WO2000000400A1 - Composite container - Google Patents

Abstract

A composite pressure container which can be used as a food can and a beverage can without using environment polluting materials, comprising a metal lid formed of a metal sheet coated on the inner side thereof with polypropylene or polyester and a container body constituted on the inner surface thereof of polypropylene or polyester, both members joined together by high frequency welding.

Description

 Specification

 Title of invention

 Composite container technical field

 The present invention relates to a container used for a beverage can or a food can to which a partial open lid / a full-open lid is joined. Landscape technology

 It is well known that conventional metal cans for beverages and food cans have a metal body with a metal cover double-wrapped through a compound to ensure hermeticity. Thermosetting resin paint such as polyepoxyphenol has been coated on the inner surface to prevent the metal odor from migrating to the contents and to prevent metal corrosion due to the contents. . Thermosetting resin paints such as polyepoxyphenol are applied by heating at 150 to 250 ° C for several minutes, but unreacted or low reacting substances such as residual solvents and substances used as raw materials are used. Low molecular weight components such as hardeners and plasticizers used as high molecular weight substances and additives migrate to the contents of metal cans, impairing the original taste and aroma of foods and beverages, or being called environmental hormones It has been pointed out that unreacted substances of bisphenol A, which is a raw material of polyepoxyphenol, are eluted, which is undesirable for food safety and health.

In recent years, laminated metal plates such as PET / iron plate, PET / aluminum plate, PP / iron plate, PP / aluminum plate have been developed as alternatives to the inner paint of metal cans. 61-149340, JP-A-63-111048, JP-A-63-111049, JP-A-6-320669, and Patent No. 2515581). Such laminated metal plates are drawn to form a two-piece can body, welded to form a three-bead can body, and a metal lid is manufactured (Japanese Patent Application Laid-Open No. HEI 9-258572). 7-331196). Such a laminated metal body and a laminated metal lid were joined by double winding, and at that time, a compound was interposed at the joint. In this case, since the polymer is laminated, there is no problem of incense transfer from the body and lid to the content food and safety and health problems. I However, since the compound is still used in the double-winding portion, residual organic solvent of the compound, low-molecular-weight components of the compound, and low-molecular-weight components of additives such as plasticizers migrate to the contents. However, the problem of incense as a whole and health and safety issues has not been solved.

 It is also known that the joining surface of the metal lid is coated with a thermoplastic polymer and joined to the metal body by high-frequency heating (Japanese Patent Laid-Open No. 254545), but the entire metal container is used for food containers. It is considered that normal paint is applied, and no consideration is given to environmental issues.

 Therefore, in order to solve the problems in the prior art as described above, the present invention is intended to be used as a food can or a beverage can without using environmentally harmful materials such as epoxy phenol resin and compound. The purpose is to provide a pressure-resistant container that can be used. BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is a cross-sectional view of a laminated metal steel sheet according to the present invention, FIG. 2 is a cross-sectional view of a laminated metal cover according to the present invention, and FIG. FIG. 4 is an enlarged view, FIG. 4 is a sectional view of a container body according to the present invention, and FIGS. 5 and 6 are enlarged partial views of the container body. Disclosure of the invention

 In the composite container according to the present invention, a metal lid made of a metal plate whose inner surface is coated with polypropylene or polyester, and a container body whose inner surface is made of polypropylene or polyester are joined by high-frequency heating, respectively. (Material)

FIG. 1 shows a laminated metal steel sheet as an example of the material used in the present invention. The laminated steel sheet is provided with an outer coating layer, a PP / modified PP layer, or a PET / adhesive resin layer 1 on the outer surface side of an iron plate or an aluminum plate 2. In addition, the inner surface of the iron plate or aluminum plate 2 is made of PP or PET through the adhesive resin layer 3. A coating layer 4 is provided.

 In the present invention, the joint surface between the lid and the container body and the inner surface of the container in contact with the contents of the can are made of polypropylene (sometimes abbreviated as PP) or polyester. This makes it possible to perform thermal bonding by high-frequency heating, and there is no elution of harmful components when in contact with foods. To obtain strong welding by high-frequency heating, both the lid and the body surface must be made of polypropylene or polyester.

