Additive for imparting freshness preservation function, method for manufacturing the additive for imparting freshness preservation function, and packaging bag

Abstract

We have developed a technology to provide a simple and useful additive that can effectively impart freshness preservation properties to the raw materials for manufacturing packaging bags made of plastic film without compromising the strength of the film, thereby providing a superior packaging bag that can maintain freshness for a longer period than conventional packaging bags that have been given freshness preservation properties using conventional technology. [Solution] An additive used in the manufacture of a plastic film having a freshness-preserving function, comprising powdered rice husks, a powdered metal complex, and vegetable oil, for imparting a freshness-preserving function; a method for manufacturing an additive for imparting a freshness-preserving function; and a packaging bag having the additive.

Description

Technical Field

[0001] The present invention relates to an additive for imparting a freshness retention function to a plastic film, a method for producing an additive for imparting a freshness retention function, and a packaging bag having the additive. Specifically, in a plastic film packaging bag used for storing fresh foods such as lettuce, cabbage, bananas and other vegetables and fruits, it is possible to keep the fresh foods stored in the bag in a fresh state for a longer period of time. The present invention relates to a technology for providing an additive for imparting an excellent freshness retention function to a plastic film, and further to a technology for providing a packaging bag having an excellent freshness retention function that contains the additive and is not available in the prior art.

Background Art

[0002] In recent years, various technologies have been proposed for products called "freshness retention bags" as listed below, and a wide variety of products are commercially available and widely used. For example, in Patent Document 1, a freshness retention material for fresh foods such as a configuration in which a porous inorganic silicate compound such as Oya stone or Hokke stone is coated on a gas-permeable body which is a synthetic resin having a three-dimensional network skeleton structure is proposed. In this proposal, the freshness retention material is obtained by coating or impregnating a slurry composed of a porous inorganic silicate compound and water on the surface of the gas-permeable body and drying it. Patent Document 2 describes that the above-mentioned porous powder adsorbs and removes ethylene gas generated in trace amounts during storage of vegetables, fruits, etc., or adsorbs and removes malodorous gases such as ammonia. And in Patent Document 2, a freshness retention resin composition in which 2 to 300 parts by weight of crushed Natsume stone powder is blended with 100 parts by weight of synthetic resin is proposed. By adding crushed Natsume stone powder, in addition to adsorbing ethylene gas and malodorous substances such as ammonia, the freshness of agricultural products or cut flowers is maintained over a long period by far infrared rays irradiated from the crushed Natsume stone powder. A freshness retention film / sheet formed using this is proposed.

[0003] Patent Document 3 proposes a multilayer packaging material comprising a thermoplastic resin layer containing a thermoplastic resin and a porous powder. Patent Document 4 proposes a fresh produce freshness-preserving packaging container made of a synthetic resin film having through-holes perforated by laser processing. Furthermore, many proposals have been made to appropriately adjust the oxygen and carbon dioxide permeability of the plastic film to enhance freshness preservation (see, for example, Patent Document 5). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-136956 [Patent Document 2] Japanese Patent Application Publication No. 9-202361 [Patent Document 3] Japanese Patent Application Publication No. 63-151451 [Patent Document 4] Patent No. 7326721 [Patent Document 5] Patent No. 7283473 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, according to the inventors' research, the packaging bag products that provide freshness preservation using the conventional technologies described above, while exhibiting freshness preservation, are not entirely sufficient. The inventors recognized that in order to effectively utilize resources such as agricultural products, there is a need for packaging bags with enhanced freshness preservation capabilities, particularly for vegetables, fruits, and cut flowers, that can maintain their freshness for a longer period. They also recognized that if this could be achieved with simple technology, the effect would be extremely significant.

[0006] Therefore, the ultimate objective of the present invention is to provide a superior packaging bag that has a longer freshness retention period than conventional packaging bag products that have been given freshness retention properties by prior art. A specific objective of the present invention is to find a technology that provides a useful additive that can effectively impart freshness retention properties to the raw materials for manufacturing packaging bags made of plastic film without impairing the strength of the film. Specifically, an objective of the present invention is to develop a technology that, by adding only a small amount to the raw materials for resin compositions for forming plastic films, enables packaging bags made of plastic film formed from said raw materials to retain the freshness of agricultural products and other foods for a longer period of time. An objective of the present invention is to develop a technology that provides a useful and novel additive that can effectively utilize rice husks, a natural resource that has been difficult to finely grind and uniformly incorporate into plastic films. [Means for solving the problem]

[0007] The above objective is achieved by the present invention as described below. That is, the present invention provides an additive for imparting the following freshness-preserving function. [1] An additive used in the manufacture of a plastic film having freshness-preserving properties, characterized by comprising powdered rice husks, a powdered metal complex, and vegetable oil, for imparting freshness-preserving properties.

[0008] The following are examples of preferred additives mentioned above. [2] The additive for imparting freshness preservation function according to [1] above, wherein the metal complex is selected from at least one of the group consisting of metal phthalocyanines, metal porphyrin complexes, and metal carbonyl complexes. [3] Additives for imparting freshness preservation function as described in [1] or [2] above, which are formed as a masterbatch. [4] An additive for imparting freshness preservation function according to any one of [1] to [3] above, wherein the melting point of the vegetable oil is 70°C or higher and 85°C or lower.

[0009] As another embodiment, the present invention provides a method for manufacturing an additive for imparting freshness-preserving function to the following plastic film. [5] A method for manufacturing an additive for imparting freshness preservation function to a plastic film, comprising the steps of: preparing a liquid A containing powdered rice husks and vegetable oil, and a liquid B containing a powdered metal complex and vegetable oil; sending the prepared liquid A and liquid B into a supercritical apparatus and performing carbon dioxide supercritical polymerization in the supercritical apparatus to prepare a stock solution of the additive; and preparing a masterbatch by incorporating the stock solution of the additive prepared in the first step in an amount of 0.2 to 0.5 parts by mass per 100 parts by mass of resin.

