JPH06239374A - Container lid - Google Patents

Abstract

(57) [Summary] [Purpose] The lid of a half-open container can be automatically sealed by being heated by the steam supplied to the container. [Composition] A lid having a laminated sheet of a base material layer / adhesive layer / metal layer / heat-sealable resin layer, which is printed on the surface thereof, must meet the following requirements (1) and (2). The lid of the container characterized by. (1) Fine voids inside a film made of a stretched product of a thermoplastic resin film containing 8 to 65% by weight of an inorganic fine powder (excluding scale-like inorganic fine powder) on which the substrate layer is printed. And a back surface layer made of a thermoplastic resin film containing 5 to 70% by weight of scale-like inorganic fine powder. (2) The pulling portion of the lid for peeling the heat-sealed lid from the container, the base material layer is heated from a temperature of 30 ° C to a temperature of 80 ° C over 5 minutes at a heating rate of 10 ° C / minute. It is provided so as to match the direction of the base material layer having a large coefficient of thermal expansion.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a heat-sealing of a container for instant food such as instant cup noodles, cup sushi, cup soup, and cup miso soup, which is eaten after pouring hot water into the container and holding it for a certain period of time. Regarding the lid used.

[0002]

2. Description of the Related Art Conventionally, instant foods represented by instant cup noodles can be eaten simply by pouring hot water into a container and waiting for a few minutes (1 to 5 minutes). It is eaten in large quantities by singles, factory night workers, single employees, students, and others. To eat such an instant food, for example, the case of instant cup noodles will be specifically described. First, the transparent shrink wrapping film packaged at the time of purchase is removed, and then the container is heat-sealed (heat-sealed). The pulled portion of the sealed lid is picked up with fingers and pulled up, and about 1/3 to 1/2 of the lid is peeled off from the container. Then, the bag containing the ingredients and soup other than the noodles in the container is cut with fingers, placed on the noodles, and boiling water is poured into this. After pouring hot water, the part of the peeled lid is placed on the flange portion at the upper end of the container to close the lid, and a weight is placed on the lid so that the lid does not roll up and open, or The heat in the container is prevented from escaping by using tape or the like to improve the heat efficiency, and the contents are steamed. And
After a lapse of a predetermined time (1 to 5 minutes), the weight on the lid is removed, the rolled-up lid is pulled, the lid is completely peeled off from the container, and the contents are steamed. Can eat.

As containers used for such instant foods, polystyrene paper (PSP) and high-impact polystyrene (HI), which have good heat retention, are usually used.
PS) sheet, plug-assisted vacuum forming or pressure forming of a laminated sheet of nylon and polyethylene into a cup shape, expanded polystyrene cup obtained by in-mold bead foam molding, and a container obtained by injection molding of polypropylene Are used. Further, as the lid used for the above-mentioned container, as shown in FIG. 5, a high-quality paper having a print 15 on its surface is used as the base material layer 2, and a low-density polyethylene, an ethylene / acrylic acid copolymer Adhesive layer 3 extrusion-coated with a molten resin film, or adhesive layer 3 coated with a urethane-based or polyester-based liquid adhesive (so-called anchor coating agent), with a thickness of 6 to 15
an aluminum foil layer 4 obtained by laminating an aluminum foil of μm,
Furthermore, a low melting point (80-135) of low-density polyethylene or ethylene-vinyl acetate copolymer is formed on the aluminum foil layer.
(° C.) A laminated sheet 6 having a four-layer structure having a heat-sealing property, which is composed of a heat-sealing layer 5 obtained by applying a resin by extrusion laminating or dissolving in a solvent, was used.

