JP5314527B2 - Food packaging material and rice ball packaging material - Google Patents

Description

  The present invention relates to a food packaging material in which the amount of water vapor permeation changes dramatically with temperature, and a packaging material for rice balls.

  Conventionally, packaging materials such as resin films and resin molded bodies have been widely used for the purpose of protecting and preserving food. In general, this type of food packaging material is required to have the ability to block the food to be packaged from the outside, that is, high sealing performance, thereby preventing exudation of moisture and liquid components to the outside of the package, dust and Prevention of food contamination due to entry of foreign matter into the package, and prevention of infection due to entry of pathogens such as bacteria and bacteria in the open air into the package have been realized. In addition, when a package of food containing a large amount of water or liquid components is stored for a long period of time in a low temperature environment such as a room temperature to a refrigerator, the water is lost over time and the food is dried. In order to prevent the original flavor and texture from being impaired, a food packaging material having excellent airtightness and more specifically having a small water vapor transmission amount is used.

  On the other hand, if the amount of water vapor permeated through the food packaging material is excessively small, water vapor from the food in the packaging body, such as packaging hot food immediately after cooking or heating the packaging body or the packaged goods in it from the outside, etc. When a large amount of is generated, the package may be deformed due to volume expansion, or the packaging material may be damaged in some cases, and the food may be scattered and contaminate the external environment. In addition, the water vapor generated condenses and condenses on the inner surface of the packaging material, which reabsorbs or partially stays on the surface of the food, causing the water content of the food to vary greatly depending on the site, resulting in the original flavor of the food. And quality deterioration such as a loss of texture. Furthermore, since a partial increase in the amount of water can promote the growth of bacteria and the like, it causes inconveniences such as difficulty in long-term storage and restrictions on the storage conditions.

  For this reason, attempts have been made to form a large number of holes of several millimeters in the resin film used as a packaging material in order to increase the amount of water vapor permeation. Is only implemented in some applications where high sealability is not required.

In order to solve this problem, in Patent Document 1, a thermoplastic resin film having a water vapor permeability of 500 to 4000 g · 30 μm / (m ² · 24 h, 40 ° C. · 90% RH) is formed on at least one side of the permeable substrate. A laminated film for bread packaging has been proposed. And, according to the laminated film for bread packaging, internal water vapor can be appropriately released through the water vapor permeable thermoplastic resin film without excessively impairing the sealing performance, so that the inside of the foreign material can be suppressed while preventing the entry of foreign matter. It is described that water vapor can be released to suppress condensation inside the packaging material and deformation of the package.

  In Patent Document 2, a urethane polymer film is laminated on at least one surface of the fiber fabric, the glass transition temperature of the urethane polymer film is in the range of 0 to 60 ° C., and A moisture-permeable waterproof fabric characterized in that the weight-average molecular weight of the polyurethane polymer is 15000 or more has been proposed. And since such a moisture-permeable waterproof fabric changes the amount of water vapor permeation depending on the outside air temperature, it is stated that if clothing is made using this, the body can be placed in a comfortable environment regardless of the outside air temperature. ing.

JP 2002-370320 A Japanese Patent No. 3074335

  However, the laminated film described in Patent Document 1 is specialized for bread packaging applications, and has a relatively high water vapor permeability. Therefore, foods other than bread, in particular, a large amount of moisture and liquid are used. When packaging foods containing ingredients, depending on the storage environment and period, the water vapor in the package is gradually released, the food is dried, and the original flavor and texture of the food are impaired. There was a problem that could be.

On the other hand, the moisture-permeable waterproof fabric described in Patent Document 2 is intended for apparel use and could not be diverted to food packaging use for the following reasons. That is, it is apparent from the examples that the moisture permeable waterproof fabric exhibits a moisture permeability of about 100 to 1000 g / (m ² · h) even in a low moisture permeable region. In addition, since the water vapor permeability is relatively high, when used for food packaging, depending on the storage environment and period, the water vapor in the package is gradually released and the food is dried, resulting in the original flavor and texture of the food. There was a problem of being easily damaged.
Furthermore, since the moisture-permeable waterproof fabric described in Patent Document 2 has high rigidity, when formed into a film, there is a problem that the followability and adhesion to packaged foods are poor. When molded into a container, there was a problem that the container shape could not be maintained due to insufficient strength. Moreover, the moisture-permeable waterproof fabric described in Patent Document 2 has a problem that transparency is low and visibility is poor, and it is difficult to confirm the state of the food to be packaged from the outside. Furthermore, the moisture-permeable waterproof fabric described in Patent Document 2 has a problem that the surface smoothness is inferior, and food easily enters the voids on the surface of the fabric, so that the peelability of the food adhering to the fabric surface is poor. It was.