[0010] The following are examples of preferred methods for manufacturing additives to impart freshness-preserving properties to the plastic film mentioned above. [6] A method for producing an additive for imparting freshness preservation function as described in [5] above, wherein the melting point of the vegetable oil is 70°C or higher and 85°C or lower. [7] A method for producing an additive for imparting freshness preservation function according to [5] or [6] above, wherein the resin constituting the resin material is selected from at least one of the group consisting of polyolefin resins and ABS resins. [8] A method for producing an additive for imparting freshness preservation function according to [7] above, wherein the polyolefin resin is either a high-density polyethylene resin or polypropylene. [9] A method for producing an additive for imparting freshness preservation function according to any one of [5] to [8] above, wherein the metal complex is selected from at least one of the group consisting of metal phthalocyanines, metal porphyrin complexes and metal carbonyl complexes.

[0011] As another embodiment of the present invention, the following packaging bag is provided.

[10] A packaging bag characterized by being made of a bag-shaped plastic film formed by inflation molding using a resin composition obtained by mixing 100 parts by mass of a polyolefin resin with an additive for imparting freshness preservation function as described in [3] above, which is formed as a masterbatch, in an amount of 9 parts by mass or more and 12 parts by mass or less.

[0012] Preferred packaging bags include the following:

[11] The packaging bag according to

[10] above, wherein the thickness of the plastic film is 8 μm or more and 50 μm or less. [Effects of the Invention]

[0013] According to the present invention, it becomes possible to provide a packaging bag that has a longer freshness retention period than packaging bag products that have been given freshness retention properties by conventional technology, and is of extremely practical value. According to the present invention, it becomes possible to provide a useful additive that exhibits a high level of performance that has not been achieved by conventional technology, by simply adding a small amount to the raw materials such as resin when manufacturing packaging bags made of plastic film, without compromising the strength of the packaging bag made of plastic film formed from these raw materials, and allowing agricultural products and other items stored in the bag to maintain their freshness for a longer period of time. According to the present invention, as a result of realizing the development of a new, effective and useful additive, it becomes possible to effectively utilize rice husks, a natural resource that was difficult to uniformly disperse in plastic film, and by adding it to the plastic film, it becomes possible to provide a new packaging bag product that can maintain the freshness of vegetables and other items stored in the bag for a longer period of time compared to conventional packaging bag products. According to the present invention, by simply adding a small amount of the new, effective, and useful additive of the present invention to the resin composition raw materials for forming a plastic film, it becomes possible to provide a plastic film packaging bag that can maintain the freshness of agricultural products and other items stored inside the bag for a longer period of time without compromising the strength required for the packaging bag. [Brief explanation of the drawing]

[0014] [Figure 1A] This is a diagram showing an outline of the manufacturing process when forming the additive of the present invention into a masterbatch. [Figure 1B] This is a diagram showing an outline of the manufacturing process when producing a packaging bag using the additive of the present invention formed into a masterbatch. [Figure 2A] This is a graph showing the results of a performance test on freshness retention over a long period, which was confirmed by the change in the area occupied by the green hue obtained by color separation of the photographic image of the cabbage, which was respectively stored in the packaging bag FR of the example of the present invention and the two commercially available packaging bags A and B for freshness retention used for comparison. [Figure 2B] This is a graph showing the results of a performance test on freshness retention over a long period, which was confirmed by the change in the area occupied by the brown hue obtained by color separation of the photographic image of the cabbage, which was respectively stored in the packaging bag FR of the example of the present invention and the two commercially available packaging bags A and B for freshness retention used for comparison. [Figure 2C] This is a graph showing the results of a performance test on freshness retention over a long period, which was confirmed by the change in the area occupied by the yellow hue obtained by color separation of the photographic image of the cabbage, which was respectively stored in the packaging bag FR of the example of the present invention and the two commercially available packaging bags A and B for freshness retention used for comparison.

Mode for Carrying Out the Invention

[0015] Hereinafter, the present invention will be described with reference to preferred embodiments, but the present invention is not limited to the following embodiments. The inventors of the present invention have earnestly studied to obtain a packaging bag that can maintain freshness for a longer period than conventional products by a simple means of adding an additive made into a masterbatch to a resin material that has been conventionally widely used as a forming material for packaging bags made of plastic film. As a result, the present invention has been achieved. <00​The inventors first focused on rice husks, a natural resource whose usefulness is recognized but which is discarded in large quantities, as a material to be incorporated into plastic films, and investigated its potential use as an additive material to effectively impart freshness preservation functionality.

[0017] Rice hulls are composed mostly of recalcitrant organic substances such as cellulose and hemicellulose, and contain about 20% amorphous silica. The inventors anticipated that powdered rice hulls could be a promising material for imparting freshness-preserving functions to plastic films, and investigated the components from the perspective of imparting freshness-preserving functions. In addition to the organic substances mentioned above, rice hulls also contain lignin. During the investigation, the inventors discovered that lignin has freshness-preserving functions. Specifically, when the freshness-preserving effect was confirmed using only lignin on lettuce, it was found that the lettuce remained green for a longer period. From these results, the inventors recognized that using "rice hull powder" as a forming component of plastic films for making packaging bags may provide long-term freshness-preserving functions to plastic film packaging bags. Furthermore, they considered that using a plastic film made by adding a small amount of lignin powder to rice hull powder might allow for more stable imparting of freshness-preserving functions to plastic film packaging bags. Furthermore, in a study using lignin alone, the lettuce remained green for a longer period, but it ended up looking as if it had been steamed. From this, it was found that using lignin in its raw form on vegetables may diminish the value of the vegetables themselves and therefore cannot be used.

[0018] When powdered rice husks are used as a component of the plastic film, the cellulose and silica components that make up the rice husks, along with the lignin mentioned above, are thought to impart the following functions to the packaging bag. The inventors conducted a confirmation test on this point. As a result, when the plastic film is made into a packaging bag, the cellulose and silica components that make up the rice husks are thought to contribute to moisture regulation inside the bag and / or gas adsorption and moisture retention from vegetables inside the bag. In this respect as well, the use of "rice husks" is desirable.

