Silver particle carrying granular high water absorption resin

Abstract

To provide a granular resin simultaneously realizing antibacterial properties and a water absorption / retention function, and a product using the same, and also to provide a technique to produce a high water absorption resin with an adhesion of silver having antibacterial properties to achieve thereof.SOLUTION: Silver is used as a vapor deposition source and a granular high water absorption resin is used as a vapor deposition object body. A physical vapor deposition is carried out through controlling a vapor deposition temperature and a vapor deposition time of a continuous vapor deposition. An evaporation substance from the silver intermittently reaches a surface of the granular high water absorption resin and produces a silver nanoparticle on the surface of the granular high water absorption resin, to obtain a silver nanoparticle carrying granular high water absorption resin in which the silver nanoparticle is carried on a granular biodegradable resin surface with an appropriate adhesive force. The granular resin has an antibacterial function as well as a water absorption / retention function; therefore can be used for a forestry soil improvement material, antibacterial daily necessaries, or the like, in line with a recycling-oriented society.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a granular superabsorbent polymer carrying antibacterial silver particles, and to a superabsorbent polymer product having antibacterial properties that uses the same. [Background technology]

[0002] The 2030 Agenda for Sustainable Development (SDGs), adopted at the United Nations Summit held at the United Nations Headquarters in New York on September 25, 2015, sets 17 common goals for the international community from 2016 to 2030. None of the goals can be achieved in isolation; they are all important but challenging goals that require strong collaboration. Notable among these are the goals of preventing global warming, building a recycling-oriented society that encompasses natural and social environments on a global scale, and ensuring hygienic and healthy lifestyles that allow people to live in safety and security. While Japan is generally considered to have a low level of achievement of its goals, it has demonstrated a proactive commitment to contributing to the world, as outlined in "Japan's Role in Achieving the Sustainable Development Goals (SDGs)" (see, for example, Non-Patent Document 2).

[0003] However, while carbon dioxide emissions and plastic waste are increasing due to human activities such as population growth and economic growth, the scope of environmental destruction caused by social factors is expanding and becoming more diverse. Furthermore, population growth, war, and conflict are increasing the number of people living in poor living conditions, making living conditions particularly difficult for growing children and the elderly whose physical strength is declining. Meanwhile, in regions with a high elderly population due to aging, there is a shortage of caregivers, and it is difficult to say that the elderly are able to live hygienic and healthy lives. Therefore, the world must come together and work together to solve these problems in order to achieve the SDGs.

[0004] The present inventors have been developing antibacterial resins that utilize antibacterial metal particles and products that use the same, and as a result of their search for antibacterial resins that can contribute to the SDGs, they have found that superabsorbent resin pellets carrying antibacterial metal particles are effective as a means of solving the problem of desertification caused by global warming and the associated climate change, among other issues of environmental destruction, and that they can be used in everyday necessities, such as disposable diapers, to ensure hygienic and healthy lives for children, the elderly, and the sick. Here, while the term "antibacterial" has traditionally been used without a proper understanding, in this specification, the term "antibacterial" is used collectively to mean a microbial control function that prevents the adverse effects of microorganisms, including sterilization, disinfection, sterilization, bacteriostasis, bacteriocontrol, preservation, antifungal properties, and the like, of microorganisms such as fungi, bacteria, and viruses, regardless of whether they are pathogenic or not (e.g., Non-Patent Document 3).

[0005] The problem of desertification is a result of global warming and the resulting climate change, as well as the destruction of terrestrial resources due to deforestation and other factors caused by population growth and the expansion of human activity. It is a problem of desertification in arid regions, which account for 41% of the world's land area, where a significant decrease in precipitation and the resulting decline in forests are occurring (e.g., Non-Patent Documents 3 and 4). In response to this problem, the United Nations has emphasized the need for research, land management, and policies aimed at preventing desertification since around 2000. To prevent the spread of desertification and its effects, afforestation activities have been carried out in arid regions around the world. Furthermore, agriculture is necessary to secure food and terrestrial food resources in arid regions. Water is the most important resource for carrying out such agriculture and forestry in arid regions. Therefore, in arid region agriculture and forestry, efforts have been made to rationally manage and efficiently use water resources through infrastructure development, such as irrigation facilities and terrace construction methods for effective water collection, as well as to improve soil water retention. Interestingly, super absorbent polymers (SAPs), which are also used in disposable diapers and other products that are essential for maintaining hygienic and healthy lives for children and the elderly, are expected to be a material that can increase the water retention capacity of soil and support afforestation and agriculture (e.g., Non-Patent Documents 3 to 5).

[0006] For example, as described in Patent Document 1, SAP with antibacterial properties is used in sanitary products such as disposable diapers and sanitary napkins used to treat urine from infants, the elderly, and sick people, and is capable of inhibiting the growth of harmful bacteria and preventing bad odors when in contact with the human body and after use. It is also disclosed that SAP can be added to soil as a water-retaining material for agricultural use to protect plant roots from pathogenic bacteria that are harmful to plants.

[0007] The reason why SAP is used as a soil water-retaining agent and soil conditioner in agriculture and forestry, as well as a material for disposable diapers, sanitary napkins, and other daily necessities, is as follows: SAP is a cross-linked polymer that absorbs more than 100 times its own weight in water when it comes into contact with water and dissipates water in a dry atmosphere. SAP is made up of starch-based and cellulose-based SAPs that use natural polymers, and cross-linked sodium polyacrylate (C-PAA-Na, Crosslinked-Poly(acrylic)) that use synthetic polymers. SAPs can be broadly categorized into C-PAA-Na-based and polyacrylamide-based SAPs. In the 1970s, biodegradable starch-based SAPs were developed in the United States as soil water-retaining agents, and PAA-Na-based SAPs were developed in Japan. Subsequently, PAA-Na-based SAPs were used in disposable diapers in Europe, leading to a worldwide market expansion. The excellent water-retaining ability of C-PAA-Na-based SAPs attracted attention, and in the 2000s, research into the use of C-PAA-Na-based SAPs, originally used in disposable diapers, as soil water-retaining agents and soil conditioners in agriculture and forestry began to actively pursue, replacing the natural polymer-based SAPs originally developed for use as soil water-retaining agents due to their biodegradability. C-PAA-Na-based SAPs now play a central role.

[0008] This is partly because C-PAA-Na SAP is inexpensive and of stable quality, but the major factors are thought to be its overwhelmingly superior water absorption and the ability to control that absorption. Also, soil water-retaining agents and soil conditioners used in agriculture and forestry, and water-absorbing agents used in disposable diapers, are required to have antibacterial properties against microorganisms in addition to their basic water-absorbing properties, and C-PAA-Na SAP has excellent water-absorbing properties that can be used in both, and it is thought to be based on the fact that it is possible to impart antibacterial properties to C-PAA-Na SAP.

[0009] However, when using C-PAA-Na-based SAP as a soil water-retaining material and soil conditioner in agriculture and forestry, it is not enough to just satisfy the water-retaining property; it must also eliminate microorganisms that cause plant diseases in the soil, promote plant growth, and not inhibit it.

