JP2013241643A - Dispersion liquid containing silver ultrafine particle, and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dispersion liquid containing a silver ultrafine particle, dispersed without flocculating the silver ultrafine particle, having excellent antibacterial performance, and remarkably excellent in transparency; and to provide a method of manufacturing the same.SOLUTION: A silver ultrafine particle-dispersed high-boiling-point solvent is prepared by adding a fatty acid silver and saccharin to a high-boiling-point solvent, followed by being heating-mixed, the silver ultrafine particle-dispersed high-boiling-point solvent is mixed with a low-boiling-point solvent, the high-boiling-point solvent and the low-boiling-point solvent are thereafter two-phase-separated, and a silver ultrafine particle is transferred therein from the high-boiling-point solvent into the low-boiling-point solvent, thereby obtaining a dispersion liquid containing the silver ultrafine particle.

Description

  The present invention relates to a dispersion containing ultrafine silver particles and a method for producing the same, and more specifically, ultrafine silver particles are dispersed in a low-boiling solvent without agglomeration and precipitation, and have excellent antibacterial and transparency properties. The present invention relates to a liquid and a method for producing the same.

In recent years, in addition to products used in places where bacteria and soot are prone to breed, such as containers used under hot and humid conditions such as medical supplies, kitchens, bathrooms, and washrooms, for example, public such as hanging leather Various antibacterial compositions are proposed because antibacterial performance is required for various products such as those used in places, housing-related materials such as wallpaper and joinery, air conditioner filters, stationery, etc. Has been.
As such an antibacterial composition, a molded product made of a thermoplastic resin or thermosetting resin containing an antibacterial agent, a coating film containing an antibacterial agent in a paint, or an antibacterial agent dispersed in a solvent. It is provided in various forms such as a dispersed liquid.

For example, the following Patent Document 1 describes a composition containing a solvent, silver nanoparticles, and a stabilizer, and the following Patent Document 2 includes an organic silver antibacterial agent and an organic antibacterial agent. An antimicrobial composition is described.
Moreover, the following patent document 3 describes a photocurable composition for antibacterial coating in which a silver salt is contained in a photocurable acrylic resin, and further, the following patent document 4 describes a photocurable resin. There have been proposed resin moldings such as various protective plates for displays having antibacterial properties, which contain antibacterial agents and / or antifungal agents.

Special table 2008-508321 JP 2010-248124 A JP-A-8-31373 International Publication No. 2011/007650

The composition described in Patent Document 1 is composed of a dispersion liquid in which silver nanoparticles are dispersed in a solvent. However, it is difficult to disperse silver nanoparticles without agglomeration. In order to prevent this, a stabilizer is essential, and it is not yet fully satisfactory in terms of transparency and efficient use of silver.
In addition, in the composition described in Patent Document 2, antibacterial performance is imparted to the resin molded body itself in combination with a resin, instead of applying the above substance to a molded body molded in advance as in Patent Document 1. However, it is advantageous in terms of productivity and sustainability of the effect, but to exhibit antibacterial performance equivalent to or higher than that of conventional materials with a content less than the conventional amount of expensive materials such as silver. I'm still not fully satisfied.

  Furthermore, as in the resin compositions described in Patent Documents 3 and 4, in a resin composition obtained by blending a silver salt with a photocurable acrylic resin, the silver salt is efficiently and uniformly dispersed in the acrylic resin. It is difficult to obtain a resin composition having both antibacterial performance and economic efficiency, so it is hoped that silver ultrafine particles capable of exhibiting excellent antibacterial performance are contained in the resin composition without agglomeration. It is rare.

Accordingly, an object of the present invention is to provide a silver ultrafine particle-containing dispersion liquid in which silver ultrafine particles are dispersed without agglomeration, have excellent antibacterial performance, and are remarkably excellent in transparency.
Another object of the present invention is to provide a method for producing a dispersion that can effectively remove by-products during the production of silver ultrafine particles and has excellent antibacterial performance and transparency.

  According to the present invention, there is provided a silver ultrafine particle-containing dispersion having transparency, characterized by containing ultrafine silver particles formed from fatty acid silver and saccharin in a low boiling point solvent.