[0019] On the other hand, even if a freshness-preserving function can be imparted to plastic film by incorporating rice husk powder, in order to impart this function to packaging bags more effectively and stably without compromising the strength of the bag, it is necessary to ensure that the rice husk powder is uniformly distributed throughout the film. However, according to the inventors' research, even if pellets containing a high concentration of finely ground rice husk powder are produced and the resulting pellets are used as a masterbatch and incorporated into the resin for forming packaging bags, there is a technical challenge in that it is difficult to uniformly incorporate the rice husk powder into the formed plastic film.

[0020] The inventors of this invention have diligently studied how to resolve the aforementioned technical problems and realize a plastic film with higher freshness retention than conventional films, and have made the following new discoveries, leading to the present invention. First, in order to impart a high freshness retention function to a plastic film, the inventors have found that it is effective to use a resin composition containing rice husk powder in combination with a powdered metal complex and vegetable oil as additives, and to prepare a plastic film using this additive and make a packaging bag from the film. Furthermore, in order to uniformly and stably impart sufficient freshness retention function to the plastic film, it is preferable to use a masterbatch with a high concentration of active ingredients as the composition of the additive. In addition, the inventors have found that by applying a new method using a supercritical fluid apparatus when preparing the masterbatch, it is possible to include the active ingredients for imparting freshness retention function to the masterbatch at a sufficient concentration, and moreover, when the obtained masterbatch is included in a general-purpose resin, it is possible to uniformly include fine powdered rice husks in the resin, thus obtaining a useful raw material for the additive. Specifically, it was found that by using a supercritical fluid apparatus to prepare the stock solution of the above-mentioned additive, and by supercritical polymerization of the raw material components sent into the apparatus using carbon dioxide, it becomes possible to stably and uniformly incorporate the active ingredient, powdered rice husks, into a plastic film.

[0021] More specifically, the inventors have discovered that the excellent effects of the present invention can be achieved by preparing a masterbatch to be used as an additive in the following manner and using it to manufacture packaging bags. First, as shown in Figure 1A, prepare liquid A containing powdered rice husks and vegetable oil, and liquid B containing powdered metal complex and vegetable oil. Then, send the prepared liquids A and B into a supercritical fluid apparatus, and supercritical polymerization of carbon dioxide is carried out in the supercritical fluid apparatus to obtain a liquid substance containing powdered rice husks and powdered metal complex. This substance is used as the stock solution for the additive, and this stock solution is incorporated into the resin at a sufficient concentration and pelletized to form the additive as a masterbatch. Then, add (blend) the obtained masterbatch to a general-purpose resin material used in the manufacture of packaging bags, and use the resulting resin composition as a raw material composition for manufacturing plastic films by methods such as inflation molding, and use this composition to prepare packaging bags (see Figure 1B). The inventors have found that the above-described simple manufacturing method efficiently produces plastic films and packaging bags that exhibit an unprecedentedly high level of freshness preservation function, which is the objective of the present invention.

[0022] The additive for imparting freshness preservation function of the present invention is an additive used in the manufacture of a plastic film having freshness preservation function, and is characterized by comprising powdered rice husks, a powdered metal complex, and a vegetable oil. The raw materials constituting the additive of the present invention will now be described. For the powdered rice husks constituting the present invention, it is preferable to use powder or fine powder obtained by directly processing rice husks of the grain rice into powder. Depending on the thickness of the plastic film used for the packaging bag to be prepared, the rice husks contained in the plastic film formed using the additive of the present invention are preferably, for example, powdered rice husks with a number average particle size of about 3 μm to 50 μm, and more preferably powdered rice husks with a number average particle size of about 3 μm to 30 μm. If the particle size of the rice husks contained in the plastic film exceeds 50 μm, it may give a foreign body sensation or cause the film to tear easily, so this is undesirable. The particle size mentioned above is the number average particle size and is the 50% diameter called the median diameter.

[0023] The additive for imparting freshness preservation function of the present invention comprises the above-mentioned powdered rice husks, a powdered metal complex, and vegetable oil. The metal complex constituting the additive of the present invention is preferably at least one selected from the group consisting of metal phthalocyanines, metal porphyrin complexes, and metal carbonyl complexes. Phthalocyanines are known to form complexes with a wide variety of metal elements. Examples of metals include copper, iron, zinc, cobalt, nickel, manganese, and aluminum. According to the inventors' studies, among these, metal phthalocyanine complexes are particularly preferred.

[0024] Metallic porphyrin complexes are a general term for colored metal complexes that use porphyrins and their derivatives as ligands. Porphyrins are also known to form complexes with a wide variety of metal elements. Examples of metals include iron, manganese, and cobalt. Metallic carbonyl complexes are a general term for coordination compounds formed when carbon monoxide coordinates to a fibrous metal. Examples of metals include iron, cobalt, and molybdenum.

[0025] For the additive material used to provide the freshness-preserving function of the present invention, it is preferable to use a vegetable oil having the following characteristics. In the carbon dioxide supercritical polymerization using the supercritical apparatus that characterizes the present invention, which is carried out when producing the raw material of the additive, the temperature is raised to a pressure of 9 MPa / 90°C. After polymerization is complete, it is necessary to slowly lower the temperature and release the carbon dioxide gas. For this reason, the vegetable oil that constitutes the additive material of the present invention is suitable to be an oil that quickly forms a film when the temperature is lowered. Specifically, it is preferable to use a vegetable oil that has a melting temperature (melting point) and the characteristic of forming a uniform film.