[0004]

However, such a lid of an instant food container has such a feature that when the lid of the container is partially opened and hot water is poured, the steam of the hot water passes through the aluminum layer on the inside of the lid to form a base material. As a result of heating the high-quality paper and releasing the water content in the high-quality paper, the high-quality paper contracts and the lid curls upward and warps (see FIG. 6). Therefore, the lid of an instant food container cooked with this kind of hot water conventionally requires the trouble of pouring hot water and then closing the lid of the opened lid by weighting the lid. It was

[0005]

[Means for Solving the Problems]

[Summary of the Invention] The inventors of the present invention have conducted extensive studies in view of the above problems, and as a result, can thermally expand outside the metal foil more greatly than the metal foil due to the temperature of steam, and the thermal expansion thereof Also utilizes the property of the lid to return to its original position due to the heat of the stretched resin film, and as long as the lid does not curl inward after returning to its original position, it has a specific structure. The present invention has been completed based on the knowledge that the lid of a container can be automatically closed by using a stretched resin film for bonding. That is, the lid of the container of the present invention is a lid formed of a laminated sheet of a base material layer / adhesive layer / metal layer / heat-sealable resin layer, which is printed on the surface, and has the following (1) and (2): It is characterized by having the requirements of. (1) Fine voids inside a film made of a stretched product of a thermoplastic resin film containing 8 to 65% by weight of an inorganic fine powder (excluding scale-like inorganic fine powder) on which the substrate layer is printed. And a back surface layer made of a thermoplastic resin film containing 5 to 70% by weight of scale-like inorganic fine powder. (2) The pulling portion of the lid for peeling the heat-sealed lid from the container, the base material layer is heated from a temperature of 30 ° C to a temperature of 80 ° C over 5 minutes at a heating rate of 10 ° C / minute. It is provided so as to match the direction of the base material layer having a large coefficient of thermal expansion.

[Detailed Description of the Invention] [I] Container Lid (1) Structure As shown in FIG. 1, the container lid 1 of the present invention basically has the following base material layer 2 / adhesive layer. 3 / Metal layer 4 / Heat-sealing resin layer 5 is included in the laminated sheet 6. (a) Base Material Layer <Structure of Base Material Layer> As the base material layer 2 used in the lid 1 of the container of the present invention, as shown in FIG. 1, inorganic fine powder (excluding scale-like inorganic fine powder) 7 And a back surface layer 2b made of a thermoplastic resin film containing the flaky inorganic fine powder 9 and a back surface layer 2b made of a stretched thermoplastic resin film containing at least two layers.

Surface Layer The surface layer 2a is a thermoplastic resin containing 8 to 65% by weight, preferably 20 to 55% by weight, of inorganic fine powder (excluding scale-like inorganic fine powder) 7 for printing. It is formed from a stretched film. When the content of the inorganic fine powder is 7% by weight or less, improvement in printability cannot be expected, fine voids 8 are less likely to occur inside the film, and not only the effect of reducing the weight of the base material layer 2 is absent but also the number of voids 8 is small. After the lid receives the heat of steam and returns to the position before being peeled off by the bimetal effect, the lid 1 further curls inward, and a gap 11 is formed between the lid 1 and the container 10 as shown in FIG. Will end up. Further, when the inorganic fine powder 7 is 65% by weight or more, it is impossible to fill the inside of the thermoplastic resin film with this kind of powder. Since the inorganic fine powder (excluding scale-like inorganic fine powder) 7 used here is a powder having a spherical particle diameter or a rough surface, a thermoplastic resin film containing the inorganic fine powder 7 is used as the film. When stretched at a temperature lower than the melting point of, a large number of fine voids (porosity) 8 are formed inside the film by using the inorganic fine powder as a core. The porosity of the surface layer is generally 4 to 55%, preferably 8
~ 45%.

