JPH10279818A - Silver-containing resin composition prevented from thermal discoloration - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the thermal discoloration of a molded resin item having an antibacterial action in a thermal molding process for producing it by using a resin compsn. contg. a silver-base inorg. antibacterial agent in a high concn. and contg. water in a specified amt. or lower as a masterbatch for diluting a virgin resin. SOLUTION: A discoloration-resistant resin compsn. comprising a high-mol.-wt. polymer and a silver-carrying inorg. substance and having a high silver content and a water content controlled to 0.06 wt.% or lower is used as a masterbatch. Silver is used as an antibacterial agent component in the form of silver ion, silver complex ion. a very fine metallic silver powder, etc. Silver ion is prepd. by dissolving silver nitrate, silver acetate, etc., in water or an alcohol and causing to be carried on an inorg. carrier by ion exchange. A silver complex ion is prepd. by causing an inorg. porous body (e.g. silica gel) to occlude the ion in the form of a complex (e.g. silver thiophosphate). The ultrafine metal silver powder is prepd. by sputtering, etc. Pref. examples of an inorg. substance as the silver carrier include zeolite, zirconium phosphate, apatite and water-soluble glass.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silver-containing high-concentration resin composition having discoloration resistance, and more particularly, to the use of the high-concentration resin composition as a master batch.
The present invention relates to a resin composition containing a silver-based inorganic antibacterial agent that does not discolor during molding of a polymer resin.

[0002]

2. Description of the Related Art Conventionally, a resin composition containing a silver-based inorganic antibacterial agent having a bactericidal action (Japanese Patent Publication No. 63-54013) has a problem that the entire resin molded product turns black-brown due to the effect of a silver chemical reaction during heat molding. It changed color. As a method for preventing discoloration of a resin composition containing such a silver-based inorganic antibacterial agent, a method in which silver and ammonium coexist (Japanese Patent Publication No. 4-28646).
A method in which a silver-based inorganic antibacterial agent and an organic antioxidant or a light stabilizer coexist, and a method in which silver oxide is melted as a solid solution in glass have been proposed. However, these methods
Resin composition containing silver-based inorganic antibacterial agent (JP-B-63-54013)
However, although discoloration of the resin is reduced as compared with the method described in Japanese Patent Application Laid-Open Publication No. H10-209, discoloration is also reduced depending on molding conditions, and is not a fundamental means for improving discoloration prevention.

[0003]

A resin composition containing a silver-based inorganic antibacterial agent causes a radical reaction under the influence of moisture adsorbed on an inorganic carrier or water adsorbed on a resin during molding of a resin product. As a result, it is decomposed into hydroxyl radical ions by the catalysis of silver and silver ions, and as a result, double bond formation of the resin structure is promoted, and the resin structure turns yellow-brown. Further, the dissociated silver reacts again with the hydroxide to form silver hydroxide, which becomes silver oxide or fine-grained silver by heat or light, and similarly has the problem of discoloring the resin molded product to brown or black. In addition, before the final molded article, the molding undergoes a remarkable heat history in the molding process.At this time, if water is present in the composition, silver and water undergo the following chemical reaction, and hydroxyl radical ions are generated. It was also known to cause discoloration. As described above, the water vapor generated at the time of heat molding roughens the surface state of the resin molded product, which is one of the causes of making the product dull and low in commercial value.

Hydroxyl radical causing the above discoloration
The reaction of ion generation depends on the presence or absence of oxygen
Therefore, this chemical reaction is performed when oxygen is not present and when oxygen is present.
When they are present, they are as follows. Note that
-OH represents a hydroxyl radical ion. (1) In the absence of oxygen H_TwoO → ・ H + ・ OH (2) When oxygen exists H_TwoO → ・ H + ・ OH ・ H + O_Two→ ・ OOH ・ H + ・ OHH → HOOH → ・ OH + ・ OH Ag + ・ OH → ・ AgOH → 1/2 (Ag_TwoO + H
_TwoO) Ag_TwoO → 2Ag + 1 / 2O_Two  As is clear from the above reaction, when
This triggers the resin composition to undergo a radical reaction.
As a result, many double bonds are formed in the resin composition,
The fat turns brown. In addition, silver ion is A
g_TwoO or fine metallic silver, the resin composition becomes dark brown
Discolor.