[0026] In addition to the above, since the additive for imparting freshness preservation function in the present invention is an additive for plastic films used in freshness preservation bags for food, it is desirable to use materials derived from natural products as much as possible for the raw materials. For this reason, the present invention uses vegetable oil. Examples of vegetable oils derived from natural products include olive oil, corn oil, sesame oil, rice oil, soybean oil, rapeseed oil, coconut oil, palm oil, sunflower oil, safflower oil, and cottonseed oil. In the present invention, among these, since the carbon dioxide supercritical polymerization described above is carried out at a temperature of about 90°C, it is preferable to use vegetable oils that become solid at room temperature with a melting point of about 70°C to 85°C. Examples of such oils include carnauba wax, rice wax, sunflower wax, rosin ester, and candelilla wax. Among these, it is preferable to use rice wax or a mixture of rice wax and other hydrogenated vegetable oils. Examples of hydrogenated vegetable oils include hydrogenated palm oil and hydrogenated rapeseed oil.

[0027] Rice wax, which can be suitably used as a vegetable oil constituting the additive of the present invention, is a natural plant-based wax unique to Japan. It is obtained by further de-oiling and refining the crude wax obtained in the process of refining rice bran oil extracted from rice bran. Rice wax is used, for example, as a mold release agent and lubricant. Rice wax has a high proportion of wax esters and high crystallinity. It also has a melting point of about 80°C and is suitable for the present invention because it melts and solidifies sharply when heated. In the present invention, it is preferable to use an oil with a melting point of 70°C to 85°C, preferably 73°C to 80°C, as the vegetable oil.

[0028] When preparing the additives for imparting the freshness-preserving function of the present invention, in addition to the materials described above, solvents, colorants, etc., may be used as appropriate. As for the solvent, it is desirable to use one that is low polar, has a low boiling point, and is capable of dissolving the vegetable oil that constitutes the present invention. Examples of such solvents include dichloromethane and bromopropane. As for the colorant, those used in conventional packaging bags may be used as appropriate.

[0029] The additive for imparting freshness preservation function of the present invention, as described above, can be stably prepared as a stock solution by the following method. Furthermore, by using the obtained stock solution of the additive, it becomes possible to easily and stably produce a masterbatch suitable for manufacturing the packaging bags of the present invention. As a result, it becomes possible to mass-produce the packaging bags of the present invention, which exhibit a longer-lasting freshness preservation function than conventional bags, using the same manufacturing method as conventional methods. This means that it becomes possible to economically provide the packaging bags of the present invention with superior freshness preservation function.

[0030] The present invention provides a method for producing an additive for imparting freshness preservation function, comprising the steps of: preparing a liquid A containing powdered rice husks and vegetable oil, and a liquid B containing powdered metal complex and vegetable oil; sending the prepared liquids A and B into a supercritical apparatus and performing carbon dioxide supercritical polymerization in the supercritical apparatus to prepare a stock solution of the additive; and preparing a masterbatch by incorporating the stock solution of the additive prepared in the first step in an amount of 0.2 to 0.5 parts by mass per 100 parts by mass of resin.

[0031] As mentioned earlier, in the process of preparing the raw material for the additive by sending liquid A and liquid B into a supercritical fluid apparatus and performing carbon dioxide supercritical polymerization, it is necessary to create a high-pressure, high-temperature environment in the supercritical fluid apparatus at 9 MPa / 90°C, and then slowly lower it to room temperature. Furthermore, the inventors have found that in order to obtain an additive with good properties for imparting freshness preservation, it is desirable that the vegetable oil used in liquids A and B rapidly forms a film on the polymer as the temperature is lowered. After investigating oils with the above properties, the inventors found that, given the requirements of being easily soluble during polymerization at 90°C, rapidly forming a film when the temperature is lowered after polymerization, and being a vegetable oil suitable for the purpose of the present invention, a vegetable oil with a melting point of about 70°C to 85°C, such as rice wax, is preferable and suitable for the manufacturing method of the present invention.

[0032] According to the inventors' studies, for example, using iron phthalocyanine as a representative example of metallic phthalocyanine and rice wax as a representative example of vegetable oil, a stock solution of additive containing rice husks and / or iron phthalocyanine can be easily obtained by sending liquid A, which contains powdered rice husks and rice wax and optionally a solvent, and liquid B, which contains powdered iron phthalocyanine and rice wax and optionally a solvent, into a supercritical fluid apparatus, reacting them in the supercritical fluid apparatus, and then cooling them. The inventors believe that this is one of the factors that realizes the excellent effects of the present invention. According to the inventors' studies, the stock solution obtained by reacting liquid A and liquid B in a supercritical fluid apparatus has the following characteristics. For example, the stock solution of additive obtained using liquid B contains nanocapsules with a median size of about 22 nm that contain iron phthalocyanine. Although iron phthalocyanine is used as a representative example in the specification of the present invention, the effects of the present invention can be obtained with any metal complex similar to iron phthalocyanine.

[0033] In the method for producing the additive of the present invention, powdered rice husks used in combination with the powdered metal complex described above are also reacted with a vegetable oil such as rice wax in a supercritical fluid apparatus to prepare the raw material for the additive. Similar to the case where a metal complex such as phthalocyanine iron is used as a constituent material, it can be inferred that the raw material contains nanocapsules ranging from tens of nanometers to over a hundred nanometers in size, containing powdered rice husks. In this case, it is estimated that several tens of percent of the total rice husks are encapsulated. The inventors believe that the effect of achieving the high level of freshness preservation described above, which was realized by using a packaging bag using the additive of the present invention, is as follows: Supercritical water is known to dissolve organic matter better than ordinary water, and when powdered rice husks are reacted in a supercritical fluid apparatus using the method described above, it is thought that the rice husks in the raw material for the additive, other than the silica that constitutes the rice husks, such as lignin, which are difficult to decompose, dissolve easily, so that the rice husks in the raw material for the additive become nanocapsules with a composition containing more fine silica. The inventors have confirmed that by using a stock solution obtained by reacting powdered rice husks in a supercritical fluid apparatus as an additive when manufacturing plastic films, the powdered rice husks dispersed in the plastic film become significantly finer compared to the powdered rice husks used as the raw material. According to the inventors' investigation, in the manufacturing method of the present invention, the powdered rice husks used as the raw material can be micronized by reacting them in a supercritical fluid apparatus when preparing the stock solution of the additive of the present invention. Therefore, relatively large rice husks with an average number of particles expressed by median diameter of about 30 μm to 90 μm can be used as the raw material. On the other hand, rice husks are hard and difficult to pulverize by mechanical grinding methods, and are also difficult to handle. Therefore, being able to use relatively large rice husks as a raw material is a significant industrial advantage.

