JPH03128242A - Heat resistant and transparent sheet - Google Patents

Abstract

PURPOSE:To obtain the multilayer plastic sheet with gas-barrier property, while its transparency and shape-retaining property is kept even if sterilizing treatment under heating is carried out by inserting the resin layer having affinity with polycarbonate resin layer and polyethylene terephthalate resin layer between said two layers. CONSTITUTION:A heat resistant and transparent sheet is constituted by positioning the transparent poly-carbonate(PC) with high glass transition point for a central layer, the polyethylene terephthalate (PET) having gas-barrier property and excellent secondary workability for both outer layers and modified polyolefin for both intermediate layers between the central layer and both outer layers, and then in another process, said sheet is constituted by positioning PET for the central layer, PC for both outer layers and polybutylene terephthalate for the intermediate layer. That is to say, the multilayer sheet having the structure made by inserting the resin layer which is different from PC and PET and has the affinity with said both materials may be produced.

Description

Detailed Description of the Invention (Industrial Field of Application) In the present invention, a polycarbonate resin layer and a polyethylene terephthalate resin layer are different from each other.

This invention relates to a multilayer plastic sheet characterized by having a resin layer interposed therebetween that has an affinity for both.

In particular, the present invention is thermoplastic and transparent.

It also has heat resistance and gas barrier properties, and when forming containers,
This invention relates to a multilayer plastic sheet that does not cause peeling between the eyebrows.

(Prior Art) Transparent sheets using various thermoplastic resins are already known.

Polyester sheet has transparency, impact strength, and gas barrier.
Although it is almost satisfactory in terms of properties and secondary processability, it is inferior in heat resistance. Sheets made of polycarbonate are
Although it has excellent heat resistance, transparency, and impact strength, it has extremely poor gas barrier properties.

Furthermore, when exposed to ultraviolet (UV) light for a long period of time, there is a problem in that minute cracks are formed on one surface and the surface becomes cloudy.

Polycarbonate/polyester multilayer sheet is heat resistant,
Although it has excellent transparency and impact strength, it has the drawback of causing delamination between one layer when molding a container by thermoforming or the like.

(Problems to be Solved by the Invention) An object of the present invention is to provide a multilayer plastic sheet that has transparency and shape retention even after heat sterilization treatment, and also has gas barrier properties. .

(Means for Solving the Problems) As a result of extensive research for this purpose, the present inventors selected polycarbonate (hereinafter referred to as PC), which is transparent and has a high glass transition point, from among a large number of thermoplastic resins, and a gas barrier material.
It has been found that the above object can be achieved by selecting a combination with polyethylene terephthalate (hereinafter referred to as PUT) which has good properties and good secondary processability.

In other words, by creating a multilayer sheet with a structure in which PC and PET are different from each other and have a resin layer that has an affinity for both, a container that is molded by thermoforming or the like and which does not peel off between the eyebrows can be heated and sterilized. Even if
The present invention was achieved by discovering that transparency, shape retention, and gas barrier properties can be obtained.

For example, a structure in which PC is placed in the center layer, PET is placed in both outer layers, and modified polyolefin is placed in both intermediate layers between the center layer and both outer layers, or PET is placed in the center layer.

A heat-resistant transparent sheet having PC as both outer layers and polybutylene terephthalate (hereinafter referred to as PBT) as an intermediate layer is preferred. Further, as the center layer, a material recovered during secondary processing of the multilayer sheet can be used.

In addition, another layer in the center of the center layer is made of ethylene-vinyl alcohol copolymer (EV), which has high gas barrier properties.
OH), polymethaxylylenecyamine adipamide (M
XD-6), gas barrier made of non-quality polyamide resin, etc.
By providing a material layer, it is also possible to manufacture a container having heat resistance and high gas barrier properties. in this case,
On the outside of the gas barrier material layer, a maleic anhydride-grafted modified ethylene-vinyl acetate copolymer, high-density polyethylene, low-density polyethylene, linear low-density polyethylene, polypropylene, or a composition mainly composed of these is used as an adhesive layer. It is preferable to use

The thermoplastic aromatic PC used in the present invention is obtained from phosgene and dihydric phenol or a derivative thereof.

A specific example of a preferred dihydric phenol is 2°2-bis(4-hydroxyphenyl)propane.

2.2-bis(4-hydroxy-3,5-dibromophenyl)propane, 2.2-bis(4-hydroxy-3,
5-dichlorophenyl)propane, 4.4'-dihydroxydiphenyl sulfone, 4.4'-dihydroxydiphenyl ether, 4.4''-dihydroxydiphenyl sulfide, 4,4''-dihydroxydiphenyl ketone, 4,4°-dihydroxydiphenylmethane, 2 ．．
2'-bis(4-hydroxy-3,5-dimethylphenyl)propane, 1. -Bis(4-hydroxyphenyl)ethane, 111-bis(4-hydroxyphenyl)cyclohexane, 4,4'-dihydroxydiphenyl,
Examples include hydroquinone.

