JP2013209362A - Antibacterial material containing zinc oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antibacterial material which exerts high antibacterial properties not only in a bright place but also in a dark place.SOLUTION: An antimicrobial material includes (A) zinc oxide and (B) a binder, and has water absorbency.

Description

  The present invention relates to an antibacterial material containing zinc oxide, and more particularly to an antibacterial material that can exhibit high antibacterial properties not only in a light place but also in a dark place.

Titanium oxide (TiO ₂ ) is roughly classified into anatase type (tetragonal), rutile type (tetragonal) and brookite type (orthorhombic) based on the crystal structure. Among these, anatase type titanium oxide and rutile type titanium oxide are used as photocatalysts.

When these titanium oxides are irradiated with ultraviolet rays, electrons in the valence band of titanium oxide are excited to the conduction band, and the electrons are emitted, generating positively charged holes. Since the generated holes have a very strong oxidizing power, they take electrons from OH ⁻ (hydroxide ions) and the like in water to generate OH radicals having a strong oxidizing power. This OH radical exhibits the property of attacking bacteria and viruses.

  An antibacterial material containing titanium oxide has been developed by utilizing such characteristics of titanium oxide. For example, in Patent Document 1, “polytetrafluoroethylene particles and visible light responsive nitrogen-doped titanium oxide photocatalytic particles and perfluoroethylene are dispersed in a fluororesin, an epoxy resin, an acrylic resin, or a silicon resin. “Composite material characterized by realizing super water repellency, antifouling / antibacterial properties and long-term durability” is disclosed (claims).

  However, an antibacterial material containing titanium oxide as a photocatalyst can generate OH radicals in the dark (that is, with little or no UV irradiation), as is apparent from the antibacterial action mechanism of titanium oxide. Inability to exhibit sufficient antibacterial properties.

JP 2007-51263 A

  The present invention solves the problems that cannot be solved by conventional antibacterial materials containing titanium oxide, and provides an antibacterial material that exhibits high antibacterial properties not only in a bright place but also in a dark place. Objective.

As a result of intensive studies, the inventor of the present invention (1) can exhibit a high antibacterial property not only in a bright place but also in a dark place according to an antibacterial material having water absorption using zinc oxide as an antibacterial substance. By setting the Lotgering factor indicating the degree of orientation of the crystal plane a in a single crystal of zinc oxide in the antibacterial material to a specific value, it exhibits extremely high antibacterial properties not only in a bright place but also in a dark place I found a new characteristic. The present invention has been completed based on such knowledge.
The gist of the present invention is as follows.

  [1] An antibacterial material containing zinc oxide (A) and a binder (B) and having water absorption.

  [2] The antibacterial material according to [1], wherein the binder (B) is an organic polymer having radical resistance.

  [3] The antibacterial material according to [2], wherein the organic polymer having radical resistance is a fluorine-containing polymer.

[4] The surface of the antibacterial material has an X-ray diffraction pattern having a diffraction peak (100) on the (100) plane and a diffraction peak (200) on the (200) plane as the diffraction peak of zinc oxide (A). ,
The Lotgering factor calculated using the diffraction intensity I (100) of the diffraction peak (100) and the diffraction intensity I (200) of the diffraction peak (200) is 0.1 or less [1] to [ 3] The antibacterial material according to any one of the above.

  According to the antibacterial material of the present invention, high antibacterial properties can be exhibited not only in a bright place (under light irradiation conditions) but also in a dark place (that is, under conditions where there is little or no ultraviolet irradiation).

FIG. 1A shows the X-ray diffraction patterns of the surfaces of the test pieces obtained in Example 1 and Comparative Example 1. FIG. 1B shows an electron micrograph of the surface of the test piece obtained in Example 1 and Comparative Example 1. FIG. 2 is a Time-CL curve showing the relationship between the amount of chemiluminescence (CL, vertical axis) and time (Time, horizontal axis) in the test pieces obtained in Examples 1-2 and Comparative Examples 1-3. .

Hereinafter, the antibacterial material of the present invention will be described in detail.
The antibacterial material of the present invention contains zinc oxide (A) and a binder (B) as essential components, and may contain optional components such as a water absorbing material, a crosslinking agent, a plasticizer, and various functional fillers as necessary. Good.

