JP2013075718A - Easily-openable lid material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an easily-openable lid material having constant seal strength or more and having good openability.SOLUTION: An easily-openable lid material of a multilayer structure functionally separated into a sheet layer 3 bearing heat sealing with a cup container 6 and a cohesive failure layer 2 bearing easy-openability by cohesive failure, wherein foam particles 4 are included in the cohesive failure layer 2 bearing the easy-openability by the cohesive failure.

Description

  The present invention relates to a lid member that seals a container by heat sealing, and particularly relates to a lid member that has easy-openability.

  Generally used as a lid for cup containers such as dessert cups such as yogurt and pudding, small cup containers such as coffee milk and syrup, and trays and cup containers for cooked foods called potion packs. A film sheet made of a material and a sealing material is used.

  The main functions required for such a lid member are a hermetic sealing property that prevents the contents from leaking and an easy-opening property that can be easily opened by a person. Moreover, oxygen barrier property, heat resistance, etc. may be calculated | required depending on the kind of contents, the expiration date of goods, a sterilization method, and a distribution means.

  In general, there are mainly two types of sealing materials used for easy-opening lid materials: delamination type and cohesive peeling type. The delamination type consists of a seal layer, a holding layer, and a base material. The seal layer is made of the same kind of resin as the adherend, so that it can be firmly heat-sealed with the adherend to maintain a strong seal. The holding layer is formed of a resin different from that of the seal layer, so that it can be easily peeled between the seal layer and the holding layer to provide easy opening (see, for example, Patent Document 1).

  However, in the case of the delamination type, the delamination strength between the layers is smaller than that of the cohesive delamination, so that not only the sealed portion but also the non-sealed portion is delaminated between the layers, causing the so-called film residual phenomenon and the lid material It is easy to happen that can not be opened well.

  On the other hand, the cohesive peeling type has the same structure of the sealing layer, the holding layer, and the base material, but the sealing layer is formed of a polymer blend of two kinds of resins, the same kind of resin as the adherend and the same kind of resin as the holding layer. Yes. Thereby, at the time of heat sealing, the sealing layer is partially heat-sealed with the adherend, and at the time of peeling, the sealing layer is peeled off while cohesively destroying the sealing layer itself at the interface of the polymer blended resin. Therefore, the sealing layer has both a sealing function and a peelability function. However, since the thermal fusion between the sealing layer and the adherend is partial, it is impossible to obtain a certain level of sealing strength. There is a point.

JP 2009-7034 A

  In the conventional easy-opening lid material, among the easy-opening sealants, there are problems of peeling such as film residue due to weak peeling strength between layers, which is a problem of delamination type, and problems of cohesive peeling type There is a problem in that there is a limit to the seal strength due to partial heat fusion between the seal layer and the adherend.

  The present invention has been made in view of the above circumstances, has a sealing strength of a certain level or more, and also has an easy-opening property, is less likely to cause problems at the time of opening such as a film residue, and is easily opened for cup containers. The object is to provide a lid.

The present invention has been made to solve the above-described problems, and the invention according to claim 1
Among lid materials that have both heat-sealing properties for sealing containers and easy-opening properties for peeling lid materials from containers, it functions as a layer responsible for heat-sealing with containers and a layer responsible for easy-opening properties due to cohesive failure An easily openable lid material having a separated multi-layer structure, wherein the layer responsible for easy opening by cohesive failure includes foamed particles.

  The invention according to claim 2 is characterized in that the layer responsible for easy opening including foamed particles is composed of the same resin component as the sealing layer, and is provided between the base material and the sealing layer. It is a lid.

  In the invention according to claim 3, the foaming start temperature of the foamed particles is lower than the heating temperature when heat-sealing the lid material, but is higher than the temperature required in the step of forming the resin layer containing the foamed particles. It is an easily openable lid material characterized in that it does not foam in the positive formation of the resin layer to be contained but foams by heating when the lid material is heat-sealed.

  The invention according to claim 4 is an easily openable lid material characterized in that the foaming start temperature of the foamed particles is 120 ° C to 150 ° C.

