JPH07133445A - Antimicrobial coating composition - Google Patents

Abstract

PURPOSE:To provide an antimicrobial coating composition containing amorphous calcium phosphate particle supporting antimicrobial metallic ion, having high antimicrobial activity, effective for preventing the color change and useful as a tray for holding a food such as perishable food. CONSTITUTION:The composition contains amorphous calcium phosphate particles supporting antimicrobial metallic ion (e.g. gold and silver). The calcium phosphate particle is preferably granulated in almost spherical form.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antibacterial coating composition used for keeping freshness of food such as fresh food.

[0002]

2. Description of the Related Art Conventionally, environmental pollution has been a problem in homes, hospitals and factories, especially in chemical and food factories, due to mold growth on painted surfaces. Further, since it is highly safe and easy to handle, in the case of water-based paints that have been used extensively in recent years, spoilage due to bacteria or mold has become a problem during the manufacturing process and storage.

Therefore, in order to avoid the above problems, it is known to add various antiseptic / antifungal agents to the coating composition. As such an antiseptic / antifungal agent, an organometallic agent such as an organomercury agent is known, but after the toxicity of the organometallic agent was pointed out, it was used as an antiseptic / antifungal agent as described above. Is an organic chlorine type or organic sulfur type. However, the above antiseptic / antifungal agents cannot be said to satisfy both contradictory properties of low toxicity and effectiveness.

Therefore, as satisfying both of the above characteristics, as disclosed in JP-A-60-202162, a zeolitic solid holding antibacterial metal ions such as silver ions having antibacterial properties. A coating composition containing particles has been proposed.

[0005]

However, in the above-mentioned conventional coating composition, when a coating film is formed and then the coating film is irradiated with sunlight or fluorescent light for a long period of time, it is contained in the coating film. This causes a problem that the solid zeolite particles are easily discolored and the appearance of the coating film is deteriorated.

[0006]

In order to solve the above-mentioned problems, the antibacterial coating composition according to claim 1 of the present invention comprises amorphous calcium phosphate particles carrying antibacterial metal ions. I am trying.

In order to solve the above-mentioned problems, an antibacterial coating composition according to a second aspect of the present invention contains antibacterial metal ions and contains amorphous calcium phosphate particles granulated into a substantially spherical shape. It is characterized by that.

As the antibacterial metal ion, at least one metal selected from gold, silver, zinc, copper, tin, lead, arsenic, platinum, iron, antimony, nickel, aluminum, barium, cadmium, manganese, a mixture thereof, and the like. The metal compounds of and the aqueous solutions thereof can be used.

The amorphous calcium phosphate (Amorphous
Calcium Phosphate: Hereinafter abbreviated as ACP)
To the calcium hydroxide suspension with stirring, 0.1 to 10% by weight, preferably 0.1 to 3% by weight, of a neutral or weakly alkaline water-soluble polymer dispersant, for example, a weakly alkaline ammonium triacrylate salt is added. After the addition to obtain a mixed solution, the above mixed solution with stirring is added dropwise to an aqueous phosphoric acid solution to obtain a slurry whose pH is adjusted to 10 to 5. The above-mentioned slurry contains ACP particles having a particle size of about 0.1 μm or less, in which aggregation of the ACP particles is prevented by adding a water-soluble polymer dispersant.

The above ACP particles were subjected to powder X-ray diffractometry to determine the pattern of calcium phosphate [Ca ₃ (PO ₄ ) ₂
nH ₂ O] and its pattern is broad, confirming that it is amorphous calcium phosphate. Moreover, the ACP particles are considered to be an electrostatically active substance because they contain water of crystallization, and it is presumed that various ACF particles and viruses are easily adsorbed.

The ACP particles adsorbing the antibacterial metal ions are mixed with the antibacterial metal ions in the slurry so that the solid content is 50% by weight or less, and the calcium ions of the ACP particles are antibacterial by ion exchange or the like. It is formed by substituting a metallic metal ion.

The slurry containing ACP particles adsorbing the antibacterial metal ions as described above may be granulated into a substantially spherical shape by a spray drying granulation method or the like. By granulating in this way, the particle size can be increased and handling becomes easier, deterioration of slip of the coating composition can be avoided when added to the coating composition, and a uniform coating film can be formed. Such ACP particles preferably have a particle size of 0.1 μm or less so that the obtained antibacterial particles have a large specific surface area and the antibacterial metal ions are efficiently replaced.

