JP2003171469A - Method for producing chitosan aqueous solution, antibacterial coating agent and antibacterial film or antibacterial sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for easily producing a large amount of a neutral aqueous solution of chitosan using an inexpensive common chitosan and useful for the production of e.g. a food packaging material, a medical packaging material and an antibacterial sheet effective for suppressing the proliferation of bacterial in a drip liquid separated and flowed out from meat, fish, etc., and keeping the freshness of foods over a long period. <P>SOLUTION: The invention provides a method for the production of an aqueous solution of chitosan by dissolving a chitosan in an aqueous solution of an acid and neutralizing the obtained chitosanic acid solution, an antibacterial coating agent containing the chitosan aqueous solution produced by the above method and an aqueous dispersion or emulsion of a synthetic resin, and an antibacterial sheet or film produced by coating a substrate sheet of film with the antibacterial coating agent. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing an aqueous chitosan solution, an antibacterial coating agent, and an antibacterial sheet or antibacterial film. The present invention relates to a method for producing an aqueous chitosan solution capable of producing an aqueous chitosan solution, an antibacterial coating agent containing the chitosan aqueous solution produced by the method, and an antibacterial sheet or antibacterial film coated with the antibacterial coating agent.

[0002]

2. Description of the Related Art Chitosan is one of high molecular weight polysaccharides obtained by hydrolyzing chitins that are widely present in nature. Chitosan is very safe as it is used in food additives. In addition, chitosan has an antibacterial action, and its antibacterial utilization is drawing attention. Generally, mass-produced, easily available and inexpensive chitosan has a deacetylation degree of about 70 to 95%. Chitosan is obtained in powder form. To use this by coating it on various materials,
It is necessary to make it a solution. Deacetylation degree of 70 for mass production
Up to 95% of chitosan is insoluble in water and soluble in inorganic acids such as hydrochloric acid and sulfuric acid or organic acids such as acetic acid, lactic acid and malic acid.

However, the chitosan solution dissolved with these acids has the following drawbacks in practical use.

First, solution-type hydrogen ions are not preferable because corrosion or the like is likely to occur depending on the material to be used. In addition, depending on the type of acid, some are dangerous to the human body, and care must be taken in handling. Furthermore, the viscosity changes significantly over time, and the viscosity gradually decreases, making long-term storage difficult.

On the other hand, chitosan, which has a deacetylation degree of 40 to 60% and which is subjected to decompression, management of heat of neutralization and removal of by-products in a homogeneous system, is soluble in neutral water. There are many steps for purification, and the price is very expensive.

Therefore, in order to solve such a problem,
Sakai and Yoshioka et al. Used 0.1N of water-insoluble powdered chitosan.
After dissolving with hydrochloric acid, the same amount of 0.1N aqueous sodium hydroxide solution was added dropwise to precipitate chitosan gel, which was washed with water, suspended in water, and bubbled with carbon dioxide gas for several minutes. Proposed to obtain neutral aqueous chitosan solution [Polymer Prepprints, J
apan (Proceedings of the Polymer Society of Japan) Vol. 50, No.
5, page 933 (2001)].

However, this method has two steps: a step of producing a gel by neutralizing a chitosan acid solution, and a step of resuspending the gel in water, bubbling with carbon dioxide gas, and dissolving it.
Since it is a stepwise method, there are problems in that the number of steps is large and the mass production is difficult, so that the cost is increased.

The present invention has been made in view of the above circumstances. For example, the degree of deacetylation is 70 to 9 which is easily available and inexpensive.
It is an object of the present invention to provide a method for producing an aqueous chitosan solution, which can be economically mass-produced using 5% water-insoluble general chitosan and which can be used as a neutral chitosan aqueous solution for a wide range of applications.

[0009]

Means for Solving the Problems and Modes for Carrying Out the Invention As a result of intensive studies to solve the above problems, the present inventor has found that an alkaline carbonate and / or carbonate as an alkaline compound used for neutralizing a chitosan acid solution. It was found that the use of hydrogen salt enables neutralization and dissolution of carbon dioxide gas generated during neutralization by bubbling at the same time. As a result, even when general chitosan is used, neutral chitosan can be easily prepared in one step from a chitosan acid solution. The inventors have found that an aqueous solution can be produced and have completed the present invention.

