JPH0414874B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a laminated lid material for a container for pressurized and heat sterilization (retort sterilization), and more specifically, the present invention relates to a laminated lid material for a container for pressurized and heat sterilization (retort sterilization), and more specifically, when the lid is opened to take out retort food from the container, it can be peeled off well. Regarding lid material. [Prior art and its problems] Containers for pressurized heat sterilization consist of a container body made of paper, synthetic resin, metal, etc., and a lid with a sealing layer. It can be sealed by heat sealing between the two. The containers thus housed and sealed are sterilized by retort, and after distribution, the lid material is peeled off by hand at the consumer. Therefore, the lid material for this container must have reliable sealing with the container body and ease of opening to the extent that it can be easily peeled off by hand when unsealing. Conventionally, as a lid material for a container for heat and pressure sterilization, a polyester surface layer, a printing layer, an aluminum foil, a polyester reinforcing layer, and a polyolefin sealing layer are laminated in this order, and the interlayer is a urethane two-component curing type. Laminates bonded by adhesives are used. However, when the conventional lid is used for sealing, the urethane two-component curing adhesive layer between the polyester reinforcing layer and the sealing layer breaks when the seal is opened, causing a portion of the sealing layer to break at the mouth of the container body. There is a problem in that the film remains behind, resulting in film formation, fuzzing, etc., and a poor appearance at the peeled and unsealed part. In particular, when reheating the contents and peeling off the lid, the urethane two-component curing adhesive may soften and peel off from the adhesive layer, leaving the entire sealing layer at the mouth of the container body. . This invention was made against the background of the above-mentioned circumstances, and its purpose is to ensure sealing performance even during retort sterilization, and to provide a method that can be easily handled by hand without problems such as film formation or fuzzing. To provide a lid material for a container for heating and pressurizing sterilization whose lid can be easily peeled off. [Means for Solving the Problems] As a result of various tests and research conducted by the present inventors to achieve the above objectives, the present inventors found that maleic anhydride-modified polyolefin was used as an adhesive for bonding the sealing layer to other layers. The present inventors have found that the use of resin is effective in achieving the object of the present invention, and have completed the present invention. That is, the laminated lid material for a container for pressure and heat sterilization of the present invention is a laminated material comprising a polyester surface layer, a reinforcing layer, an aluminum layer, and a sealing layer made of a blend of polypropylene and polyethylene. The aluminum layer and the sealing layer are laminated with an adhesive made of maleic anhydride-modified polyolefin resin. In a preferred embodiment of this invention, the reinforcing layer can be made of nylon. In addition, as another embodiment, the sealing layer is made of polypropylene, polypropylene, and polyethylene.
It may be added by weight%, or an inorganic substance may be added thereto. Furthermore, as one aspect of the present invention, the polyester surface layer can be printed on the inside with ink. In a preferred embodiment of the present invention, the adhesive layer made of maleic anhydride-modified polyolefin resin can have an average layer thickness of 10 to 100 microns, preferably 20 to 50 microns. In another embodiment, the reinforcing layer can be laminated with the sealing layer using an adhesive made of maleic anhydride-modified polyolefin resin. This invention will be explained in more detail below. The laminated lid material of this invention consists of a polyester surface layer, a reinforcing layer, an aluminum layer, and a sealing layer made of a blend of polypropylene and polyethylene. Preferably, a biaxially stretched film is used as the polyester for the surface layer.
The layer thickness is, for example, 10 μm to 50 μm. The front and/or back sides of this polyester film can be printed with ink if necessary. The reinforcing layer plays the role of reinforcing the lid material so that the lid material does not tear during opening. Therefore, preferably a biaxially stretched nylon film is used as the reinforcing layer. Types of nylon include nylon-6 and nylon-6,6. The thickness of the nylon film is, for example, 10μ ~
It is 30μ. As the aluminum that is the intermediate layer, for example, aluminum foil having a thickness of 5 μm to 50 μm can be used. The sealing layer of the lid, which joins the flange at the mouth of the container body and seals the contents of the container, is made of a blend of polypropylene and polyethylene. Various additives can be added to the blend. Examples include fillers, plasticizers, antioxidants, heat stabilizers, softeners, and binders. When preparing the polyolefin layer, it is necessary to select the polyolefin, composition, and additives in consideration of sealing reliability and ease of peeling. Of the above-mentioned layers, the aluminum layer and the sealing layer are laminated using an adhesive made of maleic anhydride-modified polyolefin resin. Further, the reinforcing layer can also be adhered to the aluminum layer with an adhesive made of maleic anhydride-modified polyolefin resin. That is, the reinforcing layer can also be laminated with the sealing layer using an adhesive made of maleic anhydride-modified polyolefin resin. Generally, this can be carried out by a coextrusion method, a sandwich lamination method, an extrusion coating method, or the like. The maleic anhydride-modified polyolefin resin used here can be obtained by reacting maleic anhydride with polyolefin under pressure and heat. Carboxyl groups derived from maleic anhydride improve adhesion to aluminum foil surfaces or nylon film surfaces. Polyolefins modified with maleic anhydride include polyethylene, polypropylene, polybutene, and blend polymers thereof. When polypropylene is used as the polyolefin, at least one of polyethylene and an inorganic substance (such as talc) is added to the polypropylene.