  The present invention has been made in view of such problems, and its purpose is to increase not only foods with low water content such as bread, but also foods containing a large amount of moisture and liquid components over a long period of time. An object of the present invention is to provide a new and unique food packaging material that is excellent in versatility and that can be preserved in quality or can be used for cooking without packaging.

  As a result of earnest research, the present inventors are a moisture permeation control layer formed by molding a resin composition containing a thermoplastic resin, and the moisture permeation control in which a change in the amount of water vapor permeation due to temperature exhibits a specific behavior It has been found that the above-mentioned problems can be solved by employing a layer, and the present invention has been completed.

That is, the present invention provides (1) to (4) below.
(1) Temperature (° C.)-Water vapor transmission rate W _VTR (g / g) obtained by molding a resin composition containing a thermoplastic resin and measured under a humidity condition of 60% RH in accordance with the JIS L1099 A-2 method. In the plot chart of (m ² · h)), the increase in the water vapor transmission rate W _VTR from the reference temperature T _S (° C.) to T _S +10 (° C.) is changed from T _S −10 ° C. (° C.) to the reference temperature T _S ( has 100 times or less become the transition region more than double the increase in water vapor permeation amount W _VTR of ° C.), the transition region less than the water vapor permeation amount W _VTR at a temperature of ^{(g / (m 2 · h} )) is 0 It is at least one moisture permeation control layer that is greater than or equal to 50 and the reference temperature T _S (° C.) is in the range of 0 ° C. or more and 100 ° C. or less.
Food packaging material.

(2) The thermoplastic resin is a copolymer comprising two or more monomers, a polymer comprising one or more prepolymers and one or more monomers, a polymer blend of two or more polymers, and / or 2 A polymer complex of more than one polymer,
The food packaging material according to (1) above.

(3) On at least one surface of the moisture permeation control layer, a moisture permeation layer having a water vapor transmission amount W _VTR within a range of 0 ° C. or more and 100 ° C. or less is always larger than that of the moisture permeation control layer.
The food packaging material according to (1) or (2) above.

(4) including the food packaging material according to any one of (1) to (3) above,
Packaging for rice balls.

  According to the present invention, not only foods with a low water content such as bread but also foods containing a large amount of water and liquid components can be stored in high quality over a long period of time, or can be used for cooking without changing the package. A new, unique and versatile food packaging material that can be used is realized.

  That is, the food packaging material of the present invention is less than the transition region S, that is, in a relatively low temperature environment, has a small water vapor transmission amount and excellent water vapor barrier properties. Therefore, by using this to package food, a decrease in moisture over time when stored for a long time in a low temperature environment is sufficiently suppressed. Moreover, the food packaging material of the present invention has a large water vapor transmission amount and excellent moisture permeability in the transition region S or more, that is, in a relatively high temperature environment. Therefore, even if a large amount of water vapor is generated in the package when the food is packaged using this, deformation of the package due to volume expansion, damage to the packaging material, and accompanying scattering of food, condensation on the inner surface of the packaging material Occurrence of variations in the amount of moisture in foods and foods is suppressed. Therefore, by using the food packaging material of the present invention, it is possible to preserve food with high quality over a long period of time or to use the package as it is for cooking. Furthermore, since the food packaging material of the present invention can have excellent moldability, excellent transparency (visibility), and excellent surface smoothness as compared with the conventional ones, a film or a molded body can be provided. Various forms such as the above can be adopted, and the designability in product display and the like can be improved.

It is a graph for demonstrating the temperature dependence of the water vapor transmission rate of a food packaging material.

  Embodiments of the present invention will be described below. In addition, the following embodiment is an illustration for demonstrating this invention, and this invention is not limited only to the embodiment.

The food packaging material of this embodiment is provided with at least one moisture permeation control layer formed by molding a resin composition containing a thermoplastic resin, and this moisture permeation control layer complies with JIS L1099 A-2 method. In a plot chart of temperature (° C.)-Water vapor transmission rate W _VTR (g / (m ² · h)) measured under a humidity condition of 60% RH, from the reference temperature T _S (° C.) to T _S +10 (° C.) It has a transition region S the increased amount of water vapor permeation amount W _VTR of the T _S -10 ℃ (℃) reference temperature T _S (° C.) 100 times 2-fold increase of the water vapor permeation amount W _VTR follows from The water vapor transmission rate W _VTR (g / (m ² · h)) at a temperature lower than the transition region S is greater than 0 and 50 or less, and the reference temperature T _S (° C.) is 0 ° C. or more and 100 ° C. or less. It is characterized by being in the range of

In this specification, the water vapor transmission amount W _VTR means a value measured in accordance with JIS L1099 A-2 method, and means a value measured under a humidity condition of 60% RH unless otherwise specified. To do. In addition, since the food packaging material of the present embodiment shows the temperature dependency of the water vapor transmission amount, the measurement of the water vapor transmission amount W _VTR needs to be performed with various temperatures set for each test. Is performed every 10 ° C., more preferably every 5 ° C.

