JPH06239375A - Cover of container - 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) A surface layer having a number of fine voids inside a film made of a uniaxially stretched product of a thermoplastic resin film containing an inorganic fine powder having the surface of the substrate layer printed thereon, and a core made of a biaxially stretched resin film. A laminate comprising a layer and a back surface layer of a thermoplastic resin film having no voids inside the film or having voids having a void ratio lower than that of the surface even if there are voids. (2) The pulling part of the lid used to peel off the heat-sealed lid from the container, the base material layer is heated at a temperature rising rate of 10 ° C./minute for 5 minutes from 30 ° C. to 80 ° C. It must be installed so as to match the direction in which the coefficient of thermal expansion is large when heated.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention is capable of heat-sealing used in containers for instant cup noodles, cup sushi, cup soup, cup miso soup, etc., which are eaten after pouring hot water into the container and holding it for a certain period of time. Regarding the lid of the container.

[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 By stopping with tape, heat in the container is prevented from escaping to improve thermal 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 a container used for such instant foods, polystyrene paper, a high-impact polystyrene sheet, or a laminated sheet of nylon and polyethylene, which have a good heat retaining property, is usually cup-assisted by plug-assist vacuum forming or pressure forming. A molded product, a foam polystyrene cup obtained by in-mold bead foam molding, a container obtained by injection molding polypropylene, and the like are used. As the lid used for the above-mentioned container, as shown in FIG. 5, a high-quality paper having a print 14 on its surface is used as the base material layer 2, and a low-density polyethylene, ethylene / acrylic acid copolymer An adhesive 3 extruded and coated with a molten resin film, or an adhesive layer 3 coated with a urethane-based or polyester-based liquid adhesive (so-called anchor coating agent), and aluminum having a thickness of 6 to 15 μm attached thereto. A foil layer 4 and a heat-sealing layer 5 on which a low-melting-point polyethylene (low melting point (80 to 135 ° C.) resin such as ethylene / vinyl acetate copolymer is extruded or melted in a solvent and applied onto the aluminum foil layer. , A laminated sheet 6 having a four-layer structure with heat sealability
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 Even if the lid is not so large that it curls inward, it was found that the lid of the container can be automatically closed by laminating it with a stretched resin film having a specific structure. Thus, the present invention has been completed. That is, the lid of the container of the present invention is a lid having a thickness of 40 to 200 μm, which is formed of a laminated sheet of a substrate layer / adhesive layer / metal layer / heat-sealable resin layer, the surface of which is printed. It is characterized by having the requirements (1) and (2). (1) A surface layer having a number of fine voids inside a film made of a uniaxially stretched product of a thermoplastic resin film containing an inorganic fine powder having the surface of the substrate layer printed thereon, and a core made of a biaxially stretched resin film. A laminate comprising a layer and a back surface layer of a thermoplastic resin film having no voids inside the film or having voids having a void ratio lower than that of the surface even if there are voids. (2) The pulling part of the lid used to peel off the heat-sealed lid from the container, the base material layer is heated at a temperature rising rate of 10 ° C./minute for 5 minutes from 30 ° C. to 80 ° C. It must be installed so as to match the direction in which the coefficient of thermal expansion is large when heated.

[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 Layer As shown in FIG. 1, the base layer 2 used in the lid 1 of the container of the present invention has a surface layer 2a / core layer 2b / back surface layer 2c of at least a three-layer structure. ing.

<Structure of Substrate Layer> Surface Layer The surface layer 2a is formed of a uniaxially stretched film of a thermoplastic resin containing 8 to 65% by weight of the inorganic fine powder 7 for printing. The surface layer has fine voids (porosity) 8 in the film. Core Layer The core layer 2b contains the inorganic fine powder 7 in an amount of 0 to 35 in order to impart strength balance in the longitudinal direction and the transverse direction to the entire base material layer 2.
It is formed from a biaxially stretched film of a thermoplastic resin, which is contained in an amount of 3% by weight, preferably 3 to 25% by weight. The core layer 2
b may or may not have fine voids 8 in the film. Back Surface Layer The back surface layer 2c is formed of a thermoplastic resin film having a porosity (0% may be smaller) than the porosity of the front surface layer 2a. The back surface layer 2c may or may not have fine voids in the film. Further, the back surface layer 2c may or may not be stretched and oriented. Additional layer If necessary, another layer may be provided between the surface layer 2a and the core layer 2b, and / or between the core layer 2b and the back surface layer 2c, within a range capable of achieving the self-closing property of the lid of the present invention. A resin film may be present. Further, another resin film may be laminated on the surface of the back surface layer 2c which is in contact with the adhesive.