[0010] It has been reported that when a large amount of C-PAA-Na-based SAP is used so that it comes into contact with plants, the expansion of the C-PAA-Na-based SAP inhibits root formation and root elongation of the plant. This raises the question of what form and how to apply the C-PAA-Na-based SAP to the soil so as not to cause a shortage of water necessary for plant growth (e.g., Patent Documents 2 and 3).

[0011] Plants require 17 nutrients for growth. C-PAA-Na-based SAPs have the ability to adsorb potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn), molybdenum (Mo), copper (Cu), and nickel (Ni). This may impair nutrient supply to plants or inhibit growth by nutrient absorption by plants. Ca and Mg ions, which are necessary for germination and rooting, have a particularly large impact on these two ions. Therefore, various approaches have been proposed to adsorb these metal ions: adjusting the content of Na salts of the carboxyl groups in C-PAA-Na-based SAPs; ion-exchanging the Na salts of the carboxyl groups for Ca salts; and coating particulate C-PAA-Na-based SAPs with inorganic compound particles containing these metals (see, for example, Patent Documents 2 and 3). However, these approaches are likely to reduce the plant's essential water-retaining function.

[0012] Furthermore, in agriculture and forestry, soil-dwelling microorganisms that harm plant growth must be eradicated, and field soil disinfection is therefore performed (e.g., Non-Patent Document 7). Soil disinfection methods include soil burning, hot steam disinfection, solar heat sterilization, soil reduction disinfection, and fungicide / insecticide disinfection. Fungicide / insecticide disinfection is the most common, and examples include DD agent, dazomet agent, carbam agent, and carbam sodium agent. While all of these can be sprayed together with SAP, they require a fumigation period of at least one week, decompose in the soil, and generate toxic gases such as clopyrin and methyl isothiocyanate, which require degassing. This soil disinfection is limited to specific fields because it is a dangerous operation requiring protective glasses and a protective mask, and also has a negative impact on aquatic animals in rivers, lakes, and other areas.

[0013] Therefore, to protect plant roots from harmful pathogens, agricultural water-retaining materials have been proposed (e.g., Patent Document 1), in which specific phosphate-based compound particles containing antibacterial metals such as silver (Ag) ions are attached to the surface of SAP particles made of natural or synthetic polymers. Also, although not SAPs, soil conditioners in which antibacterial agents are dispersed within biodegradable resins and soil conditioners in which antibacterial agents are coated on the surface of biodegradable resins (e.g., Patent Documents 4 and 5) have been reported. These antibacterial agents include inorganic antibacterial agents in which Ag ions are supported on inorganic compounds such as zeolite, silica gel, and calcium phosphate, as well as organic antibacterial agents such as quaternary ammonium salts, organic halogen-based, and phenolic organic compounds. However, when these antibacterial agents are attached to the SAP surface, their adhesion to the SAP is dependent solely on chemical adhesion forces, such as hydrogen bonds and van der Waals forces, between the SAP-constituting molecules and the antibacterial agent molecules, and they are easily detached from the SAP. Furthermore, when these antibacterial agents are dispersed within SAP, changes occur in the higher-order structure, including the extent of the molecular chains that determine the water retention capacity of SAP, which is likely to have a negative impact on the water retention function of SAP.Furthermore, few antibacterial agents are able to come into contact with microorganisms, so effective antibacterial effects cannot be expected.

[0014] Furthermore, organic antibacterial agents have safety issues. This is one factor that has led to the development of inorganic antibacterial agents that coordinate and adsorb antibacterial metal ions, which has spurred the market expansion of antibacterial plastic products. On the other hand, Ag-based antibacterial agents are known to decompose organic substances, as evidenced by the antibacterial properties of Ag ions. Therefore, Ag-based antibacterial agents are thought to degrade SAP and adversely affect its water-retaining function. Therefore, for example, to prevent SAP degradation, methods have been proposed in which antibacterial quaternary ammonium salts are chemically bonded to synthetic polymer SAPs to prevent discoloration, i.e., degradation, of the synthetic polymer SAPs (e.g., Patent Document 9), or Ag ion complexes are formed to prevent discoloration, i.e., degradation, of the synthetic polymer SAPs (e.g., Patent Document 10). Furthermore, in the case of inorganic antibacterial agents, while some antibacterial metal ions, such as Ag ions, are not toxic to the human body, others, such as large amounts of Cu ions and Fe ions, have adverse effects on cells. These ions are thought to inhibit the growth of living organisms and disrupt the natural environment (e.g., Non-Patent Document 3).

[0015] Thus, in order to utilize C-PAA-Na-based SAPs as soil water-retaining materials and soil conditioners in agriculture and forestry, it is necessary to impart safe antibacterial properties that can solve the problems of inhibiting plant growth and reducing water-retaining function.

[0016] On the other hand, when PAA-Na-based SAPs are used as liquid absorbents in sanitary products such as disposable diapers and sanitary napkins, various problems arise, as described below. For such sanitary products, the focus is primarily on odor issues, and there is a strong demand for deodorizing properties that can eliminate malodors caused by sulfur-based compounds such as hydrogen sulfide and mercaptans. For example, as described in Patent Document 6, attempts have been made to incorporate various deodorizing components into SAP, but no technology has been found that imparts antibacterial properties. However, in addition to odor issues, sanitary products using SAP can also be problematic due to skin inflammation caused by contact between the skin of the wearer of the sanitary product and excrement, such as feces and urine, or body fluids. This has led to a demand for antibacterial properties against microorganisms contained in excrement, body fluids, and other substances that are thought to be the cause of these inflammations. This has led to the development of technologies for imparting antibacterial agents to SAP.

[0017] For example, Patent Document 7 describes, as prior art, a method of imparting antibacterial properties to particulate SAP by coating the SAP with an organic antibacterial agent; a method of imparting antibacterial properties to SAP by covalently bonding a specific antibacterial silane to a C-PAA-Na-based SAP; and a method of imparting antibacterial properties to SAP by attaching amorphous calcium phosphate particles to the surface of particulate SAP with coordinated and adsorbed antibacterial metal ions such as gold or silver. However, it points out that repeated exposure to water-containing excrement makes it difficult to achieve sustained antibacterial properties. To address these issues, a method has been proposed in which inorganic fine particles adsorbed with a hydrophobic organic antibacterial agent are attached to the SAP surface to impart antibacterial properties to SAP. Patent Document 8 also proposes a method of imparting antibacterial properties to SAP by attaching an organic hydrophobic antibacterial agent and a polyhydric alcohol to the SAP surface in the form of islands, with the coverage of the organic hydrophobic antibacterial agent being 5 to 40%.

