JPH11105220A - Polyester-based multilayered sheet and low temperature impact resistant and heat resistant polyester-based multilayered formed piece using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester-based multilayered sheet, which is excellent in container formability and can form a low temperature impact resistant and high heat resistant container-formed piece, and its formed piece. SOLUTION: This multilayered sheet has a surface layer consisting of 92-99 wt.% of polyester resin, which is obtained by polycondensing a dicarboxylic acid component mainly made of terephthalic acid and 1,4-cyclohexanedimethanol. and has an intrinsic viscosity of 0.60 dl/g of higher, and 1-8 wt.% of polyolefin resin and a basic layer consisting of 60-97 wt.% of resin, which is mainly made of polyethylene terephthalate having the intrinsic viscosity of 0.60 dl/g or higher, 1-10 wt.% of polyolefin resin, 2-30 wt.% of polyester-based elastomer resin and 1 wt.% or below of modified polyolefin resin. Then, by employing a polyester-based multilayered sheet and the sheet just mentioned above, the resultant sheet is heat-formed so as to realize its degree of crystallization of 10-40% and finally heat-set.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester multi-layer sheet having improved low-temperature impact resistance and heat resistance and excellent moldability of a container, and a molded article heat-set and heat-set with the multi-layer sheet, particularly a container. Related to molded products.

[0002]

BACKGROUND OF THE INVENTION 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 temperature. In particular, the container itself may be exposed to temperatures exceeding 220 ° C. during food cooking and filling and oven processing,
It must be able to withstand use in a wide temperature range from about −20 to about 240 ° C. or more. In addition, thermoforming sheet molded products,
When performing heat setting, there are also problems with moldability such as sagging of the sheet during preheating, mold release from the mold, and molding cycle. At present, as heat-resistant food trays, crystallized PET (hereinafter referred to as C-PET) from Toyobo and THERMX with a nucleating agent added from Eastman are in practical use.

[0003] However, such C-PET also has the 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. Further, at a temperature exceeding 240 ° C., there is a disadvantage that discoloration and deformation occur. Also, THERMX added with a nucleating agent from Eastman has a disadvantage that productivity is low due to a long container molding cycle, and further, it is colored brown. In recent years, there has been an active demand for the development of various types of frozen and heated foods in line with changes in lifestyles, and there has been a long-awaited demand for high-temperature heat-resistant containers that have excellent container moldability and low-temperature impact resistance. .

[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 and / or a metal salt of a fatty acid. However, in such articles, it cannot be said that impact resistance at low temperatures and heat resistance at high temperatures have been obtained.
In addition, productivity is low due to poor container moldability, and it has not been put to practical use.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polyester-based multilayer sheet having excellent impact resistance at a low temperature and heat resistance at a high temperature and excellent in moldability of a container, and a thermoformed and heat-set sheet. Another object of the present invention is to provide a low-temperature impact-resistant and heat-resistant molded product, particularly a container molded product.

[0006]

Means for Solving the Problems The present invention is as follows. (1) 92 to 99% by weight of a polyester resin having an intrinsic viscosity of 0.60 dl / g or more and a polyolefin resin of 1 to 8 obtained by condensation polymerization of a dicarboxylic acid component containing terephthalic acid as a main component and 1,4-cyclohexanedimethanol. weight%
And a resin 60-97 containing polyethylene terephthalate having an intrinsic viscosity of 0.60 dl / g or more as a main component.
A polyester-based multi-layer sheet comprising: a base layer comprising 1% 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. (2) Using the polyester-based multilayer sheet of (1) above,
It is a heat-set, low-temperature impact-resistant, heat-resistant polyester-based multilayer molded product that is thermoformed so as to have a crystallinity of 10 to 40%.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester resin obtained by polycondensing a dicarboxylic acid component containing terephthalic acid as the main component and 1,4-cyclohexanedimethanol in the surface layer of the present invention is advantageous in terms of melt extrudability and the obtained sheet. From the viewpoint of the mechanical strength of the thermoformed and heat-set molded article, and the ability to preheat the sheet at the time of container molding, its intrinsic viscosity (hereinafter referred to as IV) is 0.60 dl / g or more; It is preferably at least 0.70 dl / g, and the upper limit of IV is usually at most 1.20 dl / g, preferably at most 1.00 dl / g.

