WO2010098309A1

WO2010098309A1 - Composition containing silver nanoparticles, masterbatch containing silver nanoparticles, and molded product thereof

Info

Publication number: WO2010098309A1
Application number: PCT/JP2010/052735
Authority: WO
Inventors: 中島有二
Original assignee: 日本イオン株式会社
Priority date: 2009-02-28
Filing date: 2010-02-23
Publication date: 2010-09-02
Also published as: JPWO2010098309A1

Abstract

A masterbatch which comprises a synthetic resin and silver incorporated therein, the silver being necessary for imparting antibacterial properties. Despite this, when the masterbatch is incorporated into a transparent synthetic resin, the masterbatch impairs neither the transparency characteristic of the transparent synthetic resin nor the preferable properties inherent in the synthetic resin. The masterbatch has excellent profitability and causes no problem concerning safety even when used to produce molded products such as synthetic-resin tablewares. The masterbatch is produced by weighing given amounts of silver lactate and pellets of a raw-material synthetic resin, mixing the ingredients, heating the mixture with stirring at a temperature at which the raw-material synthetic-resin pellets can melt, thereby melting the raw-material synthetic-resin pellets, extruding the melt, and cooling and pelletizing the extrudate.

Description

Silver nanoparticle-containing composition, silver nanoparticle-containing masterbatch and molded article thereof

The present invention relates to a composition containing antibacterial silver nanoparticles, a synthetic resin masterbatch containing silver nanoparticles, and a molded product thereof.

Since silver has antibacterial and bactericidal effects, silver is generally added to and blended with synthetic resins to impart antibacterial properties. However, when adding and blending it, it is difficult to produce a fine powder of silver itself and the cost is high. Therefore, in general, silver is supported on other inorganic fine particles. Is obtained by kneading and blending in a synthetic resin, and as a result, silver is dispersed in the synthetic resin to obtain an antibacterial synthetic resin (Patent Document 1 and Patent Document 2).

Patent Document 1 aims to “provide a method for producing a masterbatch containing an antibacterial agent that does not inactivate silver ions”, and uses soluble glass as a carrier for silver nanoparticles. Yes. Further, Patent Document 2 states that “thermoplastic capable of exhibiting excellent antibacterial properties even when the resin molded body has a bulky shape by effectively utilizing the original antibacterial properties of the inorganic antibacterial agent. The purpose of the present invention is to provide a resin molded article. In the specification, inorganic compounds for supporting antibacterial metal ions include inorganic adsorbents such as activated carbon, activated alumina and silica gel, zeolite, hydroxyapatite, phosphorus Inorganic ion exchangers such as zirconium acid, titanium phosphate, potassium titanate, hydrous bismuth, hydrous zirconium, and hydrotalcite are shown.

Also, a technique using a dispersant has been proposed in order to uniformly disperse silver nanoparticles in a synthetic resin masterbatch (Patent Document 3). Patent Document 3 has an object of “providing an antibacterial coating composition containing 30 PPM nanosilver particles on the surface of an injection preformed article and a coating method of the antibacterial coating”, and in the manufacturing process shown as a solution means, , “Nanosilver particles are dispersed in ethanol at a predetermined concentration to obtain a nanosilver ethanol dispersion liquid”.

Further, Patent Document 4 discloses a technique for uniformly dispersing silver nanoparticles in a masterbatch without using a dispersant or a carrier. In Patent Document 4, as a means for solving the problem, “a predetermined amount of an ultrafine particle material is mixed in a molding base material, the molding base material is melted or cured to be molded into a predetermined shape, and the ultrafine particle material is formed on the molding surface or surface layer portion. In the method for producing a molded article containing an ultrafine particle material, when the molded base material is melted or cured, the mixed ultrafine particle material is passed from the inside to the surface or surface layer of the molded article through a crosslinked network of the molded base material. The method of “dispersing and distributing the ultrafine particle material from the inside to the surface of the molded product or the surface layer through the cross-linked network of the molding substrate” is described. However, there is no specific explanation in the specification, and according to the applicant's knowledge, the ultrafine particle material cannot automatically move to the surface of the molded product through the cross-linked network.