Back Surface Layer The back surface layer 2b is formed of a thermoplastic resin film containing 5 to 70% by weight, preferably 15 to 65% by weight of scale-like inorganic fine powder 9. Scale-like inorganic fine powder 9
The higher the content of B, the higher the flexural modulus of the base material layer 2 and the thinner the base material layer 2. Further, the thermoplastic resin film layer containing the scale-like inorganic fine powder 9 of the back surface layer may or may not be stretched, but the stretched material is thinner and has a stronger base material layer 2. can do. The porosity 8 of the back surface layer 2b is generally 0 to 12%.
Therefore, it is smaller than the porosity of the surface layer 2a. Since the flaky inorganic fine powder 9 has a flat shape, it is difficult to generate fine voids 8 inside the film even when blended in a thermoplastic resin and stretched. 9
Since the heat insulating effect of the back surface layer 2b containing the above is reduced, the heat of the steam transmitted to the metal layer 3 is effectively transferred to the stretched resin film of the front surface layer 2a, and the stretched resin film of the front surface layer 2a is efficiently contracted. Then, the lid 1 can be quickly returned to the state before being opened. In addition, when the inorganic fine powders 7 and 9 are blended separately in this way, the front surface layer 2a and the back surface layer 2b
Both can be filled in a larger amount as compared with the case where the inorganic fine powders 7 and 9 having the same shape are mixed, so that the calories burned in the lid 1 can be reduced and the waste after use can be easily burned. Can be made.

Additional layer If necessary, another resin film may be laminated between the front surface layer 2a and the rear surface layer 2b to form the core layer 2c within a range in which the self-closing property of the lid 1 of the present invention can be achieved. It may be formed.

[0010] The wall thickness of the wall thickness of the surface layer 2a is 2~80μm, preferably 3
40 μm, the core layer 2c has a wall thickness of 0 to 180 μm,
The thickness is preferably 20 to 100 μm, and the thickness of the back surface layer 2b is 3 to 80 μm, preferably 10 to 40 μm.

<Constituent Material> Inorganic Fine Powder (Excluding Scale-like Inorganic Fine Powder) Examples of the inorganic fine powder include calcined clay, calcium carbonate, diatomaceous earth, titanium oxide, and palm curite. The inorganic fine powder is generally 0.03 to
Those having a thickness of 15 μm, preferably 0.1 to 5 μm are used. Scale-like inorganic fine powder The scale-like inorganic fine powder generally has a particle size of 0.0
Examples thereof include talc and mica having a thickness of 3 to 15 μm, preferably 0.1 to 5 μm, and an aspect ratio of 8 to 35, preferably 10 to 20. Thermoplastic resin Examples of the thermoplastic resin include polypropylene, polyethylene, ethylene / propylene copolymer, ethylene / buden-1 copolymer, ethylene / 4-methylpentene-1 copolymer, and propylene / ethylene / buden-1 copolymer. Polymer,
Examples thereof include polystyrene, polyethylene terephthalate, nylon-6, nylon-6,6, nylon-6,10 and nylon-6,12.

<Production of Base Material Layer> The base material layer is the surface layer 2 described above.
Inorganic fine powder for forming a (excluding scale-like inorganic fine powder)
A thermoplastic resin containing 7 was melt-kneaded, extruded into a sheet, cooled, reheated and stretched 3.5 to 7 times in the longitudinal direction by utilizing the peripheral speed difference of the roll to obtain a longitudinally stretched film. After that, then, using a different extruder, a thermoplastic resin containing the scale-like inorganic fine powder 9 for forming the back surface layer 2b is melt-kneaded and extruded into a sheet, and laminated on the back surface side of the longitudinally stretched film. Can be produced by stretching 4 to 12 times in the transverse direction using a tenter.