[0018] However, when organic antibacterial agents are directly attached to the SAP surface, adhesion is dependent on intermolecular hydrogen bonding and van der Waals forces between the SAP molecules and the antibacterial agent molecules. Therefore, absorption of water-containing excrement disrupts these atomic forces, resulting in the antibacterial agent's easy release and the inability to maintain its antibacterial properties. Furthermore, while covalently incorporating organic antibacterial agents into SAP strongly fixes the organic antibacterial agent to the SAP, it likely affects the higher-order structure, including the extent of molecular chains, which determines the SAP's water retention capacity, resulting in a decrease in water retention. Furthermore, when inorganic particles with antibacterial metal ions adsorbed onto the SAP surface are attached, adhesion is dependent on chemical adhesion via hydrogen bonding between the functional groups on the inorganic particle surface and the functional groups on the SAP molecules. Therefore, unless the inorganic particles are surface-treated, adhesion based on these factors is weak, resulting in the antibacterial inorganic particles easily falling off. This shedding phenomenon is also observed in methods that impart antibacterial properties to SAP by adhering inorganic microparticles adsorbed with hydrophobic organic antibacterial agents to the SAP surface.

[0019] Furthermore, when organic substances are used as substances capable of exerting the antibacterial function of antibacterial agents, the issue of toxicity cannot be ignored. This is one factor that has led to the development of inorganic antibacterial agents that coordinate and adsorb antibacterial metal ions, which has promoted the expansion of the market for antibacterial plastic products. However, as already mentioned, antibacterial metal ions also have the problem of causing SAP decomposition and reducing its water retention, and some ions, such as Cu ions and Fe ions, can have adverse effects on the human body when used in large quantities (for example, Non-Patent Document 3).

[0020] However, even when inorganic antibacterial agents are used, there is a problem specific to inorganic antibacterial agents in that if the antibacterial metal is in contact with SAP for a long period of time, the antibacterial metal ions decompose the SAP, causing discoloration and a decrease in water absorption capacity (e.g., Patent Documents 9 and 10).

[0021] Thus, in order to utilize C-PAA-Na-based SAPs in sanitary products such as diapers and napkins, it is necessary to impart a safe antibacterial function that can prevent a decrease in the antibacterial and water-absorbing functions.

[0022] There are many challenges to overcome when using SAPs, including C-PAA-Na-based SAPs, as soil water-retaining agents and soil conditioners in agriculture and forestry, and as liquid absorbents in sanitary products such as disposable diapers and sanitary napkins. However, considering that C-PAA-Na-based SAPs have overwhelmingly superior water absorption properties and can be controlled, that the basic functions required for soil water-retaining agents and soil conditioners used in agriculture and forestry, and for absorbents used in disposable diapers, are water absorption and antibacterial functions, and that they have stable quality and low price, antibacterial C-PAA-Na-based SAPs that can be used for both purposes are considered to be extremely valuable both for achieving the SDGs and industrially.

[0023] In other words, the antibacterial C-PAA-Na-based SAP is expected to contribute to the realization of a recycling-oriented society that encompasses both natural and social environments by preventing desertification, which is increasing due to global warming and the resulting climate change, and to the realization of a hygienic and healthy lifestyle by preventing the proliferation of microorganisms and foul odors when used as an absorbent material in disposable diapers and sanitary napkins used to treat the excrement of infants, children, the elderly, and the sick. [Prior art documents] [Patent documents]

[0024] [Patent Document 1] Japanese Patent Application Publication No. 5-179053 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-075055 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-048751 [Patent Document 4] Japanese Patent Application Publication No. 9-183970 [Patent Document 5] Japanese Patent Application Publication No. 9-183970 [Patent Document 6] Japanese Patent Application Laid-Open No. 2005-060677 [Patent Document 7] Japanese Patent Application Laid-Open No. 2016-104119 [Patent Document 8] Japanese Patent Application Publication No. 2017-201026 [Patent Document 9] Japanese Patent Application Publication No. 2018-131558 [Patent Document 10] Japanese Patent Application Publication No. 2019-170757 [Patent Document 11] Japanese Patent Application Laid-Open No. 2017-000969 [Patent Document 12] Japanese Patent Application Laid-Open No. 2018-135440 [Non-patent literature]

[0025] [Non-Patent Document 1] Ministry of Foreign Affairs JAPAN SDGs Action Platform, "2030 Agenda for Sustainable Development," [online], [Retrieved January 8, 2024], Internet<https: / / www.mofa.go.jp / mofaj / gaiko / oda / sdgs / pdf / 000270935.pdf> . [Non-patent document 2] Ministry of Foreign Affairs, International Cooperation Bureau, Global Issues Coordination Division, "Japan's Role in Achieving the Sustainable Development Goals (SDGs)," October 2023, [online], [Retrieved January 8, 2024], Internet<https: / / www.mofa.go.jp / mofaj / gaiko / oda / sdgs / pdf / sdgs_gaiyou_202310.pdf> . [Non-patent document 3] Yasushi Kikuchi, "Current Status and Issues of Antibacterial Metal Materials," Materia, Vol. 39, No. 2, pp. 146-150 (2000). [Non-patent document 4] Masamichi Takahashi, Kazuki Shibasaki, Eiichiro Nakama, Moriyoshi Ishizuka, Seiichi Ohta, "Use of superabsorbent polymer resins in forestry and greening fields", Journal of the Japanese Forest Society, Vol. 100, No. 6, pp. 229-236 (2018), [online], [Retrieved January 8, 2024], Internet<https: / / www.jstage.jst.go.jp / article / jjfs / 100 / 6 / 100_229 / _pdf> . [Non-patent document 5] Masamichi Takahashi, Kazuki Shibasaki, Eiichiro Nakama, Moriyoshi Ishizuka, Seiichi Ota, "Physical, Chemical, and Biological Properties of Soil Added with Superabsorbent Polymer Resin," Forest Site Research, Vol. 62, No. 1, pp. 229-236 (2020), [online], [Retrieved January 8, 2024], Internet<https: / / www.jstage.jst.go.jp / article / jjfe / 62 / 1 / 62_51 / _pdf> . [Non-patent document 6] Yasuyuki Konno, "Chemistry Carrying Water", Chemistry and Education, Vol. 66, No. 8, pp. 394-397 (2018), [online], [searched on January 8, 2024], Internet <https: / / www.jstage.jst.go.jp / article / kakyoshi / 66 / 8 / 66_394 / _pdf>.

Non-Patent Document 7

Non-Patent Document 8

Non-Patent Document 9

Non-Patent Document 10

Non-Patent Document 11

[0026] As explained in the Background Art section, antibacterial SAPs are expected to contribute to the realization of a recycling-oriented society that embraces natural and social environments by preventing desertification caused by global warming and associated climate change, and to the realization of hygienic and healthy lifestyles by preventing microbial proliferation and foul odors when used as absorbents in disposable diapers, sanitary napkins, and other products used to treat the excrement of infants, children, the elderly, and the sick. Therefore, the present invention aims to create an antibacterial SAP that can contribute to the realization of a recycling-oriented society that embraces natural and social environments by preventing desertification caused by global warming and associated climate change, and that can prevent microbial proliferation and realize hygienic and healthy lifestyles, thereby contributing to the achievement of the SDGs.

