JP3398579B2 - Heat-resistant transparent multilayer polyester sheet and molded product - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to heat resistance, transparency,
The present invention relates to a multilayer structure sheet having excellent impact resistance at low temperatures, and is widely used for industrial applications and food applications. In particular, in food applications, it is suitably used as a packaging container and a lid material for cooked food that is used after being heated and thawed in a microwave oven or the like.

[0002]

2. Description of the Related Art Conventionally, as a transparent sheet, polyvinyl chloride (PVC), polymethylmethacrylate, styrene copolymer resin, polyethylene terephthalate (PE
T), polycarbonate, etc. are known. These are used as various packaging containers, but each has its advantages and disadvantages, and its application field was limited.

That is, a sheet made of polyvinyl chloride has many environmental problems because an acidic gas is generated during combustion.
Polymethylmethacrylate has insufficient impact resistance,
Also, the secondary formability is poor. A sheet made of a styrene-based copolymer resin has excellent secondary workability, but has poor impact resistance and oil resistance. Polyethylene terephthalate is excellent in transparency and gas barrier property, but is insufficient in heat resistance and inferior in impact resistance at low temperature. Also,
Although a sheet made of polycarbonate is excellent in transparency, heat resistance and impact resistance, it is inferior in gas barrier property, secondary processability and economical efficiency, and most applications are limited to industrial applications.

As described above, the sheet made of the conventional material has various problems, and it has been demanded to develop a sheet which solves these problems and is excellent in transparency, heat resistance and economical efficiency and can be used in a wide variety of applications. There is.

As a transparent sheet which meets such a demand, a multilayer structure sheet made of polyethylene terephthalate and polycarbonate has already been proposed.

Japanese Unexamined Patent Publication (Kokai) No. 62-181129 describes that a polyethylene terephthalate polyester resin film is sandwiched between polycarbonate films and heat-bonded to form a laminated film into a container by thermoforming. ing. In this publication, it is stated that this container can be sterilized by boiling and retort. However, according to the inventors of the present invention, the container made of this laminated film is a polyethylene terephthalate-based polyester in an intermediate layer when sterilizing by boiling and retorting. There is a problem that the resin is crystallized and the transparency is lowered.

Further, Japanese Unexamined Patent Publication (Kokai) No. 3-82530 discloses a multi-layered sheet having a central layer made of thermoplastic polyester, polycarbonate layers on both sides thereof, and outer layers made of thermoplastic polyester on both sides thereof. ing. In the publication, this multilayer structure sheet is said to have excellent heat resistance, transparency, and secondary processability, but the inventors of the present application have found that the thermoplastic polyester used for the core layer and the outermost layer has impact resistance. Has a large temperature dependence at
There is a problem that the impact resistance at temperatures below the freezing point is poor. In addition, very large-scale equipment is required to manufacture this multilayer structure sheet, which is not practical in terms of economy.

[0008]

As described above, it is difficult to obtain a sheet which is excellent in heat resistance, transparency, impact resistance at low temperature, and is economical in terms of raw material cost and manufacturing equipment. It was However, with the recent advances in distribution systems and the widespread use of microwave ovens, as the demand for processed foods has increased, it has excellent heat resistance and transparency, and has impact resistance during transportation, especially strength at temperatures below the freezing point. There is a strong demand for plastic sheets.

The present invention has solved the above problems and provides a plastic sheet and a molded article having excellent heat resistance, transparency and impact resistance at low temperature.

[0010]

Means for Solving the Problems As a result of extensive studies conducted by the present inventor for this purpose, a resin composition prepared by blending a polyethylene terephthalate resin with a polycarbonate resin in a specific ratio was used as a base material, and a polycarbonate was provided on one or both surfaces. The present inventors have found that a heat-resistant transparent multilayer polyester sheet formed by laminating resins improves impact resistance at low temperature without impairing transparency, and has completed the present invention.

