JPH0545292B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a water-absorbing sheet having antibacterial properties. [Conventional technology] Conventionally, water-absorbing sheets have been made by sandwiching super-absorbent resin between paper or non-woven fabrics, and are used in diapers, sanitary products, drip sheets for food, dew prevention materials, sheets for pet wipes, and agricultural and horticultural materials. However, there are no antibacterial properties. [Problems to be Solved by the Invention] In the above-mentioned conventional technology, when the superabsorbent resin in the sheet absorbs water, mold and bacteria tend to grow on the surface and surroundings of the sheet. For example, when used as a drip sheet for food, mold grows on the surface of the sheet. When used as a dew condensation prevention material, there is a problem in that mold can grow on ceiling panels, wallpaper, fittings, etc. Conventional environmental disinfectants include halogen disinfectants, oxygen disinfectants, surfactants, aldehyde disinfectants, alcohol/phenol disinfectants, epoxide and biguanide disinfectants, but all of these are harmful to the human body. It is harmful. Furthermore, since these are organic compounds, they have poor heat resistance and are volatile, making it impossible to heat-process them. [Means for Solving the Problems] The above problems are solved by the water-absorbing sheet having antibacterial properties of the present invention. The antibacterial water-absorbing sheet of the present invention has a specific surface area of 150 m ² /g or more and a SiO ₂ /g of 14 or less.
_One or more metal ions selected from the group consisting of silver, copper, and zinc are added to A _- type zeolite, Zeolite solid particles exchanged and retained, starch/acrylate graft polymer, carboxymethylcellulose crosslinked product, vinyl alcohol/acrylate copolymer, polyacrylonitrile hydrolyzate, acrylate/acrylamide copolymer One or more superabsorbent resins selected from polymers, acrylate polymers, crosslinked polyacrylates, modified polyvinyl alcohols, or isobutylene/maleic anhydride copolymers are formed into a sandwich-like structure by two membranes. The zeolite-based solid particles and superabsorbent resin are sandwiched and are each independent powder or granule, or are integrated powder and granule, and at least one of the two membranes is water permeable. , the two membranes are bonded together by heat and pressure bonding, the amount of the zeolite solid particles (based on anhydrous zeolite) is 0.01% by weight or more of the maximum water absorption amount of the water absorbing sheet, and the amount of the super absorbent resin is It is an antibacterial water-absorbing sheet with a weight of 0.1 to 200g/ ^m2 . In the present invention, the zeolite that retains metal ions with antibacterial effects through ion exchange (hereinafter sometimes simply referred to as zeolites with antibacterial effects) is the one disclosed in Japanese Patent Application No. 7361/1983. It is. That is, zeolite solid particles having an antibacterial effect are natural or synthetic zeolites made of aluminosilicate that retain one or more types of metal ions having an antibacterial effect in the ion-exchangeable portion. Preferred examples of metal ions with antibacterial effects include silver, copper, zinc, tin, lead, bismuth,
Mention may be made of cadmium, chromium and mercury, preferably silver, copper and zinc. The above-mentioned antibacterial metals can be used alone or in combination. Zeolite is generally an aluminosilicate with a three-dimensionally developed skeleton structure, and is generally xM ₂ /nO・Al ₂ O ₃・based on Al ₂ O ₃
It is expressed as ySiO ₂ zH ₂ O. M represents an ion-exchangeable metal ion, usually a monovalent to divalent metal, and n corresponds to this valence. On the other hand, x and y are the coefficients of metal oxide and silica, respectively, and z
represents the number of water of crystallization. Many types of zeolites are known, differing in their composition ratio, pore diameter, specific surface area, etc. However, the specific surface area of the zeolite solid particles used in the present invention is 150 m ² /g (based on anhydrous zeolite) or more, and the zeolite constituent SiO ₂ /Al ₂ O ₃
The molar ratio should be 14 or less, preferably 11 or less. The solution of water-soluble salts of metals with antibacterial activity, such as silver, copper, and zinc, used in the present invention easily undergoes ion exchange with the zeolite defined in the present invention, so this phenomenon can be utilized to obtain the necessary solutions. It is possible to hold the above metal ions alone or in combination in a zeolite stationary phase, but the zeolite particles holding metal ions must have a specific surface area of 150 m ² /g or more and SiO ₂ /Al ₂ O ₃ molar ratio is
Two conditions must be met: 14 or less. If this is not the case, the object of achieving effective antibacterial action will not be obtained. This is thought to be due to the fact that the absolute amount of metal ions fixed on the zeolite is insufficient in a state where the effect can be exerted.