  Moreover, in this specification, a food packaging material means what is used in order to package the food which is a package for the purpose of preservation | save, movement, processing, protection, heating, cooling, etc. of food. The form of the food wrapping material is not particularly limited, and any form can be adopted depending on the purpose, and for example, a film, a sheet, a bag, a molded product such as a lidded container or a box can be taken. . Furthermore, in this specification, a package means the thing of the state by which the food was packaged with the food packaging material. In addition, food means all foods and drinks and is a concept that includes seasonings, food additives, and the like in addition to foods, fresh foods, processed foods, functional foods, foods for specified health use.

Moisture permeation control layer has a reference temperature T _S transition region S water vapor permeation amount W _VTR varies dramatically between the high-temperature region side and the low-temperature region side as a reference, this transition region S (reference temperature T _S) Is characterized in that the water vapor transmission amount W _VTR increases (decreases) specifically before and after. The transition region S includes an increase in the water vapor transmission rate W _VTR from the reference temperature T _S (° C.) to T _S +10 (° C.), and from the T _S −10 ° C. (° C.) to the reference temperature T _S (° C.). This is determined by comparing the increase in the water vapor transmission amount W _VTR .

Usually, in the range of 0 ° C. or more and 100 ° C. or less, the moisture is in an equilibrium state between the liquid and the gas, and in this range, problems such as drying of food and dew condensation in the package occur. Therefore, the reference temperature T _S needs to be set in the range of 0 ° C. or higher and 100 ° C. or lower, preferably in the range of 0 ° C. or higher and 80 ° C. or lower, more preferably in the range of 10 ° C. or higher and 60 ° C. or lower. . When the reference temperature T _S exceeds 100 ° C. and the reference temperature T _S is 0 ° C. or less, the fluctuation range of the water vapor transmission amount W _VTR within the temperature range of the practical packaging environment and storage environment is small. In the temperature range, since both functions of the moisture release effect and the drying suppression effect cannot be achieved, the food packaging material of this embodiment is not suitable. Note that the storage temperature of food during (long-term) storage converges near the storage environment temperature, and the storage time near the storage environment temperature occupies a large proportion. Therefore, in order to design with an emphasis on the drying suppression effect during long-term storage, it is preferable to set the reference temperature T _S to a temperature slightly higher than the recommended (long-term) storage environment temperature for each food to be packaged. On the other hand, in order to design a package that emphasizes the moisture-releasing effect, such as when the package or food in the package is heated by a microwave oven, oven, or other heating means or humidification heating means before opening, the temperature T _S is preferably set to a temperature slightly lower than the heating temperature of the food.

The water vapor transmission amount W _VTR (g / (m ² · h)) of the moisture permeation control layer at a temperature lower than the transition region S needs to be greater than 0 and 50 or less, preferably 1 or more and 30 or less. Preferably they are 5 or more and 20 or less. If the W _VTR at a temperature lower than the transition region S exceeds 50 (g / (m ² · h)), the water vapor barrier property is insufficient and the effect of suppressing the drying of the food is not effectively exhibited, and the environment is relatively low temperature. Even underneath, the water content of the food is quickly lost and the functions required for food packaging materials cannot be fully achieved.

On the other hand, the increase in the water vapor transmission rate W _VTR from the reference temperature T _S (° C.) to T _S +10 (° C.) is the water vapor transmission rate W from T _S −10 ° C. (° C.) to the reference temperature T _S (° C.). It must be 2 to 100 times the increase in _VTR , preferably 2 to 50 times, more preferably 3 to 20 times. By thus water vapor permeation amount W _VTR changes suddenly as a boundary the reference temperature T _S, excellent water vapor barrier properties at low temperature side than the reference temperature T _S is an excellent water vapor transmission at a high temperature side than the reference temperature T _S And both functions of moisture release effect and drying suppression effect are compatible. If the difference in the amount of increase in the water vapor transmission rate W _VTR exceeds 100 times, the water vapor transmission rate W _{VTR at a} temperature higher than the reference temperature T _S becomes too large, and the effect of inhibiting the drying of the food becomes insufficient. However, since the fluctuation range is small, it is impossible to achieve both functions of a moisture release effect and a drying suppression effect.

The moisture permeation control layer has a sufficiently low water vapor transmission rate W _VTR (g / (m ² · h)) at a temperature lower than the transition region S, while a water vapor transmission rate W _VTR (g / ( m ² · h)) shows a specific behavior that increases dramatically. In other words, the moisture permeation control layer functions as a water vapor barrier layer by exhibiting an excellent drying suppression effect until just before the reference temperature T _S , while the moisture release effect suddenly appears as the reference temperature T _S is exceeded. Functions as a water vapor permeable membrane. The reason why the food packaging material of the present embodiment exhibits the moisture permeation control effect optimized for food packaging due to this characteristic can be explained as follows.

