Completely biodegradable water-retaining natural polymer and method for producing same

Abstract

Provided are: a completely biodegradable water-retaining natural polymer that comprises a material derived from a natural material; and a method for producing the same.　The completely biodegradable water-retaining natural polymer includes a polysaccharide that is crosslinked by a photoreactive crosslinking agent derived from a natural extract. The polysaccharide includes at least one selected from the group consisting of xanthan gum, guar gum, gum arabic, gellan gum, alginic acid, glucomannan, carrageenan, and tara gum. This method for producing a completely biodegradable water-retaining natural polymer includes: a step for mixing a polysaccharide with a photoreactive crosslinking agent derived from a natural extract to obtain a mixture; and a step for irradiating the mixture with light having a wavelength of 200-600 nm. The polysaccharide includes at least one selected from the group consisting of xanthan gum, guar gum, gum arabic, gellan gum, alginic acid, glucomannan, carrageenan, and tara gum.

Description

Fully biodegradable water-retaining natural polymer and method for producing the same

[0001] The present invention relates to a fully biodegradable water-retaining natural polymer. The present invention relates to a method for producing a fully biodegradable water-retaining natural polymer.

[0002] The economies of various countries depend more or less on agriculture. In agriculture, a huge amount of water is required for irrigation, but in many regions, the reduction of arable land is progressing due to water shortage. Therefore, it is said that 30 to 40% of the productive land in the world remains uncultivated.

[0003] A superabsorbent polymer (hereinafter also referred to as SAP: Super Absorbent Polymer) is a material that absorbs and retains a large amount of moisture, and has a three-dimensional network structure in which polymers mainly composed of water-soluble monomers are bonded by a cross-linking reaction. SAP is generally composed of ionic monomers and has the characteristic of a large liquid uptake capacity because of its low cross-linking density (up to 1000 times its own weight). Also, SAP absorbs and retains an amount of aqueous solution equivalent to several hundred times its own weight while holding the aqueous solution under pressure. SAP has the characteristic of a large liquid uptake capacity compared with conventional hydrogels.

[0004] SAP is widely used in many fields such as agriculture, horticulture, medicine, pharmacy, food, hygiene, construction, civil engineering, cryogenics, and biomedicine. SAP is used, for example, as a biosensor, disposable diaper, sanitary napkin, and plant irrigation regulator. Also, SAP is used for wastewater treatment and for applications such as blocking cracks and water leakage. In the food industry, SAP is used as a food additive or as an insert for absorbing liquids. Also, in the medical field, SAP is used for controlling the release of drugs, enzymes, etc., and for constructing artificial organs, and is also used for contact lenses, etc.

[0005] Conventional synthesized SAPs include polymers such as polyacrylates, sulfonated polystyrenes, polyvinyl alcohols, polyethene oxides, polyvinylpyrrolidones, polyacrylonitriles, and polyacrylamides. Of these, polymers like polyacrylamide are also used for water retention purposes in agriculture. They exhibit high water absorption capacity and release 95% of their water freely under the suction pressure of plant roots.

[0006] However, most existing SAPs (Solid State Refining) are manufactured using petroleum-derived raw materials or solvents, resulting in a significant environmental impact during production. Furthermore, SAPs produced in this manner also have a high environmental impact during use, potentially harming not only crops, soil, soil moisture content, and soil fertilizer capacity, but also farm operators. These SAPs pose a high risk of soil and air pollution. Additionally, these SAPs either lack sufficient biodegradability or take too long to completely biodegrade. Therefore, these SAPs are unsuitable for crops and soil. Moreover, coolants made using existing SAPs require a large amount of energy for incineration during disposal, resulting in a significant environmental impact during disposal.

[0007] In light of this background, the present inventors have developed an environmentally friendly superabsorbent polymer and a method for producing the same, which is substantially completely biodegradable, has good water retention capacity and sustainability (see Patent Document 1). In this specification, "completely biodegradable" means that the inorganic and metallic substances contained in the raw materials of the polymer are not decomposed, but the polymer is decomposed into water and carbon dioxide by the action of microorganisms in the soil. However, the superabsorbent polymer disclosed in Patent Document 1 uses sulfosuccinic acid as a crosslinking agent. Although sulfosuccinic acid is biodegradable, it is chemically produced. There was a need to further reduce the environmental burden during material production and to conduct technical studies on SAP that is more suitable for crops and soil.

[0008] International Publication No. 2021 / 019577

[0009] This invention takes the above circumstances into consideration and aims to provide a completely biodegradable water-retaining natural polymer and a method for producing the same.

[0010] As a result of diligent research to solve the above problems, the present inventors have established a method for producing a completely biodegradable water-retaining natural polymer made from naturally derived materials, and have completed the present invention. That is, the present invention has the following features. The completely biodegradable water-retaining natural polymer of the present invention is made from naturally derived materials, is environmentally friendly, does not cause pollution, and is substantially completely biodegradable. The method for producing the completely biodegradable water-retaining natural polymer of the present invention allows for the easy production of the natural polymer and is an environmentally friendly manufacturing method.

[0011] Furthermore, as a result of diligent research to solve the above problems, the inventors conceived of applying a photoreactive crosslinking agent in the production of water-retaining polymers. When using a photoreactive crosslinking agent, the crosslinking sites and reaction rate can be precisely controlled by adjusting the irradiation distance, irradiation time, and light intensity. As a result, a robust water-retaining polymer structure can be produced. Light irradiation also has the advantage of being environmentally friendly.

[0012] Biopolymers, derived from natural materials, are naturally occurring polymers created through extensive scientific research. They have an extremely low environmental impact and are used in a wide variety of applications. Currently, the use of biopolymers is attracting significant attention in many sectors, including the food, pharmaceutical, and agricultural industries. Furthermore, renewable biomaterials represent an environmentally friendly option for reducing environmental pollution and waste generation.

[0013] A fully biodegradable water-retaining natural polymer according to one aspect of the present invention comprises a polysaccharide crosslinked with a photoreactive crosslinking agent derived from a natural extract. The polysaccharide comprises at least one selected from the group consisting of xanthan gum, guar gum, gum arabic, gellan gum, alginic acid, glucomannan, carrageenan, and tara gum.

[0014] One embodiment described above consists of materials derived from natural products, is environmentally friendly, and is less likely to pollute the environment. It achieves complete biodegradability in a water-retaining polymer. Polysaccharides crosslinked with a photoreactive crosslinking agent create a polymer with a highly water-retaining structure. One embodiment described above exhibits a high water absorption ratio.

[0015] In one embodiment described above, the polysaccharide may contain pectin. When the polysaccharide contains pectin, the water absorption ratio is improved.

[0016] In one embodiment described above, the pectin may be contained in an extract from at least one selected from the group consisting of citrus fruits, bananas, and potatoes. When the pectin is contained in the extract, the water absorption ratio is further improved.

[0017] In one of the above embodiments, the photoreactive crosslinking agent may have a double bond in its molecular structure. When the photoreactive crosslinking agent has a double bond in its molecular structure, the water absorption ratio is further improved.

[0018] In one embodiment described above, the photoreactive crosslinking agent may contain at least one selected from the group consisting of linoleic acid, α-linolenic acid, fumaric acid, curcumin, genepine (genipin), tannic acid, citric acid, ellagic acid dihydrate, sorbic acid, DL-pyroglutamic acid, resveratrol, crocin, tocotrienol, beta-carotene, oleocanthal, and coumarin. When the photoreactive crosslinking agent contains the above components, the water absorption ratio is further improved.

[0019] A method for producing a fully biodegradable water-retaining natural polymer according to another aspect of the present invention comprises the steps of: mixing a polysaccharide with a photoreactive crosslinking agent derived from a natural extract to obtain a mixture; and irradiating the mixture with light of a wavelength of 200 nm to 600 nm. The polysaccharide includes at least one selected from the group consisting of xanthan gum, guar gum, gum arabic, gellan gum, alginic acid, glucomannan, carrageenan, and tara gum.

[0020] Another embodiment described above consists of materials derived from natural products, is environmentally friendly, and is less likely to pollute the environment. Complete biodegradability is achieved in the water-retaining polymer. Polysaccharides crosslinked with a photoreactive crosslinking agent produce a polymer with a highly water-retaining structure. Another embodiment described above produces a polymer that exhibits a high water absorption ratio.

[0021] In one of the above-mentioned embodiments, the polysaccharide may contain pectin. When the polysaccharide contains pectin, the water absorption ratio is improved.

[0022] In one of the above-described embodiments, the pectin may be contained in an extract from at least one selected from the group consisting of citrus fruits, bananas, and potatoes. When the pectin is contained in the extract, the water absorption ratio is further improved.

[0023] In one of the other embodiments described above, the photoreactive crosslinking agent may have a double bond in its molecular structure. When the photoreactive crosslinking agent has a double bond in its molecular structure, the water absorption ratio is further improved.

[0024] In one of the above-described embodiments, the photoreactive crosslinking agent may contain at least one selected from the group consisting of linoleic acid, α-linolenic acid, fumaric acid, curcumin, genepine (genipin), tannic acid, citric acid, ellagic acid dihydrate, sorbic acid, DL-pyroglutamic acid, resveratrol, crocin, tocotrienol, beta-carotene, oleocanthal, and coumarin. When the photoreactive crosslinking agent contains the above-described component, the water absorption ratio is further improved.

[0025] This invention provides a natural polymer that is derived from natural materials, is environmentally friendly, pollution-free, and is substantially completely biodegradable. Furthermore, this invention provides a method for producing a substantially completely biodegradable natural polymer that is derived from natural materials and utilizes biological waste.

[0026] The present invention provides a fully biodegradable, water-retaining natural polymer in which polysaccharides are crosslinked with a photoreactive crosslinking agent derived from a natural extract, and a method for producing the same.

[0027] In this specification, "biodegradable" means having the property of being broken down by microorganisms present in the natural environment, such as soil, and converted into harmless water, carbon dioxide, and inorganic salts. The water-retaining natural polymer of the present invention is composed solely of naturally derived components and is therefore substantially completely biodegradable. "Substantially completely biodegradable" means that it is completely broken down into substances harmless in the natural environment without leaving any harmful intermediate products during the decomposition process, and no substances that adversely affect the environment are produced. Furthermore, superabsorbent polymers have the meaning commonly used in the art and are also called SAP: Super Absorbent Polymer, and include polymers designed to have high water retention performance, absorbing tens to thousands of times their own weight in water.

[0028] (Polysaccharides) In the water-retaining natural polymer of the present invention, polysaccharides are crosslinked by a photoreactive crosslinking agent to form a crosslinked structure. The polysaccharides include at least xanthan gum. Xanthan gum is a polysaccharide composed of glucose, mannose, and glucuronic acid. Xanthan gum is a natural polysaccharide obtained by the fermentation process of Xanthomonas campestris. Xanthan gum can be produced, for example, by adding sugar and other nutrients to a culture medium of Xanthomonas campestris and fermenting it to induce secretion, then separating and recovering the xanthan gum from the culture medium. Alternatively, commercially available xanthan gum may be used.

[0029] In the water-retaining natural polymer of the invention, the polysaccharide may be xanthan gum alone, or it may be used in combination with other polysaccharides. The polysaccharides other than xanthan gum include natural polysaccharides. The polysaccharides other than xanthan gum are not particularly limited, but for example, they include one or more selected from the group consisting of pectin, gum arabic, linseed gum, guar gum, tragacanth gum, cellulose, and cellulose derivatives. Among the above polysaccharides, pectin, gum arabic, linseed gum, guar gum, and tragacanth gum have many hydroxyl groups in their molecules, and these hydroxyl groups are bonded to other polysaccharides by hydrogen bonds to form a crosslinked structure.