It is preferable to add ~50wt%. This is because the addition imparts easy peelability. Each layer may be laminated by a conventional lamination method other than lamination using an adhesive made of the maleic anhydride-modified polyolefin resin described above. For example, they can be bonded and laminated by dry lamination. Adhesives for dry lamination generally include urethane-based two-component curing adhesives, epoxy-based adhesives, and epoxy-based adhesives that have heat resistance and water resistance.
Examples include polyester adhesives and copolymerized nylon adhesives. It is desirable to reduce the thickness of the adhesive layer as long as adhesion is not impaired. In this invention, the average layer thickness of the maleic anhydride-modified polyolefin resin adhesive is preferably 10 μ to 100 μ. If this upper limit is exceeded, there is a risk that the lid material will be difficult to open when peeled off from the cup, or that the sealing material may remain partially on the cup flange. Moreover, if it is less than the above-mentioned lower limit, the film may be cut or a hole may be formed when laminating the sealing material, or the seal may be too weak when sealing. A laminated example of the lid material of the present invention will be explained with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing a laminated example of the present invention. This lid material example 1 includes a biaxially stretched polyester surface layer 2 (thickness 10μ to 50μ), a nylon reinforcing layer 3 (thickness 10μ to 30μ), and an aluminum layer 4.
(thickness: 5 μm to 50 μm) and a polyolefin inseal layer 5 (thickness: 20 μm to 200 μm), and a printed layer 6 is provided on the inner surface of the surface layer. The surface layer 2 and the nylon reinforcing layer 3 are laminated via the urethane two-component curing adhesive layer 7, and the nylon reinforcing layer 3 and the aluminum layer 4 are laminated in the same manner. The aluminum layer 4 and the sealing layer 5 are laminated via a maleic anhydride-modified polyolefin adhesive layer 9. FIG. 2 is a cross-sectional view schematically showing another example of lamination. In this example, the lid material 1 includes a biaxial polyester film surface layer 2, a printed layer 6, a urethane adhesive layer 8, an aluminum layer 4, a copolymerized nylon adhesive layer 10, a nylon reinforcing layer 3, and a maleic anhydride layer. The modified polyolefin adhesive layer 9 and the polyolefin layer 5 are laminated in this order. Next, how to use the lid material of this invention will be explained. This lid material is cut into a predetermined shape, and as shown in FIG.
0 surface and heat sealed. In this case, the flange portion 20 of the container body 15 is preferably made of the same polyolefin as the sealing layer of the lid 1. To open the container, grasp the end of the lid 1 by hand and peel the lid from the container body. [Effects of the Invention] The following effects can be obtained by using the lid material of the present invention. (a) In many conventional lid materials, the entire sealing layer of the multilayer lid material remains on the container body when the container is opened (delamination), or a portion of the lid material breaks when the container is opened and remains on the container body. Something happened. According to the present invention, the sealing layer and the adjacent layer are bonded via the maleic anhydride-modified polyolefin adhesive, so that film tension can be eliminated. (b) In addition to the polyester surface layer, a reinforcing layer is provided as an intermediate layer to provide toughness to the lid material, so that when the lid peels off and the lid is opened, broken pieces of the lid will not be left at the mouth of the container body. The entire lid can be removed without leaving any residue. (c) Since the seal layer is made of a blend of polypropylene and polyethylene, it has easy peelability. [Example] The present invention will be specifically explained using the following example. Example 1 A desired pattern or symbol was printed on the surface of a 12μ thick biaxially stretched polyester using reactive gravure ink. The printed surface of the polyester layer was laminated with a 15μ thick nylon film using a urethane based two-component curing adhesive layer, and further laminated with a 9μ thick aluminum foil using the same urethane based adhesive layer. The obtained laminate was adhered to a polypropylene resin film having the following composition by a sandwich lamination method using a maleic anhydride-modified polyolefin resin. Weight % Polypropylene 70 Polyethylene 25 Talc 5 The thickness of the maleic anhydride-modified polypropylene adhesive layer of the obtained multilayer lid material was 10 μm. Example 2 (comparative example) A desired pattern, etc. is printed on the back side of 12μ thick biaxially stretched polyester using reactive gravure ink, and this printed surface is coated with 9μ aluminum foil and 50μ thick aluminum foil using a urethane two-component curing adhesive. It was sequentially laminated with polypropylene film. Example 3 (Test Example) Using the lid materials obtained in Examples 1 and 2, a container made of polypropylene was sealed and sterilized by retort. Next, we varied the temperature at which the package was opened and observed whether defects occurred when the package was opened. Number of samples each
The results for 300 pieces are shown in Table 1.

