JP2001342435A - Coating agent and antimicrobial sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating agent containing a synthetic resin emulsion or an aqueous dispersion and chitosan and an antimicrobial sheet in which the aforesaid coating agent is coated on a sheet-like base or a film-like base. SOLUTION: The coating agent of this invention has sufficient antimicrobial properties and, e.g. when coated on a heat sealable film-like base material, the material can be heat sealed and, when coated on a nonwoven fabric, paper or the like, stability against water can be added. Thus, this coating agent is useful for sheets, etc., used for suppressing growth of bacteria in drip solutions separated and flown out of packed foods, packed medical supplies, meats, fishes, etc., and keeping freshness of the foods for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antibacterial coating agent and an antibacterial sheet.

[0002]

2. Description of the Related Art Chitosan is a kind of high molecular polysaccharide obtained by hydrolyzing chitin, which exists widely in nature. Chitosan is classified as a food additive and has excellent safety. In addition, chitosan has an antibacterial action, and its use of antibacterial properties has attracted attention.

As means for utilizing such antibacterial properties,
Specifically, for example, it is conceivable to form a film or fiber from chitosan itself, but the film or fiber is not necessarily satisfactory in mechanical strength such as tensile strength, and the production of these products is not always sufficient. Was limited due to process problems.

In order to solve the above-mentioned problem, it is conceivable that a solution obtained by dissolving chitosan in an acidic aqueous solution is applied to the film surface to impart antibacterial properties. However, simply coating the film surface with a chitosan solution may be considered. However, since chitosan merely covers the surface, there is a problem that it has poor rub resistance and water resistance.

For this reason, Japanese Patent Application Laid-Open No. Hei 8-225669 discloses a method for forming a chitosan film through a graft polymer film having a free acidic group on the surface of a polymer substrate.

However, there is a problem that the water resistance of the chitosan film obtained by this method is not sufficient, and that the production process is complicated. Furthermore, since the chitosan film is formed on the surface, the original heat sealing property of the film is greatly reduced.For example, when used as food packaging, sufficient sealing strength is obtained in a bag making process or a filling process in food packaging or the like. There was a problem that it could not be obtained.

On the other hand, Japanese Patent Application Laid-Open No. 11-32742 discloses a chitosan aqueous solution containing a surfactant, but this has a problem that it lacks water resistance.

The present invention has been made in view of the above circumstances, and has an antibacterial effect by chitosan and, even when coated on a synthetic resin film or the like, serves as a base material having heat sealability and the like. Maintain the original physical properties of
It is still another object of the present invention to provide a coating agent which does not cause the coating to be peeled off or dissolved by water or the like and an antibacterial sheet having an antibacterial action by chitosan.

[0009]

Means for Solving the Problems and Embodiments of the Invention The present inventors have made intensive studies to achieve the above object, and as a result, for example, a copolymer containing an unsaturated carboxylic acid as a monomer component, and a copolymer containing the same. By using a mixture of chitosan and an emulsion or aqueous dispersion of a synthetic resin such as a partially or completely neutralized ionomer with metal ions to obtain the knowledge that the above problems can be solved,
The present invention has been made.

That is, the present invention provides (1) a coating agent comprising an emulsion or an aqueous dispersion of a synthetic resin and chitosan; and (2)
An antibacterial sheet is provided, wherein the coating agent according to (1) is applied to a sheet-like substrate or a film-like substrate.

In the above coating agent, the synthetic resin is a kind selected from the group consisting of a copolymer containing an unsaturated carboxylic acid as a monomer component and an ionomer partially or completely neutralized by a metal ion of the copolymer. The above synthetic resin is more preferable, and the chitosan is 15 to 70 parts by mass based on 100 parts by mass of the synthetic resin.
It is more preferable that the components are blended so as to have a ratio of parts by mass.