[0030] Polysaccharides include, for example, polysaccharides that can gel. Polysaccharides may include hydrocolloids other than xanthan gum. Hydrocolloids include, in addition to xanthan gum, for example, gellan gum, alginic acid, glucomannan, carrageenan, or tara gum. Hydrocolloids, for example, form a network structure when in contact with water, and this network structure traps water. Polysaccharides may contain one type of polysaccharide, or two or more types of polysaccharides. There are no particular restrictions on the combination of polysaccharides. Therefore, polysaccharides may contain xanthan gum and guar gum, or xanthan gum and gellan gum. Polysaccharides may contain gellan gum and guar gum. Polysaccharides may contain xanthan gum, guar gum, and gellan gum.

[0031] The polysaccharide may further contain pectin. Pectin is mainly found in the cell walls of plants and is primarily composed of polygalacturonic acid, in which galacturonic acid is linked by α-1,4 bonds. Pectin contains molecules in which galacturonic acid and methyl-esterified galacturonic acid, in which the carboxyl groups of galacturonic acid are methyl-esterified, are linked together. The pectin used in the water-retaining natural polymer of the present invention may contain galacturonic acid and methyl-esterified galacturonic acid in any ratio, for example, with a galacturonic acid content of 75% or more and a methoxy content of 9-15%. In other words, the pectin used in the water-retaining natural polymer of the present invention may have any degree of esterification, for example, with a degree of esterification of less than 50%, for example, 20-25%.

[0032] The pectin used in this invention is derived from natural products, such as fruits, seaweed, and vegetables. Fruits from which pectin can be derived include, for example, citrus fruits and bananas. The pectin is not particularly limited, but can be obtained from, for example, the peels of citrus fruits and banana peels. Citrus fruits are not particularly limited, but include, for example, oranges, mandarins, grapefruits, lemons, limes, yuzu, amanatsu, hassaku, iyokan, kiyomi, shiranuhi, setoka, bitter orange, pomelo, kabosu, sudachi, ponkan, kumquat, and shikwasa, and may include oranges or lemons.

[0033] Seaweed from which pectin is derived includes, for example, green algae such as Ulva and Green Laver, red algae such as Porphyra and Gracilaria, and brown algae such as Kelp, Arame, Kajime, Wakame, and Sargassum. Vegetables from which pectin is derived include, for example, potatoes. Pectin is extracted, for example, from starch obtained from potatoes. Potatoes are not particularly limited, but include, for example, potatoes. Potatoes may include sweet potatoes, taro, yams, or konjac.

[0034] In the present invention, pectin is not particularly limited, but may be derived from biological waste. Examples of biological waste include waste from fruits, seaweed, and vegetables. Of these, biological waste in which the edible and non-edible parts are clearly separated, and in which it is not necessary to use the edible parts as raw materials in the production of water-retaining natural polymers, is environmentally friendly. Specifically, the pectin is derived from one or more fruit wastes selected from the group consisting of citrus peels such as oranges and lemons, banana peels, and jackfruit peels.

[0035] This invention uses biological waste to produce a water-retaining natural polymer. Therefore, the biological waste is treated without the need for a separate treatment process. Since the water-retaining natural polymer is derived from biological waste, it is a natural product and environmentally friendly. The use of biological waste is efficient, including in terms of cost, and is beneficial for crop growth and farm management. The water-retaining natural polymer can create sustainable farmland.

[0036] In the present invention, the method for extracting pectin from natural materials such as biological waste is not particularly limited, but for example, the following procedure may be used. In the following method, biological waste is used as the raw material for pectin, but the present invention is not particularly limited to this, and materials other than biological waste may be used.

[0037] Pectin is extracted from biological waste, such as fruit peels, collected from various locations, including juice shops and food processing plants. The collected biological waste is washed to remove foreign matter such as leaves and twigs. Subsequently, the biological waste is washed again with water and then with distilled water to remove physical impurities from the surface of the biological waste. The biological waste is then dried at a temperature below 60°C for 24 to 48 hours until its weight is constant. The dried material is crushed and sieved through a mesh size of 60 to 80. The resulting powder and water are mixed in a ratio of 1:50 to obtain a mixed solution. Lemon juice is used to adjust the pH of the solution to 1 to 4.

[0038] The mixed solution is heated at 55°C for 3 hours and then cooled. After cooling, the soluble pectin and insoluble pectin are separated. For example, the cooled mixed solution is passed through a cheesecloth. As a result, an aqueous solution containing soluble pectin is obtained from the mixture of soluble and insoluble pectin. Insoluble pectin remains on the cheesecloth.

[0039] Next, ethanol is added to the aqueous solution containing soluble pectin while stirring. The soluble pectin precipitates. Subsequently, water and ethanol are removed by centrifugation or filtration, and the mixture is further dried to obtain pectin in powder form.

[0040] In the present invention, an improved method for extracting pectin from biological waste is used, as described below. Specifically, dried powder of biological waste and water are mixed in a ratio of 1:50, and then, for example, lemon juice is added to obtain an aqueous solution with a pH of 1 to 4. The obtained solution is shaken and stirred in a vibration chamber at 400 Hz to 1000 Hz for 10 to 45 minutes. Subsequently, a pectin-degrading enzyme is added to the shaken and stirred solution, and it is left to stand at room temperature (15 to 30°C) for 24 to 48 hours and cooled. After cooling, soluble pectin and insoluble pectin are separated. Subsequently, pectin is precipitated in the same manner as described above. Water and ethanol are then removed by centrifugation or filtration, and the solution is further dried to obtain pectin in powder form.

[0041] In the present invention, the pectin used in the production of the water-retaining natural polymer may be any pectin. For example, the pectin has a galacturonic acid content of more than 75%, a methoxy content of 9-15%, and a degree of esterification of less than 50%, for example, 20-25%.

[0042] (Photo-crosslinking agent) In the present invention, the photo-crosslinking agent includes a compound that is activated by exposure to light such as ultraviolet light or visible light containing blue light and forms a crosslinked structure between polysaccharides. The photo-crosslinking agent used in the present invention is a crosslinking agent that is activated by exposure to light. Further, the photo-crosslinking agent used in the present invention may be a compound having an action of promoting crosslink formation between polysaccharides, and may be a compound whose function as a so-called crosslinking agent is not known.

[0043] In the water-retaining natural polymer of the present invention, the photo-crosslinking agent may be a compound having a double bond (including a conjugated double bond) in its molecular structure. The photo-crosslinking agent having a double bond in its molecular structure exhibits an action of forming a crosslinked structure between polysaccharides by cleavage of the double bond portion upon light irradiation to generate radicals.

[0044] In the water-retaining natural polymer of the present invention, the photo-crosslinking agent is derived from a natural extract. Examples of the photo-crosslinking agent derived from a natural extract include polyphenols, carotenoids, vitamin E (tocotrienol, tocopherol), fatty acids, organic acids, amino acid derivatives, and pigments. The photo-crosslinking agent may include, for example, a compound having a double bond (including a conjugated double bond) in its molecular structure. The photo-crosslinking agent derived from a natural extract used in the water-retaining natural polymer of the present invention may include not only the photo-crosslinking agent extracted from a natural product but also a photo-crosslinking agent generated by synthesis as long as it is the same substance as the photo-crosslinking agent extracted from a natural product.

[0045] In the water-retaining natural polymer of the present invention, the photo-crosslinking agent is a group containing a double bond and is at least one selected from the group consisting of linoleic acid, α-linolenic acid, citric acid, and DL-pyroglutamic acid. Further, the photo-crosslinking agent contains at least one selected from the group consisting of fumaric acid, curcumin, genipin, tannic acid, ellagic acid dihydrate, sorbic acid, resveratrol, crocin, tocotrienol, beta-carotene, oleocanthal, and coumarin, which is a group containing a conjugated double bond.

[0046] Linoleic acid is one of the fatty acids mainly contained in vegetable oils. As linoleic acid, although not particularly limited, those extracted from vegetable oils or the like may be used, or commercially available products may be used.

[0047] α-Linolenic acid is one of the fatty acids contained in flaxseed oil, chia seeds, walnuts, and rapeseed oil. As α-linolenic acid, those extracted from the above-mentioned foods or the like may be used, or commercially available products may be used.

[0048] Fumaric acid is an organic acid contained in vegetables such as asparagus and pumpkins, citrus fruits, berries, and mushrooms. Also, fumaric acid may be produced during the fermentation process of beer and wine. As fumaric acid, those extracted from the above-mentioned foods or the like may be used, or commercially available products may be used.

[0049] Curcumin is one of the pigments contained in the roots such as turmeric. As curcumin, although not particularly limited, those extracted from the rhizomes of turmeric or the like may be used, or commercially available products may be used.

[0050] Genipin is produced by hydrolyzing geniposidic acid, which is an iridoid glycoside obtained from fruits such as gardenia. As genipin, those extracted and produced from gardenia or the like may be used, or commercially available products may be used.

[0051] Tannic acid is one of the polyphenols contained in the bark, leaves, and fruits of plants. As tannic acid, those extracted from plants and fruits or the like may be used, or commercially available products may be used.

[0052] Citric acid is an organic acid abundantly contained mainly in citrus fruits such as lemons, oranges, and grapefruit. As citric acid, those extracted from the above-mentioned foods or the like may be used, or commercially available products may be used.

[0053] Ellagic acid dihydrate is one of the polyphenols contained in berries and nuts. As ellagic acid dihydrate, those extracted from the above-mentioned foods or the like may be used, or commercially available products may be used.

[0054] Sorbic acid is a type of unsaturated fatty acid found in the fruits of the rowan tree, etc. Rubic acid may be extracted from the aforementioned fruits, etc., or commercially available products may be used.

[0055] DL-pyroglutamic acid is a cyclic amino acid produced by the elimination of water molecules from glutamic acid. DL-pyroglutamic acid is a mixture of L-pyroglutamic acid and D-pyroglutamic acid. DL-pyroglutamic acid is produced by microbial fermentation processes or by dehydration reactions using glutamic acid obtained from food products. Glutamic acid is extracted from fermented foods such as miso and soy sauce, plant-based foods such as tomatoes, beans, and nuts, and animal-based foods such as meat, fish, and dairy products. Glutamic acid can also be produced by fermenting sugars using microorganisms such as molds and lactic acid bacteria.

[0056] Resveratrol is a type of polyphenol found in grape seeds and skins, red wine, and the thin skin of peanuts. While not particularly limited, resveratrol can be extracted from grapes and peanuts, or commercially available products can be used.

[0057] Crocin is a water-soluble carotenoid pigment. While there are no particular limitations on the type of crocin used, extracts from gardenia and saffron, for example, may be used, or commercially available products may be used.

[0058] Tocotrienols are a type of vitamin E. While not specifically limited, tocotrienols extracted from rice bran and palm oil may be used, or commercially available products may be used.

[0059] Beta-carotene is a pigment found in plants such as carrots and spinach, and is a precursor to vitamin A. While not particularly limited, beta-carotene can be extracted from, for example, carrots and spinach, or commercially available products can be used.

