JP2003095313A - Heat-unsealing type sealable packaging bag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealable packaging bag which can safely and reliably perform the heating while retaining water content in a frozen food removed by the microwave. SOLUTION: The packaging bag is formed of a laminate film comprising a base layer and a thermal-bonding layer. The cohesive-destructibility printing using a photo-gravure ink containing at least one kind of nitrocellulose, polyurethane and polyamide as a resin composition is performed between the base layer and the thermal-bonding layer of a thermally-bonded part. The bag is heated by the microwave in a microwave oven to perform the cohesive destructibility of the printed layer, and then, the thermally-bonding layer is broken to form deaeration holes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a high sealing property during storage and distribution, withstands low-temperature storage, and the steam pressure generated when heated by microwaves causes cohesive destruction of the printed portion and breaks the bag. The present invention relates to a heat-opening type sealed packaging bag in which the bag is safely broken by wave heating and the contents are heated in the presence of sufficient steam, and a method for opening the heat-opening type sealed packaging bag using the same.

[0002]

2. Description of the Related Art Cooked foods generally have a high water content and are apt to rot when left at room temperature. Therefore, a method has been adopted in which the bag is hermetically sealed in a durable bag that is not easily broken, and preferably frozen. Even if this is thawed and heated, the original deliciousness is not generally expressed. Recently, microwave heating, which has been widely adopted, has an advantage that it can be thawed in a short time, but it has a drawback that it cannot be moistened because it evaporates much water. Therefore, the sealed bag has a part that is easy to break,
Various techniques have been developed for breaking the bag when the water vapor pressure in the bag is increased by heating and sufficient moisture can be supplied to the food, and then heating while evaporating the water vapor for a certain period.
These include a method of locally weakening the fusion strength of the fusion zone,
There is a method of forming a bottleneck for the release of water vapor.

[0003]

However, if the timing of water vapor release is late, the vapor pressure inside rises too much and a loud sound that is close to an explosion is emitted, causing an accident in which the contents are scattered. On the other hand, if it is too early, the food inside will be heated to a dry state with little water content, and the original taste cannot be enjoyed. Therefore, there has been a demand for a technique for surely breaking the bag when a certain water vapor pressure is reached.

[0004]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems, and has a constitution comprising a laminated film obtained by laminating a base material layer and a heat-fusible layer. Between the base material layer and the heat-fusible layer, a bag subjected to cohesive failure printing using a gravure ink containing at least one of nitrification cotton, polyurethane or polyamide as a resin component is placed in a microwave oven in a microwave oven. It is characterized in that the printed layer is coagulated and destroyed by wave heating, and then the heat-fusible layer is ruptured to form deaeration pores.

That is, a tough base film such as nylon, polyester, stretched polypropylene or the like is used in order to endure storage under circulation. Since these films do not have a heat-fusible property, it is difficult to use them as a bag material as they are, and a heat-fusible layer such as linear low density polyethylene (hereinafter referred to as LLDPE) is laminated and used. The present invention is one in which the base material layer at the portion which becomes the heat-sealing portion when the bag is manufactured is preferably printed at several places and the heat-sealing layer is laminated by a conventional method. The present invention is characterized by using a printing ink that causes cohesive failure of the formed film as the printing ink. A part of the heat-sealed part that is connected to the broken part due to cohesive failure of the ink film opens and forms a degassing hole,
Water vapor is released from the deaeration holes, and the water vapor pressure inside the bag gradually decreases.

According to the present invention which utilizes the cohesive failure of the ink film, the peel strength of the heat-sealed portion is large unless heated,
It is unlikely that the bag will lose its hermeticity during the distribution process. Further, during microwave heating with a microwave oven, there is no risk of explosive bag breakage due to excessive delay of bag breakage due to cohesive failure of the ink film itself. It suffices to simply print an ink that is prone to cohesive failure on the portion to be heat-sealed.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION As the base material layer in the present invention, a tough film such as nylon, polyester or stretched polypropylene, particularly a nylon film is preferably used. These films have low air permeability and high thermal softening temperature, and are excellent as food packaging films. On the other hand, since the heat softening temperature is high, heat fusion cannot be performed as it is, and a heat fusible layer having a low heat softening temperature is always laminated and used. Examples of the heat-fusible layer include resins such as polyethylene, unstretched polypropylene and ethylene-vinyl acetate copolymer, and among them, LLDPE is preferable. Examples of the lamination method include dry lamination in which films are adhered to each other with an adhesive, extrusion lamination in which a molten heat-fusible resin is extruded onto a base material, and the like. In dry lamination, solvent-based or solvent-free polyurethane adhesives can be used.

