JP6981899B2 - Cover film for microwave-heated foods - Google Patents

Description

The present invention relates to a cover film for microwave-heated foodstuffs, which can suppress a temperature rise of foodstuffs when microwave-heated by a microwave oven.

Microwave ovens are rapidly becoming widespread as convenient cooking utensils that can be heated easily and safely, and have become indispensable for modern life.

By the way, when heating foodstuffs with a microwave oven, it is common practice to put various foodstuffs such as lunch boxes in one plastic container and heat them at the same time. The principle of heating with a microwave oven is that water molecules contained in foods are vibrated by the action of microwaves to generate heat. Therefore, when heating various foods at the same time in this way, the water contained in each food is contained. Due to the difference in the amount, the temperature rise rate of each food material is different even if the microwave irradiation is uniform. Further, in order to shorten the time, in the high output type microwave oven used in convenience stores and the like, the uneven heating of foodstuffs tends to be larger.

As a method for solving this problem, a microwave heating adjustment sheet for preventing overheating cooking using a metal-deposited thin film and a microwave absorbing package have been proposed (for example, Patent Documents 1 and 2).

However, when the microwave heating adjustment sheet for preventing overheating cooking provided in Patent Document 1 is used, since it has a metal thin film layer, there is a risk of sparks and it is suitable for product inspection using a metal detector. It causes trouble. Further, when the microwave absorbing package provided in Patent Document 2 is used, it is preferable because there is an opening for venting water vapor, and there is a risk of hot steam leaking and burns when it is taken out from the microwave oven. No.

Japanese Unexamined Patent Publication No. 2014-198226 Japanese Unexamined Patent Publication No. 2016-94220

An object of the present invention is to provide a cover film for microwave-heated foodstuffs, which can suppress a partial temperature rise of foodstuffs during microwave heating of a microwave oven and can heat the whole foodstuffs substantially uniformly.

The present invention for solving such a problem is characterized by the following configuration.

That is, the present invention is a laminated film in which an inner layer A located on the heated food material side and an outer layer B located on the opposite side are laminated, and the inner layer A is composed of either or both of a polypropylene-based resin and a polyethylene-based resin. The outer layer B is made of a resin composition containing 0.07 to 1.5% by weight of a nonionic surfactant or a surfactant which is a mixture of a nonionic surfactant and an organic sulfonate, and the outer layer B is a polypropylene resin. , A cover film for heated foodstuffs, which comprises any or both of a polyethylene resin and a resin composition containing 0.9 to 9% by weight of the surfactant.

In the present invention, a cover film for microwave-heated foodstuffs in which the concentration of the surfactant in the outer layer B is higher than the concentration of the surfactant in the inner layer A is preferable.

In the present invention, a cover film for microwave oven-heated foodstuffs in which the inner layer A is made of polypropylene-based resin and the outer layer B is made of polypropylene-based resin and polyethylene-based resin is preferable.

In the present invention, the nonionic surfactant is a partial ester compound of a trihydric or tetravalent aliphatic polyhydric alcohol and an aliphatic monocarboxylic acid having 12 to 18 carbon atoms, and the organic sulfonate is a carbon number of carbon atoms. A cover film for microwave-heated foodstuffs, which is an alkali metal salt of an alkylsulfonic acid of 12 to 18, is preferable.

In the present invention, a cover film for microwave-heated foodstuffs in which the mixed weight ratio of the nonionic surfactant / the organic sulfonate is in the range of 70/30 to 100/0 is preferable.

In the present invention, a cover film for microwave-heated foodstuffs in which the inner layer A directly faces the cooked foodstuffs is preferable.

In the present invention, a cover film for microwave-heated foodstuffs in which the outer layer B forms the outer surface of the laminated film on the opposite side to the cooked foodstuffs is preferable.

According to the cover film for microwave-heated foodstuffs according to the present invention, when a plurality of different foodstuffs are heated simultaneously in a microwave oven, the temperature rise of the foodstuffs can be suppressed by covering the foodstuffs whose heating is desired to be suppressed, and the foodstuffs are heated at the same time. It is possible to heat a plurality of kinds of foodstuffs to a desired uniform temperature.

This is an example in which there is no heat suppressing effect when a single-layer film with a small amount of surfactant added is put on the food material. This is an example in which the heating suppression effect is not obtained when the food material is covered with a single-layer film in which a large amount of surfactant is added. This is an example of having a heating suppressing effect when a two-layer laminated film having a different amount of a surfactant added is put on a food material. This is an example in which there is no heat suppressing effect when a two-layer laminated film having a different amount of a surfactant added is put on a food material. This is an example in which there is no heat suppressing effect when the food material is wrapped in a two-layer laminated film in which the amount of the surfactant added is different. This is an example in which there is no heat suppressing effect when the food material is wrapped in a two-layer laminated film in which the amount of the surfactant added is different.