That is, the present invention provides a glycol component.
1,4-cyclohexanedimethanol component is 1-10
% Polyethylene terephthalate resin 70 copolymerized
~ 95 parts by weight and polycarbonate resin 5-30 parts by weight?
Ranaru a resin composition as a base material, its formed by laminating a polycarbonate resin on one or both sides layer heat transparent multilayer polyester sheet and formed molded article made of it.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The base material used in the present invention is a resin composition containing polyethylene terephthalate resin and a polycarbonate resin as main components, and the proportion thereof is 70 to 97 parts by weight of polyethylene terephthalate resin and 3 to 30 parts of polycarbonate resin. Parts by weight are preferred. If the compounding ratio of the polycarbonate resin is less than 3 parts by weight, the impact resistance at low temperature is lowered, which is not preferable. Further, if the compounding ratio of the polycarbonate resin exceeds 30 parts by weight, the transparency is lowered, which is not preferable. The compounding method is not particularly limited, but a method of directly charging the raw materials that are agitated and mixed into an extruder during sheet molding, and the raw materials that are agitated and mixed are melt-mixed and pelletized by a single-screw or twin-screw extruder,
Any method used at the time of sheet extrusion may be used.

As for the composition ratio of the multilayer sheet, the ratio of the polycarbonate resin layer laminated on the substrate is 10 of the whole sheet.
It is preferably ˜30% by weight. If it is less than 10% by weight, the heat resistance is lowered, which is not preferable, and if it exceeds 30% by weight, the secondary workability is lowered and it is not economically preferable.

As the polyethylene terephthalate resin of the present invention, those obtained mainly from ethylene glycol, terephthalic acid or its dimethyl ester can be used.
In addition, as the copolymerization monomer, if the glycol component is diethylene glycol, 1,4-tetramethylene glycol, 1,4-cyclohexanedimethanol, heptane methylene glycol, if the dicarboxylic acid component is isophthalic acid, 1,5-naphthalene dicarboxylic acid. It is also possible to use a part of acid, adipic acid, etc. as a monomer and replace them. Preferably, a polyethylene terephthalate resin in which 0.1 to 10 mol% or less of 1,4-cyclohexanedimethanol component is copolymerized as a glycol component, or an isophthalic acid component is 1 mol% to 1 as an acidic component.
A polyethylene terephthalate resin copolymerized with 0 mol% or less can be preferably used in terms of moldability and transparency.

More preferably, the glycol component is 1,
4-cyclohexanedimethanol component is 1 mol% or more 1
A polyethylene terephthalate resin copolymerized with 0 mol% or less is preferable because the crystallization is slower and the impact strength is good.
Crystallization is extremely slow in a copolymer having a molar ratio of more than that, and an extrusion process, a drying process, and a recycling process may cause problems such as fusion and blocking, or the physical properties of the molded product may be deteriorated. Absent.

In addition, although not particularly limited,
Intrinsic viscosity [η] (hereinafter IV value) is 0.6 dl / g when polyethylene terephthalate resin is dissolved in a mixed solvent of 1,4,4-tetrachloroethane and phenol (60:40 weight ratio) and measured at 30 ° C. The above range of 1.0 dl / g or more is preferable. If it is less than 0.6 dl / g, the mechanical strength of the sheet or molded product will be insufficient and it will be easily cracked.
When it is dl / g or more, the melt viscosity is high, the extrusion processability is poor, and the productivity is lowered, which is not desirable.

The polycarbonate resin used in the present invention contains bisphenol as a main raw material and is produced by the phosgene method or the transesterification method. Regarding bisphenol as a raw material, 2,2-bis- (4-
Hydroxyphenyl) propane (bisphenol A),
2,4-bis- (4-hydroxyphenyl) -methyl-
Butane, 1,1-bis- (4-hydroxyphenyl)-
Cyclohexane and the like are included. Further, homopolycarbonate, copolycarbonate obtained by copolymerizing carboxylic acid, or a mixture thereof may be used.

The method for producing the multilayer polyester sheet of the present invention is not particularly limited, but it can be easily carried out by coextrusion molding by a T-die method using a feed block method or a multi-manifold method with a plurality of ordinary extruders. Can be manufactured. Further, since each layer of the resin composition layer of the polyethylene terephthalate resin and the polycarbonate resin of the base material and the polycarbonate resin layer of the surface layer adheres strongly in the molten state, they can be easily laminated without using an adhesive layer. can do.