Moreover, the antibacterial material of the present invention has water absorption.
When the antibacterial material of the present invention contains zinc oxide (A) and the binder (B) and has water absorption, an antibacterial material having high antibacterial activity can be obtained.
As such an antibacterial material, the time until specular reflection due to water droplets is not observed, measured by a dropping method in accordance with JIS L 1907, is preferably 60 seconds or less, more preferably 30 seconds or less. Antibacterial materials are desirable.

  Antibacterial materials having water absorption include, for example, (i) a method of blending a water absorbing material when stirring and mixing zinc oxide (A) and binder (B), and (ii) antibacterial using a hydrophilized binder. A method for producing the material, (iii) a method in which zinc oxide (A) and binder (B) are stirred and mixed and molded, and then the surface of the resulting molded body is hydrophilized, and (iv) the antibacterial material is made porous. It can be obtained by a method such as a quality structure method. Among these, it is preferable to use a water-absorbing material from the viewpoint that an antibacterial material having water absorption can be easily obtained at low cost. In this case, for example, an antibacterial material having water absorption in the above range can be obtained by adjusting the blending amounts of zinc oxide (A), binder (B) and water absorbing material.

  From the viewpoint that the antibacterial activity can be significantly improved under bright and dark places, the X-ray diffraction pattern of the surface of the antibacterial material is the diffraction peak of (100) plane as the diffraction peak of zinc oxide (A) (100) And a diffraction peak I (100) of the diffraction peak (100) and a diffraction intensity I (200) of the diffraction peak (200). Lotgering factor (degree of orientation of the single crystal a plane of zinc oxide) is preferably 0.1 or less, more preferably 0.08 or less (for example, 0.01 to 0.08), and still more preferably Is 0.05 or less (for example, 0.01 to 0.05).

  Whether or not the X-ray diffraction pattern on the surface of the antibacterial material has peaks such as the diffraction peak (100) and the diffraction peak (200), and the diffraction intensity thereof is determined by the X-ray diffraction conditions described in Examples below. It can be judged from the X diffraction pattern of the surface of the antibacterial material obtained based on the above.

  When the single crystal structure of zinc oxide has a wurtzite structure (hexagonal crystal), the X-ray diffraction pattern of the zinc oxide powder usually has (100) planes in order of increasing horizontal axis “2θ”. It has peaks of (002) plane, (101) plane, (102) plane, (110) plane, (103) plane, (200) plane, (112) plane, and (201) plane. Here, the peaks of the (100) plane and the (200) plane indicate a single crystal a plane (plane perpendicular to the a axis) of zinc oxide.

  For example, as disclosed in Japanese Patent Application Laid-Open No. 2006-264316 and the like, the Lotgering factor (f) is calculated based on the following formula (1). When the value of f is “1”, it indicates that zinc oxide is completely oriented in the a-axis direction, and when it is “0”, zinc oxide is not oriented in the a-axis direction ( Non-oriented).

  In the formula (1), ρ is calculated by the following formula (2) from the diffraction pattern on the surface of the antibacterial material.

ρ ₀ is calculated by the following equation (3) from the X-ray diffraction pattern of the zinc oxide powder used for the antibacterial material.

  The shape of the antibacterial material of the present invention is appropriately selected according to the purpose of use of the antibacterial material, and examples thereof include a fiber shape, a plate shape, a particle shape, and a tetrapod shape.

  The antibacterial material of the present invention may be used in bright places (under light irradiation conditions) such as outdoor building materials and industrial members, but it can exhibit antibacterial properties even under conditions with little or no ultraviolet irradiation. It can be suitably used even under conditions where there is little or no UV irradiation, such as building materials for containers, members in containers, members for water, members for electronic devices, and medical members.

<Zinc oxide (A)>
The antibacterial material of the present invention contains zinc oxide (A) as an antibacterial component, but zinc oxide (A) is not particularly limited. That is, the zinc oxide (A) may be commercially available, for example, heated by vaporizing metal zinc and combusted in air, or prepared by heating zinc sulfate or zinc nitrate. It may be what was done.
Zinc oxide (A) may be used alone or in combination of two or more.

