JPH0262388B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an easily openable sealed container in which a container body made of polycarbonate or polyvinyl chloride resin is heat-sealed with a film or sheet-like lid. (Prior art and problems to be solved by the invention) Conventionally, the container body is made of synthetic resin such as polycarbonate, polyester, polyolefin, polyvinyl chloride resin, etc., and the opening is made of an easily openable lid material, such as polyethylene synthetic resin. BACKGROUND ART Containers sealed and heat-bonded using a film or sheet made of resin mixed with a heat adhesive are used as packaging containers for foods such as water lamb and curry. In conventional containers of this type that are sealed by thermally bonding a lid to a container body, the thermal bonding strength is unstable, and in some cases, the thermal bonding strength is so strong that it is difficult to open the container. In addition, in some cases, the heat bonding strength is so weak that the lid material peels off during the distribution process, making it difficult to seal with an appropriate heat bonding strength. In particular, there has been no lid material suitable for heat sealing a container body made of polycarbonate or polyvinyl chloride resin. As a result of various studies to solve these drawbacks, the present inventors found that a film or sheet formed from a composition containing a polyester resin with a low crystallinity and an appropriate amount of a polyolefin resin can be made from polycarbonate or polychloride. We have completed the present invention by discovering that it is extremely suitable as a lid material for heat-sealing containers made of vinyl resin, and an object of the present invention is to use it as a lid material for container bodies made of polycarbonate or polyvinyl chloride resin. An object of the present invention is to provide a film or sheet having useful easy-opening properties. (Means for Solving the Problems) That is, the present invention provides a container body made of polycarbonate resin or polyvinyl chloride resin made of 100 parts of polyester resin with a crystallinity of 40% or less and 5 to 50 parts of polyolefin resin. It is a sealed container that is heat-sealed with a film or sheet-like lid made of mixed resin. In the present invention, the polyester resin with a crystallinity of 40% or less (hereinafter referred to as a low-crystalline polyester resin) is, for example, a terephthalic acid ester resin such as polyethylene terephthalate or polybutylene terephthalate, or a third component added thereto. Refers to resins obtained by addition and condensation that have a crystallinity of 40% or less. Polyester resins with a crystallinity of 25% or less are preferably used. If a polyester resin with a crystallinity of 40% or more is used, it will not be possible to obtain a good quality film or sheet when blended with a polyolefin resin, and the polyester resin of the film or sheet after molding will deteriorate. Due to its high degree of crystallinity, thermal adhesion during sealing is not sufficient, making it unsuitable as a lid material for heat-sealing containers made of polycarbonate resin or polyvinyl chloride resin. However, such polyester resin with a crystallinity of 40% or less is produced by extruding the polyester resin and then rapidly cooling it to form pellets, and the crystallinity depends on the molecular weight distribution of the polyester resin, the temperature at the time of rapid cooling, This can be obtained by appropriately selecting the time and the like. In the present invention, 5 to 5 to 100 parts of polyolefin resin is added to 100 parts of this low-crystalline polyester resin.
The amount is 50 parts, preferably 15 to 35 parts. The film obtained by molding this mixed resin is different from polycarbonate resin or polyvinyl chloride resin.
Not only does it exhibit stable thermal bonding strength under normal thermal bonding conditions, but its value ranges from 0.8 to 0.8, which is optimal for lid materials.
It shows a peel strength of 2.6Kg/15mm. The polyolefin synthetic resin used in the present invention includes low density polyethylene, high density polyethylene,
Linear low-density polyethylene, ethylene-vinyl acetate copolymer ionomer, polymethylpentene, etc. may be used, but linear low-density polyethylene in particular has excellent oil resistance and can yield a soft film or sheet. preferable. In the present invention, a film or sheet is formed from a composition obtained by blending a polyolefin synthetic resin in a predetermined ratio with the above-mentioned low-crystalline polyester resin, and the molding method thereof is an extrusion molding method or an inflation molding method. A film or sheet having a thickness of about 5 to 1000 μm is formed by an appropriate molding method such as a molding method. When using this film or sheet as a lidding material, the film or sheet is thermally bonded to the opening of a container body made of polycarbonate or polyvinyl chloride resin. Alternatively, the film or sheet and paper or other synthetic resin film or sheet may be laminated and then the film or sheet side may be thermally bonded to the opening. In addition, as mentioned above, this film or sheet thermally bonded has appropriate peeling strength, so if a bag is constructed using this film or sheet, it should be an easy-to-open packaging bag. You can also do it. The present invention has a crystallinity of 40 as a polyester resin.
% or less is used as a raw material for forming the film or sheet of the lid material, and the reason for using one with a crystallinity of 40% or less will be explained below. First, 100 parts by weight of polyethylene phthalate resin (PET) of each degree of crystallinity shown in Table 1 below and 30 parts by weight of low-density polyethylene resin (PE) were mixed and extruded through a T-die at each melting temperature to an extrusion rate of 90 kg/ A film with a thickness of 25 μm was molded at hr. Cooling was performed using a cooling roll with a roll diameter of 800 mm and a temperature of 5°C. The condition of the molded film and the crystallinity of the film were as shown in Table 1.