FIG. 1 is a plot chart of temperature (° C.) − Water vapor transmission rate W _VTR (g / (m ² · h)) measured under a humidity condition of 60% RH in accordance with JIS L1099 A-2 method. The water vapor permeability of the conventional food packaging material shows the behavior of dotted line a or dotted line c in the figure. What is indicated by the dotted line a, for example, a porous food packaging material formed from nonwoven fabric or paper, has a sufficient amount of water vapor permeation in a region higher than the reference temperature T _S , so that water vapor is contained in the package at a high temperature. Although it is difficult to cause problems such as expansion of the package due to fullness or condensation on the inner surface of the packaging material, the amount of water vapor permeates even in the temperature range below the reference temperature T _S, so the food will be stored for a long time. Problems such as dryness, the original flavor and texture of foods, and contamination by foreign substances. Moreover, when it is what is shown by the dotted line c, for example, the commercially available food packaging wrap made of polyethylene, the packaging container made of polypropylene, etc., the water vapor permeability at the temperature below the reference temperature T _S is low and the water vapor barrier property is excellent. long but saved food dry or foreign objects in the hardly occurs a problem such that become intermixed, when the food for the water vapor permeation amount is smaller at a reference temperature T _S above the temperature region is such as warmed since The water vapor generated in the package cannot be fully discharged from the package body to the outside world, and the package body expands, the package material expands, the package material breaks, the dew condensation occurs on the inner surface of the package material, etc. It is difficult to avoid the problem, and it may cause a decrease in handleability due to enlargement of the package, a decrease in safety due to ejection of internal high-temperature steam, and the like. Table 1 specifically shows an example of the behavior of the water vapor transmission amount W _VTR (g / (m ² · h)) of the above-described typical representative packaging material.

注１）０℃以上１００℃以下の範囲内に水蒸気透過量Ｗ_VTRが飛躍的に増大する特異点を有さず、遷移領域Ｓが存在しない。０℃においても５０（ｇ／（ｍ²・ｈ））以上である。このような挙動を示す包装材を用いて中心温度８０℃のおにぎりを包装した後に２０℃にて８時間保管した場合、乾燥が生じ食味が損なわれ易く、そればかりか、異物が混入し易い。このような挙動を呈する包装材は、例えば、コットンリンターの再生セルロースをスパンボンド法により１０〜５０ｇ／ｍ²の坪量の不織布を形成することにより得ることができる。
注２）０℃以上１００℃以下の範囲内に水蒸気透過量Ｗ_VTRが飛躍的に増大する特異点を有さず、遷移領域Ｓが存在しない。８０℃においても５０（ｇ／（ｍ²・ｈ））未満である。このような挙動を示す包装材を用いて中心温度８０℃のおにぎりを包装した後に２０℃にて８時間保管した場合、包装材の内面に結露が発生して食味が損なわれ易い。このような挙動を呈する包装材は、例えば、軟質ポリ塩化ビニル樹脂等を融点以上で熱溶融して広幅のスリットから押し出して約５〜５０μｍ程度の厚みに製膜することにより得ることができる。

Note 1) There is no singular point where the water vapor transmission rate W _VTR dramatically increases within the range of 0 ° C. or higher and 100 ° C. or lower, and the transition region S does not exist. Even at 0 ° C., it is 50 (g / (m ² · h)) or more. When packaging a rice ball with a central temperature of 80 ° C. using a packaging material exhibiting such behavior and storing it at 20 ° C. for 8 hours, drying tends to occur and the taste is likely to be impaired, as well as foreign matters are likely to be mixed. A packaging material exhibiting such a behavior can be obtained, for example, by forming a nonwoven fabric having a basis weight of 10 to 50 g / m ² by using a spunbond method of regenerated cellulose of cotton linter.
Note 2) There is no singular point where the water vapor transmission rate W _VTR dramatically increases in the range of 0 ° C. or higher and 100 ° C. or lower, and the transition region S does not exist. Even at 80 ° C., it is less than 50 (g / (m ² · h)). When a rice ball with a central temperature of 80 ° C. is packaged using a packaging material exhibiting such a behavior and then stored at 20 ° C. for 8 hours, condensation is likely to occur on the inner surface of the packaging material, and the taste tends to be impaired. A packaging material exhibiting such behavior can be obtained, for example, by thermally melting a soft polyvinyl chloride resin or the like at a melting point or higher and extruding it from a wide slit to form a film having a thickness of about 5 to 50 μm.

