JPS63154746A - Antibacterial film - Google Patents

Abstract

PURPOSE:To obtain a sufficiently antibacterial film safely in food sanitation, by dispersing specified solid zeolite particles having antibacterial metal ions and a moisture absorbent in a synthetic resin. CONSTITUTION:An antibacterial film prepared by dispersing solid zeolite particles having antibacterial ion-exchanged metal ions, a specific surface area >=150m<2>/g and an SiO2 to Al2O3 molar ratio <=14 and a moisture absorbent. Examples of said particles which can be desirably used include those of zeolite A, zeolite X, zeolite Y, clinoptiolite and mordenite. Examples of said antibacterial metal ions include those of silver, copper and zinc. Examples of said moisture absorbents include calcium chloride, sodium chloride, potassium carbonate, magnesium sulfate and cane sugar.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a film having antibacterial properties, particularly suitable for food packaging.

[Prior Art 1] Conventionally, as an antibacterial film, there is an ilm in which a bactericide is dispersed in a thermoplastic synthetic resin. For example, in the 1980s
No. 142771 describes an antibacterial packaging film in which a diphenyl ether-based fungicide and/or a chlorhexidine-based fungicide is kneaded into vinylzoline chloride resin.

[Problem to be solved] In the above conventional technology, the disinfectant is dispersed and held in the thermoplastic synthetic resin, and the disinfectant migrates from the thermoplastic synthetic resin to the film surface and develops antibacterial properties. This is the mechanism of action. Therefore, when used in food packaging materials, etc., the disinfectant comes into direct contact with the food, which poses a problem in terms of food hygiene safety.

[Means for Solving the Problems] The present invention solves the above problems and provides an antibacterial film having sufficient antibacterial properties. That is, the present invention has a specific surface area of 150 m/g or more and a Si
This is an antibacterial film characterized by containing zeolite solid particles having a molar ratio of 02/All 203 and a moisture absorbent dispersed in a synthetic resin.

In the antibacterial film of the present invention, activated carbon is generated little by little by the catalytic action of the metal ions held by the zeolite solid particles, and it is thought that this active oxygen is the mechanism by which the antibacterial effect is exerted.

Therefore, it is safe with almost no toxicity, and its effect can be maintained as long as the metal ions are not used up.

The present inventor has discovered that the presence of a moisture absorbent together with antibacterial zeolite further improves the antibacterial effect. The generation of active oxygen through the catalytic action of metal ions requires
Moisture and oxygen are necessary, although in small amounts, and the moisture absorbent is thought to play a role in providing this moisture. Moisture appears to be necessary for the release of metal ions retained in the zeolite solid by ion exchange. Although zeolite itself is hygroscopic, it was unexpected that the antibacterial properties would be improved by adding a hygroscopic agent. It is also believed that by making the particulate moisture absorbent exist in the synthetic resin together with the zeolite solid particles, fine gaps are present in the film, and oxygen is rapidly supplied from the air.

In other words, the hygroscopic agent not only supplies moisture to the zeolite solid particles, but also forms fine gaps in the thermoplastic synthetic resin to quickly replenish oxygen. can be obtained and exhibit antibacterial properties.

In the present invention, the zeolite that retains metal ions with antibacterial effects through ion exchange (hereinafter simply referred to as zeolites with antibacterial effects) is used in Japanese Patent Application Laid-open No. 58
-7361.

In other words, zeolite 1 solid particles having an antibacterial effect are those in which one or more metal ions having an antibacterial effect are retained in the ion-exchangeable part of natural or synthetic zeolite made of aluminosilicate. Ru. Preferred examples of metal ions with antibacterial effects include silver, copper, zinc, tin,
Mention may be made of lead, bismuth, cadmium, chromium and mercury, preferably silver, copper and zinc. The above metals having antibacterial properties can be used alone or in combination.

Zeolites are generally aluminosilicates with a three-dimensionally developed skeletal structure, generally xM2/ on the basis of 8ρ203. 0・A[2o3-ysi 02
- ZH20-c table was not correct.