In the polyester resin of the present invention, a part of terephthalic acid is used, for example, 2,6-naphthalenedicarboxylic acid, isophthalic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, hydroxybenzoic acid, diphenyldicarboxylic acid, diphenyletherdicarboxylic acid. , Diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid, 3,5-dicarboxybenzenesulfonic acid, oxalic acid, succinic acid, glutaric acid, sebacic acid, etc. Good.

Further, a part of 1,4-cyclohexanedimethanolethylene glycol is used, for example, in a small amount, such as ethylene glycol, 1,2-propylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, and neopentene. It may be replaced with one or more of lenglycol, 1,4-bishydroxybenzene and polyalkylene glycol such as polyethylene glycol, polytetramethylene glycol and polypropylene glycol. 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. , Benzyloxybenzoic acid, naphthalene monocarboxylic acid, polyethylene glycol monomethylene ether and the like.

The proportion of a resin obtained by polycondensing a dicarboxylic acid component mainly composed of terephthalic acid and 1,4-cyclohexanedimethanol in the surface layer is 92 to 99% by weight.
Preferably, it is 94 to 98% by weight.

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, from the viewpoint of functioning as a crystallization nucleating agent during thermoforming.
If the amount is more than 8% by weight, an odor peculiar to the olefin resin is generated. In particular, the olefin resin cannot be used for food, and if the amount is less than 1% by weight, the effect of the polyolefin resin as a crystallization nucleating agent cannot be utilized.

Examples of the polyolefin resin in the present invention include a polypropylene resin, a polystyrene resin, and a polyethylene resin (hereinafter, referred to as PE) which can serve as a crystal nucleating agent, and PE is preferable. In consideration of the dispersibility of the polymer, high-density PE is preferable.

In the present invention, the resin containing polyethylene terephthalate as the main component of the base layer is advantageous in terms of melt extrudability, mechanical strength of the obtained sheet and the thermoformed and heat-set molded article, and the properties at the time of container molding. From the viewpoint that the sheet can be preheated, its intrinsic viscosity (hereinafter referred to as IV) is 0.6.
It is 0 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.

The resin containing polyethylene terephthalate as a main component in the present invention means homo PET and a part of terephthalic acid, for example, 2,6-naphthalenedicarboxylic acid, isophthalic acid, hexahydroterephthalic acid,
Hexahydroisophthalic acid, hydroxybenzoic acid, diphenyldicarboxylic acid, diphenyletherdicarboxylic acid, diphenylsulfondicarboxylic acid, diphenoxyethanedicarboxylic acid, 3,5-dicarboxybenzenesulfonic acid, oxalic acid, succinic acid, glutaric acid, sebacic acid, etc. And copolymerized PET substituted with one or more of these ester-forming derivatives.

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

The proportion of the resin containing polyethylene terephthalate as a main component is 60 to 97% by weight, preferably,
If it is 71 to 88% by weight, and if it is more than 97% by weight, the effect of low-temperature impact properties of the polyester-based elastomer having a low glass transition temperature cannot be utilized, and if it is less than 60% by weight, the mechanical strength characteristics of PET will be poor. It cannot be used.

The polyolefin resin used in the present invention is used in an amount of 1 to 10% by weight, preferably 2 to 6% by weight, in view of the action as a crystallization nucleating agent during thermoforming. If the amount is too large, the peculiar odor of the polyolefin resin extends to the surface, and particularly it cannot be used for foods. If the amount is less than 1% by weight, the effect of the polyolefin resin as a crystallization nucleating agent cannot be utilized.

Examples of the polyolefin resin include a polypropylene resin, a polystyrene resin, and a polyethylene resin (hereinafter, referred to as PE) which can serve as a crystal nucleating agent.
PE is preferable, and among them, high-density PE is preferable in consideration of impact resistance and dispersibility in a base polymer.