Further, various additives may be added to the base material and the polycarbonate resin layer in the multilayer sheet of the present invention, if necessary. As additives, colorants, pigments, dyes, antistatic agents, ultraviolet absorbers, energy quenchers, light diffusing agents, optical brighteners, antioxidants, heat stabilizers, slip agents,
Antiblock agents, fillers, matting agents, flame retardants, etc.

For the base material layer, it is also possible to recycle 5 to 50% by weight of the ears and miss rolls of the present sheet generated during sheet production, or a crushed product of the molded product.

The thickness of the sheet of the present invention is from 0.1 mm to 1.
5 mm is preferable, and 0.2 mm to 1.0 mm is more preferable.

The surface of the multilayer sheet of the present invention may be coated with a printing ink, a coating type anti-fog agent or an antistatic agent, if necessary, and may be subjected to corona discharge treatment to improve the effect of the coating agent or may be slipped. It is also possible to apply a silicone oil emulsion for improving the property.

To form the multilayer sheet of the present invention, it is possible to form it into a desired shape by using a commonly used sheet forming method such as vacuum forming or thermoforming. Since the molded product is excellent in heat resistance, transparency and impact resistance at low temperature, it can be used as a container and lid material when thawing frozen food in a microwave oven, and as an ice cream container and lid material. Further, even when used as a container for hot filling of juice, liquor, etc., deformation and whitening due to heat do not occur, so that it can be suitably used.

[0024]

As described above, the present invention provides a polyester sheet for molding which is excellent in heat resistance, transparency and impact strength at low temperature. The heat-resistant transparent multilayer polyester sheet of the present invention has heat resistance and impact resistance that could not be obtained unless it is an engineering plastic such as a conventional polycarbonate resin or polyethylene naphthalate resin, and has almost the same transparency as polyethylene terephthalate. And a sheet having secondary workability. Also, because it is economically superior, it can be used not only for industrial applications but also as a packaging material for foods, and it is mainly used as a packaging container and lid for cooked foods that are heated and thawed in a microwave oven before being eaten. It can be used in a wide range of applications such as materials.

[0025]

The present invention will be described in more detail with reference to the following examples. (Evaluation method) Unless otherwise specified, the physical properties of the sheet and the molded product were measured under the environmental conditions of 23 ° C and 50% humidity as follows. (1) Total Light Transmittance, Surface Haze The samples for measurement were cut out from the sheets and molded articles of each Example and Comparative Example, using a Nippon Denshoku Haze meter to measure J
It was measured according to IS K-7105. (2) Impact strength Samples were cut out from the sheets of each Example and Comparative Example, and a DuPont impact tester manufactured by Toyo Seiki Co., Ltd. was used with a 1/2 inch hemispherical wick, a load of 500 g and 1 kg, and an ambient temperature of 2
It measured at 3 degreeC, -20 degreeC, -30 degreeC, and -40 degreeC. The results are shown as a 50% impact fracture energy value (unit: J) of JIS-K7211. (3) Secondary Workability A tray having a length of 150 mm × a width of 125 mm × a height of 30 mm was prepared from the sheets of Examples and Comparative Examples by a single-shot vacuum forming machine (FK-0431-10 manufactured by Asano Laboratory Co., Ltd.). The moldability was evaluated. ◯: Good Δ: Slightly bad ×: Poor (4) Heat resistance Molded articles formed from the sheets of Examples and Comparative Examples were used in a fine oven DH62 manufactured by Yamato at 90 ° C, 100 ° C,
Heat treatment was performed at 110 ° C. for 10 minutes, and changes in the degree of deformation and transparency were visually evaluated according to the following evaluation criteria. ◯: No deformation Δ: No deformation, but whitened ×: Transformed