That is, according to the present invention, (1) chitosan is dissolved in an aqueous acid solution to give a chitosan acid solution, and the chitosan acid solution is neutralized with an alkali carbonate and / or hydrogen carbonate to give a neutral solution. A method for producing a chitosan aqueous solution, which comprises producing the chitosan aqueous solution. Here, it is more preferable to use one or more kinds selected from alkali metal carbonates, alkaline earth metal carbonates, alkali metal hydrogen carbonates and alkaline earth metal hydrogen carbonates for neutralizing the chitosan acid solution. .

Furthermore, the present invention provides (2) an aqueous dispersion or emulsion of an aqueous chitosan solution prepared by the method for producing an aqueous chitosan solution described in (1) above and a synthetic resin, particularly an ionomer and / or an acrylic resin. An antibacterial coating agent characterized by containing
And (3) an antibacterial sheet or an antibacterial film obtained by applying the antibacterial coating agent according to the above (2) to a sheet-shaped substrate or a film-shaped substrate.

The present invention will be described in more detail below. In the method for producing an aqueous chitosan solution of the present invention, chitosan is dissolved in an aqueous acid solution to give a chitosan acid solution, and the chitosan acid solution is then treated with an alkali carbonate and / or Alternatively, it is neutralized with a hydrogen carbonate to produce a neutral chitosan aqueous solution.

Here, the type of chitosan used as the starting material of the present invention is not particularly limited, and for example, the degree of deacetylation is not particularly limited, but according to the production method of the present invention, deacetylation is performed. Even without using chitosan having a degree of 40 to 60% (mass%, the same applies below), it can be used in a wide range of applications by using chitosan having a deacetylation degree of 70 to 95% which is generally easily available and inexpensive. Considering that a neutral aqueous chitosan solution can be obtained from a chitosan acid solution in one step, it is desirable to use chitosan having a deacetylation degree of 70 to 95%, particularly 75 to 90% which is easily available.

In the production method of the present invention, the kind of acid aqueous solution in which the above chitosan is dissolved to form a chitosan acid solution is not particularly limited, and the acidic compound is an inorganic acid such as hydrochloric acid or sulfuric acid or Organic acids such as acetic acid, lactic acid and malic acid can be used, and these can be used alone or in combination of two or more kinds. The concentration of the above-mentioned acidic compound in the aqueous acid solution is not particularly limited, but is usually 0.05 to 1 N, particularly 0.1.
It is suitable that it is 05-0.5N. If the concentration is too high, it may be difficult to carry out the next neutralization step, and if it is too thin, it may be necessary to add a large amount of aqueous acid solution in order to dissolve chitosan.

The mixing ratio of the aqueous acid solution to the chitosan is not particularly limited, but usually 50 to 250 parts by weight, particularly 80 to 250 parts by weight of the aqueous acid solution is used per 1 part by weight of the chitosan. Is preferred.
If the mixing ratio of the acid aqueous solution is too large, a large amount of carbonate or hydrogen carbonate may be required in the next neutralization step,
If it is too small, the dissolution of chitosan may be insufficient.

When the chitosan is dissolved in the acid aqueous solution, it is not necessary to heat it or use a special stirrer, and it can be dissolved at room temperature using a normal stirrer.

In the production method of the present invention, the type of alkali carbonate or hydrogen carbonate for neutralizing the chitosan acid solution is not particularly limited, and various carbonates and hydrogen carbonates are used. However, in the case of the present invention, considering that a carbonate or hydrogen carbonate having high solubility in water is desirable, carbonic acid of an alkali metal such as sodium or potassium, hydrogen carbonate, barium, calcium or the like. It is preferable to use the carbonic acid or hydrogen carbonate of the alkaline earth metal, and more preferably the alkali metal carbonate or the alkali metal hydrogen carbonate. In consideration of the bubbling effect, hydrogen carbonate having a large amount of carbon dioxide gas generated when neutralized is preferable, and in consideration of the solubility in water, sodium, potassium or other alkali metal hydrogen carbonate is particularly preferable. preferable.

More specifically, the carbonate and hydrogen carbonate used in the present invention include, for example, potassium carbonate, sodium carbonate, calcium carbonate, barium carbonate, potassium hydrogen carbonate, sodium hydrogen carbonate, calcium hydrogen carbonate,
Examples thereof include barium hydrogen carbonate, and these can be used alone or in combination of two or more kinds as appropriate.
These may be powders, solids, or solutions.