  The invention according to claim 5 is characterized in that, by heat-sealing the lid material on the container, only the heat-sealed portion makes the layer responsible for easy-opening including foamed particles porous. It is.

  According to the said structure, since the layer which bears easy opening contains a foamed particle, when it heats more than the foaming temperature of a foamed particle, the said layer will become porous by the foaming. At this time, by setting the resin component constituting the layer containing the expanded particles as the same resin component as that of the seal layer, the temperature at the time of heat sealing becomes equal to or higher than the melting point of the resin. The resin of the layer is also in a molten state, and the expanded particles are easily expanded. Of course, this heat sealing temperature needs to be higher than the foaming temperature of the foamed particles.

  In addition, since the resin component of the layer containing the expanded particles and the sealing layer are the same, both layers are melted during heat sealing, and the interface is firmly fused. Prevents light peeling.

  Thus, when the layer containing foamed particles is made porous at the time of heat sealing, the layer easily breaks and breaks down, and the layer becomes an agglomerated release layer when the cover material is peeled off. Further, since only the heat-sealed portion can be made porous, it is possible to form an agglomerated release layer only on the heat-sealed portion. For example, by using a sealing mold that heats only the flange portion of the cup container in a ring shape, heat sealing can form an agglomerated release layer in the ring shape only on the flange portion, and the portion of the lid material to be peeled off Since only the flocculent peeling is selectively performed, it is possible to prevent the occurrence of peeling failure such as a film residue.

It is sectional drawing which showed the principal part in order to demonstrate the layer structure of the easy-open lid | cover material which concerns on this invention. FIG. 2 is a cross-sectional view showing a porous state in which foamed particles in the cohesive failure layer in FIG. 1 are foamed by heating to generate voids. 1 shows steps (a) to (b) for sealing the easily openable lid material of FIG. 1 onto a cup container, and FIG. 2 (c) shows a seal portion in a state of being heat-sealed in a ring shape corresponding to the flange 8 of the container. FIG. FIG. 4 is a cross-sectional view showing a cross section in the vicinity of the flange in FIG. 3 (c), and showing a state in which a void is generated in the cohesive failure layer by heat sealing at the flange portion to create a cavity. FIG. 5 is a cross-sectional view showing a peeled surface when the lid material is opened in a state where the flange portion in FIG.

  The easy-open lid | cover material which concerns on embodiment of this invention is demonstrated in detail with reference to drawings.

  FIG. 1 shows a layer structure of an easy-open lid according to an embodiment of the present invention. A cohesive failure layer 2 and a seal layer 3 are laminated on a base material 1 in this order. And in this cohesive failure layer 2, the foamed particle 4 is mixed and the cover material 7 is formed (refer FIG. 3). The foamed particles 4 in the cohesive failure layer 2 are foamed by heating as shown in FIG.

  Here, for example, as shown in FIG. 3, when the lid is heat-sealed to the ring-shaped flange 8 on the opening side of the container 6 such as a cup container, a seal portion 9 is formed. When the lid 7 is heat-sealed to the flange 8 of the container 6, when the lid 7 is heat-sealed to the flange 8 of the container 6 in the cohesive failure layer 2, the cavity 5 is generated and becomes porous. (See FIG. 4). Thereby, when the lid body 7 is opened, the porous portion where the cavity 5 is formed becomes the peeling surface 10 to prevent peeling.

  Here, as the base material 1 constituting the easy-open lid according to the present invention, aluminum foil, paper, stretched polyester film, stretched nylon film, stretched polypropylene film, polystyrene film, silica vapor-deposited stretched polyester film, aluminum vapor-deposited stretch Any material that is generally used as a base film of a soft packaging material such as a polyester film or other barrier film can be applied, and an optimal base material 1 can be selected and used as appropriate depending on the contents and use.

  For the cohesive failure layer 2 and the seal layer 3, thermoplastic resins such as polyethylene, polypropylene, polyester, polystyrene, polyvinyl acetate, acrylic resins, urethane resins and the like can be used. The resin needs to be the same as the resin of the adherend part of the container, and in general, polyethylene and polypropylene are often used. Further, in order to improve the adhesion between the cohesive failure layer 2 and the seal layer 3, it is desirable to use resins of the same system for both layers.