<Physical Properties> Voids (Porosity) In the container lid 1 of the present invention, the stretched resin film used for the base material layer 2 has a large number of fine voids (porosity) 8 centered on the inorganic fine powder 7. Have Such a stretched resin film has a porosity of 4 to 60%, preferably 8 to 50% calculated by the following formula. Porosity = [(ρ ₀ −ρ) / ρ ₀ ] × 100 ρ ₀ : Density of film before stretching ρ: Density of film after stretching Thermal expansion coefficient In the lid 1 of the container of the present invention, the base material layer 2 is Coefficient of thermal expansion (L
_e ) is important. The coefficient of thermal expansion of such a base material layer 2 is
Thermo-mechanical analyzer "TM-7000" manufactured by Vacuum Riko Co., Ltd.
Using "(trade name), width: 5 mm, span length: 30 m
The test piece of m (L ₀ ) was heated from the temperature of 30 ° C. to the temperature of 80 ° C. over 5 minutes at a heating rate of 10 ° C./minute, and the span length of the test piece at the temperature of 80 ° C. The value (TMA method) obtained by measuring (L) and using the following equation is shown. Thermal expansion coefficient = [(L−L ₀ ) / L ₀ ] × 100 If the value of the thermal expansion coefficient of the base material layer 2 is too large, FIG.
As shown in FIG. 6, the cup noodles self-close before they are ready to eat, and the pulling portion 12 of the lid 1 is excessively caught inside to form a gap 11, or when the cup noodles are too small, as shown in FIG. , The lid 1 is further opened, so 0.40 to 1.
It is preferably 0%, particularly 0.55 to 0.85%
Is preferred. The value of the coefficient of thermal expansion of the base material layer obtained by the TMA method is a value obtained by subtracting the coefficient of thermal contraction of the stretched resin film from the coefficient of thermal expansion of the material resin of the stretched resin film. Tensile elastic modulus The tensile elastic modulus (JIS-K7113) of the base material layer in the direction in which the tensile portion 12 of the base material layer 2 is provided is 13,000 to 6
It is 50,000 kg / cm ² . Since the orientation of the base material layer 2 is exerted on the film by stretching, the elastic modulus of the base material layer 2 is higher than that of the unstretched resin film, and since the scale-like inorganic fine powder 9 is used, Higher rigidity. Therefore, the thickness of the base material layer 2 can be reduced.

<Thickness> The thickness of the base material layer 2 used in the lid 1 of the container of the present invention is generally 20 to 180 μm, preferably 40 to 110 μm.

(B) Adhesive Layer As the adhesive layer 3 laminated to bond the base material layer 2 and the metal layer 4 such as an aluminum foil described later in the lid 1 of the container of the present invention, a urethane prepolymer is used. , Liquid polyester, isocyanate-based, polyester isocyanate-based, polyether isocyanate-based, polyethyleneimine-based, organic titanate-based anchor coating agents, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer and other hot melt adhesives Can be mentioned. Coating type adhesive from 1 to 20 g / m ^2, preferably used in an amount of 2 to 6 g / m ^2. The hot melt adhesive is melt-extrusion laminated with a wall thickness of 8 to 30 μm. Such an adhesive layer is generally 1 to 30 μm, preferably 2
Used with a thickness of ~ 15 μm.

(C) Metal Layer As the metal layer 4 used in the lid 1 of the container of the present invention, a metal foil such as an aluminum foil or an iron foil having a wall thickness of usually 3 to 25 μm can be mentioned. Especially the wall thickness is 6-1
It is preferable to use a 5 μm aluminum foil for the reasons of handling and economical reasons. Further, from the economical aspect, the metal foil is usually used with a thickness smaller than that of the base material layer 2.

(D) Heat-sealable resin layer The heat-sealable resin layer 5 used for heat-sealing the container and the lid 1 in the present invention is a resin having a melting point lower than that of the resin constituting the base material layer 2. Is used. Specific examples of such heat-sealable resin include low-density polyethylene, linear low-density polyethylene, ethylene / vinyl acetate copolymer (preferably ethylene / vinyl acetate copolymer having a vinyl acetate content of 12% by weight or less). , Ethylene / acrylic acid copolymer (preferably ethylene / acrylic acid copolymer having an ethylene content of 65 to 94% by weight), ethylene / methacrylic acid alkyl ester copolymer, Surlyn (metal of ethylene / acrylic acid copolymer Examples thereof include salts, metal salts of ethylene / methacrylic acid copolymers), ethylene / propylene copolymers, ethylene / propylene / butene-1 copolymers, and vinyl chloride / vinyl acetate copolymers. The heat-sealable resin may be extrusion-laminated on a metal sheet such as an aluminum foil, or the resin may be dissolved in a solvent, coated on the aluminum foil using a coater, and dried to obtain a heat-sealable resin. Layers may be provided. The heat-sealable resin layer 5 has a thickness of 2
˜50 μm, preferably 3-40 μm. The heat-sealing of the container 10 and the lid 1 using such a heat-sealable resin can prolong the storage period of the food in the container 1. (2) Pulling part In the container lid 1 of the present invention, as shown in FIG.
A pulling portion 12 for peeling off the lid 1 is provided, but its forming position is important in the present invention.