The amount of the above-mentioned carbonate and / or hydrogen carbonate to be added is not particularly limited, but in consideration of neutralizing the acid used when dissolving the above chitosan in an aqueous acid solution, It is preferable that the amount of the alkali is the same as that of the acid, but it is not always necessary to be the same, and even if the pH is raised or lowered, it is unbalanced as long as it is in a range compatible with the purpose of use of the obtained chitosan aqueous solution. It doesn't matter.

When the chitosan acid solution is neutralized with the carbonate and / or hydrogen carbonate, it is not necessary to heat the solution, and it may be at room temperature. An aqueous solution neutralized by bubbling carbon dioxide gas can be obtained without stirring, but stirring is preferable from the viewpoint of accelerating the reaction. When stirring, it is not necessary to use a special stirring device, and neutralization can be performed using a normal stirring device at room temperature.

According to the production method of the present invention, by using carbonate and / or hydrogen carbonate as the alkali compound used for neutralizing the chitosan acid solution, neutralization and dissolution by bubbling carbon dioxide can be performed simultaneously. Therefore, for example, even if general chitosan having a deacetylation degree of 70 to 95% is used, a neutral chitosan aqueous solution can be produced from the chitosan acid solution in one step.

The use of the chitosan aqueous solution obtained by the above-mentioned production method is not particularly limited, but it is preferable to use it as an antibacterial coating agent utilizing the antibacterial action of chitosan. In particular, the antibacterial coating agent of the present invention containing the above chitosan aqueous solution and a dispersion or emulsion of a synthetic resin is more preferable because it becomes an antibacterial coating agent that is hard to remove even when washed with water.

Here, the synthetic resin contained in the antibacterial coating agent of the present invention is an emulsion or an aqueous dispersion, and the kind thereof is not particularly limited as long as it can be used as a coating agent, but in the case of the present invention In consideration of water resistance after coating, heat sealability, etc., the above synthetic resin is a copolymer containing an unsaturated carboxylic acid as a monomer component, and a portion of a copolymer containing an unsaturated carboxylic acid as a monomer component due to a metal ion. Neutralized or completely neutralized ionomers and the like are suitable, and these can be used alone or in combination of two or more kinds.

That is, the copolymer containing the unsaturated carboxylic acid component is not compatible with chitosan as it is, but when the aqueous dispersion or emulsion is mixed with chitosan, the amino group of chitosan and the carboxyl group of the copolymer are mixed. Due to the interaction with the group, it is uniformly dispersed in water and can be suitably used as a coating agent.

In the case of the present invention, among the above synthetic resins, ethylene-α, β unsaturated carboxylic acid copolymers, ethylene-
Ionomer or the like, which is partially neutralized or completely neutralized with a metal ion of an α, β unsaturated carboxylic acid copolymer, is preferable.
In particular, an acrylic resin which is a (co) polymer containing acrylic acid, methacrylic acid and its derivative as a monomer component, and an ionomer obtained by neutralizing the acrylic resin with a metal ion such as Na ion are more preferable. In addition, in the present invention, the "copolymer" is not limited to those composed of two kinds of monomers, and also includes a terpolymer including three or more kinds of monomers.

The content of the unsaturated carboxylic acid component of the synthetic resin is not particularly limited, but in consideration of the water resistance of the resin, the synthesis of the unsaturated carboxylic acid component of about 1 to 30% by mass. Resins are more preferred.

The dispersion or emulsion of the above synthetic resin can be produced by a known method,
For example, as a method for preparing an emulsion of the acrylic resin, a monomer component of the acrylic resin, a polymerization catalyst commonly used for the monomer component, an appropriate kind of surfactant and water are added, and this is emulsified by a conventional method. Examples of the method for preparing the aqueous dispersion of the ionomer include a method of polymerizing the ionomer with sodium hydroxide (NaOH) or potassium hydroxide (KOH).
Alternatively, it is put into water in the presence of an alkali such as ammonia water (NH ₄ OH), and then, for example, 1 in an autoclave.
Examples include a method of dispersing the above ionomer in water by stirring under heating and pressurization at 00 ° C. or higher. Or Saixen (Sumitomo Seika Co., Ltd.),
It is also possible to use an aqueous dispersion of a resin that is commercially available under the trade name of Chemipearl (manufactured by Mitsui Chemicals, Inc.).