M represents an ion-exchangeable metal ion, usually a monovalent to divalent metal, and n corresponds to this valence. On the other hand, X and y each represent a metal oxide, a coefficient of wrinkle strength, and 2 represents the number of crystal water.

Many types of zeolites are known, differing in their composition ratio, pore diameter, specific surface area, etc.

However, the specific surface area of the zeolite solid particles used in the present invention must be 150rd/3 or more (based on anhydrous zeolite), and the 5i02/A203 molar ratio of the zeolite constituents must be 14 or less, preferably 11 or less.

The solution of water-soluble salts of metals with antibacterial activity, such as silver, copper, and zinc, used in the present invention easily undergoes ion exchange with the zeolite defined in the present invention, so this phenomenon can be utilized to obtain the necessary solutions. It is possible to hold the above metal ions alone or in combination in a zeolite stationary phase, but the zeolite particles holding metal ions are
Specific surface area is 150TIt/g or more, Katsu3i 02 /
Two conditions must be met: the A'203 molar ratio is 14 or less. If this is not the case, the object of achieving effective antibacterial action will not be obtained. This is thought to be due to the fact that the absolute amount of metal ions fixed on the zeolite is insufficient in a state where the effect can be exerted. In other words,
This is thought to be due to the physicochemical properties of zeolite exchange groups, such as cloudiness, exchange rate, and accessibility.

Therefore, S! is known as molecular sieve.
Zeolites with a large molar ratio of 02/A,Q203 are completely unsuitable for the present invention.

In addition, in zeolite with a Si 02 /AI2203 molar ratio of 14 or less, it is possible to uniformly retain metal ions having an antibacterial effect, and for this reason, it is only by using such zeolite that a sufficient antibacterial effect can be obtained. It turns out. In addition, zeolite Si 02
The acid resistance and alkali resistance of zeolites with a high silica ratio and a /A9203 molar ratio exceeding 14 increase as 5102 increases, but on the other hand, it takes a long time to synthesize, and from an economical point of view, zeolites with such a high silica ratio It is not a good idea to use Previous) Hot S! Natural or synthetic zeolites with 02/Aρ203≦14 can be used satisfactorily from the viewpoint of acid resistance and alkali resistance in the fields of application normally considered for the present invention, and are inexpensive and advantageous from an economic point of view. . From this point of view as well, the 5102/Aρ2 o3 molar ratio must be 14 or less.

The molar ratio of SiO2/AfJ203 used in the present invention is 1
As the zeolite material of 4 or less, any natural or synthetic olide can be used.

For example, natural zeolite is analcin (Anal
cime: S i 02 / Afl 203 =
3.6-5°6), Chabazit
e: Si 02 /A1203 = 3.2 to 6.
0 and 6.4-7.6), clinoptilolite (C
1inoptilolite: Si 02 /AfJ
203=8.5~10.5), Erionite (Er!
0nlje: S! 02/Af) 203
= 5.13-7.4), Fauja
site: Si 02 / 8 and 203 = 4.2 ~
4.6), mordenite (s)
i02/AfJ203=8.34~10.0>
,Philipsite:S
i02/Afl203 = 2.6~4.4)
etc. These typical natural zeolites are suitable for the present invention. On the other hand, a typical synthetic zeolite is 8-type zeolite (S!02/AfJ203=
1.4~2.4>, X-type zeolite (Si 02
/AfJ203 = 2~3), Y-type zeolite (Si
02 /Aρ203=3~6), to Mordenai 1 (S
i O/An 203 = 9-10), etc.
These synthetic zeolites are suitable as the zeolite material of the present invention. Particularly preferred are synthetic A-type zeolites, X-type zeolites, Y-type zeolites and synthetic or natural mordenites.

The shape of the zeolite is preferably in the form of powder particles, and the particle size may be appropriately selected depending on the application. For example, a few microns to a few 1
0 micron or several hundred microns or more, or 5
It can be less than a micron, especially less than 2 microns.