Since the pulling portion 12 of the lid 1 coincides with the peeling direction α of the lid 1, since the self-closing property of the lid 1 is promoted, the direction β in which the coefficient of thermal expansion of the base material layer 2 is large β It is desirable to provide it in accordance with. Pulling part 1 of the lid 1
If 1 is provided so as to match the direction γ in which the value of the coefficient of thermal expansion is small, the self-closing property decreases. However, since the lid 1 is trimmed from the laminated sheet 6 including the base material layer 2,
In order to reduce material loss, as shown in FIG. 4, an angle θ within 45 degrees with respect to the direction β showing a large heat shrinkage ratio.
Then, the self-closing property of the lid 1 can be maintained to the extent that the self-closing property is slightly reduced.

(3) Thickness The thickness of the lid 1 made of the laminated sheet 6 is 40 to 200 μm.
m, economically 60 to 150 μm.

[II] Manufacture of container with lid (1) Heat-sealing Basically, base material layer 2 / adhesive layer 3 / metal layer 4 / heat-sealing property, which becomes the lid 1 of the container of the present invention formed as described above. The laminated sheet 6 made of the resin layer 5 is provided inside the dried noodles 13, the ingredients 14
Placed on the container 10 containing, usually 100 ~ 160 ℃,
It is preferably heat-sealed at a temperature of 120 to 140 ° C. for 0.1 to 3 seconds. (2) Formation of Pulling Portion In order to form the pulling portion 11 by cutting the container 10 heat-sealed to the laminated sheet 6 into individual containers 10, a substantially circular shape (almost Diameter 150
The lid 1 having a protrusion 11 (pulled portion of about 10 mm) is trimmed. (3) Shrink wrap Next, the sealed container thus obtained is shrink-wrapped to form a product.

[III] Hot Water Supply The lid 1 that is half opened is heated by the steam that has been supplied, and the base material layer 2 is subjected to the thermal expansion of the metal layer 4 of the material forming the lid 1.
Thermal expansion of the container 10 is superior, and the lid 1 automatically returns to the original position (see FIG. 2) due to the bimetal effect, and the container 10
Can be sealed.

[0022]

【Example】

Example 1 Production of base material layer (1) 85% by weight of polypropylene having a melt index (MI) of 0.8 (melting point of 164 ° C.), 5% by weight of high-density polyethylene and calcium carbonate 1 having an average particle size of 1.5 μm
The composition (A) in which 0% by weight was mixed was kneaded by an extruder set at 270 ° C., then extruded into a sheet, and cooled by a cooling device to obtain an unstretched sheet. Then, this sheet was heated again to a temperature of 150 ° C. and then stretched 5 times in the machine direction. (2) Composition (B) in which 60% by weight of polypropylene having MI of 4.0 and 40% by weight of calcium carbonate having an average particle size of 1.5 μm are mixed, and 60% by weight of polypropylene of MI 4.0 and an aspect ratio The mixture (C) with 40% by weight of talc of No. 12 is kneaded by separate extruders, then extruded into a sheet form from a die, and laminated on both sides of the 5 times stretched film of (1). , Three-layer structure (B layer / A layer / C
A laminated film of (layer) was obtained. Then, after cooling the laminated film having the three-layer structure to 60 ° C., the laminated film is heated again to a temperature of about 161 ° C., and then 7.5 times in the lateral direction using a tenter.
Double stretching and annealing at 165 ° C.
Cooled to a temperature of 0 ° C, slit the ears and have a three-layer structure (uniaxial stretching / biaxial stretching / uniaxial stretching), wall thickness 70 μm
A base material layer (B / A / C = 17 μm / 36 μm / 17 μm) was obtained. The void ratio of each layer is (B / A / C = 3
0% / 25% / 5%). The printing surface was applied to the surface of layer B.