In the coating agent of the present invention, the amount of the chitosan aqueous solution, the dispersion of the synthetic resin or the emulsion to be added is not particularly limited, but the chitosan is 10 to 10 parts by mass of the synthetic resin. It is preferable that the compounding amount be 70 parts by mass. If the blending ratio of chitosan is too low, the surface area of chitosan exposed on the surface of the coating layer will be increased, so sufficient antibacterial properties will be obtained without the addition of surfactants, stirring methods, coating methods and selection of resins. May not be obtained. On the other hand, if the blending ratio of chitosan is too high, the coating may be peeled off or dissolved by water after being used as a coating agent.
Here, for example, when the coating agent of the present invention is applied to a film-shaped substrate or the like, considering the appearance of the film after coating, in the coating agent, the chitosan content is 10 to 10 parts by mass with respect to 100 parts by mass of the synthetic resin. 40
It is more preferable that the compounding ratio be such that the ratio is parts by mass.

The amount of the above synthetic resin and chitosan to be added to the entire coating agent of the present invention is not particularly limited, but it is easy to handle as a coating agent,
Considering the antibacterial effect and the like, the above-mentioned synthetic resin is usually contained in an amount of 0.1 to 20% by mass, particularly 1 to 10% with respect to the whole coating agent.
% By mass, 0.02 to 2% by mass of chitosan, especially 0.1 to
It is more preferable to mix it so as to be 1% by mass.

The coating agent of the present invention can contain an alkali such as sodium hydroxide (NaOH), potassium hydroxide (KOH) or ammonia (NH ₃ ) as a dispersion aid. In addition to the above-mentioned essential components, various components which are usually blended in the coating agent can be blended in a usual dose as necessary in a range that does not hinder, and as such components, for example, a surfactant, a thickener, and an ultraviolet absorbing agent. Agents and the like can be added.

The method for producing the coating agent of the present invention is not particularly limited. For example, when the emulsion or dispersion of the ionomer and / or acrylic resin and the chitosan aqueous solution are mixed, the emulsion or dispersion is prepared. It is preferable to add an aqueous chitosan solution with stirring and to stir the mixture under normal conditions of the apparatus using, for example, a chemister or magnetic stirrer until the whole is uniform.

The coating base material of the coating agent of the present invention is not particularly limited and can be applied to various base materials. Particularly, when it is applied to a sheet-shaped base material or a film-shaped base material, it is effective. Is.

The antibacterial sheet or antibacterial film of the present invention is obtained by coating the above-mentioned coating agent on a sheet-shaped substrate or a film-shaped substrate, and the type of the sheet-shaped substrate or the film-shaped substrate is It is not particularly limited, and for example, synthetic resin sheet or film, non-woven fabric, aluminum foil, paper and the like can be used. Specific examples of the synthetic resin include polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate, and polyamide resins such as 6-nylon. The antibacterial sheet or antibacterial film of the present invention is not limited to a sheet shape or a film shape, and includes a tape shape and the like.

The coating amount of the above-mentioned coating agent on the antibacterial sheet or film of the present invention is not particularly limited and may be any coating amount, but the coating thickness after drying is usually 1 to 30 μm, In particular, it is preferable to apply the coating so that the thickness is 1 to 20 μm. If the coating film thickness is too thin, the coating may be uneven and sufficient antibacterial properties may not be obtained, and if it is too thick, further antibacterial properties may not be improved, which may be uneconomical. .

The method for producing the antibacterial sheet or the antibacterial film of the present invention is not particularly limited. For example, the surface of the sheet-shaped substrate or the film-shaped substrate is coated with the coating agent by a spray coater, a gravure coater, a roll coater or the like. After applying evenly to 80 to 13
By drying for 5 to 10 minutes under a heating condition of 0 ° C. to remove the water content of the coating agent and to cure the coating agent,
An antibacterial sheet can be obtained.