On the other hand, the water vapor permeability of the food packaging material of this embodiment shows the behavior of the solid line b in the figure. As described above, the food packaging material of the present embodiment has a sufficiently small water vapor transmission rate in the temperature region below the reference temperature T _S , so that moisture release from the packaging body to the outside is suppressed, and as a result, the food is dried. It is suppressed. At this time, the humidity in the package can be increased in the temperature range below the reference temperature T _S, but the amount of water vapor generated is relatively small because it is in a relatively low temperature environment, and even if condensed water droplets are generated, the taste is good. There is no impact on hygiene and is negligible. On the other hand, as described above, the food packaging material of the present embodiment has a water vapor permeability so that the water vapor transmission amount increases remarkably as the temperature rises from around the reference temperature T _S , and the generated water vapor can be quickly released. . For this reason, it is difficult for condensation to occur on the inner surface of the packaging material, and adverse effects on the food due to water droplets generated by the condensation and expansion of the package are suppressed. Table 2 specifically shows a behavior example of the water vapor transmission amount W _VTR (g / (m ² · h)) of the food packaging material of the present embodiment.

注３）５０〜７０℃に遷移領域Ｓが存在し、基準温度Ｔ_Sが６０℃に存在する。このような挙動を示す食品包装材を用いて中心温度８０℃のおにぎりを包装した後に２０℃にて８時間保管した場合、結露の発生、食品の乾燥、食味の悪化、異物の混入は生じ難い。また、上記従来の不織布等の包装材に比して、視認性（透明性）、形状追従性、剥離性にも優れる。このような挙動を呈する食品包装材は、例えば、スチレン・ブタジエン共重合高分子（旭化成ケミカルズ株式会社製樹脂、商品名「アスマー」）を、融点以上で熱溶融して広幅のスリットから押し出して約５〜５０μｍ程度の厚みに製膜することにより得ることができる。
注４）２５〜４５℃に遷移領域Ｓが存在し、基準温度Ｔ_Sが３５℃に存在する。このような挙動を示す食品包装材を用いて中心温度８０℃のおにぎりを包装した後に２０℃にて８時間保管した場合、結露の発生、食品の乾燥、食味の悪化、異物の混入は生じ難い。また、上記従来の不織布等の包装材に比して、視認性（透明性）、形状追従性、剥離性にも優れる。このような挙動を呈する食品包装材は、例えば、４，４’−ジフェニルメタンジイソシアネートとポリプロピレングリコールを共重合させて得たウレタンプレポリマーをエチレングリコールと反応させて得られるウレタン系高分子を、融点以上で熱溶融して広幅のスリットから押し出して約５〜５０μｍ程度の厚みに製膜することにより得ることができる。

Note 3) The transition region S exists at 50 to 70 ° C., and the reference temperature T _S exists at 60 ° C. When packaging rice balls with a central temperature of 80 ° C. using a food packaging material exhibiting such behavior and storing them at 20 ° C. for 8 hours, the occurrence of condensation, drying of the food, deterioration of taste, and contamination with foreign substances are unlikely to occur. . Moreover, compared with the said conventional packaging materials, such as a nonwoven fabric, it is excellent also in visibility (transparency), shape followability, and peelability. A food packaging material exhibiting such a behavior is, for example, a styrene-butadiene copolymer polymer (resin made by Asahi Kasei Chemicals Corporation, trade name “Asmer”) that is melted at a temperature equal to or higher than the melting point and extruded from a wide slit. It can be obtained by forming a film to a thickness of about 5 to 50 μm.
Note 4) The transition region S exists at 25 to 45 ° C., and the reference temperature T _S exists at 35 ° C. When packaging rice balls with a central temperature of 80 ° C. using a food packaging material exhibiting such behavior and storing them at 20 ° C. for 8 hours, the occurrence of condensation, drying of the food, deterioration of taste, and contamination with foreign substances are unlikely to occur. . Moreover, compared with the said conventional packaging materials, such as a nonwoven fabric, it is excellent also in visibility (transparency), shape followability, and peelability. The food packaging material exhibiting such a behavior is, for example, a urethane polymer obtained by reacting a urethane prepolymer obtained by copolymerizing 4,4′-diphenylmethane diisocyanate and polypropylene glycol with ethylene glycol, having a melting point or higher. It can be obtained by heat melting and extruding from a wide slit to form a film having a thickness of about 5 to 50 μm.

  The moisture permeation control layer of the food packaging material of this embodiment can be obtained by molding a resin composition containing a thermoplastic resin. More specifically, using a thermoplastic resin obtained by polymerizing or blending a plurality of components having different glass transition temperatures, melting points, crystallinity, molecular weight, molecular chain length, steric structure, molecular gap, polarity, hydrophilicity, etc. By molding a resin composition containing such a thermoplastic resin, a moisture permeation control layer in which water vapor permeability (temperature dependence of water vapor transmission amount) is controlled within the above range can be easily obtained.