Hereinafter, the cover film for microwave-heated foodstuffs of the present invention will be specifically described.
The cover film for microwave-heated foodstuffs of the present invention is a laminated film in which at least the inner layer A located on the side of the cooked foodstuff and the outer layer B located on the opposite side are laminated (hereinafter, the inner layer A is simply referred to as the A layer). The outer layer B may be simply referred to as the B layer.) The A layer is important for improving the film forming property and the handleability of the film by giving an appropriate rigidity to the film. Further, if necessary, a layer made of a polypropylene-based resin or a polyethylene-based resin may be laminated between the A layer and the B layer or on the A layer side to form three or more kinds of composite laminated films.

The resin composition constituting the layer A in the present invention comprises either or both of a polypropylene-based resin and a polyethylene-based resin, and is a nonionic surfactant or a mixture of a nonionic surfactant and an organic sulfonate. It is necessary to consist of a resin composition containing 0.07 to 1.5% by weight of a surfactant. With this configuration, it becomes a cover film for microwave-heated foodstuffs, which has excellent heat resistance and an excellent heating suppression effect as a whole.

When the amount of the surfactant in the A layer is less than 0.07% by weight, the concentration difference from the surfactant added to the B layer is large, and the surfactant added to the B layer shifts to the A layer side, resulting in As a result, the effect of suppressing heating is deteriorated, and the uniform heating property of the food is inferior. If the amount of the surfactant in the layer A exceeds 1.5% by weight, the effect of suppressing heating is also reduced, and the amount of the surfactant contained in the entire film is increased, so that smoke is emitted from the surfactant during film formation. Etc. occur in large quantities, making film formation difficult.

Examples of the polypropylene-based resin include homopolypropylene, a random or block copolymer of ethylene and propylene, and a ternary copolymer of ethylene, butene and propylene, which have a melting point of 140 to 165 ° C. from the viewpoint of heat resistance. Those are preferable.

Examples of the polyethylene-based resin include high-pressure method low-density polyethylene, linear low-density polyethylene, and high-density polyethylene.

The polypropylene-based resin and the polyethylene-based resin can be mixed and used in an appropriate ratio composition, but a resin composition containing 70% by weight or more of the polypropylene-based resin is used to obtain a cover film having excellent heat resistance. Is preferable.

Above all, it is particularly preferable to use a resin composition containing 40% by weight or more of homopolypropylene because high rigidity can be obtained, movement of the surfactant in the layer is suppressed, and the uniform heating property of the food material is excellent.

The resin composition constituting the B layer in the present invention comprises either or both of a polypropylene-based resin and a polyethylene-based resin, and is the above-mentioned nonionic surfactant or nonionic surfactant and an organic sulfonate. It is necessary to consist of a resin composition containing 0.9 to 9% by weight of a surfactant which is a mixture of the above.

If the amount of the surfactant is less than 0.9% by weight, the effect of suppressing heating is insufficient, and if the amount of the surfactant exceeds 9% by weight, the surfactant is deposited on the surface of the film to become white powder and the appearance is deteriorated.

In the cover film for microwave-heated foodstuffs of the present invention, the B layer contains 0.9 to 9% by weight of a nonionic surfactant or a surfactant which is a mixture of a nonionic surfactant and an organic sulfonate. In order to prevent the surfactant from migrating from the B layer side and lowering the concentration of the surfactant in the B layer, the same surfactant is contained in the A layer in a relatively large amount within the range of. , It is contained in the range of 0.07 to 1.5% by weight at a concentration lower than the concentration of the B layer.

As the polypropylene-based resin and the polyethylene-based resin of the resin composition constituting the B layer, those described in the resin composition constituting the A layer can be preferably used.

In the present invention, it is particularly preferable that the inner layer A is made of polypropylene-based resin and the outer layer B is made of polypropylene-based resin and polyethylene-based resin.

The surfactant used in the present invention is a nonionic surfactant or a mixture of a nonionic surfactant and an organic sulfonate in both the resin composition constituting the A layer and the resin composition constituting the B layer. The mixed weight ratio of the nonionic surfactant / organic sulfonate is preferably in the range of 70/30 to 100/0, and more preferably in the range of 70/30 to 90/10.

The nonionic surfactant is preferably a partial ester compound of a trihydric or tetravalent aliphatic polyhydric alcohol and an aliphatic monocarboxylic acid having 12 to 18 carbon atoms.

Examples of the trihydric or tetravalent aliphatic polyhydric alcohol include trivalent aliphatic alcohols such as glycerin and tetravalent aliphatic alcohols such as pentaerythritol, diglycerin and sorbitan.

Examples of the aliphatic monocarboxylic acids having 12 to 18 carbon atoms include saturated fatty acid monocarboxylic acids such as lauric acid, myristic acid, partiminic acid and stearic acid, and unsaturated fatty acids such as palmitoleic acid, oleic acid and linolenic acid. Examples thereof include monocarboxylic acids, and examples of the partial ester compound with the above-mentioned trivalent or tetravalent aliphatic polyhydric alcohol include glycerin fatty acid ester, pentaerythritol fatty acid ester, diglycerin fatty acid ester, and sorbitan fatty acid ester.