[0027] The technical objective of the present invention to achieve this objective is to develop antibacterial C-PAA-Na, which uses a crosslinked poly(acrylic acid) sodium salt (C-PAA-Na) as a superabsorbent polymer (SAP), which has excellent water absorption, stable quality, and is available at low cost, and silver (Ag), which exhibits safe and excellent antibacterial properties, as an antibacterial agent. The objective is to achieve the following main goals: first, to ensure contact between microorganisms and Ag to effectively exert the antibacterial properties of Ag ions; second, to maintain the water absorption properties of C-PAA-Na; third, to prevent decomposition of C-PAA-Na by Ag ions; and fourth, to control the adhesive force between Ag and C-PAA-Na to prevent the loss of nontoxic antibacterial metal ions upon contact with water, etc., thereby exhibiting sustained antibacterial effects. In addition to this technical challenge, another technical challenge is to solve the problem of C-PAA-Na interfering with plant rooting and growth, which is unique to the use of antibacterial C-PAA-Na as a soil water retention material and soil improvement material in agriculture and forestry.

[0028] Furthermore, the technical objective of the present invention is to achieve the same properties as C-CMC-Na by using a biodegradable crosslinked carboxymethyl cellulose sodium salt (C-CMC-Na) that is compatible with natural ecosystems and by using Ag as an antibacterial agent to produce antibacterial C-CMC-Na. This is because biodegradability is an important function required for daily necessities and is particularly desired as a soil water-retaining agent and soil conditioner used in agriculture and forestry, such as afforestation to prevent desertification. Furthermore, while starch-based SAPs are also natural polymer-based SAPs, C-CMC-Na, which is a copolymer of poly(sodium acrylate) (PAA-Na) and a crosslinked CMC-Na, has a smaller environmental impact and is widely used industrially as a thickener, etc., and is available as a stable, high-quality raw material. [Means for solving the problem]

[0029] The present inventors have been developing technology for many years to produce antibacterial metal nanoparticles on various carriers using physical vapor deposition (Patent Documents 11 and 12). In the process, they have used various granular plastics with different thermal properties as carriers to produce antibacterial metal nanoparticles on the granular plastics under various vapor deposition conditions. As a result, they have discovered that if the vapor deposition conditions are set taking into account the thermal properties of the plastics, it may be possible to control the adhesive force between the antibacterial metal nanoparticles and the granular plastics.

[0030] On the other hand, as mentioned above, antibacterial C-PAA-Na or C-CMC-Na, which use C-PAA-Na, which has excellent water absorption and stable quality and is available at low cost, or C-CMC-Na, which has both water absorption and biodegradability, as an SAP and Ag, which exhibits safe and excellent antibacterial properties, have several technical challenges to overcome: first, ensuring contact between microorganisms and Ag to effectively exert the antibacterial function of Ag ions; second, not reducing the water absorption function of C-PAA-Na; third, preventing the decomposition of C-PAA-Na by Ag ions; and fourth, controlling the adhesive force between Ag and C-PAA-Na to prevent the loss of nontoxic antibacterial metal ions upon contact with water, etc., thereby exhibiting a sustained antibacterial effect.

[0031] Furthermore, the goal is to realize a technology that will enable C-PAA-Na, which has these functions, to solve the problem of C-PAA-Na hindering plant rooting and growth, which is unique to soil water retention and soil improvement materials used in agriculture and forestry.

[0032] Therefore, the present inventors came up with the idea that, in order to address these issues, it might be effective to use antibacterial metal nanoparticle-supported granular plastic, which is produced under specific vapor deposition conditions that the antibacterial metal nanoparticles and the granular plastic have an appropriate adhesive force. That is, if antibacterial metal nanoparticles are supported on granular SAP with an appropriate adhesive force, they will remain on the granular SAP for a certain period of time and then be released, thereby achieving the desired antibacterial function and preventing SAP decomposition. In addition, because the antibacterial agent is the metal itself, the released antibacterial metal will continue to elute antibacterial metal ions thereafter.

[0033] More specifically, first, the granular SAP carrying antibacterial metal nanoparticles is present only on the surface of the resin, allowing sufficient contact between the antibacterial metal nanoparticles and microorganisms, allowing the metal ions released from the antibacterial metal nanoparticles to exert a sufficient antibacterial effect. Furthermore, the antibacterial metal nanoparticles have a large specific surface area, resulting in high antibacterial functionality. Second, the metal particles that fulfill the antibacterial function of the granular SAP carrying antibacterial metal nanoparticles are nanometer-sized and do not affect the water absorption function of the SAP. Third, after a certain period of time, the antibacterial metal nanoparticles are detached and separated from the granular SAP, preventing decomposition of the SAP by the antibacterial metal ions. This prevents discoloration and loss of water absorption due to SAP decomposition. Fourth, the antibacterial agent of the present invention is made up of antibacterial metal nanoparticles, which are not easily washed away by water, unlike antibacterial metal ions coordinated and adsorbed to inorganic compounds, etc., and the metal ions are eluted from the metal nanoparticles over a long period of time, allowing the agent to exhibit antibacterial properties over a long period of time. Furthermore, because the antibacterial metal nanoparticles are supported on the granular SAP for a certain period of time, the antibacterial function is maintained in a specific area near the granular SAP, and after the antibacterial metal nanoparticles are released, they diffuse to areas other than the specific area near the granular SAP, thereby exhibiting their antibacterial function. Therefore, the antibacterial function of the granular SAP supporting the antibacterial metal nanoparticles is maintained over both time and space.

[0034] Regarding the SAP-induced disruption of plant rooting and growth, which is a common problem with soil water-retaining agents and soil conditioners used in agriculture and forestry, granular SAP loaded with antibacterial metal nanoparticles does not lose its water-retaining properties and its antibacterial properties are maintained over time and space, eliminating the need to spray it in direct contact with plants. Therefore, SAP expansion does not disrupt plant rooting and growth. For the same reason, even if SAP adsorbs calcium ions and magnesium ions, which are nutrients necessary for plant growth, it does not disrupt the supply of nutrients to plants.

[0035] Needless to say, if Ag, which has excellent antibacterial properties and is non-toxic, is used as the antibacterial metal, it will not have the adverse effects on the human body or the environment that Cu, Fe, etc. do. Furthermore, by using C-PAA-Na as the SAP, it is possible to impart overwhelmingly superior water absorption and water retention capabilities. On the other hand, although it has inferior water absorption and water retention capabilities, by using C-CMC-Na as the SAP, it can be imparted with biodegradability suitable for a recycling-oriented society.

[0036] The present inventors investigated the possibility of solving the above-mentioned problems by using various granular plastics with different thermal properties as carriers to generate antibacterial metal nanoparticles on granular plastics under various deposition conditions. As part of this investigation, the inventors selected C-PAA-Na and C-CMC-Na as SAPs and Ag, which is highly safe and widely recognized for its antibacterial properties, and performed deposition on granular C-PAA-Na and C-CMC-Na under various conditions. As a result, they discovered specific deposition conditions that allowed them to create granular C-PAA-Na and C-CMC-Na nanoparticles carrying Ag nanoparticles that effectively combine antibacterial and water-absorbing / retaining functions without canceling each other out, and that could be used in water-retaining materials, soil conditioners, sanitary products, etc., thereby completing the present invention.