  Examples of commercially available zinc oxide (A) include “1 type zinc oxide”, “2 type zinc oxide”, “3 type zinc oxide” classified by JIS K-1410, and the Japanese Pharmacopoeia. And anisotropy (columnar, plate-like, tetrapot-like) zinc oxide (zinc oxide having shape anisotropy) prepared through a hydrothermal synthesis process. These zinc oxides can be purchased from Sakai Chemical Co., Ltd., Hakusui Tech Co., Ltd. or Sumitomo Osaka Cement Co., Ltd., for example.

  Among them, zinc oxide (A) is preferably zinc oxide having shape anisotropy, particularly columnar zinc oxide, from the viewpoint of having high antibacterial activity as zinc oxide and being capable of controlling orientation. .

  In the antibacterial material of the present invention, the blending amount (volume part) of zinc oxide (A) is preferably with respect to 100 parts by volume of the binder (B) in view of the antibacterial activity exerted in a bright place and a dark place. Is 1 to 1000 parts by volume, more preferably 5 to 500 parts by volume, and still more preferably 10 to 300 parts by volume. It is preferable that the blending amount of zinc oxide (A) is in the above range because an antibacterial material that exhibits better antibacterial activity in light and dark places and is excellent in durability with less dust fall off is preferable. .

<Binder (B)>
The binder (B) is not particularly limited as long as it can hold (bind) zinc oxide (A), and may be an organic polymer or an inorganic polymer. The antibacterial material of the present invention It is appropriately selected according to the use.
A binder (B) may be used individually by 1 type, and may use 2 or more types together.

Examples of the organic polymer include:
Thermosetting resins such as phenolic resin, epoxy resin, melamine resin, urea resin, unsaturated polyester resin, alkyd resin, polyurethane, thermosetting polyimide;
Olefin resins (polyethylene (eg, high density polyethylene (HDPE), medium density polyethylene (MDPE), low density polyethylene (LDPE)), polypropylene, etc.), polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl acetate, fluorine-containing Thermoplastic resins such as polymers (fluorine resins), ABS resins (acrylonitrile butadiene styrene resins), acrylic resins (polymethacrylates, polyacrylates, etc.), polyamide resins;
Natural or natural rubber, acrylic rubber, nitrile rubber, isoprene rubber, urethane rubber, ethylene propylene rubber, chlorosulfonated polyethylene, epichlorohydrin rubber, chloroprene rubber, silicone rubber, styrene-butadiene rubber, butadiene rubber, fluorine rubber, polyisobutylene, etc. Synthetic rubber;
Is mentioned.

  Examples of the inorganic binder include polyborosiloxane, polycarbosilane, polysilastyrene, polysilazane, polytitanocarbosilane, and polysiloxane (including silicone rubber).

  In the antibacterial material of the present invention, reactive oxygen species (radicals) are generated by the action of zinc oxide (A), but the generated radicals deteriorate the binder (B), resulting in deterioration of the antibacterial material (for example, the service life). Decrease, zinc oxide powder falling), etc. may occur. Therefore, it is preferable that the binder (B) has radical resistance. Among these, from the viewpoint of particularly good radical resistance, a fluorine-containing polymer (fluorine resin) or fluororubber is preferable.

  Examples of such a fluoropolymer (fluorine-based resin) include polytetrafluoroethylene [PTFE], tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer [PFA], and tetrafluoroethylene-hexafluoropropylene copolymer [FEP]. , Tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer [EPE], poly (chlorotrifluoroethylene) [PCTFE], tetrafluoroethylene-ethylene copolymer [ETFE], low melting point ethylene-tetrafluoroethylene Copolymer, ethylene-chlorotrifluoroethylene copolymer [ECTFE], polyvinylidene fluoride [PVDF], fluoroethylene-vinyl ether copolymer [FEVE], tetrafluoroethylene-par Such as fluorodioxoles copolymer [TFEPD] and the like. Among these fluoropolymers, PTFE, PFA, and FEP are preferred from the viewpoint of extremely good durability, processability, and radical resistance.

<Water absorbing material>
By providing a water-absorbing material to the antibacterial material of the present invention, the antibacterial properties of zinc oxide contained in the material can be effectively and efficiently exhibited.
Examples of the water-absorbing material include silicon particles, water-absorbing polymer particles (polyacrylic acid polymer, polyvinyl alcohol, water-absorbing urethane, etc.), activated carbon, zeolite, and the like. Among these, compounds that are not decomposed by radicals generated from zinc oxide are preferable, and silicon particles, activated carbon, and zeolite are more preferable.
A water absorbing material may be used individually by 1 type, and may use 2 or more types together.