In other words, this is thought to be due to the physicochemical properties of the zeolite, such as the amount of exchange groups, exchange rate, and accessibility. Therefore, zeolites with a high SiO ₂ /Al ₂ O ₃ molar ratio, known as molecular sieves, are completely unsuitable for the present invention. In addition, in zeolite with a SiO ₂ /Al ₂ O ₃ molar ratio of 14 or less, it is possible to uniformly retain metal ions that have antibacterial activity, and for this reason, it is only by using such zeolite that a sufficient antibacterial effect can be achieved. was found to be obtained. In addition, the acid resistance and alkali resistance of zeolite with a high silica ratio, where the SiO ₂ /Al ₂ O ₃ molar ratio of zeolite exceeds 14, is
The silica content increases as SiO ₂ increases, but its synthesis also takes a long time, and from an economic standpoint, it is not a good idea to use zeolite with such a high silica ratio. The above-mentioned natural or synthetic zeolite with SiO ₂ /Al ₂ O ₃ ≦14 can be used satisfactorily in the fields of application normally considered for the present invention from the viewpoint of acid resistance and alkali resistance, and also from an economical point of view. It is cheap and a good idea. From this point of view as well, the SiO ₂ /Al ₂ O ₃ molar ratio must be 14 or less. As the zeolite material having a SiO ₂ /Al ₂ O ₃ molar ratio of 14 or less used in the present invention, either natural or synthetic zeolite can be used. For example, natural zeolite is analcime (Analcime).
_SiO2 / _Al2O3 =3.6 _{~ 5.6} ), Chabazite: _SiO2 / _Al2O3 =3.2~6.0 and 6.4~
7.6), Clinoptilolite:
SiO ₂ /Al ₂ O ₃ = 8.5 to 10.5), Erionite (Erionite: SiO ₂ / Al ₂ O ₃ = 5.8 to 7.4), Faujasite (Faujasite: SiO ₂ / Al ₂ O ₃ = 4.2 to 4.6),
mordenite: SiO ₂ /Al ₂ O ₃ = 8.34
~10.0), Philipsite:
SiO ₂ /Al ₂ O ₃ =2.6 to 4.4), and the like. These typical natural zeolites are suitable for the present invention. On the other hand, typical synthetic zeolites include A-type zeolite (SiO ₂ /Al ₂ O ₃ = 1.4-2.4),
-type zeolite (SiO ₂ /Al ₂ O ₃ = 2-3), Y-
_These synthetic _zeolites are suitable as _{the zeolite} material of the _present invention _. . Particularly preferred are
Synthetic A-type zeolite, X-type zeolite, Y
- type zeolites, clinoptilolites and synthetic or natural mordenites. The shape of the zeolite is preferably in the form of powder particles, and the particle size may be appropriately selected depending on the application. For example, it can be several microns to several tens of microns, more than several hundred microns, or less than 5 microns, especially less than 2 microns. Metal ions must be retained in the zeolite solid particles through an ion exchange reaction. If it is simply adsorbed or attached without ion exchange, the antibacterial effect and its durability will be insufficient. As a method for retaining metal ions, for example, when various zeolites defined in the present invention are converted to Ag-zeolite of the present invention, when converting Ag-zeolite, a water-soluble silver salt such as silver nitrate is usually used. A solution is used, but care must be taken not to make it too concentrated. For example, when converting A-type or
When using 2MAgNO ₃ ), silver ions replace sodium ions in the solid phase through ion exchange, and at the same time, silver oxides etc. are precipitated in the zeolite solid phase.