Further, the synthetic resin is at least one synthetic resin selected from the group consisting of an ethylene-α, β unsaturated carboxylic acid copolymer and an ionomer partially or completely neutralized by a metal ion of the copolymer. It is more preferable that the synthetic resin is an acrylic resin containing acrylic acid or methacrylic acid as a monomer component.

Hereinafter, the present invention will be described in more detail. The coating agent of the present invention contains an emulsion or an aqueous dispersion of a synthetic resin and chitosan.

Here, the chitosan used in the present invention can be obtained, for example, by hydrolyzing chitin in an alkali and removing an acetyl group in the chitin. Although the degree of deacetylation of chitosan is not particularly limited, the degree of deacetylation is such that water-soluble chitosan can be obtained in consideration of the miscibility in the coating agent of the present invention.
~ 60% is preferred.

The type of the synthetic resin contained in the coating agent of the present invention is not particularly limited as long as it can be used as an emulsion or an aqueous dispersion and can be used as a coating agent. Considering the properties, heat sealing properties, etc., the above synthetic resin is a copolymer containing an unsaturated carboxylic acid as a monomer component, or partially neutralized or completely neutralized with a metal ion of a copolymer containing an unsaturated carboxylic acid as a monomer component. Preference is given to sum ionomers, which may be used alone or in combination of two or more.
More than one species can be used in appropriate combination.

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

In the present invention, among the above synthetic resins, ethylene-α, β-unsaturated carboxylic acid copolymer, ethylene-α
Ionomers of partially or completely neutralized α, β unsaturated carboxylic acid copolymers with metal ions are preferred,
In particular, a (co) polymer (acrylic resin) containing acrylic acid, methacrylic acid and derivatives thereof as a monomer component is more preferable. In the present invention, the term “copolymer” is not limited to those composed of two types of monomers, but also includes terpolymers composed of three or more types of monomers.

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

In the coating agent of the present invention, the amount of the chitosan and the synthetic resin is not particularly limited, but the coating layer formed by the coating agent of the present invention contains chitosan in the synthetic resin. Considering that it is assumed to be dispersed in a sea-island shape,
The chitosan is used in an amount of 15 per 100 parts by mass of the synthetic resin.
It is preferable that the compounding agent be blended so as to have a ratio of up to 70 parts by mass. If the compounding ratio of chitosan is too low, sufficient antibacterial properties will be required unless measures such as mixing of surfactants, stirring methods, coating methods and selecting resins are used to increase the surface area of chitosan exposed on the coating layer surface. May not be obtained. On the other hand, if the proportion of chitosan is too high,
After being used as a coating agent, the coating may be peeled off or dissolved by water. Here, for example, when the coating agent of the present invention is applied to a film-like substrate or the like, in consideration of the appearance of the film after coating, in the coating agent, the chitosan is 15 to 100 parts by mass of the synthetic resin. It is more preferable that it is blended at a ratio of 40 parts by mass.

The amount of the synthetic resin and chitosan to be added to the entire coating agent of the present invention is not particularly limited.
In consideration of the antibacterial effect and the like, the above synthetic resin is usually 0.1 to 20% by mass, especially 1 to 10% by mass, based on the whole coating agent.
Mass%, chitosan is 0.02 to 2 mass%, particularly 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 dispersing aid. Within the range not hindered, in addition to the above essential components, various components usually blended in a coating agent can be blended in a usual dose, if necessary. Such components include, for example, a surfactant, a thickener, and an ultraviolet absorber. Agents and the like can be blended.

The method for producing the coating agent of the present invention is not particularly limited, and it can be produced by a known method. For example, as a method for preparing an emulsion of the synthetic resin, the monomer component of the synthetic resin is used. And a polymerization catalyst commonly used for the monomer component and an appropriate type of surfactant and water, and a method of emulsion-polymerizing the same by a conventional method.Examples of the method for preparing the synthetic resin dispersion include: The above synthetic resin is put into water in the presence of an alkali such as sodium hydroxide (NaOH), potassium hydroxide (KOH) or aqueous ammonia (NH ₄ OH), and heated and pressurized at 100 ° C. or more in an autoclave, for example. A method of dispersing the resin in water by stirring can be used. Alternatively, an aqueous dispersion of a resin commercially available under a trade name such as Seixen (manufactured by Sumitomo Seika Co., Ltd.) or Chemipearl (manufactured by Mitsui Chemicals, Inc.) can also be used.