Specific examples of the glycerin fatty acid ester include glycerin monolaurate, glycerin dilaurate, glycerin monomillistart, glycerin dimillistart, glycerin monopalmitate, glycerin dipalmitate, glycerin monosteert, and glycerin dyste. Alerts, glycerin monoole art, glycerin diore art, etc.

Specific examples of the above-mentioned pentaerythritol fatty acid ester include pentaerythritol monolaurate, pentaerythritol dilaurate, pentaerythritol monomillistart, pentaerythritol dimyristart, pentaerythritol monopalmitate, pentaerythritol dipalmitate, and penta. Examples include pentaerythritol monosteaert, pentaerythritol disterert, pentaerythritol monooleart, and pentaerythritol dioreart.

Specific examples of the above-mentioned diglycerin fatty acid ester include diglycerin monolaurate, diglycerin monomillistart, diglycerin monopalmitate, diglycerin monomyristoleart, diglycerin monosteert, and diglycerin monooleart. Diglycerin monolinoleat, diglycerin dilaurate, diglycerin dimilista, diglycerin dipalmitate, diglycerin dimyristoreart, diglycerin disteaert, diglycerin dioleart, diglycerin dilinoleart, di Glycerin Lauromilistart, Glycerin myristo palmitate, Diglycerin lumitosteert, Diglycerin lumitooleate, Diglycerin stearopalmitreart, Diglycerin trilaurate, Diglycerin trimilitat, Diglycerin tripalmitate, Diglycerin Trimilist Reart, Diglycerin Triste Alert, Diglycerin Trioleart, Diglycerin Trilinoleart, Diglycerin Dilauro Millistart, Diglycerin Laurogi Millistart, Diglycerin Dimilist Palmitate, Diglycerin Millist Dipalmi Examples thereof include tart, diglycerin dipalmitose alert, diglycerin lumito diste alert, diglycerin dipalmitoleart, diglycerin lumitodiole art, diglycerin distearo palmitre art, diglycerin stearo dipalmitre art and the like.

Specific examples of the sorbitan fatty acid ester include sorbitan monolaurate, sorbitan monomillistart, sorbitan monopalmitate, sorbitan monomyristole art, sorbitan monosteert, sorbitan monoole art, sorbitan monolinoleat, and sorbitanji. Laurat, Sorbitan Jimiri Start, Sorbitan Ji Palmitate, Sorbitan Jimi Risto Reart, Sorbitan Jiste Alert, Sorbitan Giole Art, Sorbitan Jiri Nore Art, Sorbitan Lauro Miri Start, Sorbitan Myristo Palmitat, Sorbitan Palmito Stealert, Sorbitan Palmitoole Art, Sorbitan Stearo Palmitre Art, Sorbitan Trilaurate, Sorbitan Trimilli Start, Sorbitan Tripalmitate, Sorbitan Trimilist Reart, Sorbitan Triste Alert, Sorbitan Triole Art, Sorbitan Trilinole Art, Sorbitan Girauro Miri Start, Sorbitan Laurologic Milli Start, Sorbitan Jimilist Palmitat, Sorbitan Mirito Jipalmitato, Sorbitan Jipalmit Stealert, Sorbitan Palmito Giste Alert, Sorbitan Jipalmit Oleart, Sorbitan Palmito Dioreart, Sorbitan Jistaro Palmitre Examples include art, sorbitan stearoji palmitre art, and the like.

Examples of the organic sulfonate include an alkylsulfonic acid alkali metal salt, an alkylarylsulfonic acid alkali metal salt, a 1,2-bis (alkyloxycarbonyl) -1-ethanesulfonic acid alkali metal salt, and the like, among which 12 carbon atoms are used. Alkali metal salts of alkyl sulfonic acid of ~ 18 are preferable in terms of food hygiene. These include lithium dodecyl sulfonate, lithium tridecyl sulfonate, lithium tetradecyl sulfonate, lithium pentadecyl sulfonate, lithium hexadecyl sulfonate, lithium heptadecyl sulfonate, lithium octadecyl sulfonate, sodium dodecyl sulfonate, tri. Sodium decyl sulfonate, sodium tetradecyl sulfonate, sodium pentadecyl sulfonate, sodium hexadecyl sulfonate, sodium heptadecyl sulfonate, sodium octadecyl sulfonate, potassium dodecyl sulfonate, potassium tridecyl sulfonate, potassium tetradecyl sulfonate , Pentadecylsulfonate potassium, hexadecylsulfonate potassium, heptadecylsulfonate potassium, octadecylsulfonate potassium and the like.

