JPH07108583A - Polyester sheet excellent in heat sealability and molded product thereof - Google Patents

Abstract

PURPOSE:To provide a polyester sheet having excellent heat sealability, impact resistance and transparency. CONSTITUTION:A multilayered polyester sheet is obtained by the coextrusion of aromatic polyester and a copolyester with crystal melting heat of 8cal/g or less, a shear rate of 100S<-1> and melt viscosity of 1200 poise or more.

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 product, and more particularly to a polyester molded product which maintains transparency and impact resistance and has improved heat sealability.

[0002]

2. Description of the Related Art Polyesters, particularly crystalline polyester resins represented by polyethylene terephthalate (hereinafter referred to as PET) are widely used as polymers for sheets and films including fibers, but they have excellent chemical resistance and low resistance. Taking advantage of gas permeability, it has come to be applied to carbonated drinks, juice, bottles for beverages such as beer, cosmetic containers, and food trays. Among them, molded products obtained by thermoforming a sheet made of PET are widely used for containers for foods, foods and the like.

However, a thermoformed product made of a PET sheet has poor heat-sealing property, and it is low in pressure molding (90 ° C.).
It can be heat-sealed only with a product molded at the preheating temperature of (near). Especially, vacuum molded products cannot be completely heat-sealed.

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

However, in the method of improving by laminating the copolyester on the PET sheet, a sheet forming step and a laminating step are required. Also, when the copolyester is simply formed into a single layer sheet, the impact resistance is poor.

[0006]

DISCLOSURE OF THE INVENTION The present inventors have completed the present invention as a result of extensive studies to solve the above-mentioned conventional problems, and the purpose thereof is excellent. Another object is to provide a polyester sheet having heat sealability, impact resistance, and transparency.

[0007]

[Means for Solving the Problems] The above-mentioned objects are the aromatic polyester and 280 when the heat of fusion of crystal is 8 cal / g or less.
Melt viscosity at ℃, shear rate 100s ^-1 is 1200
It is achieved by a multilayer polyester sheet characterized by being coextruded with a poise or higher copolyester.

The copolyester having the heat-sealing property which is the first requirement constituting the present invention means that part of the terephthalic acid component is isophthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, diphenyldicarboxylic acid, It may be used by substituting it with one or more other dicarboxylic acid components such as diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, sebacic acid and the like, but isophthalic acid and 2,6-naphthalenedicarboxylic acid are particularly preferable. Copolymerization in which a portion of the ethylene glycol component is replaced with one or more other glycol components such as diethylene glycol, hexamethylene glycol, trimethylene glycol, propylene glycol, neopentyl glycol, butylene glycol, 1,4-cyclohexanedimethanol, etc. Polyesters may also be used, but 1,4-cyclohexanedimethanol is particularly preferred.

The copolyester used in the present invention has a heat of crystal fusion of 8 cal / g or less and a melt viscosity of 1200 poise or more at 280 ° C. and a shear rate of 100 s ^-1 . Those whose heat of crystal fusion exceeds 8 cal / g are
At the time of thermoforming, especially at the time of vacuum forming, the surface is crystallized to deteriorate the heat sealability. The melt viscosity at 280 ° C is 12
If the porosity is less than 00 poise, the difference in melt viscosity between the co-extruded sheet and the adjacent layer becomes large and flow marks are generated, so that a clean sheet cannot be obtained.

When isophthalic acid is used as a part of the acid component of the copolymerized polyester, a copolymerized product of 8 to 15 mol% with respect to ethylene terephthalate 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 copolyester, it is 5 to 35 mol% with respect to ethylene terephthalate.
A copolymerized product is preferable in terms of heat sealability and viscosity increase.

Some of the acid component of the copolyester is 2,
When 6-naphthalenedicarboxylic acid is used, a copolymer of 5 to 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 means not only polyethylene terephthalate and polyethylene naphthalate but also a part of the terephthalic acid component is isophthalic acid within a range that does not change the properties thereof. Substituting one or more other dicarboxylic acid components such as adipic acid, diphenyldicarboxylic acid, diphenyletherdicarboxylic acid, diphenylsulfonedicarboxylic acid, sebacic acid, naphthalenedicarboxylic acid, etc., and replacing a part of the ethylene glycol component with diethylene glycol, hexamethylene glycol , Trimethylene glycol, propylene glycol, 1,4-cyclohexanedimethanol, neopentyl glycol, butylene glycol, etc., may be substituted with one or more other glycol components.
The intrinsic viscosity of polyester is 60 at a weight ratio at 20 ° C.
/ 40 in a phenol / tetrachloroethane mixed solvent, 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. Is.