[0008] thickness of the thick the surface layer 2a is 2 to 50 [mu] m, preferably 2 to
30 μm, and the thickness of the core layer 2b is 10 to 180 μm.
m, preferably 40 to 100 μm, and the thickness of the back surface layer 2c is 3 to 50 μm, preferably 10 to 40 μm. Further, the thickness of the core layer 2b is 20 to 9 of the entire base material layer 2.
It is preferably 5%. The thickness of the base material layer 2 is generally 20 to 180 μm, preferably 40 to 110 μm.

<Constituent Material> Thermoplastic Resin As the above-mentioned thermoplastic resin, high density polyethylene, polypropylene, propylene / ethylene copolymer, propylene / ethylene / buden-1 copolymer, propylene / buden-1 copolymer, Propylene-4-methylpentene-1
Examples thereof include copolymers, nylon-6, nylon-6,6, nylon-6,10, nylon-6,12, polyethylene terephthalate, polycarbonate and polystyrene.

Inorganic fine powder As the above inorganic fine powder, calcium carbonate, calcined clay, diatomaceous earth, talc, mica, palm curite, titanium oxide and the like can be mentioned, and the inorganic fine powder generally has a particle size of 0. 03 to 15 μm, preferably 0.1 to 5 μm
m is used.

<Physical Properties of Substrate Layer> Porosity (void) The porosity (void) of each layer constituting the above-mentioned substrate layer 2 is important in the present invention, and as such a porosity (void) of each layer film. Has a porosity of the surface layer 2a of 4 to 55.
%, Preferably 8-45%. Further, the porosity of the core layer 2b is 0 to 32%, preferably 8 to 25%, which is smaller than the porosity of the surface layer 2a. Furthermore, the back surface layer 2c
Has a porosity of 0 to 50%, preferably 0 to 35%, which is smaller than the porosity of the surface layer 2a. The porosity of the back surface layer 2c may be the same as that of the core layer 2b, or may be large or small. The porosity (void) of each layer film is generated by stretching the film containing the inorganic fine powder 7, and a large number of fine voids 8 are formed inside the film with the inorganic fine powder 7 as a core. A large number of fine cracks are generated on the film surface, which improves the adhesion of printing ink. The porosity (void) of each layer film is calculated by the following equation. Porosity = [(ρ ₀ −ρ) / ρ ₀ ] × 100 ρ ₀ : Density of film before stretching ρ: Density of film after stretching

Thermal Expansion Coefficient The pulling portion 10 provided on the lid 1 of the container 9 of the present invention is
As shown in FIG. 2, it is important to provide the base material layer 2 so as to match the direction α in which the coefficient of thermal expansion (L _e ) of the base material layer 2 is large. The coefficient of thermal expansion of such a base material layer was measured using a thermomechanical analyzer "TM-7000" (trade name) manufactured by Vacuum Riko Co., Ltd.
A test piece having a length of 5 mm and a span length of 30 mm (L ₀ ) was heated at a temperature rising rate of 10 ° C./minute for 5 minutes from a temperature of 30 ° C. to 80 ° C.
The temperature of the test piece was increased to 80 ° C., and the span length (L) of the test piece at the temperature of 80 ° C. was measured.
Law) is indicated. Thermal expansion coefficient = [(L−L ₀ ) / L ₀ ] × 100 If the value of the thermal expansion coefficient of the base material is too large, as shown in FIG. 7, the cup noodles self-close before they are ready to eat. Then, the pulling portion 10 of the lid 1 is excessively rolled inward to form a gap 11, or if it is too small, the lid 1 is further opened as shown in FIG. 6, so 0.40 to 1.0
%, Particularly preferably 0.55 to 0.85%. 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.