[0034] Furthermore, as described above, in the manufacturing method of the present invention, the rice husks in the raw solution of the additive produced are nanocapsules with a composition containing many fine-sized silica particles. This improves compatibility with resins such as polyolefin resins that form the base of the packaging bag, allowing the powdered rice husks to be uniformly incorporated into the resin. This is also considered to be one of the reasons why a previously unseen high level of freshness preservation has been achieved in the packaging bag using the additive of the present invention.

[0035] According to the inventors' research, the additive of the present invention, formed as a masterbatch using the stock solution with the above-described configuration, can be added to a conventional resin material for the manufacture of plastic films to uniformly incorporate rice husks of a finer size than those used as raw materials into the resulting plastic film. This is considered to be a major factor in achieving excellent freshness preservation in plastic film packaging bags formed using the additive of the present invention.

[0036] According to the inventors' investigation, as described later, even when preparing a stock solution of the additive using only liquid A containing rice husk powder in the same manner, and manufacturing a packaging bag using the obtained additive, it was not possible to obtain the high level of freshness preservation function achieved by using the packaging bag of the present invention which also contains a powdered metal complex. From this fact, the inventors believe that the presence of powdered rice husks uniformly and finely dispersed in the plastic film forming the packaging bag, along with the metal complex such as phthalocyanine iron, and the environment in a cool, dark place (vegetable compartment of a refrigerator) where vegetables are stored, may be causing some kind of synergistic effect that leads to ethylene gas adsorption and inactivation of the vegetables being preserved, thereby suppressing the rate of ripening.

[0037] In the method for producing the additive of the present invention, the resin material used when preparing the masterbatch using the raw material of the additive prepared as described above is not particularly limited. Considering subsequent applications such as packaging bags, it is preferable that the resin material be at least one selected from the group consisting of polyolefin resins and ABS resins.

[0038] According to the inventors' studies, when the masterbatch configured as described above is applied as an additive to the packaging bag of the present invention, a packaging bag with high freshness preservation capabilities can be easily prepared by configuring it as follows. Specifically, for example, a resin composition can be prepared by mixing 100 parts by mass of polyolefin resin with 9 to 12 parts by mass of the additive masterbatch, and by performing inflation molding using this resin composition, a bag-shaped plastic film of the present invention with excellent freshness preservation properties can be easily obtained. Considering the packaging bag, it is preferable to prepare the plastic film with a thickness of 8 μm to 50 μm. According to the present invention, excellent freshness preservation properties can be obtained regardless of the film thickness. Considering the strength of the packaging bag, although it depends on the application, it is more preferable that the thickness of the bag-shaped plastic film be around 20 μm to 35 μm.

[0039] The following describes the method for producing an additive for imparting freshness preservation function of the present invention, which involves liquid A containing powdered rice husks and rice wax, and liquid B containing a powdered metal complex and rice wax. Liquid A may contain the aforementioned powdered rice husks and, for example, a vegetable oil such as rice wax. In addition, other components such as liquid paraffin to impart fluidity to liquid A, or acetyl tributyl citrate to impart plasticity to the synthetic resin, may be included. Similarly, liquid B may contain a metal complex and a vegetable oil such as rice wax, and the components mentioned above may be used. Furthermore, other components such as a silicone resin to impart hydrophobicity to the synthetic resin to which the freshness preservation function is to be imparted by using the resulting stock solution as an additive may be included. In addition, an organic solvent may be used as appropriate as needed to provide suitable fluidity when sent into a supercritical fluid apparatus.

[0040] The additive of the present invention for imparting freshness-preserving function to synthetic resins, etc., is preferably formed as a masterbatch, as specified in the manufacturing method of the present invention. As described above, according to the manufacturing method of the present invention, a stock solution for forming a masterbatch containing nanocapsules containing at least the powdered metal complex and nanocapsules containing at least the powdered rice husk can be easily prepared by reacting powdered rice husk and powdered metal complex with vegetable oil using a supercritical fluid apparatus. The additive of the present invention, formed as a masterbatch containing the above stock solution at a sufficient concentration, mixes well with general-purpose synthetic resins conventionally used in the manufacture of packaging bags. As a result, when a plastic film is prepared using a resin composition containing the additive of the present invention, the powdered rice husk and powdered metal complex, which are the active ingredients of the additive, can be uniformly contained in the prepared plastic film. The resin composition containing the additive of the present invention is a useful material for producing packaging bags by molding methods such as inflation molding. The packaging bag obtained in this way will uniformly contain the powdered rice husk and powdered metal complex, which are the active ingredients of the additive of the present invention. As a result, it is considered to have become a highly practical and useful product, possessing superior freshness preservation capabilities, sufficient strength and other requirements for packaging bags, and maintaining the same semi-transparent appearance as conventional products. Furthermore, it is easy to color it using coloring agents.

[0041] The additive of the present invention, which can achieve the above-described excellent effects, can be easily obtained, for example, as follows: The additive of the present invention, which can achieve the above-described excellent effects, can be easily obtained by incorporating the stock solution for imparting the freshness-preserving function that characterizes the present invention into a resin material containing a resin selected from the group consisting of polyolefin resins such as polyethylene and polypropylene, or ABS resin, in an amount of, for example, 0.2 to 0.5 parts by mass per 100 parts by mass of resin. Preferably, the masterbatch contains the stock solution at a concentration of about 0.3 parts by mass. By using a masterbatch containing the stock solution containing powdered rice husks at a sufficient concentration in the manufacture of a plastic film for forming a packaging bag, it is possible to prepare a plastic film in which fine powdered rice husks are distributed throughout the film with a small amount of additive.

