JPH11106625A - Polyester-based sheet and polyester-based molded article having impact resistance at low temperature and heat resistance by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a polyester-based sheet having excellent vessel moldability and moldable a vessel having impact resistance at a low temperature and heat resistance, and a molded material of the sheet. SOLUTION: This polyester-based sheet comprises 62-97 wt.% of a polyethylene terephthalate-based resin having >=0.60 dl/g inherent viscosity, 1-8 wt.% of a polyolefin resin, 2-30 wt.% of a polyester-based elastomer resin and <1 wt.% of a modified polyolefin resin. The polyester-based molded article is obtained from the polyester-based sheet by heat-molding and subjecting to heat- setting so as to have 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 heat-resistant polyester sheet which is excellent in moldability of a container and a molded article excellent in low-temperature impact resistance which is thermoformed using the sheet and heat-set. About goods.

[0002]

2. Description of the Related Art Due to the widespread use of microwave ovens and ovens for home use, food trays that can withstand use at high temperatures, in particular,
As a tray for frozen foods, it is necessary to be able to withstand not only high temperatures but also freezer temperature, and in practical use, it can be used in a wide temperature range from about -20 to about 180 ° C or more. You need to be able to endure. In addition, when thermoforming and heat setting a sheet molded product, there are problems in formability such as sagging of the sheet at the time of preheating, release from a mold and a molding cycle. At present, crystallized PET (hereinafter referred to as C-PET) has been put to practical use as a heat-resistant food tray.

[0003] However, such C-PET also has a disadvantage that the impact resistance is not sufficient and the container is partially damaged when an impact is applied during movement at a low temperature. In addition, when heat setting, the preheating step of the sheet is a point, and there is a drawback in container molding that generation of wrinkles in the container due to sheet sagging and a long molding cycle. Due to recent changes in lifestyles, frozen and heated foods are increasingly required, and there is a need for a heat-resistant container having low-temperature impact resistance and excellent container moldability.

[0004] As a method for improving such disadvantages,
Polyethylene terephthalate resin (hereinafter referred to as PET)
Japanese Patent Application Laid-Open No. 4-34, comprising polyethylene and a polyethylene ionomer
No. 5,656, JP-A No. 1-272659 comprising PET and a modified polyolefin resin, and JP-A-2-255557 comprising PET and a modified polyolefin resin and a fatty acid diester or a fatty acid metal salt. However, such articles cannot be said to have obtained impact resistance at low temperatures and have not been put to practical use.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-resistant polyester-based sheet excellent in container moldability and a molded article excellent in low-temperature impact resistance which is thermoformed using the sheet and heat-set. And container molded articles.

[0006]

Means for Solving the Problems The present invention is as follows. (1) 62 to 97% by weight of a polyethylene terephthalate resin having an intrinsic viscosity of 0.60 dl / g or more, 1 to 8% by weight of a polyolefin resin, 2 to 30% by weight of a polyester elastomer resin, and 1% by weight of a modified polyolefin resin
A polyester sheet comprising: (2) A heat-set, low-temperature, impact-resistant, heat-resistant polyester-based molded article which is formed using the polyester-based sheet of (1) above and has a crystallinity of 10 to 40%.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The polyethylene terephthalate resin of the present invention is characterized by its melt extrudability into a sheet, the obtained sheet and the mechanical strength of a thermoformed and heat-set molded article, and the molding of a container. From the point that the sheet can be preheated at the time, its intrinsic viscosity (hereinafter referred to as IV) is 0.
It is 60 dl / g or more, preferably 0.70 dl / g or more, and the upper limit of IV is usually 1.30 dl / g or less, preferably 1.00 dl / g or less.

[0008] The polyethylene terephthalate resin in the present invention is based on homo PET,
In addition to ET, part of terephthalic acid, for example, 2,6-naphthalenedicarboxylic acid, isophthalic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, hydroxybenzoic acid, diphenyldicarboxylic acid, diphenyletherdicarboxylic acid, diphenylsulfondicarboxylic acid, Diphenoxyethane dicarboxylic acid, 3,5-dicarboxybenzenesulfonic acid, oxalic acid, succinic acid, glutaric acid,
It may be a copolymerized PET substituted with one or more of sebacic acid and the like and their ester-forming derivatives.

