JP2021155859A - Packaging paper for food product, and method of producing food product - Google Patents

Abstract

To provide packaging paper for a food product, capable of uniformly heating a food product and suitably releasing moisture when heated in a microwave oven, and a method of producing a food product using the same.SOLUTION: The packaging paper for a food product, comprises polyolefin synthetic pulp of Canadian Standard Freeness of not less than 100 ml and not more than 520 ml, ceramic powder that generates far-infrared rays when heated, and natural pulp. The air-permeability of the paper is 5 to 200 cc/cm2/s.SELECTED DRAWING: None

Description

The present invention relates to food wrapping paper and a method for producing food.

Conventionally, a plastic film has been widely used as a packaging member for storing food (for example, Patent Document 1). However, plastic films for food packaging generally have low breathability. Therefore, when the food is wrapped in a film and stored in a refrigerator or the like, the water released from the inside of the food is cooled on the surface of the plastic film and easily becomes water droplets. Then, when the water returned to the food again, the texture may change or a region containing excessive water may be generated.

Further, when the food is heated in a microwave oven or the like, the moisture released from the inside of the food may be shielded by the plastic film and returned to the food, resulting in uneven heating.

Japanese Unexamined Patent Publication No. 2020-23345

As described above, with conventional plastic films for food packaging and the like, it has been difficult to release water generated during storage or heating. Further, in recent years, it has been desired to provide a packaging member capable of heating food efficiently and evenly in a shorter time.

The present invention has been made in view of such circumstances. An object of the present invention is to provide a food wrapping paper capable of uniformly and uniformly heating food by heating in a microwave oven or the like, and capable of appropriately releasing water, and a method for producing food using the wrapping paper.

That is, the present invention provides the following food wrapping paper.
[1] Containing polyolefin synthetic pulp having a Canadian standard drainage degree of 100 ml or more and 520 ml or less, ceramic powder that generates far infrared rays by heating, and natural pulp, the air permeability is 5 to 200 cc / cm ² / s. There is food wrapping paper.
[2] The food wrapping paper according to [1], which has a basis weight of 5 to 40 g / m ^2.

[3] The food wrapping paper according to [1] or [2], wherein the ceramic powder is at least one selected from the group consisting of cordierite, mullite, petalite, rhyolite, clay, and alumina.
[4] The food wrapping paper according to any one of [1] to [3], wherein the content of the polyolefin synthetic pulp is 10 to 80% by mass.

[5] The food wrapping paper according to any one of [1] to [4], wherein the content of the ceramic powder is 1 to 10% by mass.
[6] The food wrapping paper according to any one of [1] to [5], which is used for heating in a microwave oven.

The present invention also provides the following methods for producing foods.
[7] A step of wrapping the material with the food wrapping paper according to any one of the above [1] to [6], and a step of heating the material in a microwave oven while wrapped with the food wrapping paper. , A method of producing food.

The food wrapping paper of the present invention can appropriately release moisture, and further generates far infrared rays when heated in a microwave oven. Therefore, the material wrapped inside can be uniformly and fluffyly warmed.

In the present specification, the numerical range indicated by "-" means a numerical range including the numerical values described before and after "-".

As described above, the conventional food packaging material has low moisture permeability, and water droplets are likely to be generated during storage or heating. Further, with the conventional packaging material for food, it is difficult to uniformly heat the food by a microwave oven or the like.

On the other hand, the food wrapping paper of the present invention contains a polyolefin synthetic pulp having a Canadian drainage degree of 100 ml or more and 520 ml or less, a ceramic powder that generates far infrared rays by heating, and a natural pulp. Since the food wrapping paper of the present invention contains the above ceramic powder, for example, when heated in a microwave oven, far infrared rays are generated, and the food can be uniformly heated to the inside. Further, since the food wrapping paper has a Canadian drainage degree within the above range, excess water can be released to the outside when wrapping the food or heating the food, for example, and the food food can be eaten. The feeling is not easily impaired. On the other hand, it does not release excessive water and the required amount of water is retained inside. Therefore, the food can be kept in an appropriate state for a long period of time, and can be uniformly heated to the inside in a short time by a microwave oven or the like.

The food wrapping paper of the present invention may contain components other than polyolefin synthetic pulp, ceramic powder, and natural pulp, and may contain, for example, binder fibers and other components. Hereinafter, each component will be described.