[0037] That is, first, the present invention provides a granular superabsorbent resin with antibacterial properties, characterized in that physical vapor deposition is carried out using Ag as the vapor deposition source and granular C-PAA-Na as the substrate, controlling the vapor deposition atmosphere temperature in the range of 50 to 130°C while controlling the vapor deposition time for continuous vapor deposition in the range of 0.05 to 0.2 seconds, so that evaporated substances from the Ag intermittently reach the surface of the granular C-PAA-Na, generating Ag nanoparticles on the surface of the granular C-PAA-Na, and these Ag nanoparticles are supported on the surface of the granular C-PAA-Na with moderate adhesive force.

[0038] The key point here is that the Ag nanoparticle-loaded granular C-PAA-Na nanoparticles formed by physical vapor deposition have an appropriate adhesive force between the Ag nanoparticles and the granular C-PAA-Na. This adhesive force is achieved by controlling the deposition ambient temperature between 50 and 130°C and the deposition time between continuous depositions between 0.05 and 0.2 seconds, allowing the evaporated Ag material to intermittently reach the surface of the granular C-PAA-Na nanoparticles, resulting in the formation of Ag nanoparticles on the surface of the granular C-PAA-Na nanoparticles. As a result, as mentioned above, this Ag nanoparticle-loaded granular C-PAA-Na nanoparticles effectively exhibits antibacterial and water-retaining / absorbent properties, while eliminating factors that counteract these functions.

[0039] We experimentally found that these deposition conditions can produce Ag nanoparticle-loaded granular C-PAA-Na with moderate adhesive strength. However, the factors controlling the adhesive strength between Ag nanoparticles and granular C-PAA-Na have not yet been fully elucidated. What is currently known is that there is a close relationship between the deposition conditions and the thermal properties of the C-PAA-Na substrate. The deposition conditions, particularly the deposition ambient temperature and continuous deposition time, are important. The deposition ambient temperature refers to the temperature of the gas in the vacuum chamber where physical vapor deposition is performed, not the temperature of the substrate. The continuous deposition time refers to the time during which the deposition source is continuously exposed to the substrate. The thermal properties include the glass transition temperature (Tg), melting point (Tm), and heat distortion temperature (HDT). Tg and Tm are typically measured by differential scanning calorimetry (DSC). HDT, also known as the Temperature of Deflection under Load, is a temperature measured according to JIS K7191 or ASTM D648. Briefly, in both JIS K7191 and ASTM D648, a test piece of a specific length is subjected to a three-point bending test in which a constant load is applied to the test piece and the temperature is raised at a rate of 120°C / hr. The HDT is the temperature at which the increase in bending strain is 0.2%. The loads used in JIS K7191 are 1.80 MPa and 0.45 MPa, while the corresponding loads in ASTM D648 are 1.82 MPa and 0.46 MPa.

[0040] First, we will explain the influence of the deposition ambient temperature. Adhesion between dissimilar substances, i.e., adhesion, is generally believed to be based on physical bonding forces between the adhesive and the adherend, such as van der Waals forces or hydrogen bonds between the atoms or molecules of the two, chemical bonding forces such as covalent bonds, mechanical bonding forces due to the anchoring effect based on the surface shape, and the cohesive strength of the adhesive. However, in the case of adhesion between Ag nanoparticles and granular C-PAA-Na in the present invention, no adhesive is used. Instead, Ag nanoparticles are deposited by evaporation of Ag atoms, such as Ag atoms emitted from the Ag deposition source, colliding with the surface of the granular C-PAA-Na in a vacuum containing an inert gas. As the precipitated particles aggregate, a force acts to reduce their surface energy, forming spheres with the smallest surface area for the same volume, and the Ag nanoparticles adhere to the granular C-PAA-Na. This phenomenon has also been reported as a mechanism for the generation of metal nanoparticles on glass substrates by sputtering or other methods (Non-Patent Document 20).

[0041] This suggests that the Ag nanoparticle surface is not oxidized and contacts the granular C-PAA-Na surface as pure Ag nanoparticles, and therefore physical and chemical bonding forces contribute little to the adhesion between them. Therefore, it is speculated that the surface energy and solid state of the granular C-PAA-Na surface are closely related during the process from the collision of the Ag evaporated material with the granular C-PAA-Na to the generation of nanoparticles.

[0042] The surface state of this granular C-PAA-Na is considered to be clean, in a vacuum containing an inert gas, and therefore its molecular mobility is thought to be related to the temperature change. Therefore, by reviewing the molecular motion and state changes associated with increasing temperature of resins, resins are viscoelastic, possessing both viscosity and elasticity. The polymers that make up resins undergo active molecular motion with increasing temperature, transitioning from a glassy state through Tg to a rubbery state, and then from the rubbery state through Tm to a fluid state. Tg is considered the temperature at which segmental motion, which does not shift the center of gravity of the polymer, is released, and Tm is considered the temperature at which free polymer motion is released, transforming the solid into a liquid. Furthermore, HDT is the temperature at which a resin deforms when external stress is applied in the rubbery state, and is thought to indicate the difference in the state of the resin in the rubbery state. Furthermore, dynamic viscoelasticity measurements reveal β-dispersion and γ-dispersion, which are thought to be highly localized molecular motions of polymers in the glassy state, such as the movement of polymer side chains and the rotational motion of the polymer main chain (according to this designation, Tg corresponds to α-dispersion).

[0043] Thus, based on the generation process of Ag nanoparticles on the C-PAA-Na particles, the state change accompanying the release of polymer molecular motion as the resin temperature rises, and the results of experiments with different deposition ambient temperatures, it is reasonable to assume that the more active the segmental motion on the surface of the C-PAA-Na particles at the deposition ambient temperature, the stronger the binding strength of the Ag nanoparticles to the C-PAA-Na particles, and the stronger the adhesion of the Ag nanoparticles to the C-PAA-Na particles. It is also inferred that the anchoring effect of the Ag nanoparticles, as if they are buried in the C-PAA-Na particles, contributes significantly to the binding strength.

[0044] The surface energy of a resin is an indicator of the hydrophilicity and hydrophobicity of the resin in terms of its wettability, and is known to affect the bonding strength between different materials. Indeed, experimental results using resins with different surface energies have shown that the adhesion strength between Ag nanoparticles and these granular resins is low in the case of fluororesins and silicone-based resins, so this is an important factor. However, because the deposition and the deposited material are fixed and no surface treatment is performed during the Ag nanoparticle production process, the effect on the surface energy of the granular C-PAA-Na is a slight change in surface energy that depends on the deposition ambient temperature. This effect is extremely limited, and this effect is considered to be included in the control of the deposition ambient temperature.

[0045] Therefore, to obtain an appropriate adhesive strength by physical vapor deposition of Ag onto granular C-PAA-Na, the deposition ambient temperature is preferably 50 to 130°C. Depending on the application of the Ag nanoparticle-supported highly water-absorbent C-PAA-Na, the adhesive strength can be controlled by setting the deposition ambient temperature in the range of 50 to 130°C, and the higher the deposition ambient temperature, the more improved the adhesive strength. This is supported by the fact that the HDT is within the range between Tg and Tm, the smaller the measurement load, the higher the HDT, and the more active the molecular motion in the rubber region becomes at higher temperatures.