 As the polypropylene used in the present invention, a copolymer with ethylene or the like may be used in addition to a usual propylene copolymer for molding. Lamination of polypropylene on a metal lid or a body can be performed by a known technique, but usually, PP / modified PP (modified PP includes a maleic anhydride graft copolymer or the like). It can be obtained by heat welding the release film to a metal plate. The use of the modified PP ensures the adhesion between the metal surface and the polymer layer.

 As the polyester used in the present invention, polyethylene terephthalate (hereinafter sometimes abbreviated as PET) and a copolymer mainly composed of ethylene terephthalate repeating units are preferable. The method of laminating the polyester on the metal surface can be performed by a known technique. One of the methods is a method of heating a metal surface and thermally welding a PET laminating film thereon, as disclosed in Japanese Patent Application Laid-Open No. 7-90094. Another method is to apply an adhesive polymer having an affinity for metal and polyester to one side of a polyethylene terephthalate film, and form a polyester surface on the metal surface via the adhesive polymer layer. It is. As a laminating method using such an adhesive polymer, it is preferable to use a method disclosed in Japanese Patent No. 2515581 or the like.

 As the metal forming the container lid or body used in the present invention, a metal such as an iron plate or an aluminum plate, which is usually used as a container material, is used. In laminating the polymer, a known pretreatment is performed. be able to.

(Lid)

The lid is used to ensure the required pressure resistance for long-term storage of food or beverage cans A metal plate (usually 0.10 to 0.40 mm in thickness, preferably 0.15 to 0.30 mm), and at least the joint surface with the body and the inner surface forming the container are made of polypropylene or Polyester is laminated.

 The lid must have a plastic film of the same type as the fuselage attached to the inner surface that comes into contact with the fuselage.If the plastic material constituting the fuselage is PP, the PP film is Is laminated with PET film. The outer surface of the lid may be laminated with the same plastic film as the inner surface or coated with paint for prevention. Preferred constitutions include PP / modified PP / metal / modified PP / PP, PET / adhesive layer / metal / adhesive layer / PET, PET / metal / PET. The thickness of the film of the laminate layer is from 10 to 200 zm, preferably from 20 to 70 m.

 The laminated metal plate made in this way is added to a normal metal lid by a mold. In this case, the flange formed on the entire circumference of the metal lid is heat-welded with the flange of the fuselage in the case of high-frequency heating only, so the flange shape of the fuselage is the same as that of the fuselage. Is preferably a flat shape. The flange width is more stable because it is heat-welded to the fuselage, but if it is too wide the appearance will be poor and if it is too narrow the stability of the heat welding will be poor. The flange width is usually lmm to 10mm, preferably 2mm to 7mm. When using in combination with winding, a shape suitable for normal double winding may be used. Furthermore, in order to obtain easy-opening if necessary, score-line is cut in the metal part so as not to damage the laminated PP or PET film, and a pull tab is attached to make a partial open or full open lid I can do it.

Fig. 2 shows an example of the lid. This lid portion is formed of a lid body 11 and a flange portion 13 formed on the entire periphery of the lid body 11. The lid main body 11 has a circular top plate portion 12, and a score line 16 is formed on the entire outer circumference of the top plate portion 12. Further, on one side of the top plate section 12, a pull-up pad 15 for opening is provided. The above-mentioned flange width is a portion indicated by reference numeral 14 in FIG. 2, that is, a heat-welded portion to the body. (body)

 Since the fuselage is welded to the lid and these joints are formed on the inner surface of the fuselage, at least the joints on the inner surface of the fuselage are made of the same type of plastic material as the film bonded to the lid. It is necessary. If the film laminated on the lid is PP, a body made of PP material is used, and if the film laminated on the lid is PET, the PET material is used. Is used.

 The fuselage may be a single layer of a plastic material or a multi-layer substrate combined with a barrier substrate that is impermeable to oxygen and water vapor. In the case of a single layer, if the plastic film laminated on the lid is PP, an injection-molded product of PP, a vacuum-pressure molded product, or a blow-molded product is used. Similarly, in the case of a single layer, when the film laminated on the lid is PET, an injection molded product of PET, a vacuum-pressure molded product, or a biaxially stretched molded product is used. In particular, in the case of a biaxially stretched product of a PET laminated metal lid and PET, the lid and the body can be used as a pressure-resistant container for carbonated beverages, beer, etc. by forming a pressure-resistant structure respectively.

