JPH09328603A - Polyester-based sheet and its molding product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a heat-resisting polyester-based sheet suitable for a molding product for a package requiring heat resistance and impact resistance and excellent in moldability of a vessel. SOLUTION: This polyester-based sheet comprises 92-98wt.% polyethylene terephthalate having >=0.70dl/g intrinsic viscosity and 2-8wt.% high-density polyethylene having <=2g/10min melt flow rate measured by a method of ASTM D1238, and has 2-8% heat shrinkage measured by a method of JIS K6734. A molding product molded from the polyester-based sheet has 10-40% crystallinity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester sheet, and more specifically, it is a polyester suitable for container moldings such as trays, which are excellent in moldability of containers and are required to have properties such as heat resistance and impact resistance. Regarding system sheets.

[0002]

2. Description of the Related Art Food trays that can withstand use at high temperatures due to the widespread use of microwave ovens and ovens for home use, especially trays for frozen foods, not only can withstand use at high temperatures, but also freezers. It must be able to withstand temperatures and, in practice, must be able to withstand use in a wide temperature range from about -20 to about 180 ° C or higher. Further, when thermoforming or heat setting a sheet molded product, there are problems such as sagging of the sheet during preheating, moldability such as mold release and molding cycle. At present, crystallized PET (hereinafter referred to as C-PET) has been put to practical use as a heat-resistant food tray.

However, even such C-PET has a drawback that the impact resistance at low temperature is not sufficient and the container is partially damaged when an impact is applied during movement at freezing temperature. Further, due to changes in lifestyles, frozen and heated foods are more and more demanded, and at present, there is a strong demand for heat resistant containers having impact resistance.

As a method for improving such drawbacks,
A patent (Japanese Patent Application Laid-Open No. 4-345656) consisting of polyethylene terephthalate and a polyethylene ionomer has been filed. However, in such an article, it cannot be said that sufficient impact resistance is obtained, and there is a drawback that it has an offensive odor during heating and heat setting and that it is discolored. Due to such drawbacks, it has not been put to practical use.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a polyester sheet suitable for a tray container which is required to have heat resistance, impact resistance, moldability and heat resistance and impact resistance. It is in.

[0006]

The present invention has arrived at the present invention by paying attention to such problems, that is, the present invention is based on polyethylene terephthalate having an intrinsic viscosity of 0.70 dl / g or more and ASTM method D1238. 2g / measured
A polyester sheet containing high density polyethylene having a melt flow rate of 10 minutes or less at a ratio of polyethylene terephthalate / high density polyethylene = 92/8 to 98/2 (weight ratio), according to JIS method K6734. It is a polyester sheet having a heat shrinkage of 2 to 8% as measured and excellent in moldability.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Polyethylene terephthalate (hereinafter referred to as PET) according to the present invention has an intrinsic viscosity (mechanical strength of a molded product and an inherent viscosity (in order to prevent operational failure due to sagging of a sheet during a sheet preheating step during container molding). Below I
V) is 0.70 or more, preferably 0.80 or more.

High-density polyethylene (hereinafter referred to as PE) has a melt flow rate (hereinafter referred to as MFR) of 2 because of the effect of PE on impact resistance and dispersibility with PET.
g / 10 minutes or less, preferably 1 g / 10 minutes or less,
Moreover, the ratio of PE to the total weight of PET and PE is 2 to 8% by weight, preferably 3 to 6% by weight, and 2
If it is less than wt%, the effect on impact resistance will be significantly reduced,
If it is more than 8% by weight, a peculiar odor of PE is generated and it cannot be used in a food container.

The heat shrinkage is 2 to 8%, preferably 3
If it is less than 2%, dripping of the sheet will occur in the sheet preheating step during container molding and the operability will be markedly deteriorated. The shape cannot be obtained.

The crystallinity of the molded product obtained from the polyester sheet of the present invention is 10 to 40%, preferably 20 to 35%. If it is less than 10%, sufficient heat resistance as a container can be obtained. If it is more than 40%, it will be in an over-crystallized state and the impact resistance will be significantly reduced.

PET in the present invention means that it contains 80% by weight or more of ethylene terephthalate units,
Homopolymer is a theory of glutinous terephthalic acid 2,
6-naphthalenedicarboxylic acid, isophthalic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, hydroxybenzoic acid, diphenyldicarboxylic acid, diphenyletherdicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid, 3,5-dicarboxybenzenesulfone It may be replaced with one or more of acids, oxalic acid, succinic acid, glutaric acid, sebacic acid and the like and ester-forming derivatives thereof.

Further, a part of ethylene glycol is used in a small amount of cyclohexanedimethanol, 1,2-propylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, neopentylene glycol, 1,4-bis (ethylene glycol). It may be replaced with one or more of hydroxybenzene and polyalkylene glycols such as polyethylene glycol, polytetramethylene glycol and polypropylene glycol. Further, trifunctional or higher functional compounds such as glycerin, pentaerythritol, trimellitic acid and 5-hydroxyisophthalic acid may be used to a certain extent so that the polymer is substantially linear, and monofunctional compounds,
For example, p-phenylphenol, benzyloxybenzoic acid, naphthalene monocarboxylic acid, polyethylene glycol monomethylene ether, etc. may be substituted.