[0046] Next, we will discuss another deposition condition, the continuous deposition time. As noted in Patent Document 12, the continuous deposition time is an important factor for generating metal nanoparticles. The continuous deposition time, which determines the time the substrate is exposed to the deposition source, affects the particle size of the generated metal nanoparticles and the surface temperature of the substrate. Therefore, the shorter the continuous deposition time, the smaller the particle size of the Ag nanoparticles. Given the same binding strength between the Ag nanoparticles and the granular C-PAA-Na per unit area, the Ag nanoparticles are less likely to detach. This also suppresses the temperature rise of the granular C-PAA-Na substrate, thereby reducing the binding strength between the Ag nanoparticles and the granular C-PAA-Na. The smaller the particle size of the Ag nanoparticles, the larger their specific surface area, which increases in proportion to the square of the particle size. This significantly affects the elution of Ag ions, i.e., their antibacterial effect.

[0047] The continuous deposition time may also have a similar effect. However, experiments were conducted with the deposition ambient temperature held constant and the continuous deposition time as a parameter to determine the optimal continuous deposition time for generating an adequate adhesive force between the Ag nanoparticles and the C-PAA-Na particles. The results indicated that a range of 0.05 to 0.2 seconds is preferable. Furthermore, the longer the continuous deposition time, the stronger the bonding strength between the Ag nanoparticles and the C-PAA-Na particles. This is likely related to the temperature rise on the surface of the deposition target due to exposure to the deposition source.

[0048] In this way, we have used a metal as the deposition source and granular resin as the deposition target, and have explained the adhesive force between the metal nanoparticles generated by physical vapor deposition and the granular resin using Ag and C-PAA-Na, but the factors that determine this are unclear. Therefore, it is necessary to experimentally determine the conditions that fix the metal and resin used and generate an appropriate adhesive force.

[0049] The same applies to the particle size and adhesion amount of Ag nanoparticles supported on granular C-PAA-Na. The average particle size of Ag nanoparticles generated on granular C-PAA-Na by physical vapor deposition depends on the cumulative deposition time of continuous deposition, but is preferably controlled to approximately 1 to 50 nm. According to the technical characteristics of nanotechnology, the antibacterial effect of antibacterial metal nanoparticles is thought to increase with their specific surface area, and a smaller average particle size is preferable. However, in order for Ag nanoparticles to be generated on the surface of granular C-PAA-Na and supported on the granular C-PAA-Na with appropriate adhesive strength, as in the present invention, it is necessary to not only rely on the specific surface area but also to have an appropriate adhesive strength due to an appropriate anchoring effect, and to prevent a decrease in the specific surface area by uniformly dispersing the Ag nanoparticles on the granular C-PAA-Na. From these perspectives, the average particle size of Ag nanoparticles is preferably approximately 1 to 50 nm, more preferably approximately 5 to 50 nm, and even more preferably approximately 10 to 50 nm. Furthermore, the amount of Ag nanoparticles attached to the granular C-PAA-Na by physical vapor deposition also depends on the deposition time obtained by accumulating the continuous deposition time, but it is preferable that they are uniformly dispersed on the surface of the granular C-PAA-Na.It is preferable to control the amount of Ag nanoparticles attached to the granular PLA so that it is approximately 0.005 to 0.5 wt%, more preferably approximately 0.01 to 0.5 wt%, and even more preferably approximately 0.02 to 0.5 wt%.

[0050] The above explanation also applies to the granular superabsorbent resin carrying antibacterial Ag nanoparticles produced by physical vapor deposition using Ag as the deposition source and granular C-CMC-Na as the deposition target.

[0051] More importantly, the Ag nanoparticle-supported granular C-PAA-Na, which possesses optimal antibacterial properties and water absorption and retention capabilities, should be defined by the adhesive force between the Ag nanoparticles and the granular C-PAA-Na. However, no technology exists to measure adhesive force. In other words, the Ag nanoparticle-supported granular C-PAA-Na, a granular resin possessing both antibacterial properties and water absorption and retention capabilities, is a product invention that should be directly identified by its special technical feature, the adhesive force between the Ag nanoparticles and the granular PLA. However, this identification was impossible at the time of filing, and identifying the Ag nanoparticles would require significant technological development effort, which would be inconsistent with the first-to-file system and highly impractical. Therefore, the present invention is defined as a product invention manufactured under specified conditions. The same applies below.

[0052] The C-PAA-Na that can be used in the present invention is not particularly limited, and generally available products can be used, with industrially produced products being more preferable. For example, C-PAA-Na such as Sunfresh (registered trademark) manufactured by Sanyo Chemical Industries, Ltd., Sunwet (registered trademark) manufactured by SDP Global Co., Ltd., AQUAKEEP (registered trademark) manufactured by Sumitomo Seika Chemicals Co., Ltd., AQUALIC (registered trademark) and ACRYHOPE (registered trademark) manufactured by Nippon Shokubai Co., Ltd., and Hysorb (registered trademark) manufactured by BASF Japan Ltd. can be used as the granular deposition target, and is not particularly limited.

[0053] As for the shape and size, if the particles are granular and have a maximum length of approximately 0.1 to 30 mm, this does not pose a significant problem for physical vapor deposition of Ag or for subsequent commercialization. However, if the size is less than 0.1 mm or exceeds 30 mm, physical vapor deposition is performed while stirring the powdered resin, as described below, which can cause manufacturing problems such as scattering and recovery. A particularly easy-to-handle size for granular resin is approximately 3 to 5 mm. Furthermore, granular water-absorbent resin of a desired size can be prepared by crushing or crushing the resin raw material using a general single- or double-screw resin crusher or resin pulverizer. To achieve uniform particle size, a resin pulverizer is preferred. Furthermore, classification is even more preferred to achieve uniform particle size and enhance antibacterial properties and water absorption / retention properties.

[0054] Secondly, the present invention provides a granular superabsorbent resin with antibacterial properties, characterized in that physical vapor deposition is carried out using Ag as the vapor deposition source and granular C-CMC-Na as the substrate, controlling the vapor deposition atmosphere temperature in the range of 70 to 180°C while controlling the vapor deposition time for continuous vapor deposition in the range of 0.05 to 0.2 seconds, so that vaporized substances from the Ag intermittently reach the surface of the granular C-CMC-Na, generating Ag nanoparticles on the surface of the granular C-CMC-Na, and these Ag nanoparticles are supported on the surface of the granular C-CMC-Na with appropriate adhesive force.

[0055] The granular C-CMC-Na is not particularly limited, and any commonly available product can be used, with industrially produced products being more preferable. For example, Gelfine (registered trademark) manufactured by Daicel Miraizu Co., Ltd. can be used. The size of the granular C-CMC-Na is the same as that of the granular C-PAA-Na, and therefore a detailed description thereof will be omitted.