  The water-absorbing material may be appropriately blended within a range that does not impair the properties of zinc oxide, and the blending amount is preferably 1 to 1000 parts by volume, more preferably 5 to 500 parts by volume with respect to 100 parts by volume of the binder. More preferably, it is 10 to 300 parts by volume.

  The antibacterial material of the present invention is manufactured by adding zinc oxide (A) and binder (B), and optionally mixing optional components simultaneously or in any order to known stirring / mixing means, stirring and mixing. can do. Further, after stirring and mixing, a compression molding process may be performed according to the purpose of use. As the compression molding step, the mixture obtained after the stirring and mixing may be put into a mold and compression molded, or roll-rolled. The pressure condition in this compression molding process is not particularly limited.

The Lotgering factor can be controlled by changing pressure conditions in the compression molding process. For example, when zinc oxide (A) is columnar zinc oxide, the Lotgering factor tends to decrease when the applied pressure is decreased. Conversely, when the pressure applied in the compression molding process is increased, the Lotgering factor tends to increase.
For example, when the pressure in the compression molding step is about 1 to 30 kg / cm ² , an antibacterial material having a Lotgering factor of 0.1 or less tends to be obtained.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, the following Example does not limit this invention.

[Example 1]
50 parts by volume of columnar zinc oxide (manufactured by Sakai Chemical Industry Co., Ltd.), 25 parts by volume of FEP (perfluoroethylene-propene copolymer, manufactured by Daikin Industries, Ltd., “NP-20”) and 25 parts by volume of activated carbon as a water absorbing material The mixture was mixed and melt-kneaded for 30 minutes using a Laboplast Mill (Toyo Seiki Seisakusho, “4C150 type”) at 300 ° C. to obtain pellets. The obtained pellets are subjected to a mold (internal dimensions are 55 mm (length) × 55 mm (width) × 0.5 mm (depth)) and heated in the atmosphere at 350 ° C. for 30 minutes. did.
Next, as a compression molding step, a test piece (1) was prepared by compression molding at a pressure of 30 kg / cm ² under air cooling.
In addition, the dimension of the obtained test piece (1) was 50 mm long x 50 mm wide x 0.2 mm thickness, and the weight of the test piece (1) was 1.40 g.

  The prepared test piece (1) was measured for the Lotgering factor, the chemiluminescence amount (antibacterial activity), and the water absorption indicating the degree of orientation of the zinc oxide single crystal a-plane based on the following methods.

[Example 2]
In Example 1, instead of FEP (25 parts by volume) and activated carbon (25 parts by volume), the test piece (2) was prepared in the same manner as in Example 1 except that 45 parts by volume of FEP and 5 parts by volume of activated carbon were used. The lottering factor, chemiluminescence amount and water absorption of the test piece (2) were measured.
In addition, the dimension of the obtained test piece (2) was 50 mm long x 50 mm wide x 0.2 mm thickness, and the weight of the test piece (2) was 1.41 g.

[Comparative Example 1]
A test piece (3) was prepared in the same manner as in Example 1 except that activated carbon was not blended and the amount of FEP used was 50 parts by volume in Example 1, and the Lotgering factor of the test piece (3) was prepared. The amount of chemiluminescence and water absorption were measured.

[Comparative Example 2]
In Comparative Example 1, a test piece (4) was prepared in the same manner as in Comparative Example 1 except that the pressure condition in the compression molding process was changed from “30 kg / cm ² ” to “100 kg / cm ² ”. The Lotgering factor, chemiluminescence amount and water absorption of (4) were measured.

[Comparative Example 3]
In Example 1, a test piece (5) was prepared in the same manner as in Example 1 except that no columnar zinc oxide was added and the amount of FEP and activated carbon used was 50 parts by volume. The amount of chemiluminescence and the water absorption were measured. In addition, since the zinc oxide was not included, the Lotgering factor was not measured.