  Furthermore, the resin used for the cohesive failure layer 2 is desirably a resin having a melting point equal to or lower than the foaming start temperature of the foamed particles 4 included in the layer. This is because when the foamed particles 4 are foamed, the foaming efficiency is better when the surrounding resin is melted.

  Since the foamed particles 4 included in the cohesive failure layer 2 are desirably foamed when the lid member 7 is heat-sealed, it is necessary to use those having a foaming start temperature lower than the heat-sealing temperature. However, in order not to foam at the time of forming the cohesive failure layer 2, the foaming start temperature must be higher than the temperature applied when the layer is formed. For example, when the cohesive failure layer 2 is formed by application of a resin dispersion and heat drying, it is necessary to select foamed particles 4 having a foaming start temperature higher than the heat drying temperature.

  The method of forming the cohesive failure layer 2 and the seal layer 3 needs to be formed by applying a coating liquid such as a heat seal lacquer instead of the extrusion lamination of resin. This is because in resin extrusion laminating, it is necessary to raise the resin temperature to near 300 ° C. even for resins such as polyethylene and polypropylene, but foamed fine particles having a foaming start temperature higher than 300 ° C. are not currently available on the market. . Therefore, it is desirable to form these layers by applying an organic solvent-based coating liquid containing polyethylene or polypropylene as a resin component by gravure printing or the like, and forming a film at a drying temperature of 80 ° C. to 100 ° C.

  From the above, the desirable configuration of the easy-open lid according to the present invention is that the stretched polyester film, silica vapor-deposited stretched polyester film, nylon film or aluminum foil, or a laminated film of these appropriately selected according to the application is used as the base material 1. Then, a coating liquid containing polyethylene or polypropylene in which foamed particles 4 having a foaming start temperature of 130 ° C. to 150 ° C. are dispersed as a resin component is applied to form a cohesive failure layer 2 having a thickness of 5 μm to 10 μm. The coating liquid of the resin component of the same system as the cohesive failure layer 2 is applied thereon to form a heat seal layer with a thickness of 10 μm to 20 μm.

  Next, Examples 1-1, 1-2, Example 2, and Example 3 based on one embodiment of the present invention will be described in detail, which are exemplary, The present invention is not limited at all.

  Using a 12 μm-thick silica-deposited stretched polyester film as a base material 1, 25 weight percent of foamed particles 4 is added to a heat seal lacquer composed of a polypropylene resin component and an organic solvent, and a film is formed by gravure printing. The cohesive failure layer 2 is formed by coating to a thickness of 10 μm, and further the same heat seal lacquer is applied to the thickness of 10 μm without adding the foamed particles 4 to form a seal layer. An easy-open lid was prepared.

  The drying temperature after application of the cohesive failure layer 2 and the seal layer 3 was 100 ° C. The foamed particles 4 added to the cohesive failure layer 2 were foamed particles 4 having a foaming start temperature of 130 ° C., a shell component of acrylonitrile, and a core component of low-boiling hydrocarbons.

  An easy-open lid was prepared in the same manner as in Example 1 except that the foamed particles 4 having a foaming start temperature of 100 ° C. were used.

  An easy-open lid was prepared in the same manner as in Example 1 except that the foamed particles 4 having a foaming start temperature of 170 ° C. were used.

  Examples 1 to 3 were evaluated as follows. The cap material 6 made of polypropylene having the flange 8 was filled with water, and the lid 7 was sealed by heat sealing at a sealing temperature of 160 ° C. Sealability and openability were evaluated using the cup container 6 with the lid material sealed. The sealability is evaluated by applying a 40 kg load to the lid 7 for 1 minute, and then evaluating whether or not there is a liquid leak from the seal portion. The evaluation of the unsealing property is not easy to open or abnormally open when manually opened. Evaluated.

In Example 1, only the flange portion is heated in a ring shape and sealed in two ways: a heat sealing method (Example 1-1) and a method of heating and sealing the front surface of the lid material (Example 1-2). In Examples 2 and 3, only the flange portion was heated in a ring shape and sealed only by the heat sealing method. The result is

Shown in

  That is, in the case of Example 1, what heated only the flange part became porous by foaming only the part corresponding to the flange 8 of the cohesive failure layer 2, and both the sealing property and the unsealing property were favorable.