Regarding the polyester elastomer resin of the present invention, the effect on the impact resistance at low temperatures, the sagging of the sheet at the time of preheating when thermoforming and heat setting the sheet molded product, and the preheating time, that is, container molding From the viewpoint of cycle time and mold releasability, the usage ratio is 2 to 30% by weight, preferably 5 to 20% by weight, and if more than 30% by weight, the modulus of elasticity of the sheet when heated is reduced. If the content is less than 2% by weight, the effect on the moldability due to the decrease in the elastic modulus is not exhibited, and the effect on the impact resistance at a low temperature may be utilized. Not done.

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 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. Considering 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 without any compatibility with PET. It is difficult to take advantage of the impact resistance at the time. In order to take full advantage of the low-temperature impact resistance of this polyolefin resin, it is preferable to mix a small amount of a modified polyolefin that has excellent compatibility with the polyolefin resin and is also compatible with PET. From the viewpoint of the effective action of the compound, its use ratio is less than 1% by weight, and if it is 1.0% by weight or more, it is excessive as a compatibilizing agent and causes the generation of black carbide due to thermal deterioration during melt mixing. In the case of a molded product of a container, black spots are stained, and in particular, a food container is extremely inferior in appearance.

Examples of the modified polyolefin resin in the present invention include ethylene-maleic anhydride-acrylic ester copolymer, ethylene-maleic anhydride grafted product, butadiene-alkyl acrylate-alkyl methacrylate copolymer and the like. Preferred are an ethylene-maleic anhydride-acrylic acid ester copolymer and an ethylene-maleic anhydride graft, which have excellent compatibility with PE and are easily compatible with PET.

The polyester-based multi-layer sheet of the present invention may contain a small amount of other polymers or additives, if necessary. In such a case, the properties of the polyester-based sheet do not substantially change. It is preferable to carry out the above. Examples of these polymers or additives include polyamides, polyolefins other than PE, other polyesters, etc., matting agents such as titanium dioxide and alumina oxide, inorganic fillers such as talc, phosphoric acid, phosphorous acid and esters thereof. And antioxidants, antibacterial agents, ultraviolet absorbers, fluorescent brighteners, pigments, dyes, and the like.

Extrusion of the polyester-based multilayer sheet of the present invention can be carried out by known means. For example,
The resin composition constituting the surface layer and the base layer can be produced using a general multilayer sheet molding machine having two extruders and a multilayer die.

The layers constituting the polyester-based multi-layer sheet and the molded article of the present invention are as follows: when the sheet is formed into a container or a package, the outer layer is a surface layer, and the inner layer is a base layer. Thereby, the layer in contact with the contents inside the base layer is formed as a surface layer, and can be shown as a surface layer / base layer or a configuration of surface layer / base layer / surface layer. The thickness / thickness ratio can be arbitrarily set depending on the application and the like. For example, the surface layer (when there are two layers, the total thereof) is
The base layer has a thickness of 80 to 800 μm, and the thickness ratio of the base layer can be expressed as follows: surface layer (when there are two layers, the sum thereof): base layer = 2: 8 to 6: 4.

The molded article of the present invention can be molded by known means. For example, a commonly used vacuum forming method and plug assist forming method can be employed.

[0027]

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 measured as a solvent at a temperature of 30 ° C. (2) Impact resistance test method A cut piece of a tray container adjusted to -10 ° C was weighed to a height of 20 g using a DuPont type falling weight impact test.
The number of cracks with respect to the test number of 15 when the weight was dropped from cm, 25 cm, 30 cm, and 35 cm was determined.