Metal ions must be retained in the zeolite solid particles through an ion exchange reaction. If it is simply adsorbed or attached without ion exchange, the antibacterial effect and its durability will be insufficient. As a method for retaining metal ions, various zeolites defined in the present invention can be used in A of the present invention.
Taking the case of conversion to g-zeolite as an example, normally /J
- A solution of a water-soluble silver salt such as silver nitrate is used during zeolite conversion, but care must be taken not to increase its concentration too much. For example, when converting A-type or ) By ion exchange, silver ions are replaced with sulfur and lithium ions in the solid phase, and at the same time, silver oxides and the like are precipitated in the same phase of zeolite.

For this reason, the porosity of the zeolite is reduced and the specific surface area is significantly reduced. Furthermore, even if the specific surface area does not decrease significantly, the bactericidal activity decreases due to the presence of silver oxide itself. In order to prevent the precipitation of excess silver into the zeolite phase, the concentration of the silver solution should be diluted, for example 0.3M.
A(] It is necessary to keep NO3 below 0. The safest A!11 NO3 concentration is 0.1M or below.

It was found that when an ACl NO3 solution of such a concentration was used, the specific surface area of the Ag-zeolite obtained was almost the same as that of the zeolite used as the conversion material, and that the antibacterial effect could be exhibited under optimal conditions.

Next, when the zeolites defined in the present invention are converted to CI-zeolite, the same phenomenon as in the case of Ag-zeolite described above occurs depending on the concentration of the copper salt used for ion exchange. For example, when converting 8-type or Since basic precipitates such as Cu3 (S04) (OH)4 are precipitated in the same phase, the porosity of the zeolite is reduced and the specific surface area is significantly reduced. In order to prevent precipitation of excessive copper into the zeolite phase, it is preferable to maintain the concentration of the aqueous preparation used in a more dilute state, for example, at 0.05M or less.

When using a CuSO4 solution with such a concentration, the CL obtained is
It has been found that the specific surface area of I-zeolite is almost the same as that of the converted material zeolide, and that it has the advantage of exhibiting its antibacterial effect in an optimal state.

A () When converting to Zn-zeolite and Cu-zeolite, depending on the concentration of salts used for ion exchange, solids may precipitate in the same phase of the zeolite.However, when converting to Zn-zeolite, This phenomenon is not observed when the salt concentration is around 2 to 3M. Generally, the ZO-zeolite used in the present invention can be easily obtained by using salts having concentrations around the above range.

Ag-zeolite, Cu-zeolite and l
When carrying out the ion exchange reaction in a batch process for conversion to n-zeolite, the zeolite material may be immersed in a salt solution having the above-mentioned concentration. In order to increase the metal content in the zeolite material, the number of batch treatments may be increased. On the other hand, when treating a zeolite material by a column method using a salt solution having the above concentration, the desired metal-zeolite can be easily obtained by filling an adsorption tower with the zeolite material and passing the salt solution through it. can get.

The number of metals occupied in the above metal-zeolite (anhydrous zeolite group Q) is 30% by weight or less for silver,
The preferred range is 0°001 to 5% by weight. - Regarding the copper and zinc used in the hydropower invention, the amount of copper or zinc in the metal-zeolite (based on anhydrous zeolite) is 35% by weight or less, and the preferable range is 0.01 to 15% by weight.
It's in a serious condition. It is also possible to use silver, copper and zinc ions in combination, in which case the total amount of metal ions is 35% relative to the metal-zeolite (anhydrous zeolite group Q).
It may be less than 0.001% to 15% by weight, and the preferable range is determined by the composition ratio of metal ions.

Further, even if metal ions other than those mentioned above, such as sodium, potassium, calcium, or other metal ions, coexist, the antibacterial effect is not hindered, so the residual or coexistence of these ions is not a problem.

The ratio of the metal having a bactericidal effect to the total amount of zeolite (based on anhydrous zeolite) may be 30% by weight or less for silver, and the preferred range is 0.001 to 5% by weight. On the other hand, in the case of copper or zinc, the content is 35% or less, and the preferable range is 0.01 to 15%. When silver, copper and zinc ions are used in combination, the total amount of metal ions is preferably in the range of o, ooi to 15ifi%. Further, there is no problem with the remaining or coexistence of other metal ions.

