JP3333791B2 - Antibacterial resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Molded articles made of synthetic resin are
Although it has relatively good mold resistance, it can be used for sheets attached to the surface of various building materials, filters used for air purifiers and air conditioners, shoe insoles, and sheets placed on the wood surface and inside furniture. It is known that various antifungal agents or antibacterial agents are sometimes added to impart a growth inhibiting effect on mold.

However, in a conventional antibacterial resin composition or a molded product obtained by simply adding an antibacterial agent to a synthetic resin such as a polyolefin resin, a growth inhibitory effect against fungi is recognized. However, no growth inhibitory effect against Escherichia coli and other bacteria is observed.

Therefore, as an antibacterial resin composition having a sufficient inhibitory effect against a wide range of bacteria such as described above, a bactericidal effect has been disclosed as disclosed in, for example, JP-A-62-241939. A polyolefin-based resin composition containing a zeolite holding a metal has been proposed.

Further, in Japanese Patent Application Laid-Open No. 4-142349, silver,
After supporting an antibacterial metal selected from copper and zinc on calcium phosphate, calcium carbonate, calcium silicate and a calcium-based ceramic selected from hydroxyapatite, the ceramic is fired at 800 ° C. or higher, and the fired material is fired. An antibacterial resin composition mixed with a polyolefin resin has been proposed.

[0006]

However, when the above-mentioned conventional antibacterial zeolite and antibacterial ceramic are uniformly dispersed in a thermoplastic resin such as a polyolefin resin together with a dispersant, the silver ion in the antibacterial agent and the dispersant become dissociated. Reacts to form a silver salt, causing a problem that the resin is thermally discolored.

[0007]

According to the present invention, there is provided an antibacterial resin composition comprising an antibacterial particle comprising amorphous calcium phosphate having an antibacterial metal ion mixed with a polyolefin resin. It is characterized by being.

The antibacterial particles are contained in a slurry containing amorphous calcium phosphate (ACP) particles in an amount of 50% by weight or less in an antibacterial metal powder, an antibacterial metal compound, or These antibacterial metal ions are adsorbed to ACP particles by mixing these aqueous solutions and performing ion exchange or the like. Further, a mixture obtained by mixing the above antibacterial metal ions into a slurry may be granulated by a spray drying granulation method or the like to obtain antibacterial particles.

The slurry is prepared by adding 0.1 to 10% by weight of a weakly alkaline or neutral water-soluble polymer dispersant, for example, a weakly alkaline ammonium triacrylate, to a calcium hydroxide suspension under stirring. Preferably 0.1-3
After adding a weight% to obtain a mixed solution, the mixed solution under stirring is adjusted to a pH of 10 to 5 by dropping of an aqueous phosphoric acid solution, thereby containing ACP particles having a particle size of about 0.1 μm or less.

The above-mentioned ACP particles were obtained by analyzing 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. In addition, since the ACP fine particles contain water of crystallization, they are considered to be electrostatically active substances, and are presumed to be easy to adsorb various bacteria and viruses.

In order for the obtained antibacterial particles to have a large specific surface area, the ACP particles of the slurry should have a particle size of 0.1 μm or less. The particle size of the powder is desirably 20 μm or less. In addition, it is desirable that the slurry and the antibacterial metal powder, antibacterial metal compound powder or antibacterial metal aqueous solution to be added are mixed at room temperature.

On the other hand, if the amount of ACP particles in the slurry is 90% by weight or more, the viscosity of the slurry becomes high, so that the mixing property at the time of adding the antibacterial metal ion is deteriorated, causing a problem. , Making it unsuitable for granulation. In addition,
When granulating, the content of ACP particles in the slurry should be 1
By changing the amount in the range of 90% by weight, antibacterial particles having a desired average particle size can be obtained.

In the granulation method, the particles obtained are as follows:
It is not particularly limited as long as it is porous and has a substantially spherical shape with a particle size of 200 μm or less, and a specific surface area of 10 m ² / g or more.For example, it is possible to use a spray drying granulation method. Alternatively, a granulation method of crushing after freeze-drying, or a high-speed stirring type granulation method may be used.

As antibacterial metals, gold, silver, zinc, copper,
At least one metal selected from tin, lead, arsenic, platinum, iron, antimony, nickel, aluminum, barium, cadmium, and manganese, a mixture thereof, a metal compound thereof, and an aqueous solution thereof can be used.