 If the fuselage has a multilayer structure, the same type of plastic as the film laminated on the lid is used on the inner side of the container that comes into contact with the lid because it is bonded and bonded to the lid. It is necessary. If the film laminated on the lid is PP, use PP; if PET, use PET.

As a body having such a multilayer structure, a body for a two-piece can obtained by squeezing a laminated metal plate similar to the lid portion or a body for a three-piece can obtained by welding is used. In addition, a laminate film of PP / barrier base material / PP or PET / barrier base material / PET is inserted into an injection mold, and a multi-layered body is made by insert molding. The barrier one substrate used therefor, a metal foil such. A1 foil Ya iron foil, a film with a deposit of S IOx and A 1 ₂ 0 ₃ in PET, EVO H or PVDC, PAN, films of NY resin mentioned Can be Further, a multi-layered body may be made by vacuum / pressure forming a sheet having a PP / barrier single base / PP or a PET / barrier single base / PET configuration. In this case, the barrier base material is made of E VOH, P VDC, PAN, or NY resin, which can follow the elongation of body forming by vacuum pressure forming. Can be. Further, a body having a PP / barrier-substrate / PP configuration may be formed by blow molding. Furthermore, a parison having a PET / barrier base material / PET configuration is made, and the parison is set in a blow mold and blow-molded, thereby producing a biaxially stretched product. In particular, a combination of a laminated metal lid and a laminated metal barrel, or a PET laminated metal lid and a biaxially stretched product can be used as a pressure-resistant container for carbonated beverages and beer by forming the lid and the body in a pressure-resistant structure. Since the fuselage only welds to the lid, it must have a shape that matches the flange of the lid. The flange width is also limited by the flange width of the lid when only high-frequency heating is used, and a width 1 mm narrower than the flange width of the lid is usually preferable. When using together with winding, it is necessary to make the mouth shape suitable for winding, and like the mouth of a regular metal can, the shape that is thinly spread out along the flange shape of the lid Good.

 Figure 4 shows an example of the fuselage. Examples of the flange portion 20a of the body 20 shown in FIG. 4 are shown in FIGS. 5 and 6 in an enlarged manner.

 The body 20 has a main body 2Ob, and a flange 20a formed so as to protrude outward around the entire outer peripheral portion which is an opening end face of the main body 20b. . The body 20 is a two-bead can obtained by drawing the same laminated metal plate as the lid, and as shown in an enlarged view in FIG. And PP 23 are laminated. The flange portion 2 Ob may have a configuration as shown in FIG. 5 or a configuration as shown in FIG. In the example of the flange portion shown in FIG. 6, the tip portion is wrapped inward to prevent the iron plate from flowing out of the flange end surface.

(Joint)

 Means for applying heat include radiant heating, hot plate heating, ultrasonic heating, and high frequency heating.

However, radiation does not provide enough heat. In the hot plate method, since the metal lid is thick, it takes time to transfer heat to the contact interface between the lid and the body to be welded. Further, in ultrasonic heating, it is necessary to accurately fix the body and the lid to the jig, and furthermore, it is necessary to prevent the horn from separating from the joint surface, but it is difficult to do so. This is not preferable as a means for applying heat.

 On the other hand, high-frequency heating is optimal because it induces heat in the lid metal plate by means of a high-frequency magnetic field, so that heat can be directly transmitted to the laminated plastic in contact with the body. In addition, in order to improve the appearance of the joint and increase the stability of the joint, it is possible to supplementally lightly wind the joint.