-Polyolefin Synthetic Pulp Polyolefin synthetic pulp is a fiber aggregate in which a plurality of fine fibers made of polyolefin are entangled to form a fiber having a branched structure, and the fibers are aggregated without being aligned in a specific direction as a whole. The term "synthetic pulp is made of polyolefin" is not limited to the meaning that it is made of only polyolefin. That is, the polyolefin synthetic pulp includes other thermoplastic resins other than polyolefin and synthetic pulp containing other components described later.

Examples of polyolefins include polyethylene (ethylene homopolymer), polypropylene (propylene homopolymer), ethylene / propylene copolymer, ethylene / butene-1 copolymer, and ethylene / 4-methylpentene-1 copolymer. included. Further, the polyolefin of the present specification includes an ethylene / vinyl acetate copolymer obtained by polymerizing an olefin and a monomer other than the olefin, an ethylene / (meth) acrylic acid copolymer, and an ethylene / (meth) acrylic acid ester. Copolymers and the like are also included. In this case, the amount of the structural units other than the olefin is preferably 50 mol% or less, more preferably 40 mol% or less, based on all the structural units. Further, the polyolefin in the present specification also includes a graft-modified product obtained by graft-modifying a (unmodified) polyolefin with an unsaturated carboxylic acid monomer.

Among them, the polyolefin is preferably an ethylene-based polymer mainly containing ethylene or a propylene-based polymer mainly containing propylene from the viewpoint of cost and flexibility, and is preferably an ethylene homopolymer or an ethylene / α-olefin copolymer (α). -Olefins preferably have 3 to 20 carbon atoms), propylene homopolymers, propylene / α-olefin copolymers (α-olefins have 2 or 4 to 20 carbon atoms), or unsaturated carboxylic acid monomers. A polymer graft-modified with (hereinafter, also referred to as "modified polyolefin") is preferable. Among these, ethylene-based polymers (ethylene homopolymers, ethylene / α-olefin copolymers, or polymers obtained by graft-modifying these with unsaturated carboxylic acid monomers) are particularly preferable.

When the polyolefin is an ethylene homopolymer, the melt flow rate (hereinafter also referred to as "MFR") measured at 190 ° C. and a load of 2.16 kg is 0.01 g / 10 min to 1000 g / according to ASTM D 1238. 10 minutes is preferable, 0.1 g / 10 minutes to 500 g / 10 minutes is more preferable, and 1 g / 10 minutes to 100 g / 10 minutes is more preferable. When an ethylene homopolymer having an MFR in the above range is used, a polyolefin synthetic pulp having a branched structure can be obtained. As a result, the strength of the food wrapping paper tends to increase, and the supportability of the ceramic powder described later becomes good.

On the other hand, if the polyolefin is an ethylene · alpha-olefin copolymer, its density (ASTM D 1505) is preferably 0.850~0.950g / cm ^3, more preferably 0.870~0.945g / cm ³ , 0.9000 to 0.940 g / cm ³ is more preferable. In this case, the MFR measured at 190 ° C. and a load of 2.16 kg is preferably 0.1 to 100 g / 10 minutes, more preferably 0.5 to 50 g / 10 minutes, and 1 to 1 to 10 minutes, in accordance with ASTM D 1238. 20 g / 10 minutes is more preferred. When an ethylene / α-olefin copolymer having a density and MFR in the above range is used, a polyolefin synthetic pulp that is highly branched and has good mutual entanglement can be obtained. As a result, the strength of the food wrapping paper tends to increase, and the supportability of the ceramic powder described later becomes good.

Examples of α-olefins having 3 to 20 carbon atoms that copolymerize with ethylene include propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 4-methyl-1-pentene, 1-hexene, and the like. Includes α-olefins having 3 to 20 carbon atoms such as 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 1-eicosene.

The amount of ethylene-derived structural units in the ethylene / α-olefin copolymer is preferably 50 mol% or more and less than 100 mol%, more preferably 80.0 to 99.5 mol%, and 90.0 to 99.0. More preferably mol%.

Further, the MFR of the propylene homopolymer measured at 230 ° C. and a load of 2.16 kg in accordance with ASTM D 1238 is preferably 0.1 to 500 g / 10 minutes, preferably 0.5 to 100 g / 10 minutes. More preferably, 1 to 50 g / 10 minutes is further preferable. When a propylene homopolymer having an MFR in the above range is used, a polyolefin synthetic pulp that is highly branched and has good mutual entanglement can be obtained. As a result, the strength of the food wrapping paper tends to increase, and the supportability of the ceramic powder described later becomes good.