In addition, in order to ensure slipperiness and laminating suitability suitable for film processing, specific additives, specifically organic lubricants such as erucic acid amide, are added to the A layer and the B layer as long as the object of the present invention is not impaired. , Antioxidants having a molecular weight of 500 or more, and inorganic particles such as silica, zeolite and calcium carbonate, and organic particles such as polymethylmethacrylate crosslinked particles may be selected and used. Further, it can contain an antioxidant, a heat-resistant stabilizer, an antistatic agent and the like that improve the film-forming property. As long as the effects of the present invention are not impaired, the polymers of the A layer and the B layer can be mixed and used with ears, slit scraps and the like generated when the film of the present invention is produced, if necessary.

The thickness of the cover film for microwave-heated foodstuffs of the present invention is preferably in the range of 20 to 100 μm, and in the case of a two-layer structure of A layer and B layer, A layer / B layer = 2/1 to 10/1. Those in the range are suitable, and if they deviate from this range, uneven stacking may occur and the film forming property may deteriorate.

As a method of using the cover film for microwave-heated foodstuffs of the present invention, it is preferable to cover the foodstuff whose heating is to be suppressed with the A layer side facing (for example, in contact with) the foodstuff. Further, a plurality of cover films for microwave-heated foodstuffs of the present invention may be stacked and used.

The cover film for microwave-heated foodstuffs of the present invention can be used as it is in the form of a sheet, or can be used even if it is processed into a packaging form such as a lid material. However, as shown in the following basic study, it is necessary to use it in a form having a heat suppressing effect.

Further, the cover film for microwave-heated foodstuffs of the present invention is used by laminating a biaxially stretched polyamide film, a biaxially stretched polyester film, printing paper, etc. individually or in combination on the A layer side as needed. May be good.

Hereinafter, a series of study results leading to the invention of the cover film for microwave-heated foodstuffs of the present invention will be described with reference to the drawings.

FIG. 1 is an example in which the heat suppressing effect is not obtained when the single-layer film 3 in which the amount of the surfactant added is as small as 0.07 to 1.5% by weight is put on the food material (rice 1). Put 150 g of rice in a polypropylene tray 2, cover it with a film 3, and heat it with a Toshiba microwave oven ER-LD7 at a display output of 500 W for 60 seconds, and then measure the temperature of the rice with a contact thermometer manufactured by Tasco Japan. Measured with TNA-110. As in the case where the film 3 was not covered, the temperature rose to 80 ° C., and the heat suppressing effect was not recognized.

FIG. 2 shows an example in which the food material is covered with the single-layer film 4 in which the amount of the surfactant added is as large as 2 to 9% by weight, and the heating suppressing effect is not obtained. The temperature rose to 80 ° C. as in the case where the film 4 was not covered.

FIG. 3 shows an example in which a two-layer laminated film having a different amount of a surfactant added is covered with a heat-suppressing effect. The amount of the surfactant added to the two-layer laminated film of the layer 6 in which the amount of the surfactant added is as small as 0.07 to 1.5% by weight and the layer 5 in which the amount of the surfactant added is as large as 4 to 9% by weight. When the layer 6 having a small amount of water was covered toward the rice side, the temperature rose only to 70 ° C., and a heating suppressing effect was observed.

FIG. 4 shows an example in which the heating suppression effect is not obtained when the two-layer laminated films having different amounts of the surfactant added are covered. The amount of the surfactant added to the two-layer laminated film of the layer 7 in which the amount of the surfactant added is as small as 0.07 to 1.5% by weight and the layer 8 in which the amount of the surfactant added is as large as 2-9% by weight. When the layer 8 having a large amount of water was put on the rice side, the temperature rose to 80 ° C., and the heating suppressing effect was not observed.

FIG. 5 shows an example in which the heating suppression effect is not obtained when the film is wrapped in a two-layer laminated film in which the amount of the surfactant added is different. The amount of the surfactant added to the two-layer laminated film of the layer 11 in which the amount of the surfactant added is as small as 0.07 to 1.5% by weight and the layer 10 in which the amount of the surfactant added is as large as 2-9% by weight. The layer 11 having a small amount of water was wrapped toward the rice side, and the one having a small hole 9 for steaming was heated in the same microwave oven as above. The temperature rose to 80 ° C., and no heat suppressing effect was observed.

FIG. 6 is an example in which there is no heat suppressing effect when wrapped in a two-layer laminated film in which the amount of the surfactant added is different. The amount of the surfactant added to the two-layer laminated film of the layer 13 in which the amount of the surfactant added is as small as 0.07 to 1.5% by weight and the layer 14 in which the amount of the surfactant added is as large as 2-9% by weight. The layer 14 having a large amount of water was wrapped toward the rice side, and a small hole 12 for steaming was opened and heated in a microwave oven in the same manner as described above. The temperature rose to 80 ° C., and no heat suppressing effect was observed.