  Although it does not specifically limit as a specific example of the thermoplastic resin which comprises a moisture-permeable control layer, For example, the copolymer (preferably a block copolymer or a graft copolymer) which consists of 2 or more types of monomers, 1 type Polymers comprising the above prepolymers and one or more monomers (preferably block copolymers or graft copolymers), polymer blends of two or more polymers (including physical blends, chemical blends, polymer alloys) And a polymer complex of two or more kinds of polymers. The reason why the water vapor permeability of the moisture permeation control layer is adjusted within the above range cannot be unambiguously described because various factors are intertwined. However, the moisture permeation control layer is mainly composed of a thermoplastic resin. Due to the chemical properties, physical properties, and thermal properties of the multiple components that comprise, for example, partially having a crystalline structure and an amorphous structure, soft units (soft segments) and hard units (hard segments) This is presumably due to non-uniform construction. Therefore, as illustrated, it is preferable to use a thermoplastic resin capable of easily constructing the soft unit and the hard unit when forming the moisture permeation control layer.

A method for controlling the water vapor permeability (water vapor transmission amount, temperature dependency of water vapor transmission amount, reference temperature T _S ) of the moisture permeation control layer is not particularly limited, and any method can be adopted. For example, glass transition temperature, melting point, crystallinity, molecular weight, molecular chain length, three-dimensional structure, molecular gap, polarity, hydrophilicity, etc. of each component constituting the thermoplastic resin, blending ratio of multiple components, melting during molding Alternatively, the water vapor permeability of the moisture permeation control layer can be controlled by appropriately adjusting the cooling conditions (temperature, time, process management, etc.), the thickness of the film or sheet during molding, the thickness of the molded body, and the like.

For example, in the case where T _S is determined using the difference in glass transition temperature, it is presumed that the control of the water vapor transmission amount can be explained as follows. That is, normally, the soft unit has a glass transition point lower than that of the hard unit, and above the glass transition temperature, the micro-Brownian motion of the molecule is activated, the molecular gap is increased, and the water vapor transmission rate is remarkably increased. On the other hand, at the same temperature, there is almost no change in the physical characteristics of the hard unit, and the rigidity and shape can be maintained. Therefore, the moisture permeation control layer in which these are present non-uniformly maintains the shape and rigidity required as a food packaging material in the high temperature environment above the glass transition temperature of the soft unit by the characteristics of the hard unit, and at the same time, A significant increase in the amount of transmission can be caused by the properties of the soft unit. In general, the higher the blending ratio of the hard unit, the higher the glass transition temperature as a whole, and the higher the molecular weight of the components constituting the hard unit and the soft unit, the lower the glass transition temperature. As the three-dimensional rigidity increases, the glass transition point becomes higher. As the hydrophilicity of each component increases, the amount of water vapor transmission increases, and as the activity of the soft brown of the soft unit increases, the amount of increase in the amount of water vapor transmission tends to increase. Therefore, it is possible to precisely control the water vapor permeability of the moisture permeation control layer by adjusting the combination and blending ratio of each component constituting the thermoplastic resin.

Although it does not specifically limit as a specific example of the copolymer which consists of 2 or more types of monomers, For example, the styrene-butadiene copolymer which is a styrene-type alloy is mentioned. In this case, for example, polystyrene is used as a hard unit that melts at a high temperature of about 120 ° C. and hardly changes in shape and rigidity at a temperature lower than that. By adopting the crystalline polybutadiene whose permeability is remarkably increased as a soft unit, it is possible to realize the moisture permeation control layer of the present embodiment in which a change in the amount of water vapor permeation due to temperature exhibits a specific behavior. In such a styrene-butadiene copolymer, for example, by changing the blending ratio of polystyrene and crystalline polybutadiene, the fluctuation amount of the water vapor transmission amount W _VTR around the reference temperature T _S can be arbitrarily adjusted.

Specific examples of the polymer composed of one or more prepolymers and one or more monomers are not particularly limited. For example, a polyisocyanate represented by the general formula OCNR ₁ NCO and a diol represented by HOR ₂ OH are co-polymerized. Urethane polymer OCN [(R ₁ NHCOOR ₂ OCONH) _m (R ₁ NHCOOR ₃ OCONH) _n ] _l R obtained by reacting a urethane prepolymer obtained by polymerization with a chain extender represented by HOR ₃ OH ₁ NCO [wherein m, n and l represent a positive integer, particularly preferably 1 to 16]. Such a polyurethane-based polymer does not become a completely uniform state at the molecular level, and is composed of a soft segment composed of a non-crystalline diol unit and a hard segment composed of a chain extender and a polyisocyanate. It is conceivable that the glass transition temperature and the water vapor transmission characteristics may vary depending on the rigidity of R ₁ , R ₂ , R ₃ , molecular weight, steric structure, polarity, hydrophilicity, etc., as well as the number of m and n. That is, the glass transition temperature becomes lower as the molecular weight of R _2, R ₃ is increased, in R _1, R _2, a glass transition temperature higher rigidity of the R ₃ increases increases tendency. In addition, the higher the hydrophilicity of R ₁ , R ₂ , and R ₃ , the greater the amount of water vapor transmission, and the higher the activity of micro Brownian motion, such as the longer molecular chain length of R ₃ , the water vapor transmission amount at the glass transition temperature. The range of increase tends to increase. Therefore, in such a polyurethane polymer, by combining these in consideration, the fluctuation amount of the water vapor transmission amount W _VTR around the reference temperature T _S and the reference temperature T _S can be precisely adjusted. It is possible to realize the moisture permeation control layer of this embodiment in which the change in the amount of water vapor permeation due to temperature exhibits a specific behavior.