On the other hand, the propylene / α-olefin copolymer is preferably a copolymer of propylene and an α-olefin having 2 or 4 to 20 carbon atoms, and preferably has a melting point of 130 to 165 ° C. Further, according to ASTM D 1238, the MFR measured at 230 ° C. and a 2.16 kg load is preferably 0.1 to 500 g / 10 minutes, more preferably 0.5 to 100 g / 10 minutes, and 1 to 50 g / min. 10 minutes is even more preferred. When a propylene / α-olefin copolymer having a melting point and MFR in the above ranges is used, a polyolefin synthetic pulp that is highly branched and has good mutual entanglement can be obtained. As a result, the strength of the food wrapping paper tends to increase, and the supportability of the ceramic powder described later becomes good.

The α-olefin copolymerized with propylene is ethylene or an α-olefin having 4 to 20 carbon atoms. Examples of α-olefins include α-olefins exemplified by ethylene / α-olefin copolymers. The propylene content in the propylene / α-olefin copolymer is usually 50 mol% or more and less than 100 mol%, preferably 80.0 to 99.5 mol%, and more preferably 90.0 to 99.0 mol%. ..

The above ethylene homopolymer, ethylene / α-olefin copolymer, propylene homopolymer and propylene / α-olefin copolymer are monomers in the presence of conventionally known catalysts such as Cheegler-Natta-based catalysts and metallocene-based catalysts. Can be prepared by polymerizing or copolymerizing by a conventionally known polymerization method such as a vapor phase method, a bulk method, or a slurry method.

The modified polyolefin is obtained by grafting the above ethylene homopolymer, ethylene / α-olefin copolymer, propylene homopolymer, propylene / α-olefin copolymer and the like with an unsaturated carboxylic acid or a derivative thereof. ..

Examples of unsaturated carboxylic acids or derivatives thereof (such as unsaturated carboxylic acids) for obtaining modified polyolefins include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid and itaconic acid; maleic anhydride, Acid anhydrides such as itaconic anhydride, norbornenecarboxylic acid anhydride, tetrahydrophthalic acid anhydride; hydroxyalkyl esters such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl acrylate, hydroxyethoxymethacrylate or hydroxyalkoxyalkyl esters. Etc. are included. In particular, maleic anhydride is preferably used. These unsaturated carboxylic acids or derivatives thereof can be used alone or in combination of two or more.

The graft ratio of the modified polyolefin is preferably 0.01 to 10% by mass, more preferably 0.1 to 5% by mass, in terms of graft monomers such as unsaturated carboxylic acid, with respect to 100% by mass of the polyolefin before graft modification. When the graft ratio is within the above range, a food packaging material that is highly branched, has good mutual entanglement, and has high ceramic powder retention can be obtained.

The modified polyolefin can be prepared by a conventionally known graft modification method for polyolefin. For example, a modified polyolefin can be prepared by reacting a polyolefin with an unsaturated carboxylic acid or a derivative thereof without a solvent using an extruder or the like. The reaction temperature at this time can be about 120 to 350 ° C.

At the time of graft modification, it is preferable to carry out the graft reaction in the presence of a radical initiator in order to carry out the graft copolymerization efficiently. The radical initiator is usually preferably used in an amount of 0.001 to 1 part by mass, more preferably 0.01 to 0.5 part by mass, based on 100 parts by mass of the polyolefin.

As such a radical initiator, an organic peroxide, an organic peroxide, an azo compound and the like can be used. Examples of such radical initiators include benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di (peroxide benzoate) hexin-3,1 , 4-Bis (t-butylperoxyisopropyl) benzene, lauroyl peroxide, t-butylperacetate, 2,5-dimethyl-2,5-di- (t-butylperoxy) hexin-3,2,5-dimethyl- 2,5-Di (t-butylperoxy) hexane; t-butylperbenzoate, t-butylperphenylacetate, t-butylperisobutyrate, t-butylper-sec-octate, t-butylperpivalate, ku Milperpivalate and t-butylperdiethyl acetate; azobisisobutyronitrile, dimethylazoisobutyrate and the like are included. Among these, dicumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexin-3, 2,5-dimethyl-2,5-di (t-). Dialkyl peroxides such as butylperoxy) hexane and 1,4-bis (t-butylperoxyisopropyl) benzene are preferred.