These may be used alone or in combination of two or more. Furthermore, although these dihydric phenols are para-substituted, other isomers may also be used.

Furthermore, ethylene glycol, propylene glycol, etc. may be used in combination with these dihydric phenols.

The most typical dihydric phenol is 2°2-bis(4-hydroxyphenyl)propane.

It is commonly called bisphenol A and is most preferred from the viewpoint of comprehensive physical properties.

PET used in the present invention is obtained by melt polymerizing a low polymer obtained by a normal esterification reaction or transesterification reaction from terephthalic acid or a lower alkyl ester of terephthalic acid and ethylene glycol by a normal method. or those obtained by solid phase polymerization. A thermoplastic polyester having at least 80 mol% of ethylene terephthalate units is desirable.

That is, it means a copolymer consisting of 80 mol% or more of ethylene terephthalate units and other repeating units, that is, other copolymer components, and the other copolymer components include various acid components and polyhydric alcohol components. can be used.

For example, acid components include phthalic acid, isophthalic acid, succinic acid, adipic acid, sebacic acid, dodecanedicarboxylic acid, and hexahydroterephthalic acid.

Examples of the polyhydric alcohol component include 2,6-naphthalenedicarboxylic acid, 2,5-dibromoterephthalic acid, diphenyldicarboxylic acid, trimellitic acid, trimesic acid, and pyromellitic acid.

Propylene glycol, diethylene glycol.

Tetramethylene glycol, polyethylene glycol,
Polytetramethylene glycol, 1,6-hexanediol, trimethylene glycol, 2-obentyl glycol, p-xylylene glycol 1,4-cyclohexane dimetatool, bisphenol A, glycerin, pentaerythritol, trimethanol propane, trimethanol Examples include benzene, triethanol, and benzene.

The molecular weight of thermoplastic polyester is approximately io, ooo to io
The range of o and ooo is preferable from the viewpoint of physical properties and extrusion processability. In order to obtain high transparency at high temperatures, copolymerized polyester is suitable because it is difficult to crystallize.

What is the modified polyolefin used in the present invention?

Examples include ethylene-vinyl acetate copolymers, high-density polyethylene, low-density polyethylene, linear low-density polyethylene, and maleic anhydride graft-modified polypropylene, and compositions mainly composed of these.

PBT used in the present invention is a polyester obtained by polycondensing terephthalic acid or its lower alkyl ester with 1°4-butanediol using an organic titanium compound and/or an organic tin compound as a catalyst.

Isophthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, 237-naphthalenedicarboxylic acid, 1
, 5-naphthalene dicarboxylic acid, methyl terephthalic acid,
4,4°-biphenyldicarboxylic acid, 2,2'-biphenyldicarboxylic acid, 1,2-bis(4-carboxyphenoxy)ethane, succinic acid.

Adipic acid, speric acid, azelaic acid, sebacic acid,
Other dicarboxylic acids such as dodecanedicarboxylic acid, octadecanedicarboxylic acid, dimer acid or ethylene glycol, propylene glycol.

1.5-bentanediol, 1.6-hexanediol, 1.8-octanediol, 1.10-decanediol, cyclohexane dimetatool, 2.2-bis(2
Those substituted with other diols such as '-hydroxyethoxyphenyl)propane can also be used.

In the present invention, it is necessary that the glass transition temperature of PC is 120°C or higher. The reason for this is that when used in food containers etc., the container will not be deformed even if heat sterilization is performed. The elastic modulus of thermoplastics in the glass state below the glass transition temperature is generally about 10.
The value is approximately "dyne/cm". However, as the temperature rises and approaches the glass transition temperature, the elastic modulus rapidly decreases, and the equilibrium elastic modulus based on rubber elasticity (10b = 107d
yne/cm2).

When the elastic modulus is plotted against temperature, it can be seen that the absolute value decreases by about three orders of magnitude in a temperature range of 10-odd degrees Celsius across the glass transition temperature. Therefore, the heat resistance of a sheet made of a single layer of thermoplastic plastic is determined by its glass transition temperature.

On the other hand, the PC used in the multilayer sheet of the present invention has a glass transition temperature of 120°C or higher, and the crystallization rate of PET is low, so even if a container made of the sheet is heat sterilized (80°C), , does not cause whitening or deformation due to crystallization. Since PET has much better gas barrier properties than PC, the multilayer sheet of the present invention has gas barrier properties.