When the emulsion or dispersion of the synthetic resin is mixed with chitosan, the chitosan is mixed with an aqueous solution having an appropriate concentration (usually about 0.5 to 5% by mass) while stirring the emulsion or dispersion. It is preferable to add the chitosan aqueous solution thus prepared and to stir the mixture under a normal stirring condition of the apparatus using, for example, a chemical stirrer or a magnetic stirrer until the whole becomes uniform.

The coating agent of the present invention is not particularly limited in its coating substrate, and can be applied to various substrates. In particular, when the coating agent is applied to a sheet substrate or a film substrate, it is effective. It is.

The antibacterial sheet of the present invention is obtained by applying the above coating agent to a sheet-like substrate or a film-like substrate, and the type of the sheet-like substrate or the film-like substrate is particularly limited. Instead, for example, a synthetic resin sheet or film, nonwoven fabric, aluminum foil, paper, or 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. Incidentally, the antibacterial sheet of the present invention is not limited to a sheet shape, a film shape,
It includes a tape shape and the like.

The coating amount of the above-mentioned coating agent in the antibacterial sheet of the present invention is not particularly limited, and can be an arbitrary coating amount.
m, especially 5 to 20 μm. If the coating thickness is too thin, the coating may be uneven, and sufficient antibacterial properties may not be obtained.If the coating thickness is too thick, no further improvement in antibacterial properties may be obtained, which may be uneconomical. .

The method for producing the antibacterial sheet of the present invention is not particularly limited. For example, the coating agent is uniformly applied to the surface of the sheet-like substrate or the film-like substrate by a spray coater, a gravure coater, a roll coater or the like. After that, if necessary, the coating is dried for about 5 to 10 minutes under a heating condition of 80 to 130 ° C. to remove moisture from the coating agent and to cure the coating agent, whereby an antibacterial sheet can be obtained.

[0028]

The coating agent of the present invention has sufficient antibacterial properties. For example, a packaging material in which the coating agent of the present invention is coated on a film-like substrate has a heat-sealing property on the film-like substrate. Can be heat-sealed even after coating, and thus can be used for food packaging, medical packaging, and the like by forming a package. Further, for example, by coating the coating agent of the present invention on a sheet-like substrate such as nonwoven fabric or paper, it is possible to impart stability to water, so that it is separated from meat, fish, etc., and drip liquid flowing out. It can be suitably used also for the purpose of suppressing the growth of bacteria and maintaining the freshness of food for a long period of time.

Therefore, the antibacterial sheet of the present invention suppresses the growth of bacteria against drip liquids separated and effluent from, for example, food packaging, medical packaging, meat, fish, etc., and maintains the freshness of food for a long period of time. It is useful as a holding sheet or the like.

[0030]

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

Example 1 An ionomer obtained by neutralizing an ethylene-acrylic acid copolymer (acrylic acid content: 20% by mass) with a Zn ion (neutralization degree: 20%) was mixed with water to obtain a solid of the ethylene-acrylic acid copolymer. By stirring in an autoclave at 130 ° C. under heating and pressure for 30 minutes in the presence of ammonia so as to be 25% by mass, an ionomer dispersion is prepared by dispersion, and the ionomer dispersion is stirred. While water-soluble chitosan (deacetylation degree 46%, "Koyo Chitosan DA
C-50 "(manufactured by Koyo Chemical Co., Ltd.) in an aqueous solution having a concentration of 1%, and the above-mentioned ionomer 100
Chitosan was blended so as to be 15 parts by mass with respect to parts by mass and stirred until the whole became uniform to prepare a coating agent, and this coating agent was used as a polyethylene terephthalate film substrate (film thickness 125 μm).
Is applied to a thickness of 10 μm after drying, and 9
After drying at 0 ° C. for 10 minutes, the antibacterial sheet of Example 1 was obtained.