  In the case of Example 1, when the entire surface was heated, the cohesive failure layer 2 on the entire surface of the lid material was made porous by foaming, and peeled off at the cohesive failure layer portion over the entire surface of the cover material when the cover material was opened. The film remaining phenomenon of layer 3 was observed, and the opening was poor.

  In the case of Example 2, since the foaming start temperature of the foamed particles 4 was 100 ° C., foaming occurred over the entire surface at the drying temperature (100 ° C.) at the time of forming the cohesive release layer. Thereby, unevenness was generated on the surface of the cohesive failure layer, and unevenness was generated in the coating of the seal layer 3. For this reason, unevenness in heat sealing also occurred, resulting in partial sealing failure. Further, since the entire surface was foamed and made porous, a film residue at the time of opening was also generated.

  In the case of Example 3, since the foaming start temperature of the foamed particles 4 was 170 ° C., foaming did not occur at the heat seal temperature of 160 ° C., and the cohesive failure layer 2 was not made porous at all. Therefore, the peel strength at the time of opening the lid material was large, and it was difficult to open the lid.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention at the stage of implementation. Furthermore, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements.

  For example, even if some constituent elements are deleted from all the constituent elements shown in the embodiment, the problems described in the column of problems to be solved by the invention can be solved, and the effects described in the effects of the invention can be obtained. In some cases, a configuration from which this configuration requirement is deleted can be extracted as an invention.

  Since the easily openable lid material of the present invention includes foamed particles in the layer responsible for easy opening, when heated to a temperature higher than the foaming temperature of the foamed particles, the layer becomes porous due to the foaming. At this time, by setting the resin component constituting the layer containing the expanded particles as the same resin component as that of the seal layer, the temperature at the time of heat sealing becomes equal to or higher than the melting point of the resin. The resin of the layer is also in a molten state, and the expanded particles are easily expanded.

  In addition, since the resin component of the layer containing the expanded particles and the sealing layer are the same, both layers are melted during heat sealing, and the interface is firmly fused. Prevents light peeling.

  Thus, when the layer containing foamed particles is made porous at the time of heat sealing, the layer easily breaks and breaks down, and the layer becomes an agglomerated release layer when the cover material is peeled off. Further, since only the heat-sealed portion can be made porous, it is possible to form an agglomerated release layer only on the heat-sealed portion. For example, by using a sealing mold that heats only the flange portion of the cup container in a ring shape, heat sealing can form an agglomerated release layer in the ring shape only on the flange portion, and the portion of the lid material to be peeled off Since only the flocculent peeling is selectively performed, it is possible to prevent the occurrence of peeling failure such as a film residue.

DESCRIPTION OF SYMBOLS 1 ... Base material 2 ... Cohesive failure layer 3 ... Seal layer 4 ... Foamed particle 5 ... Cavity 6 ... Cup container 7 ... Cover material 8 ... Flange 9 ... Seal part 10 ... Release surface

Claims (5)

Easily has a multi-layer structure that separates the heat sealing property for sealing the container and the easy-opening property for peeling from the container, and is functionally separated into a layer responsible for thermal fusion with the container and a layer responsible for easy-opening property due to cohesive failure An openable lid material,
An easily openable lid material comprising foamed particles in a layer responsible for easy opening by cohesive failure.   The easily openable lid according to claim 1, wherein the layer responsible for easy opening including the foamed particles is composed of the same resin component as that of the sealing layer, and is provided between a base material and the sealing layer. Wood.   The foaming start temperature of the foamed particles is lower than the heating temperature at the time of heat sealing, but is higher than the temperature required in the step of forming the layer containing the foamed particles. The easy-opening lid material according to claim 1, wherein foaming is performed by heating when the heat sealing is performed.   The easy-open lid according to any one of claims 1 to 3, wherein a foaming start temperature of the foamed particles is 130 ° C to 150 ° C.   5. The layer according to claim 1, wherein the layer responsible for easy opening including the foamed particles is made porous only by heat sealing to the container. Openable lid.

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