JP4808140B2 - Food packaging sheet - Google Patents

Description

  The present invention relates to a food packaging sheet used for packaging food such as bread and rice balls.

In general, for foods such as bread, rice balls and confectionery, packaging with a transparent film is well known.
In recent years, a wrapping paper having a transparent film on the inner side and a Japanese paper-like texture on the outer side is also seen as in Patent Document 1 in order to give a high-class feeling due to the wrapping paper texture.

  On the other hand, in the case of film packaging with high hermeticity in bread wrapping, steam such as fresh bread remains inside the packaging sheet and adheres to the outside of the bread, losing the crispness of the surface in French bread, melon bread, etc. There was a problem.

  In the case of paper packaging, there is a problem that the tight feeling inside the bread is lost by drying because foreign matters such as paper dust are mixed and air permeability is large. Furthermore, since the main component is paper, it is necessary to display a “paper mark” based on the Containers and Packaging Recycling Law, and it is avoided by consumers from the image of hygiene compared to “Plamark”, which is plastic. Sometimes.

As a method of giving a high-quality paper texture and appropriate air permeability, it is conceivable to bond the air-permeable film of Patent Document 2 and a base material having a paper texture. The air permeability is lost by bonding the adhesive or the like, and the effect is reduced.
In addition, when the paper and the film are bonded together, the paper expands and contracts due to moisture absorption and release, which causes a problem of curling of the packaging sheet.

JP 2004-262536 A JP 2002-370320 A

  The present invention has been made under the technical background as described above, and has an object to provide a food packaging sheet having a high-class feeling due to the texture of paper and also having appropriate air permeability. is there.

  The food packaging sheet of the present invention is configured as follows in order to achieve the above object.

  That is, the sheet for food packaging of the present invention first includes an outer layer (FIG. 1: reference numeral 1) containing at least natural fibers and synthetic fibers, and an inner layer (FIG. 1: reference numeral 2) containing synthetic fibers having heat sealing properties. In addition to this, the sheet S as a whole is heat-sealable food packaging sheet (Fig. 1: symbol S), and the sheet S as a whole has a synthetic fiber as a main component (50% or more). Further, the synthetic fiber content ratio of the inner layer and the outer layer is basically set such that (synthetic fiber content% of the inner layer) − (synthetic fiber content% of the outer layer) is 0 to 55.

  As natural fiber, softwood kraft pulp (NKP) is strong, and entanglement with synthetic fiber is also preferable.

  As synthetic fibers, polyolefin fibers such as polypropylene fibers (PP) and polyethylene fibers (PE), low melting point polyethylene terephthalate fibers (PET), acrylic fibers and the like can be used. Polyolefin fibers are fluid. The melting point is 100 to 160 ° C., which is preferable because an appropriate hermeticity can be obtained by heat processing. Polyethylene fibers are particularly preferable because they can be easily formed by heat processing. Moreover, it is preferable that the synthetic fiber has a fibrillated shape because the fiber is easily entangled, so that the sheet strength can be increased, and the fiber can be easily melted at the time of heat sealing to improve the sealing property.

  As a chemical internally added to the raw material, it is preferable to add a wet paper strength agent because the bond between natural fibers can be strengthened. Wet paper strength agents include amphoteric polyacrylamide, polyamide epichlorohydrin, etc., but since polyamide epichlorohydrin can strengthen not only between natural fibers but also between natural fibers and synthetic fibers, preferable. The addition amount is preferably 5 to 30 kg, particularly preferably 10 to 25 kg, per 1 t of the absolutely dry raw material fiber. If it is less than 5 kg, there is no effect, and if it exceeds 30 kg, excessive addition occurs, and dirt in the system is incorporated as a foreign substance, making it unsuitable for food packaging.

  In order to improve water resistance and printability, it is preferable to add a sizing agent such as alkyl ketene dimer (AKD) or alkenyl succinic anhydride (ASA). In particular, AKD should be added to the inner layer having heat sealability. And is particularly preferable because it has an effect of reducing fusion to a dryer or calendar roll. The amount of addition is preferably 2 to 10 kg, particularly 3 to 7 kg, based on 1 t of absolutely dry raw fiber. If it is less than 2 kg, there is no effect, and if it exceeds 10 kg, excessive addition is made, and dirt in the system is incorporated as a foreign substance, making it unsuitable for food packaging.

  The sheet S is formed by combining the outer layer 1 and the inner layer 2. In addition, the inner layer 2 is a layer bonded by heat sealing (FIG. 1: code | symbol H) at the time of packaging.

In the outer layer and the inner layer, the synthetic fiber content ratio in the absolutely dry raw material fiber of the inner layer should be increased, and (the synthetic fiber content rate% of the inner layer) − (the synthetic fiber content rate% of the outer layer) should be 55 or less. preferable. If it exceeds 55 , the structural difference between the outer layer and the inner layer is large, curling occurs, and bag making is difficult. Moreover, since it is possible to fuse only the inner layer without fusing the outer layer at the time of sealing to the heat sealing machine by setting it to 0 or more, especially 10 or more, the outer layer is fused to the heat sealing machine. It is not preferable because there is a fear).

  The synthetic fiber content ratio of the entire inner layer + outer layer sheet is preferably 50 to 95%. If it is less than 50%, the synthetic fiber is not the main component in the entire sheet, and the “Plamark” display based on the Containers and Packaging Recycling Law cannot be achieved, and / or the outer layer may be fused at the time of heat sealing. If it exceeds 95%, the texture and air permeability of the paper is lost, water vapor when freshly baked in melon bread or the like remains, and the crispness on the surface of the bread (FIG. 1: reference B) is lost.