When the antibacterial metal ions are added to the above slurry in the form of metal powder or metal compound powder,
The particle size of the metal powder or metal compound powder is preferably 20 μm or less in order to improve the solubility. Moreover, when the antibacterial metal ions are added to the slurry, it is desirable that the mixing be performed at room temperature.

On the other hand, when the amount of ACP particles in the slurry is 90% by weight or more, the viscosity of the slurry becomes high, which makes it unsuitable for mixing and granulation. ACP in the slurry
By changing the content of particles in the range of 1 to 90% by weight,
Granulated particles having a desired average particle size can be obtained.

As the granulating method, if the obtained granulated particles are porous and have a substantially spherical shape with a particle size of 200 μm or less and a specific surface area of 50 m ² / g or more, Although not limited, for example, a spray drying granulation method can be used, and a granulation method of freeze-drying and pulverization, or a high-speed stirring granulation method may also be used.

In the above antibacterial coating composition, the coating film forming element and coating film auxiliary element contained therein are not particularly limited, but representative examples include acrylic resin and vinyl acetate emulsion coating materials. Alternatively, acrylic resin-based and alkyd resin-based solvent-based paints may be mentioned.

[0017]

EXAMPLE An example of the present invention will be described below with reference to FIG. In the antibacterial coating composition,
Amorphous Calcium Phosphate (Amorphous Calcium Phosphate) that holds antibacterial metal ions such as silver ions by adsorption
ium Phosphate: hereinafter abbreviated as ACP) Particles formed into a substantially spherical shape are added to the coating composition.

The above coating composition is selected to have a small affinity for ACP particles. The particle size of the ACP particles is set according to the thickness of the coating film set by the viscosity determined by the physical properties and concentration of the coating composition.

As a result, the antibacterial coating composition faces the ACP particles when the coating film is formed and the solvent is evaporated from the antibacterial coating composition to reduce the thickness of the coating film. When the coating layer on the front side becomes particularly thin and the thickness of the coating approaches the particle size of the ACP particles, the coating layer on the front side moves to the periphery due to surface tension. This is a coating composition,
This is because the surface of the ACP particles is not wetted by the coating composition because of its low affinity with the ACP particles.

This makes it easier for the ACP particles to be exposed from the surface of the coating film, and since the viscosity of the coating film resulting from evaporation of the solvent is high, it is also possible to prevent the ACP particles from being completely exposed. Then, the coating film is held.

The ACP particles were prepared by first adding 0.5% by weight of ammonium triacrylate as a weakly alkaline water-soluble polymer dispersant to a calcium hydroxide suspension with stirring.
After the addition to obtain a mixed solution, the pH of the mixed solution with stirring was adjusted to 10 by dropping an aqueous phosphoric acid solution to obtain a slurry. The above slurry contained ACP fine particles having a particle size of about 0.1 μm or less, because the addition of the ammonium triacrylate salt prevents the ACP particles from aggregating.

AC prepared by diluting the above slurry with ion-exchanged water so that the concentration of ACP is 20% by weight.
A P slurry was obtained. Anhydrous silver nitrate powder dissolved in ion-exchanged water was mixed with the ACP slurry so as to have the concentrations shown in Table 1, and stirred with a stirring motor for 1 hour to obtain mixed slurry. To convert the above mol% to weight%, add the conversion factor 1.07 to the above mol% value.
Just ask.

[0023]

[Table 1]

Subsequently, as shown in FIG. 1, ACP particles 1
And the above mixture slurry 3 containing silver ions 2 are spray-dried by a metering pump 4 (manufactured by Okawara Kakoki Co., Ltd.
L-8) Supply to 5. The atomizer 6 of the spray dryer 5 was rotated at a high speed, and the mixture slurry 3 was sprayed into the hot air stream for drying in the spray dryer 5 to be granulated and dried by the spray granulation method.

AC containing silver ion obtained by granulation drying
The substantially spherical antibacterial particles 7, which are P fine powder, are cyclone 8
5 to 20 μm was collected according to. At this time, ultrafine powder that could not be collected by the cyclone 8 was separately collected by a bag filter (not shown). As a result of measuring the specific surface area of each of the above antibacterial particles 7 by the BET method, the specific surface area of each of the above antibacterial particles 7 is 100 to 110 m ² / g.
Met.

The operating conditions in the spray-drying granulation were as follows. The supply rate of the mixture slurry 3 as a raw material by the metering pump 4 is 1 to 3 kg / h, and the temperature of the hot air heated by the electric heater 10 through the air filter 9 is equal to the inlet temperature of the hot gas chamber 11. 200 to 2
The outlet temperature at the discharge hole 12 connected to the cyclone 8 was controlled to 50 ° C. so as to always exceed 100 ° C., and the rotation speed of the atomizer 6 was set within the range of 10,000 to 37,000 rpm.