[Table] As is clear from Table 1, when polyethylene phthalate resin with a crystallinity of 40% or more is used, it is necessary to raise the melting temperature during film forming, and in that case, the flow of the mixed polyethylene Too large to form a good quality film suitable for heat sealing. Furthermore, when the melting temperature during molding is high, the cooling time after molding becomes long, and as a result, the degree of crystallinity of polyethylene terephthalate in the film increases. When the degree of crystallinity of polyethylene terephthalate in this film increases, heat sealability decreases. Table 2 below shows this relationship. Films molded in the same manner as above with various blends of polyethylene terephthalate resin and low-density polyethylene resin were thermally bonded to polycarbonate resin (PC), and the thermal bonding strength at that time was measured. The results are shown in Table 2.

[Table] As shown in Table 2, polyester resins with a crystallinity of 40% or less have excellent thermal adhesion. Therefore, in the present invention, crystallinity of 40
% or less of polyester resin is used. Next, the present invention will be explained with examples. Example 1 A polycarbonate film with a thickness of 40μ (Iupilon manufactured by Mitsubishi Plastics Co., Ltd.) and a low-crystalline polyester resin (Kodar, PETG6763) with a degree of crystallinity of 10% were coated with linear low-density polyethylene (Moatec manufactured by Idemitsu Petrochemical Co., Ltd.).
0138H) in the proportions shown in Table 1, and was then thermally bonded to an easily openable film with a thickness of 25 μm at a thermal bonding temperature of 200° C. and a pressure of 2.0 Kg/cm ² for 1.0 seconds.
Table 3 shows the thermal adhesion strength between the thermally bonded laminated films.

[Table] The results show that the thermal adhesive strength of a film made only of low-crystalline polyester resin is higher than the optimum peel strength, and that the thermal adhesive strength of a film containing 50 parts or more of linear low-density polyethylene is higher than the optimum peel strength. It peeled off weakly. Example 2 An easily openable film with a thickness of 25μ obtained by mixing the same low-crystalline polyester resin and linear low-density polyethylene used in Example 1 in the proportions shown in Table 4. A polycarbonate film having a thickness of 40 μm, which is the same as that used in Example 1, was thermally bonded at a thermal bonding temperature of 160° C. and a pressure of 2.0 kg/cm ² for 1.0 seconds, and the thermal bonding strength is shown in Table 4.

[Table] In Examples 1 and 2, similar results were obtained for polyvinyl chloride film as for polycarbonate film. (Effects of the Invention) When heat sealing a container body made of polycarbonate resin or polyvinyl chloride resin with a film or sheet-like lid material, the present invention uses a polyester resin with a crystallization rate of 40% or less and a polyolefin resin as the lid material. A film or sheet molded from a mixed resin is used, and because the film or sheet is used, it is easy to open and can be sealed and thermally bonded without any problem of peeling during the distribution process. . Therefore, the sealed container of the present invention is extremely useful for food packaging and the like.

Claims (1)

[Claims] 1. A container body made of polycarbonate resin or polyvinyl chloride resin, 100 parts of polyester resin with a crystallinity of 40% or less and 5 parts of polyolefin resin.
A sealed container heat-sealed with a film or sheet-like lid material molded from a mixed resin with ~50 parts. 2. The sealed container according to claim 1, wherein the polyolefin resin is linear low density polyethylene.