JP3024977B2 - Heat-sealable packaging material with heat resistance - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a polyester resin-based packaging material having heat resistance enough to withstand retort sterilization and having good heat seal strength after retort sterilization.

[Prior Art] Conventionally, polyolefins such as polyethylene and polypropylene are generally used as packaging materials such as soft packaging materials, container materials, and lid materials, and these are sealed by a method of heat-sealing each other.

However, in the case of polyolefin packaging materials, antioxidants and other additives are eluted in the process of forming into films, etc., and these migrate to the packaged contents. And the problem of adsorption of the flavoring component and other active ingredients in the contents to the packaging material.

In order to solve such problems, it has been proposed to use polyethylene terephthalate (PET) as the inner layer of the packaging material. However, PET has a problem in heat sealability, and a solution for it has been demanded.

[Problems to be Solved by the Invention] The present invention has been made in view of the above circumstances, and there is no possibility that the contents will taste unpleasant or unpleasant odor. It is an object of the present invention to provide a packaging material which can improve adsorption, has excellent heat sealing properties, and has a small decrease in heat sealing strength after retort sterilization.

[Means for Solving the Problems] In order to solve the above problems, the present invention uses two or more acids containing terephthalic acid as a main component as a dicarboxylic acid component (hereinafter, simply referred to as an acid component) constituting a polyester. Take steps.

That is, the present invention comprises two or more acids mainly composed of terephthalic acid as an acid component constituting the polyester, at least 10 mol of ethylene glycol as a diol component, and has a melting point of 120 to 133 ° C., or A heat-sealable packaging material having heat resistance provided with at least an amorphous polyester resin as an inner surface layer. [Function] The packaging material of the present invention has a small decrease in seal strength after retort sterilization and a small seal strength. The width can be 2.3 kg / 15 mm or more, and there is no risk of deformation such as wrinkles after retort sterilization even when used as a lid material for containers.

[Example] The packaging material of the present invention is described above with reference to the drawings.

The drawing shows an example of a three-layer structure, which comprises an inner surface layer 1 made of a polyester resin, which is a feature of the present invention, and an outer surface layer 3 laminated on the inner surface layer with an intermediate layer 2 interposed therebetween. The inner surface layer 1 is composed of two or more acids containing terephthalic acid as a main component as an acid component and a polyester resin containing at least 10 mol% of ethylene glycol as a diol component. The diol component may include 1,4-butanediol, neopentyl glycol, propylene glycol, etc. in addition to ethylene glycol.

The intermediate layer 2 and the outer layer 3 can be appropriately selected depending on the intended use of the packaging material. For example, when the intermediate layer 2 is used as a lid material for a container for sterilizing retorts, ethylene-
Vinyl alcohol copolymer (EVOH), polyvinylidene chloride (PVDC), polyethylene terephthalate (PET), polypropylene (PP), paper, aluminum foil, etc. can be used as the outer surface layer 3. When used as a pouch, aluminum foil, EVOH, PVDC
And the like, and a stretched PET film, a stretched nylon film, or the like can be used as the outer surface layer 3.

The intermediate layer 2 may be omitted, or the intermediate layer 2 may be a laminate of two or more, depending on the purpose of use.

Next, a specific example in which the packaging material of the present invention is used as a cover material for a container for retort sterilization will be described.

In addition, the container for retort sterilization used polyethylene terephthalate, and the lid material used what laminated | stacked the polyester resin of the composition shown in following Table 1 (50 micrometers in thickness) on the inner surface of the biaxially stretched PET (25 micrometers in thickness) sheet.

The heat sealing conditions were 200 ° C., a pressure of 1 kg / cm ² , and 1 second.

In the above example, retort sterilization was performed at 120 ° C. for 30 minutes.

Further, the amount of limonene adsorbed is such that the drinking water containing limonene is sealed in the container, and the lid is brought into contact with the lid for 170 hours or more.Then, the drinking water is taken out, and the limonene adsorbed in the lid is quantitatively ethyl acetate. And limonene in the solution was measured by gas chromatography.

The results are also shown in Table 1. The solubility parameter (SP value) is also shown as one scale for evaluating this adsorption. This SP value is a numerical value indicating the ease of dissolution when dissolving a plastic material in a volatile solvent, and the closer the SP value of the plastic material and the SP value of the solvent are, the easier it is to dissolve. growing. The SP value is generally calculated from the latent heat of vaporization of the polymer substance and the solvent, the heat of vaporization, and the like.

As is clear from the results in Table 1, if the melting point of the polyester resin inner layer is not lower than 120 ° C. or not amorphous, a part of the inner layer is melted during retort sterilization, and the lid material is deformed. Also, as the diol component, butanediol alone extremely reduces the seal strength after retort sterilization, but the use of ethylene glycol alone or a mixture of 10 mol% or more of ethylene glycol and butanediol suppresses the decrease in seal strength. be able to.

[Effects of the Invention] As described in detail above, the packaging material of the present invention has a very small decrease in seal strength before and after retort sterilization, and has no risk of deformation after retort sterilization. Further, the content of the active ingredient such as a flavoring agent in the content is extremely low, and thus it is particularly useful as a packaging material for foods and other contents requiring heat sterilization.

[Brief description of the drawings]

 The drawing is a sectional view showing an example of the packaging material of the present invention. 1 ... inner layer, 2 ... intermediate layer, 3 ... outer layer.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-55-166248 (JP, A) JP-A-63-15745 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00-35/00 B65D 65/40

Claims (2)

(57) [Claims] 1. A polyester resin comprising at least two moles of terephthalic acid as an acid component constituting a polyester and at least 10 mol of ethylene glycol as a diol component and having a melting point of 120 to 130 ° C. A heat-sealable packaging material having heat resistance provided at least as an inner surface layer. 2. An polyester component comprising two or more acids mainly composed of terephthalic acid as an acid component and at least 10 mol of ethylene glycol as a diol component, and an amorphous polyester resin as at least an inner surface layer. Provided heat-sealable packaging material with heat resistance.