If necessary, a small amount of other polymers or additives may be mixed in the polyester sheet of the present invention, but in this case, the properties of the polyester sheet are not essentially changed. It is preferable to do so. Examples of these polymers or additives include polyamides, polyolefins other than PE, other polyesters, etc., matting agents such as titanium dioxide and alumina oxide, stabilizers such as phosphoric acid, phosphorous acid and their esters, and antioxidants. Agents, antibacterial agents, ultraviolet absorbers, fluorescent whitening agents or pigments, dyes and the like.

[0014]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. The main methods for measuring physical properties are as follows. (A) Intrinsic viscosity (IV) It was measured at a temperature of 30 ° C. in a mixed solvent of phenol / tetrachloroethane = 60/40 (weight ratio).

(B) Melt flow rate (MFR)
(G / min) Measured by ASTM method D1238.

(C) Impact strength Using a tray container cut-out piece adjusted to an impact strength of -10 ° C., a weight of 76 g is 50 cm in height using a DuPont drop weight impact test.
It was measured by the number of cracks with respect to the number of 15 tests when the weight was dropped from 100 cm.

The PET, PE and polyethylene iomers used are as follows. (A) PET resin with PET IV = 1.00 g / dl

(B) PE High density PE having an MFR of 0.40 g / 10 min and low density PE resin having an MFR of 15 (c) Polyethylene ionomer Na ion type polyethylene ionomer resin having an MFR of 0.9 g / 10 min.

Examples 1 and 2 and Comparative Example 1 Using each of the above-mentioned resins, a home-made sheeting machine was used.
A sheet molded product having a thickness of 5 mm was obtained. Next, using this sheet, a tray container having a full capacity of 320 cc was obtained with a vacuum pressure air molding machine TVP-33 manufactured by Sanwa Kogyo Co., Ltd. All barrel temperature conditions during sheet molding are set to 290 ° C, all sheet preheating conditions during container molding are set to 90% heater output, mold temperature conditions during container molding are all set to 180 ° C, heating time during container molding. Were all set for 10.5 seconds. Table 1 shows the evaluation results of the heat resistance by observing the appearance of discoloration and deformation after leaving the container in a gear oven set at 220 ° C. for 15 minutes.

[0020]

[Table 1]

As is clear from "Table 1", the heat-resistant polyester molded product of the present invention exhibits excellent heat resistance. Examples 3 and 4 and Comparative Example 2 Each of the above resins was used to prepare 0.1% by a homemade sheeting machine.
A sheet molded product having a thickness of 5 mm was obtained. Next, using this sheet, a tray container having a full capacity of 320 cc was obtained using a vacuum pressure air molding machine TVP-33 manufactured by Sanwa Kogyo Co., Ltd. All barrel temperature conditions during sheet molding were set at 290 ° C, and all sheet preheating conditions during container molding were set at 90% heater output.
The mold temperature conditions during container molding were all set to 180 ° C., and the heating time during container molding was set to 10.5 seconds. Furthermore,
This container was subjected to a heat treatment for 30 minutes in a gear oven set at 150 ° C., assuming that the contents were actually put into the container and oven treatment was performed. Table 2 shows the evaluation results of the impact strength of the container.

[0022]

[Table 2]

As is clear from "Table 2", the heat-resistant polyester molded product of the present invention exhibits excellent impact resistance.

[0024]

The polyester sheet of the present invention has a high I
Impact resistance of PET of V and high density PE itself In particular, good dispersibility of high density PE in high IV PET is added, and impact resistance of the tray container is improved even when heated and heat set. . Further, by using the sheet having the above-described composition having a heat shrinkage rate of 2 to 8%, the sagging property of the sheet at the time of heating during heating and heat setting and the moldability at the time of heat setting are improved, and the molding cycle is shortened and Wrinkles and uneven thickness of the container are eliminated, and the container moldability is improved. In addition, by crystallizing the crystallinity to 10 to 40%, heat resistance that makes it possible to use a microwave oven or an oven can be obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Fujio Hirasawa 2-2-8 Dojimahama, Kita-ku, Osaka Toyobo Co., Ltd.

Claims (2)

[Claims] 1. Polyethylene terephthalate / high density polyethylene = 92/8 to polyethylene terephthalate having an intrinsic viscosity of 0.70 dl / g or more and high density polyethylene having a melt flow rate of 2 g / 10 minutes or less as measured by ASTM method D1238. It is a polyester sheet containing 98/2 (weight ratio), and the heat shrinkage rate of the sheet is 2 to 8% as measured by JIS method K6734.
Is a polyester sheet. 2. A molded product molded from the polyester sheet according to claim 1 and having a crystallinity of 10 to 40%.