JP2023173714A - Lid-body laminate sheet, lid body, food packaging container and food package - Google Patents

Abstract

To provide a lid body that has a high mass ratio of paper and attains both of openability and sealability.SOLUTION: A lid-body laminate sheet 10 used in a lid body of a food packaging container having a container body provided with an opening and a lid body covering the opening, includes a function layer 6 having waterproofness, a printed layer 5, a paper base material 4 and a heat-seal layer 1 in this order. The paper base material 4 has a mass greater than a mass of any other layer included in the lid-body laminate sheet 10. The heat-seal layer 1 has a peak strength of adhesive force measured by probe tack testing, lying in a range of -490 gf or greater and -20 gf or smaller or an integral value of adhesive force measured by probe tack testing, lying in a range of 5 gf seconds or greater and 180 gf seconds or smaller.SELECTED DRAWING: Figure 1

Description

The present invention relates to a laminated sheet for a lid, a lid, a food packaging container, and a packaged food.

In addition to changes in household composition and lifestyles due to the trend toward nuclear families in recent years, advances in distribution, freezing, and refrigeration technologies have led to an increase in the number of cooked and processed chilled foods sold at convenience stores and supermarkets. Demand is growing. At the same time, demand for packaging containers for chilled foods is also increasing.

The lids of food packaging containers, including chilled foods, are required to have a certain level of sealing strength to prevent the contents from deteriorating during storage and from peeling during transportation. However, as the sealing strength increases, the load applied to the lid increases, so problems such as destruction of the lid become more likely to occur when the lid is opened. Examples of defects include fuzzing, stringiness, paper peeling, and a portion of the lid material remaining in the container. If the problem is such that residue from the lid material blocks the opening of the container, it will be difficult to remove the contents. In addition, if some of the residue gets mixed into the contents, it is unfavorable from the standpoint of hygiene and quality stability. Furthermore, the appearance after peeling is poor, leading to a poor impression on the product using the packaging container.

BACKGROUND OF THE INVENTION A multilayer sealant film is known that is used as an easy-to-open lidding film, and has an easy-peel layer (cohesive failure layer) that is prone to cohesive failure. This multi-layered sealant film has a structure in which cohesive failure of the easy-peel layer occurs selectively when the lid is opened, making it less prone to fuzzing and stringing, making it suitable for applications that require relatively high sealing strength. used.

For example, Patent Document 1 discloses a film for a lidding material that includes a sealant film having a multilayer structure consisting of a heat-sealing layer and a cohesive failure layer introduced adjacent to the heat-sealing layer. The cohesive failure layer used here is a plastic layer containing as a main component a resin selected from propylene homopolymer, propylene-ethylene copolymer, and linear low-density polyethylene.

JP 2016-210063 Publication

In order to reduce the burden on the environment, paper, which has a low environmental burden and is a renewable resource, is increasingly being used in place of petroleum-based plastic materials. Demand for lid materials with a high paper mass ratio is also increasing for food packaging containers. In this case, by using paper as the base material and making the heat seal layer thinner by using a material that can be made into a thin film such as heat seal varnish, the mass ratio of paper in the lid material can be increased and the use of plastic can be avoided. It becomes possible to significantly reduce the amount.

The above technology disclosed in Patent Document 1 uses a sealant film with a multilayer structure including a cohesive failure layer made of plastic in order to realize an easy-to-open lidding film that does not cause stringiness or the like. . For this reason, depending on the technology, it is difficult to suppress fuzzing, stringiness, etc., and improve unsealability in a lid material having a high mass ratio of paper. The reality is that it is difficult to achieve both ease of opening and adhesion in a lid having such a high mass ratio of paper.

An object of the present invention is to provide a lid that has a high paper mass ratio and is both easy to open and seal.

According to the first aspect of the present invention, a laminated sheet for a lid according to any one of [1] to [11] below is provided.
[1] A laminated sheet for a lid used for the lid of a food packaging container comprising a container main body provided with an opening and a lid covering the opening, the sheet comprising a functional layer having water resistance and printing. layer, a paper base material, and a heat seal layer in this order, the mass of the paper base material is greater than the mass of any other layer included in the laminated sheet for lid, and the heat seal layer The peak strength of the adhesive force measured by the probe tack test is within the range of -490 gf or more and -20 gf or less, or the integrated value of the adhesive force measured by the probe tack test is 5 gf・sec or more and 180 gf・sec Laminated sheets for lids within the following range.

[2] The container according to [1], which includes a support layer between the paper base material and the heat-sealing layer, and the breaking strength of the support layer is greater than the heat-sealing strength between the lid and the container body. Laminated sheet for lid.

[3] The laminated sheet for a lid according to [1] or [2], which includes a gas barrier layer between the printing layer and the heat-sealing layer.

[4] The lid according to any one of [1] to [3], wherein the paper base material is coated paper having a coating layer on one side, and the printing layer is provided on the coating layer. Laminated sheet for body use.

[5] The laminated sheet for a lid body according to any one of [1] to [4], wherein the heat seal layer has a mass per area of 0.5 to 5.8 g/m ² .

[6] The heat-sealing layer according to any one of [1] to [5], wherein the heat-sealing layer contains one or more ethylene-vinyl acetate copolymers having a glass transition temperature in the range of 20°C or higher and 70°C or lower. Laminated sheet for lid.

[7] The laminated sheet for a lid body according to any one of [1] to [6], wherein the heat seal layer is a coating film derived from an aqueous emulsion or a heat seal varnish.

[8] An anchor coat layer is provided between the paper base material and the heat seal layer, and the anchor coat layer is disposed adjacent to the heat seal layer, and the anchor coat layer has a mass per area of 0.5 to 6. The laminated sheet for a lid according to any one of [1] to [7], which is within the range of 5 g/m ² .

[9] When the layers other than the paper base material included in the lid laminated sheet are classified into layers made of plastic and other layers, the mass of the paper base material is The laminated sheet for a lid according to any one of [1] to [8], which is larger than the total mass of the layers and the total mass of the other layers.

[10] The laminate sheet for a lid according to any one of [1] to [9], wherein the paper base material accounts for 60% or more by mass of the laminate sheet for a lid.

According to the second aspect of the present invention, the lid described in [11] below is provided.
[11] A lid made of the laminated sheet for a lid according to any one of [1] to [10].

According to the third aspect of the present invention, there is provided a food packaging container according to any one of [12] to [15] below.
[12] A food packaging container comprising a container main body provided with an opening and a lid according to [11] that covers the opening, wherein the support layer is comprised of the paper base material and the food packaging. A food packaging container that is placed between the container and the inner space of the container.

[13] The food packaging container according to [12], wherein the container body has a flange around the opening, and the lid is heat-sealed to the flange via the heat-sealing layer.

[14] The food packaging container according to [12] or [13], wherein the internal space of the food packaging container is filled with a mixed gas containing oxygen gas, nitrogen gas, and carbon dioxide gas.

[15] The food packaging container according to any one of [12] to [14], wherein the food packaging container is a chilled food packaging container or a frozen food packaging container.

According to the fourth aspect of the present invention, the packaged food described in [16] below is provided.
[16] A packaged food comprising the food packaging container according to any one of [12] to [15] and a food contained in the food packaging container.