Examining the observation results shown in FIGS. It is presumed that it is absorbed by the water film and can be expected to have an effect of suppressing the heating of foodstuffs. In the form of FIG. 1, since a single-layer film with a small amount of surfactant added is covered, it is presumed that a water film due to water vapor evaporated from the rice is difficult to form and the heating suppressing effect is not recognized. In the form of FIG. 3, water vapor evaporated from rice wraps around the outer layer in which a large amount of surfactant is added to form a water film, and microwaves from a microwave oven are emitted on the outer surface side thereof. It is presumed that it was absorbed by the water film and the heating of the food was suppressed. However, in the forms shown in FIGS. 2 and 4, a water film is generated on the film surface on the food side due to the steam evaporated from the rice, and the food is heated by the high-temperature steam re-evaporated from the water film, so that heating is suppressed. It is probable that the effect was reduced or the heating suppression effect was not observed.

The heating suppressing effect was not observed in the forms shown in FIGS. 5 and 6, but this is because in the form shown in FIG. 5, since the foodstuff is wrapped in the two-layer laminated film, the water vapor evaporated from the rice is outside. It is presumed that this is because the layer cannot reach the outer surface of the layer in which the amount of the surfactant added is large and no water film is formed on the surface. It is presumed that the form shown in FIG. 6 is due to heating by high-temperature steam from the water film formed on the food material side of the film.

Next, an example of the method for producing the cover film for microwave-heated foodstuffs of the present invention will be described with respect to the case of a two-layer laminated film.

Using two extruders, a surfactant master containing 70% by weight or more of a polypropylene-based resin in the range of MFR (melt flow rate) of 5 to 10 g / 10 minutes and a polypropylene-based resin as the main components from one extruder. The resin composition mixed with the batch is extruded at 200 to 250 ° C. (layer A), and the resin composition obtained by mixing the polypropylene resin, the polyethylene resin and the same surfactant masterbatch as above from another extruder is obtained. Extruded at 200 to 250 ° C (B layer), laminated with a co-extruded multilayer die, extruded into a film so that the thickness of the A layer / B layer is, for example, 43 μm / 7 μm, and used with a cooling roll at 25 to 50 ° C. Cast cooled and solidified to form a laminated film. Subsequently, if necessary, the surface of the A layer is subjected to a corona discharge treatment.

The present invention will be described with reference to examples, but the present invention is not limited thereto. The method for measuring the characteristics and the method for evaluating the effect in the present invention are as follows.

(1) Resin density The density was measured according to the density gradient tube method specified in JIS K7112-1980.

(2) Film thickness Using a dial gauge type thickness gauge (JIS B-7509-1992, stylus 5 mmφ flat type), 10 points were measured at 10 cm intervals in the longitudinal and width directions of the film, and the average value was measured. And said.

(3) Thickness of each layer A cross section of the film was cut out with a microtome, and the cross section was magnified 1000 times using a digital microscope VHX-100 (manufactured by KEYENCE Co., Ltd.) and photographed. The distance in the thickness direction of each layer was measured, and the thickness of each layer was obtained by back calculation from the magnification. In determining the thickness of each layer, a total of five cross-sectional photographs of a total of five locations arbitrarily selected from different measurement fields of view were used, and the average value was calculated.

(4) Melt flow rate (MFR)
According to JIS K-7210, the polyethylene-based resin was measured at 190 ° C. and the polypropylene-based resin was measured at 230 ° C.

(5) Melting point (T _m )
Using a differential scanning calorimetry device DSC (DSC-60A) manufactured by Shimadzu Corporation, a 5 mg sample was heated to 200 ° C at a rate of 10 ° C / min under a nitrogen atmosphere and held for 5 minutes, and then 10 When the temperature is cooled to 10 ° C. at a cooling rate of ° C./min and the temperature is raised again at a rate of 10 ° C./min, the peak temperature of the endothermic peak accompanying the melting of the resin is set to the melting point (T). _m ).

(6) Film-forming properties When forming a laminated film, those with severe edge curl during casting were marked with x, and those with easy winding tension adjustment and no wrinkles were marked with ○.

(7) Film condition After forming the laminated film, visually check the film condition and rub the film surface with a finger. Those in a clean state without white powder generated on the surface were marked with ○.

(8) Microwave oven heating evaluation For a bento container made of polypropylene material with a size of 200 mm x 250 mm and a height of 25 mm that can store two ingredients so that they do not come into contact with each other, 150 g of white rice on one side and 100 g of grilled mackerel on the other side (family) (Mart Co., Ltd.) and Seven Gold / Gold hamburger 100 g (manufactured by Seven-Eleven Co., Ltd.) were installed, and the A-layer side of the film of the present invention was placed on top of the white rice so as to face the rice.

After heating the bento container filled with ingredients with a Toshiba microwave oven ER-LD7 at a display output of 500 W for 60 seconds, the temperature of each ingredient is measured with a contact thermometer TNA-110 manufactured by Tasco Japan. The temperature difference of the ingredients was evaluated.