The content of antibacterial zeolite solid particles holding antibacterial metal ions (based on anhydrous zeolite) is 0.1 to 20% by weight, especially 0.5 to 20% by weight of the weight of the film that has not absorbed water. Preferably, the content is 10%.

As a moisture absorbent, calcium chloride, chloride], lithium,
Magnesium chloride, dibasic sodium phosphate, ammonium chloride, potassium carbonate, potassium alum, magnesium sulfate, sodium nitrate, ammonium sulfate, dibasic ammonium phosphate, potassium bromide, silica gel, zeolite, sucrose, fructose, glucose, sorbitol, multi-1
One or more kinds selected from the group consisting of lactose and lactose can be used. The hygroscopic agent preferably has a moisture content of 0.
It is added to the film as fine particles with a particle size of 1 to 100 microns, especially 1 to 25 microns. The content of the moisture absorbent is preferably 0.1 to 60% by weight based on the total weight of the antibacterial film.

As the synthetic resin, thermoplastic resins such as polyethylene, polypropylene, polyvinyl chloride, polyamide, ethylene vinyl acetate copolymer, saponified ethylene vinyl acetate copolymer, polyester, etc. can be used, but are not limited thereto. The method of dispersing and incorporating antibacterial zeolite-based solid particles and moisture absorbent into a thermoplastic synthetic resin and forming a film is to mix it with the thermoplastic synthetic resin in a heated and molten state using a Banbury type mixer or roller type mixer. A conventional kneading method can be used, and conventional methods such as a T-die method, an inflation method, and a calendar method can be used to form a film.

In addition, in order to impart strength and other functions to the film, it can be multilayered by coextrusion or lamination with other films.

The invention will be further explained below by means of examples.

[Example] The antibacterial zeolite used in the example was Bactekiller A.
3508N (trademark, manufactured by Sinanen New Ceramics)
It is commercially available as. This is a type A zeolite to which triple weight percent silver and 5 weight percent copper are added by ion exchange, and has an average particle size of 5 to 6 μm.

Specific surface area is 500-600/3, S! 02/A
, I) 203 molar ratio is approximately 2.

Example 1 5 parts by weight of zeolite solid particles carrying antibacterial metal ions and 5 parts by weight of magnesium sulfate with a particle size of 10 μm were kneaded into 90 parts by weight of low-density polyethylene using a Banbury type mixer, and then mixed by the inflation method. A film with a thickness of 40μ was obtained.

Example 2 5 parts by weight of zeolite solid particles carrying antibacterial diagonal ions and 50 parts by weight of calcium carbonate having a particle size of 3 μm were kneaded into 45 parts by weight of linear low-density polyethylene using a Banbury type mixer, A film with a thickness of 40 μm was obtained by the inflation method.

Comparative Example 1 Zeolite-based solid particles carrying antibacterial total ions were kneaded into a 95-type low-density polyethylene assembly using a conventional method using a Banbury type mixer, and a film with a thickness of 40μ was obtained by the inflation method. Ta.

Comparative Example 2 Five parts by weight of zeolite solid particles carrying antibacterial metal ions were kneaded into linear low-density polyethylene using a Banbury type mixer in a conventional manner, and a film with a thickness of 40 μm was obtained by an inflation method.

Antibacterial property evaluation experiment 1 In Example 1 and Comparative Example 1, a low-density polyethylene film with a thickness of 40μ was used as a control.
It was cut into pieces of cm x 5 cm and each piece was examined for antibacterial properties.

1) Test strain 5 taphylococcus aureus IF
Ot3276 (Staphylococcus aureus) Escherichia coli IFO3301
(Escherichia coli> 2) Bacterial liquid preparation test After culturing the bacterial strain in an ordinary bouillon medium at 37°C overnight, it was diluted with sterile physiological saline so that the number of bacteria per strain was approximately 106.

