JPH0528181B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a coextruded multilayer sheet, and more specifically, it provides a coextruded multilayer sheet that has excellent rigidity and gas barrier properties and is suitable for forming deep-drawn containers. . (Prior art) Linear polyester in general, and polyethylene terephthalate (hereinafter referred to as PET) in particular, has attracted attention as a material for various containers including bottles due to its excellent mechanical and chemical properties. -Represented by the method described in Publication No. 5107
Demand for deep-drawn containers made from PET sheets is also increasing as they have excellent rigidity and gas barrier properties. However, as packaging technology improves and packaging uses expand, higher functionality is required of PET containers, including improved gas barrier properties. As a means of improving the gas barrier properties of such PET containers, partially saponified resins of ethylene/vinyl acetate copolymer (hereinafter referred to as EVOH), which are materials with better gas barrier properties, or vinyl resins mainly based on EVOH are being used. A multilayer sheet coextruded with PET and PET has been proposed, and the technology is being actively developed, but it has not yet been put into practical use. (Problem to be solved by the invention) Despite the highly acclaimed effects of the high-performance sheet created by combining PET/EVOH, the main reason why it has not been put to practical use is the poor adhesion between the two. There's a problem. While PET has a highly crystalline, non-polar molecular structure, EVOH has a polar molecular structure with hydroxyl groups with large molecular cohesive energy, and for this reason, PET and EVOH do not adhere at all. Therefore, although an adhesive layer is indispensable in the middle for forming PET/EVOH multilayer sheets, an adhesive suitable for forming sheets for deep-drawn containers has not yet been found. Of course just
If the purpose is to bond PET and EVOH, adhesives based on acid anhydride group-containing polyolefins or epoxy group-containing polyolefins have already been put into practical use. However, in addition to adhesive strength, adhesives for coextruded multilayer sheets intended for secondary processing such as deep drawing are required to have secondary processability such as suitability for melt extrusion and stretching processing, as well as transparency. Naturally, none of the existing adhesives has been found that comprehensively satisfies these requirements. In order to solve this problem, polyamide-based and polyester-based adhesives have been developed. For example, as described in Japanese Patent Application Laid-Open No. 135473/1983, adhesives of thermoplastic polyester with a low softening point have been developed. An effective method for bonding PET and EVOH has been reported, however, such adhesives cause a large decrease in melt viscosity under melt extrusion conditions for PET and EVOH, making it difficult to form uniform coextruded multilayer sheets. This makes molding difficult. (Means for Solving the Problems) The present inventors have solved these problems, and have developed a product that has excellent rigidity and gas barrier properties, can maintain transparency if necessary, and can also be used for deep drawing processing, etc. PET with secondary stretch processability/adhesive layer/
In order to develop a coextruded multilayer sheet with EVOH as the basic unit, we have arrived at the present invention as a result of extensive research, particularly regarding the adhesive layer. That is, the present invention provides a multilayer sheet having an adhesive layer between a polyester resin layer mainly composed of PET or a partially saponified EVOH resin or a vinyl resin layer mainly composed of EVOH. This is a coextruded multilayer sheet characterized in that the layer is a blend of sulfonic group-containing polyester and polyamide in a weight ratio of 30/70 to 70/30. Furthermore, the sulfonic group-containing polyester in such a blend contains 90% terephthalic acid as the acid component.
~10 mol%, isophthalic acid 10~90 mol%, and sodium sulfoisophthalic acid 1~15 mol%, the alcohol component is ethylene glycol, and the polyamide contains nylon 66 component 5~15 mol%. Nylon 6.66 containing 30% by weight
This is a coextruded multilayer sheet characterized by imparting transparency by using a copolymerized polyamide blend as an adhesive layer. The structure of the multilayer sheet according to the present invention is a five-layer structure consisting of PET/adhesive layer/EVOH as a basic unit, PET/adhesive layer/EVOH/adhesive layer/PET, or a multilayer structure with more layers as necessary. can do. The PET used in the present invention is a polyester whose main repeating unit is ethylene terephthalate, and the amount of phthalic acid, isophthalic acid, hexahydrophthalic acid, naphthalene dicarboxylic acid, adipic acid, and sebacin is 10 mol% or less of the total acid component. It is possible to use dicarboxylic acids such as acids, polyhydric carboxylic acids such as trimellitic acid and pyromellitic acid, or oxyacids such as P-oxbenzoic acid as the acid component, and in an amount of 10 mol% or less of the total alcohol component. 1,2-propanediol, 1,
Dihydric alcohols such as 3-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, cyclohexanedimethanol, trimethylolpropane, triethylolpropane, pentaerythritol, etc. Polyhydric alcohols and the like can be used as the alcohol component. Such PET can be obtained by a conventional melt polycondensation reaction, and if necessary, the degree of polymerization can be further increased by solid phase polymerization. The EVOH used in the present invention has the trade name “EVAL”
It is a crystalline polymer obtained by saponifying a random copolymer of ethylene/vinyl acetate, as represented by the following: It has polar hydroxyl groups and exhibits extremely excellent gas barrier properties due to its large molecular cohesive energy. The sulfon group-containing polyester, which is a component in the blend used as the adhesive layer of the present invention, is usually prepared by using sodium sulfoisophthalic acid or sodium sulfo terephthalic acid as part of the acid component in the polyester. It can be easily obtained by a melt polycondensation reaction according to the method, but when a high degree of polymerization is required, a solid phase polymerization reaction can also be used. Among such sulfon group-containing polyesters, the copolyester having the composition described in the present invention for forming a transparent multilayer sheet further contains phthalic acid, hexahydrophthalic acid, and naphthalene in an amount of 10 mol% or less of the total acid component. Dicarboxylic acids such as dicarboxylic acid, adipic acid, azelaic acid, and sebacic acid, polyhydric carboxylic acids such as trimellitic acid and pyromellitic acid, or oxyacids such as P-oxybenzoic acid can be used as the acid component; 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,6 in an amount of 10 mol% or less of the total alcohol component
-hexanediol, neopentyl glycol,
Dihydric alcohols such as diethylene glycol, triethylene glycol, and cyclohexanedimethanol, and polyhydric alcohols such as trimethylolpropane, triethylolpropane, and pentaerythritol can be used as the alcohol component. The polyamide, which is also a component in the blend, is selected from polycapramide, polylaurinlactam, polyhexamethylene adipamide, and poly-11-aminoundecanoic acid.
Although these may be used alone, as a copolymer, or as a mixture, it is preferable to use a nylon 6/66 copolymer polyamide containing 5 to 30% by weight of a nylon 66 component for forming a transparent multilayer sheet. By melt-blending these sulfon group-containing polyesters and polyamides using a melt extruder, a uniform composition can be easily prepared. The multilayer sheet obtained by the present invention has a
After being heated in a range of 150°C, it can be easily made into a deep-drawn container by vacuum forming or pressure forming. (Function) The present invention utilizes the excellent compatibility of sulfon group-containing polyester, which has excellent adhesion to PET, and polyamide, which has excellent adhesion to EVOH, to create a homogeneous melt blend of PET/
By using EVOH as an adhesive layer, it is a coextruded multilayer sheet that has strong mutual adhesion.This adhesive layer exhibits extremely strong adhesion with PET and EVOH, and at the same time
It has melt viscosity characteristics similar to EVOH, and therefore can be easily formed into a uniform multilayer sheet by extrusion from a multilayer die. In addition, such sheets have excellent secondary processability such as stretching, and depending on the composition of the blend that becomes the adhesive layer, it is possible to form transparent sheets, making them suitable for forming deep-drawn containers. It is a useful material rich in (Example) Next, the present invention will be specifically described with reference to Examples, but the present invention is not limited thereto. Example 1 77 mol % of terephthalic acid, 15 mol % of isophthalic acid, 5 mol % of sebacic acid, 3 mol % of 5-sodium sulfoisophthalic acid as acid components and ethylene glycol as alcohol component were melted in a conventional manner. A condensation reaction was carried out to obtain a sulfonic group-containing polyester having an intrinsic viscosity of 0.70 as measured at 20°C in a mixed solvent of equal weights of phenol/tetrachloroethane. On the other hand, nylon 6.6 contains 15% by weight of nylon 66 component and has a relative viscosity of 4.5 when measured at 25°C in 96% concentrated sulfuric acid.
66 copolyamide was prepared, and after thoroughly drying both, equal amounts of each were extruded using a melt extruder to obtain a transparent blend. Separately, prepare PET with an intrinsic viscosity of 1.0 and EVOH (EVAL EP-F manufactured by Kuraray Co., Ltd.) with an MI (melt index) value of 1.40 g measured at 190°C for 10 minutes with a load of 2160 g, and mix these materials sufficiently. PET (340μ) / adhesive layer (20μ) /
EVOH (80μ) / adhesive layer (20μ) / PET (340μ)
A sheet with a thickness of 800μ was obtained. As far as observation with the naked eye was concerned, it was a uniform and transparent sheet of EVOH with no uneven thickness, and each layer was firmly adhered. This sheet was heated at 130°C for 5 seconds and then vacuum formed into a cup with a diameter of 100 mm and a depth of 40 mm, resulting in a uniformly stretched transparent product. Examples 2 to 4, Comparative Examples 1 to 3 Multilayer sheets with adhesive layers made of various polyester/polyamide blends having different composition conditions were molded according to the method of Example 1, and the results were as follows: Tables 1 and 2 The results were obtained. In the table, TPA stands for terephthalic acid, IPA stands for isophthalic acid, SEA stands for sebacic acid, Na-SIPA stands for 5-sodiumsulfoisophthalic acid, and EG stands for ethylene glycol.