[0013] Tensile elongation modulus of tensile modulus portion direction of the base layer provided (JI
S-K7113) is 10,000-40,000 kg
/ Cm ² , preferably 15,000-30,000 kg
/ Cm ² . Since the orientation of the base layer is exerted on the film by stretching, the elastic modulus shows a value higher than that of the unstretched resin film. Therefore, the thickness of the base material layer can be reduced.

<Manufacture of Base Material Layer> The base material layer 2 is obtained by melt-kneading the resin for forming the core layer 2b, extruding it into a sheet, cooling it, and reheating it in the longitudinal direction by utilizing the peripheral speed difference of the roll. 3.5-7
Double stretching is performed to obtain a longitudinally stretched film. Then, the resin for the surface layer and the resin for the back surface layer are melt-kneaded using separate extruders, each is extruded into a sheet shape, and laminated on the front and back surfaces of the longitudinally stretched film, respectively, and this is laterally applied using a tenter. It is produced by stretching 4 to 12 times. Further, each layer is prepared in advance, and urethane prepolymer, anchor coating agent for liquid polyester, ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, Surlyn (ethylene / acrylic acid copolymer It may be produced by bonding and laminating with a hot melt adhesive such as a metal salt, a metal salt of ethylene / methacrylic acid copolymer), an ethylene / acrylic acid ester copolymer, or low density polyethylene.

(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, low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, etc. Mention may be made of hot melt adhesives. The coating type adhesive is 1-2
It is used in an amount of 0 g / m ² , preferably 2-6 g / m ² . The hot melt adhesive is melt-extrusion laminated with a wall thickness of 8 to 30 μm. Such adhesive layers are generally 1-3
It is used in a thickness of 0 μm, preferably 2 to 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. From the economical aspect, the metal layer 4 is usually used in the same thickness as the base material layer 2 or in a thickness thinner than the base material layer 2.

(D) Heat-sealable resin layer The heat-sealable resin layer 5 used for heat-sealing the lid 1 of the container and the flange portion 9a of the container 9 in the present invention is a resin constituting the base material layer 2. A resin having a melting point lower than that of 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 ethylene content of 65 to 94% by weight), ethylene / methacrylic acid ester copolymer, ionomer (metal salt of ethylene / acrylic acid copolymer , A metal salt of ethylene / methacrylic acid copolymer),
Examples thereof include ethylene / propylene copolymer, ethylene / propylene / butene-1 copolymer, vinyl chloride / vinyl acetate copolymer and the like. 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 has a wall thickness of 2 to 50 μm, preferably 3 to 4
It is 0 μm. The heat-sealing of the container 9 and the lid 1 using such a heat-sealable resin can prolong the storage period of the food in the container 9.

(2) Pulling portion In the lid 1 of the cup noodle container of the present invention, as shown in FIG. 2, a pulling portion 10 for peeling off the lid 1 is provided. Is important in the present invention. Since the pulling portion 10 of the lid 1 coincides with the peeling direction β of the lid 1, since the self-closing property of the lid 1 is promoted, the direction α in which the coefficient of thermal expansion of the base material layer 2 is large α It is desirable to provide it in accordance with. If the pulling portion 10 of the lid 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, as shown in FIG. 4, since the lid 1 is trimmed from the laminated sheet 6 made of the base material layer 2, the peeling direction β of the lid 1
Is an angle θ within 45 degrees with respect to the direction α showing a large heat shrinkage in order to reduce material loss,
The self-closing property of the lid 1 can be maintained to a degree that the self-closing property is slightly reduced.

(3) Thickness The thickness of the lid 1 made of the laminated sheet 6 is generally 40 to 2
00 μm, 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 has dried noodles 12 and ingredients 13 inside.
A large number of the containers 9 containing the above are placed side by side, and heat-sealed at a temperature of usually 100 to 160 ° C., preferably 120 to 140 ° C. for 0.1 to 3 seconds.

(2) Formation of pulling part The container 9 heat-sealed to the above-mentioned laminated sheet 6 is separated into individual containers 9
A substantially circular shape (for example, a diameter of 150 m) in which a protruding portion 10 is formed in part in order to form the pulling portion 10 by separating each
The lid 1 having the protruding portion 10 (pulling portion) of about 10 mm with respect to m is trimmed.