Manufacture of Lid The surface of the above-mentioned base material layer is printed, and further, an anchor coating agent of urethane prepolymer is applied to the back surface side so as to be 3 g / m ^2, and an aluminum foil having a thickness of 6 μm is applied to this. Was laminated. On the aluminum foil side of this laminate, an ethylene / vinyl acetate copolymer (vinyl acetate content 5.4% by weight) was extruded at 200 ° C. (thickness: 22%).
μm) and then cooled. This was trimmed so that a tensile portion was formed in the sheet feeding direction (machine tension direction: MD) to obtain a substantially circular lid (diameter 150 m).
m, tensile portion 10 mm).

250 g of dried noodles and 25 g of ingredients in a container made of expanded polystyrene (PSP) having a heat seal content of 1,000 cc and a diameter of about 150 mm.
Then, the lid was heat-sealed by applying pressure at 140 ° C. for 0.5 second.

Evaluation After standing for one day, the pulling part of the lid of the expanded polystyrene container is pulled with a finger to open 2/3 of the lid, and boiling water is heated from this opening (temperature: about 91 ° C.). 600 cc was poured into the container for 5 seconds to measure the self-closing property of the lid.

The results obtained are shown in Table 1.

Example 2 The procedure of Example 1 was repeated, except that the base layer was manufactured as follows. The results obtained are shown in Table 1. Manufacture of base material layer (1) 85% by weight of polypropylene having a melt index (MI) of 0.8 (melting point 164 ° C.), 5% by weight of high-density polyethylene, average particle diameter of 1.2 μm, and aspect ratio of 1
270 of the composition (A) obtained by mixing 10% by weight of talc of No. 2
After kneading with an extruder set to ℃, it was extruded into a sheet and cooled by a cooling device to obtain a non-stretched sheet. Then, this sheet was heated again to a temperature of 150 ° C. and then stretched 5 times in the machine direction. (2) Composition (B) in which 90% by weight of polypropylene having MI of 4.0 and 10% by weight of calcium carbonate having an average particle size of 1.5 μm are mixed, and 95% by weight of polypropylene of MI 4.0 is an average particle. The composition (C) mixed with 5% by weight of talc having a diameter of 1.2 μm was melt-kneaded by a separate extruder, and then melt-extruded into a sheet form from a die, which was (1)
Laminated on both sides of a 5 times stretched film of
A laminated film of A layer / C layer) was obtained. Then, after cooling the laminated film having the three-layer structure to 60 ° C., about 1
It is heated to a temperature of 60 ° C, stretched 7.5 times in the transverse direction using a tenter, annealed at a temperature of 165 ° C, cooled to a temperature of 60 ° C, and the ears are slit into three pieces. Layer structure (uniaxial stretching / biaxial stretching / uniaxial stretching), wall thickness 7
0 μm (B / A / C = 17 μm / 36 μm / 17 μm)
A base material layer of The void ratio of each layer is (B / A /
C = 8% / 10% / 2%). The printed side is B
It was applied to the layer surface.

Example 3 The procedure of Example 1 was repeated except that the substrate layer was produced as follows. The results obtained are shown in Table 1. Manufacture of base material layer (1) Polypropylene having MI of 2 g / 10 min (melting point of about 1
64 ° C) 57% by weight, high-density polyethylene 18% by weight,
A resin composition (A) containing 22% by weight of calcium carbonate having an average particle diameter of 1.5 μm and 3% by weight of titanium oxide was melt-kneaded by an extruder and extruded into a sheet at a temperature of 200 ° C., followed by cooling. After cooling with a device, the sheet was heated again to a temperature of 150 ° C., and then stretched 5 times in the longitudinal direction to obtain a longitudinally stretched film. Then, a mixture (B) of 40% by weight of polypropylene and 60% by weight of talc having an aspect ratio of 15 was melt-kneaded at 200 ° C. in separate extruders, and then melt-extruded in a sheet form from a die, This was laminated on the back surface of a longitudinally stretched film 5 times as large as that of (A), this laminated film was cooled to 60 ° C., and then heated again to a temperature of about 158 ° C., and then 7 times in the transverse direction using a tenter. Stretched and further annealed at a temperature of 164 ° C. for 6
It is cooled to a temperature of 0 ° C., the ears are slit, and the two-layer structure (biaxially stretched / uniaxially stretched) has a thickness of 80 μm (A / B = 5
A base layer made of a two-layer stretched resin film of 2 μm / 18 μm) was obtained. The void ratio of each layer is (A / B = 40
% / 12%). The printing surface was applied to the surface of layer A.