As the polyolefin synthetic pulp, a commercially available product may be used. Examples of commercially available products of polyolefin synthetic pulp include SWP (trade name) manufactured by Mitsui Chemicals, Inc.

The Canadian drainage degree of the polyolefin synthetic pulp is 100 ml or more and 520 ml, more preferably 300 to 400 ml. When the Canadian drainage level is within this range, it is possible to appropriately evaporate the water generated from the food wrapped in the food wrapping paper to the outside, and store it in an appropriate state without excessively permeating the water. can. The Canadian drainage degree is a value measured in accordance with JIS P-8121.

Here, the melting point of the polyolefin synthetic pulp is preferably 70 ° C. to 160 ° C., more preferably 80 ° C. to 150 ° C., and even more preferably 90 ° C. to 140 ° C. Generally, the melting point of synthetic pulp depends on the melting point of the polyolefins that compose it. When the melting point of the polyolefin synthetic pulp is 160 ° C. or lower, food wrapping paper can be produced at a relatively low temperature. On the other hand, when the melting point of the polyolefin synthetic pulp is 70 ° C. or higher, the heat resistance of the obtained food wrapping paper is enhanced. The melting point of polyolefin synthetic pulp is measured by a differential scanning calorimeter.

The average fiber length of the polyolefin synthetic pulp is preferably 0.05 to 50 mm, more preferably 0.05 to 10 mm, still more preferably 0.1 to 3 mm. The fiber length and average fiber length can be adjusted by processing with, for example, a disc type refiner.

Here, the average fiber length of the polyolefin synthetic pulp can be obtained by the following procedure. The fibers constituting the polyolefin synthetic pulp are classified in increments of 0.05 mm in length. After that, the measured fiber length of the fibers included in each class (length) and the number of fibers included in each class are measured. The measurement may be performed on 12,000 to 13,000 fibers. Then, from the above measurement results, the number average fiber length Ln (mm) of each class is obtained by the following formula.
Ln = ΣL / N
L: Measured fiber length (mm) of fibers contained in one class
N: Number of fibers contained in one class The average fiber length (mm) of the fibers constituting the polyolefin synthetic pulp is obtained by the following formula.
Average fiber length = Σ (Nn × Ln ³ ) / Σ (Nn × Ln ² )
Nn: Number of fibers included in each class

On the other hand, for the above fiber length, synthetic pulp is dispersed in water so that the concentration becomes 0.02% by mass, and each fiber is used with an automatic fiber measuring machine (product name: Valmet FS5) manufactured by Valmet Automation Co., Ltd. It can be obtained by measuring the length. In the measuring machine, the fibers flowing in the capillary are irradiated with xenon lamp light, a video signal is collected by a CCD (charge-coupled device) sensor, and image analysis is performed. The average fiber length is expressed as a weight average.

The amount of the polyolefin synthetic pulp with respect to the total amount of the food wrapping paper is preferably 10 to 80% by mass, more preferably 20 to 60% by mass. When the amount of the polyolefin synthetic pulp is 10% by mass or more, the ceramic powder can be sufficiently retained, and a high-strength food wrapping paper can be obtained. On the other hand, when the amount of the polyolefin synthetic pulp is 80% by mass or less, the amount of the ceramic powder is relatively sufficient, and the amount of far infrared rays at the time of heating can be sufficiently sufficient.

-Ceramic powder The ceramic powder may be an inorganic compound that generates far infrared rays when heated. From the viewpoint of generating (radiating) far infrared rays by heating in a microwave oven, inorganic compounds containing conductive powders such as Fe, Al, Au, Ag, Cu, and Si are preferable.

Examples of the ceramic powder is cordierite _{(2MgO · 2Al 2 O 3 ·} 5SiO 2), mullite _{(3Al 2 O 3 · 2SiO 2} ), petalite (LiAlSi ₄ O _10), rhyolite _(SiO 2), clay _{(2Al 2 O 3 · 2H 2} O), include alumina _(Al 2 _{O 3).} The food wrapping paper may contain only one type of ceramic powder, or may contain two or more types of ceramic powder.