[0060] Oleocanthal is an organic compound extracted from extra virgin olive oil. While not particularly limited, oleocanthal can be extracted from extra virgin olive oil or other sources, or commercially available products may be used.

[0061] Coumarin is a type of lactone and is known as one of the aromatic compounds found in plants. While not particularly limited, coumarin extracted from sources such as cherry leaves, cinnamon, and tonka beans may be used, or commercially available coumarins may be used.

[0062] The water-retaining natural polymer of the present invention may further contain other components besides the polymer in which polysaccharides are crosslinked with a photoreactive crosslinking agent, without departing from the objectives of the present invention. Other components include, for example, water, water absorption rate regulators, pH adjusters, antibacterial agents, preservatives, surfactants, softeners, weather resistance improvers, colorants, and fragrances. Alternatively, the water-retaining natural polymer of the present invention may consist solely of the polymer in which polysaccharides are crosslinked with a photoreactive crosslinking agent.

[0063] (Manufacturing Method) The present invention provides a method for producing the biodegradable water-retaining natural polymer described above. The manufacturing method of the present invention comprises the steps of: mixing a polysaccharide and a photoreactive crosslinking agent derived from a natural extract to obtain a mixture; and activating the photoreactive crosslinking agent to crosslink the polysaccharide. For example, the manufacturing method of the present invention comprises the steps of: mixing a polysaccharide and a photoreactive crosslinking agent derived from a natural extract to obtain a mixture; and irradiating the mixture with light of a wavelength of 200 nm to 600 nm. The polysaccharide and the photoreactive crosslinking agent may have the configuration described above.

[0064] Conventional methods may be used to mix the polysaccharide and the photoreactive crosslinking agent. For example, the materials may be mixed using a kneader that kneads the materials after adding them. The mixture obtained in the mixing step may be crushed into a powder before proceeding to the next step.

[0065] Any means known in the art may be used to activate the photoreactive crosslinking agent and crosslink the polysaccharides. Activation of the photoreactive crosslinking agent may be performed by any means known in the art. Activation of the photoreactive crosslinking agent only requires providing energy that allows the double bonds (including conjugated double bonds) of the photoreactive crosslinking agent to cleave and generate radicals. The cleavage of the double bonds and the generation of radicals create a crosslinked structure between the polysaccharides. In the process of activating the photoreactive crosslinking agent, radicals are generated by any means, such as light, heat, and radiation. For example, the process of activating the photoreactive crosslinking agent and crosslinking the polysaccharides may involve irradiating the mixture with light, for example, light with a wavelength of 200 nm to 600 nm, to activate the photoreactive crosslinking agent and crosslink the polysaccharides. Alternatively, the process of activating the photoreactive crosslinking agent and crosslinking the polysaccharides may involve applying heat to the mixture to activate the photoreactive crosslinking agent and crosslink the polysaccharides.

[0066] The water-retaining natural polymer of the present invention is produced, for example, as follows: Polysaccharides and a photoreactive crosslinking agent are kneaded using a kneader. The kneaded polysaccharides and photoreactive crosslinking agent are crushed into a substantially powdery state (for example, mesh size 4 to 400). Subsequently, the substantially powdery knead is irradiated with light of a wavelength of 200 nm to 600 nm to obtain the water-retaining natural polymer of the present invention. The water-retaining natural polymer of the present invention is obtained by irradiation with ultraviolet light or blue light.

[0067] Here, the photoreactive crosslinking agent and polysaccharides are, if necessary, classified or ground before mixing to adjust the particle size to a mesh size of 4 to 400. For mixing, known mixing equipment such as a kneader, unscrew mixer, twin-screw mixer, and roll mill are used. For crushing after mixing, known methods such as bead mills, ball mills, and vibratory crushing using a shaker are used. The light irradiation source may include known irradiation sources such as xenon lamps, halogen lamps, deuterium lamps, and excimer lamps. Of these steps, the crushing step after mixing and the light irradiation step may be carried out simultaneously.

[0068] The mixing ratio of xanthan gum and photoreactive crosslinking agent during kneading can be appropriately adjusted according to the desired degree of polymerization, but for example, it may be 100:100 to 100:0.0005 parts by mass. If the mixing ratio of the photoreactive crosslinking agent is too low compared to xanthan gum (100:0.0005 parts by mass), the crosslinking reaction may not proceed sufficiently, and the desired water absorption performance may not be achieved. However, if the mixing ratio is 100:0.0005 or higher compared to xanthan gum, the crosslinking reaction will proceed sufficiently, and the desired water absorption performance will be obtained. Also, if the mixing ratio of the photoreactive crosslinking agent is too high compared to xanthan gum (100:100 parts by mass), the network structure after the crosslinking reaction may become too dense, and the desired water absorption performance may not be achieved. However, if the ratio is 100:100 or lower, the network structure after the crosslinking reaction will not become too dense, and the desired water absorption performance will be obtained.

[0069] If the polysaccharide further contains pectin, the mixing ratio of pectin to the photoreactive crosslinking agent during kneading can be appropriately adjusted according to the desired degree of polymerization, but for example, it may be 100:5 to 100:0.0005 parts by mass. If the mixing ratio of the photoreactive crosslinking agent is too low compared to pectin (100:0.0005 parts by mass), the crosslinking reaction may not proceed sufficiently, and the desired water absorption performance may not be achieved. However, if the mixing ratio is 100:0.0005 or higher compared to pectin (100:0.0005 parts by mass), the crosslinking reaction will proceed sufficiently, and the desired water absorption performance will be obtained. Also, if the mixing ratio of the photoreactive crosslinking agent is too high compared to pectin (100:5 parts by mass), the network structure after the crosslinking reaction may become too dense, and the desired water absorption performance may not be achieved. However, if the mixing ratio of the photoreactive crosslinking agent is 100:5 or lower, the network structure after the crosslinking reaction will not become too dense, and the desired water absorption performance will be obtained.

[0070] The mixing ratio of pectin to xanthan gum during kneading can be appropriately adjusted according to the desired degree of polymerization, but for example, it may be 100:5 to 100:500 parts by mass, or 100:10 to 100:80 parts by mass. If the mixing ratio of pectin is too low compared to xanthan gum (100:500 parts by mass), the network structure may not be sufficiently formed after the crosslinking reaction, and the desired water absorption performance may not be achieved. However, if the mixing ratio of pectin is 100:500 or more parts by mass compared to xanthan gum, the network structure will be sufficiently formed after the crosslinking reaction, and the desired water absorption performance will be obtained. Similarly, if the mixing ratio of pectin is too high compared to xanthan gum (100:5 parts by mass), the network structure may not be sufficiently formed after the crosslinking reaction, and the desired water absorption performance may not be achieved. However, if the mixing ratio of pectin is 100:5 or less parts by mass compared to xanthan gum, the network structure will be sufficiently formed after the crosslinking reaction, and the desired water absorption performance will be obtained.

[0071] After the compound is crushed, the photoreactive crosslinking agent can be activated. For example, the photoreactive crosslinking agent is activated by irradiating the crushed material with light. The degree to which the photoreactive crosslinking agent is activated can be adjusted according to the desired degree of polymerization of the polymer. For example, the desired degree of polymerization of the polymer can be obtained by adjusting the irradiation time of the light irradiated onto the crushed material. The irradiation time of the light irradiated onto the crushed material may be, for example, 30 seconds to 10 minutes, or 30 seconds to 5 minutes. If the irradiation time is shorter than 30 seconds, the crosslinking reaction may not proceed sufficiently, and the desired water absorption performance may not be achieved. However, if the irradiation time is 30 seconds or longer, the crosslinking reaction will proceed sufficiently, and the desired water absorption performance will be obtained. Also, if the irradiation time is longer than 10 minutes, the formed network structure may break down, and the desired water absorption performance may not be achieved. However, if the irradiation time is 10 minutes or less, the formed network structure will be maintained, and the desired water absorption performance will be obtained.

[0072] The particle size of the water-retaining natural polymer of the present invention can be any particle size by adjusting the degree of crosslinking. For example, the volume-average particle size of the water-retaining natural polymer of the present invention is 30 μm to 5000 μm. If the volume-average particle size of the water-retaining natural polymer of the present invention is less than 30 μm, it may not mix uniformly when mixed with water and may remain as clumps, but if it is 30 μm or more, it can be mixed uniformly with water. Also, if the volume-average particle size of the water-retaining natural polymer of the present invention is greater than 5000 μm, it may take a long time to gel when mixed with water and may not exhibit the desired water absorption performance, but if it is 5000 μm or less, it will gel more quickly when mixed with water and the desired water absorption performance can be obtained. Known methods can be used to measure the volume-average particle size. For example, a laser diffraction / scattering particle size distribution analyzer (Partica LA-960V2, manufactured by HORIBA) may be used.

[0073] The water-retaining natural polymer of the present invention is widely used in agriculture, horticulture, medicine, pharmaceuticals, food, hygiene, construction, civil engineering, cooling agents, and biomedicine. For example, the water-retaining natural polymer may be used in biosensors, disposable diapers, sanitary napkins, plant irrigation regulators, wastewater treatment, and applications to block cracks and leaks. Furthermore, in the food industry, the water-retaining natural polymer may be used as a food additive or as an insert for absorbing liquids. In the medical field, the water-retaining natural polymer may be used to control the release of drugs and enzymes, and may also be used in the construction of artificial organs and contact lenses.

[0074] The water-retaining natural polymer of the present invention may be used, for example, for water retention purposes in agriculture. For instance, the water-retaining natural polymer of the present invention can be mixed into soil for plant growth to enhance the soil's water retention capacity. This promotes plant growth even in arid and water-scarce regions. Since the water-retaining natural polymer of the present invention is manufactured solely from readily biodegradable plant-derived components, it is completely biodegradable. Therefore, because the water-retaining natural polymer of the present invention is completely biodegradable after use, it is environmentally friendly and does not pollute the soil or air.

[0075] The components released when the water-retaining natural polymer of the present invention biodegrades are organic matter, and therefore are not harmful, leaving no residue that would adversely affect the environment. When the water-retaining natural polymer of the present invention biodegrades, it releases various organic substances such as sugars, organic acids, alcohols, fatty acids, amino acids, proteins, carbon dioxide, and water as nutrients to the soil, improving soil quality and promoting plant growth. Therefore, the water-retaining natural polymer of the present invention can be used as an organic fertilizer that reduces the amount of other fertilizers required for the growth of crop plants by 40-60%.

[0076] The water-retaining natural polymer of this invention reduces the water requirements for plant growth by 60-80%. Because water usage can be minimized, it is extremely useful for water conservation. The water thus saved can then be used for a variety of other purposes, such as irrigating land that remains uncultivated due to drought.

[0077] The water-retaining natural polymer of the present invention is useful for enhancing the soil's moisture retention capacity, even in barren land and marble slurry. It can provide a solution for using land plots that have been left barren or have become barren due to the dumping of marble slurry.

[0078] Furthermore, reducing the water requirements for plant growth by 60-80% lowers agricultural production costs. This reduction in agricultural production costs increases the income generated by agriculture.

[0079] Furthermore, the water-retaining natural polymer of the present invention can retain water for approximately 15 to 21 days while holding 60 to 80% of its maximum absorbable water capacity. This environmentally friendly water-retaining natural polymer of the present invention not only retains water, but also gradually biodegrades in the soil, continuously releasing nutrients necessary for plant growth, thereby increasing plant growth by 100 to 300% compared to normal conditions without the use of the water-retaining natural polymer. Even plants that grow slowly under normal soil conditions will see significantly accelerated growth with the use of the water-retaining natural polymer of the present invention. In addition, the water-retaining natural polymer of the present invention is reusable, as it does not completely decompose for up to 12 months after initial use and retains its ability to absorb water and supply water to plants again.

