JPH09296328A - Microbicidal activated carbon fiber and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a microbicidal activated carbon fiber excellent in sustainability and microbicidal properties, and effective for the use of a water cleaning device, etc., by stably dispersing very fine particles of metallic silver having <=1μm diameter into the inside of the fiber. SOLUTION: This microbicidal activated carbon fiber dispersed with very fine particles of metallic silver having <=1μm diameter in its inside is obtained by using a pitch containing silver as a raw material for spinning (B) obtained by adding a silver compound to a coal-based or a petroleum-based heavy oil (A), oxidizing, and then polymerizing. The method for producing the fiber is to add the silver compound to the heavy oil (A) having <=500 poise viscosity at 100 deg.C, oxidize (nitrate) and then polymerize the oil at 250-350 deg.C to form a pitch for spinning (B) containing <=1wt.% of silver and having 220-350 deg.C softening point, then form a pitch fiber, make an infusible fiber, and further activate the infusible fiber. A water cleaning device is obtained by using the microbicidal activated carbon fiber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an activated carbon fiber which is used in a water purifier or the like and has excellent antibacterial properties and long life, and a method for producing the same.

[0002]

2. Description of the Related Art With the recent deterioration of the quality of drinking water, water purifiers have been attached to waterworks to remove residual chlorine and mold odor, and to remove harmful substances such as trihalomethane. However, tap water also contains trace amounts of bacteria or spores, and the chlorine that was originally added for sterilization is removed by the water purifier, so the purified water loses its sterilizing power and therefore remains in trace amounts. Breeding of bacteria to be activated becomes active. In particular, if water is left in the water purifier for a long period of time while being left in the water purifier, this effect becomes large, which is a problem from a sanitary point of view.

In order to solve these problems, the sterilizing power of silver ions, which has been known for a long time, is used to adsorb and remove various harmful substances contained in drinking water and suppress the growth of bacteria and the like. It has been practiced to impregnate silver with activated carbon for use in water purification. For example, Japanese Unexamined Patent Publication No.
No. 93134 and Japanese Examined Patent Publication No. 52-38666 are typical examples. In all of these methods, activated carbon produced in advance is impregnated with silver or a silver compound and directly applied by spraying.

Further, in the case of fibrous activated carbon, so-called activated carbon fiber, which has a fast adsorption rate and is superior in adsorption performance of harmful substances such as trihalomethane as compared with activated carbon, a method of adding silver in order to have antibacterial property as well. Has been attempted (Japanese Patent Laid-Open No. 58-131187, Japanese Patent Laid-Open No. 7-1).
No. 63,640), there is a problem that it cannot be attached uniformly.

Also, "PETROTECH" Vol. 19,
No. 1 (1996), pp. 33-37, there is reported a silver particle-supported antibacterial activated carbon fiber produced by a kneading method using a phenol resin as a raw material, silver nitrate and a methanol solvent. However, when the specific surface area becomes large in the running water test, there is a problem that the silver content is significantly decreased with the immersion period, that is, the silver particles fall out from the pores in the initial stage. Further, since a solvent such as methanol is used, it becomes a factor of complexity of the process including the removal thereof and an increase in cost.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an inexpensive silver-containing activated carbon fiber which is excellent in adsorption and removal of harmful substances and is also excellent in antibacterial property for a long time, and a method for producing the same. .

[0007]

Means for Solving the Problems As a result of extensive studies on the above problems, the present inventor has specified a raw material and a production method, and by adding a silver compound at a stage of a precursor raw material for a spinning pitch, Silver can be uniformly dispersed in the activated carbon fiber, and at the time of activation treatment, it can be dispersed in the form of fine particles so as not to substantially inhibit the formation of pores on the surface or inside of the activated carbon fiber,
The inventors have found that it is possible to provide an inexpensive activated carbon fiber which is excellent in adsorptive removal of harmful substances and the like, and which is less likely to drop silver and has excellent antibacterial properties over a long period of time, thereby completing the present invention.