[Lottgering factor f]
The X-ray diffraction patterns on the surfaces of the test pieces (1) to (4) were measured under the following X-ray diffraction conditions. Among these, the X-ray diffraction patterns on the surfaces of the test pieces (1) and (3) are shown in FIG.
[X-ray diffraction conditions]
X-ray diffractometer: RINT2000 (manufactured by Rigaku)
・ Acceleration voltage: 40 kV
・ Current: 30mA
・ Characteristic X-ray: CuKα ray ・ Scanning speed: 4 degrees / min

The surface index of each peak of the X-ray diffraction patterns on the surfaces of the test pieces (1) to (4) was identified based on the lattice constant of zinc oxide having a wurtzite structure. The height from the baseline to each peak was measured, and the diffraction intensity of each peak was calculated with the diffraction intensity at the peak of the (101) plane being 100. The results are shown in Table 1.
Moreover, the diffraction intensity of each surface of the columnar zinc oxide powder used in preparing the test pieces (1) to (4) was calculated in the same manner as described above. The results are shown in Table 2.

  Note that the lattice constant of the wurtzite-type zinc oxide is X of hexagonal wurtzite-structured zinc oxide powder (non-oriented sample) published by JCPDS-ICDD (Powder Diffraction Standards Committee International Diffraction Data Center). It identified from the line diffraction pattern (No.36-1451).

  From the obtained diffraction intensity, the Lotgering factor f was calculated based on the formula (1). Table 1 shows the values of the Lotgering factor f of the test pieces (1) to (4).

  In addition, the electron micrograph (measuring instrument: Hitachi High-Technologies Corporation S-3400, magnification 5000 times) of the surface of test piece (1) and (3) is shown in FIG.1 (B). As shown in FIG. 1B, it can be seen that the test piece (1) is randomly oriented as compared to the test piece (3).

[Amount of chemiluminescence (antibacterial activity)]
As described below, the chemiluminescence amounts of the test pieces (1) to (5) were measured using the chemiluminescence method. The chemiluminescence amount is an index indicating the amount of reactive oxygen species (hydrogen peroxide) generated from zinc oxide. The larger the chemiluminescence amount, the more active oxygen species attacking fungi. Show. That is, the larger the chemiluminescence value, the higher the antibacterial property.

After leaving each of the test pieces (1) to (5) in a dark place for 300 seconds (5 minutes), a test aqueous solution containing luminol (luminol concentration: 10 ⁻⁶ mol / l) on the surface of each test piece. Was dripped.
Reaction of active oxygen and luminol generated by zinc oxide in 0 to 300 seconds after dropping of the test aqueous solution (that is, 300 to 600 seconds after leaving test pieces (1) to (5) in the dark) Luminescence generated by (luminol reaction) was measured using a chemiluminescence spectrometer (trade name “CLD-100FC” manufactured by Tohoku Electronics Industry Co., Ltd.), and the vertical axis represents chemiluminescence (CL, chemiluminescence) Time-CL curve with the horizontal axis representing time (Time, seconds). The results are shown in FIG.
From the Time-CL curve, the integrated value (chemiluminescence amount (0 to 300)) of the luminescence intensity for 0 to 300 seconds after the test aqueous solution was dropped was calculated. The results are shown in Table 1.

Moreover, antibacterial activity was evaluated based on the following evaluation criteria.
◎: Chemiluminescence amount (0-300) is 500,000 or more ○: Chemiluminescence amount (0-300) is 200,000 or more and less than 500,000 △: Chemiluminescence amount (0-300) is 50,000 or more and less than 200,000 × : Chemiluminescence (0-300) is less than 50,000

[Water absorption]
The water absorption of the test pieces (1) to (5) was measured by a dropping method in accordance with JIS L 1907. Specifically, one drop of water was dropped on each of the test pieces (1) to (5), the dropped water drop was visually observed, and the time until specular reflection by the water drop was not observed was measured. . A test piece having a time required for water absorption of 60 seconds or less was used as an antibacterial material having water absorption.

Claims (4)

  An antibacterial material comprising zinc oxide (A) and a binder (B) and having water absorption.   The antibacterial material according to claim 1, wherein the binder (B) is an organic polymer having radical resistance.   The antimicrobial material according to claim 2, wherein the organic polymer having radical resistance is a fluorine-containing polymer. The X-ray diffraction pattern on the surface of the antibacterial material has (100) plane diffraction peak (100) and (200) plane diffraction peak (200) as the zinc oxide (A) diffraction peak,
The Lotgering factor calculated using the diffraction intensity I (100) of the diffraction peak (100) and the diffraction intensity I (200) of the diffraction peak (200) is 0.1 or less. The antibacterial material as described in any one of.