ADVANTAGE OF THE INVENTION According to the present invention, a lid body having a high mass ratio of paper and achieving both openability and sealability is provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial cross-sectional view schematically showing an example of a laminated sheet for a lid according to a first embodiment of the present invention. FIG. 7 is a partial cross-sectional view schematically showing a laminated sheet for a lid according to a modified example. FIG. 7 is a partial cross-sectional view schematically showing a laminated sheet for a lid according to another modification. FIG. 3 is a cross-sectional view schematically showing a food packaging container according to a third embodiment of the present invention.

Embodiments of the present invention will be described below with reference to the drawings. The embodiments described below are more specific implementations of any of the above aspects. Note that elements having the same or similar functions are given the same reference numerals, and redundant explanations will be omitted.

[First embodiment]
FIG. 1 is a partial cross-sectional view schematically showing an example of a laminated sheet for a lid according to a first embodiment of the present invention.

The laminated sheet 10 for a lid shown in FIG. 1 is used as a lid in a food packaging container that includes a container body provided with an opening and a lid that covers the opening. That is, the laminated sheet for lid 10 is a lid material that itself is used as a lid, or a portion cut out from it is used as a lid.

The laminated sheet 10 for the lid includes a heat seal layer 1, a paper base material 4, a printed layer 5, and a functional layer 6 having water resistance (hereinafter also simply referred to as "functional layer 6") in this order. It includes. This laminated sheet 10 for a lid does not include a gas barrier layer, which will be described later, and is therefore suitable for applications that do not require high gas barrier properties. Each layer included in the lid laminated sheet 10 will be described below.

(Paper base material)
The lid laminated sheet 10 includes a paper base material 4. The mass of the paper base material 4 is larger than the mass of any other layer included in the lid laminated sheet 10. The ratio of the mass of the paper base material 4 to the mass of the laminated sheet 10 for lid body is preferably 40% or more, more preferably 45% or more, even more preferably 50% or more, and 50% or more. %, more preferably 60% or more. This mass ratio is 80% or less according to one example, 70% or less according to another example, and 65% or less according to still another example.

When the layers other than the paper base material 4 included in the lid laminated sheet 10 are classified into layers made of plastic and other layers, the mass of the paper base material 4 is equal to the total mass of the layers made of plastic and It is preferable that the mass is larger than the total mass of the other layers. In this case, in Japan, the lid laminated sheet 10 can be treated as paper under the Containers and Packaging Recycling Law.

The above classification is based on the "Containers and Packaging Recycling Law Explanatory Materials." That is, "plastic" is a material that contains a polymer as an essential component and is shaped and manufactured using fluidity during processing. Paints and adhesives are not included in plastics because they are unrelated to the concept of "forming." Therefore, in the example shown in FIG. 1, the heat seal layer 1 is a "layer made of plastic." In the example shown in FIG. 1, the printed layer 5 formed from ink, the functional layer 6 formed by coating, and the adhesive layer (not shown) formed from an adhesive are "other layers."

The basis weight, ie, the mass per area, of the paper substrate 4 is in the range of 20 to 500 g/m ² according to one example, and in the range of 40 to 100 g/m ² according to another example. If the basis weight of the paper base material 4 is increased, the lid will become harder and the opening performance will decrease. When the basis weight is reduced, the strength of the lid is reduced.

In addition, when the basis weight of the paper base material 4 is increased, the ratio of the mass of the paper base material 4 to the mass of the laminated sheet for lid 10 also increases. However, when the basis weight of the paper base material 4 is increased, the amount of carbon dioxide emitted during manufacturing of the paper base material 4 and disposal of the lid laminated sheet 10 increases.

The paper base material 4 is not particularly limited as long as it has plant-derived pulp as its main component. Examples of the paper base material 4 include coated paper such as high-quality paper, medium-quality paper, and slightly coated paper, single-gloss paper, and bleached and unbleached kraft paper (acidic paper or neutral paper).

The paper base material 4 is preferably coated paper having a coating layer on at least one surface. That is, it is preferable that the paper base material 4 is a single-sided coated paper or a double-sided coated paper. The surface of coated paper provided with a coating layer has excellent smoothness compared to the surface of paper not provided with a coating layer.

When the paper base material 4 is coated paper having a coat layer on one side, the printing layer 5 can be provided on the coat layer, for example. In this case, it is possible to suppress the printing ink and functional layer ink from penetrating into the paper fibers of the paper base material 4. Further, by providing the coat layer, it is easy to display a high quality image on the printing layer 5, and since the underlying surface of the functional layer 6 becomes smooth, the water resistance of the functional layer 6 is also improved.

The coat layer contains resin. Examples of the resin contained in the coating layer include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, and ethylene-α polymerized using a metallocene catalyst (single-site catalyst). -Olefin copolymer, polypropylene, ethylene-vinyl acetate copolymer, ionomer resin, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-propylene copolymer , methylpentene polymer, acid-modified polyolefin resins obtained by modifying polyolefin resins such as polyethylene and polypropylene with unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic anhydride, and fumaric acid, polyethylene terephthalate resins, and polybutylene terephthalate. Examples include thermoplastic resins such as resin, nylon resin, and styrene-butadiene rubber. These resins may be used in combination of two or more, or may be used by copolymerizing two or more. The coating layer may further contain additives, such as fillers such as clay, kaolin, calcium carbonate, talc, mica, and titanium oxide.

The thickness of the coating layer is preferably in the range of 0.5 to 50 μm, more preferably in the range of 1 to 15 μm.

(heat seal layer)
The heat-sealing layer 1 enables the lid 21 to be heat-sealed to the container body 22 of the food packaging container 20 shown in FIG. 4, which will be described later, and thereby has a heat-melting adhesive function for sealing the container. In addition, the heat seal layer 1 has a peak strength of adhesive force measured by a probe tack test in the range of -490 gf or more and -20 gf or less, or an integral value of adhesive force measured by a probe tack test is 5 gf.・It is within the range of 180 gf/second or more. If the peak strength or integral value of the adhesive force in the probe tack test is within the above range, when the lid 21 sealed with a predetermined strength in the food packaging container 20 is peeled off, the lid material may become fluffy or stringy. It is possible to suppress the occurrence of a problem in which a portion remains in the container body 22.

Here, the process of generating fluff and stringiness will be explained. When peeling off the lid 21 sealed with a predetermined strength in the food packaging container 20, the edge of the sealed surface of the flange 22a by the heat seal layer 1, that is, the portion sealed by the heat seal layer 1 and the portion not sealed. If the heat-sealing layer 1 does not break instantly near the boundary, fluffing and stringiness will occur. If the heat-sealing layer 1 does not break instantly, the breakage occurs after the heat-sealing layer 1 stretches into a film or thread between the lid body 21 and the sealing surface, and a part of the heat-seal layer 1 that has spread into a film or thread becomes part of the container body. It remains on the 22 side. Such problems of fuzzing and stringiness not only impair the appearance after peeling, but also may cause foreign matter to be mixed into the contents, which is undesirable from the standpoint of hygiene and quality stability. The peak strength of the adhesive force measured by the probe tack test in the heat seal layer 1 is within the range of -490 gf or more and -20 gf or less, or the integrated value of the adhesive force measured by the probe tack test is 5 gf/second or more. If it is within the range of 180 gf/sec or less, the heat seal layer 1 can break instantly even when the sealing strength is high, causing problems such as fuzzing and stringiness, where a part of the lid material remains on the container body 22. The occurrence of is suppressed.