When molding deep-drawn containers using thermoforming, etc., PC-PE can be used as an intermediate layer that is easier to mold than PET.
Prevents peeling at the T interface.

(Examples) Next, the present invention will be explained in detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Example 1 Both outer layers were made of polycarbonate resin with an intrinsic viscosity of 0.80 (Kneepilon manufactured by Mitsubishi Gas Chemical Co., Ltd.), and the center layer was made with an intrinsic viscosity of 0.
．． 85 polyethylene terephthalate resin (Unitika (
PET (manufactured by Mitsubishi Yuka Co., Ltd.) and the middle layer is a maleic anhydride-grafted modified ethylene-vinyl acetate copolymer resin (Mitsubishi Yuka Co., Ltd.).
(Modic) manufactured by Co., Ltd.).

A five-layer sheet having the configuration shown in Table 1 was coextruded using a multilayer extrusion molding machine under the following molding conditions.

All extruders use 65φ screws, and the merging system uses a feed block system. Die temperature 285°C1
A 5-layer sheet with a total thickness of 1.0 mm was produced under the conditions of a cooling roll at 30° C. and a take-up speed of 2.5 m/min.

Example 2 Polyethylene terephthalate resin (PET manufactured by Unitika Co., Ltd.) having an intrinsic viscosity of 1.00 was used for both outer layers and the center layer.

The intermediate layer is a polycarbonate resin with an intrinsic viscosity of 0.90 (Niepilon manufactured by Mitsubishi Gas Chemical Co., Ltd.), and the maleic anhydride-grafted modified ethylene-vinyl acetate copolymer resin (Mitsubishi Oil Chemical Co., Ltd.) is used between the outer layer and the intermediate layer and between the intermediate layer and the center layer. A sheet was produced under the same conditions as in Example 1 except that 3 types and 9 layers were used (Modic Co., Ltd.).

Comparative Example 1 Using the polyethylene terephthalate resin of Example 1,
A single layer sheet was produced in the same manner as in Example 1.

Comparative Example 2 A single layer sheet was produced in the same manner as in Example 1 using the polycarbonate resin of Example 1.

Comparative Example 3 A three-layer sheet was produced in the same manner as in Example 1 using the polycarbonate resin of Example 1 for both outer layers and the polyethylene terephthalate resin of Example 1 for the center layer.

Comparative Example 4 A 5-layer sheet was produced in the same manner as in Example 1 using the polyethylene terephthalate resin of Example 1 for both outer and center layers and the polycarbonate resin of Example 1 for the middle layer.

Table 1 MAH: Maleic anhydride graft modified ethylene vinyl acetate copolymer resin (Note) w-mi ratio: 5 layers 2515/4015/25 (
%) 9 layers 1015/1515/3015/1515/1
0 (%) 3 layers 25150/25 (%) (a) Determined by the appearance of whitening and deformation of the container (b) Unit: kg/25 mm (20°C) Sample 2 Container with drawing ratio 1.3 (c) Unit : cc-mm/m”-day-atm
(20″C) As can be seen from Table 1, even though the comparative example has excellent heat resistance, the interlayer adhesion strength after container molding is quite poor.However, in the example, heat sterilization is possible. It has a heat resistance of 80'C, good gas barrier properties, and excellent interlayer adhesive strength.

Needless to say, the secondary workability was very good.

(Effects of the Invention) The packaging container molded using the sheet according to the present invention has high functionality that has not been achieved conventionally, such as transparency, heat sterilization, and good gas barrier properties, and is suitable for food distribution. The adhesive strength is strong enough that the container itself will not peel off.

Claims (5)

[Claims] (1) A multilayer plastic sheet characterized in that a resin layer made of a resin other than the two resins and having an affinity for both is interposed between a polycarbonate resin layer and a polyethylene terephthalate resin layer. (2) The product has a five-layer structure in which the center layer is made of polycarbonate, both outer layers are made of polyethylene terephthalate, and both intermediate layers between the center layer and both outer layers are made of modified polyolefin. multilayer plastic sheet. (3) Claim (1) characterized in that it has a five-layer structure in which polycarbonate is placed in the center layer, polyethylene terephthalate is placed in both outer layers, and polybutylene terephthalate is placed in both intermediate layers between the center layer and both outer layers. Multilayer plastic sheet as described. (4) A five-layer structure in which polyethylene terephthalate is placed in the center layer, polycarbonate is placed in both outer layers, and modified polyolefin is placed in both intermediate layers.
1) Multilayer plastic sheet as described. (5) The multilayer plastic sheet according to claim (1), characterized in that the center layer is made of polyethylene terephthalate, both outer layers are made of polycarbonate, and both intermediate layers are made of polybutylene terephthalate, resulting in a five-layer structure.