Examples of the polyolefin resin include high-density polyethylene, low-density polyethylene, medium-density polyethylene, ethylene-propylene copolymer, ethylene-butene-1 copolymer, polypropylene, and propylene-butene-1.
Copolymer, polybutene-1, poly4-methylpentene-1, or EVA resin (copolymer of ethylene and vinyl acetate)
And the like.

The antimicrobial resin composition of the present invention comprises a dispersant, a matting agent, a deodorant, a coloring agent, an ultraviolet absorber,
An infrared absorber, a flame retardant, a fluorescent whitening agent, another ion adsorbent, another antibacterial agent and the like can be contained according to the purpose.

Further, as a dispersant, powdered paraffin, polyethylene wax, sodium stearate,
Fatty acid metal salts such as magnesium stearate, barium stearate, zinc stearate, calcium stearate, and aluminum stearate; fatty acid amides such as ethylenebisstearamide, methylenebisstearamide, and stearamide; polysiloxane compounds; and Sodium dodecylbenzenesulfonate, C _{6 to} C ₁₂ α-olefin sodium sulfonate, sodium oleate,
Anionic surfactants such as fatty acid metal salts such as sodium laurate can be used. Note that the present invention is not limited to these.

In order to form a molded article of the antibacterial resin composition of the present invention, antibacterial particles are mixed with polyolefin resin in a range of more than 0 to 10% by weight, and other additives are added to Henschel. The mixture obtained by blending with a blender such as a mixer or a tumbler is uniformly melt-kneaded by an extruder or the like, and then poured into a mold by an appropriate means and cooled. Instead of the extruder, it is also possible to perform melt mixing using a dissolution stirrer, a kneader, a Banbury mixer, or the like.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG. The antibacterial resin composition is obtained by heating and melting a polyolefin resin such as low-density polyethylene or polypropylene, and kneading the polyolefin resin with antibacterial particles. When the antimicrobial particles are kneaded in this way, a dispersant such as magnesium stearate is appropriately added to uniformly disperse the antimicrobial particles.

The antibacterial particles are obtained by adsorbing silver ions as antibacterial metal ions to amorphous calcium phosphate (ACP) particles.

The method for producing the antibacterial particles will now be described. First, 0.5% by weight of ammonium triacrylate as a weakly alkaline water-soluble polymer dispersant is added to a suspension of calcium hydroxide under stirring. After obtaining a mixed solution, the above-mentioned mixed solution under stirring was adjusted to pH 10 by dropwise addition of a phosphoric acid aqueous solution, so that the particle size was about 0.1 μm.
A slurry containing the following ACP fine particles was obtained. The particle size of the ACP fine particles in the slurry could be reduced to about 0.1 μm or less by adding the water-soluble polymer dispersant.

The above slurry was diluted with ion-exchanged water, and AC was prepared so that the concentration of ACP became 20% by weight.
A P slurry was obtained. Anhydrous silver nitrate powder dissolved in ion-exchanged water was added to the ACP slurry at 0.1,
The respective mixtures were mixed so as to be 0.5, 0.7, 1.0, and 10.0 mol%, and stirred for 1 hour with a stirring motor to obtain each mixture slurry. In order to convert the above mol% to weight%,
The conversion factor of 1.07 should be added to the mol% value.

As shown in FIG. 1, the mixture slurry 3 containing the ACP particles 1 and the silver ions 2 is supplied to a metering pump 4.
Spray dryer (L-8 manufactured by Okawara Kakoki Co., Ltd.)
5 Atomizer 6 for spray dryer 5
Was rotated at a high speed, and the mixture slurry 3 was sprayed into a hot air flow for drying in a spray drier 5 to perform granulation and drying by a spray granulation method.

Silver ion-containing AC obtained by granulation drying
The substantially spherical antibacterial particles 7 which are P fine powders are
As a result, a sample having an average particle size of 12 μm was collected. At this time, the ultrafine powder that could not be collected by the cyclone 8 was separately collected by a bag filter (not shown).

The operating conditions in the above spray drying granulation were as follows. The feed 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 such that the inlet temperature of the hot gas chamber 11 is 200-2
At 50 ° C., the outlet temperature at the discharge hole 12 connected to the cyclone 8 was controlled so as to always exceed 100 ° C., and the rotation speed of the atomizer 6 was set in the range of 10,000 to 37,000 rpm.