Comparative Example 1 A substrate layer was produced in the same manner as in Example 1 except that it was produced as follows. The results obtained are shown in Table 1. Production of base material layer (1) Composition (A) in which 81% by weight of polypropylene having a melt index (MI) of 0.8% by weight is mixed with 3% by weight of high-density polyethylene and 16% by weight of calcium carbonate having an average particle size of 1.5 μm. Was kneaded with an extruder set at 270 ° C., extruded into a sheet, and cooled by a cooling device,
An unstretched sheet was obtained. Then, this sheet was heated again to a temperature of 140 ° C. and then stretched 5 times in the machine direction. (2) A composition (B) in which 54% by weight of polypropylene having an MI of 4.0 and 46% by weight of calcium carbonate having an average particle size of 1.5 μm are mixed and kneaded in another extruder, It was extruded into a sheet and laminated on both sides of the 5 times stretched film of (1) to obtain a laminated film having a three-layer structure.
Next, after cooling the laminated film having the three-layer structure to 60 ° C., it is heated again to a temperature of about 160 ° C., stretched 7.5 times in the transverse direction using a tenter, and annealed at a temperature of 165 ° C. Then, it is cooled to a temperature of 60 ° C., the ears are slit and a three-layer structure (uniaxial stretching / biaxial stretching / uniaxial stretching) with a wall thickness of 80 μm (B / A / B = 16 μm / 48
A base layer of (μm / 16 μm) was obtained. The void ratio of each layer was (B / A / B = 30% / 33.7% / 30%).

Comparative Example 2 The procedure of Example 1 was repeated except that the substrate layer was produced as follows. The results obtained are shown in Table 1. Manufacture of base layer Synthetic paper "Yupo FPG #" made by Oji Yuka Synthetic Paper Co., Ltd., which is made of multi-layer stretched polypropylene film containing inorganic fine powder
80 "(trade name, wall thickness 80 μm) was used. (Substrate porosity 33%)

Comparative Example 3 The procedure of Example 1 was repeated except that the base material layer was manufactured as follows. The results obtained are shown in Table 1. Production of Base Layer A transparent unstretched polypropylene film “Taiko FHK2” (trade name, wall thickness 60 μm) manufactured by Nimura Sansho Co., Ltd. was used. (Void ratio of base material 0%)

Comparative Example 4 The procedure of Example 1 was repeated except that the base material layer was manufactured as follows. The results obtained are shown in Table 1. Production of base material layer Paper for base material of commercially available cup ramen lid ("Cormorant" (trade name) of Fuji Kako Co., Ltd. (wall thickness 90 μm,
A weighed amount of 82.4 g / m ² )) was used.