The peak adhesive strength of the heat seal layer 1 in the probe tack test is determined by the resistance force when a probe is pressed against the main surface of the heat seal layer 1 of the laminated sheet for lid 10 and pulled up using probe tack under the conditions described below. Indicates the maximum value of (adhesive force). Note that since the peak intensity is a measured value, it is a negative value. The larger the absolute value of the peak intensity, the greater the adhesive force, and the smaller the absolute value of the peak intensity, the lower the adhesive force. The peak adhesive strength of the heat seal layer 1 measured by a probe tack test is preferably in the range of -480 gf or more and -20 gf or less, more preferably in the range of -200 gf or more and -40 gf or less.

The integrated value of the adhesive force in the probe tack test of the heat seal layer 1 is the resistance force when a probe is pressed against the main surface of the heat seal layer 1 of the laminated sheet for lid 10 and pulled up using probe tack under the conditions described below. It shows the product of (adhesive force) and pulling time. The integral value of adhesive force measured by a probe tack test in the heat seal layer 1 is preferably in the range of 5 gf·sec to 150 gf·sec, more preferably in the range of 7.5 gf·sec to 80 gf·sec. It's within.

The heat seal layer 1 is made of, for example, ethylene-vinyl acetate (EVA), ethylene-aliphatic unsaturated carboxylic acid copolymer, ethylene-aliphatic unsaturated carboxylic acid ester copolymer, etc. Ethylene coalition, ionomer resin, or other polyolephins (for example, linear lows (LINEAR LOW DENSITY POLYETHYLENE; LLDPE), ultra -low -density luggage polyethylene (Very Low Den) SITY POLYETHYLENE; VLDPE), and polypropylene etc.) may be included.

From the viewpoint of processability, the heat seal layer 1 preferably contains ethylene-vinyl acetate copolymer (EVA). When the heat seal layer 1 contains an ethylene-vinyl acetate copolymer, the content is 51% by mass or more according to one example, and 70% by mass or more according to another example. Further, the heat seal layer 1 may contain other components such as other resins such as polyolefins and additives, within a range that does not impair the above-mentioned effects of containing the ethylene-vinyl acetate copolymer. From the viewpoint of ensuring the content of other components, the content of the ethylene-vinyl acetate copolymer contained in the heat seal layer 1 may be, for example, 95% by mass or less.

The glass transition temperature (Tg) of the ethylene-vinyl acetate copolymer may be from 20°C to 70°C, according to one example, and from 30°C to 60°C, according to another example. The glass transition temperature of the ethylene-vinyl acetate copolymer can be adjusted by adjusting the content of monomers constituting the copolymer. Generally, as the content fraction of ethylene monomer increases, the glass transition temperature of the copolymer decreases, and as the content fraction of vinyl acetate monomer increases, the glass transition temperature of the copolymer increases.

Here, the glass transition temperature (Tg) was measured using a DSC (differential scanning calorimeter) in accordance with JIS K7271:2012.

The heat seal layer 1 may contain two or more types of ethylene-vinyl acetate copolymers having different glass transition temperatures (Tg).

The heat seal layer 1 may be provided on the paper base material 4 by lamination, for example, or may be a coating film obtained by applying a heat seal varnish or a water-based emulsion onto the paper base material 4 and drying it. . For example, the heel sheet layer 1 is formed by applying a heat seal varnish obtained by dissolving an ethylene-vinyl acetate copolymer in a solvent or a water-based emulsion of an ethylene-vinyl acetate copolymer onto the paper base material 4 and drying it. It may also be a coating film obtained by Solid plasticizers and tackifiers can be added to heat seal varnishes and water-based emulsions.

The method for applying the heat seal varnish or water-based emulsion is not particularly limited, and may be appropriately selected from commonly used coating equipment. For example, air knife coater, blade coater, gravure coater, rod blade coater, roll coater, reverse roll coater, bar coater, curtain coater, die slot coater, champlex coater, metering blade type size press coater, short dwell coater, spray Various known coating methods such as a coater, gate roll coater, lip coater, etc. can be used.

The mass per area of the heat-sealing layer 1 is, for example, within the range of 0.5 to 5.8 g/m ² from the viewpoint of reducing the amount of plastic used by thinning the film and balancing adhesive strength. is preferable, and according to another example, it is preferably within the range of 3.0 to 5.0 g/m ² . According to one example, the thickness of the heat seal layer 1 is preferably in the range of 0.5 μm or more and 7.5 μm or less, and according to another example, it is in the range of 2.5 μm or more and 6.0 μm or less. It is preferable.

(Printing layer)
The printed layer 5 is a layer formed in order to put the lid laminate sheet 10 or the lid into practical use as a commercial product. The printing layer 5 is made of, for example, a conventionally used ink binder resin such as urethane-based, acrylic-based, nitrocellulose-based, rubber-based, or vinyl chloride-based, and various pigments, extender pigments, plasticizers, drying agents, and stabilizers. This layer is made of ink to which additives such as agents are added, and displays patterns such as letters and pictures. As a method for forming the printing layer 5, for example, well-known printing methods such as offset printing, gravure printing, and silk screen printing, and well-known coating methods such as roll coating, knife edge coating, and gravure coating are used. be able to.

The thickness of the printed layer 5 is not particularly limited, and may be, for example, within the range of 0.1 to 5 μm, or may be within the range of 0.2 to 1 μm.

(Functional layer with water resistance)
The functional layer (water-resistant layer) 6 having water resistance suppresses liquids from outside the container, such as water and oil due to dew condensation, from penetrating into the lid body in packaged foods described later, and prevents this liquid from penetrating the printed layer 5. This is a layer that prevents the particles from reaching layers such as the paper base material 4 and the like. The functional layer 6 prevents liquid from outside the container from reaching the layers such as the printing layer 5 and the paper base material 4, thereby preventing, for example, deterioration, destruction, or reduction in adhesion of these layers.

According to one example, the functional layer 6 is formed on the printed layer 5 to reduce the water absorption of the partially laminated sheet, which is the portion from the functional layer 6 to the paper base material 4 of the laminated sheet 10 for the lid. Control. The functional layer 6 preferably has water resistance that makes the water absorption of the laminated sheet for a lid body 20 g/m ² or less by the Cobb method described below.

Here, water absorption refers to the contact time of the test piece with water, using the measurement surface as the surface of the functional layer 6, in the method specified in JIS P8140:1998 "Paper and paperboard - Water absorption test method - Cobb method". This is the water absorption obtained when the time is 300 seconds. As mentioned above, this water absorption is preferably 20 g/m ² or less, more preferably 10 g/m ² or less, and even more preferably 5 g/m ² or less. The lower limit of this water absorption is ideally 0 g/m ² . According to one example, this water absorption is greater than or equal to 1 g/m ² .

The functional layer 6 is preferably an overprint varnish layer (hereinafter referred to as "OP varnish layer").