Example 2 The antibacterial sheet of Example 2 was prepared in the same manner as in Example 1 except that the mixing ratio of the water-soluble chitosan was 20 parts by mass with respect to 100 parts by mass of the ionomer. I got

Example 3 The antibacterial sheet of Example 3 was prepared in the same manner as in Example 1 except that the mixing ratio of the water-soluble chitosan was 40 parts by mass with respect to 100 parts by mass of the ionomer. I got

Example 4 In Example 1, instead of the ionomer dispersion, a (meth) acrylate-acrylic acid copolymer (acrylic acid content: 3.5% by mass, “Almatex K271”) was used. Using an acrylic resin emulsion obtained by mixing and dispersing 20% by mass of water (manufactured by Mitsui Chemicals, Inc.) into water, the aqueous chitosan aqueous solution was mixed with 100 parts by mass of the acrylic resin. An antibacterial sheet of Example 4 was obtained in the same manner as in Example 1, except that the blending was carried out so as to be 15 parts by mass.

Reference Example 1 The antibacterial sheet of Reference Example 1 was prepared in the same manner as in Example 1 except that the mixing ratio of the water-soluble chitosan was 10 parts by mass with respect to 100 parts by mass of the ionomer. I got

Comparative Example 1 The ionomer dispersion used in Example 1 was applied to a polyethylene terephthalate film substrate (film thickness 125 μm) so that the film thickness after drying was 10 μm, and 90 ° C. At 10
After drying for a minute, a sheet of Comparative Example 1 was obtained.

Comparative Example 2 In Comparative Example 1, except that the emulsion of the acrylic resin used in Example 4 was used instead of the ionomer dispersion,
In the same manner as in Comparative Example 1, a sheet of Comparative Example 2 was obtained.

Comparative Example 3 Only the polyethylene terephthalate film substrate used in Example 1 was used as the sheet of Comparative Example 3.

Examples 1 to 4, Reference Example 1 and Comparative Example 1
The antibacterial effects of the sheets Nos. 1 to 3 were evaluated by the following method. Table 1 shows the results.

<Evaluation Method of Antibacterial Effect> Two kinds of test bacterial strains used in the experiment for confirming the antibacterial effect were prepared: Staphylococcus aureus IFO 12732 and Escherichia coli IFO 3972. First, the test bacterium was transferred to an NA medium (normal agar medium) and cultured at 35 ± 1 ° C. for 24 hours. The test bacterium was transferred again to the NA medium and further cultured at 35 ± 1 ° C. for 20 hours. Next, one loop of the cultured test bacteria was transplanted to a 1 / 500NB medium (normal broth medium) and uniformly dispersed to obtain a bacterial solution for inoculation.

Samples were prepared by cutting the sheets of Examples 1 to 4, Reference Example 1 and Comparative Examples 1 to 3 into squares of 50 mm square.
After the above-mentioned bacterial solution for inoculation (0.3 ml (including about 3 × 10 ⁵ bacteria)) was dropped on the coated surface (one surface in Comparative Example 3), a sterilized CPP film was put on the solution and brought into close contact therewith. It was stored for 24 hours under the conditions of ± 1 ° C. and a relative humidity of 90% or more. After storage, the bacteria adhering to the film covered with the test piece are sufficiently washed out, and the number of viable bacteria in 1 ml of the washed liquid is determined by using the desoxycholate medium "Eiken Chemical Co., Ltd." Then, the number of viable bacteria was measured by the agar plate medium method using the Staphylococcus medium "Eiken Chemical Co., Ltd.", multiplied by 10, and the obtained value was converted into the number of viable bacteria per test surface. And the viable cell count 24 hours later.

[0042]

[Table 1]

Next, the antibacterial sheets of Examples 1 to 4 were evaluated for stability against water and heat sealability by the following methods.