[0005]

Means for Solving the Problems The present inventors have solved the above-mentioned problems, and provide a resin composition containing a silver-based inorganic antibacterial agent which does not discolor even in a high-temperature environment during resin molding. Succeeded. In the present invention, when heat-molding a resin product having an antibacterial effect, a high-concentration resin composition containing a silver-based inorganic antibacterial agent as a master batch is used for diluting a virgin resin and having a water content of a specific amount or less. By using this, discoloration of the resin molded product could be prevented.
The most important thing to prevent thermal discoloration of resin molded products is
The raw material of silver-supported inorganic material is that the resin composition does not contain water, and it is most preferable that the raw material of the resin composition containing the silver-supported inorganic material be free of water by a hot cut method or the like. Desirably, it is practically impossible to reduce the water content in the resin composition to 0, so it is possible to prevent thermal discoloration by controlling the water content to the upper limit or less. .

The high-concentration resin composition of the present invention having a water content of not more than the specified amount has a discoloration resistance comprising a silver-based inorganic antibacterial agent and a polymer resin, wherein the water content is controlled to 0.06% by weight or less. A high-concentration resin composition containing a silver-based inorganic antibacterial agent is prepared and used as a master batch in the resin composition. From a practical point of view, the water content of Matasu batch is 0.06wt%
It was found that the discoloration of the silver-containing resin composition can be prevented even if the above reaction occurs in the resin if the content is below. A silver-containing resin composition containing a silver-carrying inorganic substance and a high molecular weight polymer whose water content is controlled to 0.06% by weight or less does not discolor the resin even during molding under a high-temperature environment. The silver used in the present invention is a general-purpose antibacterial agent such as silver ions having antibacterial properties, silver complex ions and ultrafine metal silver, and the silver ions are formed of water using silver nitrate, silver nitrate, silver acetate, or the like. Alternatively, the silver complex ion is dissolved in an alcohol and carried on an inorganic carrier by ion exchange, and the silver complex ion is absorbed in an inorganic porous body such as silica gel in the form of a complex such as silver thiosulfate. Further, ultrafine metallic silver having an active surface energy can be obtained by a sprinkling method or the like.

As the inorganic substance supporting silver, an inorganic ion exchanger such as zeolite, zirconium phosphate, apatite, and montmorillonite, or a water-soluble glass is suitable. The zeolites include natural zeolites and synthetic zeolites, and the crystal form does not matter as long as the silver is ion-exchanged, but the zeolite support itself is mixed with the polymer polymer, so that it is uniform. In order to obtain a molded article having physical properties, a fine article having a uniform particle diameter is desirable. In particular, A-type zeolite has a high loading capacity and is most suitable in the practice of the present invention from the viewpoint of physical properties and economy.

[0008] Zirconium phosphate used as a carrier has a lower silver carrying capacity than zeolite.
It is suitable for use in the present invention because of its fine particles and low water absorption. Further, when water-soluble glass is used as a carrier and silver oxide is used as an antibacterial agent, silver oxide is essentially a glass component, so that when water-soluble water glass containing silver dissolves in water, silver is ionized at the same time. It dissolves in water in a state where it exhibits antibacterial properties, and resin products containing silver glass antibacterial agents had a problem that the discoloration was particularly remarkable due to moisture, but boron oxide was used as a glass component, and practically 30 wt% It is preferable to add the above to have a water-soluble function. Also,
Apatite, which is generally considered to be a desirable inorganic carrier, has weaker silver retention than inorganic carriers such as zeolite and zirconium phosphate described above, and silver precipitates on the surface under a high temperature environment, and silver ions and ultrafine silver Antibacterial activity is reduced due to reduced particles, and montmorillonite is also rich in water absorption like zeolite, and resin products containing inorganic antibacterial agents discolor during heat molding. It is possible.

In order to enhance the antibacterial effect of silver-based antibacterial agents,
It is preferable that silver in the final resin molded product is ionized, and for that purpose, it is desirable that the inorganic antibacterial agent present in the polymer composition absorb moisture. The high-molecular polymer to be used in the present invention is a high-molecular resin widely used in heat molding such as polyolefin resin, polyamide resin, acrylic resin, vinyl chloride resin, ABS resin, urethane resin, and the like.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples are shown below, but the present invention is not limited to these.

Example 1 Preparation of High Concentration Resin Composition; Silver-Supported Inorganic Material; Silver Zeolite (Silver 2.1 wt%, Zinc 13 wt%)
%, Water content 0.01wt%) Resin; polypropylene (trade name "J10", manufactured by Ube Industries, Ltd.)
9 ") The above silver zeolite (10 kg) and polypropylene resin (40 kg) were thoroughly mixed with a Banbury mixer. The molten mixture was extruded into water at 240 ° C. using a twin screw extruder. After taking it out, it is put on a belt and cooled in the air, and the obtained rod-like body is cut into a length of about 1 cm by a guillotine cutter by a strand method, and the effect of the water content in the obtained resin composition is examined. Therefore, the water content was varied by changing the cooling distance in water (18 ° C.) Note that the water content of the master batch is a value analyzed by the Karl Fischer method at 260 ° C.