This has the disadvantage that the porosity of the zeolite is reduced and the specific surface area is significantly reduced. Furthermore, even if the specific surface area does not decrease significantly, the bactericidal activity decreases due to the presence of silver oxide itself. In order to prevent such excess silver from being deposited on the zeolite phase, it is necessary to maintain the concentration of the silver solution in a more dilute state, for example, below 0.3 MAgNO ₃ . The safest concentration of AgNO ₃ is 0.1M or less. When an AgNO ₃ solution with such a concentration was used, the specific surface area of the Ag-zeolite obtained was almost the same as that of the converted material zeolite, and it was found that the antibacterial effect could be exhibited under optimal conditions. Next, when the zeolites defined in the present invention are converted to Cu-zeolite, the same phenomenon as that for Ag-zeolite described above occurs depending on the concentration of the copper salt used for ion exchange. For example A-type or
When converting -type zeolite (sodium-type) to Cu-zeolite by ion exchange reaction,
When using 1MCuSO ₄ , Cu ²⁺ replaces Na ⁺ in the solid phase, but at the same time, Cu ₃ in the zeolite solid phase
The porosity of zeolite decreases due to the precipitation of basic precipitates such as (SO ₄ )(OH) ₄ , which has the disadvantage that the specific surface area decreases significantly. In order to prevent such excessive copper from being deposited in the zeolite phase, it is preferable to maintain the concentration of the water-soluble copper solution used in a more dilute state, for example, 0.05M or less. When using a _CuSO4 solution with such a concentration, the specific surface area of the Cu-zeolite obtained is almost the same as that of the converted material zeolite,
It was found that it has the advantage of being able to exhibit its antibacterial effect under optimal conditions. It was mentioned that when converting to Ag-zeolite and Cu-zeolite, solids may precipitate on the zeolite solid phase depending on the concentration of salts used for ion exchange, but when converting to Zn-zeolite, the salts used This phenomenon is not observed when the distance is around 2 to 3M. Zn usually used in the present invention
- Zeolite can be easily obtained by using salts at concentrations near the above. When carrying out the ion exchange reaction in a batch method for conversion into the above-mentioned Ag-zeolite, Cu-zeolite and Zn-zeolite, the zeolite material may be immersed in a salt solution having the above-mentioned concentration. In order to increase the metal content in the zeolite material, the number of batch treatments can be increased. On the other hand, when treating a zeolite material by a column method using a salt solution having the above-mentioned concentration, the target metal-
Zeolite is obtained. The amount of metal in the above metal-zeolite (based on anhydrous zeolite) is 30% by weight or less for silver, and the preferred range is 0.001 to 5% by weight.
It is in. On the other hand, for copper and zinc used in the present invention, metal-zeolite (based on anhydrous zeolite)
The amount of copper or zinc therein is up to 35% by weight, with a preferred range of 0.01 to 15% by weight. Silver,
It is also possible to use copper and zinc ions in combination; in this case, the total amount of metal ions may be 35% by weight or less based on the metal-zeolite (based on anhydrous zeolite), and the preferred range is the composition ratio of metal ions. Although it depends on the amount, it is approximately 0.001 to 15% by weight. Further, even if metal ions other than those mentioned above, such as sodium, potassium, calcium, or other metal ions, coexist, the antibacterial effect is not hindered, so the residual or coexistence of these ions is not a problem. The ratio of metals with antibacterial activity to the total amount of zeolite (based on anhydrous zeolite) may be 30% by weight or less for silver, and the preferred range is 0.001 to 30% by weight.