  Although it does not specifically limit as a specific example of polyisocyanate, For example, what has two or more isocyanate groups at the terminal, More specifically, 2, 4- toluene diisocyanate, 4,4'- diphenylmethane diisocyanate, carbodiimide modification | denaturation 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, prepolymer type polyisocyanate, and the like. These can be used individually by 1 type or in mixture of 2 or more types.

  Although it does not specifically limit as a specific example of diol, For example, what has two or more hydroxyl groups in a molecule | numerator, More specifically, polypropylene glycol, 1, 4- butane glycol adipate, polytetramethylene glycol, bisphenol A + Examples include polyether polyols such as propylene oxide, polyester polyols, and polyether polyester polyols obtained by polymerizing these. These can be used individually by 1 type or in mixture of 2 or more types.

  Specific examples of the chain extender are not particularly limited. For example, ethylene glycol, diethylene glycol, propylene glycol, 1,4-butane glycol, bis (2-hydroxyethyl) hydroquinone, bisphenol A + ethylene oxide, bisphenol A + propylene oxide, and the like. Is mentioned. These can be used individually by 1 type or in mixture of 2 or more types.

  Specific examples of the polymer blend of two or more polymers and the polymer complex of two or more polymers are not particularly limited. For example, styrene-based, olefin-based, ester-based, amide-based, carbonate-based polymer blends, polymer alloys More specifically, for example, polyamide / polypropylene, polyamide / elastomer, polycarbonate / polystyrene, polycarbonate / polypropylene, polycarbonate / polybutylene terephthalate, polycarbonate / polyethylene terephthalate, modified polyphenylene ether, ABS / polyolefin and These combinations and the like can be mentioned. These can be used individually by 1 type or in mixture of 2 or more types.

  In addition to the above, examples of the material having a crystalline / non-crystalline part include a polyvinyl chloride part having a crystalline polyvinyl chloride part and an amorphous polyvinyl chloride part. In this case, the crystalline polyvinyl chloride part functions as a hard unit, and the amorphous polyvinyl chloride part functions as a soft unit. Conceivable. Examples of a material that exhibits the same effect include viscose, transisoprene, polynorbornene, and polybutadiene rubber.

  The resin composition containing a thermoplastic resin may contain other components as necessary. Other components are not particularly limited and are known additives such as surfactants, antioxidants, heat stabilizers, flame retardants, internal mold release agents, antiblocking agents, antistatic agents, plasticizers, lubricants. , Ultraviolet absorbers, infrared absorbers, pigments, various solvents and the like.

  In molding a moisture permeation control layer from a resin composition containing a thermoplastic resin, a known thermoplastic resin film forming / molding method or the like can be used. Specific examples include a solution cast molding method, a T-die method, a cutting method, an inflation method, an injection molding method, a blow molding method, a pressure forming method, a vacuum molding method, a foam molding method, and the like. It is not limited.

  The thickness of the moisture permeation control layer is not particularly limited, and is appropriately set according to the required water vapor permeability. In general, as the thickness of the moisture permeation control layer increases, the water vapor permeability tends to decrease. On the other hand, as the moisture permeation control layer decreases, the water vapor permeability tends to increase. ) And shape followability tend to be improved.

  Even if the food packaging material has the above-described configuration of the moisture permeation control layer alone, it has a configuration in which other functional layers are partially or entirely installed on one or both sides of the moisture permeation control layer formed into a film or sheet. Even if it is, the structure by which another functional layer is contained in a moisture-permeable control layer, or the structure by which the moisture-permeable control layer was integrated with the other functional layer may be sufficient.

  Specific examples of the functional layer are not particularly limited. For example, in addition to silicone resins, fluororesins, superabsorbent resins, elastomers such as natural rubber and synthetic rubber, natural fibers, synthetic fibers or semi-synthetic fibers are used. Nonwoven fabric, woven fabric, paper, etc. By adopting a laminated structure with such a functional layer, it is possible to impart or improve functions such as adhesiveness, slipperiness, water absorption, oil absorption, releasability, adhesion, etc. The utility value is enhanced as a highly functional food packaging material.