JP 05-255515 A Japanese Patent Application Laid-Open No. 07-252376 JP 2006-9008 A JP 2007-197707 A

By the way, the prior arts and methods disclosed in Patent Documents 1 to 3 have the following problems in addition to the fact that antibacterial properties are not necessarily at a sufficiently satisfactory level. That is,
(1) When a dispersant is used, the components of the dispersant remain in the synthetic resin, which may be harmful depending on the dispersant used, and the silver fine particles are uniform in the synthetic resin. Not distributed.
(2) And when using a carrier,
(A) Since it is difficult to make the particle size of the inorganic particles themselves carrying silver less than or equal to the wavelength of visible light, transparency, which is a feature of the particles, is impaired when blended with a transparent synthetic resin.
(B) Since silver is supported on the inorganic particles, the process is expensive, and the cost of the silver-supported inorganic particles is increased, resulting in high cost of the master batch.
(C) Since silver is blended in the synthetic resin, inorganic particles that do not contribute to imparting antibacterial properties are additionally blended, and the preferable physical properties (for example, impact strength) inherent to the synthetic resin are impaired. There is a case.

Therefore, in the present invention, the silver itself necessary for the expression of antibacterial properties is uniformly dispersed in the synthetic resin, and when blended with the transparent synthetic resin, the characteristic transparency is not impaired, and the synthetic resin originally possesses. It is an object of the present invention to provide a masterbatch that does not impair the preferred physical properties, is excellent in economic efficiency, and does not pose a safety problem even when it is a molded article such as synthetic resin tableware. .

In order to solve the above problems, the present inventor has eagerly studied the possibility from various angles. One of them is, "If a low molecular weight organic silver compound is mixed with a synthetic resin and melted and kneaded, this organic The silver compound is thermally decomposed during kneading, and silver fine particles are formed in the synthetic resin. Therefore, in consideration of the safety after molding, silver lactate made by reacting lactic acid and silver contained in foods often used in daily life (eg cheese, yogurt) (silver lactate itself is easily used as a standard reagent) ) As a candidate organic silver compound. Silver lactate was added to and blended with the pellets of the synthetic resin, kneaded at a temperature at which the synthetic resin melts using a kneading extruder, and extruded into strands to be cut into pellets. When this synthetic resin pellet is observed under a transmission microscope, silver is found to be very finely dispersed (average particle diameter is about 1 nm to 80 nm) and uniformly dispersed in the obtained synthetic resin. There was found. If the ultrafine silver particles are dispersed and present in the synthetic resin in such a form, the synthetic resin is expected to have sufficient antibacterial properties.
Therefore, in order to confirm this, a small plate-shaped molded product generally called a color plate is molded from the obtained synthetic resin pellets by injection molding, and whether or not the plate-shaped molded product has antibacterial properties. As a result of evaluation by a standard method, it was found that antibacterial properties as expected were obtained, and the present invention was achieved. In addition, we have fully clarified why the nanosized ultrafine particles of silver are present in the synthetic resin if silver lactate is mixed with the synthetic resin and kneaded and extruded at a high temperature. However, it is presumed that silver lactate decomposes into lactic acid and silver at a high temperature, and silver ions formed by the decomposition aggregate to form ultrafine silver particles in the synthetic resin.
The above invention was originally performed using a polypropylene resin as a synthetic resin. However, it is technically expected that the same effect can be sufficiently expected with other thermoplastic resins, and is therefore another general-purpose synthetic resin. Similar investigations were made not only for polyethylene resins, polystyrene resins, ABS resins, etc., but also for polycarbonate resins, polyamide resins, polyethylene terephthalate resins, etc., which are engineering resins. It was found that similar results were obtained.

More specifically, the present invention is as follows. That is, the silver nanoparticle-containing composition according to claim 1 of the present application is produced by mixing a predetermined amount of silver lactate and a thermoplastic resin and kneading the thermoplastic resin at a meltable temperature. .
The master batch containing silver nanoparticles according to claim 2 of the present application is prepared by mixing a predetermined amount of silver lactate and a thermoplastic resin, kneading at a meltable temperature of the thermoplastic resin to obtain a mixed melt, and mixing and melting the mixture. It is characterized by being manufactured by extruding, cooling and chopping.
The silver nanoparticle-containing masterbatch according to claim 3 of the present application is the silvernanoparticle-containing masterbatch according to claim 2, wherein the silver concentration in the silver lactate with respect to the thermoplastic resin is about 200 ppm to It is characterized by 20,000 ppm.
Furthermore, the master batch containing silver nanoparticles according to claim 4 of the present application is the master batch containing silver nanoparticles according to claim 2 or claim 3, wherein the silver nanoparticles have a particle size of about 1 nm to 80 nm. It is characterized by that.
In addition, a synthetic resin molded product according to claim 5 of the present application is a thermoplastic resin containing the silver nanoparticle-containing masterbatch according to any one of claims 2 to 4 added and mixed to melt the thermoplastic resin. It is characterized by being melted and molded at a possible temperature.