(3) Shrink packaging Next, the sealed container thus obtained is shrink-wrapped to form a product.

[III] Hot Water Supply As shown in FIG. 3, the half-opened lid 1 is heated by the steam supplied, and the base layer 2 is heated by the thermal expansion of the metal layer 4 of the material forming the lid 1. The expansion is superior, and the bimetal effect automatically returns the lid 1 to the original position, so that the container 9 can be sealed as shown in FIG.

[0024]

【Example】

Example 1 Production of base material layer (1) 81% by weight of polypropylene having a melt index (MI) of 0.8 (melting point of 164 ° C.), 3% by weight of high-density polyethylene and 1% of calcium carbonate having an average particle size of 1.5 μm
The composition (A) containing 6% by weight was kneaded by an extruder set at 270 ° C., 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) Separately, a composition (B) in which 55% by weight of polypropylene having an MI of 4.0, 45% by weight of calcium carbonate having an average particle size of 1.5 μm and a polypropylene (C) having an MI of 4.0 are separated. After melt-kneading with an extruder, this was extruded into a sheet form from a die and laminated on both sides of the (1) 5-fold stretched film to obtain a laminated film having a three-layer structure. Then, after cooling the laminated film having the three-layer structure to 60 ° C., it is heated again to a temperature of about 175 ° 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., and the ears are slit to form a three-layer structure (uniaxially stretched / biaxially stretched / uniaxially stretched) having a wall thickness of 80 μm (B / A / C = 20 μm / 40 μm).
m / 20 μm) was obtained. The void ratio of each layer was (B / A / C = 5.2% / 14.2% / 0%). The printing is performed on the B layer side.

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 dry laminated. An ethylene / vinyl acetate copolymer (vinyl acetate content 5.4% by weight) was extrusion laminated (wall thickness: 22 μm) at a temperature of 200 ° C. on the aluminum foil side of this laminate, and then cooled. This was trimmed so that a tension portion was formed in the sheet feeding direction (machine tension direction: MD) to obtain a substantially circular lid (diameter 150 mm, tension portion 10 mm).

Heat seal 250 g of dried noodles and 25 g of ingredients were placed in a container made of expanded polystyrene having a capacity of 1,000 cc and a diameter of about 150 mm, and the lid was heat-sealed by applying pressure at 140 ° C. for 0.5 seconds. .

Evaluation After standing for one day, the pulling portion 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 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) 81% by weight of polypropylene having a melt index (MI) of 0.8 (melting point of 164 ° C.), 3% by weight of high-density polyethylene and calcium carbonate having an average particle size of 1.5 μm 1
The composition (A) containing 6% by weight was kneaded by an extruder set at 270 ° C., 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 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 diameter of 1.5 μm are mixed, and a high density of 80% by weight of a polypropylene of MI 4.0 Polyethylene 10% by weight and average particle size 1.
The composition (C) mixed with 5% by weight of calcium carbonate (10% by weight) and the polypropylene having MI of 2 were melt-kneaded by separate extruders, and then melt-extruded into a sheet from a die, Laminated film on both sides of the 5 times stretched film of 1) and having a four-layer structure (B layer / A layer / C layer / D)
Layer) was obtained. Then, this laminated film having a three-layer structure
After cooling to 0 ° C., it is heated again to a temperature of about 160 ° C. and stretched 7.5 times in the transverse direction using a tenter.
Annealing treatment at a temperature of 5 ° C., cooling to a temperature of 60 ° C., slits in the ears, and a four-layer structure (uniaxial stretching / biaxial stretching / uniaxial stretching / uniaxial stretching) with a wall thickness of 80 μm (B /
A / C / D = 15 μm / 46 μm / 16 μm / 4 μm)
A base material layer of The void ratio of each layer is (B / A / C
/D=30%/29.7%/2.0%/0%). The printing surface was applied to the surface of layer B.