According to the present invention, a silver ultrafine particle-dispersed high-boiling solvent is prepared by adding fatty acid silver and saccharin to a high-boiling solvent, and heating and mixing the resulting mixture. Provided is a method for producing a dispersion containing ultrafine silver particles, characterized in that after mixing, the high-boiling solvent and the low-boiling solvent are separated into two phases, and the ultrafine silver particles are transferred from the high-boiling solvent to the low-boiling solvent. Is done.
In the method for producing a dispersion containing ultrafine silver particles of the present invention,
1. The heating temperature is 120 ° C. or higher and lower than the decomposition start temperature of fatty acid silver;
2. The low boiling point solvent is methyl isobutyl ketone or methyl ethyl ketone,
Is preferred.

In the dispersion containing ultrafine silver particles of the present invention, ultrafine silver particles having an average particle size of 100 nm or less are dispersed without agglomeration, and the fatty acid produced as a by-product during the production of ultrafine silver particles is removed from the dispersion. Excellent in properties. Further, since the silver ultrafine particles are dispersed without agglomeration, they are excellent in transparency and can efficiently exhibit antibacterial performance. In addition, antibacterial shows what suppresses proliferation and propagation of bacteria.
Moreover, in the silver ultrafine particle-containing dispersion of the present invention, since the silver ultrafine particles are dispersed in a low boiling point solvent, it can be suitably used as a diluting solvent for coating compositions, resin compositions, etc. The antibacterial performance can be imparted to the coating film and the resin molded body.
Furthermore, in the dispersion containing silver ultrafine particles of the present invention, since the silver-containing compound having antibacterial performance can be used effectively, the blending amount of the silver-containing compound can be reduced, and the economy is excellent. Yes.
In the method for producing a dispersion containing ultrafine silver particles of the present invention, ultrafine silver particles excellent in antibacterial performance can be dispersed without agglomeration in a low boiling point solvent by a relatively simple operation, and the transparency of the dispersion is affected. It is possible to efficiently remove the by-product that gives water, and the productivity is also excellent. Since the dispersion medium is a low boiling point solvent, it is suitable for the application of antibacterial properties to resin compositions such as paints.

Such an effect of the present invention is also apparent from the results of Examples described later.
That is, in the silver ultrafine particle dispersion of the present invention, as clearly shown by having a transmittance of 90% or more, the ultrafine silver particles are uniformly dispersed without agglomeration, and by-products such as fatty acids are effective. It is clear that it has been removed. It is clear that excellent antibacterial performance can be obtained even when the fatty acid silver content is as small as 0.05 to 0.1% by weight (Examples 1 to 5).
On the other hand, when a combination other than the combination of fatty acid silver and saccharin is used as the antibacterial component, the same solvent is used as in the examples, and even when the same operation is performed, the transparency is somewhat inferior and the desired antibacterial performance Is not obtained (Comparative Examples 1 to 4).
Further, even when the antibacterial component used in the present invention is used, when two-phase separation is not performed or two-layer separation is not performed, the by-product is left in a state where silver ultrafine particles are dispersed in a high boiling point solvent. It is clear that the high boiling point solvent cannot be removed in the coating process because the water is present as it is, and therefore the desired coating film cannot be formed and the antibacterial performance is also inferior (Comparative Examples 5 and 6). ).

(Antimicrobial component)
In the dispersion containing ultrafine silver particles of the present invention, it is an important feature to use a combination of saccharin and fatty acid silver as an antimicrobial component for forming ultrafine silver particles.
The mixing ratio of the fatty acid silver and saccharin is preferably in the range of 1: 0.01 to 1: 5, particularly 1: 0.1 to 1: 1 by weight. If it is out of the above range, components that are not used for the formation of silver ultrafine particles increase, which is not only inferior in economic efficiency, but also there is a possibility that transparency is lowered.

  In the present invention, fatty acids in the fatty acid silver used in combination with saccharin include myristic acid, stearic acid, oleic acid, palmitic acid, n-decanoic acid, p-toylic acid, succinic acid, malonic acid, tartaric acid, malic acid, glutaric acid. An acid, adipic acid, an acetic acid etc. can be mentioned, Especially, a stearic acid can be used conveniently. The most suitable fatty acid silver includes silver stearate.