The printing ink is mainly composed of a pigment, a resin and a solvent. Depending on the printing method, an ink having physical properties suitable for the printing method is used, but gravure printing is preferably used in the present invention. As the pigment, zinc oxide, zinc sulfide,
In addition to extender pigments such as barium sulfate, calcium carbonate and silica, pigments such as titanium oxide and zinc white may be used alone or in combination of two or more. The total blending amount of the extender pigment and the pigment is 20 to 70% by weight, preferably 30 to 60% by weight of the ink.
% By weight. If it exceeds 70% by weight, the strength of the ink film is insufficient, and if it is less than 20% by weight, the shielding power of the ink film is insufficient.

Solvents used for ink production include aromatic hydrocarbon solvents such as toluene and xylene, alcohol solvents such as methanol, ethanol, isopropanol and n-butanol, acetone, methyl ethyl ketone,
Ketone solvent such as methyl isobutyl ketone, ethyl acetate,
There are ester solvents such as butyl acetate, and these are used alone or in admixture of two or more. The amount of gravure ink used is 8 to 25% by weight.

The resin component of the printing ink used in the present invention contains at least one of nitrification cotton, polyurethane or polyamide. Nitrified cotton is a nitrate ester obtained by reacting natural cellulose with nitric acid, and the three hydroxyl groups in the 6-membered ring of the anhydrous glucopyranose group in the natural cellulose are replaced with nitrate groups. The degree of nitrification (nitrogen content) and the degree of polymerization are not particularly limited, but those having an average degree of polymerization of 35 to 400 are preferably used in consideration of the production of printing ink and printability. If the average degree of polymerization is less than 35, the film strength of the ink is lowered and the scratch resistance and the scuff resistance are lowered, which is not preferable. If the average degree of polymerization exceeds 400, the solubility in a solvent, the low temperature stability of the ink, and the compatibility with polyamide are deteriorated, which is not preferable.

Polyurethanes used in the printing ink of the present invention include polymer diol compounds, organic diisocyanate compounds and chain extenders, and those obtained by stopping the reaction with a reaction terminator if necessary. Examples of the polymer diol compound include various polymer diol compounds in addition to the polyether diol compound and the polyester diol compound. As the organic diisocyanate compound, any of an aromatic diisocyanate compound, an aliphatic diisocyanate compound and an araliphatic diisocyanate compound can be used. As the chain extender, diol compounds such as ethylene glycol and propylene glycol, or diamine compounds such as ethylenediamine and propylenediamine can be used. Examples of the reaction terminator used as necessary include monoamines such as n-butylamine and monoethanolamine, and monoalcohols such as methanol and propanol.

The weight average molecular weight of the polyurethane used in the ink is preferably 10,000 to 150,000.
When the molecular weight of polyurethane is less than 10,000, the blocking resistance of the ink obtained and the adhesion to the original fabric are deteriorated. On the other hand, when it exceeds 150,000, the dispersibility of the pigment and the redissolvability of the ink are deteriorated, which is not preferable. The weight average molecular weight can be determined by gel permeation chromatography (GPC) or a relational expression between the intrinsic viscosity of the polymer and the weight average molecular weight. The skeletal structure of polyurethane may be branched or linear having a branch. These resins can be used alone or in combination with other resins.

Examples of the polybasic acid which is a raw material of the polyamide used for the ink include adipic acid, sebacic acid, isophthalic acid, terephthalic acid, trimellitic acid, cyclohexanedicarboxylic acid and polymerized fatty acid. A monocarboxylic acid may be used in combination with the polybasic acid. Examples of the monocarboxylic acid used in combination include acetic acid, propionic acid, lauric acid, palmitic acid, benzoic acid, cyclohexanecarboxylic acid and the like. Examples of the polyvalent amine include ethylenediamine, diethylenetriamine, triethylenetetramine, 1,2-diaminopropane, 1,3-diaminopropane, hexamethylenediamine, xylylenediamine and isophoronediamine.

Printing is generally performed on the substrate layer, and the heat-fusible layer is laminated on the printed surface of the substrate layer. As a result, the printed surface is not exposed on the surface of the laminated film, and the printed surface is protected by the base material layer and the heat-fusible layer. Fusing is performed by heat-fusing the heat-fusible layers of the two laminated films, so that the two heat-fusible layers are bonded to each other to form the base material layer, the ink film layer, and the heat-fusible layer. , An ink film layer (not present when printed on only one laminated film) and a base material layer. When printing this ink, it is generally adjusted to an appropriate printing viscosity using a diluting solvent before use.