[0080] (Cooling agent) The present invention may also provide a cooling agent comprising the water-retaining natural polymer described above. The cooling agent is used to lower the temperature of an object or to maintain an object at a low temperature. In addition to the water-retaining natural polymer, the cooling agent may also contain water, a water absorption rate regulator, a pH adjuster, an antibacterial agent, a preservative, a surfactant, a softener, a weather-resistant agent, a colorant, and a fragrance. The cooling agent may further include a container for containing the water-retaining natural polymer.

[0081] The containers used for the above-mentioned coolant are not particularly limited, but include, for example, plastic containers, aluminum pouches, nonwoven fabrics, paper containers, foamed plastic containers, glass containers, metal containers, or biodegradable plastic containers. The above-mentioned coolant does not need to be incinerated after use and is completely biodegradable in the soil. Therefore, it can be disposed of without contaminating the soil.

[0082] The embodiments of the present invention will be described in detail below with reference to examples, but the present invention is not limited to the following embodiments unless it exceeds the gist of the invention.

[0083] [Measurement of Water Absorption Ratio] Water-retaining natural polymers were prepared by the following tests 1 to 9, and their water absorption ratios were measured. The water absorption ratios of the prepared water-retaining natural polymers were measured according to JIS-K7223 as follows: 0.1 g to 1.2 g (W3 (g)) of water-retaining natural polymer particles were placed in a tea bag (mesh opening 55 μm). The tea bag containing the water-retaining natural polymer particles was immersed in a beaker containing 100 mL of pure water (Milli-Q water) for 24 hours. After that, it was removed and left to drain for 10 minutes, and its weight was measured. This weight is W1 (g). The same procedure was performed on a tea bag without water-retaining natural polymer particles, and its weight was measured. This weight is W2 (g).

[0084] The water absorption ratio is calculated using the following formula: Water absorption ratio (g / g) = (W1 - W2) / W3

[0085] [Test 1] Water-retaining natural polymers A1 to A12 were prepared using polysaccharides and photoreactive crosslinking agents, and their water absorption ratios were measured. Table 1 shows the composition and water retention ratios of water-retaining natural polymers A1 to A12.

[0086] [Polysaccharides] Xanthan gum was used as the polysaccharide. The xanthan gum was obtained from Marugo Corporation (product code: marugo09).

[0087] [Photoreactive Crosslinking Agents] Linoleic acid, α-linolenic acid, fumaric acid, curcumin, sorbic acid, citric acid, glycerol, genepine (genipin), and tannic acid were used as photoreactive crosslinking agents. These were supplied by Fujifilm Wako Pure Chemical Industries, Ltd. Ellagic acid dihydrate and DL-pyroglutamic acid were also used as photoreactive crosslinking agents. These were supplied by Tokyo Chemical Industries, Ltd.

[0088] [Example A1] 100 parts by mass of xanthan gum and 0.2 parts by mass of linoleic acid were kneaded for 15 minutes using a single-screw kneader (Osaka Chemical Co., Ltd.; Wonder Crusher) to obtain a nearly powdery mixture. The obtained mixture was crushed with a grinder and then irradiated with light using a handy UV lamp (manufactured by AS ONE Corporation) (wavelength: 254 nm, irradiation time: 60 seconds, irradiation distance: 150 mm). As a result, the water absorption ratio of the water-retaining natural polymer A1 was 196.2 g / g.

[0089] [Example A2] The procedure was carried out in the same manner as in Example A1, except that α-linolenic acid was used instead of linoleic acid, and water-retaining natural polymer A2 was obtained. The water absorption ratio of water-retaining natural polymer A2 was 180.9 g / g. [Example A3] The procedure was carried out in the same manner as in Example A1, except that fumaric acid was used instead of linoleic acid, and water-retaining natural polymer A3 was obtained. The water absorption ratio of water-retaining natural polymer A3 was 204.6 g / g. [Example A4] The procedure was carried out in the same manner as in Example A1, except that curcumin was used instead of linoleic acid, and water-retaining natural polymer A4 was obtained. The water absorption ratio of water-retaining natural polymer A4 was 193.0 g / g. [Example A5] The procedure was carried out in the same manner as in Example A1, except that 100 parts by mass of linoleic acid was used, and water-retaining natural polymer A5 was obtained. The water absorption ratio of water-retaining natural polymer A5 was 302.0 g / g. [Example A6] The procedure was carried out in the same manner as in Example A2, except that 100 parts by mass of α-linolenic acid was used, and a water-retaining natural polymer A6 was obtained. The water absorption ratio of the water-retaining natural polymer A6 was 187.3 g / g.

[0090] [Example A7] The procedure was carried out in the same manner as in Example A1, except that 0.2 parts by mass each of fumaric acid, sorbic acid, citric acid, and glycerol were used instead of linoleic acid, and water-retaining natural polymer A7 was obtained. The water absorption ratio of water-retaining natural polymer A7 was 202.6 g / g. [Example A8] The procedure was carried out in the same manner as in Example A1, except that 0.2 parts by mass each of fumaric acid, sorbic acid, and citric acid were used instead of linoleic acid, and water-retaining natural polymer A8 was obtained. The water absorption ratio of water-retaining natural polymer A8 was 198.7 g / g. [Example A9] The procedure was carried out in the same manner as in Example A1, except that genepine (genipin) was used instead of linoleic acid, and water-retaining natural polymer A9 was obtained. The water absorption ratio of water-retaining natural polymer A9 was 192.0 g / g. [Example A10] The procedure was carried out in the same manner as in Example A1, except that tannic acid was used instead of linoleic acid, and water-retaining natural polymer A10 was obtained. The water absorption ratio of water-retaining natural polymer A10 was 221.0 g / g. [Example A11] The procedure was carried out in the same manner as in Example A1, except that ellagic acid dihydrate was used instead of linoleic acid, and water-retaining natural polymer A11 was obtained. The water absorption ratio of water-retaining natural polymer A11 was 187.0 g / g. [Example A12] The procedure was carried out in the same manner as in Example A1, except that DL-polyglutamic acid was used instead of linoleic acid, and water-retaining natural polymer A12 was obtained. The water absorption ratio of water-retaining natural polymer A12 was 198.0 g / g.

[0091]

[0092] [Test 2] Pectin P1-P4 was prepared and further used with polysaccharides and photoreactive crosslinking agents to produce water-retaining natural polymers B1-B10. The water absorption ratio of each was measured. Table 2 shows the composition of water-retaining natural polymers B1-B10.

[0093] [Extraction of Pectin P1] The peel of a navel orange (citrus sinensis) was dried at 60°C for 24 hours, and then ground until the powder size was 60 mesh. 8 g of this powder was placed in a 500 mL Erlenmeyer flask, followed by the addition of 400 mL of pure water (Milli-Q water). Lemon juice was then added, and the solution was adjusted to a pH of 1-4, after which it was shaken in a vibration chamber at 980 Hz for 30 minutes. Pectinase was then added, and the mixture was allowed to stand at room temperature for 24 hours. The solution was then cooled to 10°C, and soluble pectin was separated from insoluble pectin using a filter cheesecloth. Ethanol was then added with stirring, and the soluble pectin precipitated. Subsequently, the soluble pectin was separated by centrifugation for 30 minutes and filtration, and after drying and grinding, powdered pectin P1 was obtained.

[0094] [Extraction of Pectin P2] The extraction of pectin P2 was carried out in the same manner as for pectin P1, except that sweet lemon (citrus limetta) peel was used instead of navel orange peel. [Extraction of Pectin P3] The extraction of pectin P3 was carried out in the same manner as for pectin P1, except that giant Cavendish banana peel was used instead of navel orange peel. [Extraction of Pectin P4] The extraction of pectin P4 was carried out in the same manner as for pectin P1, except that monkey banana peel was used instead of navel orange peel.

[0095] [Polysaccharides] The polysaccharides used were xanthan gum, guar gum, gum arabic, sebacic acid, gallic acid, and crocin. Xanthan gum (product code: marugo09) and guar gum (product code: marugo28) were sourced from Marugo Corporation. Gum arabic (product code: 016-00025), sebacic acid (product code: 196-00272, purity: Wako Grade 1), gallic acid (product code: 077-06092, Wako Grade 1), and crocin (product code: C1527) were sourced from Fujifilm Wako Pure Chemical Industries Ltd.

[0096] [Photoreactive Crosslinking Agents] Linoleic acid, α-linolenic acid, fumaric acid, curcumin, sorbic acid, citric acid, glycerol, genepine (genipin), and tannic acid were used as photoreactive crosslinking agents. These were supplied by Fujifilm Wako Pure Chemical Industries, Ltd. Ellagic acid dihydrate and DL-pyroglutamic acid were also used as photoreactive crosslinking agents. These were supplied by Tokyo Chemical Industries, Ltd.

[0097] [Examples B1-B5] 100 parts by mass of each of pectin P1-P4, 40 parts by mass of xanthan gum, and 2.5 parts by mass (partially 0.67 parts by mass) of a photoreactive crosslinking agent were kneaded in a single-screw kneader for 15 minutes to obtain a nearly powdery mixture. After the obtained mixture was crushed, it was irradiated with light (wavelength: 365 nm, irradiation time: 120 seconds, irradiation distance: 150 mm) to obtain water-retaining natural polymers B1-B5. The water absorption ratios of water-retaining natural polymers B1-B5 were distributed in the range of approximately 100 g / g to 30 g / g. Water-retaining natural polymers B1-B5 showed generally equivalent water absorption ratios. Water-retaining natural polymer B1 tended to have a higher water absorption ratio than water-retaining natural polymers B2-B5. Water-retaining natural polymer B2 tended to have a higher water absorption ratio than water-retaining natural polymers B3-B5.

[0098] [Examples B6-B10] Water-retaining natural polymers B6-B10 were prepared using 100 parts by mass of pectin P1, 40 parts by mass of polysaccharides (guar gum and gum arabic), other components (sebacic acid, gallic acid, and crocin), and 2.5 parts by mass of a photoreactive crosslinking agent. The water absorption ratios of water-retaining natural polymers B6-B10 tended to be lower than those of water-retaining natural polymers B1-B4. The water absorption ratio of water-retaining natural polymer B6 tended to be higher than that of water-retaining natural polymers B7-B10.

[0099]

[0100] From the results of Tests 1 and 2, it was confirmed that in order to exceed 30 g / g, which is an example of an effective absorption rate, the parts by mass of xanthan gum should be between 40 and 100. It was also confirmed that when pectin P1 was used, the parts by mass of xanthan gum should be between 10 and 100. The parts by mass of xanthan gum may be between 25 and 100, or between 40 and 150. The parts by mass of xanthan gum may be between 40 and 200. In all cases, it was confirmed that the absorption rate exceeded 30 g / g, which is an example of an effective absorption rate. Furthermore, in the above tests, similar water absorption rates were obtained when, in addition to xanthan gum, for example, gellan gum, alginic acid, glucomannan, carrageenan, or tara gum was used.