(High boiling point solvent)
In the present invention, the high boiling point solvent to which the antibacterial component is first added means a solvent having a higher boiling point than the low boiling point solvent to be used.
That is, in the present invention, by heating a high-boiling solvent to which an antibacterial component is added, silver ultrafine particles are formed in the solvent. Therefore, by heating at a temperature lower than the decomposition start temperature of fatty acid silver, It becomes possible to prepare a dispersion without volatilization.
As such a high boiling point solvent, ethylene glycol, diethylene glycol, glycerin and the like can be preferably used.

(Low boiling solvent)
In the dispersion containing ultrafine silver particles of the present invention, the low boiling point solvent used as a dispersion medium containing ultrafine silver particles is a solvent that is smaller than the boiling point of the high boiling point solvent and that can be two-phase separated from the high boiling point solvent. This makes it possible to transfer the ultrafine silver particles from the high-boiling solvent and to remove the high-boiling solvent together with by-products.
The boiling point of the low boiling point solvent is preferably in the range of 40 to 100 ° C. from the viewpoints of productivity and handleability when the dispersion of the present invention is used in combination with other resin compositions. .
As such a low boiling point solvent, methyl isobutyl ketone, methyl ethyl ketone or the like can be effectively used when the above-described glycols are used as the high boiling point solvent.

(Method for producing a dispersion containing ultrafine silver particles)
The dispersion containing ultrafine silver particles of the present invention is prepared by the following method.
(1) First step First, a combination of fatty acid silver and saccharin is added to a high-boiling solvent, and heated and mixed for 1 to 30 minutes at a temperature lower than the decomposition start temperature of the fatty acid silver to be used. Form in. Preferably, the silver compound is easily dissolved by heating in a temperature range of 120 ° C. or higher and lower than the decomposition start temperature of the fatty acid silver, and the dissolved silver compound is easily reduced, so that silver ultrafine particles are easily formed. .
In this case, the fatty acid silver as an antibacterial component is desirably blended in an amount of 0.1 to 5 parts by weight per 100 parts by weight of the high boiling point solvent. If the amount of fatty acid silver is less than the above range, sufficient antibacterial performance cannot be imparted to the dispersion, while if the amount of fatty acid silver is greater than the above range, the antibacterial effect is higher. However, it is not preferable in terms of economy and moldability.

(2) Second Step Next, a mixed solution is prepared by adding and mixing a low boiling point solvent to such a high boiling point solvent containing silver ultrafine particles.
The amount of the low-boiling solvent added varies depending on the content of the antibacterial component to be used and cannot be generally specified, but is desirably in the range of 10 to 100 parts by weight with respect to 100 parts by weight of the high-boiling solvent.
(3) Third step After the high-boiling solvent and the low-boiling solvent are phase-separated by allowing the liquid mixture of the high-boiling solvent and the low-boiling solvent to stand at a temperature of 0 to 40 ° C. for 30 to 600 minutes, Remove the solvent.
When the mixed solution is phase-separated, the ultrafine silver particles present in the mixed solution move to the low-boiling solvent side, and most of fatty acids such as stearic acid by-produced by the formation of ultrafine silver particles are in the high-boiling solvent. Therefore, by removing the high boiling point solvent, a dispersion liquid in which silver ultrafine particles are dispersed in the low boiling point solvent can be obtained.
The removal of the high boiling point solvent can be carried out by a conventionally known method such as simple distillation, vacuum distillation, precision distillation, thin film distillation, extraction, membrane separation or the like.