Further, a part of ethylene glycol may be replaced with a small amount of, for example, cyclohexanedimethanol, 1,2-propylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, neopentylene glycol,
Copolymerized PET substituted with one or two or more of 4-bishydroxybenzene and polyalkylene glycol such as polyethylene glycol, polytetramethylene glycol, and polypropylene glycol may be used.
Further, a trifunctional or more functional compound such as glycerin, pentaerythritol, trimellitic acid, or 5-hydroxyisophthalic acid may be used in a substantially linear polymer, and a monofunctional compound such as p-phenylphenol may be used. And benzyloxybenzoic acid, naphthalene monocarboxylic acid, polyethylene glycol monomethylene ether and the like.

The use ratio of the polyethylene terephthalate resin is from 62 to 97% by weight, preferably from 71 to 91% by weight, and if it is more than 97% by weight, the effect on the container moldability of the polyester elastomer having a low glass transition temperature, The effect on impact resistance at low temperatures was not exploited, and 61
If the amount is less than the weight percentage, the mechanical strength characteristics of PET cannot be utilized.

The polyolefin resin used in the present invention is used in an amount of 1 to 8% by weight, preferably 2 to 6% by weight, in view of the action as a crystallization nucleating agent during thermoforming.
If the amount is more than 8% by weight, a peculiar smell of the polyolefin resin is generated, and particularly, it cannot be used for food, and if it is less than 1% by weight, the effect of the polyolefin resin as a crystallization nucleating agent cannot be utilized.

As the polyolefin resin, a polypropylene resin, a polystyrene resin, a polyethylene resin, and the like, which can serve as a crystal nucleating agent, can be mentioned. A polyethylene resin is preferable, and a high-density PE is particularly preferable in consideration of impact resistance and dispersibility in PET.

The polyester elastomer resin of the present invention has an effect on impact resistance at a low temperature, sags of a sheet at the time of preheating when thermoforming and heat setting a sheet molded product, and releasing from a mold. From the viewpoints of properties and container molding cycle, the use ratio is 2 to 30% by weight, preferably 3 to 20% by weight. When the content is less than 2% by weight, the effect of shortening the container molding cycle is lost, and the effect on the low-temperature impact resistance is not utilized.

The polyester elastomer resin of the present invention is a polyester resin having a low glass transition temperature, a hard segment of polybutylene terephthalate and a soft segment of polytetramethylene glycol (hereinafter PT).
MG), a copolymerized polyester-based elastomer in which the hard segment is polybutylene terephthalate and the soft segment is lactone, the hard segment is polyethylene terephthalate and the soft segment is PTMG, and the like. In consideration of this, a copolymer polyester elastomer having a high effect on low-temperature impact resistance and having a hard segment of polyethylene terephthalate and a soft segment of PTMG is preferred.

The modified polyolefin resin of the present invention is a polyolefin resin which is a crystal nucleating agent which is melt-mixed and dispersed in PET and is present in a completely free form because it is completely incompatible with PET. It is difficult to make use of impact resistance at low temperatures. In order to make full use of the low-temperature impact resistance of this polyolefin resin, the compatibility with the polyolefin resin is excellent, and PET is used.
It is desirable to mix a small amount of a modified polyolefin that is easily compatible with water, and its use ratio is less than 1% by weight from the viewpoint of effective action on impact resistance at low temperatures, and the content is less than 1.0% by weight. It is excessive as a solubilizer and causes the generation of black carbide due to thermal deterioration during melting and mixing, resulting in black spots on container molded products, especially in the appearance of food containers,
Extremely inconvenient.

The modified polyolefin resin in the present invention includes ethylene-maleic anhydride-acrylic ester copolymer, ethylene-maleic anhydride graft, butadiene-alkyl acrylate-alkyl methacrylate copolymer, and the like. Excellent compatibility with PE and P
Ethylene-maleic anhydride-acrylate copolymers and ethylene-maleic anhydride grafts, which are easily compatible with ET, are preferred.

The polyester sheet of the present invention may contain a small amount of other polymers or additives if necessary, but in this case, the properties of the polyester sheet are not substantially changed. It is preferred to do so. As these polymers or additives, for example, polyamides, polyolefins other than PE,
Other polytesters, such as titanium dioxide, matting agents such as alumina oxide, inorganic fillers such as talc, stabilizers such as phosphoric acid, phosphorous acid and their esters, antioxidants, antibacterial agents,
Examples include ultraviolet absorbers, fluorescent whitening agents, pigments, dyes, and the like.