[0101] [Test 3] Pectins P5-P8 were prepared, and water-retaining natural polymers C1-C16 containing each of the pectins P5-P8 were fabricated. The water absorption ratio of the water-retaining natural polymers C1-C16 was measured. Table 3 shows the composition and water retention ratio of the water-retaining natural polymers C1-C16. Pectins P5-P8 contain citrus.

[0102] [Pectin P5] Pectin P5 was obtained from Unitech Foods Co., Ltd. Pectin P5 is UNIPECTINE® AYD 5110 SB. [Pectin P6] Pectin P6 was obtained from Unitech Foods Co., Ltd. Pectin P6 is UNIPECTINE® SS 150 CITRUS. [Pectin P7] Pectin P7 was obtained from Unitech Foods Co., Ltd. Pectin P7 is UNIPECTINE® SS 845 C. [Pectin P8] Pectin P8 was obtained from Unitech Foods Co., Ltd. Pectin P8 is UNIPECTINE® AYD 3110 SB.

[0103] [Polysaccharides] Xanthan gum was used as the polysaccharide. The xanthan gum was obtained from Marugo Corporation (product code: marugo09).

[0104] [Photoreactive Crosslinking Agent] Citric acid was used as the photoreactive crosslinking agent. The citric acid was obtained from Fujifilm Wako Pure Chemical Industries, Ltd. (product code: 038-06925).

[0105] [Example C1] 100 parts by mass of pectin P5, 25 parts by mass of xanthan gum, and 2.5 parts by mass of citric acid powder were kneaded in a single-screw kneader for 15 minutes to obtain a nearly powdery mixture. After the obtained mixture was crushed, it was irradiated with light (wavelength: 365 nm, irradiation time: 120 seconds, irradiation distance: 150 mm) to obtain water-retaining natural polymer C1. The water absorption ratio of water-retaining natural polymer C1 was 272.4 g / g.

[0106] [Example C2] The procedure was carried out in the same manner as for water-retaining natural polymer C1, except that 50 parts by mass of xanthan gum was used, and water-retaining natural polymer C2 was obtained. The water absorption ratio of water-retaining natural polymer C2 was 311.1 g / g. [Example C3] The procedure was carried out in the same manner as for water-retaining natural polymer C1, except that 75 parts by mass of xanthan gum was used, and water-retaining natural polymer C3 was obtained. The water absorption ratio of water-retaining natural polymer C3 was 260.4 g / g. [Example C4] The procedure was carried out in the same manner as for water-retaining natural polymer C1, except that 100 parts by mass of xanthan gum was used, and water-retaining natural polymer C4 was obtained. The water absorption ratio of water-retaining natural polymer C4 was 257.9 g / g.

[0107] [Example C5] The procedure was carried out in the same manner as for water-retaining natural polymer C1, except that pectin P6 was used instead of pectin P5, and water-retaining natural polymer C5 was obtained. The water absorption ratio of water-retaining natural polymer C5 was 180.2 g / g. [Example C6] The procedure was carried out in the same manner as for water-retaining natural polymer C2, except that pectin P6 was used instead of pectin P5, and water-retaining natural polymer C6 was obtained. The water absorption ratio of water-retaining natural polymer C6 was 257.2 g / g. [Example C7] The procedure was carried out in the same manner as for water-retaining natural polymer C3, except that pectin P6 was used instead of pectin P5, and water-retaining natural polymer C7 was obtained. The water absorption ratio of water-retaining natural polymer C7 was 166.5 g / g. [Example C8] The procedure was carried out in the same manner as for water-retaining natural polymer C4, except that pectin P6 was used instead of pectin P5, and water-retaining natural polymer C8 was obtained. The water absorption ratio of water-retaining natural polymer C8 was 202.3 g / g.

[0108] [Example C9] The procedure was carried out in the same manner as for water-retaining natural polymer C1, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer C9 was obtained. The water absorption ratio of water-retaining natural polymer C9 was 116.0 g / g. [Example C10] The procedure was carried out in the same manner as for water-retaining natural polymer C2, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer C10 was obtained. The water absorption ratio of water-retaining natural polymer C10 was 320.1 g / g. [Example C11] The procedure was carried out in the same manner as for water-retaining natural polymer C3, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer C11 was obtained. The water absorption ratio of water-retaining natural polymer C11 was 354.0 g / g. [Example C12] The procedure was carried out in the same manner as for water-retaining natural polymer C4, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer C12 was obtained. The water absorption ratio of the water-retaining natural polymer C12 was 365.0 g / g.

[0109] [Example C13] The process was carried out in the same manner as for water-retaining natural polymer C1, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer C13 was obtained. The water absorption ratio of water-retaining natural polymer C13 was 318.7 g / g. [Example C14] The process was carried out in the same manner as for water-retaining natural polymer C2, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer C14 was obtained. The water absorption ratio of water-retaining natural polymer C14 was 347.1 g / g. [Example C15] The process was carried out in the same manner as for water-retaining natural polymer C3, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer C15 was obtained. The water absorption ratio of water-retaining natural polymer C15 was 353.6 g / g. [Example C16] The process was carried out in the same manner as for water-retaining natural polymer C4, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer C16 was obtained. The water absorption ratio of the water-retaining natural polymer C16 was 354.1 g / g.

[0110]

[0111] The results of Test 3 confirmed that the parts by mass of xanthan gum may be between 25 and 100. The parts by mass of xanthan gum may also be between 35 and 85, or between 50 and 75. Furthermore, in the above tests, similar water absorption ratios were observed when other substances besides xanthan gum, such as gellan gum, alginic acid, glucomannan, carrageenan, or tara gum, were used.

[0112] [Test 4] Pectins P5 to P8 were prepared, and water-retaining natural polymers D1 to D16 containing each of the pectins P5 to P8 were fabricated. The water absorption ratio of the water-retaining natural polymers D1 to D16 was measured. Table 4 shows the composition and water retention ratio of the water-retaining natural polymers D1 to D16.

[0113] [Polysaccharides] Guar gum was used as the polysaccharide. The guar gum was obtained from Marugo Corporation (product code: marugo28).

[0114] [Photoreactive Crosslinking Agent] Citric acid was used as the photoreactive crosslinking agent. The citric acid was obtained from Fujifilm Wako Pure Chemical Industries, Ltd. (product code: 038-06925).

[0115] [Example D1] 100 parts by mass of pectin P5, 25 parts by mass of guar gum, and 2.5 parts by mass of citric acid powder were kneaded in a single-screw kneader for 15 minutes to obtain a nearly powdery mixture. After the obtained mixture was crushed, it was irradiated with light (wavelength: 365 nm, irradiation time: 120 seconds, irradiation distance: 150 mm) to obtain a water-retaining natural polymer D1. The water absorption ratio of the water-retaining natural polymer D1 was 30.6 g / g.

[0116] [Example D2] The procedure was carried out in the same manner as for water-retaining natural polymer D1, except that 50 parts by mass of guar gum was used, and water-retaining natural polymer D2 was obtained. The water absorption ratio of water-retaining natural polymer D2 was 28.3 g / g. [Example D3] The procedure was carried out in the same manner as for water-retaining natural polymer D1, except that 75 parts by mass of guar gum was used, and water-retaining natural polymer D3 was obtained. The water absorption ratio of water-retaining natural polymer D3 was 45.2 g / g. [Example D4] The procedure was carried out in the same manner as for water-retaining natural polymer D1, except that 100 parts by mass of guar gum was used, and water-retaining natural polymer D4 was obtained. The water absorption ratio of water-retaining natural polymer D4 was 59.9 g / g.

[0117] [Example D5] The procedure was carried out in the same manner as for water-retaining natural polymer D1, except that pectin P6 was used instead of pectin P5, and water-retaining natural polymer D5 was obtained. The water absorption ratio of water-retaining natural polymer D5 was 22.9 g / g. [Example D6] The procedure was carried out in the same manner as for water-retaining natural polymer D2, except that pectin P6 was used instead of pectin P5, and water-retaining natural polymer D6 was obtained. The water absorption ratio of water-retaining natural polymer D6 was 34.1 g / g. [Example D7] The procedure was carried out in the same manner as for water-retaining natural polymer D3, except that pectin P6 was used instead of pectin P5, and water-retaining natural polymer D7 was obtained. The water absorption ratio of water-retaining natural polymer D7 was 59.8 g / g. [Example D8] The procedure was carried out in the same manner as for water-retaining natural polymer D4, except that pectin P6 was used instead of pectin P5, and water-retaining natural polymer D8 was obtained. The water absorption ratio of water-retaining natural polymer D8 was 55.0 g / g.

[0118] [Example D9] The procedure was carried out in the same manner as for water-retaining natural polymer D1, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer D9 was obtained. The water absorption ratio of water-retaining natural polymer D9 was 44.7 g / g. [Example D10] The procedure was carried out in the same manner as for water-retaining natural polymer D2, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer D10 was obtained. The water absorption ratio of water-retaining natural polymer D10 was 71.9 g / g. [Example D11] The procedure was carried out in the same manner as for water-retaining natural polymer D3, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer D11 was obtained. The water absorption ratio of water-retaining natural polymer D11 was 63.0 g / g. [Example D12] The procedure was carried out in the same manner as for water-retaining natural polymer D4, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer D12 was obtained. The water absorption ratio of the water-retaining natural polymer D12 was 99.1 g / g.

[0119] [Example D13] The process was carried out in the same manner as for water-retaining natural polymer D1, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer D13 was obtained. The water absorption ratio of water-retaining natural polymer D13 was 9.6 g / g. [Example D14] The process was carried out in the same manner as for water-retaining natural polymer D2, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer D14 was obtained. The water absorption ratio of water-retaining natural polymer D14 was 28.4 g / g. [Example D15] The process was carried out in the same manner as for water-retaining natural polymer D3, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer D15 was obtained. The water absorption ratio of water-retaining natural polymer D15 was 49.9 g / g. [Example D16] The process was carried out in the same manner as for water-retaining natural polymer D4, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer D16 was obtained. The water absorption ratio of the water-retaining natural polymer D16 was 54.3 g / g.

[0120]

[0121] The results of Test 4 confirmed that the mass of guar gum may be between 25 and 100. The mass of guar gum may be between 50 and 75, between 50 and 100, or between 75 and 100.

[0122] [Test 5] Pectins P5 to P8 were prepared, and water-retaining natural polymers E1 to E16 containing each of the pectins P5 to P8 were fabricated. The water absorption ratio of the water-retaining natural polymers E1 to E16 was measured. Table 5 shows the composition and water retention ratio of the water-retaining natural polymers E1 to E16.

[0123] [Polysaccharides] Gum arabic was used as the polysaccharide. The gum arabic was obtained from Fujifilm Wako Pure Chemical Industries, Ltd. (product code: 016-00025).

[0124] [Photoreactive Crosslinking Agent] Citric acid was used as the photoreactive crosslinking agent. The citric acid was obtained from Fujifilm Wako Pure Chemical Industries, Ltd. (product code: 038-06925).

[0125] [Example E1] 100 parts by mass of pectin P5, 25 parts by mass of gum arabic, and 2.5 parts by mass of citric acid powder were kneaded in a single-screw kneader for 15 minutes to obtain a nearly powdery mixture. After the obtained mixture was crushed, it was irradiated with light (wavelength: 365 nm, irradiation time: 120 seconds, irradiation distance: 150 mm) to obtain a water-retaining natural polymer E1. The water absorption ratio of the water-retaining natural polymer E1 was 22.7 g / g.