In the present invention, the raw material used to make silver exist as ultrafine particles in the synthetic resin is a simple chemical product called silver lactate, and it requires a special process other than mixing and heating with the synthetic resin. Nor. In addition, a sufficient antibacterial effect can be exhibited even when the amount of silver lactate used is as small as 200 ppm to 20,000 ppm. Therefore, for example, the cost is lower than that of a conventional method in which silver is supported on zeolite or the like described in Patent Document 2 and the amount used is at least 2 to 3% or more.
In addition, the synthetic resin (master batch containing silver nanoparticle) in which ultrafine particles (so-called nanosize) of silver obtained in the present invention are dispersed may be a transparent synthetic resin such as polystyrene resin or polycarbonate resin. The transparency of the synthetic resin is not impaired because the size of the silver particles is smaller than the wavelength of visible light.
Furthermore, since the physical properties of the synthetic resin molded product obtained from the master batch containing silver nanoparticles according to the present invention are very low, the content of silver nanoparticles is 200 ppm to 20,000 ppm, usually about 500 ppm to 5,000 ppm. The physical properties inherent to the synthetic resin are not impaired.

FIG. 1 is a photograph of an internal structure observed with a transmission electron microscope of a masterbatch containing silver nanoparticles using polypropylene as a synthetic resin raw material pellet according to the present invention, and FIG. FIG. 1 (B) is a photograph of a PP substrate containing 4,000 ppm of silver nanoparticles according to the present invention. FIG. 2 is a production flow diagram of a masterbatch containing silver nanoparticles according to the present invention.

First, the manufacturing process of the master batch containing silver nanoparticles according to the present invention will be described with reference to FIG. In FIG. 2, reference numeral 1 is a master batch containing silver nanoparticles according to the present invention (hereinafter referred to as “master batch (1) containing silver nanoparticles)”, reference numeral 3 is a synthetic resin raw material pellet, and reference numeral 5 is Silver lactate.

[Raw material mixing step: S1]
After measuring a predetermined amount of powdered silver lactate (5) or an aqueous solution of silver lactate (5) and a synthetic resin raw material pellet (3), the mixture is mixed with a Henschel mixer or the like. It feeds into the kneading extruder for master batch production. The predetermined amount is such that the silver concentration in the silver lactate (5) is about 200 ppm to 20,000 ppm with respect to the synthetic resin raw material pellet (3). Synthetic resin raw material pellet “250” for “2”.
The amount of silver lactate (5) added to the synthetic resin raw material pellet (3) is preferably about 200 ppm to 20,000 ppm with respect to the pellet because the obtained pellet is desirably used as a master batch. That is, when the concentration is 200 ppm or less, the concentration of silver becomes too low when used as a master batch, and the antibacterial effect is difficult to be obtained. When the concentration is 20,000 ppm or more, the cost is increased and the practicality is lost. .
In addition, when mixing the synthetic resin raw material pellet (3) and the silver lactate (5), in order to uniformly attach the fine powder of the silver lactate (5) to the surface of the synthetic resin raw material pellet (3), liquid paraffin or the like It is desirable to add and mix a small amount in advance as a so-called spreading agent. Although depending on the type of the synthetic resin, it is also preferable to add and use a lubricant such as magnesium stearate so that the silver nanoparticles are more uniformly dispersed in the synthetic resin.

In addition, preparation of the aqueous solution of silver lactate was based on the following procedures.
1. 30 g of powdered silver lactate silver lactate powder is dissolved in 970 g of distilled water.
2. Insoluble particles are filtered through a glass filter.
2 is a schematic view of granular silver lactate (5) stuck to the surface of granular synthetic resin raw material pellet (3).