Here, it is preferable that the ceramic powder is dispersedly arranged in the food wrapping paper. The ceramic powder may be adhered to, for example, the surface of the above-mentioned polyolefin synthetic pulp, or may be kneaded into the polyolefin synthetic pulp.

The average particle size of the ceramic powder is preferably 1 to 500 μm, more preferably 10 to 300 μm. When the average particle size of the ceramic powder is within this range, the ceramic powder is less likely to fall off from the food wrapping paper. For the average particle size of the ceramic powder, the catalog value may be adopted when the catalog value exists, and when the catalog value does not exist, the average particle size may be measured by a laser diffraction type particle size measuring device. As the particle size measuring device, SALD-2000J manufactured by Shimadzu Corporation, Coulter counter manufactured by Coulter Co., Ltd., and Microtrack particle size distribution measuring device manufactured by Nikkiso Co., Ltd. are preferably used, and SALD-2000J manufactured by Shimadzu Co., Ltd. is more preferably used.

The amount of the ceramic powder is preferably 1 to 10% by mass, more preferably 3 to 8% by mass, based on the total amount of the food wrapping paper. When the amount of the ceramic powder is 3% by mass or more, the amount of far infrared rays at the time of heating can be sufficiently increased. On the other hand, when the amount of the ceramic powder is 10% by mass or less, the flexibility of the food wrapping paper becomes high, and it can be applied to various foods.

-Natural pulp As mentioned above, food wrapping paper contains natural pulp. As used herein, the natural pulp is a pulp containing natural fibers. Natural pulp includes wood pulp and non-wood pulp.

Wood pulp is pulp obtained from wood such as softwood and hardwood. Specifically, these trees are subjected to a chemical pulping method represented by the craft method, the soda method and the sulfite method, a semi-chemical pulping method represented by the neutral sulfite method and the acidic sulfite method, and others. It can be pulped by a known pulping method. Among these, softwood kraft pulp (NBKP) is preferable from the viewpoint of further improving the strength.

On the other hand, non-wood pulp is pulp obtained from raw materials other than wood. Examples of raw materials other than wood include plant fiber. Plant fibers include bast fibers composed of Manila hemp, flax, cannabis, mulberry, mulberry, honey or ganpi; cotton such as cotton and cotton linter; straw; bamboo; esparto; bagasse and the like. These plant fibers are obtained by pulping them by a known pulping method such as a chemical pulping method, a semi-chemical pulping method, a chemigrand pulping method, or a mechanical pulping method. Non-wood pulp may contain a plurality of types of plant fibers. Among these, non-wood pulp containing Manila hemp is preferable because of its availability, supply amount, and the like.

The natural pulp may contain one kind of wood pulp or non-wood pulp, and may contain a plurality of kinds of wood pulp and / or non-wood pulp.

The fiber length of the natural pulp is preferably 1 mm to 80 mm, more preferably 2 mm to 50 mm, from the viewpoint of the strength of the food wrapping paper and the like. The fiber length of natural pulp is measured in the same manner as the fiber length of polyolefin synthetic pulp.

Here, the amount of the above-mentioned natural pulp is preferably 10 to 70% by mass, more preferably 32 to 60% by mass, based on the total mass of the food wrapping paper. When the amount of natural pulp is within the above range, the texture and texture of the food wrapping paper are improved.

-Binder fiber As described above, the food wrapping paper may contain a binder fiber. The binder fiber is not particularly limited as long as it can be made into paper. By blending the binder fiber into the food wrapping paper, the tensile strength of the food wrapping paper can be improved. From the viewpoint of preventing paper breakage when the wrapping paper is dried, the binder fiber preferably contains fibers having a melting point of 70 ° C. or higher and 130 ° C. or lower, and contains fibers having a melting point of 100 ° C. or higher and 120 ° C. or lower. Is more preferable.

Examples of such binder fibers include synthetic fibers. Specific examples include polyethylene fibers, low melting point polyester fibers, acrylic fibers, polyethylene / polypropylene composite fibers, polyethylene / polyethylene terephthalate composite fibers, polyester composite fibers and the like.

The form of the binder fiber may be short fiber or long fiber as long as the effect of the present invention is not impaired, but the average fiber length is preferably 0.1 to 20 mm, preferably 1 to 10 mm. If the average fiber length is within this range, the composition containing the binder fiber can be substantially made into a sheet, and a uniform food wrapping paper tends to be obtained. Further, such a binder fiber can be used for wet papermaking.