The evaluation items and evaluation criteria are as follows.
・ Temperature difference between white rice and grilled mackerel ○: less than 10 ℃ ×: 10 ℃ or more ・ Temperature difference between white rice and hamburger ○: less than 10 ℃ ×: 10 ℃ or more.

The raw materials used in this example are as follows.
(1) Homopolypropylene (PP-1)
MFR = 8.0 g / 10 minutes, density = 0.900 g / cm ³ , T _m = 163 ° C.
(2) Ethylene-propylene random copolymer (PP-2)
MFR = 6.0 g / 10 minutes, density = 0.900 g / cm ³ , T _m = 142 ° C.
(3) Surfactant masterbatch (MB-1, main component is polypropylene resin)
The surfactant has a mixed ratio of nonionic surfactant and organic sulfonate of 82/18, and the nonionic surfactant is a partial ester of glycerin and an aliphatic monocarboxylic acid having 12 to 18 carbon atoms. Surfactant master batch which is a mixture of a compound and a partial ester compound of diglycerin and an aliphatic monocarboxylic acid having 12 to 18 carbon atoms, wherein the organic sulfonate is an alkyl sulfonic acid sodium salt having 12 to 18 carbon atoms.
MFR = 7.0 g / 10 minutes, density = 0.900 g / cm ³ , surfactant concentration = 15% by weight.
(4) Ethylene-propylene random copolymer (PP-3)
MFR = 25.0 g / 10 minutes, density = 0.900 g / cm ³ , T _m = 125 ° C.
(5) Ethylene / α-olefin random copolymer elastomer (E-1)
MFR = 3.6 g / 10 minutes, density = 0.885 g / cm ³ .
(6) High-density polyethylene (HD-1)
MFR = 16.0 g / 10 minutes, density = 0.955 g / cm ³ , T _m = 130 ° C.
(7) Linear low density polyethylene (LL-1)
MFR = 8.0 g / 10 minutes, density = 0.920 g / cm ³ , T _m = 123 ° C.
(8) Linear low density polyethylene (LL-2)
MFR = 2.1 g / 10 minutes, density = 0.920 g / cm ³ , T _m = 123 ° C.

Example 1
As the resin for layer A, 48.5 parts by weight of homopolypropylene (PP-1), 48.5 parts by weight of ethylene / propylene random copolymer (PP-2) and 3 parts by weight of masterbatch of surfactant (MB-1) are mixed. A resin composition obtained by mixing 83% by weight of an ethylene / propylene random copolymer (PP-2) and 17% by weight of a masterbatch (MB-1) of a surfactant was used as the resin for the B layer. Was put into each of the two extruders, extruded from a T-shaped cap of two-layer co-extruded laminate at an extrusion temperature of 230 ° C, and rapidly cooled with a casting roll of 40 ° C to form a cover film for microwave-heated foodstuff of two-layer laminate. A film was formed. The total thickness of the obtained cover film for microwave-heated foodstuffs was 50 μm, and the stacking ratio of the A layer / B layer was 6/1. The film-forming property was good, there was no edge curling during casting, the slipperiness was good, and stable winding was possible. The film of the present invention satisfied all the required characteristics.

Example 2
The same as in Example 1 except that a resin composition obtained by mixing 83 parts by weight of an ethylene / propylene random copolymer (PP-3) and 17 parts by weight of a surfactant masterbatch (MB-1) was used as the resin for the B layer. A two-layer laminated cover film for microwave-heated foodstuffs was obtained. All of the required characteristics of the film of the present invention were satisfied.

Example 3
The same as in Example 1 except that a resin composition obtained by mixing 94 parts by weight of an ethylene / propylene random copolymer (PP-2) and 6 parts by weight of a surfactant masterbatch (MB-1) was used as the resin for the B layer. A two-layer laminated cover film for microwave-heated foodstuffs was obtained. The film of the present invention satisfied all the required characteristics.

Example 4
The same as in Example 1 except that a resin composition obtained by mixing 47 parts by weight of an ethylene / propylene random copolymer (PP-2) and 53 parts by weight of a surfactant masterbatch (MB-1) was used as the resin for the B layer. A two-layer laminated cover film for microwave-heated foodstuffs was obtained. The film of the present invention satisfied all the required characteristics.

Example 5
As the resin of the A layer, 49.8 parts by weight of homopolypropylene (PP-1), 49.7 parts by weight of ethylene / propylene random copolymer (PP-2) and 0.5 parts by weight of the surfactant masterbatch (MB-1). A two-layer laminated cover film for microwave-heated foodstuffs was obtained in the same manner as in Example 1 except that the resin composition in which the above was mixed was used. The film of the present invention satisfied all the required characteristics.