Example 3 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. 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 22% by weight,
A resin composition (A) containing 18% by weight of calcium carbonate having an average particle size 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 to a temperature of 60 ° C. with a device, the sheet was heated again to a temperature of 150 ° C., and then stretched 5 times in the machine direction to obtain a stretched film. (2) After melt-kneading a mixture (B) of 85 parts by weight of propylene / butene-1 / ethylene copolymer (melting point 142 ° C.) and 5 parts by weight of calcined clay at a temperature of 200 ° C. in separate extruders. , Melt-extruding this into a sheet from a die,
By laminating on the back surface of the 5 times stretched film of (1), a laminated film (A layer / B layer) having a two-layer structure was obtained. Then, after cooling the laminated film having the two-layer structure to 60 ° C.
Heated to a temperature of 8 ° C, stretched 7 times in the transverse direction using a tenter, annealed at a temperature of 165 ° C, cooled to a temperature of 60 ° C, slit the ears and double layer. Structure (biaxially stretched / uniaxially stretched), wall thickness 80 μm (A /
B = 70 μm / 10 μm) was obtained. The void ratio of each layer was (A / B = 33% / 0%). 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) The 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 melt-kneaded by separate extruders, Melt extruded into a sheet from a die and laminated on both sides of the 5 times stretched film of (1) to form a three-layer structure (B layer / A layer /
A laminated film of B layer) was obtained. Then, after cooling the laminated film having the three-layer structure to 60 ° C., it is again heated to about 160 ° C.
Heat up to the temperature of 7. and use a tenter to move laterally 7.
Stretched 5 times, annealed at a temperature of 165 ° C,
Cooled to a temperature of 60 ° C, slit the ears and have a three-layer structure (uniaxial stretching / biaxial stretching / uniaxial stretching), wall thickness 80 μm
A base material layer (B / A / B = 16 μm / 48 μm / 16 μm) was obtained. The void ratio of each layer is (B / A / B = 3
0% / 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 substrate layer was produced 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.

[0034]

[Table 1]

[0035]

EFFECT OF THE INVENTION The lid of the container of the present invention is heated by the steam supplied to the container, whereby the bimetal effect works and the container can be automatically sealed. There is no need to close the lid after the hot water is supplied and place a weight.

[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 Biaxially stretched resin microporous film 2b, 2c Uniaxially stretched resin microporous film 3 Adhesive layer 4 Metal layer 5 Heat-sealable resin layer 6 Laminated sheet 7 Inorganic fine powder 8 Void 9 Container 10 Tensile Part 11 Gap 12 Dry noodle 13 Tool 14 Printing α Peeling direction β Direction with high value of thermal expansion coefficient γ Direction with low value of thermal expansion coefficient θ Angle within 45 degrees to direction β showing high thermal contraction rate

Front page continuation (72) Inventor Takashi Funato 23 Tozada, Kamisu-cho, Kashima-gun, Ibaraki Prefecture Towada 23 Kashima Plant, Oji Petrochemical Synthetic Paper Co., Ltd. (72) Takashi Miyaji, Kamisu-cho, Kashima-gun, Ibaraki Prefecture 23 Wada Okaka Kasei Synthetic Paper Co., Ltd., Kashima Plant (72) Inventor Yukio Kohama 826 Hagiden, Higaenji, Chigasaki City, Kanagawa Prefecture Tokai Metal Co., Ltd., Chigasaki Plant (72) Inventor Yamada Kazunori Kanagawa Chigasaki City, Chigasaki 826 Fukada, Tokai Metal Co., Ltd. inside the Chigasaki Plant (72) Inventor Toshiaki Watanabe 826 Hagiden, Chigasaki City, Kanagawa Tokai Metal Co., Ltd. inside the Chigasaki Plant (72) Inventor Chi Kanai Autumn 826 Fukada, Hagien, Chigasaki, 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) A surface layer having a number of fine voids inside a film made of a uniaxially stretched product of a thermoplastic resin film containing an inorganic fine powder having the surface of the substrate layer printed thereon, and a core made of a biaxially stretched resin film. A laminate comprising a layer and a back surface layer of a thermoplastic resin film having no voids inside the film or having voids having a void ratio lower than that of the surface even if there are voids. (2) The pulling part of the lid used to peel off the heat-sealed lid from the container, the base material layer is heated at a temperature rising rate of 10 ° C./minute for 5 minutes from 30 ° C. to 80 ° C. It must be installed so as to match the direction in which the coefficient of thermal expansion is large when heated.