Example 4 The procedure of Example 1 was repeated, except that the base material layer was manufactured as follows. The results obtained are shown in Table 1. Manufacture of base material layer (1) 32% by weight of polypropylene having a melt index (MI) of 0.8 (melting point 164 ° C.), 3% by weight of high-density polyethylene and calcium carbonate having an average particle size of 1.5 μm 6
Aspect ratio of 1 with composition (A) in which 5% by weight is mixed
The composition (B) obtained by mixing 20% by weight of talc of No. 2 and 40% by weight of polypropylene are melt-kneaded by separate extruders, respectively, and then supplied to one die and extruded into a sheet shape, and a cooling device. To obtain an unstretched sheet. Then, this sheet was heated again to a temperature of 150 ° C. and then stretched 5 times in the machine direction. Then this is 16
Annealing treatment is performed at a temperature of 5 ° C., cooling is performed to a temperature of 60 ° C., the ears are slit, and the wall thickness is 70 μm (A / B =
A base material layer having a two-layer structure of 52 μm / 18 μm) was obtained. The void ratio of each layer was (A / B = 35% / 3%). The printing surface was applied to the surface of layer A.

[0034]

[Table 1]

[0035]

The lid of the container of the present invention as described above is heated by the steam supplied to the container, whereby the bimetal effect works to automatically and quickly seal the container. There is no need to close the lid and put a weight on it after hot water supply like noodles.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of a lid of a container according to the present invention.

FIG. 2 is a perspective view of the lid and the container of the present invention in a state where hot water is poured into the container and the lid is closed.

FIG. 3 is a perspective view of the lid and the container of the present invention in a state in which the lid is opened, tools are put in the container, and hot water is not poured.

FIG. 4 is a plan view of a laminated sheet when trimming the lid of the container of the present invention from the laminated sheet.

FIG. 5 is an enlarged cross-sectional view of a conventional lid.

FIG. 6 is a perspective view of a conventional lid and container in a state where hot water is poured into the container and the container is further opened.

FIG. 7 is a perspective view of the improper lid and the container in a state in which hot water is poured into the container and is closed too much to be curved inward.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Container lid 2 Base material layer 2a Surface layer 2b Back surface layer 2c Core layer 3 Adhesive layer 4 Metal layer 5 Heat-sealable resin layer 6 Laminated sheet 7 Inorganic fine powder 8 Scale-like inorganic fine powder 9 Void 10 Container 11 Gap 12 Tension Part 13 Dry noodle 14 Tool 15 Printing α Peeling direction β Direction with large value of thermal expansion coefficient γ Direction with small value of thermal expansion coefficient θ Angle within 45 ° to direction β showing large thermal contraction rate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Funato 23, Towada, Kamisu-machi, Kashima-gun, Ibaraki Prefecture Okaka Synthetic Paper Co., Ltd., Kashima Plant (72) Inventor Takashi Miyaji, Kamisu, Kashima-gun, Ibaraki Prefecture 23, Towada, Oji Petrochemical Synthetic Paper Co., Ltd., Kashima Plant (72) Inventor, Yukio Obama 826, Hagien, Fukuda, Chigasaki City, Kanagawa Tokai Metal Co., Ltd., Chigasaki Plant (72) Inventor, Yamada Wan, 826 Hagiden, Chigasaki, Kanagawa, Kanagawa Prefectural Tokai Metals Co., Ltd., Chigasaki Plant (72) Inventor, Toshiaki Watanabe 826, Hagien, Chigasaki, Kanagawa, Chigasaki, Tokai Metals (72) Inventor Chiaki Kanai 826 Fukuda, Hagien, Chigasaki City, Kanagawa Prefecture Tokai Metal Co., Ltd. Chigasaki Plant

Claims (1)

[Claims] 1. A lid comprising a laminated sheet of a base material layer / adhesive layer / metal layer / heat-sealable resin layer, the surface of which is printed, provided with the following requirements (1) and (2). A container lid characterized by the following. (1) Fine voids inside a film made of a stretched product of a thermoplastic resin film containing 8 to 65% by weight of an inorganic fine powder (excluding scale-like inorganic fine powder) on which the substrate layer is printed. And a back surface layer made of a thermoplastic resin film containing 5 to 70% by weight of scale-like inorganic fine powder. (2) The pulling portion of the lid for peeling the heat-sealed lid from the container, the base material layer is heated from a temperature of 30 ° C to a temperature of 80 ° C over 5 minutes at a heating rate of 10 ° C / minute. It is provided so as to match the direction of the base material layer having a large coefficient of thermal expansion.