(Dispersion containing ultrafine silver particles)
As described above, the dispersion containing ultrafine silver particles of the present invention is a dispersion in which ultrafine silver particles having an average particle size of 100 nm or less are dispersed in a low boiling point solvent such as methyl isobutyl ketone and methyl ethyl ketone without aggregation. Therefore, the transmittance is 90% or more, and the transparency is remarkably excellent. In addition, the average particle diameter as used in this specification means the thing which made the thing which does not have a clearance gap between silver and makes one particle | grain, and took the average.
In addition, since the silver ultrafine particles are uniformly dispersed without agglomeration, it can exhibit excellent antibacterial performance, and saccharin silver contained as a trace component also has a silver ion elution property as described above. Since it is excellent, antibacterial performance is also improved by this.
Furthermore, in the dispersion containing ultrafine silver particles of the present invention, when fatty acid silver is used as an antibacterial component, the ultrafine silver particles present in the liquid separation are between the fatty acid and silver, the surface of which is modified with the fatty acid component. Therefore, when the dispersion liquid of the present invention is blended with a coating composition or a resin composition, direct contact between the silver surface and the resin can be reduced. Degradation can be effectively suppressed, a decrease in the molecular weight of the resin and the like can be reduced, and inhibition of moldability can be effectively prevented.

The ultrafine silver particle-containing dispersion of the present invention can be suitably used as a diluent solvent for a coating composition or a resin composition, and thus the coating composition without impairing the transparency of the coating composition or the resin composition. Antibacterial performance can be imparted to a coating film made of the composition or a resin molded body made of the resin composition.
Such paint compositions include phenolic resins, epoxy resins, urethane resins, melamine resins, urea resins, alkyd resins, unsaturated polyester resins, silicone resins, and other thermosetting resins, or photocurable acrylic resins. Can be used as the base resin.
As the resin composition, in addition to the above thermosetting resin, low-, medium-, high-density polyethylene, linear low density polyethylene, linear ultra-low density polyethylene, isotactic polypropylene, syndiotactic polypropylene, propylene -Olefin resins such as ethylene copolymer, polybutene-1, ethylene-butene-1 copolymer, propylene-butene-1 copolymer, ethylene-propylene-butene-1 copolymer, polyethylene terephthalate, polybutylene terephthalate, Mention may be made of polyester resins such as polyethylene naphthaate, polyamide resins such as nylon 6, nylon 6,6 and nylon 6,10, and thermoplastic resins such as polycarbonate resin.
Since the dispersion containing ultrafine silver particles of the present invention is excellent in transparency, it should be used as a diluting solvent for a composition comprising an acrylic resin, particularly a photocurable acrylic resin, which requires particularly high transparency. Is preferred.

(Dispersion permeability)
Dilute the dispersion 5 times with the solvent used as the dispersion medium, measure the transmittance from 400 to 800 nm with a spectrophotometer, and set the average value as the transmittance. X was determined.

(Antimicrobial test of resin composition)
The antibacterial test method conformed to JIS Z 2801: 2000 antibacterial processed product-antibacterial test method. S. aureus was used as the bacterial species. The antibacterial activity value was defined as a logarithmic value obtained by dividing the number of bacteria after cultivation of the unprocessed film by the number of bacteria after cultivation of the antibacterial film. The case where the antibacterial activity value was 2.0 or more was judged as ◯, and the case where the antibacterial activity value was less than 2.0 was judged as ×.

Example 1
In a 100 ml glass bottle, 48.5 g of ethylene glycol, 1 g of silver stearate, 0.5 g of saccharin, and 200 g of zirconia beads (φ0.65 mm) were blended as a high-boiling solvent, and then stirred for 30 minutes to obtain a dispersion. The dispersion was transferred to an Erlenmeyer flask and heated and mixed with stirring at 180 ° C. for 10 minutes. Thereafter, 10 ml of methyl isobutyl ketone (MIBK) was added as a low boiling point solvent, stirred and mixed, and allowed to stand for 1 hour. Since the low boiling point solvent and the high boiling point solvent were separated into two layers, the high boiling point solvent side was removed to obtain a dispersion containing ultrafine silver particles in the low boiling point solvent. The transmittance of the dispersion was evaluated. A photocurable acrylic resin (manufactured by Taisei Fine Chemical Industries), a dispersion containing ultrafine silver particles, MIBK, and a photopolymerization initiator (Ciba Specialty Chemical) mixed in advance with a dilution solvent in a ratio of 50: 1: 48.4: 0.6 After mixing at a weight ratio and coating on a PET film having a thickness of 100 μm with a bar coater, it was cured with a UV irradiation device to form a coating film made of the resin composition on the PET film. The antibacterial effect on the coating surface (side opposite to the PET film) was confirmed. The results are shown in Table 1.