The polyester sheet of the present invention can be produced by a means known per se. For example, it can be manufactured using a general sheet forming machine having an extruder and a die. Further, the resin composition of the present invention may be multi-layered with C-PET as needed. For example, the resin composition constituting the surface layer and the inner layer can be manufactured using a general multilayer sheet molding machine having two extruders and a multilayer die. Further, the molded container of the present invention can also be produced by a means known per se. For example,
It can be manufactured by adopting a commonly used vacuum forming method and plug assist forming method.

[0019]

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 in the present invention are as follows.

1. Intrinsic viscosity Phenol / tetrachloroethane = 60/40 (weight ratio) was used as a solvent and measured at a temperature of 30 ° C.

Low-Temperature Impact Resistance Test A cut piece of a tray container adjusted to -10 ° C. was weighed to a height of 200 g using a DuPont type drop weight impact test to a height of 20 g.
The number of cracks for 15 test pieces when dropped from cm, 30 cm, 40 cm, and 50 cm was determined.

The used PET, PE, polyester-based elastomer, modified polyolefin and polyethylene iomer resin are as follows. (1) PET resin RP560 (IV = 1.00 g / dl) manufactured by Toyobo Co., Ltd. (2) Polyolefin resin High-density PE resin (Hi-Zex) manufactured by Mitsui Petrochemical Industry Co., Ltd. (3) Polyester elastomer resin manufactured by Toyobo Co., Ltd. Perprene resin (4) Modified polyolefin resin Ethylene-maleic anhydride graft product (Adtex) manufactured by Japan Polyolefin Co. (5) Polyethylene ionomer Na ion type polyethylene ionomer resin (Surlyn) manufactured by DuPont

[Examples 1, 2, 3 and Comparative Examples 1, 2] Using each of the above resins, a home-made sheeting machine was used for 0.5 hours.
A sheet molded product having a thickness of mm was obtained. Next, using this sheet, a tray container with a full capacity of 320 cc was obtained with a vacuum pressure air molding machine TVP-33 manufactured by Sanwa Kogyo. The barrel temperature conditions during sheet molding were all set to 290 ° C, the sheet preheating conditions during container molding were all set to 90% heater output, the mold temperature conditions during container molding were all set to 180 ° C, and the sheet preheating time was 4 hours. The test was performed with a 2-second pitch setting from seconds to 16 seconds. "Table 1" shows the results of evaluation of the state of the container molding.

[0024]

[Table 1]

The polyester-based molded article obtained was a good container molded article having a sheet preheating time of 4 seconds without sagging of the sheet. Comparative Examples 1 and 2 were separated from the heat-set mold in a sheet preheating time of 4 seconds. In 16 seconds, the sheet drooped significantly, so that only a container with wrinkles was obtained.
As apparent from "Table 1," the polyester-based sheet has a short cycle time and exhibits excellent container moldability.

[Examples 4 and 5 and Comparative Examples 3 and 4] The case where the containers were actually filled with contents and oven-treated using the container molded products of Examples 2 and 3 and Comparative Examples 1 and 2 was used. Assuming, heat treatment was performed for 5 minutes in a gear oven set at 200 ° C. Table 2 shows the evaluation results of the impact strength of the container.

[0027]

[Table 2]

As is clear from Table 2, the polyester-based molded article shows excellent impact resistance at low temperatures.

[0029]

The polyester sheet according to the present invention comprises:
A molded article formed from the sheet, which is excellent in container moldability and impact resistance, is a polyester molded article having extremely excellent low-temperature impact resistance and excellent heat resistance.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FIB29L 22:00 (72) Inventor Takayuki Kai 10-24 Toyocho, Tsuruga-shi, Fukui Toyobo Co., Ltd. Inventor Hideyuki Kaetsu 10-24 Toyo-cho, Tsuruga-shi, Fukui Toyobo Co., Ltd.

Claims (2)

[Claims] 1. From 62 to 97% by weight of a polyethylene terephthalate resin having an intrinsic viscosity of 0.60 dl / g or more, 1 to 8% by weight of a polyolefin resin, 2 to 30% by weight of a polyester elastomer resin and less than 1% by weight of a modified polyolefin resin. Polyester sheet consisting of. 2. The polyester sheet according to claim 1, which is thermoformed so as to have a crystallinity of 10 to 40%.
Heat-set low-temperature impact-resistant and heat-resistant polyester-based molded product.