According to one example, the functional layer 6 contains a water-resistant resin. As the water-resistant resin, any resin that can achieve the above-mentioned water absorption can be used without any restriction. Examples of water-resistant resins include polyolefin resins such as polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, and vinyl chloride-vinyl acetate copolymers, silicone resins, acrylic resins, epoxy resins, Polyester resins, cellulose resins, or urethane resins can be used. The functional layer 6 can be obtained, for example, by applying a paint containing a water-resistant resin onto the paper base material 4 on which the printing layer 5 is formed by a known method. In addition to the water-resistant resin, the paint may further contain additives such as pigments, dyes, curing agents, leveling agents, antiblocking agents, and lubricants, and solvents.

The functional layer 6 preferably has high abrasion resistance and scratch resistance so as to maintain sufficient water resistance. From this point of view, it is preferable that the thickness of the functional layer 6 and the coating amount of the paint that is its material are larger than the thickness of the normal OP varnish layer and the coating amount of the normal OP varnish. Here, the "coating amount" is the solid mass per area.

For example, in the lid laminated sheet 10 shown in FIG. 1, the paint for forming the functional layer 6 is preferably applied in an amount of 0.2 g/m ² or more, and 2.0 g/m 2 or more. It is more preferable to apply the coating in such a manner that the coating thickness is at least /m ² . This paint is applied in such a manner that the coating amount is, for example, 10 g/m ² or less. The thickness of the functional layer 6 is preferably 0.2 μm or more, more preferably 2.0 μm or more. The thickness of the functional layer 6 is, for example, 10 μm or less. Note that the functional layer 6 may be provided on the printing layer 5 by lamination.

(Adhesive layer)
The lid laminated sheet 10 can further include one or more adhesive layers.
For example, when the film-like heat-sealing layer 1 is laminated onto the paper base material 4, an adhesive layer may be included between the heat-sealing layer 1 and the paper base material 4 to bond them together.

For the material of the adhesive layer, an adhesive resin or an adhesive that provides the necessary adhesive strength is appropriately selected and used depending on the material of the layer to be adhered through the adhesive layer.

Examples of the adhesive resin include low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, and polyethylene such as a copolymer of ethylene-α olefin polymerized using a metallocene catalyst; Vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl methacrylate copolymer, and ethylene-maleic acid copolymer, etc. One or more resins selected from ethylene-unsaturated carboxylic acid copolymers; and ionomer resins can be used.

The adhesive is, for example, an adhesive composition formed by mixing a first composition containing a base agent and a solvent and a second composition containing a curing agent and a solvent. The adhesive layer obtained from this adhesive includes a cured product produced by the reaction between the main agent and the curing agent in the adhesive composition.

An example of the main ingredient is a polyol. Examples of curing agents include isocyanate compounds. Examples of the adhesive include ether-based two-component reactive adhesives and ester-based two-component reactive adhesives.

The cured product of the ether-based two-part reactive adhesive is, for example, polyether polyurethane. Polyether polyurethane is produced by the reaction of a polyether polyol as a main ingredient and an isocyanate compound as a curing agent.

Examples of cured ester-based two-component adhesives include polyester polyurethane and polyester. Polyester polyurethane is produced by the reaction of a polyester polyol as a main ingredient and an isocyanate compound as a curing agent.

In a two-component reactive adhesive, an acrylic polyol may be used as the main ingredient. Moreover, the above-mentioned adhesive composition does not need to contain a solvent as long as it can be melted by heating and its viscosity can be lowered.

The mass per area of the lid laminated sheet 10 is preferably in the range of 50 to 160 g/ ^m2 , more preferably in the range of 60 to 140 g/ ^m2 , and more preferably in the range of 70 to 130 g/m2. It is more preferable to fall within the range of ^m2 . If this value is reduced, the strength of the lid will be reduced. If this value is increased, the lid will become harder and the ease of opening will decrease. Furthermore, increasing this value not only increases the cost but also increases the amount of carbon dioxide emissions associated with manufacturing and exhaust.

[Modified example]
Various modifications can be made to the laminated sheet for the lid. For example, as described below, the laminated sheet for lids may further include one or more of a support layer, a gas barrier layer, and an anchor coat layer in addition to the laminated sheet for lids 10 shown in FIG. . A modified example will be described below with reference to FIGS. 2 and 3. Note that the matters described with reference to FIG. 1 can be applied singly or in combination to the laminated sheet for a lid body according to the modified example described herein.

FIG. 2 is a partial sectional view schematically showing a laminated sheet for a lid according to a modified example.
The lid laminated sheet 11 shown in FIG. 2 is the same as the lid laminated sheet 10 described with reference to FIG. 1, except that it further includes a support layer 2 and a gas barrier layer 3.

(Support layer)
The support layer 2 improves the strength of the lid laminated sheet 11. The support layer 2 may be made of non-woven materials such as ethylene/vinyl alcohol copolymer film, nylon film, PET (polyethylene terephthalate) film, PAN (polyacrylonitrile) film, PBT (polybutylene terephthalate) film, PMP (polymethylpentene), etc. Examples include stretched films such as stretched or biaxially stretched films, but are not limited to these, and films using polyvinyl alcohol resins, olefin resins, unsaturated polyester resins, etc. may also be used. The breaking strength can be adjusted by using additives such as curing agents and fillers, curing treatment by electron beam irradiation, and the like.

The thickness of the support layer 2 is preferably within the range of 3 μm to 50 μm, more preferably within the range of 10 μm to 30 μm. If the support layer 2 is too thick, the amount of carbon dioxide emissions and costs associated with manufacturing the support layer 2 and disposing of the lid laminated sheet 11 will increase. If the support layer 2 is too thin, it will be difficult to achieve high breaking strength.

The breaking strength of the support layer 2 is preferably greater than the heat sealing strength between the lid 21 and the container body 22 of the food packaging container 20 shown in FIG. 4, which will be described later. Here, the fact that the breaking strength of the supporting layer 2 is greater than the heat sealing strength between the lid 21 and the container body 22 means that in MD (Machine Direction), the breaking strength of the supporting layer 2 is greater than the heat sealing strength between the lid 21 and the container body 22. This means that the breaking strength of the support layer is greater than the heat sealing strength between the lid 21 and the container body 22 in TD (Transverse Direction).

The breaking strength of the support layer 2 is the tensile force obtained by the measuring method specified in JIS Z1707:2019 "General rules for plastic films for food packaging." Note that this tensile force (N/15 mm) is a value obtained by converting the maximum force when the test piece breaks into a force (N/15 mm) equivalent to the width of the test piece of 15 mm. The heat seal strength between the lid and the container body will be described later.

When the breaking strength of the support layer 2 is greater than the heat sealing strength between the lid 21 and the container body 22, paper peeling is less likely to occur when the lid 21 is peeled off from the container body 22. For example, when the breaking strength of the support layer 2 is greater than 30 N/15 mm, paper peeling can be suppressed until the heat seal strength is about 30 N/15 mm. Here, "paper peeling" means that when the lid 21 is peeled off from the container body 22, cohesive failure of the paper base material 4 occurs and a part of the lid 21 remains on the container body 22. . When paper peels off, it may become difficult to take out the contents stored in the container body 22.