Examples 1 to 3 and Comparative Examples 1 to 4 Polyethylene terephthalate (hereinafter referred to as PET) resin (PET9921 manufactured by Eastman, IV value =)
0.80) and Polycarbonate (hereinafter referred to as PC) resin (Mitsubishi Engineering Plastics Corp. Iupilon S)
-3000) was blended at a ratio shown in Table 1 and mixed with stirring. Further, PC resin was used as a raw material for both surface layers of the base material. Each is a dehumidifying dryer PD-3 manufactured by Kawata.
It was dried with 0DAM and P-50DS so that the water content was 50 ppm. Next, the raw materials for the double-sided layers are 40
mm single-screw extruder, base material of 65mm manufactured by Chiyoda Seiki Co., Ltd.
Simultaneously extruded in a single screw extruder at an extrusion temperature of 260 ° C. to 300 ° C., and melted resins were combined with a Sanwa Seiko Ltd. type 2 three-layer feed block (thickness slit ratio 1: 10: 1). Extruded from a 700 mm wide T-die, with a quenching roll, a thickness of 0.50 mm, a sheet composition ratio: base material layer 82 parts by weight / double-sided layer 18 parts by weight (thickness direction composition ratio 1: 9: 1), a two-kind three-layer sheet. Created.

[0027]

[Table 1]

Table 1 shows the results of measuring the total light transmittance, haze, and impact strength of these sheets. Regarding the total light transmittance and the haze, no significant change was observed up to 30 parts by weight of the content of the PC resin in the base material, but when the content was more than 30 parts by weight, the haze was significantly reduced. Regarding the impact strength, no change in the value was observed in any sheet up to -30 ° C, but at -40 ° C, when the content of the PC resin in the base material was less than 5 parts by weight, the strength was significantly lowered. ing.

Table 2 shows the results obtained by molding these sheets into a tray having a shape as shown in FIG. 1 by a single-shot molding machine and evaluating the secondary workability. If the content of the PC resin in the base material is more than 30 parts by weight, the moldability is slightly lowered.

Table 2 shows the results of comparison of heat resistance of molded products. No deformation is observed in any of the sheets up to 130 ° C. However, when the content of PC resin in the base material is less than 5 parts by weight, whitening occurs at 110 ° C. and the transparency is lost, whereas when the content of PC resin is 5 parts by weight or more, whitening does not occur.

[0031]

[Table 2]

Comparative Examples 5 to 6 PET resin (Comparative Example 5) and PC resin (Comparative Example 6) were extruded using the extruder of Example 1 to prepare a single layer sheet having a thickness of 0.5 mm.
The evaluation results are shown in Tables 1 and 2. Although the PET resin single-layer sheet has good transparency and secondary processability, it has a very poor impact strength and heat resistance at low temperatures. The PC resin single-layer sheet has good transparency, impact strength, and heat resistance, but is significantly inferior in secondary workability.

(Examples 4 to 5, Comparative Examples 7 to 8) Example 2
Using the same resin composition (90 parts by weight of PET resin + 10 parts by weight of PC resin) as the base material layer and using 100 parts by weight of PC resin for both side layers, the sheet composition ratio of 2 types and 3 layers is as shown in Table 3. A sheet was prepared in the same manner as in each example.
Table 3 shows the results of evaluating the secondary moldability of these sheets and the heat resistance of the molded product. If the amount of the double-sided layer is more than 30% by weight, the secondary formability is lowered, if it is less than 10% by weight, the heat resistance is lowered, and if the double-sided layer is 5% by weight, the deformation occurs at 110 ° C.

[0034]

[Table 3]

[Brief description of drawings]

FIG. 1 Shape of tray used in Examples

─────────────────────────────────────────────────── --Continued from the front page (56) Reference JP 62-208924 (JP, A) JP 62-181129 (JP, A) JP 60-162646 (JP, A) JP 9- 176463 (JP, A) JP-A-6-122145 (JP, A) JP-A-5-212841 (JP, A) JP-A-4-352635 (JP, A) JP-A-4-62152 (JP, A) Japanese Unexamined Patent Publication No. 3-82530 (JP, A) Actually open 62-197516 (JP, U) Actually open 7-26130 (JP, U) Actually open 1-85205 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) B32B 1/00-35/00 C08L 1/00-101/16

Claims (2)

(57) [Claims] 1. A glycol component containing 1,4-cyclohexa
A resin composition comprising 70 to 95 parts by weight of a poly (ethylene terephthalate) resin copolymerized with 1 to 10 mol% of a dimethanol component and 5 to 30 parts by weight of a polycarbonate resin is used as a base material, and one or both surfaces thereof are coated with the resin composition. A heat-resistant transparent multilayer polyester sheet made by laminating polycarbonate resins. 2. A molded article comprising the heat-resistant transparent multilayer polyester sheet according to claim 1 .