In the resin composition of the present invention, additives, antistatic agents, ultraviolet absorbers, stabilizers, carbon black, talc, mica, titanium dioxide, carbonic acid are added within a range that does not change the essential properties of the polymer. Inorganic particles and pigments such as calcium, alumina, silica, wollastonite and kaolin may be contained.

The thickness of the multilayer polyester sheet of the present invention is preferably 0.15 to 1 mm, from the viewpoints of container rigidity and industrial productivity. The container obtained by processing this sheet has a slightly different thickness depending on the location, but normally, except for the stretched portion, it does not 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 copolyester is preferable from the viewpoint of container strength and heat sealability.

Next, the resin composition is melt-extruded by an extruder and then rapidly cooled, and an amorphous sheet having a crystallinity of 3% or less and having the above-mentioned thickness is produced without stretching, and is produced in a container. As the molding means, vacuum molding, pressure molding, snapback molding, lever draw molding, air slip molding, plug assist molding, hot plate molding or a molding method combining these is known as a conventional method. Then, either method can be used.

Further, the molded product has a drawing ratio (depth with respect to the frontage).
A container body having a volume of 0.1 to 1.5 is preferable in terms of securing volume and moldability.

[0019]

EFFECTS OF THE INVENTION The molded product of the present invention has a heat of crystal fusion having a heat sealability of 8 ca on the surface on the heat sealability required side.
Melt viscosity at 280 ° C is 1200 pois at 1 / g or less
Since the copolyester of e or more is co-extruded with the aromatic polyester and used, it has excellent heat sealability, printability, gas permeability, and mechanical properties, and also has little adsorption of flavor components, Most suitable for food containers, chemical containers, etc. Further, since the heat-sealing property of the vacuum-formed product is particularly excellent, it can be applied to a wide range of thermoforming machines.

[0020]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

Examples 1 to 4 and Comparative Examples 1 to 2 The PET pellets shown in Table 1 were dried to a water content of 0.01% or less, and a 0.5 mm-thick film was formed with a multi-layer extruder equipped with a T-die. A sheet was obtained, and the length was 157 mm by a vacuum thermoforming machine equipped with a female mold whose temperature was controlled at 45 ° C.
× width 110 mm × depth 34 mm (maximum drawing ratio 0.31)
The container was prepared and the following items were tested. The results are shown in Table 1.

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 and a pressure of 2.5 kg / cm ² to measure the peel strength. The peel width of the sample is 15 mm. (Target value 1000 g / 15 mm or more) 1. Impact strength: The impact strength of the sheet was measured by Toyo Seiki Co., Ltd. Graphic Impact Tester. Sheet thickness 5
It is preferable that the crack initiation energy is 3.5 to 4 J at 00 microns. 3. Low temperature impact strength; 200 g of water was placed in a container, and the container heat-sealed under the above conditions was left at -30 ° C for 24 hours,
Drop it on the concrete floor with the side of the container down and
Measure the height at 0% destruction, x less than 60 cm, 60 to 1
00 cm was evaluated as Δ and 100 cm or more was evaluated as ◯. 4. Sheet film-forming property: Judgment was visually performed at the time of sheet film formation. ○ if the film was formed cleanly, and × if a flow mark etc. appeared.

[0023]

[Table 1]

CHDM; cyclohexanedimethanol NDCA; naphthalenedicarboxylic acid

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Claims (7)

[Claims] 1. An aromatic polyester having a heat of fusion of crystal of 8
A multilayer polyester sheet characterized by being coextruded with a copolyester having a melt viscosity of 1200 poise or more at 280 ° C. at a cal / g or less and a shear rate of 100 s ⁻¹ . 2. A molded product comprising the multilayer polyester sheet according to claim 1. 3. The molded article according to claim 2, wherein the copolyester is obtained by copolymerizing isophthalic acid with ethylene terephthalate in an amount of 8 to 15 mol%. 4. The copolymerized polyester comprises 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 a copolymer. 5. The molded article according to claim 2, wherein the molded article is a main body of a container. 6. The molded product according to claim 2, wherein the thickness of the aromatic polyester is 4 to 30 times the thickness of the copolyester. 7. The drawing ratio is 0.1 to 1.5.
Molded product described.