That is, the present invention: A silver-containing spinning pitch (which is obtained by adding a silver compound to a coal-based or petroleum-based heavy oil (A), performing an oxidation treatment, and then performing a polymerization treatment ( B) as a raw material,
Further, there is provided an antibacterial activated carbon fiber in which finely particulate metallic silver having a diameter of 1 μm or less is dispersed inside the fiber. Also, after adding a silver compound to a coal-based or petroleum-based heavy oil (A) whose viscosity at a temperature of 100 ° C is 500 poise or less and performing an oxidation treatment, a polymerization treatment is performed at a temperature of 250 ° C or higher. And softening point of silver content less than 1% by weight 220 ℃
Antibacterial activity of producing pitch (B) for spinning at 350 ° C. or less, then spinning the pitch raw material to produce pitch fiber, then infusibilizing the pitch fiber into infusible fiber, and further activating treatment A method for producing carbon fiber is provided. It is also characterized in that the spinning pitch (B) is obtained by nitrating and oxidizing the heavy oil (A). Further, there is provided a water purification device using the antibacterial activated carbon fiber described above.

Hereinafter, the present invention will be described in detail. (I) Antibacterial Activated Carbon Fiber The antibacterial activated carbon fiber of the present invention is obtained by adding a silver compound to a coal-based or petroleum-based heavy oil (A), performing an oxidation treatment, and then performing a polymerization treatment. It is characterized in that finely particulate metallic silver having a diameter of 1 μm or less, which is obtained from the above-described silver-containing spinning pitch (B) as a raw material, is dispersed (relatively uniformly) inside the fiber.

(I) Regarding metallic silver: 1) Kind of silver compound: The silver compound added to the heavy oil of the present invention is not particularly limited in its kind as long as it can be dispersed in the heavy oil, and it is water-soluble. A silver compound, an organic solvent-soluble silver compound, or the like can be used.

However, silver compounds that are difficult or insoluble in water or organic solvents are difficult to disperse uniformly in heavy oil, and it is necessary to disperse them forcibly by adding an emulsifier, a dispersant / suspension agent and the like. However, these additives are not preferable because they may cause adverse effects on subsequent spinning, infusibilization, heat treatment and the like. Therefore, it is preferable to use a water-soluble silver compound such as silver nitrate, silver sulfate and silver phosphate. Such a silver compound is added to the heavy oil and then sequentially subjected to polymerization treatment, spinning, infusibilization, heat treatment such as activation, etc., so that the activated carbon fiber is finally made into a metallic silver state. Distributed. At this time, the silver compound may remain inside the activated carbon fiber, but in the present invention, it is extremely small and does not affect the performance of the activated carbon fiber.

2) Particle size of metallic silver: The metallic silver of the present invention is
It is necessary to be dispersed inside the fiber so as not to substantially inhibit the formation of pores during activation. Therefore,
The metallic silver dispersed inside the fiber is 1.0 μm or less,
Preferably 0.1-0.8 μm, more preferably 0.1
It is required that the fine particles have a particle diameter of 0.5 μm. If the particle size of the metallic silver is larger than 1.0 μm, it tends to hinder the formation of pores of the activated carbon fiber and hinder its purifying action, which is not desirable, and if it is less than 0.1 μm, it becomes extremely fine particles. The carrying state inside the activated carbon fiber is likely to be unstable, and when used as a water purifier, metallic silver particles fall off and the effect is not maintained, which is not preferable.

The particle size of metallic silver changes depending on the heat treatment temperature, and the higher the heat treatment temperature, the more the produced metal silver particles aggregate. Therefore, the lower the heat treatment temperature, the smaller the particle size tends to be. In order to keep the particle diameter within the above range, it is desirable that the heat treatment temperature is 200 ° C. or higher and 1400 ° C. or lower. Therefore, it is necessary to appropriately select the heat treatment temperature for activation in consideration of the performance of the activated carbon fiber such as the required specific surface area. In the case of the present invention, the heat treatment temperature for activation is 700 as described in detail below.
C. to 1100.degree. C., and the particle size of metallic silver is adjusted to the above range.