The heat seal strength is adjusted depending on the use and purpose of the packaging container 22. For example, the heat seal strength may be reduced in order to provide ease of opening. Therefore, the breaking strength of the support layer 2 does not need to be more than 30 N/15 mm. The breaking strength of the support layer 2 is not particularly limited, but is preferably in the range of 10 to 100 N/15 mm, more preferably in the range of 25 to 85 N/15 mm. When the above-mentioned breaking strength is increased, the effect of reinforcing the laminate to suppress paper peeling increases. However, if the support layer 2 is made thicker in order to increase the breaking strength, as described above, the amount of carbon dioxide emissions and costs associated with manufacturing the support layer 2 and disposing of the lid laminated sheet 11 will increase.

Note that the support layer 2 only needs to be included between the paper base material 4 and the heat seal layer 1, and is not limited to the position shown in FIG. 2.

(Gas barrier layer)
The gas barrier layer 3 has gas barrier properties such as oxygen barrier properties and water vapor barrier properties. The gas barrier layer 3 suppresses gases such as oxygen, water vapor, and aroma components from outside the container from entering the container in the packaged food described later. Thereby, the gas barrier layer 3 suppresses deterioration of the food contents in the packaged food. Moreover, the gas barrier layer 3 suppresses the diffusion of odor components of the contents to the outside of the container in the packaged food. According to one example, the gas barrier layer 3 has an oxygen permeability of 0.1 to 100 cc/m ² /day/atm in an atmosphere of a temperature of 30° C. and a relative humidity of 70%.

The gas barrier layer 3 is, for example, a metal layer, an inorganic oxide layer, a resin-containing layer, or a combination of two or more thereof. When microwave heating using a microwave oven is assumed, the gas barrier layer 3 is preferably an inorganic oxide layer, a resin-containing layer, or a combination thereof.

The gas barrier layer 3 may be formed by coating, melt molding, or vapor-deposited inorganic oxide. Alternatively, the gas barrier layer 3 may be a metal foil such as an aluminum foil, or may be formed by vapor-depositing a metal such as aluminum.

Examples of inorganic oxides include silicon oxide, boron oxide, or metal oxides such as aluminum oxide, magnesium oxide, calcium oxide, potassium oxide, tin oxide, sodium oxide, titanium oxide, lead oxide, zirconium oxide, and yttrium oxide. can use things.

The resin-containing layer can be formed, for example, by coating. In this case, a coating liquid containing a resin such as polyvinyl alcohol, ethylene-vinyl alcohol copolymer, ethylene-vinyl acetate copolymer, polyvinylidene chloride, polyacrylonitrile, and epoxy resin can be used. Additives such as organic or inorganic particles, layered compounds, and curing agents may be added to this coating liquid.

When the resin-containing layer is formed by melt molding, for example, the above-mentioned resin or a mixture of the above-mentioned resin and an additive can be used as the material. For example, extrusion molding techniques such as T-die and inflation can be used for melt molding.

The thickness of the gas barrier layer 3 is in the range 0.01 to 30 μm according to one example, and in the range 0.1 μm to 12 μm according to another example.

The laminated sheet 11 for a lid may include a gas barrier layer 3 and a support layer 2 as a barrier film in which the gas barrier layer 3 is provided on the support layer 2. When the gas barrier layer 3 and the support layer 2 are included as a barrier film, it is easy to adjust necessary physical properties such as barrier properties and durability depending on the use or purpose.

The lid laminated sheet 11 may include the gas barrier layer 3 and the paper base material 4 as a barrier paper in which the gas barrier layer 3 is provided on the paper base material 4. When the gas barrier layer 3 and the paper base material 4 are included as a barrier paper, it is easy to adjust the necessary physical properties such as barrier properties and durability depending on the use or purpose.

Note that the gas barrier layer 3 only needs to be included between the print layer 5 and the heat seal layer 1, and is not limited to the position shown in FIG. 2.

This laminated sheet 11 for lids has the same effects as described above for the laminated sheet 10 for lids. In addition to having gas barrier properties, this lid laminated sheet 11 does not easily deteriorate gas barrier properties, particularly oxygen barrier properties. This will be explained below.

Food packaging containers are sometimes desired to have excellent oxygen barrier properties that prevent oxygen from entering from the outside in order to suppress the oxidation of the packed food. In such food packaging containers, the lid is also required to have oxygen barrier properties.

To impart gas barrier properties against oxygen and the like to a paper-based lid, a metal foil or a metal-deposited film made of a metal such as aluminum is often provided as a gas barrier layer on the paper base material, for example. However, food packaging containers whose lids include metal layers cannot be inspected for metal foreign matter using a metal detector after filling, and cannot be incinerated as paper because they contain metal, so they can be recycled as waste paper. There are problems in that it cannot be used in packaging containers for chilled foods that are expected to be cooked in a microwave oven.

As mentioned above, some gas barrier layers do not include a metal layer. As such a gas barrier layer, those containing resins such as polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyvinylidene chloride, polyamide such as nylon MXD6, and polyacrylonitrile are often used. A metal layer-less lid can avoid the above problems.

The optimum temperature range for distribution and storage of chilled foods is set for each food, but generally it is within the range of 0 to 10 degrees Celsius. After production, packaged foods made by housing chilled foods in food packaging containers reach consumers through various distribution channels. During this process, for example, from the time a consumer purchases a packaged food at a store until it is stored in the refrigerator at home, or from the time the consumer takes the packaged food out of the refrigerator until the time the consumer starts cooking, the packaged food is placed in a room temperature environment.

The present inventors have discovered that a packaged food in which a chilled food is housed in a food packaging container whose lid body includes a paper base material and a gas barrier layer, particularly a packaged food in which the gas barrier layer is a resin-containing layer, is stored in a refrigerated state. It has been found that the gas barrier properties, particularly the oxygen barrier properties, of the lid body decrease significantly during the first few hours of exposure to a room temperature environment. This is remarkable when the proportion of the mass of the paper base material to the mass of the lid is large.

The present inventors have found that the above problem is caused by dew condensation occurring on the surface of the lid. That is, when a packaged article that has been in a refrigerated environment is exposed to a room temperature environment, dew condensation occurs on the outer surface of the lid, and the moisture reaches the gas barrier layer, damaging the gas barrier layer. As a result, the oxygen barrier properties of the lid decrease.

The above laminated sheet 11 for a lid includes a functional layer 6 having water resistance. Therefore, in a packaged food using this lid laminated sheet 11 as a lid material, moisture generated on the outer surface of the lid due to dew condensation does not easily reach the gas barrier layer 3. Therefore, in a packaged food using this lid laminated sheet 11 as a lid material, the gas barrier layer 3 is less likely to be damaged due to dew condensation on the outer surface of the lid, and the oxygen barrier properties are less likely to deteriorate.

The present inventors have found that, in particular, in a packaged food made by storing a chilled food in a food packaging container, when the lid includes a paper base material, paper peeling occurs when the lid is peeled from the container body. I am discovering even more easy things. As mentioned above, paper peeling can be made less likely to occur by making the breaking strength of the support layer 2 greater than the heat sealing strength between the lid and the container body.