[0036]

According to the method for producing a chitosan aqueous solution of the present invention, a neutral chitosan aqueous solution can be produced easily and mass-producible even if an inexpensive general chitosan is used. Therefore, according to the antibacterial coating agent, antibacterial sheet or antibacterial film of the present invention using the chitosan aqueous solution produced by such a production method, the antibacterial coating agent has sufficient antibacterial properties and is also excellent in safety and production cost. A cheap coating agent, antibacterial sheet, and antibacterial film can be obtained. Therefore, the present invention, for example, an antibacterial sheet that suppresses the growth of bacteria in drip liquid that is separated and flows out from food packaging, medical packaging, meat, fish, etc., and keeps the freshness of food for a long period of time, antibacterial It is useful in producing a flexible film.

[0037]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Example 1 Chitosan (Deacetylation Degree 7
5-85%: Kimitsukitosan LLWP) 0.5 g.
After dissolving with 100 g of 1N hydrochloric acid, it was neutralized with 1.0 g of KHCO ₃ to obtain a neutral chitosan aqueous solution.

Example 2 Chitosan (Deacetylation Degree 7
5-85%: Kimitsukitosan LLWP) 0.5 g.
After dissolving with 100 g of 1N hydrochloric acid, NaHCO ₃ 0.84
Neutralization with g gave a neutral aqueous chitosan solution.

Example 3 Chitosan (Deacetylation Degree 7
5-85%: Kimitsukitosan LLWP) 0.5 g.
After dissolving with 100 g of 1N hydrochloric acid, it was neutralized with 0.69 g of K ₂ CO ₃ to obtain a neutral chitosan aqueous solution.

Example 4 Chitosan (Deacetylation Degree 7
5-85%: Kimitsukitosan LLWP) 1.0 g
After dissolving with 100 g of 1N hydrochloric acid, 0.84 g of KHCO ₃
The solution was neutralized with to obtain a neutral chitosan aqueous solution.

Example 5 Chitosan (Deacetylation Degree 7
5-85%: Kimitsukitosan LLWP) 1.0 g
After dissolving with 100 g of 1N hydrochloric acid, NaHCO ₃ 0.84
Neutralization with g gave a neutral aqueous chitosan solution.

Example 6 Chitosan (Deacetylation Degree 7
5-85%: Kimitsukitosan LLWP) 1.0 g
After dissolving with 100 g of 1N hydrochloric acid, it was neutralized with 0.69 g of K ₂ CO ₃ to obtain a neutral chitosan aqueous solution.

Example 7 Chitosan (Deacetylation Degree 7
5-85%: Kimitsukitosan LLWP) 0.5 g.
After dissolving with 100 g of 1N hydrochloric acid, 0.53 g of Na ₂ CO ₃
The solution was neutralized with to obtain a neutral chitosan aqueous solution.

Example 8 Chitosan (Deacetylation Degree 7
5-85%: Kimitsukitosan LLWP) 0.5 g.
After dissolving with 100 g of 1N hydrochloric acid, 0.50 g of CaCO ₃
The solution was neutralized with to obtain a neutral chitosan aqueous solution.

Example 9 Chitosan (Deacetylation Degree 7
5-85%: Kimitsukitosan LLWP) 0.5 g.
After dissolving with 100 g of 1N hydrochloric acid, BaCO ₃ 0.99 g
The solution was neutralized with to obtain a neutral chitosan aqueous solution.

Comparative Example 1 Chitosan (Deacetylation Degree 7
5-85%: Kimitsukitosan LLWP) 0.5 g.
After dissolving with 100 g of 1N hydrochloric acid, it was neutralized with 0.4 g of NaOH.

Comparative Example 2 Chitosan (Deacetylation Degree 7
5-85%: Kimitsukitosan LLWP) 0.5 g.
After dissolving with 100 g of 1N hydrochloric acid, it was neutralized with 0.56 g of KOH.

Comparative Example 3 Chitosan (Deacetylation Degree 7
5-85%: Kimitsukitosan LLWP) 0.5 g.
It was dissolved with 100 g of 1N hydrochloric acid to obtain a chitosan acid solution.

Comparative Example 4 Chitosan (Deacetylation Degree 7
5-85%: Kimitsukitosan LLWP) 0.5 g.
After dissolving with 100 g of 1N hydrochloric acid, 100 g of 0.1N NaOH aqueous solution was added dropwise to obtain a chitosan gel. The gel was washed with water, suspended in water, and carbon dioxide gas was bubbled to obtain an aqueous chitosan solution.