The functional layer preferably has a water vapor transmission amount W _VTR (g / (m ² · h)) that is always larger than that of the moisture permeation control layer over the entire temperature range of 0 to 100 ° C. Water vapor permeability of W _VTR of the functional layer ^{(g / (m 2 · h} )) water vapor permeability of the entire food packaging If is less than the moisture-permeable control layer ^{_{W VTR (g / (m 2}} · h)) is functional layer Therefore, the moisture permeation control effect of the moisture permeation control layer may not be fully exhibited. Moreover, it is preferable that a functional layer is a thing with poor hygroscopicity. If the hygroscopicity of the functional layer is high, it is difficult to adjust the moisture permeability at the time of use, and thus the moisture permeability control effect of the moisture permeability control layer may not be sufficiently exhibited.

  It is desirable that the food packaging material does not contain a fabric. When the food packaging material includes a fabric, the fabric is opaque, so that it is difficult to visually recognize the food in the package from the outside. Therefore, it is necessary to unpack the food in order to confirm the food in the package. In addition, when the food packaging material including the fabric is in the form of a film or sheet, the thickness and rigidity of the fabric impairs flexibility and shape following at the time of molding or handling of the film or sheet, Productivity, handleability and versatility tend to decrease. On the other hand, when the food packaging material containing the fabric is a container-shaped molded body, the flexibility of the fabric makes it difficult to maintain the shape when the molded body is molded or when it is handled after molding. Tend to decrease the stability and dimensional stability. Furthermore, since the fabric has irregularities on the surface and is poor in smoothness and inferior in peelability, there may be inconveniences such as food in the package entering the voids on the surface of the fabric during packaging or storage. Moreover, since the fiber which comprises a cloth may drop | omit and mix in a foodstuff, the use as a food packaging material may be restrict | limited.

  The method of forming the functional layer is not particularly limited. For example, a method of laminating or integrating a functional layer separately formed into a sheet shape with an adhesive or heat and laminating or integrating the moisture permeability control layer formed into a film shape or a sheet shape , A method of laminating or integrating a molten functional layer directly onto a moisture permeation control layer formed into a film or sheet and forming a film, or applying or spraying a functional layer separately dissolved in a solution to the moisture permeation control layer Examples thereof include a method of drying and then laminating or integrating, and a method of laminating or integrating the functional layer on the moisture permeation control layer by coextrusion or vapor deposition.

  As described above in detail, the food packaging material of the present embodiment preserves not only foods with low water content such as bread but also foods containing a large amount of water and liquid components over a long period of time. For example, it can be suitably used as a packaging material for packaging food containing rice or grains that have been cooked, steamed or fermented. For example, rice balls are usually molded at a high temperature of about 60 to 90 ° C., and after being radiated for a certain period of time in order to maintain the flavor, the rice balls are often stored and transported as they are. Since the food packaging material of the embodiment has both functions of a moisture release effect at a relatively high temperature and a drying suppression effect at a relatively low temperature, the process of radiating heat can be omitted by using this. Can be packaged. Therefore, by using the food packaging material of the present embodiment, the process tolerance is dramatically increased, and as a result, productivity and economy are improved.

  The food packaging material and rice ball packaging material of the present invention have both functions of a moisture release effect at a relatively high temperature and a drying suppression effect at a relatively low temperature, and a food with a low water content such as bread. Not only food containing a large amount of water and liquid components can be stored in high quality for a long period of time, or it can be cooked as it is in the package, so that food can be stored, moved, processed, protected and heated. As a material used for cooling, it can be used widely and effectively.

Claims (4)

A temperature (° C.)-Water vapor transmission rate W _VTR (g / (m ² ) obtained by molding a resin composition containing a thermoplastic resin and measured under a humidity condition of 60% RH in accordance with JIS L1099 A-2 method. In the plot chart of h)), the increase in water vapor transmission rate W _VTR from the reference temperature T _S (° C.) to T _S +10 (° C.) is from T _S −10 ° C. (° C.) to the reference temperature T _S (° C.). It has a transition region that is 2 to 100 times the increase in the water vapor transmission rate W _VTR , and the water vapor transmission rate W _VTR (g / (m ² · h)) at a temperature lower than the transition region is greater than 0 and 50 And having at least one moisture permeation control layer, wherein the reference temperature T _S (° C.) is in the range of 0 ° C. or more and 100 ° C. or less.
Food packaging material. The thermoplastic resin is a copolymer composed of two or more monomers, a polymer composed of one or more prepolymers and one or more monomers, a polymer blend of two or more polymers, and / or two or more types of polymers. A polymer complex of the polymer,
The food packaging material according to claim 1. On at least one surface of the moisture permeation control layer, a moisture permeation layer having a water vapor transmission amount W _VTR within a range of 0 ° C. or more and 100 ° C. or less is always larger than that of the moisture permeation control layer.
The food packaging material according to claim 1 or 2. Including the food packaging material according to any one of claims 1 to 3,
Packaging for rice balls.

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