【table】

【table】

[Table] (Effects of the invention) As is clear from Examples 1 to 4, the multilayer sheet having the basic unit of PET/adhesive layer/EVOH that satisfies the requirements of the present invention has excellent extrusion moldability.
It has excellent uniformity and interlayer adhesion, and by limiting the composition of the adhesive blend, it can be made into a transparent sheet. Furthermore, this sheet has excellent deep drawing workability, and allows containers with excellent rigidity and gas barrier properties to be easily manufactured.

Claims (1)

[Claims] 1. An adhesive layer is provided between polyethylene terephthalate or a polyester resin layer mainly composed of polyethylene terephthalate and a partially saponified resin of ethylene/vinyl acetate copolymer or a vinyl resin layer mainly composed of this. In a multilayer sheet having a structure, the adhesive layer is composed of a sulfon group-containing polyester and a polyamide.
A coextruded multilayer sheet characterized by being a blend with a weight ratio of 70 to 70/30. 2 The sulfon group-containing polyester contains 90 to 10 mol% of terephthalic acid and 10 to 10 mol% of isophthalic acid as acid components.
90 mol%, Sodium sulfoisophthalic acid 1~
2. The coextruded multilayer sheet according to claim 1, which is a copolymerized polyester consisting of 15 mol% and whose alcohol component is ethylene glycol. 3 Polyamide contains 5-30% by weight of nylon 66 component
2. The coextruded multilayer sheet according to claim 1, wherein the adhesive layer is a blend of nylon 6 and 66 copolyamide.