[0126] [Example E2] The procedure was carried out in the same manner as for water-retaining natural polymer E1, except that 50 parts by mass of gum arabic was used. The water absorption ratio of water-retaining natural polymer E2 was 48.3 g / g. [Example E3] The procedure was carried out in the same manner as for water-retaining natural polymer E1, except that 75 parts by mass of gum arabic was used. Water-retaining natural polymer E3 was obtained. The water absorption ratio of water-retaining natural polymer E3 was 29.6 g / g. [Example E4] The procedure was carried out in the same manner as for water-retaining natural polymer E1, except that 100 parts by mass of gum arabic was used. Water-retaining natural polymer E4 was obtained. The water absorption ratio of water-retaining natural polymer E4 was 41.8 g / g.

[0127] [Example E5] The procedure was carried out in the same manner as for water-retaining natural polymer E1, except that pectin P6 was used instead of pectin P5, and water-retaining natural polymer E5 was obtained. The water absorption ratio of water-retaining natural polymer E5 was 2.3 g / g. [Example E6] The procedure was carried out in the same manner as for water-retaining natural polymer E2, except that pectin P6 was used instead of pectin P5, and water-retaining natural polymer E6 was obtained. The water absorption ratio of water-retaining natural polymer E6 was 5.4 g / g. [Example E7] The procedure was carried out in the same manner as for water-retaining natural polymer E3, except that pectin P6 was used instead of pectin P5, and water-retaining natural polymer E7 was obtained. The water absorption ratio of water-retaining natural polymer E7 was 9.5 g / g. [Example E8] The procedure was carried out in the same manner as for water-retaining natural polymer E4, except that pectin P6 was used instead of pectin P5, and water-retaining natural polymer E8 was obtained. The water absorption ratio of water-retaining natural polymer E8 was 16.1 g / g.

[0128] [Example E9] The procedure was carried out in the same manner as for water-retaining natural polymer E1, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer E9 was obtained. The water absorption ratio of water-retaining natural polymer E9 was 46.4 g / g. [Example E10] The procedure was carried out in the same manner as for water-retaining natural polymer E2, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer E10 was obtained. The water absorption ratio of water-retaining natural polymer E10 was 41.4 g / g. [Example E11] The procedure was carried out in the same manner as for water-retaining natural polymer E3, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer E11 was obtained. The water absorption ratio of water-retaining natural polymer E11 was 42.8 g / g. [Example E12] The procedure was carried out in the same manner as for water-retaining natural polymer E4, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer E12 was obtained. The water absorption ratio of the water-retaining natural polymer E12 was 34.5 g / g.

[0129] [Example E13] The procedure was carried out in the same manner as for water-retaining natural polymer E1, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer E13 was obtained. The water absorption ratio of water-retaining natural polymer E13 was approximately 0 g / g. [Example E14] The procedure was carried out in the same manner as for water-retaining natural polymer E2, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer E14 was obtained. The water absorption ratio of water-retaining natural polymer E14 was 30.0 g / g. [Example E15] The procedure was carried out in the same manner as for water-retaining natural polymer E3, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer E15 was obtained. The water absorption ratio of water-retaining natural polymer E15 was 55.2 g / g. [Example E16] The procedure was carried out in the same manner as for water-retaining natural polymer E4, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer E16 was obtained. The water absorption ratio of the water-retaining natural polymer E16 was 48.2 g / g.

[0130]

[0131] The results of Test 5 confirmed that the mass of gum arabic may be between 25 and 100. The mass of gum arabic may be between 50 and 75, between 50 and 100, or between 75 and 100. The water absorption ratio may be, for example, 10 g / g or more.

[0132] [Test 6] Pectins P5 to P8 were prepared, and water-retaining natural polymers F1 to F16 containing each of the pectins P5 to P8 were fabricated. The water absorption ratio of the water-retaining natural polymers F1 to F16 was measured. Table 6 shows the composition and water retention ratio of the water-retaining natural polymers F1 to F16.

[0133] [Polysaccharides] Sebacic acid was used as the polysaccharide. The sebacic acid was obtained from Fujifilm Wako Pure Chemical Industries, Ltd. (product code: 196-00272, purity: Wako Grade 1).

[0134] [Photoreactive Crosslinking Agent] Citric acid was used as the photoreactive crosslinking agent. The citric acid was obtained from Fujifilm Wako Pure Chemical Industries, Ltd. (product code: 038-06925).

[0135] [Example F1] 100 parts by mass of pectin P5, 25 parts by mass of sebacic acid, and 2.5 parts by mass of citric acid powder were kneaded in a single-screw kneader for 15 minutes to obtain a nearly powdery mixture. After the obtained mixture was crushed, it was irradiated with light (wavelength: 365 nm, irradiation time: 120 seconds, irradiation distance: 150 mm) to obtain a water-retaining natural polymer F1. The water absorption ratio of the water-retaining natural polymer F1 was approximately 0 g / g.

[0136] [Example F2] The procedure was carried out in the same manner as for water-retaining natural polymer F1, except that 50 parts by mass of sebacic acid was used, and water-retaining natural polymer F2 was obtained. The water absorption ratio of water-retaining natural polymer F2 was 0.5 g / g. [Example F3] The procedure was carried out in the same manner as for water-retaining natural polymer F1, except that 75 parts by mass of sebacic acid was used, and water-retaining natural polymer F3 was obtained. The water absorption ratio of water-retaining natural polymer F3 was 2.6 g / g. [Example F4] The procedure was carried out in the same manner as for water-retaining natural polymer F1, except that 100 parts by mass of sebacic acid was used, and water-retaining natural polymer F4 was obtained. The water absorption ratio of water-retaining natural polymer F4 was 3.1 g / g.

[0137] [Example F5] The procedure was carried out in the same manner as for water-retaining natural polymer F1, except that pectin P6 was used instead of pectin P5, and water-retaining natural polymer F5 was obtained. The water absorption ratio of water-retaining natural polymer F5 was 0.3 g / g. [Example F6] The procedure was carried out in the same manner as for water-retaining natural polymer F2, except that pectin P6 was used instead of pectin P5, and water-retaining natural polymer F6 was obtained. The water absorption ratio of water-retaining natural polymer F6 was 0.4 g / g. [Example F7] The procedure was carried out in the same manner as for water-retaining natural polymer F3, except that pectin P6 was used instead of pectin P5, and water-retaining natural polymer F7 was obtained. The water absorption ratio of water-retaining natural polymer F7 was 1.0 g / g. [Example F8] The procedure was carried out in the same manner as for water-retaining natural polymer F4, except that pectin P6 was used instead of pectin P5, and water-retaining natural polymer F8 was obtained. The water absorption ratio of water-retaining natural polymer F8 was 2.1 g / g.

[0138] [Example F9] The procedure was carried out in the same manner as for water-retaining natural polymer F1, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer F9 was obtained. The water absorption ratio of water-retaining natural polymer F9 was 13.1 g / g. [Example F10] The procedure was carried out in the same manner as for water-retaining natural polymer F2, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer F10 was obtained. The water absorption ratio of water-retaining natural polymer F10 was 15.2 g / g. [Example F11] The procedure was carried out in the same manner as for water-retaining natural polymer F3, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer F11 was obtained. The water absorption ratio of water-retaining natural polymer F11 was 17.5 g / g. [Example F12] The procedure was carried out in the same manner as for water-retaining natural polymer F4, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer F12 was obtained. The water absorption ratio of the water-retaining natural polymer F12 was 14.2 g / g.

[0139] [Example F13] The procedure was carried out in the same manner as for water-retaining natural polymer F1, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer F13 was obtained. The water absorption ratio of water-retaining natural polymer F13 was 0.1 g / g. [Example F14] The procedure was carried out in the same manner as for water-retaining natural polymer F2, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer F14 was obtained. The water absorption ratio of water-retaining natural polymer F14 was 0.1 g / g. [Example F15] The procedure was carried out in the same manner as for water-retaining natural polymer F3, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer F15 was obtained. The water absorption ratio of water-retaining natural polymer F15 was approximately 0 g / g. [Example F16] The procedure was carried out in the same manner as for water-retaining natural polymer F4, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer F16 was obtained. The water absorption ratio of the water-retaining natural polymer F16 was 1.1 g / g.

[0140]

[0141] The results of Test 6 confirmed that the mass of sebacic acid may be between 25 and 100. The mass of sebacic acid may be between 50 and 75, between 50 and 100, or between 75 and 100. The water absorption ratio may be, for example, 10 g / g or more. In Table 6, the water absorption ratios of water-retaining natural polymers F9 to F12 tended to be higher than those of other water-retaining natural polymers.

[0142] [Test 7] Pectins P5 to P8 were prepared, and water-retaining natural polymers G1 to G16 containing each of the pectins P5 to P8 were fabricated. The water absorption ratio of the water-retaining natural polymers G1 to G16 was measured. Table 7 shows the composition and water retention ratio of the water-retaining natural polymers G1 to G16.

[0143] [Polysaccharides] Gallic acid was used as the polysaccharide. The gallic acid was obtained from Fujifilm Wako Pure Chemical Corporation (product code: 077-06092, Wako Grade 1).

[0144] [Photoreactive Crosslinking Agent] Citric acid was used as the photoreactive crosslinking agent. The citric acid was obtained from Fujifilm Wako Pure Chemical Industries, Ltd. (product code: 038-06925).

[0145] [Example G1] 100 parts by mass of pectin P5, 25 parts by mass of gallic acid, and 2.5 parts by mass of citric acid powder were kneaded in a single-screw kneader for 15 minutes to obtain a nearly powdery mixture. After the obtained mixture was crushed, it was irradiated with light (wavelength: 365 nm, irradiation time: 120 seconds, irradiation distance: 150 mm) to obtain a water-retaining natural polymer G1. The water absorption ratio of the water-retaining natural polymer G1 was approximately 0 g / g.

[0146] [Example G2] The procedure was carried out in the same manner as for water-retaining natural polymer G1, except that 50 parts by mass of gallic acid was used, and water-retaining natural polymer G2 was obtained. The water absorption ratio of water-retaining natural polymer G2 was approximately 0 g / g. [Example G3] The procedure was carried out in the same manner as for water-retaining natural polymer G1, except that 75 parts by mass of gallic acid was used, and water-retaining natural polymer G3 was obtained. The water absorption ratio of water-retaining natural polymer G3 was approximately 0 g / g. [Example G4] The procedure was carried out in the same manner as for natural polymer G1, except that 100 parts by mass of gallic acid was used, and natural polymer G4 was obtained. The water absorption ratio of the obtained natural polymer G4 was approximately 0 g / g.

[0147] [Example G5] The procedure was carried out in the same manner as for natural polymer G1, except that pectin P6 was used instead of pectin P5, and natural polymer G5 was obtained. The water absorption ratio of the obtained natural polymer G5 was approximately 0 g / g. [Example G6] The procedure was carried out in the same manner as for water-retaining natural polymer G2, except that pectin P6 was used instead of pectin P5, and water-retaining natural polymer G6 was obtained. The water absorption ratio of water-retaining natural polymer G6 was approximately 0 g / g. [Example G7] The procedure was carried out in the same manner as for water-retaining natural polymer G3, except that pectin P6 was used instead of pectin P5, and water-retaining natural polymer G7 was obtained. The water absorption ratio of water-retaining natural polymer G7 was approximately 0 g / g. [Example G8] The procedure was carried out in the same manner as for water-retaining natural polymer G4, except that pectin P6 was used instead of pectin P5, and water-retaining natural polymer G8 was obtained. The water absorption ratio of water-retaining natural polymer G8 was approximately 0 g / g.