Further, using two types of spray dryers (FOC-20, OD-25G, FOC-25, OC-25 manufactured by Okawara Kakoki Co., Ltd.) obtained by scaling up the spray dryer 5, the slurry supply amount was 100 kg. / hr, and the other conditions were the same as in the above to prepare composite particles.
As a result, antibacterial particles similar to antibacterial particles 7 were obtained. The antibacterial particles 7 thus obtained were truly spherical.

The antibacterial particles 7 obtained above were examined by X-ray powder diffraction for the formation phases of the antibacterial particles 7, and although not shown, the obtained antibacterial particles 7 were found to be calcium phosphate [Ca ₃ (PO ₄ ) ₂ .nH ₂ O] and silver. Also, the broad X-ray diffraction pattern indicates that calcium phosphate is amorphous.

It was also identified that the antibacterial particles 7 incorporated silver ions into calcium phosphate and formed a solid solution state of both. In other words, it is assumed that silver ions are incorporated in the microcrystals of calcium phosphate and at the positions of calcium ions.

Next, the specific surface area of each of the obtained antibacterial particles 7 was measured. Their specific surface areas were measured by the BET method. As a result, the specific surface area of each antibacterial particle 7 was in the range of 100 to 110 m ² / g.

Next, the antibacterial particles 7 having silver ions so as to be 0.1 and 0.5 mol% obtained above, and commercially available antibacterial apatite particles (with a silver ion content of 2% by weight) And the antibacterial properties were examined.

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

2. Antibacterial test (shake flask method) 0.1 g of each antibacterial particle 7 was weighed as a sample, put into a 200 ml Erlenmeyer flask containing 100 ml of the above-mentioned phosphate buffer, and about 10 ⁵ cells were added to the suspension of the test bacteria. After the addition, the Erlenmeyer flask was shaken while keeping it at 25 ° C. ± 5 ° C., and the number of bacteria in the Erlenmeyer flask was measured over time. The strains used are as follows.

Escherichia coli (Escherichia coli) IFO-12734 Staphylococcus aureus (Staphylococcus aureus) IFO-12732 Psedomonas aeruginosa (Pseudomonas aeruginosa) IFO-12689 Candida albicans (Candida) IFO-1060 Media used Bacteria: Mueller Hinton 2 (BBL) ) Fungus: Potato dextrose agar medium (Eiken) The results of the above measurements are shown in Tables 1-4.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

[0037]

[Table 4]

As described above, the antibacterial particles 7 of the above embodiment are
The antibacterial effect was higher than that of the apatite composite particles commercially available as conventional antibacterial particles. This is because the antibacterial particles 7 of each of the above examples are porous, so that the specific surface area, which is the area in contact with the bacteria, is large, and the ACP used as the base material has a high bacterial adsorption capacity (Asahi Shimbun, (See evening paper, January 16, 1993).

Further, since such antibacterial particles 7 are spherical, they are easily dispersed uniformly when blended into a resin molded product such as a foamed plastic tray on which fresh food is placed. The mixing property with respect to the product can be improved as compared with the related art.

Next, it is assumed that the antibacterial particles 7 are blended into a plastic sheet and used in the white tray such as a foamed plastic tray on which fresh food is placed. From this, the compounded antibacterial particles 7
Is colored, for example, brown, there is a possibility that the user may mistakenly recognize that dust or dirt is attached to the tray.

Therefore, an antimicrobial resin composition using the antimicrobial particles 7 having silver ions so as to be 0.5 mol% and commercially available antimicrobial apatite particles (with a silver ion content of 2% by weight) is used. Each of the products was prepared, a plate was prepared from the antibacterial resin composition by injection molding, and the color difference of the plate was measured.

First, as a sample 1, a low-density polyethylene
A masterbatch was prepared by kneading (180 to 230 ° C.), extruding and pelletizing 85% by weight, 10% by weight of magnesium stearate as a dispersant, and 5% by weight of the above antibacterial particles 7 containing 0.5 mol% of silver ions. Using the above masterbatch, a plate was produced by injection molding at 210 ° C.

Next, as Sample 2, 85% by weight of polypropylene and 10% by weight of zinc stearate as a dispersant were added.
5% by weight of 5 mol% silver ion-containing antibacterial particles 7 were kneaded (180-230 ° C.), extruded and pelletized to prepare a master batch. Using the above masterbatch, a plate was produced by injection molding at 210 ° C. The addition of the above dispersant is effective for uniformly dispersing the antibacterial particles 7.