The cohesive failure in the present invention means delamination of the ink film layer, delamination between the substrate layer and the ink film layer, or delamination between the ink film layer and the heat-fusible layer. When the ink layer undergoes cohesive failure, the film that protects the heat-fusible layer disappears, and the heat-fusible layer in this area easily breaks due to the water vapor pressure inside the bag, and passes through the cohesively damaged ink film layer to release pores. Water vapor is released and water vapor is released. Cohesive failure is likely to occur when the cohesive force of the ink film layer is small, and is most likely to occur when the resin component forming the ink is nitrified cotton. In addition, polyurethane and polyamide can be preferably used because the heat resistance is lowered by adding a large amount of an extender pigment or a pigment such as titanium dioxide.

[0016]

Example A cohesive failure coating was printed on a horizontal fusion-bonded portion of a stretched nylon having a thickness of 15 μm in a vertical stripe pattern with a printing portion of 1 cm and a non-printing portion of 1 cm. Gravure ink composition is titanium dioxide 50% by weight, polyamide 12% by weight, nitrified cotton 6
% And the solvent was 32%. The solvent contained isopropanolamine, ethyl acetate and toluene at a ratio of 5: 5: 7, respectively. LLDPE on the printed surface of stretched nylon
Was extruded to a thickness of 35 μm and laminated to produce a laminated film.

Using this laminated film, a three-side sealed bag having a width of 12 cm and a length of 18 cm was manufactured. Vertical seal width 1c
m, leaving a 5 mm non-fused part on the outside. The width of the horizontal seal is about 8 mm, and a non-fused portion of 5 mm is left outside. A printing section was provided which penetrates the horizontal fusion-bonded portion and reaches the outside through the entire horizontal fusion-bonded portion. The inside was filled with 6 pieces of shumai, and stored frozen for 14 days. Before eating, the Shumai bag was put in a microwave oven while being frozen and heated. The internal temperature gradually increased, and when it reached a certain temperature, the bag suddenly inflated like a balloon, and after this state continued for several seconds, steam started to be released while the bag was inflated with a low plosive sound. After heating for about 10 seconds in this state, the contents were taken out to obtain warm pork mai having the same taste as when steamed in a steaming basket. At the horizontal fusion-bonded portion of the bag, cohesive failure occurred in a mountain shape extending from the inside of the bag to the outside at several points on the printed portion, and the heat-fusible layer was torn at a part of the cohesive failure site.

[0018]

According to the present invention, printing in which the cohesive force of the heat-sealed portion is intentionally reduced is made possible to safely and reliably perform heating by microwaves without releasing moisture of frozen food.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B65D 81/34 B65D 81/34 U // B65D 33/01 33/01 F term (reference) 3E064 BA26 BA29 BA30 BA36 BA54 BB03 EA30 HD02 HD10 HE01 3E067 AB01 BA12A BB15A BB16A BB25A BC03A EE02 FA01 FC01 GB02 GD10 3E086 AD01 BA04 BA15 BA33 BB02 CA01

Claims (6)

[Claims] 1. A bag made of a packaging material obtained by laminating a base material layer and a heat-fusible layer, wherein printing is performed between the base material layer and the heat-fusible layer at a fusion-bonding site. A heat-opening type sealed packaging bag, wherein a film formed by the printing ink undergoes cohesive failure by heating, and the heat-fusible layer is broken to form deaeration holes. 2. The heat-openable sealed packaging bag according to claim 1, wherein a cohesive failure gravure printing ink is used as the printing ink. 3. The heat-opening mold according to claim 2, wherein at least one selected from the group consisting of nitrification cotton, polyurethane and polyamide is contained as a resin component constituting the cohesive failure gravure printing ink. Sealed packaging bag. 4. The heat-openable sealed packaging bag according to claim 2, wherein the cohesive failure gravure printing ink contains an extender pigment, titanium dioxide, or an extender pigment and titanium dioxide. 5. The heat-openable sealed packaging bag according to claim 1, wherein the base film is a nylon film. 6. A laminated film formed by laminating a base material layer and a heat-fusible layer, wherein cohesive destructive printing is applied between the base material layer and the heat-fusible layer at a fusion-bonding site. A method for opening a heat-sealing type sealed packaging bag, comprising heating the bag by microwave to coagulate and destroy the printed layer, and then to break the heat-fusible layer to form deaeration holes.