Example 6
As the resin of the A layer, 50.0 parts by weight of homopolypropylene (PP-1), 46.7 parts by weight of ethylene / propylene random copolymer (PP-2), and 3.3 parts by weight of the surfactant masterbatch (MB-1). A two-layer laminated cover film for microwave-heated foodstuffs was obtained in the same manner as in Example 1 except that the resin composition in which the above was mixed was used. The film of the present invention satisfied all the required characteristics.

Example 7
As the resin of the A layer, 50.0 parts by weight of homopolypropylene (PP-1), 40.3 parts by weight of ethylene / propylene random copolymer (PP-2), and 9.7 parts by weight of the surfactant masterbatch (MB-1). A two-layer laminated cover film for microwave-heated foodstuffs was obtained in the same manner as in Example 1 except that the resin composition in which the above was mixed was used. The film of the present invention satisfied all the required characteristics.

Example 8
A resin composition obtained by mixing 10 parts by weight of homopolypropylene (PP-1), 87 parts by weight of ethylene / propylene random copolymer (PP-2), and 3 parts by weight of masterbatch (MB-1) as a resin for layer A. A two-layer laminated cover film for microwave-heated foodstuffs was obtained in the same manner as in Example 1 except that the above was used. The film of the present invention satisfied all the required characteristics.

Example 9
As the resin for the A layer, a resin composition obtained by mixing 87 parts by weight of homopolypropylene (PP-1), 10 parts by weight of ethylene / propylene copolymer (PP-2) and 3 parts by weight of masterbatch (MB-1) of a surfactant is prepared. A two-layer laminated cover film for microwave-heated foodstuffs was obtained in the same manner as in Example 1 except that it was used. The film of the present invention satisfied all the required characteristics.

Example 10
As the resin for the B layer, 33 parts by weight of the ethylene / propylene random copolymer (PP-3), 20 parts by weight of the ethylene / α-olefin random copolymer elastomer (E-1), and 20 parts by weight of the high density polyethylene (HD-1). In the same manner as in Example 1, a two-layer laminate was used except that a resin composition obtained by mixing 10 parts by weight of linear low-density polyethylene (LL-1) and 17 parts by weight of a surfactant master batch (MB-1) was used. A cover film for microwave-heated foodstuffs was obtained. The film of the present invention satisfied all the required characteristics.

Example 11
The stacking ratio of the A layer / B layer was set to 2.5 / 1, and a cover film for microwave-heated foodstuffs having two layers laminated was obtained in the same manner as in Example 9 except for the above. The film of the present invention satisfied all the required characteristics.

Example 12
The stacking ratio of the A layer / B layer was set to 9/1, and other than that, a cover film for microwave-heated foodstuffs having two layers laminated was obtained in the same manner as in Example 9. The film of the present invention satisfied all the required characteristics.

Example 13
Same as Example 9 except that a resin composition obtained by mixing 97 parts by weight of linear low-density polyethylene (LL-2) and 3 parts by weight of a surfactant masterbatch (MB-1) was used as the resin for layer A. A two-layer laminated cover film for microwave-heated foodstuffs was obtained. The film of the present invention satisfied all the required characteristics.

Example 14
As the resin for the B layer, a resin composition obtained by mixing 70 parts by weight of an ethylene / propylene copolymer (PP-2) and 30 parts by weight of a surfactant masterbatch (MB-1) was used, and the other parts were the same as in Example 1. A two-layer laminated cover film for microwave-heated foodstuffs was obtained. Although some white powder was generated in the film state, there was no problem in practical use, and the required characteristics of the film of the present invention were satisfied.

Example 15
As the resin for layer A, 48.5% by weight of homopolypropylene (PP-1), 48.5 parts by weight of ethylene / propylene random copolymer (PP-2) and 3 parts by weight of surfactant master batch (MB-1) are mixed. Using the above resin composition, as the resin for the B layer, a resin composition obtained by mixing 83 parts by weight of ethylene / propylene random copolymer (PP-2) and 17 parts by weight of the surfactant master batch (MB-1) was used. As the resin for the layer, a resin composition obtained by mixing 99.5 parts by weight of homopolypropylene (PP-1) and 0.5 parts by weight of the surfactant master batch (MB-1) was used, and a resin composition was used between the A layer and the B layer. As the middle layer C, these are charged into three extruders, respectively, extruded from a T-shaped cap of a three-layer co-extruded laminate at an extrusion temperature of 230 ° C., rapidly cooled with a casting roll of 40 ° C., and heated in a microwave oven of the three-layer laminate. A cover film for foodstuffs was formed. The total thickness of the obtained cover film for microwave-heated foodstuffs was 50 μm, and the stacking ratio of the A layer / C layer / B layer was 1/8/1. The film-forming property was good, there was no edge curling during casting, the slipperiness was good, and stable winding was possible. The film of the present invention satisfied all the required characteristics.

Example 16
Examples except that a resin composition obtained by mixing 90.3 parts by weight of ethylene / propylene random copolymer (PP-2) and 9.7 parts by weight of a surfactant masterbatch (MB-1) was used as the resin for the C layer. In the same manner as in No. 13, a three-layer laminated cover film for microwave-heated foodstuffs was obtained. The film of the present invention satisfied all the required characteristics.