Further, two kinds of spray dryers (FOC-20, OD-25G, FOC-25, OC-25 manufactured by Okawara Kakoki Co., Ltd.), which are scale-ups of the above spray dryer 5, are used, and the slurry supply amount is 100 kg. When the antibacterial particles were prepared in the same manner as above under other conditions, the same antibacterial particles as the antibacterial particles 7 by the spray dryer 5 were obtained.
The antibacterial particles thus obtained were spherical.

Each of the antibacterial particles 7 obtained in each of the above-mentioned examples was examined for their production phase by the powder X-ray diffraction method, and although not shown, the obtained antibacterial particles 7 were obtained.
Is identified as a complex of calcium phosphate [Ca ₃ (PO ₄ ) ₂ · nH ₂ O] and silver, and since the X-ray diffraction pattern is broad, calcium phosphate is amorphous. I understand.

It was also identified that the antibacterial particles 7 had silver ions incorporated in calcium phosphate to form a solid solution state of the both. That is, it is assumed that silver ions are incorporated in the above-mentioned calcium phosphate microcrystals, positions of calcium ions, and the like.

Next, the above sample No. 1, sample No. 2, sample No. 3
The antibacterial activity of each was measured. As Comparative Example 1, commercially available antibacterial apatite particles (having a silver ion content of 2% by weight) were used.

Test method 1. Preparation of bacterial solution Test bacterial cells cultured in agar medium at 37 ° C for 18 hours are suspended in phosphate buffer (1 / 15M, pH 7.2) to prepare a stock solution of 10 ⁸ cells / ml. The stock solution was diluted appropriately and used for the test.

2. Antibacterial test (Shake flask method) Weigh 0.1 g of each sample, and add 100 g of the above phosphate buffer solution.
Place the solution in a 200 ml Erlenmeyer flask containing ml and add the test bacterial suspension to about 10 ⁵ cells / ml, and shake the Erlenmeyer flask while keeping it at 25 ° C ± 5 ° C. Then, the number of bacteria in the Erlenmeyer flask was measured. The strains used are as follows.

Strains used Escherichia coli (E. coli) IFO-12734 Staphylococcus aureus IFO-12732 Psedomonas aeruginosa IFO-12689 Candida albicans IFO-1060 Medium used Bacteria: Mueller Hinton 2 (BBL) ) Fungus: potato dextrose agar medium (Eiken) The above measurement results are shown in Tables 2-5.

[0034]

[Table 2]

[0035]

[Table 3]

[0036]

[Table 4]

[0037]

[Table 5]

As described above, the antibacterial particles 7 of the above-mentioned embodiment are
It was shown that the antibacterial action is higher than that of the apatite particles which are commercially available as conventional antibacterial particles. This is because the antibacterial particles 7 of each of the above-mentioned examples are porous and thus have a large specific surface area which is an area in contact with bacteria, and further, the ACP used as the base material has a high bacteria adsorption capacity (Asahi Shimbun, 1993 1
It is assumed to have the evening edition, 16th of the month, see).

Next, an example of the antibacterial coating composition using the antibacterial particles 7 of Sample No. 3 will be described.
Thermoplastic acrylic emulsion (solid content concentration 50.0% by weight, manufactured by Nippon Acrylic Chemical Co., Ltd., trade name: PRIMAL AC-
55) 70% by weight, titanium oxide (manufactured by Toho Titanium Co.) 10% by weight, and hydroxyethyl cellulose 0.4%.
% By weight, 2% by weight of polycarboxylic acid type polymer surfactant
Were weighed and mixed to prepare an acrylic emulsion paint.

100 g of this acrylic emulsion paint
Weigh it and pour it into a stainless beaker.
No. 3 antibacterial particles 7 (particle diameter 12 μm) were added so as to be 10% by weight and mixed by stirring to obtain an antibacterial coating composition (composition 1).

As another example of the antibacterial coating composition,
Thermoplastic acrylic emulsion (solid content concentration 46.5% by weight, manufactured by Nippon Acrylic Chemical Co., Ltd., trade name: PRIMAL AC-
61) 70% by weight, titanium oxide 10% by weight, hydroxyethyl cellulose 0.4% by weight, polycarboxylic acid type polymeric surfactant 2% by weight,
These were mixed to prepare an acrylic emulsion paint.