[0056] The Ag nanoparticle-supported C-PAA-Na and Ag nanoparticle-supported granular C-CMC-Na of the present invention can be widely used in daily necessities that require water absorption and water retention, such as highly absorbent cloths for infants, children, the elderly, and pets, disposable diapers, sanitary napkins, and air fresheners. They are particularly suitable for hygiene products such as disposable diapers and sanitary napkins.

[0057] Furthermore, the Ag nanoparticle-loaded C-PAA-Na and Ag nanoparticle-loaded granular C-CMC-Na of the present invention can be used as a soil water-retaining material or soil improvement material for afforestation to prevent desertification, greening trees, lawn creation, and gardening, etc. [Effects of the Invention]

[0058] The present invention will contribute to the realization of a circular society that embraces natural and social environments and prevents desertification, which is increasing due to global warming and the resulting climate change, and will also contribute to the achievement of the SDGs by being used as an absorbent material in disposable diapers and sanitary napkins used to treat the excrement of infants, children, the elderly, the sick, etc., thereby realizing a hygienic and healthy lifestyle that prevents the proliferation of microorganisms and bad odors.

[0059] More specifically, the granular water-absorbent C-PAA-Na and Ag nanoparticle-loaded granular C-CMC-Na of the present invention can be used not only as soil water-retaining materials and soil conditioners for afforestation, greening, lawn creation, and gardening to prevent desertification, but also as a wide range of daily necessities such as sanitary products such as disposable diapers and sanitary napkins, thereby contributing to the protection of the natural environment and supporting hygienic and healthy lifestyles. [Brief explanation of the drawings]

[0060] [Figure 1] The figures show literature values of the thermal properties of various synthetic resins used as indicators for setting the deposition temperature and continuous deposition time when producing the Ag nanoparticle-supported granular C-PAA-Na of the present invention. [Figure 2] FIG. 1 is a schematic diagram of an ion plating apparatus for producing granular C-PAA-Na supported with Ag nanoparticles by physical vapor deposition according to one embodiment of the present invention. [Figure 3] This is a schematic diagram showing the Ag nanoparticle generation mechanism to explain that in granular C-PAA-Na on which Ag nanoparticles are supported by physical vapor deposition, according to one embodiment of the present invention, the Ag nanoparticles and granular C-PAA-Na are supported with moderate adhesive force. [Figure 4] FIG. 1 is a schematic diagram illustrating the application of granular C-PAA-Na, on which Ag nanoparticles are supported by physical vapor deposition, to a reforestation project as a practical example, according to one embodiment of the present invention. [Figure 5] FIG. 1 is a schematic diagram showing the application of granular C-PAA-Na, on which Ag nanoparticles are supported by physical vapor deposition, to a highly absorbent wipe, as a practical example according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0061] The present invention will be described in more detail below using the embodiments shown in the drawings, with the intention of clarifying its technical concept. However, the present invention is not limited to these embodiments, and can be implemented in various modifications within the scope of the present invention, and is limited only by the technical concept described in the claims.

[0062] Figure 1 shows the thermal properties of general-purpose plastics and the C-PAA-Na used in this invention, as well as the deposition ambient temperature and continuous deposition time as preferred deposition conditions for physical vapor deposition of antibacterial metals. For general-purpose plastics, the deposition conditions are for granular general-purpose plastics containing various metals other than Ag as the deposition source. For SAP, the deposition conditions are for granular C-PAA-Na and granular C-CMC-Na using Ag as the deposition source. For reference, the thermal properties of uncrosslinked PAA-Na before C-PAA-Na is produced and CMC-Na before C-CMC-Na is produced are also shown. While this figure does not clearly explain the correlation between the deposition conditions and granular C-PAA-Na and granular C-PAA-Na, it suggests that a deposition ambient temperature in the temperature range from the glassy to rubbery state of granular C-PAA-Na and granular C-PAA-Na generates an appropriate adhesive force between Ag nanoparticles and granular C-PAA-Na and granular C-PAA-Na. In practice, it is necessary to set deposition conditions according to the application.

[0063] In one embodiment of the present invention, granular C-PAA-Na with an average particle size of 1 mm was used as the substrate, and Ag was used as the deposition source. Physical vapor deposition was performed using the ion plating apparatus shown in Figure 2 under deposition conditions of a deposition atmosphere temperature of 100°C, a continuous deposition time of 0.1 sec, and a total deposition time of 18 minutes, generating 300 ppm (0.03 wt%) of Ag nanoparticles on the surface of the granular C-PAA-Na, producing Ag nanoparticle-loaded granular C-PAA-Na that exhibits excellent antibacterial and water absorption / retention properties.

[0064] The ion plating apparatus shown in Figure 2 includes a deposition chamber 101 equipped with at least an ion source 102, an Ag deposition source 103 (antibacterial metal), an inert gas introduction system 108, and a vacuum exhaust system 109. A shutter 104 with a slit 105, precisely rotated by a rotary motor 106, is installed between the Ag deposition source 103 and granular C-PAA-Na 110 (a deposition target on which Ag deposition material 107 is deposited), located below the Ag deposition source 103. The Ag deposition material 107 ejected from the Ag deposition source 103 by the ion source 102 is intermittently deposited on the surface of the granular C-PAA-Na 110. Furthermore, the granular C-PAA-Na 110 is agitated by a screw 111 connected to a stirring motor 112 at the bottom of the production apparatus to ensure uniform exposure of the Ag deposition material 107. This agitation circulates the granular C-PAA-Na 110 along its travel path 114. Specifically, the granular C-PAA-Na110-1 at the bottom of the manufacturing equipment is lifted up to the granular C-PAA-Na110-2, and then intermittently deposited on the granular C-PAA-Na110-3, where the Ag nano-evaporation material 107 adheres. This then leads to the granular C-PAA-Na110-4, which is not exposed to the evaporation source for a certain period of time. While FIG. 2 illustrates intermittent deposition using a shutter mechanism, this is not necessarily a shutter mechanism. Any mechanism can be used as long as it can accurately release the Ag evaporation material onto the granular C-PAA-Na110 and control the time the granular C-PAA-Na110 is exposed to the Ag evaporation material 107. For example, a method of directly controlling the ion beam emitted from the ion source 102 can be used. The temperature of the entire evaporation chamber 101 is controlled by a temperature control device 113.

[0065] The mechanism by which Ag nanoparticles are generated on the surface of the granular C-PAA-Na to be deposited is unclear, but is speculated as follows (Non-Patent Document 20). A typical film formation mechanism, such as deposition or sputtering, is called Volmer-Weber (VW) growth. This is an island growth process in which numerous three-dimensional island-like nuclei are formed from the initial stage of growth, and as the deposition amount increases, these nuclei grow and coalesce, eventually forming a continuous film. The above-mentioned ion plating apparatus was modified to focus on the initial stage of VW growth film formation, controlling the continuous deposition time for the deposition material to be continuously deposited on the granular C-PAA-Na to at least 0.2 seconds or less, and enabling deposition while stirring the granular C-PAA-Na, so that new surfaces of the granular C-PAA-Na are always exposed to the Ag deposition material. With this modified ion plating apparatus, the continuous deposition time is short, so a continuous Ag film is not formed, and only a three-dimensional sea-island structure, i.e., Ag nanoparticles, are formed one after another on the surface of the granular C-PAA-Na110.