(Example 2)
A dispersion and a resin composition were prepared in the same manner as in Example 1 except that ethylene glycol was changed to diethylene glycol, and the same evaluation as in Example 1 was performed. The results are shown in Table 1.

(Example 3)
A photocurable acrylic resin (manufactured by Taisei Fine Chemical Industry), a dispersion containing ultrafine silver particles, MIBK, and a photopolymerization initiator (Ciba Specialty Chemical) mixed in advance with a diluting solvent in a ratio of 50: 0.05: 48.9: 0. A dispersion and a resin composition were prepared in the same manner as in Example 1 except that they were mixed at a weight ratio of 6. The same evaluation as in Example 1 was performed. The results are shown in Table 1.

Example 4
The dispersion and the resin composition were prepared in the same manner as in Example 1 except that the dispersion was transferred to an Erlenmeyer flask and heated and mixed while stirring at 160 ° C. for 10 minutes, and the same evaluation as in Example 1 was performed. The results are shown in Table 1.

(Example 5)
A dispersion and a resin composition were prepared in the same manner as in Example 1 except that ethylene glycol was changed to glycerin, and the same evaluation as in Example 1 was performed. The results are shown in Table 1.

(Comparative Example 1)
A dispersion and a resin composition were prepared in the same manner as in Example 1 except that saccharin was changed to sodium saccharin, and the same evaluation as in Example 1 was performed. The results are shown in Table 1.

(Comparative Example 2)
A dispersion and a resin composition were prepared in the same manner as in Example 1 except that saccharin calcium was used, and the same evaluation as in Example 1 was performed. The results are shown in Table 1.

(Comparative Example 3)
A dispersion and a resin composition were prepared in the same manner as in Example 1 except that 49 g of ethylene glycol, 1 g of silver stearate, and 200 g of zirconia beads (φ0.65 mm) were blended in a 100 ml glass bottle as Example 1 The same evaluation was performed. The results are shown in Table 1.

(Comparative Example 4)
After blending 49.0 g of ethylene glycol, 1 g of saccharin silver and 200 g of zirconia beads (φ0.65 mm) as a high boiling point solvent in a 100 ml glass bottle, the mixture was shaken for 30 minutes to obtain a dispersion. The dispersion was transferred to an Erlenmeyer flask and heated and mixed with stirring at 180 ° C. for 10 minutes to obtain a dispersion. The transmittance of the dispersion was evaluated. A photocurable acrylic resin (manufactured by Taisei Fine Chemical Industries), a dispersion containing ultrafine silver particles, MIBK, and a photopolymerization initiator (Ciba Specialty Chemical) mixed in advance with a dilution solvent in a ratio of 50: 1: 48.4: 0.6 After mixing at a weight ratio and coating on a PET film having a thickness of 100 μm with a bar coater, it was cured with a UV irradiation device to form a coating film made of the resin composition on the PET film. The antibacterial effect on the coating surface (side opposite to the PET film) was confirmed. The results are shown in Table 1.

(Comparative Example 5)
In a 100 ml glass bottle, 48.5 g of ethylene glycol, 1 g of silver stearate, 0.5 g of saccharin, and 200 g of zirconia beads (φ0.65 mm) were blended as a high-boiling solvent, and then stirred for 30 minutes to obtain a dispersion. The dispersion was transferred to an Erlenmeyer flask and heated and mixed with stirring at 180 ° C. for 10 minutes to obtain a dispersion. The transmittance of the dispersion was evaluated. A photocurable acrylic resin (manufactured by Taisei Fine Chemical Industries), a dispersion containing ultrafine silver particles, MIBK, and a photopolymerization initiator (Ciba Specialty Chemical) mixed in advance with a dilution solvent in a ratio of 50: 1: 48.4: 0.6 After mixing at a weight ratio and coating on a PET film having a thickness of 100 μm with a bar coater, it was cured with a UV irradiation device to form a coating film made of the resin composition on the PET film. The antibacterial effect on the coating surface (side opposite to the PET film) was confirmed. The results are shown in Table 1.

(Comparative Example 6)
A dispersion and a resin composition were prepared in the same manner as in Example 1 except that ethylene glycol was changed to polyethylene glycol. Silver ultrafine particles did not migrate to the MIBK side.