Subsequently, as Comparative Example 2, polypropylene
85% by weight, 10% by weight of zinc stearate as a dispersant, 5% by weight of commercially available antibacterial apatite particles (with a silver ion content of 2% by weight) and kneading (180-230 ° C)
A master batch was prepared by pelletizing. Using the master batch, a plate was prepared by injection molding at 210 ° C.

Next, the method of measuring the color difference of each of the above plates will be described. The plates of Samples 1 and 2 and Comparative Example 2 are connected to low density polyethylene (LDP) as a blank.
A plate made of E) and polypropylene (PP) was used. Each of the above plates is measured using an integrating sphere color difference meter (ND-100P).
, Manufactured by Nippon Denshoku Industries Co., Ltd.), using the reflection method and the transmission method.

[0046]

[Table 5]

[0047]

[Table 6]

As is clear from Tables 5 and 6, Samples 1 and 2 were found to have the same whiteness as their respective blanks. However, it was found that the plate of Comparative Example 2 turned brown.

Thus, the antibacterial resin composition using the antibacterial particles 7 is colorless even when heated during kneading, so that a commercially available plastic container or a sheet-like plastic container can be used. Even if it is used for plastic, it is possible to prevent the antibacterial particles 7 from being erroneously recognized as dirt.

Therefore, when the antibacterial resin composition of the above embodiment is used in a plastic container, the antibacterial particles 7 can be exposed on the surface of the container, so that the antibacterial resin composition can be used on foods placed in the plastic container. The growth of various bacteria can be suppressed, and the appearance of the plastic container can be prevented from deteriorating.

From the above, the antibacterial resin composition is
It can improve the shelf life of fresh foods, has the effect of preventing food poisoning due to foods grown with various germs, and is also suitably used for a tray and the like that also has the effect of maintaining the freshness of agricultural products such as mushrooms and fruits. Can be.

Incidentally, hydroxyapatite adsorbing and carrying antibacterial metal ions is known as antibacterial apatite particles. When the antibacterial particles are added to the slurry and used in water or come into contact with a substance having a large amount of water, the antibacterial metal ions are eluted and the antibacterial properties are deteriorated. It was discolored to brown or the like when illuminated by light.

When the antibacterial apatite particles obtained as described above are treated at a high temperature, the elution of antibacterial metal ions can be suppressed, but the antibacterial activity is reduced, and particularly, the antibacterial activity against Staphylococcus aureus and the like is reduced. Antimicrobial metals such as low silver lack antimicrobial efficacy.

However, in the antibacterial particles 7, no elution of antibacterial metal ions was observed, and no discoloration due to sunlight or fluorescent light was observed. Thereby, even if the antibacterial particles 7 are added to the inner surface of a food tray or the like,
There is no danger that the user will mistakenly recognize that dust or dirt is attached.

In the above embodiment, the example in which the antibacterial particles 7 are granulated and used is described. However, the above-mentioned slurry mixed with antibacterial silver ions is simply dried to form a silver ion-containing ACP.
Fine particles may be used.

Further, in the above-described embodiment, an example in which the antibacterial resin composition is used for a food tray or a mounting tray has been described. However, the present invention can be used for a molded article requiring antibacterial properties. Surface materials, air conditioner interior materials, refrigerator surface materials, electric washing machine surface materials, centrifugal tub inner and outer surface coating materials, medical equipment cases and medical saucers, dishes such as cups and saucers, foods such as fresh foods Can be suitably used for a transfer tray or the like.

[0057]

As described above, the antibacterial resin composition of the present invention has a constitution in which antibacterial particles composed of amorphous calcium phosphate having antibacterial metal ions are mixed with a polyolefin resin.

Therefore, the above structure can maintain a white color even when heated when mixed with a polyolefin-based resin, so that it is prevented from discoloring to brown or the like when heated as in the prior art, and the antibacterial property is prevented. The particles are prevented from being mistakenly recognized by the user as dirt or the like. In addition, the above-described configuration can exhibit high antibacterial properties due to amorphous calcium phosphate capable of adsorbing bacteria, and thus has an effect that it can be suitably used for a loading tray or the like on which foods such as fresh foods are placed.

[Brief description of the drawings]

FIG. 1 is a schematic structural view of a spray drier used for producing antibacterial particles used in the antibacterial resin composition of the present invention.

[Explanation of symbols]

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

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C08L 23/00-23/36

Claims (1)

(57) [Claims] 1. An antimicrobial resin composition comprising antimicrobial particles comprising amorphous calcium phosphate having antimicrobial metal ions mixed with a polyolefin resin.