It is 5% by weight. whereas for copper or zinc it is 35
% or less, and the preferred range is 0.01 to 15% by weight
It is. When using silver, copper and zinc ions in combination, the total amount of metal ions is between 0.001 and 15
A weight percent range is preferred. Further, there is no problem with the remaining or coexistence of other metal ions. Content of antibacterial zeolite solid particles holding antibacterial metal ions (based on anhydrous zeolite)
is 0.01% by weight or more of the maximum water absorption amount of the water absorption sheet,
In particular, it is preferably 0.5% by weight or more. The super absorbent resin used in the present invention includes a starch acrylate graft polymer,
Crosslinked carboxymethyl cellulose, vinyl alcohol/acrylate copolymer, polyacrylonitrile hydrolyzate, crosslinked polyacrylate, modified polyvinyl alcohol, acrylate polymer, acrylate/acrylamide copolymer, or isobutylene/maleic anhydride Examples include resins with high water absorption such as acid copolymers. It is also possible to use two or more of the above superabsorbent resins. The amount of superabsorbent resin is preferably within the range of 0.1 to 200 g, particularly preferably within the range of 1 to 50 g per m ² of sheet. The superabsorbent resin is preferably in the form of powder or granules independent of the antibacterial zeolite solid particles, for example, particles with a particle size of 5 to 500μ are mixed with the antibacterial zeolite solid particles in two sheets. Sandwich is applied to the film. Alternatively, it is possible to use a granular body in which a superabsorbent resin is applied to the surface of antibacterial zeolite solid particles by appropriate means such as coating and integrated. In the present invention, as the water-permeable membrane, paper, wet nonwoven fabric, dry nonwoven fabric, cellophane, polyvinyl alcohol, woven film with micropores, etc. can be used. As the water-impermeable membrane, a commonly used synthetic resin film such as polyolefin, polyester, polyamide or the like can be used. Whether one of the two membranes is water-impermeable or both membranes are water-permeable can be arbitrarily selected depending on the field of use of the sheet of the present invention. Each membrane itself can be a collection of membranes, such as a laminate, for example a laminate of paper and perforated polyethylene film. Each membrane can also be a composite of a base fabric coated with, for example, polyvinyl alcohol. In the present invention, the term membrane is used in a meaning that includes the above. The two membranes sandwiching the antibacterial zeolite solid particles and the superabsorbent resin are bonded to each other by appropriate means. Preferably, a film that becomes adhesive when heated is selected, or an adhesive is further used to bond the film by heat and pressure bonding. As the adhesive, ethylene-vinyl acetate copolymer is particularly preferred, and polyethylene and polypropylene can also be used as the adhesive. The two membranes can also be joined together by mechanical means, such as suturing. The present invention provides a hygienically preferable antibacterial water-absorbing sheet that does not allow the growth of mold or bacteria on or around the surface of the sheet that absorbs water. The invention will be further explained below with reference to Examples. The antibacterial zeolite used in the Examples is commercially available as Bacte Killer A350 BN (trademark, manufactured by Sinanen News Ceramics). this is,
It is made by adding 3% by weight of silver and 5% by weight of copper to A-type zeolite by ion exchange, and has a diameter of 5 to 6 μm.
It has an average particle size of Specific surface area is 500~600m2 ^/
g, the SiO ₂ /Al ₂ O ₃ molar ratio is approximately 2. Example: Between two sheets of paper (25 g/m ² ), acrylate- ^based super water absorbent resin (Aquakive 10SH-
P (trademark: Seitetsu Kagaku Kogyo Co., Ltd.), particle size 100 μ, water absorption capacity pure water 500 ml/g, sheep blood 50 ml/g), 10 g, zeolite solid particles carrying antibacterial metal ions, and ethylene as an adhesive. vinyl acetate copolymer
5g was sprayed and heated and pressed using a heated roll at 100°C to obtain an antibacterial water-absorbing sheet. Comparative Example 1 Example 1 was repeated except that the zeolite solid particles carrying antibacterial metals were not used. Comparative Example 2 Example 1 was repeated except that the superabsorbent resin was not used. Antibacterial Property Evaluation Experiment The above three types of sheets were cut into 5 x 5 cm pieces, and after absorbing water, the antibacterial effect was examined. In the experiment, each sheet was sprayed with spores of Bacillus subtilis and Aspergillus niger.