(Comparative Example 7)
In a 100 ml glass bottle, 49.5 g of ethylene glycol, 0.5 g of saccharin, and 200 g of zirconia beads (φ0.65 mm) were blended as a high-boiling solvent, and then stirred for 30 minutes to obtain a dispersion. The dispersion was transferred to an Erlenmeyer flask and heated and mixed with stirring at 180 ° C. for 10 minutes. Thereafter, 10 ml of methyl isobutyl ketone (MIBK) was added as a low boiling point solvent, stirred and mixed, and allowed to stand for 1 hour. Since the low boiling point solvent and the high boiling point solvent were separated into two layers, the high boiling point solvent side was removed to obtain a dispersion. The transmittance of the dispersion was evaluated. A photocurable acrylic resin (manufactured by Taisei Fine Chemical Industries), a dispersion containing ultrafine silver particles, MIBK, and a photopolymerization initiator (Ciba Specialty Chemical) mixed in advance with a dilution solvent in a ratio of 50: 1: 48.4: 0.6 After mixing at a weight ratio and coating on a PET film having a thickness of 100 μm with a bar coater, it was cured with a UV irradiation device to form a coating film made of the resin composition on the PET film. The antibacterial effect on the coating surface (side opposite to the PET film) was confirmed. The results are shown in Table 1.

(Comparative Example 8)
After blending 50 g of ethylene glycol and 200 g of zirconia beads (φ0.65 mm) as a high boiling point solvent in a 100 ml glass bottle, the mixture was shaken and stirred for 30 minutes to obtain a dispersion. The dispersion was transferred to an Erlenmeyer flask and heated and mixed with stirring at 180 ° C. for 10 minutes. Thereafter, 10 ml of methyl isobutyl ketone (MIBK) was added as a low boiling point solvent, stirred and mixed, and allowed to stand for 1 hour. Since the low boiling point solvent and the high boiling point solvent were separated into two layers, the high boiling point solvent side was removed to obtain a dispersion. The transmittance of the dispersion was evaluated. A photocurable acrylic resin (manufactured by Taisei Fine Chemical Industries), a dispersion containing ultrafine silver particles, MIBK, and a photopolymerization initiator (Ciba Specialty Chemical) mixed in advance with a dilution solvent in a ratio of 50: 1: 48.4: 0.6 After mixing at a weight ratio and coating on a PET film having a thickness of 100 μm with a bar coater, it was cured with a UV irradiation device to form a coating film made of the resin composition on the PET film. The antibacterial effect on the coating surface (side opposite to the PET film) was confirmed. The results are shown in Table 1.

The silver ultrafine particle-containing dispersion of the present invention can impart excellent antibacterial performance without impairing the transparency of the coating film or resin molded article by using it as a diluent solvent for coating compositions or resin compositions. It becomes possible.
In particular, the silver ultrafine particle-containing dispersion of the present invention can be suitably used as a diluting solvent for an acrylic resin used as a hard coat material formed on a protective film for a liquid crystal display. Antibacterial performance can be efficiently imparted to an excellent protective film for liquid crystal displays.

Claims (4)

  A silver ultrafine particle-containing dispersion liquid having transparency, comprising silver ultrafine particles formed from fatty acid silver and saccharin in a low boiling point solvent.   A fatty acid silver and saccharin are added to a high boiling point solvent, and the mixture is heated and mixed to prepare a silver ultrafine particle dispersed high boiling point solvent. After mixing the silver ultrafine particle dispersed high boiling point solvent with a low boiling point solvent, A method for producing a dispersion containing ultrafine silver particles, wherein two-phase separation is performed between a boiling point solvent and a low boiling point solvent, and silver ultrafine particles are transferred from a high boiling point solvent to a low boiling point solvent.   The method for producing a dispersion containing ultrafine silver particles according to claim 2, wherein the heating temperature is 120 ° C or higher and lower than the decomposition start temperature of fatty acid silver.   The method for producing a dispersion containing ultrafine silver particles according to claim 2 or 3, wherein the low boiling point solvent is methyl isobutyl ketone or methyl ethyl ketone.