[0066] More specifically, granular C-PAA-Na110 with an average particle diameter of 1 mm is placed in the production vapor deposition chamber 101, and the Ag vapor deposition source 103 is installed. Next, the degree of vacuum in the vapor deposition chamber 101 is adjusted to 1×10 -4While evacuating the chamber 101 through the vacuum exhaust system 109 to a pressure of about 1 torr, inert gas Ar is introduced into the chamber 101 through the inert gas introduction system 108. Once the vacuum level is stabilized, the rotation motor 106 and the stirring motor 102 rotate the shutter 104 and the screw 111 to evaporate the Ag vapor material from the Ag vapor deposition source 103 at a rate of 1 Å to 10 μm / min per unit area until the Ag vapor concentration relative to the C-PAA-Na granules reaches 300 ppm, producing Ag nanoparticles on the C-PAA-Na granules. This evaporation rate was determined in advance through a preliminary experiment using a conventional gravimetric method for evaporation on a fixed flat substrate. The deposition conditions for such Ag nanoparticles are as follows: the deposition atmosphere temperature in the chamber 101 is set to 100°C using the temperature control device 113; and the rotation speed of the shutter 104 is set according to the shape of the slit 105 so that the Ag vapor material 107 is continuously deposited on the C-PAA-Na granules for a continuous deposition time of about 0.1 seconds.

[0067] Figure 3 is a schematic diagram illustrating the Ag nanoparticle formation mechanism, explaining how the Ag nanoparticles and granular C-PAA-Na nanoparticles are supported with adequate adhesion in the Ag nanoparticle-supported granular C-PAA-Na nanoparticles produced in this manner. Because the granular C-PAA-Na is agitated, Ag vaporized material, such as Ag atoms emitted from the Ag vapor deposition source, adheres uniformly to the surface of the granular C-PAA-Na nanoparticles, forming numerous island-like nuclei. These nuclei grow with increasing deposition volume, producing Ag nanoparticles. The deposition ambient temperature was set to 100 °C, which allows for the release of polymer segmental motion near the Tg of the granular C-PAA-Na nanoparticles. When the Ag vaporized material collided with the outermost surface of the PLA pellet, the outermost surface of the granular C-PAA-Na nanoparticles became depressed, and then grew into Ag nanoparticles. This anchoring effect is thought to be responsible for the adequate adhesion between the Ag nanoparticles and the granular C-PAA-Na nanoparticles. Furthermore, because the continuous deposition time is controlled, the temperature of the PLA pellet surface does not rise above the deposition ambient temperature, which is thought to prevent the adhesion from becoming too strong. Controlling the continuous deposition time is likely to prevent the Ag nanoparticles from growing into a film and contribute to the production of Ag nanoparticles with a uniform particle size.

[0068] The Ag nanoparticle-loaded granular C-PAA-Na produced in this manner is used, for example, as a soil water-retaining material and soil conditioner in afforestation projects, as shown in Figure 4. The Ag nanoparticle-loaded granular C-PAA-Na of the present invention can be sprayed away from trees, so it does not expand and inhibit the rooting and growth of planted plants. It can also provide sustained antibacterial protection against microorganisms that hinder the rooting and growth of planted plants over a long period of time. Furthermore, the Ag nanoparticles released after a predetermined time safely protect the entire planted area against microorganisms that are harmful to plant growth. Furthermore, such release does not cause decomposition of the granular C-PAA-Na by Ag ions, so the water-retaining function of the granular C-PAA-Na is not deteriorated. In such applications, it is preferable to use biodegradable Ag-loaded granular C-CMC-Na.

[0069] Figure 5 shows an example of the use of the Ag nanoparticle-loaded granular C-PAA-Na of the present invention in a highly absorbent dustcloth. Even if the Ag nanoparticles are detached from the granular C-PAA-Na, the antibacterial function of the Ag nanoparticles is maintained, resulting in a long-term antibacterial function. Furthermore, this detachment prevents the decomposition of the granular C-PAA-Na by Ag ions, so its absorbency is not impaired.

[0070] These are just some examples of applications in which the Ag nanoparticle-loaded granular C-PAA-Na and Ag-loaded granular C-CMC-Na of the present invention can be used, and it is expected that there will be a wide range of applications in which antibacterial properties, water absorption, and water retention are required. [Industrial Applicability]

[0071] The Ag nanoparticle-loaded granular C-PAA-Na and Ag-loaded granular C-CMC-Na of the present invention are resin materials that combine antibacterial functions with water absorption and retention functions, which can contribute to achieving the SDGs, which are a global challenge in modern society, and are considered to have extremely high industrial applicability. [Explanation of symbols]

[0072] 100 Ion plating equipment 101 Vapor deposition tank 102 Ion Source 103 Ag deposition source 104 Shutter 105 Slit 106 Rotational Motor 107 Ag deposition material 108 Inert gas introduction system 109 Vacuum exhaust system 110 Granular C-PAA-Na 111 Screw 112 Stirring motor 113 Temperature Control Device 114 Migration path of granular C-PAA-Na 200 Ag nanoparticle-loaded granular C-PAA-Na 300 forest plantations 400 Highly absorbent cloth 410 mesh 420 Liquid-proof film 430 Cotton Pulp

Claims

1. physical vapor deposition is carried out using silver as a vapor deposition source and a granular crosslinked sodium polyacrylate as a substrate, while controlling the vapor deposition atmosphere temperature in the range of 50 to 130°C and simultaneously controlling the vapor deposition time for continuous vapor deposition in the range of 0.05 to 0.2 seconds; A granular highly absorbent resin with antibacterial properties, characterized in that evaporated substances from the silver intermittently reach the surface of the granular crosslinked sodium polyacrylate, producing silver nanoparticles on the surface of the granular crosslinked sodium polyacrylate, and the silver nanoparticles are supported on the surface of the granular crosslinked sodium polyacrylate with an appropriate adhesive force.

2. physical vapor deposition is carried out using silver as a vapor deposition source and granular crosslinked carboxymethyl cellulose as a substrate, while controlling the vapor deposition atmosphere temperature in the range of 70 to 180°C and simultaneously controlling the vapor deposition time for continuous vapor deposition in the range of 0.05 to 0.2 seconds; A granular highly absorbent resin with antibacterial properties, characterized in that evaporated substances from the silver intermittently reach the surface of the granular crosslinked carboxymethyl cellulose, generating silver nanoparticles on the surface of the granular crosslinked carboxymethyl cellulose, and the silver nanoparticles are supported on the surface of the granular crosslinked carboxymethyl cellulose with moderate adhesion.

3. 3. A water-absorbing daily necessity, comprising the granular highly water-absorbent polymer according to claim 1 or 2.

4. A disposable diaper or sanitary napkin, characterized by using the granular highly absorbent polymer according to claim 1 or 2.

5. A soil water-retaining material comprising the granular highly water-absorbent polymer according to claim 1 or 2.

6. A soil improvement material comprising the granular highly water-absorbent polymer according to claim 1 or 2.

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