Note that the problems described above regarding the case where the contents are chilled foods may also occur when the contents are frozen foods. The configuration described here can produce the same effect as described above for the case where the content is a chilled food even when the content is a frozen food.

FIG. 3 is a partial cross-sectional view schematically showing a laminated sheet for a lid according to another modification.
The lid laminated sheet 12 shown in FIG. 3 is the same as the lid laminated sheet 11 described with reference to FIG. 2, except that it further includes the anchor coat layer 7. Note that the matters described with reference to FIGS. 1 and 2 can be applied singly or in combination to the laminated sheet for a lid according to the modification described herein.

(Anchor coat layer)
The anchor coat layer 7 is interposed between the support layer 2 and the heat seal layer 1 to improve the adhesion between these layers. If the interlayer adhesion is low, interlayer peeling (delami) occurs when the package is opened, and this tends to cause fuzzing and stringiness. Therefore, by interposing the anchor coat layer 7 between the support layer 2 and the heat-sealing layer 1, it is possible to suppress the occurrence of fluffing and stringiness due to peeling between these two layers when the package is opened.

The anchor coating agent used in the anchor coating layer 7 is not particularly limited, and for example, known ones such as a water-based anchor coating agent and a solvent-based anchor coating agent can be used. Examples of the water-based anchor coating agent include polyethyleneimine. Examples of solvent-based anchor coating agents include two-component curing anchor coating agents in which a base resin and a curing agent react to form a urethane bond; for example, the base resin is a polyester resin, and the curing agent is a polyisocyanate, etc. can be mentioned.

The mass per area of the anchor coat layer 7 is preferably in the range of 0.5 to 6.5 g/m ² according to one example, and 0.5 to 2.0 g/m ² according to another example. It is preferable that it is within the range of .

As a method for forming the anchor coat layer 7, for example, well-known printing methods such as offset printing, gravure printing, and silk screen printing, and well-known coating methods such as roll coating, knife edge coating, and gravure coating may be used. Can be used.

Note that the anchor coat layer 7 may be disposed between the paper base material 4 and the heat seal layer 1 so as to be adjacent to the heat seal layer 1. Therefore, the layer adjacent to the surface of the anchor coat layer 7 on the opposite side to the surface adjacent to the heat seal layer 1 is not limited to the support layer 2. For example, in the lid laminated sheet 10 shown in FIG. 1, the anchor coat layer 7 may be interposed between the paper base material 4 and the heat seal layer 1.

(Adhesive layer)
The lid laminated sheet 11 and the lid laminated sheet 12 can further include one or more adhesive layers.
For example, the lid laminated sheets 11 and 12 may include an adhesive layer between the paper base material 4 and the gas barrier layer 3 to bond them together.

[Second embodiment]
The lid according to the second embodiment of the present invention is a lid obtained from the lid laminated sheet according to the first embodiment or the modified example described above. An example of the lid according to the second embodiment is a lid 21 that will be described later with reference to FIG. 4. As explained in connection with the lid laminated sheets 10 and 11, the lid according to the present embodiment has a paper mass ratio in the lid, and prevents fuzzing and stringiness while maintaining sealing performance. Excellent opening properties.

[Third embodiment]
FIG. 4 is a cross-sectional view schematically showing a food packaging container according to a third embodiment of the present invention. The food packaging container 20 shown in FIG. 4 includes a container body 22 provided with an opening, and a lid 21 that covers the opening.

The container body 22 has, for example, a cylindrical shape with a bottom. The container body 22 here includes a bottom portion, a body portion (or side wall portion), and a flange 22a. The flange 22a widens outward at the upper opening of the body.

The container body 22 includes, for example, an olefin resin such as polypropylene (PP). The container body 22 may further contain a component such as ethylene-vinyl alcohol copolymer (EVOH) in order to improve its gas barrier properties. Further, the container body 22 may further contain additives, for example, additives intended to improve processability, design, and chemical durability.

The container body 22 may have a single layer structure or a multilayer structure. This multilayer structure may be a two-layer structure or may include three or more layers. In the latter case, the multilayer structure may be a three-layer structure (PP/PP+EVOH/PP) including a gas barrier layer, for example, a layer containing a component such as the above-mentioned ethylene-vinyl alcohol copolymer as an intermediate layer.

Paper can also be used for the container body 22. When the contents include a liquid substance, the container body 22 includes a paper base material and a layer made of resin or the like provided on the surface of the content side to prevent the liquid substance from seeping into the paper base material. A multilayer structure including the following can be adopted. As the material for the container body 22 containing the paper base material, for example, paper leaves, paper powder, pulp, or waste paper can be used. For forming the container body 22, general-purpose techniques such as folding and pasting of sheets containing paper leaves as used in the production of paper packs, press molding of sheets using molds, and pulp molding can be used. It is. By using paper for the container body 22, it is possible to reduce the amount of carbon dioxide emitted during the manufacturing and disposal of the food packaging container 20 as a whole, thereby reducing the burden on the environment.

The lid 21 is any one of the laminated sheets 10 to 12 for lids, or is cut out from any of them. The lid 21 is heat-sealed to the flange 22a via the heat-sealing layer 1 after the contents are contained in the container body 22. In this heat sealing, the sealing temperature, sealing pressure, and sealing time can be set as appropriate.

[Fourth embodiment]
The packaged food according to the fourth embodiment of the present invention is obtained by accommodating a food product in the food packaging container according to the third embodiment described above. The food to be accommodated is not particularly limited, but is preferably a chilled food or a frozen food. Chilled foods and frozen foods are, for example, cooked or processed foods. Chilled foods and frozen foods are, for example, grilled fish, boiled fish, or prepared foods.

In this packaged food, as described above, the heat sealing strength between the lid 21 and the container body 22 is preferably smaller than the breaking strength of the support layer 2 included in the lid 21. This heat sealing strength is preferably within the range of 5N/15mm to 60N/15mm, more preferably within the range of 10N/15mm to 50N/15mm. The difference between the breaking strength of the support layer 2 and the heat sealing strength between the lid 21 and the container body 22 is preferably within the range of 5 to 60 N/15 mm, and preferably within the range of 10 to 40 N/15 mm. It is more preferable that there be. Here, the heat seal strength is a value obtained by the method specified in JIS Z0238:1998 "Test method for heat seal flexible packaging bags and semi-rigid containers".

In manufacturing this packaged food, before heat-sealing the lid 21 to the container body 22, for example, after the contents have been accommodated in the container body 22, the lid 21 is heat-sealed to the container body 22. Before this, the gas in the container body 22 may be replaced by a known method. For example, the container body 22 may be filled with an inert gas. By appropriately changing the gas composition inside the container, we can suppress the growth of bacteria and extend the quality shelf life, maintain the flavor and color of food for a long time by preventing oxidation, and prevent the loss of vitamins. be able to. The replacement gas is appropriately selected depending on the type of food contained therein. As the replacement gas, a mixed gas of oxygen gas, nitrogen gas, and carbon dioxide gas is suitably used.

The lid included in this packaged food has excellent sealing and opening properties. Therefore, in addition to being less likely to cause deterioration of the contents, this packaged food is also less likely to cause problems associated with the lid being destroyed when the package is opened, resulting in fuzzing or stringiness, and a portion of the lid remaining in the container. .