  It is preferable that the outer layer and the inner layer have the same amount of rice tsubo or the outer layer has a high rice tsubo because of excellent curl suitability, and the total rice tsubo after combining is about 20 to 100 g / m 2.

  As a manufacturing method, the outer layer and the inner layer are made by a known paper machine such as a long mesh, a short mesh, a circular mesh, etc., and after laminating and laminating, a combination of an elastic roll and a metal roll at about 130 to 150 ° C. A synthetic fiber is melted by a soft calender or a super calender and heat-processed to obtain an appropriate air permeability, and a product molded by heat that satisfies the conditions of “Plamark” display can be obtained.

  Hereinafter, preferred embodiments of the food packaging sheet of the present invention will be described.

Natural fiber:
Softwood bleached kraft pulp (NBKP): Canadian Freeness 500cc
Synthetic fibers:
Polyethylene fiber (Mitsui Chemicals, product number: SWP E-400)
See Table 1 for the mixing ratio.

Internal chemicals:
Polyamide epichlorohydrin wet paper strength agent: (manufactured by Seiko PMC, product number: WS4024)
20 kg of active ingredient added to 1 t of absolutely dry raw material Alkyl ketene dimer (AKD) sizing agent: (manufactured by Seiko PMC, AD1602)
* Inner layer only 5kg of active ingredient is added to 1t of absolutely dry raw material. The above raw materials are made by the inner layer: short net paper machine and the outer layer: circular net paper machine so that the dry weight is 15g / m2 respectively. Papermaking was carried out, and the inner and outer layers were 30 g / m2. Furthermore, the synthetic fiber was melted and heat-processed by a machine calendar (metal roll temperature: 140 ° C.) treatment.

  As the conventional product, an OPP film (manufactured by Futamura Chemical Co., Ltd., product number: FOH # 25) and rayon paper (10 g / m 2) bonded by dry lamination was used.

  Synthetic fiber blending ratio: Synthetic fiber blending ratio (%) in the absolutely dry raw fiber of the inner layer and outer layer. The remaining raw fiber was NBKP.

Synthetic fiber ratio difference: (Synthetic fiber content% in inner layer)-(Synthetic fiber content% in outer layer)
Plastic mark display: The synthetic fiber ratio of the entire sheet is 50% or more.
×: Plastic mark cannot be displayed.

  Curl: The curl was visually evaluated on the desk and suspended while the sheet was at a temperature of 23 ° C. and the humidity was changed from 20% to 80%.

A: No curling was observed on the desk or in the suspended state.
◯: Slightly curled in the suspended state, but no curling is seen on the desk, and there is no problem in practical use.
X: Curling was seen both on the desk and in the suspended state.

  Melon bread crispness: Evaluate whether there is crispness on the surface of the melon bread 3 days after production.

A: There was a clear crispy texture.
○: I felt crispy.
X: Lack of crispness.

  Heat sealing property: The inner layers were heat sealed with a sealing machine at a sealing temperature of 160 ° C. and a pressure of 0.5 kg / cm 2 for evaluation.

A: The inner layers could be heat sealed without any problem.
A: Melting was observed in the outer layer, but the inner layer was heat-sealed without adhesion to the sealing machine.
X: The outer layer melted and adhered to the sealing machine.

  Texture: 20 people evaluated whether the outer layer had a paper texture.

A: Evaluated that 90% or more of people had a paper texture.
○: 70% or more and less than 90% of people evaluated that they had a paper texture.
X: Less than 70% of the people evaluated to have a paper texture.

Comprehensive evaluation As is clear from Table 1, the food packaging sheets of Examples 2 to 7 that satisfy all of the requirements of the present invention are plastic mark display suitability, curling properties, and melon bread surface required for this type of food packaging sheet. ◎ or ○ evaluation was obtained in all the physical properties such as crispness, heat sealability of the inner layer, texture of the outer layer, etc. On the other hand, (synthetic fiber content rate% of the inner layer)-(containing the synthetic fiber of the outer layer) %) Was 65, and the sheet for food packaging of Comparative Example 2 was unqualified in curling property, and (synthetic fiber content% of the inner layer) − (synthetic fiber content% of the outer layer) was −5 (minus). The food packaging sheet of Comparative Example 3 was inconvenient in that the outer layer was fused to the heat sealing machine during heat sealing. In addition, the food packaging sheet of Comparative Example 1 having a value of (inner layer synthetic fiber content%)-(outer layer synthetic fiber content%) within the range of the requirements of the present invention is 15, curling and crisp on the surface of the melon bread. Although the physical properties such as feel, heat sealability, and outer layer texture were evaluated well, the synthetic fiber compounding ratio as a whole sheet did not reach 50% (47.5%), and the application of the plastic mark was not possible. It did not meet the purpose of the invention.

It is explanatory drawing of the state which packaged bread with the sheet | seat for food packaging concerning Example 1 of this invention.

  1 is an outer layer, 2 is an inner layer, B is a bread, S is a sheet for food packaging, and H is a heat seal part.

Claims (1)

In a heat-sealable food packaging sheet having a multilayer structure composed of an outer layer containing at least a natural fiber and a synthetic fiber, and an inner layer containing a synthetic fiber having heat sealability,
The natural fiber is a softwood kraft pulp,
The synthetic fiber contained in the outer layer and the inner layer is at least one of a polyolefin fiber, a low melting point polyethylene terephthalate fiber, and an acrylic fiber,
The synthetic fibers contained in the outer layer and / or inner layer are fibrillated,
The synthetic fiber content of the outer layer is 45 to 85%,
The synthetic fiber content of the entire sheet is 50% or more,
About the synthetic fiber content ratio of the said inner layer and an outer layer, the sheet | seat for food packaging whose (synthetic fiber content rate% of an inner layer)-(synthetic fiber content rate% of an outer layer) is 0-55.

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