The average fiber length of the binder fiber is the same as the average fiber length of synthetic pulp, using a general fiber length distribution measuring device (for example, an automatic fiber measuring machine manufactured by Valmet Automation (product name: Valmet FS5)). It is a value measured by.

The ratio of the binder fiber contained in the food wrapping paper is preferably in the range of 1% by mass or more and 50% by mass or less, more preferably 5% by mass or more and 30% by mass or less, based on the total mass of the food wrapping paper. By including the binder fiber within this range, the paper breakage when the food wrapping paper is dried tends to be prevented, and the tensile strength of the food wrapping paper tends to be improved.

-Other Ingredients In addition to the above-mentioned polyolefin synthetic pulp, ceramic powder, and natural pulp, the food wrapping paper may contain other ingredients as long as the object and effect of the present invention are not impaired. Examples of other ingredients include dry paper strength agents, wet paper strength agents, yield improvers, coagulants, flocculants, dispersants, mold release agents, defoamers, bactericides, antibacterial agents, heat stabilizers, weather resistance. Includes stabilizers, various stabilizers, antioxidants, dispersants, antistatic agents, slip agents, antiblocking agents, antifoaming agents, lubricants, dyes, natural oils, synthetic oils, waxes, fillers and the like.

-Physical Properties of Food Wrapping Paper The air permeability of the food wrapping paper of the present invention is 5 to 200 cc / cm ² / s, more preferably 20 to 100 cc / cm ² / s. When the air permeability of the food wrapping paper is 5 cc / cm ² / s or more, the water generated from the food can be appropriately transpired during storage or heating. On the other hand, when the air permeability is 200 cc / cm ² / s or less, it becomes difficult for the food to dry during storage or heating. The above air permeability is a value measured in accordance with JIS L1096, and is measured by a Frazier air permeability measuring machine.

The basis weight of the food wrap is preferably ^{5~40g / m 2, 10~30g / m} 2 is more preferable. When the basis weight of the food wrapping paper is within the above range, the air permeability can be easily adjusted within the above range, which is also preferable from the viewpoint of cost.

Further, the thickness of the food wrapping paper is preferably 20 to 300 μm, more preferably 40 to 150 μm. When the thickness of the food wrapping paper is within the above range, the strength is high and it is difficult to tear when the food is wrapped.

-Method for producing food wrapping paper The method for producing food wrapping paper is not particularly limited. For example, a slurry containing the above-mentioned polyolefin synthetic pulp, ceramic powder, and other components is prepared, and the slurry is made into paper. It may be produced.

-Use of food wrapping paper The food wrapping paper of the present invention can be used for storing various foods and for cooking. As mentioned above, food wrapping paper generates far infrared rays when heated. Therefore, it is particularly suitable for applications in which food is wrapped inside a food wrapping paper and the food is cooked in a microwave oven or the like while being wrapped in the food wrapping paper.

The type of food to be wrapped with food wrapping paper is not particularly limited, and can be used for storage or cooking of rice, vegetables, meat, fish, etc.

The shape of the food wrapping paper is not particularly limited, and may be, for example, a sheet shape, a bag shape, a box shape, or the like.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the scope of the present invention is not limited by this.

1. 1. Preparation of materials (1) Polyolefin synthetic pulp (A)
As the polyolefin synthetic pulp (A), the following polyolefin synthetic pulp (A-1) and polyolefin synthetic pulp (A-2) were used.
-Polyolefin synthetic pulp (A-1): Polyethylene-based synthetic pulp produced by the method described below, Canadian drainage degree: 350 ml
-Polyolefin synthetic pulp (A-2): SWP E620 ("SWP" is a registered trademark of Mitsui Chemicals, Inc.), manufactured by Mitsui Chemicals, Canadian drainage degree: 340 ml

(Method for Producing Polyolefin Synthetic Pulp (A-1))
20 liters of n-hexane (23 ° C), 20 liters of water (23 ° C), polyethylene resin (MFR measured according to ASTM D1238): 4.0 g / in an autoclave with a stirrer in an 80 liter container equipped with a baffle plate. 10 minutes (190 ° C, 2.16 kg load)) 1000 g, and polyvinyl alcohol (trade name: Gosenol NL-05, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., saponification degree 99%, 4% aqueous solution viscosity at 20 ° C 4.6 to 6.0 mPa · s) 30 g was added. The temperature of the mixture was raised to 145 ° C. while stirring at a rotation speed of 900 rpm.