Tests conducted in connection with the present invention will be described below.
<1> Manufacture of laminated sheet for lid (Example 1)
The laminated sheet 11 for lid shown in FIG. 2 was manufactured by the following method.
First, imitation paper having a basis weight of 37.3 g/m ² was prepared. By coating one side of this imitation paper with a coating liquid containing polyvinyl alcohol (PVA), styrene-butadiene rubber (SBR), silica, and layered silicate as the main components, and water as the main solvent, A single-sided coated paper with a coating layer of 15 g/m ² (dry state) was prepared as the paper base material 4.

By sequentially forming a printed layer 5 and a functional layer 6 on the coat layer of this paper base material 4 using a gravure multicolor printing machine, the paper base material 4, the printed layer 5, and the functional layer 6 are formed. A laminate a was obtained. The printing layer 5 was formed using normal printing ink. The amount of printing ink applied was 1.0 g/m ² . The functional layer 6 was formed using an OP varnish agent containing nitrocellulose resin and polyethylene granular wax as main components. The coating amount of the OP varnish agent was 0.5 g/m ² .

On the other hand, polyethylene terephthalate (PET) with a thickness of 12 μm was prepared as the support layer 2. A barrier layer 3 was formed on one side of this support layer 2 by vapor depositing alumina. The basis weight of the laminate b consisting of the support layer 2 and the barrier layer 3 was 16.8 g/m ² .

Next, a laminate b consisting of a support layer 2 and a barrier layer 3 was attached to a laminate a consisting of a paper base material 4, a printed layer 5, and a functional layer 6 by dry lamination. For dry lamination, first, a dry laminating agent was applied onto the surface of the barrier layer 3 of the laminate b using a gravure coater to form an adhesive layer. As the dry laminating agent, a two-component reactive adhesive containing an ester polyol and an isocyanate curing agent was used. The amount of dry laminating agent applied was 3.0 g/m ² . Next, the laminates a and b are laminated together with this adhesive layer in between so that the surface of the barrier layer 3 of the laminate b faces the surface of the paper base material 4 of the laminate a. A body c (supporting layer 2/barrier layer 3/adhesive layer/paper base material 4/printing layer 5/functional layer 6) was obtained.

Next, a heat seal varnish (hereinafter referred to as "HS varnish") was applied onto the surface of the support layer 2 of the obtained laminate c using a gravure coater, and 5.3 g/m ² (dry state) was applied. A heat seal layer 1 was formed. As the HS varnish, HS varnish A shown below, which is an aqueous emulsion containing ethylene-vinyl acetate copolymer (EVA) as a main component, was used.

Thereafter, the obtained laminate was aged at 40°C. In the manner described above, the lid laminated sheet 11 shown in FIG. 2 was obtained.

(Examples 2 to 5 and Comparative Example 1)
A laminated sheet 11 for a lid was manufactured in the same manner as in Example 1, except that the type or amount of HS varnish applied (mass per area) was changed as shown in Table 1 below.

(Example 6)
A laminate c (supporting layer 2/barrier layer 3/adhesive layer/paper base material 4/printing layer 5/functional layer 6) was produced in the same manner as in Example 1. An anchor coat agent (AC agent) was applied onto the surface of the support layer 2 of the obtained laminate c using a gravure coater to form an anchor coat layer (AC layer) of 1.2 g/m ² (dry state). 7 was formed. As the anchor coating agent, a solvent-based anchor coating agent containing an ester resin as a main ingredient and a polyisocyanate as a curing agent was used.

Next, HS varnish D was applied onto this anchor coat layer 7 using a gravure coater to form a heat seal layer 1 of 3.3 g/m ² (dry state).

Thereafter, the obtained laminate was aged at 40°C. In the manner described above, the lid laminated sheet 12 shown in FIG. 3 was obtained.

(Examples 7 to 9 and Comparative Example 2)
A laminated sheet 12 for a lid was produced in the same manner as in Example 6, except that the type or amount of HS varnish applied (mass per area) was changed as shown in Table 1 below.

<HS varnish>
・HS Varnish A: EVA-containing water-based emulsion. The solvent is water/isopropyl alcohol (IPA). EVA: Tg 23°C, melting point 70-100°C.
・HS varnish B: EVA-containing aqueous emulsion. The solvent is water/IPA. EVA: Tg 38°C, melting point 70-100°C.
- HS Varnish C: A mixture of HS Varnish A and HS Varnish B. Mass ratio: HS varnish A/HS varnish B = 7:3.
- HS Varnish D: A mixture of HS Varnish A and HS Varnish B. Mass ratio: HS varnish A/HS varnish B = 3:7.

<Mass ratio of paper, plastic, and others>
Each layer included in each laminated sheet for lids was prepared in accordance with the above-mentioned "Container and Packaging Recycling Law Explanatory Materials". , AC layer and HS layer).
Next, the mass ratio (%) of each category to the lid laminated sheet was calculated. In calculating the mass ratio (%), the mass of a 200 mm x 250 mm size was measured and converted into g/m ² . The mass of the laminated sheet for the lid, the paper base material, and the support layer was actually measured, and the mass of "others" (functional layer, printing layer, gas barrier layer, adhesive layer, AC layer, and HS layer) was calculated based on the mass of the laminated sheet for the lid. It was calculated by subtracting the mass of the paper base material and support layer from the mass of the sheet.

<Breaking strength of support layer>
The breaking strength of the support layer 2 used in each laminated sheet for lids was measured in accordance with the tensile force measurement method of JIS Z1707:2019. The width of the test piece was 15 mm, and the length was 100 mm. The number of test pieces was three. The distance between the gauge lines was 50 mm, and the test speed was 1000 mm/min. The breaking strength was measured using a Tensilon universal testing machine. Breaking strength was measured in MD and TD.

<Heat seal test>
The heat seal strength of each lid laminated sheet was measured. Here, the adherend includes a pair of polypropylene (PP) layers and a layer made of a mixture of polypropylene and 4% by mass ethylene-vinyl alcohol copolymer (EVOH) interposed between them. A layered polypropylene resin sheet (PP/PP+EVOH 4% mass/PP) (B-130WE3, manufactured by Idemitsu Unitec) was used.

First, each lid laminated sheet and the polypropylene resin sheet were heat-sealed to obtain a test piece. The width of the test piece was 15 mm and the length was 50 mm. The number of test pieces was three. The sealing temperature was 190° C., the sealing pressure was 0.2 MPa, the sealing time was 2 seconds, and the width of the seal bar was 5 mm. Heat sealing was performed using a heat seal tester (trade name "TP-701-B"; manufactured by Tester Sangyo Co., Ltd.).

Next, the heat seal strength between each lid laminated sheet and the polypropylene resin sheet was measured by a method based on JIS Z0238:1998. Specifically, the heat-sealed portion of the test piece was opened at 180°, and a tensile load was applied to the heat-sealed portion to cause it to peel or break. The relative movement speed, ie, the peeling speed, was 1000 mm/min.

The heat seal strength was measured using a Tensilon universal testing machine. The heat seal strength was measured in MD and TD of the laminated sheet for the lid.