[0148] [Example G9] The procedure was carried out in the same manner as for water-retaining natural polymer G1, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer G9 was obtained. The water absorption ratio of water-retaining natural polymer G9 was 25.7 g / g. [Example G10] The procedure was carried out in the same manner as for water-retaining natural polymer G2, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer G10 was obtained. The water absorption ratio of water-retaining natural polymer G10 was 17.7 g / g. [Example G11] The procedure was carried out in the same manner as for water-retaining natural polymer G3, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer G11 was obtained. The water absorption ratio of water-retaining natural polymer G11 was 20.5 g / g. [Example G12] The procedure was carried out in the same manner as for water-retaining natural polymer G4, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer G12 was obtained. The water absorption ratio of the water-retaining natural polymer G12 was 25.2 g / g.

[0149] [Example G13] The procedure was carried out in the same manner as for water-retaining natural polymer G1, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer G13 was obtained. The water absorption ratio of water-retaining natural polymer G13 was approximately 0 g / g. [Example G14] The procedure was carried out in the same manner as for water-retaining natural polymer G2, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer G14 was obtained. The water absorption ratio of water-retaining natural polymer G14 was approximately 0 g / g. [Example G15] The procedure was carried out in the same manner as for water-retaining natural polymer G3, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer G15 was obtained. The water absorption ratio of water-retaining natural polymer G15 was approximately 0 g / g. [Example G16] The procedure was carried out in the same manner as for water-retaining natural polymer G4, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer G16 was obtained. The water absorption ratio of the water-retaining natural polymer G16 was approximately 0 g / g.

[0150]

[0151] The results of Test 7 confirmed that the parts by mass of gallic acid may be between 25 and 100. The parts by mass of gallic acid may be between 25 and 50, between 25 and 75, between 50 and 75, or between 50 and 100. The water absorption ratio may be, for example, 10 g / g or more. In Table 7, the water absorption ratios of water-retaining natural polymers G9 to G12 tended to be higher than those of other water-retaining natural polymers.

[0152] [Test 8] Pectins P5 to P8 were prepared, and water-retaining natural polymers H1 to H16 containing each of the pectins P5 to P8 were fabricated. The water absorption ratio of the water-retaining natural polymers H1 to H16 was measured. Table 8 shows the composition and water retention ratio of the water-retaining natural polymers H1 to H16.

[0153] [Polysaccharides] Crocin was used as the polysaccharide. Crocin was obtained from Fujifilm Wako Pure Chemical Industries, Ltd. (product code: C1527).

[0154] [Photoreactive Crosslinking Agent] Citric acid was used as the photoreactive crosslinking agent. The citric acid was obtained from Fujifilm Wako Pure Chemical Industries, Ltd. (product code: 038-06925).

[0155] [Example H1] 100 parts by mass of pectin P5, 25 parts by mass of crocin, and 2.5 parts by mass of citric acid powder were kneaded in a single-screw kneader for 15 minutes to obtain a nearly powdery mixture. After the obtained mixture was crushed, it was irradiated with light (wavelength: 365 nm, irradiation time: 120 seconds, irradiation distance: 150 mm) to obtain a water-retaining natural polymer H1. The water absorption ratio of the water-retaining natural polymer H1 was 0.5 g / g.

[0156] [Example H2] The procedure was carried out in the same manner as for water-retaining natural polymer H1, except that 50 parts by mass of crocin was used, and water-retaining natural polymer H2 was obtained. The water absorption ratio of water-retaining natural polymer H2 was 1.2 g / g. [Example H3] The procedure was carried out in the same manner as for water-retaining natural polymer H1, except that 75 parts by mass of crocin was used, and water-retaining natural polymer H3 was obtained. The water absorption ratio of water-retaining natural polymer H3 was 2.1 g / g. [Example H4] The procedure was carried out in the same manner as for water-retaining natural polymer H1, except that 100 parts by mass of crocin was used, and water-retaining natural polymer H4 was obtained. The water absorption ratio of water-retaining natural polymer H4 was 1.7 g / g.

[0157] [Example H5] The procedure was carried out in the same manner as for water-retaining natural polymer H1, except that pectin P6 was used instead of pectin P5, and water-retaining natural polymer H5 was obtained. The water absorption ratio of water-retaining natural polymer H5 was 2.3 g / g. [Example H6] The procedure was carried out in the same manner as for water-retaining natural polymer H2, except that pectin P6 was used instead of pectin P5, and water-retaining natural polymer H6 was obtained. The water absorption ratio of water-retaining natural polymer H6 was 2.3 g / g. [Example H7] The procedure was carried out in the same manner as for water-retaining natural polymer H3, except that pectin P6 was used instead of pectin P5, and water-retaining natural polymer H7 was obtained. The water absorption ratio of water-retaining natural polymer H7 was 0.8 g / g. [Example H8] The procedure was carried out in the same manner as for water-retaining natural polymer H4, except that pectin P6 was used instead of pectin P5, and water-retaining natural polymer H8 was obtained. The water absorption ratio of water-retaining natural polymer H8 was 0.6 g / g.

[0158] [Example H9] The procedure was carried out in the same manner as for water-retaining natural polymer H1, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer H9 was obtained. The water absorption ratio of water-retaining natural polymer H9 was 15.1 g / g. [Example H10] The procedure was carried out in the same manner as for water-retaining natural polymer H2, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer H10 was obtained. The water absorption ratio of water-retaining natural polymer H10 was 17.1 g / g. [Example H11] The procedure was carried out in the same manner as for water-retaining natural polymer H3, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer H11 was obtained. The water absorption ratio of water-retaining natural polymer H11 was 14.2 g / g. [Example H12] The procedure was carried out in the same manner as for water-retaining natural polymer H4, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer H12 was obtained. The water absorption ratio of the water-retaining natural polymer H12 was 11.1 g / g.

[0159] [Example H13] The procedure was carried out in the same manner as for water-retaining natural polymer H1, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer H13 was obtained. The water absorption ratio of water-retaining natural polymer H13 was 0.1 g / g. [Example H14] The procedure was carried out in the same manner as for water-retaining natural polymer H2, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer H14 was obtained. The water absorption ratio of water-retaining natural polymer H14 was 0.1 g / g. [Example H15] The procedure was carried out in the same manner as for water-retaining natural polymer H3, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer H15 was obtained. The water absorption ratio of water-retaining natural polymer H15 was 0.2 g / g. [Example H16] The procedure was carried out in the same manner as for water-retaining natural polymer H4, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer H16 was obtained. The water absorption ratio of the water-retaining natural polymer H16 was 0.1 g / g.

[0160]

[0161] The results of Test 8 confirmed that the mass of crocin may be between 25 and 100. The mass of crocin may be between 25 and 50, between 25 and 75, between 50 and 75, or between 50 and 100. The water absorption ratio should be, for example, 10 g / g or more. In Table 8, the water absorption ratios of water-retaining natural polymers H9 to H12 tended to be higher than those of other water-retaining natural polymers.

[0162] [Test 9] Pectins P5 to P8 were prepared, and water-retaining natural polymers I1 to I16 containing each of the pectins P5 to P8 were fabricated. The concentration dependence of the photoreactive crosslinking agent on the water absorption ratio of the water-retaining natural polymers I1 to I16 was measured. Table 9 shows the composition and water retention ratio of the water-retaining natural polymers I1 to I16.

[0163] [Polysaccharides] Xanthan gum was used as the polysaccharide. The xanthan gum was obtained from Marugo Corporation (product code: marugo09).

[0164] [Photoreactive Crosslinking Agent] Citric acid was used as the photoreactive crosslinking agent. The citric acid was obtained from Fujifilm Wako Pure Chemical Industries, Ltd. (product code: 038-06925).

[0165] [Example I1] 100 parts by mass of pectin P5, 40 parts by mass of xanthan gum, and 1 part by mass of citric acid powder were kneaded in a single-screw kneader for 15 minutes to obtain a nearly powdery mixture. After the obtained mixture was crushed, it was irradiated with light (wavelength: 365 nm, irradiation time: 120 seconds, irradiation distance: 150 mm) to obtain a water-retaining natural polymer I1. The water absorption ratio of the water-retaining natural polymer I1 was 241.7 g / g.

[0166] [Example I2] The procedure was carried out in the same manner as for water-retaining natural polymer I1, except that 2 parts by mass of citric acid was used, and water-retaining natural polymer I2 was obtained. The water absorption ratio of water-retaining natural polymer I2 was 331.5 g / g. [Example I3] The procedure was carried out in the same manner as for water-retaining natural polymer I1, except that 3 parts by mass of citric acid was used, and water-retaining natural polymer I3 was obtained. The water absorption ratio of water-retaining natural polymer I3 was 339.1 g / g. [Example I4] The procedure was carried out in the same manner as for water-retaining natural polymer I1, except that 4 parts by mass of citric acid was used, and water-retaining natural polymer I4 was obtained. The water absorption ratio of water-retaining natural polymer I4 was 351.3 g / g. [Example I5] The procedure was carried out in the same manner as for water-retaining natural polymer I1, except that 5 parts by mass of citric acid was used, and water-retaining natural polymer I5 was obtained. The water absorption ratio of water-retaining natural polymer I5 was 304.0 g / g.

[0167] [Example I6] Natural polymer I6 was obtained by following the same procedure as for water-retaining natural polymer I1, except that pectin P6 was used instead of pectin P5. The water absorption ratio of the obtained natural polymer I6 was 303.6 g / g. [Example I7] Natural polymer I7 was obtained by following the same procedure as for natural polymer I2, except that pectin P6 was used instead of pectin P5. The water absorption ratio of the obtained natural polymer I7 was 315.4 g / g. [Example I8] Water-retaining natural polymer I8 was obtained by following the same procedure as for water-retaining natural polymer I3, except that pectin P6 was used instead of pectin P5. The water absorption ratio of water-retaining natural polymer I8 was 324.9 g / g. [Example I9] Water-retaining natural polymer I9 was obtained by following the same procedure as for water-retaining natural polymer I4, except that pectin P6 was used instead of pectin P5. The water absorption ratio of water-retaining natural polymer I9 was 343.1 g / g. [Example I10] The procedure was carried out in the same manner as for water-retaining natural polymer I5, except that pectin P6 was used instead of pectin P5, and water-retaining natural polymer I10 was obtained. The water absorption ratio of water-retaining natural polymer I10 was 277.9 g / g.

[0168] [Example I11] The procedure was carried out in the same manner as for water-retaining natural polymer I1, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer I11 was obtained. The water absorption ratio of water-retaining natural polymer I11 was 378.4 g / g. [Example I12] The procedure was carried out in the same manner as for water-retaining natural polymer I2, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer I12 was obtained. The water absorption ratio of water-retaining natural polymer I12 was 348.2 g / g. [Example I13] The procedure was carried out in the same manner as for water-retaining natural polymer I3, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer I13 was obtained. The water absorption ratio of water-retaining natural polymer I13 was 333.3 g / g. [Example I14] The procedure was carried out in the same manner as for water-retaining natural polymer I4, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer I14 was obtained. The water absorption ratio of water-retaining natural polymer I14 was 330.2 g / g. [Example I15] The procedure was carried out in the same manner as for water-retaining natural polymer I5, except that pectin P7 was used instead of pectin P5, and water-retaining natural polymer I15 was obtained. The water absorption ratio of water-retaining natural polymer I15 was 368.9 g / g.