[Table] As is clear from Table 1, the lid material of the present invention had no defects at all, and the peelability was dramatically improved compared to the conventional lid material (Example 2).

[Brief explanation of drawings]

1 and 2 are cross-sectional views schematically showing an example of the multilayer lid material of the present invention, and FIG. 3 is a cross-sectional view showing a container sealed with the lid material. 1... Lid material, 2... Surface layer, 3... Reinforcement layer, 4
... Aluminum layer, 5 ... Seal layer, 6 ... Printing layer, 7 ... Urethane adhesive layer, 8 ... Urethane adhesive layer, 9 ... Maleic anhydride modified polyolefin adhesive layer, 10 ... Copolymerized nylon adhesive layer, 10... Container body, 20... Flange portion.

Claims (1)

[Scope of Claims] 1. A laminated material comprising a polyester surface layer, a reinforcing layer, an aluminum layer, and a sealing layer made of a blend of polypropylene and polyethylene,
A laminated lid material for a container for pressure and heat sterilization, characterized in that the aluminum layer and the sealing layer are laminated with maleic anhydride-modified polyolefin. 2. The laminated lid material according to claim 1, wherein the reinforcing layer is nylon. 3 Seal layer is polypropylene and polyethylene 5
The laminated lid material according to claim 1, which is made of a blend to which ~50% by weight is added. 4 Seal layer is polypropylene and polyethylene 5
The laminated lid material according to claim 1, which is made of a blend containing ~50% by weight and an inorganic substance. 5. The laminated lid material according to claim 1, wherein the polyester surface layer is printed on the inside with ink. 6. The laminated lid material according to claim 1, wherein the adhesive layer made of maleic anhydride-modified polyolefin has an average layer thickness of 10μ to 100μ. 7. The laminated lid material according to claim 1, wherein the reinforcing layer is laminated with the sealing layer using an adhesive made of maleic anhydride-modified polyolefin.