<Peak strength and integral value of adhesive force>
For the heat seal layer of each laminated sheet for lids, the peak strength and integral value of adhesive force were measured by a probe tack test. In the test, a probe tack device (TAC-1000, manufactured by Resca Co., Ltd.) was used to press the probe against the heat seal layer under the following conditions, and the maximum value of the resistance force (adhesive force) when pulled up was taken as the peak strength of the adhesive force. It was measured. Since the peak intensity is a measured value, it is a negative value. The larger the absolute value of the peak intensity is, the greater the adhesive force is, and the smaller the absolute value of the peak intensity is, the smaller the adhesive force is.

Further, the product of the above-mentioned resistance force (adhesive force) and pulling time was measured as an integral value of the adhesive force. Here, the lifting time means the time from when the probe is pulled up until the resistance becomes zero.

The measurement conditions are as follows.
Probe: 10mmφ cylindrical probe material: SUS
Temperature: 80℃
Pressing pressure: 0.5MPa
Pressing time: 20 seconds Pulling speed: 1mm/second

<Openability>
A food packaging container 20 shown in FIG. 4 was produced using each laminated sheet for lids, and the occurrence of defects (fuzzing, stringiness, paper peeling, etc.) when the lid 21 was opened was evaluated.

In producing the food packaging container 20 shown in FIG. 4, first, the lid 21 was cut out from each lid laminated sheet. As the container body 22, a polypropylene resin sheet B-130WE3 (PP/PP+EVOH 4% mass/PP) used for the heat seal strength measurement described above was press-molded into a flanged tray shape using hot pressure. did. The container main body 22 had a substantially rectangular opening with a length of 120 mm in the long side direction and a length of 90 mm in the short side direction, and a height of 30 mm. Heat sealing of the lid body 21 to the flange 22a is performed by applying a temperature of 210° C. and a pressure of 0.2 MPa for 1.5 seconds using a seal bar with a width of 5 mm that is made to follow the shape of the flange 22 a. This was done by

Regarding the obtained food packaging container 20, the lid 21 was opened by hand from the corner of the container body 22. The appearance of residue on the lid body 21 with respect to the container body, such as fuzzing, stringiness, and paper peeling, upon opening was evaluated.

(Fuzzing, stringiness, etc.)
A: There is no easily visible fluffing or stringiness, and there is no minute film residue.
B: Stringing occurs locally, but there is no residual adhesion that could reach the opening of the container or mix into the contents, and there is no deterioration in appearance after peeling.
C: Fuzzing occurs, and film residues that may reach the opening of the container or contaminate the contents are observed.

(Paper peeling, etc.)
The presence or absence of paper peeling was visually evaluated. As mentioned above, "paper peeling" means that when the lid 21 is peeled off, cohesive failure of the paper base material 4 occurs and a part of the lid 21 remains on the container body 22 (double lid, (including membrane breakage).
A: No paper peeling occurred.
B: Paper peeling occurred.

The results of the above measurements and tests are summarized in Table 1 below. In addition, in Table 1, "mass" is mass per area. The classification of "paper," "plastic," and "other" in the column labeled "mass ratio" is in accordance with the "Containers and Packaging Recycling Law Explanatory Materials." The column labeled "Difference" lists the value obtained by subtracting the heat seal strength between the lid laminated sheet and the resin sheet from the breaking strength of the support layer.

Note that the present invention is not limited to the above-described embodiments, and can be variously modified at the implementation stage without departing from the gist thereof. Moreover, each embodiment may be implemented in combination as appropriate, and in that case, the combined effect can be obtained. Furthermore, the embodiments described above include various inventions, and various inventions can be extracted by combinations selected from the plurality of constituent features disclosed. For example, if a problem can be solved and an effect can be obtained even if some constituent features are deleted from all the constituent features shown in the embodiment, the configuration from which these constituent features are deleted can be extracted as an invention.

DESCRIPTION OF SYMBOLS 1... Heat seal layer, 2... Support layer, 3... Gas barrier layer, 4... Paper base material, 5... Printing layer, 6... Functional layer, 7... Anchor coat layer, 10... Laminated sheet for lid, 11... Lid 12... Laminated sheet for lid, 20... Food packaging container, 21... Lid, 22... Container body, 22a... Flange.

Claims (16)

A laminated sheet for a lid used for the lid of a food packaging container comprising a container body provided with an opening and a lid covering the opening, the sheet comprising: a functional layer having water resistance; a printed layer; It includes a paper base material and a heat seal layer in this order, the mass of the paper base material is greater than the mass of any other layer included in the laminated sheet for lid, and the heat seal layer The peak strength of the adhesive force measured by the tack test is in the range of -490 gf or more and -20 gf or less, or the integrated value of the adhesive force measured by the probe tack test is in the range of 5 gf/sec or more and 180 gf/sec or less. Laminated sheet for the lid inside. The lid according to claim 1, further comprising a support layer between the paper base material and the heat-sealing layer, and the breaking strength of the support layer is greater than the heat-sealing strength between the lid and the container body. Laminated sheet. The laminated sheet for a lid according to claim 1, further comprising a gas barrier layer between the printing layer and the heat-sealing layer. The laminated sheet for a lid according to claim 1, wherein the paper base material is a coated paper having a coat layer on one side, and the printing layer is provided on the coat layer. The laminated sheet for a lid body according to claim 1, wherein the heat seal layer has a mass per area of 0.5 to 5.8 g/ ^m2 . The laminated sheet for a lid according to claim 1, wherein the heat seal layer contains one or more ethylene-vinyl acetate copolymers having a glass transition temperature in the range of 20° C. or higher and 70° C. or lower. The laminated sheet for a lid body according to claim 6, wherein the heat seal layer is a coating film derived from an aqueous emulsion or a heat seal varnish. An anchor coat layer is provided between the paper base material and the heat seal layer, and the anchor coat layer is disposed adjacent to the heat seal layer, and the anchor coat layer has a mass per area of 0.5 to 6.5 g/m. The laminated sheet for a lid according to claim 1, which is within the range of ² . When the layers other than the paper base material included in the lid laminated sheet are classified into layers made of plastic and other layers, the mass of the paper base material is the sum of the layers made of plastic. The laminated sheet for a lid body according to claim 1, which is larger than the total mass of the mass and the other layers. The laminated sheet for a lid according to claim 1, wherein a mass ratio of the paper base material to the laminated sheet for a lid is 60% or more. A lid made of the laminated sheet for lids according to any one of claims 1 to 10. 12. A food packaging container comprising a container body provided with an opening and a lid according to claim 11 that covers the opening, wherein the support layer is formed between the paper base material and the inside of the food packaging container. A food packaging container placed between the space. 13. The food packaging container according to claim 12, wherein the container body has a flange around the opening, and the lid is heat-sealed to the flange via the heat-sealing layer. The food packaging container according to claim 12, wherein the internal space of the food packaging container is filled with a mixed gas containing oxygen gas, nitrogen gas, and carbon dioxide gas. The food packaging container according to claim 12, wherein the food packaging container is a chilled food packaging container or a frozen food packaging container. A packaged food comprising the food packaging container according to claim 12 and a food contained in the food packaging container.