 Welding of the lid and fuselage is performed as follows. That is, the metal plate is heated by the Joule loss of the eddy current generated in the metal plate of the lid, and the laminated plastic and the same kind of plastic as the body are melted. Welding. Example

 (Example 1)

 Nominal diameter using a laminated metal plate composed of PP (48 JL) / modified PP (2 変 性) Z iron plate (200 μ.) / Modified PP (2〃) / PP (28〃) Was produced. The width of the flange was 5 mm, and the score was lined up and a pull tab was attached to form a fully open lid. From the inner surface of the fuselage, draw-forming and forming using a metal plate composed of PP (48〃) / modified PP (2j) / iron plate (200〃) / modified PP (2Λ / PP (28〃), nominal diameter # 401 A flange was provided at the opening and the flange width was set to 4 mm.The body was filled with 250 ml of distilled water, fitted with a lid, and covered with a high-frequency heating welding machine. The container filled with the distilled water was placed in a retort pot, and subjected to hot water retort sterilization at 125 ° C for 40 minutes, and the F value at this time was 38.

On the other hand, the body and bottom lid are formed from an iron plate with a thickness of 0.23 mm and the inside of which is coated with epoxy phenol, which is used for ordinary metal cans, and these are double-wound using a compound. To form a container body, which was filled with 250 ml of distilled water. On this body, a container was formed by double-tightening a full-open lid of epoxy phenol inner surface coating on the A1 plate via a compound to form a container, which was used as a comparative sample. This was stored in a retort pot and subjected to hot water retort sterilization at 125 ° C for 40 minutes. F at this time. The value was 40. The various samples obtained in this way were tasted for the content of distilled water by 22 panelists, and the transfer of off-flavors and offensive odors from the container to the content of distilled water was organoleptically evaluated. Further, in order to compare the elution amount from the container, the ultraviolet absorbance of distilled water and distilled water were evaporated to dryness, and the evaporation residue was measured. Further, the evaporation residue was identified by a gas chromatograph mass spectrometer. The results are shown in Tables 1, 2, 3, and 4.

【table 1】

 1; significance level at 1% risk

 twenty five % 〃

 Fill the cup with distilled water after retort and blindfold test according to each item

[Table 2] UV absorbance

Measure distilled water after retort with a cell length of 1 cm [Table 3] Evaporation residue of distilled water

Distilled water after retort was evaporated to dryness at the mouth of the evaporator and dried to dryness at 105 ° C for 4 hours. The residue obtained was converted to the unit of mg / m ² from the surface area of the container.

[Table 4] Identification of evaporation residue

Table 1 shows that there is a significant difference between the 1% risk factor and the 5% risk factor for each item, indicating that the product of the present invention has little transfer of off-flavor and odor to distilled water. It can be seen that an unusual flavor is occurring.

Table 2 shows that the magnitude of the absorbance is a measure of the size of the organic matter eluted in distilled water, indicating how much of the eluted material has dissolved in the conventional metal can. From Table-3, the amount eluted was confirmed as an actual residue. Again, it can be seen that a large amount of eluted material has been dissolved in the conventional metal can. Table 4 shows a summary of what kind of eluate was found. The eluate from conventional metal cans is mainly bisphenol A, which is said to be an environmental hormone, which is not desirable for food safety and health.

 (Example 2)

 A metal lid with a nominal diameter of # 211 was manufactured using a laminated metal plate with a PET (30) / iron plate (200 /) / Ρ Τ (30) configuration from the inner side as a lid. A single-layer bottle of biaxially-stretched PET with a diameter of 80 mm and a height of 120 mm was prepared as the body, with the shape of a metal lid for tightening and a scored line and a pull tab attached to form a partial open lid. The shape was adapted to the shape of the metal cover for tightening, and the bottom was a pressure-resistant structure of inverted dome type.

This body was filled with water, the above-mentioned lid was fitted, and lightly tightened with a seamer for metal cans.Then, the lid and the body were welded with a high-frequency heating welding machine, as shown in Fig. 3. A sample having a joint was prepared. A hole was made in the lid of this sample, and water was injected with a water pressure pump to check the joint strength between the lid and the body. However, even at a water pressure of 1 O kg / cm ² , the joint did not peel off.

On the other hand, commercial beer is 0-5. After cooling to C, the mixture was gently poured into the body, the lid was fitted, and the lid and the body were welded with a high-frequency heating welding machine to produce a beer sealed sample. The sample was left at room temperature for one month, and no abnormality was recognized without any peeling of the joint. The pressure of the beer at this time was ^2.5 kg / cm ² at room temperature.