100 g of this acrylic emulsion paint
Weigh it and pour it into a stainless beaker.
No. 3 antibacterial particles 7 (particle diameter 12 μm) were added so as to be 10% by weight and mixed by stirring to obtain an antibacterial coating composition (composition 2).

As still another example of the antibacterial coating composition, 70 weight parts of a thermoplastic acrylic colloidal dispersion (concentration of solid content: 30.0% by weight, manufactured by Nippon Acrylic Chemical Co., Ltd., trade name: Primal I-94) is used. %, 10% by weight of the titanium oxide, 0.4% by weight of hydroxyethyl cellulose (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), and 2% by weight of the polycarboxylic acid type polymer surfactant, and they are mixed. An acrylic colloidal dispersion paint was prepared.

100 g of this acrylic colloidal dispersion paint was weighed and poured into a stainless beaker,
Add 1 of the antibacterial particles 7 (particle size 12 μm) of Sample No. 3 to this.
An antibacterial coating composition (composition 3) was obtained by adding 0% by weight and stirring and mixing.

Next, each composition 1, 2, 3 obtained above
The antibacterial activity of each of these was measured. As Comparative Example 2,
The acrylic emulsion paint described in the preparation method of Sample No. 1 was used. The coating compositions 1 to 3 and the coating compositions of Comparative Example 2 were applied on a wooden board and dried to form a coating film, and the number of viable bacteria on the coating film was measured by the following test method.

Test method 1. Preparation of bacterial solution Preparation of bacterial cells used in the test In a flask containing 100 ml of liquid medium containing 15 kinds of inorganic compounds, vitamins, and sucrose, 0.1 g of soil collected in Nara prefecture was placed, and it was 48 at 25 ° C. The culture was shaken for an hour. Next, after taking out the above flask and leaving it to stand for 5 minutes, 1.0 ml of the supernatant was taken out, and 100 ml of the above liquid medium was newly added.
It was added to the flask containing 1 and shake-cultured at 25 ° C. for 48 hours. This operation was performed twice. When a part of the culture solution thus obtained was taken out and observed with a microscope,
It was confirmed that the bacterial cells in the culture solution were uniform white spherical bacteria.

Antibacterial test The culture solution of white spherical bacteria obtained above was diluted stepwise to 10 ^-3 with sterile physiological saline, and the diluted culture solution diluted to 10 ^-2 and 10 ^-3 was added to the bacterial solution. Used as. First, about 20 ml of sterilized and dissolved agar medium for measuring viable bacteria was dispensed into a sterile petri dish to solidify.

0.05 ml each of the diluted culture broth diluted to 10 ^-2 and 10 ^-3 was uniformly applied onto such a medium with a conradi stick. A wooden board (1.5 x 1.5 cm) with a coating film of each composition 1 to 3 formed in the center of each medium.
Was placed so that the coating film was in contact with the medium surface. afterwards,
The petri dish was covered with a lid and sealed with parafilm, and then cultured at 25 ° C. for 1 day. Then, when each of the wooden boards was removed from each petri dish and each of the petri dishes was further cultured, no colony of bacterial cells was observed on the medium surface of each of the petri dishes.

On the other hand, similarly, in the test using the paint as Comparative Example 2, many colonies were observed on the medium surface of the petri dish. As a result, the coating films of the compositions 1 to 3 have antibacterial properties, so that the antibacterial particles 7 ... Blended in the antibacterial coating composition are exposed from the surface of the coating film. It is understood that there is.

Further, since the antibacterial particles 7 are spherical in shape as described above, they are easily dispersed uniformly in the coating composition, and the mixing property with respect to the coating composition can be improved more than before.

Next, it is envisaged that each of the first to third compositions is used in the white tray such as a foamed plastic tray on which fresh food is placed. From this, when the blended antibacterial particles 7 are colored,
If the tray is exposed to sunlight or fluorescent light and discolors, the user may mistakenly recognize that dust or dirt is attached to the tray.

Therefore, coating films of each of the above sample No. 1 and sample No. 3 were formed on the surface of the plate, and the color difference of these coating films was measured over time. Further, as Comparative Example 3, a similar antibacterial coating composition was used in which commercially available antibacterial apatite particles (having a silver ion content of 2% by weight) were blended in place of the antibacterial particles 7 in Sample No. 1. A coating film was used.