<Evaluation Method of Stability to Water> After the antibacterial sheets of Examples 1 to 4 were immersed in water at 20 ° C. for 24 hours, the appearance of each sheet was visually observed to determine whether the coating was peeled off. Or, when it was confirmed whether or not the antibacterial sheets of Examples 1 to 4 were dissolved, no dissolution or peeling was observed, and it was confirmed that they were stable to water. On the other hand, for comparison, the antibacterial sheet in which only the water-soluble chitosan was coated on the polyethylene terephthalate film had the coating layer swelled in water, and the coating layer had been dissolved 24 hours later.

[Examples 5 to 8] In the above Examples 1 to 4, the film substrate was changed to a laminated film composed of nylon (25 μm) / urethane-based adhesive / polyethylene (50 μm). Except having applied the coating agent, it carried out similarly to Examples 1-4, and obtained the antimicrobial sheet of Examples 5-8. This antibacterial sheet was heat-sealed under the following conditions so that the coated surfaces overlap each other, and the heat-sealing strength was determined by the following measurement method. Table 2 shows the results.

<Evaluation method of heat sealability> Heat seal conditions Heat seal temperature: 150 ° C. Heat seal time: 1 second Heat seal pressure: 2 kg / cm ² Measurement method (JIS Z 0238) Tensile speed: 300 mm / min Measurement Environment: temperature 23 ° C, humidity 55% RT

[0047]

[Table 2]

Example 9 The antibacterial sheet of Example 9 was prepared in the same manner as in Example 3 except that the coating agent was applied to a nonwoven fabric of polypropylene instead of the film made of polyethylene terephthalate. I got

Example 10 The antibacterial activity of Example 10 was the same as in Example 3 except that the above coating agent was applied to aluminum foil instead of the film made of polyethylene terephthalate. I got a sheet.

Comparative Example 4 Only the nonwoven fabric used in Example 9 was used as the sheet of Comparative Example 4.

Comparative Example 5 Only the aluminum foil used in Example 10 was used as the sheet of Comparative Example 5.

The sheets of Examples 9 and 10 and Comparative Examples 4 and 5 were evaluated for the antibacterial effect in the same manner as in the above Examples. Table 3 shows the results.

[0053]

[Table 3]

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09D 105/08 C09D 105/08 123/08 123/08 133/00 133/00 133/02 133/02 157 / 10 157/10 // C08L 101: 00 C08L 101: 00 (72) Inventor Eisaku Hirasawa 1-4-16 Nibashi Bakurocho, Chuo-ku, Tokyo F-term in Fujimori Kogyo Co., Ltd. 4F006 AA12 AA35 AB03 AB13 AB24 4H011 AA02 BA01 BB08 BB19 BC19 DA17 DD07 DH02 DH10 DH25 4J038 BA112 CB061 CB141 CG141 CJ011 GA06 HA176

Claims (6)

[Claims] 1. A coating agent comprising an emulsion or an aqueous dispersion of a synthetic resin and chitosan. 2. The synthetic resin is at least one synthetic resin selected from the group consisting of a copolymer containing an unsaturated carboxylic acid as a monomer component and an ionomer partially or completely neutralized by a metal ion of the copolymer. The coating agent according to claim 1. 3. The coating agent according to claim 1, wherein the chitosan is blended in an amount of 15 to 70 parts by mass with respect to 100 parts by mass of the synthetic resin. 4. The synthetic resin is at least one synthetic resin selected from the group consisting of an ethylene-α, β unsaturated carboxylic acid copolymer and a partially or completely neutralized ionomer of a metal ion of the copolymer. The coating agent according to claim 1, 2 or 3. 5. The coating agent according to claim 1, wherein the synthetic resin is an acrylic resin containing acrylic acid or methacrylic acid as a monomer component. 6. An antibacterial sheet obtained by applying the coating agent according to claim 1 to a sheet-like substrate or a film-like substrate.