 [Action and effect]

A metal lid laminated with PP or PET is heat-sealed by high-frequency heating to a multi-layer fuselage whose surface is made of the same plastic material as the lid or a single-layer fuselage made of the same plastic material as the lid. Is manufactured. Here, (1) Bisphenol A, which is called an environmental hormone, is not eluted because polyepoxyphenol paint is not used, and (2) Residual organic compounds from the compound are not used because double-tightening compound is not used. There is no problem of elution of solvents and low molecular weight components, etc. (3) There is little transfer of off-flavor and odor to the contents, without impairing the taste and aroma inherent in foods. A container preferable for food safety and hygiene can be provided. When joining is performed by using both high-frequency heating and double winding, the most stable joint without pinholes and slow leaks is formed, following the deformation of the flange when falling. . Also as a torso,

If a pressure-resistant body such as a biaxially stretched bottle is used, a container for carbonated beverages can be provided.

Claims

The scope of the claims 1. A composite container in which a metal lid made of a metal plate whose inner surface is coated with polypropylene or polyester and a container body whose inner surface is made of polypropylene or polyester are joined by high frequency welding.  2. A polypropylene film is coated on the inner surfaces of the metal lid and the container body,  The coating layer of the polypropylene film is obtained by heat-welding a co-extruded film composed of PP and modified PP to a metal plate, The composite container according to claim 1.  3. Polyester film is coated on the metal lid and the inner surface of the container body,  The coating layer of the polyester film is obtained by heating a metal surface and heat-welding a PET laminating film thereon. The composite container according to claim 1.  4. Polyester film is coated on the inner surface of the metal lid and the container body,  The coating layer of the polyester film is obtained by applying an adhesive polymer having an affinity for metal and polyester to one surface of a polyethylene terephthalate film, and coating the resultant through one layer of the adhesive polymer. The composite container according to claim 1.  5. The metal lid is formed of a metal plate having a thickness of 0.10 mm to 0.40 mm in order to secure necessary pressure resistance as a food or beverage can stored for a long time. The composite container according to claim 1.  6. The metal lid is formed of a metal plate having a thickness of 0.15 mm to 0.30 mm in order to secure necessary pressure resistance as a food or beverage can stored for a long time. A composite container according to claim 5. 7. The metal lid is made of the same material as the container body on the inner surface side in contact with the container body. 2. The composite container according to claim 1, wherein a plastic film made of a material is bonded. 8. The composite container according to claim 1, wherein the coating layer on the inner surface of the metal lid has a thickness of 10 / m to 200 zm.  9. The composite container according to claim 8, wherein the thickness of the coating layer on the inner surface of the metal lid is from 20 m to 70 / m.  10. The composite container according to claim 1, wherein a flange portion for joining the container body is formed around the entire outer peripheral portion of the metal lid, and the width of the flange portion is 1 mm to 10 mm.  1 1. A flange for joining the container body is formed all around the outer periphery of the metal lid, and the width of the flange is 2mn! The composite container according to claim 10, which has a diameter of 7 mm.  12. The entire circumference of the outer peripheral portion, which is the opening end surface of the container body, is wound around the flange portion of the metal lid, and after being tightened, the entire circumference of the container body and the flange portion of the metal lid are subjected to high-frequency welding. The composite container according to claim 10 or 11, which is fixed. 13. A flange portion to be joined to the flange portion of the metal cover is formed all around the outer peripheral portion of the container body, and the flange portion of the container body is formed to be lmm narrower than the flange width of the metal cover. The composite container according to claim 10, wherein:  14. The composite container according to claim 1, wherein a joint portion between the inner surface of the container body and the metal lid is made of the same kind of plastic material as a film coated on the inner surface of the metal lid.  15. The composite container according to claim 1, wherein the container body is formed of a molded product made of a single layer of a plastic material.  16. The composite container according to claim 1, wherein the container body includes a barrier base material and a coating layer made of pyrene or polyester provided on the barrier base material.  17. The composite container according to claim 16, wherein the coating layer of the container body is made of the same material as the coating layer on the inner surface of the metal lid.