3) Test procedure A certain amount of bacterial solution was sprayed onto the surface of the sample piece (5 x 5 cm), and the surface of the sample was wiped with sterile gauze immediately after spraying and after being left at 35°C for 6 hours. Next, the test bacteria adhering to the same gauze were extracted with 5CDLP broth medium (Daigo Nutrient Chemical Co., Ltd.) to prepare a test solution. The number of viable bacteria in this test solution is 5CDLP.
The number of viable bacteria per sample was calculated by the usual pour plate culture method (cultured at 37° C. for 2 days) on an agar medium (Daigo Nutrient Chemical Co., Ltd.).

The results are shown in Tables 16 and 2. The sterilization effect in the table is the formula This is the index calculated by

Table 1 Antibacterial clothing against Staphylococcus aureus 2 Antibacterial experiment against Escherichia coli 2 Films obtained in Example 2 and Comparative Example 2, and thickness 4
5 cm x 0 μ linear low density polyethylene film
It was cut into 5 cm pieces and each piece was examined for antibacterial properties.

The experiment was conducted using Bacillus subtilis (Bacillus StJb) on each film.
tiliS), and black mold (Aspergilfu
S. niger) spores were sprayed on each sample, and the number of surviving bacteria was measured immediately after spraying and after storage at 22°C for 7 days.

The measurements were performed using the following procedure. That is, the bacteria on the surface of each film was washed off in sterile water containing 0.1% Tween 80 (100 Ini), and the number of viable bacteria in this sterilized water was determined using an ordinary agar medium (manufactured by Yoneken Chemical Co., Ltd.) for Bacillus subtilis.
Black mold was measured using potato dextrose agar medium (manufactured by Yoneken Kagaku ■) by a conventional pour plate culture method, and the number of viable bacteria adhering to each film was calculated. The results are shown in Tables 3 and 4.

Table 3 Antibacterial properties against Bacillus subtilis Table 4 Antibacterial properties against black mold [Effects of the invention] A film having excellent antibacterial properties was obtained by the present invention. When food is packaged using the antibacterial film according to the present invention, the growth of microorganisms attached to the film surface is suppressed,
Or it can be sterilized. Therefore, deterioration of food by microorganisms can be suppressed, and the shelf life of food can be extended. In conventional films mixed with disinfectants harmful to food hygiene or preservatives that are food additives, these substances migrate from the film to the film surface and may adhere to food, but with the present invention. This is not the case with this film. Therefore, the antibacterial film of the present invention is food hygienically safe.

Kanebo Co., Ltd. Applicant: Dai Nippon Printing Co., Ltd. Hagiwara Giken Co., Ltd.

Claims (6)

[Claims] (1) Specific surface area of 150 m^2/g or more and 14
An antibacterial film comprising zeolite solid particles having the following SiO_2/Al_2O_3 molar ratio and a moisture absorbent dispersed in a synthetic resin. (2) The zeolite solid particles are A-type zeolite, X-type zeolite
The film according to claim 1, which is composed of type zeolite, Y-type zeolite, clinoptilolite, or mordenite. (3) The film according to claim 1 or 2, wherein the metal ion having an antibacterial effect is one or more metal ions selected from the group consisting of silver, copper, and zinc. (4) Any one of claims 1 to 3, wherein the content of zeolite solid particles (based on anhydrous zeolite) is 0.1 to 20% by weight based on the total weight of the antibacterial film. The film mentioned. (5) The moisture absorbing agent is calcium chloride, sodium chloride, magnesium chloride, dibasic sodium phosphate, ammonium chloride, potassium carbonate, potassium alum, magnesium sulfate, sodium nitrate, ammonium sulfate, dibasic ammonium phosphate, potassium bromide, silica gel , zeolite, sucrose, fructose, glucose, sorbitol, maltitol, and lactose. Films listed in . (6) Claims 1 to 5, wherein the content of the moisture absorbent is 0.1 to 60% by weight based on the total weight of the antibacterial film.
The film described in any one of the paragraphs.