The number of surviving bacteria was measured immediately after spraying and after storage for 7 days at 22°C and 90% relative humidity. The measurements were performed using the following procedure. That is, the bacteria on the surface of each sheet was washed off in 10 ml of sterile water supplemented with 0.1% Tween 80, and the number of viable bacteria in this sterile water was measured using an ordinary agar medium (manufactured by Eiken Chemical Co., Ltd.) in the case of Bacillus subtilis. In the case of black mold, potato dextrose agar medium (Eiken Chemical Co., Ltd.)
The number of viable bacteria adhering to each sheet was calculated using a standard pour plate culture method. The results are shown in the table. Comparative Example 3 The example was repeated except that 5 g of a chlorine-based disinfectant (salt powder, available chlorine 30%) was used instead of the zeolite-based solid particles carrying antibacterial metal ions. In this comparative example, the dry powder had poor heat resistance, so it decomposed during the heat-pressing process and chlorine volatilized, which irritated the nose and was very harmful. In addition, the heating roll was severely corroded and could no longer be reused. Comparative Example 4 Comparative Example 3 was repeated, except that the salsi flour was not used. This experimental procedure is the same as Comparative Example 1, but
This experiment was repeated to correct for errors caused by subtle differences in temperature, humidity, etc. during bacterial culture. Comparative Example 5 Comparative Example 3 was repeated except that the superabsorbent resin was not used. As in Comparative Example 3, the chlorine volatilized and was very harmful, and the heating roll could not be reused. Cut the above three types of sheets into 5 x 5 cm pieces, 10ml
After absorbing water, the antibacterial effect was examined using the same procedure as in the antibacterial evaluation experiment described above. The results are shown in the table.

【table】

[Table] From the above table, it can be seen that the antibacterial water-absorbing sheet of the present invention is of comparative example 1 (without antibacterial zeolite) and comparative example 2.
It can be seen that it has a more pronounced antibacterial effect than the sample (without superabsorbent resin). Furthermore, the sheet of the example has a superior antibacterial effect compared to a sheet containing a chlorine-based disinfectant and a superabsorbent resin.
From Comparative Example 3 and Comparative Examples 4 and 5, it can be seen that the antibacterial effect of the chlorine-based disinfectant is rather significantly reduced by the presence of the superabsorbent resin.

Claims (1)

[Claims] 1 Specific surface area of 150 m ² /g or more and 14 or less
A-type zeolite with SiO ₂ /Al ₂ O ₃ molar ratio,
Zeolite-based solid particles in which one or more metal ions selected from the group consisting of silver, copper, and zinc are ion-exchanged and retained in X-type zeolite, Y-type zeolite, clinoptilolite, or mordenite; Starch/acrylate graft polymer, carboxymethylcellulose crosslinked product, vinyl alcohol/acrylate copolymer, polyacrylonitrile hydrolyzate, acrylate/acrylamide copolymer, acrylate polymer, crosslinked polyacrylic acid One or more superabsorbent resins selected from salt, modified polyvinyl alcohol, or isobutylene/maleic anhydride copolymer are sandwiched between two membranes in a sandwich-like manner, and zeolite solid particles and superabsorbent The resins are each independent powder or granule, or are integrated powder and granule, at least one of the two membranes is water permeable, and the two membranes are bonded to each other by heat compression bonding. Antibacterial water absorption, wherein the amount of the zeolite solid particles (based on anhydrous zeolite) is 0.01% by weight or more of the maximum water absorption amount of the water absorption sheet, and the amount of the superabsorbent resin is 0.1 to 200 g/ ^m2 . sheet.