[Raw material mixture melting / kneading step: S2]
In the kneading extruder for master batch production, the synthetic resin raw material pellets (3) in the raw material mixture are melted by heating, and the silver lactate (5) is stirred and mixed uniformly, and the silver in the silver lactate (5) The ions are reduced to silver nanoparticles having a nano-sized particle size.
The silver nanoparticles are presumed to be formed by aggregation of silver ions in silver lactate depending on the processing temperature, but the particle size can be adjusted by adjusting the heat and temperature during the production of the master batch containing silver nanoparticles. Can be planned. In addition, the set temperature of the cylinder at the time of melting and kneading extrusion by the kneading extruder for masterbatch production is set to a temperature suitable for each synthetic resin, but usually 170 ° C to 290 ° C is used. For example, about 170 ° C. to 180 ° C. is used for polyethylene resin, and about 270 ° C. to 290 ° C. is used for polycarbonate resin. The kneading extruder for producing the master batch is preferably a twin screw extruder, but it has been confirmed that there is no particular problem even with a single screw extruder.

[Extrusion process: S3]
The reheated raw material mixture is extruded from a nozzle and formed into a strand shape.

[Cooling and shredding step: S4]
The extruded molded product is cooled and further cut into a master batch (1) containing silver nanoparticles.
In addition, the figure described in [Cooling and Shredding Step] in FIG. 2 is a schematic diagram of a master batch (1) containing silver nanoparticles.

Here, properties and the like of a master batch (hereinafter referred to as “PP base material”) containing silver nanoparticles produced through the above process using polypropylene resin pellets as synthetic resin raw material pellets will be described.

FIG. 1 is a photograph of an internal structure observed with a transmission electron microscope of a masterbatch containing silver nanoparticles using polypropylene as a synthetic resin raw material pellet according to the present invention, and FIG. FIG. 1 (B) is a photograph of a PP substrate containing 4,000 ppm of silver nanoparticles according to the present invention. The black dots in the part surrounded by black circles in FIG. 1B are silver nanoparticles, but it can be seen from the photograph that silver nanoparticles having a particle size of less than 10 nm are evenly distributed.

Table 1 shows the specifications of the PP base material containing the silver nanoparticles.

And the antibacterial performance test was done with respect to PP base material containing this silver nanoparticle.
The test method is performed according to JIS Z 2801 (film adhesion method). E. coli NBRC 3972 was used. The results are shown in Table 2. In the table, “non-blended PP substrate” refers to a PP substrate that does not contain silver nanoparticles, and “silver nanoparticle PP substrate” refers to a PP substrate that contains silver nanoparticles.

The “antibacterial activity value” in Table 2 is a numerical value representing the antibacterial performance. Therefore, the two samples shown in Table 2 are both “antibacterial performance”.

In the production of a molded product, as described above, a sufficient antibacterial effect can be obtained when the mass ratio of the raw material pellets is 90% and the silver nanoparticle-containing masterbatch according to the present invention is 10%. . Therefore, synthetic resin materials that can be injection molded, antibacterial plastic molded products to which silver nanoparticles are added, for example, medical equipment, medical equipment, care products, PET bottles, plastic containers, cooking utensils, tableware, various vehicle interiors, It can be processed into furniture, toys, writing instruments, home appliances, oral hygiene products, household goods, and so on.

1 Master batch containing silver nanoparticles according to the present invention 3 Synthetic resin raw material pellets 5 Silver lactate

Claims

A composition containing silver nanoparticles, which is produced by mixing a predetermined amount of silver lactate and a thermoplastic resin and kneading the thermoplastic resin at a meltable temperature.
It is manufactured by mixing a predetermined amount of silver lactate and a thermoplastic resin, kneading at a meltable temperature of the thermoplastic resin to obtain a mixed melt, extruding the mixed melt, cooling and chopping. A masterbatch containing silver nanoparticles.
The silver nanoparticle-containing masterbatch according to claim 2, wherein the silver concentration in the silver lactate with respect to the thermoplastic resin is about 200 ppm to 20,000 ppm.
The silver nanoparticle-containing masterbatch according to claim 2 or 3, wherein the silver nanoparticle has a particle size of about 1 nm to 80 nm.
A master batch containing the silver nanoparticles according to any one of claims 2 to 4 is added to and mixed with a thermoplastic resin, and the thermoplastic resin is melted at a meltable temperature to be molded. Synthetic resin molded product.