Next, the method for measuring the color difference of each of the above coating films will be described. The above sample No. 1, sample No. 3 and comparative example 3 were described.
The coating films are exposed to UV light for 10 days with a black light, and the surface of those coatings is measured with an integrating sphere color difference meter (ND
-100P, manufactured by Nippon Denshoku Industries Co., Ltd.), the coating films of Sample No. 1 and Sample No. 3 maintained white without discoloration. A pink discoloration was observed on the film.

As described above, in the structure of the above-mentioned embodiment, by using many of the added antibacterial particles 7 ... Can be exposed, and the amorphous calcium phosphate having the ability to adsorb bacteria is used as a carrier for silver ions, Antibacterial particles 7
The antibacterial property can be effectively exhibited, and the antibacterial property can be improved as compared with the conventional case where many antibacterial particles are buried in the coating film.

Therefore, in the above-mentioned constitution, the sterilization state is maintained by the antibacterial particles 7 which are mixed at the time of being manufactured or stored, and in addition, the antibacterial properties of the compounded even when exposed to ultraviolet rays. Since the particles 7 can avoid discoloration and remain colorless, that is, white, for example, even if the particles 7 are applied to the surface of a commercially available plastic container or the like, the user may misidentify the antibacterial particles 7 as stains or the like. To be prevented.

Therefore, in the above-mentioned constitution, since the surface of the plastic container such as a lamin pack can be coated with the antibacterial particles 7, it is possible to suppress the growth of various bacteria on the food placed on the plastic container as compared with the conventional case.
It is possible to avoid deterioration of the appearance of the plastic container. Further, the above-described structure can also prevent the deterioration of the coated surface of houses, hospitals, factories, etc., and can avoid the deterioration of the environment due to the growth of bacteria and mold on the coated surface.

By the way, in the conventional antibacterial coating composition containing the antibacterial zeolite solid particles, since the particle shape of the antibacterial zeolite solid particles is block-shaped, that is, indeterminate, slipperiness during application is improved. Is inferior. From this fact, the above antibacterial coating composition has poor spreadability during application, and it is difficult to obtain a coating film having a uniform thickness, and unevenness is likely to occur.

However, in the constitution of the above-mentioned embodiment, since the mixed antibacterial particles 7 are spherical, the spreadability at the time of application is good and a more uniform coating film can be formed. Moreover, since the antibacterial particles 7 are granulated, the particle size can be increased while maintaining the large specific surface area. Thereby, the proportion of the antibacterial particles 7 exposed from the surface of the coating film can be increased, so that the antibacterial property of the coating film can be improved.

Further, in the constitution of the above-mentioned embodiment, when the antibacterial property equivalent to the conventional one is required, the amount of the antibacterial particles 7 added can be reduced and the amount of silver or the like used can be reduced. Therefore, the cost can be reduced more than ever before. On the other hand, when the antibacterial particles 7 are added in the same amount as in the conventional case, the antibacterial particles 7 that contribute to the antibacterial property can be significantly increased compared with the conventional one, so that the antibacterial property can be stably maintained for a long period of time.

As a result, the above-mentioned constitution is excellent in antibacterial properties and can avoid deterioration of appearance, so that it is suitable for use as a tray for placing food such as fresh food, coating of medical equipment, and coating for building exteriors. Can be used.

In the structure of the above embodiment, an example in which white titanium oxide is added as a pigment has been given, but other pigments can be used if necessary. Further, the addition of the pigment can be omitted and the antibacterial particles 7 can also be used as a white pigment.

[0062]

As described above, the antibacterial coating composition according to the first aspect of the present invention comprises amorphous calcium phosphate particles retaining antibacterial metal ions.

Therefore, the above-described structure has a high antibacterial property and prevents discoloration, so that it can be suitably used for a tray for placing food such as fresh food.

As described above, the antibacterial coating composition according to the second aspect of the present invention has a composition containing the antibacterial metal ions and holding the amorphous calcium phosphate particles granulated into a substantially spherical shape.

Therefore, the above-mentioned constitution has the further effect that the deterioration of the slipperiness as a paint can be avoided and a more uniform coating film can be formed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a spray dryer used for antibacterial particles of a coating composition of the present invention.

[Explanation of symbols]

 1 ACP particles (amorphous calcium phosphate particles) 2 Silver ions (antibacterial metal ions) 7 Antibacterial particles

Claims (2)

[Claims] 1. An antibacterial coating composition comprising amorphous calcium phosphate particles retaining antibacterial metal ions. 2. An antibacterial coating composition containing amorphous calcium phosphate particles which retain antibacterial metal ions and are granulated into a substantially spherical shape.