The PET, polyolefin resin, polyester elastomer resin and modified polyolefin resin used are as follows. (1) Resin obtained by polycondensation of a dicarboxylic acid component containing terephthalic acid as a main component and 1,4-cyclohexanedimethanol In an autoclave, dimethyl terephthalate and 1,4
-An initial condensate is produced by a transesterification method in which a transesterification reaction with cyclohexanedimethanol is carried out in the presence of a catalyst, and this initial condensate is polycondensed by a polycondensation method to obtain
A polyester resin having V = 0.75 dl / g (hereinafter referred to as Es resin) was obtained. (2) PET resin RP560 manufactured by Toyobo Co., Ltd. (IV = 1.00 g / dl) (3) Polyolefin resin High-density PE resin manufactured by Mitsui Petrochemical Industries (Hi-Zex) (4) Polyester elastomer Perprene manufactured by Toyobo Co., Ltd. Resin (5) Modified polyolefin resin Ethylene-maleic anhydride-acrylate copolymer (Rexpearl) manufactured by Japan Polyolefin Co., Ltd. (6) Polyethylene ionomer Na-type polyethylene ionomer resin manufactured by Dupont (Surlyn)

[Examples 1, 2 and Comparative Examples 1, 2, 3] 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 set at 315 ° C. for the surface layer and 290 ° C. for the base layer in Examples, and in Comparative Examples 1 and 2,
The base layer side was set at 290 ° C., and in Comparative Example 3, the surface layer side and the base layer side were set at 315 ° C. Then, the sheet preheating conditions during container molding were all set to a heater output of 90%, and the mold temperature conditions during container molding were all 180 ° C setting, heating time for container molding is 4
The test was performed at a pitch of 2 seconds from 18 seconds to 18 seconds. "Table 1" shows the results of evaluation of the state of the container molding.

[0030]

[Table 1]

With the polyester-based multilayer molded article of the present invention, a good container molded article without sheet sagging can be obtained with a sheet preheating time of 6 to 8 seconds. In Comparative Examples 1 and 2, the sheet preheating time is 6 to 8 seconds. Then, without releasing from the heat set mold,
At 16 seconds, the sheet drooped significantly, so that only a container with wrinkles was obtained. In Comparative Example 2, the sheet was not softened during the sheet preheating time of 6 seconds to 8 seconds, and the container was poorly determined and had a satisfactory shape.
As is clear from Table 1, the polyester-based multilayer molded article has a short cycle time and shows excellent container moldability.

[Examples 3 and 4 and Comparative Examples 4 and 5] Using the container molded products of Examples 1 and 2 and Comparative Examples 1 and 2, the case where the container was actually filled with contents and oven-treated was performed. Table 2 shows the evaluation results of the heat resistance by observing the appearance of the container when heat treatment was performed for 4 minutes in a gear oven set at 250 ° C. assuming.

[0033]

[Table 2]

[Examples 5 and 6 and Comparative Examples 6 and 7] Using the container molded products of Examples 1 and 2 and Comparative Examples 1 and 2, the case where the container was actually filled with contents and oven-treated was performed. Assuming, heat treatment was performed for 4 minutes in a gear oven set at 250 ° C. Table 3 shows the evaluation results of the impact strength of the container.

[0035]

[Table 3]

As is clear from Table 3, the polyester-based multilayer molded article shows excellent impact resistance at low temperatures.

[0037]

The polyester-based multilayer sheet according to the present invention is a polyester-based multilayer molded article having excellent container moldability, low-temperature impact resistance and high heat resistance.

Claims (2)

[Claims] 1. A polyester resin having an intrinsic viscosity of 0.60 dl / g or more obtained by condensation polymerization of a dicarboxylic acid component containing terephthalic acid as a main component and 1,4-cyclohexanedimethanol, and 92 to 99% by weight of a polyolefin resin. ~
A surface layer composed of 8% by weight, and a resin 6 containing polyethylene terephthalate as a main component having an intrinsic viscosity of 0.60 dl / g or more.
0 to 97% by weight, 1 to 10% by weight of polyolefin resin,
A base layer comprising 2 to 30% by weight of a polyester elastomer resin and less than 1% by weight of a modified polyolefin resin. 2. A polyester multilayer molded article which is thermoformed using the polyester multilayer sheet according to claim 1 so as to have a crystallinity of 10 to 40%, and is heat-set at low temperature impact resistance and heat resistance. .