Then, the mixture was kept at 145 ° C., and stirring was continued for another 30 minutes. Next, this suspension was ejected (flushed) into a drum under a nitrogen atmosphere and a pressure of −400 mmHg through a hole having a diameter of 3 mm and a length of 20 mm attached to an autoclave to obtain a fibrous substance. ..

The obtained fibrous material was further prepared into a water slurry having a concentration of 3 g / liter in the receptor. Then, using a disc-type refiner having a diameter of 12 inches, the fiber length and the Canadian standard drainage degree were adjusted to obtain a polyolefin synthetic pulp (A-1).

(2) Natural pulp (B)
As the natural pulp (B), the following natural pulp (B-1) and natural pulp (B-2) were used.
-Natural pulp (B-1): Softwood kraft pulp (NBKP), manufactured by Mitsui Bussan Packaging Co., Ltd., average fiber length: 4 mm
-Natural pulp (B-2): Manila hemp pulp (Abaca pulp), manufactured by Mitsui Bussan Packaging Co., Ltd., average fiber length: 10 mm

(3) Ceramic powder (C)
As the ceramic powder (C), the following ceramic powder (C-1) and ceramic powder (C-2) were used.
-Ceramic powder (C-1): Matera powder, average particle size 25 μm (Ryumoniwa), manufactured by Matera Co., Ltd.-Ceramic powder (C-2): Heat-generating ceramic balls (clay, cordierite, petalite) with an average particle size of 50 μm , Alumina, iron, and aluminum), manufactured by Nagano Ceramics Co., Ltd.

(4) Others As other components, the following binder fiber, polyethylene fiber (a-1), and HDPE were used.
-Binder fiber: Low melting point polyester fiber, N720, manufactured by Kuraray (melting point 110 ° C, fiber length 5 mm)
-Polyethylene fiber: Shortcut fiber made of polyethylene, made by Daiwabo Co., Ltd., fiber length 3 mm
-HDPE: High-density polyethylene Hi-Zex 2200J, manufactured by Prime Polymer Co., Ltd.

<Example 1>
40 parts by mass of polyolefin synthetic pulp (A-1), 40 parts by mass of natural pulp (B-1), 5 parts by mass of natural pulp (B-2), 5 parts by mass of ceramic powder (C-1), 10 parts by mass of binder fiber , And 2 liters of water were added to JIS type pulper and stirred and mixed for 10 minutes to obtain an aqueous slurry.

Next, using this water slurry, a mixed paper machine having a basis weight of 20 g / m ² was prepared by a 250 mm square paper machine. This mixed paper was dried in a rotary dryer having a surface temperature of 110 ° C. for 2 minutes. Then, the heat treatment was further carried out at a surface temperature of 135 ° C. for 2 minutes to obtain a food wrapping paper. The thickness of the food wrapping paper was 60 μm.

<Example 2>
A food wrapping paper was obtained in the same manner as in Example 1 except that the ceramic powder (C-2) was used instead of the ceramic powder (C-1).

<Example 3>
A food wrapping paper was obtained in the same manner as in Example 1 except that the polyolefin synthetic pulp (A-2) was used instead of the polyolefin synthetic pulp (A-1).

<Comparative example 1>
A food wrapping paper was obtained in the same manner as in Example 1 except that polyethylene fibers were used instead of the polyolefin synthetic pulp (A-1).

<Comparative example 2>
95 parts by mass of HDPE and 5 parts by mass of ceramic powder (C-1) were supplied to a 30 mmφ extruder of a cast film molding machine having a coat hanger type die having a width of 300 mm. Then, it was extruded at a temperature of 240 ° C. and then rapidly cooled with a metal roll to form a 30 μm-thick food wrapping paper (film). Then, the obtained molded film was evaluated in the same manner as in Example 1.

<Comparative example 3>
In Example 1, without using ceramic powder (C-1), 40 parts by mass of polyolefin synthetic pulp (A-1), 45 parts by mass of natural pulp (B-1), 5 parts by mass of natural pulp (B-2), binder. A food wrapping paper was obtained in the same manner as in Example 1 except that 10 parts by mass of fibers were used.