[0042] By using a masterbatch containing a high concentration of the stock solution for imparting the freshness-preserving function that characterizes the present invention, prepared as described above, the packaging bag of the present invention exhibiting high freshness-preserving properties can be easily prepared, as previously stated. Furthermore, the inventors have confirmed that even if only a small amount of additive is used in the preparation of the packaging bag, the packaging bag of the present invention can exhibit high freshness-preserving properties. Specifically, for example, when producing a packaging bag by inflation molding, it has been confirmed that a packaging bag with high freshness-preserving properties can be prepared by using a resin composition which is a mixture containing 10 parts by mass of the additive of the present invention formed as a masterbatch and 90 parts by mass of a polyolefin resin such as polyethylene. In contrast, as previously stated, the masterbatch described above contains 0.2 to 0.5 parts by mass of the stock solution of the additive in 100 parts by mass of resin. As mentioned above, the stock solution of the additive that characterizes the present invention is obtained by sending liquid A and liquid B into a supercritical fluid apparatus and reacting them. For example, the stock solution contains 1 to 3 parts by mass of each active ingredient in liquid A and liquid B per 100 parts by mass of the stock solution. Therefore, the amount of liquid A and liquid B, which are the active ingredients of the additive of the present invention that make up the stock solution contained in 100 parts by mass of plastic film that constitutes the packaging bag, is extremely small, about 0.0005 to 0.0008 parts by mass. Furthermore, the amounts of active ingredients in liquid A and liquid B that make up the stock solution of the additive of the present invention should be approximately the same, or it is preferable to use a slightly smaller amount of liquid B, which contains a metal complex, compared to liquid A, which contains rice husks. For example, it is preferable to adjust the amount of active ingredient in liquid B to be 0.7 to 0.9, with the amount of active ingredient in liquid A being 1, and then send it to the supercritical fluid apparatus.

[0043] Any synthetic resin commonly used in the preparation of packaging bags can be used as the resin. In this invention, it is preferable to use polyolefin resins such as polyethylene or polypropylene. It is also preferable to use high-density polyethylene (HDPE). In other words, according to the inventors' research, by using HDPE as the main raw material for the bag, the resulting packaging bag can be made strong and resistant to tearing even when filled with heavy items. [Examples]

[0044] Further specific examples of the above-described embodiment will be explained below with reference to examples and comparative examples. However, the present invention is not limited to the following examples. Unless otherwise specified, parts or % are based on mass.

[0045] [Example 1] As the base resin used in manufacturing packaging bags, high-density polyethylene pellets, which have been conventionally used in the manufacture of packaging bags, were used. Then, the additive of the present invention, which is formed as a masterbatch, was added to the high-density polyethylene pellets of the base resin to impart freshness-preserving function to the formed plastic film. The additive formed as a masterbatch was prepared by applying the manufacturing method of the present invention using the supercritical apparatus described above, to prepare a stock solution of the additive containing powdered rice husks, powdered metal complex, and vegetable oil, and the product was made using this stock solution. When preparing the stock solution, the powdered rice husks used as raw materials had a median diameter of approximately 50 μm to 60 μm on average. The powdered metal complex used was phthalocyanine iron powder (manufactured by Tokyo Chemical Industry Co., Ltd.), which is sold as a pigment. The vegetable oil used was rice wax, which has a melting point of approximately 75°C. These are all representative examples, and the additive of the present invention is not limited to these.

[0046] In the embodiments of the present invention, in order to smoothly deliver liquid A, which contains powdered rice husks and vegetable oil, and liquid B, which contains powdered metal complex and vegetable oil, to a supercritical fluid apparatus, the fluidity was adjusted by adding the above-mentioned components to liquid A and / or liquid B using an organic solvent or liquid paraffin. Then, liquids A and B sent into the supercritical fluid apparatus were subjected to carbon dioxide supercritical polymerization under conditions of 9 MPa pressure / 90°C. After polymerization, the temperature was slowly lowered to remove the carbon dioxide gas, and the reaction product was removed from the supercritical fluid apparatus to obtain the stock solution. As mentioned above, the vegetable oil used in the embodiments has a melting point of about 75°C, so when the temperature drops, the vegetable oil contained in the reaction product (stock solution) solidifies rapidly, and as a result, the surface of the powdered rice husks and powdered metal complex in the reaction product is quickly and uniformly coated.

[0047] In the embodiments of the present invention, a masterbatch was prepared by incorporating the stock solution of the additive specified in the present invention, prepared as described above, into a resin material. In the embodiments of the present invention, polyethylene was used as the resin material to contain the stock solution, considering that the final product would be a packaging bag made of high-density polyethylene. Furthermore, the masterbatch was prepared by incorporating the stock solution into the resin material so that its content was 0.3% by mass.

[0048] Using the masterbatch of the additive of the present invention described above, a resin composition raw material for producing a packaging bag was prepared by adding and mixing it with pellets of high-density polyethylene, the base resin. In this case, 10 parts by mass of the masterbatch of the additive of the present invention prepared above was used for 100 parts by mass of high-density polyethylene. In the example of the present invention, the obtained resin composition was used as a raw material and subjected to inflation molding to produce a polyethylene packaging bag with dimensions of approximately 40 cm in length, approximately 30 cm in width, and 25 μm in thickness. Upon visual observation, the obtained packaging bag was uniformly translucent. Furthermore, it did not tear under normal force when pulled by hand. In the raw solution of the additive used to produce the plastic film constituting the packaging bag of Example 1, the amount of active ingredients in solution A, which contains rice husks and vegetable oil, was 0.00075% by mass, and the amount of active ingredients in solution B, which contains a metal complex and vegetable oil, was 0.00058% by mass.