[0169] [Example I16] The procedure was carried out in the same manner as for water-retaining natural polymer I1, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer I16 was obtained. The water absorption ratio of water-retaining natural polymer I16 was 372.5 g / g. [Example I17] The procedure was carried out in the same manner as for water-retaining natural polymer I2, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer I17 was obtained. The water absorption ratio of water-retaining natural polymer I17 was 362.9 g / g. [Example I18] The procedure was carried out in the same manner as for water-retaining natural polymer I3, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer I18 was obtained. The water absorption ratio of water-retaining natural polymer I18 was 362.9 g / g. [Example I19] The procedure was carried out in the same manner as for water-retaining natural polymer I4, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer I19 was obtained. The water absorption ratio of water-retaining natural polymer I19 was 309.7 g / g. [Example I20] The procedure was carried out in the same manner as for water-retaining natural polymer I5, except that pectin P8 was used instead of pectin P5, and water-retaining natural polymer I20 was obtained. The water absorption ratio of water-retaining natural polymer I20 was 343.1 g / g.

[0170]

[0171] The results of Test 9 confirmed that the parts by mass of citric acid may be between 1 and 5. The parts by mass of citric acid may be between 1 and 4, or between 2 and 4. In addition, the above tests showed a similar tendency to exhibit water absorption ratios when gellan gum, alginic acid, glucomannan, carrageenan, or tara gum were used, in addition to xanthan gum.

[0172] Furthermore, tests 1 to 9 above demonstrated that, in order to cleave the double bond of the photoreactive crosslinking agent by light irradiation, any wavelength within the range of ultraviolet light and blue light, generally within the wavelength range of 200 nm to 600 nm, is acceptable.

[0173] As described above, the water-retaining natural polymer of the present invention has been found to have an excellent water absorption ratio. Furthermore, it has been found that the water-retaining natural polymer of the present invention can utilize biological waste and can be manufactured solely from materials derived from natural products. The present invention may also provide a coolant using the water-retaining natural polymer, which exhibits excellent cooling performance.

[0174] [Biodegradation Test in Soil] Since the water-retaining natural polymer of the present invention is manufactured solely from naturally derived materials, it completely biodegrades in soil within 12 months. A biodegradation test of the water-retaining natural polymer is performed, for example, as follows:

[0175] Red clay collected in Onna Village, Kunigami District, Okinawa Prefecture, is passed through a sieve with a mesh size of 250 μm to remove coarse particles. 100.0 g of this red clay is mixed with 10.00 g of a water-retaining natural polymer and placed in a pod with a filter at the bottom (product name: NALGENE Rapid-Flow, manufactured by Thermo Fisher SCIENTIFIC). The mixture is then left at room temperature for 12 months. During this period, 100 mL of pure water (Milli-Q water) is poured into the pod, and after it is confirmed that the water has completely evaporated, another 100 mL of pure water is poured in, and this process is repeated. In addition, the weight of the pod under test is measured once a month, and the weight of the mixture of red clay and water-retaining natural polymer is calculated by subtracting the weight of an empty pod that was measured beforehand. As a control (reference), only 100 g of red clay is placed in the pod, and then the weight of only red clay is measured in the same manner. As a result, it was determined that complete biodegradation occurred if the amount decreased by 10.00 g in 12 months.

[0176] As described above, the fully biodegradable water-retaining natural polymer according to the present invention contains polysaccharides crosslinked with a photoreactive crosslinking agent derived from natural extracts. The polysaccharides include at least one selected from the group consisting of xanthan gum, guar gum, gum arabic, gellan gum, alginic acid, glucomannan, carrageenan, and tara gum. The fully biodegradable water-retaining natural polymer according to the present invention is made from natural materials, is environmentally friendly, and does not easily pollute the environment. Full biodegradability is achieved in the water-retaining polymer. The polysaccharides crosslinked with the photoreactive crosslinking agent create a polymer with a highly water-retaining structure. The fully biodegradable water-retaining natural polymer embodiment exhibits a high water absorption ratio.

[0177] The above polysaccharides include pectin. In this case, the water absorption ratio is improved. The above pectin is contained in an extract from at least one selected from the group consisting of citrus fruits, bananas, and potatoes. In this case, the water absorption ratio is further improved. The above photoreactive crosslinking agent has a double bond in its molecular structure. In this case, the water absorption ratio is further improved. The above photoreactive crosslinking agent includes at least one selected from the group consisting of linoleic acid, α-linolenic acid, fumaric acid, curcumin, genepine (genipin), tannic acid, citric acid, ellagic acid dihydrate, sorbic acid, DL-pyroglutamic acid, resveratrol, crocin, tocotrienol, beta-carotene, oleocanthal, and coumarin. In this case, the water absorption ratio is further improved.

[0178] The present invention provides a method for producing a fully biodegradable water-retaining natural polymer, comprising the steps of: mixing a polysaccharide with a photoreactive crosslinking agent derived from a natural extract to obtain a mixture; and irradiating the mixture with light of a wavelength of 200 nm to 600 nm. The polysaccharide includes at least one selected from the group consisting of xanthan gum, guar gum, gum arabic, gellan gum, alginic acid, glucomannan, carrageenan, and tara gum. The production method according to the present invention is made from natural materials, is environmentally friendly, and is less likely to pollute the environment. The produced water-retaining polymer achieves complete biodegradation. The polysaccharide crosslinked by the photoreactive crosslinking agent produces a polymer with a highly water-retaining structure. The production method according to the present invention produces a polymer that exhibits a high water absorption ratio.

[0179] Although embodiments and examples of the present invention have been described above, the present invention is not necessarily limited to the embodiments and examples described above, and various modifications are possible without departing from the spirit of the invention.

[0180] As can be seen from the above-described embodiments and examples, this specification includes the following disclosures: (Note 1) A fully biodegradable water-retaining natural polymer comprising a polysaccharide crosslinked by a photoreactive crosslinking agent derived from a natural extract, wherein the polysaccharide comprises at least one selected from the group consisting of xanthan gum, guar gum, gum arabic, gellan gum, alginic acid, glucomannan, carrageenan, and tara gum. (Note 2) The fully biodegradable water-retaining natural polymer according to Note 1, wherein the polysaccharide further comprises pectin. (Note 3) The fully biodegradable water-retaining natural polymer according to Note 2, wherein the pectin is contained in an extract from at least one selected from the group consisting of citrus fruits, bananas, and potatoes. (Note 4) The fully biodegradable water-retaining natural polymer according to any one of Notes 1 to 3, wherein the photoreactive crosslinking agent has a double bond in its molecular structure. (Note 5) The photoreactive crosslinking agent comprises at least one selected from the group consisting of linoleic acid, α-linolenic acid, fumaric acid, curcumin, genipin, tannic acid, citric acid, ellagic acid dihydrate, sorbic acid, DL-pyroglutamic acid, resveratrol, crocin, tocotrienol, beta-carotene, oleocanthal, and coumarin, wherein the fully biodegradable water-retaining natural polymer is as described in any one of Notes 1 to 4. (Note 6) A method for producing a fully biodegradable water-retaining natural polymer, comprising the steps of: mixing a polysaccharide with a photoreactive crosslinking agent derived from a natural extract to obtain a mixture; and irradiating the mixture with light of a wavelength of 200 nm to 600 nm, wherein the polysaccharide comprises at least one selected from the group consisting of xanthan gum, gellan gum, alginic acid, glucomannan, carrageenan, and tara gum. (Note 7) The method for producing a completely biodegradable water-retaining natural polymer according to Note 6, wherein the polysaccharide further comprises pectin. (Note 8) The method for producing a completely biodegradable water-retaining natural polymer according to Note 7, wherein the pectin is contained in an extract from at least one selected from the group consisting of citrus fruits, bananas, and potatoes. (Note 9) The method for producing a completely biodegradable water-retaining natural polymer according to any one of Notes 6 to 8, wherein the photoreactive crosslinking agent has a double bond in its molecular structure.(Note 10) A method for producing a completely biodegradable water-retaining natural polymer according to any one of Notes 6 to 9, wherein the photoreactive crosslinking agent comprises at least one selected from the group consisting of linoleic acid, α-linolenic acid, fumaric acid, curcumin, genipin, tannic acid, citric acid, ellagic acid dihydrate, sorbic acid, DL-pyroglutamic acid, resveratrol, crocin, tocotrienol, beta-carotene, oleocanthal, and coumarin.

[0181] This invention provides an environmentally friendly, pollution-free, and substantially completely biodegradable water-retaining natural polymer widely used in agriculture, the pharmaceutical industry, food, personal hygiene, and biomedicine. Furthermore, this invention provides a water-retaining natural polymer derived from natural materials using biological waste, which is substantially completely biodegradable.

Claims

1. A fully biodegradable, water-retaining natural polymer comprising a polysaccharide crosslinked by a photoreactive crosslinking agent derived from a natural extract, wherein the polysaccharide comprises at least one selected from the group consisting of xanthan gum, guar gum, gum arabic, gellan gum, alginic acid, glucomannan, carrageenan, and tara gum.

2. The fully biodegradable water-retaining natural polymer according to claim 1, wherein the polysaccharide further comprises pectin.

3. The fully biodegradable water-retaining natural polymer according to claim 2, wherein the pectin is contained in an extract from at least one selected from the group consisting of citrus fruits, bananas, and potatoes.

4. The photoreactive crosslinking agent is a fully biodegradable water-retaining natural polymer according to any one of claims 1 to 3, having a double bond in its molecular structure.

5. The photoreactive crosslinking agent comprises at least one selected from the group consisting of linoleic acid, α-linolenic acid, fumaric acid, curcumin, genipin, tannic acid, citric acid, ellagic acid dihydrate, sorbic acid, DL-pyroglutamic acid, resveratrol, crocin, tocotrienol, beta-carotene, oleocanthal, and coumarin, the fully biodegradable water-retaining natural polymer according to any one of claims 1 to 3.

6. A method for producing a completely biodegradable water-retaining natural polymer, comprising the steps of: mixing a polysaccharide with a photoreactive crosslinking agent derived from a natural extract to obtain a mixture; and irradiating the mixture with light of a wavelength of 200 nm to 600 nm, wherein the polysaccharide comprises at least one selected from the group consisting of xanthan gum, guar gum, gum arabic, gellan gum, alginic acid, glucomannan, carrageenan, and tara gum.

7. The method for producing a completely biodegradable water-retaining natural polymer according to claim 6, wherein the polysaccharide further comprises pectin.

8. The method for producing a fully biodegradable water-retaining natural polymer according to claim 7, wherein the pectin is contained in an extract from at least one selected from the group consisting of citrus fruits, bananas, and potatoes.

9. A method for producing a completely biodegradable water-retaining natural polymer according to any one of claims 6 to 8, wherein the photoreactive crosslinking agent has a double bond in its molecular structure.

10. A method for producing a completely biodegradable water-retaining natural polymer according to any one of claims 6 to 8, wherein the photoreactive crosslinking agent comprises at least one selected from the group consisting of linoleic acid, α-linolenic acid, fumaric acid, curcumin, genipin, tannic acid, citric acid, ellagic acid dihydrate, sorbic acid, DL-pyroglutamic acid, resveratrol, crocin, tocotrienol, beta-carotene, oleocanthal, and coumarin.

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