Comparative Example 1
As the resin for the A layer, a resin composition obtained by mixing 83 parts by weight of homopolypropylene (PP-1) and 17 parts by weight of the masterbatch (MB-1) was used, and as the resin for the B layer, an ethylene-propylene copolymer ( PP-2) Using a resin composition in which 97 parts by weight and 3 parts by weight of a masterbatch (MB-1) of a surfactant were mixed, a film was formed in the same manner as in Example 1 except for the above, and the obtained film was carried out. The evaluation was performed in the same manner as in Example 1. Since the amount of the surfactant added to the B layer is small, the temperature difference between the salt-grilled white rice and mackerel and the temperature difference between the white rice and the hamburger are 10 ° C or more in the microwave oven heating evaluation, which satisfies the required characteristics as the film of the present invention. It wasn't.

Comparative Example 2
A resin composition obtained by mixing 99.6 parts by weight of homopolypropylene (PP-1) and 0.4 parts by weight of a masterbatch (MB-1) of a surfactant was used as the resin for the A layer, and ethylene was used as the resin for the B layer. -A resin composition obtained by mixing 94 parts by weight of propylene copolymer (PP-2) and 6 parts by weight of a masterbatch (MB-1) of a surfactant was used, and other than that, a film was formed in the same manner as in Example 1 to obtain the resin composition. The film was evaluated in the same manner as in Example 1. Since the rigidity of the homopolypoly of the A layer is high, the edge curl is large at the time of casting and the film forming property is deteriorated, and since the amount of the A layer added is small, the surfactant added to the B layer is transferred to the A layer. As a result, the amount of surfactant in the B layer is reduced, and in the microwave oven heating evaluation, the temperature difference between salt-baked white rice and mackerel and the temperature difference between white rice and hamburger are 10 ° C or more. There wasn't.

Comparative Example 3
As the resin for layer A, 48.5 parts by weight of homopolypropylene (PP-1), 48.5 parts by weight of ethylene-propylene copolymer (PP-2) and 3.0 parts by weight of surfactant master batch (MB-1) were used. Using the mixed resin composition, as the resin for the B layer, a resin composition obtained by mixing 20% by weight of ethylene / propylene copolymer (PP-2) and 80 parts by weight of the surfactant master batch (MB-1) was used. A film was formed in the same manner as in Example 1, and the obtained film was evaluated in the same manner as in Example 1. Since the amount of the surfactant added to the B layer is large, white powder is deposited on the film and the appearance is poor, which does not satisfy the required characteristics as the film of the present invention.

The conditions and results of Examples 1 to 16 and Comparative Examples 1 to 3 are collectively shown in Tables 1 to 4.

1 ... Rice 2 ... Polypropylene tray 3 ... Single-layer film with a small amount of surfactant added 4 ... Single-layer film with a large amount of surfactant added 5, 8, 10, 14 ... ... Layers 6, 7, 11, 13 with a large amount of surfactant added ... Layers 9, 12 with a small amount of surfactant added ... Steam holes

Claims (6)

A laminated film outer layer B is laminated on the opposite side of the inner layer A located on the heating food side, the inner layer A, the polypropylene-based resin, the resin composition ing from either or both of the polyethylene resin, It contains 0.07 to 1.5% by weight of a nonionic surfactant or a surfactant which is a mixture of a nonionic surfactant and an organic sulfonate , and the outer layer B is a polypropylene-based resin or a polyethylene-based resin. the resin composition ing from either or both of the resins, and also contains the surfactant from 0.9 to 9 wt%, the inner layer a is characterized by being used is covered in a state in contact with the heating foodstuff electronic Cover film for range-heated foods. The cover film for microwave-heated foodstuffs according to claim 1, wherein the concentration of the surfactant in the outer layer B is higher than the concentration of the surfactant in the inner layer A. The cover film for microwave-heated foodstuffs according to claim 1 or 2, wherein the inner layer A is made of a polypropylene resin and the outer layer B is made of a polypropylene resin and a polyethylene resin. The nonionic surfactant is a partial ester compound of a trihydric or tetravalent aliphatic polyhydric alcohol and an aliphatic monocarboxylic acid having 12 to 18 carbon atoms, and the organic sulfonate has 12 to 18 carbon atoms. The cover film for microwave-heated foodstuffs according to any one of claims 1 to 3, which is an alkylsulfonic acid alkali metal salt. The cover film for microwave-heated foodstuffs according to any one of claims 1 to 4, wherein the mixed weight ratio of the nonionic surfactant / the organic sulfonate is in the range of 70/30 to 100/0. The cover film for microwave-heated foodstuffs according to any one of claims 1 to 5 , wherein the outer layer B forms the outer surface of the laminated film on the opposite side to the cooked foodstuff.

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