[0049] [Example 2] Except for replacing the base resin with polypropylene, a packaging bag for Example 2 was prepared in the same manner as in Example 1, and containing the same additives as used in Example 1. Visual inspection of the packaging bag for Example 2 revealed that the obtained packaging bag was uniformly translucent. Furthermore, it did not tear under normal force when pulled by hand.

[0050] [Comparative Example 1] In the comparative example, the stock solution preparation using the supercritical fluid apparatus as in Example 1 was carried out using only solution A, which contained powdered rice husks and vegetable oil. Then, a masterbatch was prepared using the stock solution obtained without using a metal complex. The packaging bag for the comparative example was prepared in the same manner as in Example 1. When the obtained packaging bag for Comparative Example 1 was visually observed, the resulting packaging bag was uniformly translucent. However, it was not possible to obtain the excellent freshness preservation function obtained with the packaging bags of Examples 1 and 2, which used a powdered metal complex in combination.

[0051] (Evaluation Result 1 - Evaluation by Visual Observation) The inventors of the present invention confirmed the freshness preservation performance of the plastic film packaging bag of Example 1 obtained as described above by placing vegetables inside. As a result, they found that the following excellent effects can be obtained. First, one cabbage was placed in the packaging bag of Example 1, and the bag containing the cabbage was placed in a refrigerator to begin storage, and storage continued for 41 days. During that time, the storage condition of the cabbage was examined by removing the cabbage from the packaging bag and visually observing it. The condition of the outer leaves (appearance) of the cabbage was observed by visual inspection and by touching with clean, gloved fingers after removing it from the packaging bag. In addition, the cabbage after 41 days from the start date was cut open and observed, including the condition of the inside.

[0052] As a result, initially, after 20 days from the start of storage, there was almost no change in the appearance of the cabbage. Then, after about 30 days from the start of storage, a slight yellow discoloration was observed on the cabbage leaves. After 41 days from the start of storage, the yellow area on the outer leaves of the cabbage had grown larger, but the core at the cut surface remained white, and although the yellow area on the outer leaves had grown larger, it was still possible to hold it without any problems. Furthermore, the difference in color of the core at the cut surface of a cabbage cut in half with a knife after 41 days, the feel of the hardness of the cabbage when cut with a knife, and the difference in the slimy feel when touching the outer leaves all confirmed that the freshness of the cabbage stored in the packaging bag of Example 1 was maintained in a remarkably good state. Furthermore, when lettuce, broccoli, Shine Muscat grapes, komatsuna (Japanese mustard spinach), cucumber, and cut vegetables were placed in the packaging bag of Example 1 and evaluated in the same way as with cabbage, the results showed excellent freshness retention, similar to that of cabbage.

[0053] In contrast, a comparative test was conducted using cabbages of the same freshness and size as those used in the examples, in the same manner as in the examples. In the comparative test, instead of the freshness-preserving bags used in the examples, commercially available freshness-preserving bags that are currently widely used were used. These commercially available freshness-preserving bags use Oya stone as a manufacturing material. One cabbage was placed in this freshness-preserving bag and stored for a long period of time in the same refrigerator as in the examples, starting from the same date as in the examples. As a result, the condition of the stored cabbages was as follows. First, 14 days after the start of storage, a small yellow area was observed on the outer leaves of the cabbage. Then, 20 days after the start of storage, the yellow area on the outer leaves became larger, and by 41 days after the start of storage, the yellow area had spread to almost the entire outer leaf of the cabbage. Furthermore, by 41 days after the start of storage, the leaves below the outer leaves also had yellow areas, and the outer leaves felt slimy to the touch. In the comparative test, the cabbage stored in the conventional freshness-preserving bag for 41 days had a slightly brown core, and felt softer when cut with a knife compared to the cabbage stored in the packaging bag of the example for 41 days.

[0054] (Evaluation Result 2 - Evaluation based on color analysis of the image) In addition to the visual evaluation described above, to conduct a more objective evaluation, photographic images of the vegetables used as test subjects were used, and the information in the photographic images was color-separated to evaluate the state of freshness preservation. Specifically, a freshness preservation test was conducted using packaging bag FR, which was prepared in Example 1 and measures approximately 40 cm in length and 30 cm in width, a commercially available packaging bag A made from Oya stone and possessing freshness preservation properties of the same size, and a commercially available packaging bag B made from rice bran and possessing freshness preservation properties. Approximately the same size cabbages were placed in each of the three test bags: packaging bag FR from Example 1, and the commercially available packaging bags A and B used for comparison. Approximately the same size and condition of cabbages were placed in each bag, and the bags were stored for a long period in the vegetable compartment of the same refrigerator. For the three test subjects, photographs of the cabbages in each bag were taken under the same conditions from day 0 to day 41 of the test, and the freshness preservation properties were evaluated by image analysis using the obtained photographic images. Specifically, we performed hue analysis on the cabbage photographs obtained at each stage of development, and determined the amount of green, brown, and yellow regions in each photograph to evaluate them relatively. The evaluation method using color analysis of the cabbage photographs is described below.

[0055] The photographic images of the cabbage were formatted as BMP (bitmap) images, and these images were analyzed in detail. The colors were classified based on the RGB values ​​of red (R), green (G), and blue (B), and the number of pixels and the proportion of each color were quantified using Python. The classification criteria for green, yellow, and brown colors used to evaluate freshness were as follows.

[0056] (Color classification criteria) (1) Green: R-value: 0-100, G-value: 100-255, B-value: 0-100 (2) Yellow: R-value: 150-255 G-value: 150-255 B-value: 0-100 (3) Brown: R-value: 100-255, G-value: 50-150, B-value: 0-100

[0057] Next, the hue information was extracted by converting to the HSV color space, which consists of three components: hue, saturation, and lightness. Then, the pixels of green, yellow, and brown were counted. The freshness preservation was then evaluated using the number of green, yellow, and brown pixels obtained by counting the pixels of each color for photographic images of cabbage stored in a refrigerator for 0, 20, and 41 days. Specifically, considering the discoloration of the cabbage during storage, the total number of pixels of green, yellow, and brown was set to 100, and the proportion of each of the three colors' pixel counts was calculated. Cabbage with a smaller decrease in the proportion of green pixels was judged to have better freshness preservation. When evaluating using brown, a larger increase in the proportion of brown pixels indicated that the freshness had deteriorated. The following are the set values ​​for the hue ranges of the three colors green, yellow, and brown used in the above evaluation.