Comparative Example 5 Chitosan (Deacetylation Degree 7
5-85%: Kimitsukitosan LLWP) 0.5 g.
After dissolving with 100 g of 1N hydrochloric acid, it was neutralized with 1.6 g of (NH ₄ ) ₂ CO ₃ (ammonia content 30 wt%) to obtain a neutral aqueous chitosan solution.

The appearance of each obtained chitosan solution was visually observed, and the solubility was evaluated based on the following criteria.
Moreover, the pH was confirmed using pH test paper. The results are shown in Table 1.

<Evaluation Criteria for Solubility> ◯: A transparent aqueous solution without precipitation was obtained. Δ: There was a residue (precipitate), but a transparent aqueous solution was obtained, and there was no problem in actual use. X ... Gelled and chitosan separated as a solid.

[0054]

[Table 1]

[Examples 10 to 13 and Comparative Example 6] Using the chitosan solutions of the above-mentioned Example 7, Example 8 and Comparative Example 3,
The antibacterial coating agents of Examples 10 to 13 and Comparative Example 6 were prepared according to Table 2. The appearance of these solutions was visually observed. The results are also shown in Table 2.

[0056]

[Table 2]

Ionomer ^{* 1} : An ethylene-acrylic acid copolymer (acrylic acid content: 15% by mass) is neutralized with Na ions (neutralization degree: 60%) to give an ionomer in water.
An ionomer dispersion dispersed by stirring for 30 minutes under heating and pressurization in an autoclave at 130 ° C. in the presence of ammonia so that the solid content of the acrylic acid copolymer becomes 20% by mass. Acrylic resin ^{* 2} : (meth) acrylic acid ester-acrylic acid copolymer (acrylic acid content 3.5% by mass, "ALMATEX K271", manufactured by Mitsui Chemicals, Inc.) in water to make 20% by mass. , Mixed and dispersed acrylic resin emulsion.

[Examples 14 to 21] Examples 10 to 1 above
The antibacterial coating agent of No. 3 was applied to the corona-treated surface of a film made of polyethylene terephthalate having a thickness of 75 μm, which was corona-treated on one side, using a Mayer bar so that the coating thickness after drying would be the film thickness shown in Table 3. Apply and 10 at 90 ℃
After drying for minutes, the antibacterial films of Examples 14 to 21 were obtained. With respect to each antibacterial film, the water resistance of the antibacterial coating film was evaluated by the following method. The results are also shown in Table 3.

(1) Water resistance evaluation method Water was dropped with a dropper on the surface of each antibacterial film coated with the antibacterial coating agent, and after 10 minutes, the water was wiped off to visually observe the state of the antibacterial coating agent film. The case where there was no change in appearance was evaluated as ◯, and the case where there was a change in appearance was evaluated as x.

[0060]

[Table 3]

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) C09D 201/00 C09D 201/00 // C08L 5:08 C08L 5:08 F term (reference) 4F070 AA01 AB01 AB13 CA12 CB02 CB11 4J038 BA011 BA012 CG001 CG002 CG091 CG092 HA266 MA08 MA10 PB02 PB04 PC08

Claims (5)

[Claims] 1. A method for producing a neutral chitosan aqueous solution by dissolving chitosan in an aqueous acid solution to form a chitosan acid solution, and then neutralizing the chitosan acid solution with a carbonate and / or hydrogen carbonate. A method for producing an aqueous chitosan solution. 2. The neutralization of the chitosan acid solution is selected from alkali metal carbonates, alkaline earth metal carbonates, alkali metal hydrogen carbonates and alkaline earth metal hydrogen carbonates.
The method for producing an aqueous chitosan solution according to claim 1, wherein at least one species is used. 3. An antibacterial coating agent comprising an aqueous chitosan solution prepared by the method for producing an aqueous chitosan solution according to claim 1 or 2, and an aqueous dispersion or emulsion of a synthetic resin. 4. The antibacterial coating agent according to claim 3, wherein the synthetic resin is an ionomer and / or an acrylic resin. 5. An antibacterial sheet or an antibacterial film, which is obtained by applying the antibacterial coating agent according to claim 3 or 4 to a sheet-shaped substrate or a film-shaped substrate.