<Evaluation>
By the following methods, the basis weight of the obtained food wrapping paper, the ceramic powder retention rate, the aeration amount, and the texture of the rice heated while wrapped in the food wrapping paper were evaluated. The results are shown in Table 1.

(Basis weight)
The basis weight of the obtained food wrapping paper was measured by the method specified in JIS P 8124 (2011).

(Ceramic powder retention rate)
The mass of the obtained food wrapping paper was measured in advance, and the initial content of the ceramic powder was calculated from the ratio of the charged amount. The food wrapping paper was tapped by hand to remove the unretained ceramic powder. The food wrapping paper was then incinerated to give a residue. The mass of the residue was measured, and the obtained value was used as the mass of the ceramic powder after scraping. The retention rate of the ceramic powder was calculated from the following formula.
Ceramic powder retention rate (%) = mass of ceramic powder after wiping off / initial content of ceramic powder

(Breathability)
The air permeability of the food wrapping paper produced in each Example and Comparative Example was measured by a Frazier air permeability measuring machine according to JIS L1096.

(Paper thickness)
The thickness of the obtained food wrapping paper was measured by the method specified in JIS P 8118 (2014).

(Evaluation of texture of rice)
100 g of rice cooked in an electric rice cooker was wrapped in the food wrapping paper prepared in each Example and Comparative Example. Then, after storing in a refrigerator having an internal temperature of 5 ° C. for 24 hours, the mixture was heated in a 500 W microwave oven for 60 seconds. Then, the elasticity (texture) of the cooked rice was evaluated on the following five grades. A score of 4 or higher was evaluated as passing.
5 points: Texture similar to that of freshly cooked in a microwave oven 4 points: Inferior to 5 points, but better than 3 points 3 points: Not wrapped in food wrapping paper, but placed on a plate Same texture as when stored and heated in a microwave oven 2 points: Inferior to 3 points, but better than 1 point 1 point: Store on a plate without wrapping in food wrapping paper And the same texture as before heating in the microwave

As shown in Table 1, the food wrapping paper containing the synthetic pulp and the ceramic powder had a high retention rate of the ceramic powder (Examples 1 to 3). Moreover, in the food wrapping paper, the texture of rice was very good. Even if it was stored in a refrigerator, it had an appropriate air permeability, so that it was less likely to become sticky, and it is considered that the far-infrared effect of the ceramic powder provided the same texture as immediately after cooking.

On the other hand, in the food wrapping paper containing polyethylene fibers and ceramic fibers, the retention rate of the ceramic powder was very poor (Comparative Example 1). Therefore, it is probable that the far-infrared effect could not be obtained. In addition, when high-density polyethylene was used instead of synthetic pulp or natural pulp, the retention rate of ceramic powder was high, but when heated in a microwave oven, the wrapping burst due to expansion due to excess moisture. (Comparative example 2). In addition, the excess water made the rice sticky. A simple synthetic paper containing no ceramic powder was not sticky due to excess moisture, but had no effect due to far infrared rays, and a good texture could not be obtained (Comparative Example 3).

The food wrapping paper of the present invention can heat food evenly and uniformly by heating in a microwave oven or the like. Therefore, it is very useful when storing and cooking various foods.

Claims (7)

Polyolefin synthetic pulp having a Canadian standard drainage degree of 100 ml or more and 520 ml or less, ceramic powder that generates far infrared rays by heating, and natural pulp.
Including
The air permeability is 5 to 200 cc / cm ² / s.
Food wrapping paper. Basis weight is 5-40 g / m ² .
The food wrapping paper according to claim 1. The ceramic powder is at least one selected from the group consisting of corgerite, mullite, petalite, rhyolite, clay, and alumina.
The food wrapping paper according to claim 1 or 2. The content of the polyolefin synthetic pulp is 10 to 80% by mass.
The food wrapping paper according to any one of claims 1 to 3. The content of the ceramic powder is 1 to 10% by mass.
The food wrapping paper according to any one of claims 1 to 4. For microwave heating,
The food wrapping paper according to any one of claims 1 to 5. The step of wrapping the material with the food wrapping paper according to any one of claims 1 to 6.
The process of heating the material in a microwave oven while wrapped in the food wrapping paper,
A method of manufacturing a food product.