[0011]

[Table 1] Composition ratio of the obtained resin composition: silver zeolite 20, polypropylene resin 80% ─── No. Water content of master batch (wt%) Cooling distance in water (cm) ──────────────────────────────── 1 0.026 10 2 0.045 20 3 0.060 30 4 0.082 50 5 0.120 100 ────────────────────────────────

The relationship between the polypropylene resin molded plate and discoloration;
The high-concentration resin composition obtained above was diluted 20 times (corresponding to 1% by weight of silver zeolite in the final resin product) with a virgin polypropylene resin (J-700GP manufactured by Idemitsu Petrochemical Co., Ltd.). The above composition was subjected to injection molding under the conditions of 250 ° C. and a residence time of 5 minutes to obtain a plate-like molded product (5 cm × 8 cm × 3).
mm). The water content is an analysis value at 250 ° C. by the Karl Fischer method.

[0013]

[Table 2] ─────────────────────────────── Masterbatch NO. Water content (wt%) ΔE evaluation ─── ──────────────────────────── 1 (invention) 0.025 2.5 Discoloration cannot be confirmed 2 (invention) 0.045 2.7 Discoloration cannot be confirmed 3 ( Control) 0.060 3.1 Discoloration not confirmed 4 (Control) 0.082 7.5 Discoloration (yellow) Yes 5 (Control) 0.120 12.6 Discoloration (yellowish brown) Yes ──────────────────── ────────────ΔE · AN indicates the color difference of JIS L0804.

[0014]

Example 2 Relationship between nylon resin molded plate and discoloration; zirconium silver phosphate (silver 3.0 wt%, moisture 0.01 wt%) as silver-carrying inorganic substance,
Silver glass (silver 0.6 wt%, moisture 0.01 wt%) and silver thiosulfate complex occlusion silica gel (silver 2.5 wt%, moisture 0.88 wt%) were used. 6-nylon as nylon resin (Mitsubishi Chemical Corporation)
; Trade name "Novamid 1010J") was used. A high-concentration resin composition having a silver-carrying inorganic substance concentration of 20% was prepared in the same manner as in Example 1. The obtained high-concentration resin composition is 20 times with a virgin nylon resin (Mitsubishi Chemical Corporation; "Novamid 1010J").
(Equivalent to 1% by weight of silver zirconium phosphate in the final resin product). The resulting composition was placed at 260 ° C. for a residence time of 5
Injection molding under the conditions of 1 min.
cm × 3 mm). The water content is an analysis value at 250 ° C. by the Karl Fischer method.

[0015]

[Table 3] ─────────────────────────────────── No. Inorganic antibacterial agent Master batch ΔE Evaluation Moisture Amount (wt%) ─────────────────────────────────── 6 Zr silver phosphate (this invention) 0.030 2.1 Discoloration cannot be confirmed 7 〃 (this invention) 0.058 2.4 Discoloration cannot be confirmed 8 〃 (control) 0.066 3.2 Slight discoloration 9 〃 (control) 0.092 5.8 Yellow discoloration 10 〃 (control) 0.140 10.2 Yellow brown discoloration 11 Silver glass (invention) 0.055 2.5 Discoloration not confirmed 12 Silver thiosulfate complex occluder (control) 0.050 18.6 Black brown discoloration 色─────────────ΔE · AN indicates the color difference of JIS L0804.

[0016]

The resin composition containing a silver antibacterial agent has excellent antibacterial properties, but has a disadvantage of discoloration due to heat molding, and the discoloration has reduced its commercial value. The amount is controlled to 0.06% or less, making a high-concentration resin composition consisting of a silver-carrying inorganic substance and a polymer resin,
By mixing this as a master batch into the resin composition, discoloration of the resin can be prevented even during molding in a high-temperature environment, and it can greatly contribute to increasing the added value of the resin molded product.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Koji Nakamura Inventor Nakamura Bussan Co., Ltd. Awaji Plant 6-41, Nishi-Awaji, Higashi-Yodogawa-ku, Osaka-shi, Osaka

Claims (5)

[Claims] 1. A silver-containing high-concentration resin composition having a discoloration resistance, comprising a silver-carrying inorganic substance and a polymer, wherein the water content is controlled to 0.06% by weight or less. 2. The high-concentration silver-containing resin composition according to claim 1, wherein silver is an antibacterial agent component. 3. The high-concentration silver-containing resin composition according to claim 1, wherein the inorganic carrier is water-soluble glass. 4. The silver-containing high-concentration resin composition according to claim 1, wherein the inorganic carrier has ion exchange ability. 5. A high concentration resin composition according to claim 1,
Resin composition characterized by being used as a batch