[0058] (Set the hue range) (1) Green area: [(35,50,50),(85,255,255)] (2) Yellow area: [(20,50,50),(30,255,255)] (3) Area of ​​brown: [(10,50,50),(20,255,255)]

[0059] Table 1 shows the results of a color analysis of photographic images of cabbage stored in the vegetable compartment of the same refrigerator using three different packaging bags, at various storage times. Specifically, Table 1 shows the percentage of the area occupied by green, with the total number of pixels of the three colors (green, yellow, and brown) set to 100, as analyzed for each photographic image of the stored cabbage. As shown in Table 1, when using packaging bag FR in the example, unlike when using commercially available packaging bags A and B, the cabbage placed in the bag retained significantly more green color even after 41 days, confirming that the bag has unprecedented freshness preservation capabilities. Figure 2A is a graph showing the evaluation results of freshness preservation based on the change in the green area of ​​the cabbage photographic images shown in Table 1 over time.

[0060] TIFF2026111486000001.tif42170

[0061] Table 2, similar to Table 1, shows the evaluation results of color analysis of photographic images of cabbage in the same refrigerator's vegetable compartment, using three different packaging bags, at various storage times. Specifically, Table 2 shows the percentage of the area occupied by brown, with the total number of pixels for the three colors (green, yellow, and brown) being set to 100, as analyzed for each photographic image of the stored cabbage. As shown in Table 2, when using packaging bag FR in the example, unlike when using commercially available packaging bags A and B, the area of ​​brown in the cabbage inside the bag was significantly smaller even after 41 days of storage, confirming that the bag exhibits good freshness preservation capabilities. Figure 2B is a graph of the evaluation results obtained by observing the change in the area of ​​brown in the photographic images of cabbage shown in Table 2 over time.

[0062] TIFF2026111486000002.tif40170

[0063] Table 3 shows the results of a color analysis of photographic images of cabbage stored in the vegetable compartment of the same refrigerator using three different packaging bags, at various storage times. Specifically, Table 3 shows the percentage of the area occupied by yellow, with the total number of pixels of the three colors (green, yellow, and brown) being set to 100, as analyzed for each photographic image of the stored cabbage. As shown in Table 3, when using packaging bag FR in the example, unlike when using commercially available packaging bags A and B, the increase in the yellow area of ​​the cabbage placed in the bag was small even after 41 days, confirming that the bag has superior freshness preservation capabilities that conventional products cannot achieve. Figure 2C is a graph showing the evaluation results of freshness preservation based on the change in the yellow area of ​​the cabbage photographic images shown in Table 3 over time.

[0064] TIFF2026111486000003.tif40170

[0065] (Evaluation Result 3 - Intensity Evaluation) The strength of the high-density polyethylene packaging bag of Example 1 and the polypropylene packaging bag of Example 2 was confirmed by pulling them in various directions with both hands. As a result, it was confirmed that both the bags of Example 1 and Example 2 had the same strength as commercially available packaging bags of similar thickness that were used as a comparison when the freshness preservation performance was evaluated earlier.

Claims

1. An additive used in the manufacture of a plastic film having freshness-preserving properties, characterized by comprising powdered rice husks, a powdered metal complex, and vegetable oil, for imparting freshness-preserving properties.

2. The additive for imparting freshness preservation function according to claim 1, wherein the metal complex is selected from at least one of the group consisting of metal phthalocyanines, metal porphyrin complexes, and metal carbonyl complexes.

3. An additive for imparting freshness preservation function according to claim 1 or 2, which is formed as a masterbatch.

4. The additive for imparting freshness preservation function according to claim 1 or 2, wherein the melting point of the vegetable oil is 70°C or higher and 85°C or lower.

5. A method for manufacturing an additive for imparting freshness-preserving function to a plastic film, A method for producing an additive for imparting freshness preservation function, comprising the steps of: preparing a liquid A containing powdered rice husks and vegetable oil, and a liquid B containing a powdered metal complex and vegetable oil; sending the prepared liquids A and B into a supercritical fluid apparatus and performing carbon dioxide supercritical polymerization in the supercritical fluid apparatus to prepare a stock solution of the additive; and preparing a masterbatch by incorporating the stock solution of the additive prepared in the first step in an amount of 0.2 to 0.5 parts by mass per 100 parts by mass of resin.

6. A method for producing an additive for imparting freshness preservation function according to claim 5, wherein the melting point of the vegetable oil is 70°C or higher and 85°C or lower.

7. A method for producing an additive for imparting freshness preservation function according to claim 5 or 6, wherein the resin constituting the resin material is selected from at least one of the group consisting of polyolefin resins and ABS resins.

8. The method for producing an additive for imparting freshness preservation function according to claim 7, wherein the polyolefin resin is either a high-density polyethylene resin or polypropylene.

9. A method for producing an additive for imparting freshness preservation function according to claim 5 or 6, wherein the metal complex is selected from at least one of the group consisting of metal phthalocyanines, metal porphyrin complexes, and metal carbonyl complexes.

10. A packaging bag characterized by being made of a bag-shaped plastic film formed by inflation molding using a resin composition obtained by mixing 100 parts by mass of a polyolefin resin with an additive for imparting freshness preservation function as described in claim 3, which is formed as a masterbatch, in an amount of 9 parts by mass to 12 parts by mass.

11. The packaging bag according to claim 10, wherein the thickness of the plastic film is 8 μm or more and 50 μm or less.

Images