3) Content of metallic silver: The content of metallic silver in the activated carbon fiber is 10.0% by weight or less in terms of silver, preferably 0.1 to 5.0% by weight, more preferably 0. It is 0.5 to 2.0% by weight. If the content of metallic silver with respect to the activated carbon fiber is as low as less than 0.1% by weight, the antibacterial effect is reduced, and if it exceeds 10.0% by weight, there is no significant difference in the antibacterial effect and the cost is high. It is not desirable. In the case of the present invention, the silver compound is added at the stage of the raw material heavy oil, so the content of the metallic silver is adjusted at this point. Therefore, the amount of the silver compound added to the heavy oil needs to be determined in consideration of the yield of the spinning pitch and the activation yield that greatly changes depending on the required performance of the activated carbon fiber. The activation yield of the activated carbon fiber depends on the required specific surface area and varies greatly from several% to 90%.

When the silver compound is added in an amount of more than 1% by weight in terms of silver with respect to the spinning pitch, silver tends to precipitate due to a silver mirror reaction or the like during pitching, making uniform dispersion difficult, In addition, during spinning, problems such as yarn breakage are likely to occur. From these, it is possible to add the silver compound in consideration of the yield of the spinning pitch so as to be 1% by weight or less in terms of silver in the spinning pitch stage with respect to the heavy oil as the raw material,
It is desirable that there is no hindrance to pitch formation and fiber formation of pitch, and the content of metallic silver relative to the activated carbon fiber can be maintained within the above-mentioned appropriate range.

(Ii) Regarding the spinning pitch (B): (a) Heavy oil (A) The heavy oil (A) is a condensation polycondensate which gives a certain viscosity (softening point) by oxidation treatment or heat treatment. It is not particularly limited as long as it is a hydrocarbon containing a ring aromatic compound as a main component, but for example, crude oil distillation residual oil, fluid catalytic cracking (FCC) heavy oil, petroleum heavy oil such as naphtha cracking residual oil, coal tar. , Heavy coal-based oils such as coal liquefied oil. The viscosity of the heavy oil is preferably as low as possible in order to uniformly disperse the silver compound, and is 500 at 100 ° C.
It should be below poise, preferably below 100 poise, more preferably below 20 poise.

(B) Spinning pitch (B) The heavy oil (A) is filtered, hydrogenated, catalytically cracked, if necessary,
Distillation, etc., addition / mixing of silver compounds, oxidation treatment,
By carrying out polymerization treatment, distillation and the like, a substantially optically isotropic silver-containing spinning pitch suitable for producing activated carbon fibers can be obtained. In the present invention, the silver compound may be added at any time before the polymerization treatment, but in order to improve operability and dispersibility, it is preferable to add it in accordance with the oxidation treatment described below. In the present invention, the oxidation treatment of the heavy oil (A) needs to be performed before the thermal polymerization treatment in order to smoothly pitch the heavy oil. There are various methods such as air blown as this oxidation method, but in the present invention, performing nitration oxidation treatment provides a high-performance activated carbon fiber, and an optically isotropic pitch with a high yield. It is preferable in that it is obtained and that the silver compound is uniformly dispersed.

The nitration oxidation treatment of heavy oil is preferably carried out in an emulsion state using an acid catalyst such as sulfuric acid or phosphoric acid and an aqueous solution of a nitrating reagent such as nitric acid or an organic nitro compound. For example, the concentration of the nitrating reagent and the acid catalyst in the aqueous solution is generally 2 to 10 N (2 to 10 N, respectively).
Mol / L). If the concentration of the nitrating reagent is less than 2 N, the reaction such as nitration is not sufficiently performed.
Further, even if it exceeds 10 N, the progress of the nitration reaction hardly changes, which is disadvantageous in terms of cost. Further, during this operation, it is desirable to sufficiently stir with a stirrer, including uniformly mixing the added silver compound.

The nitration reaction is generally carried out at a low temperature of about 10 to 100 ° C. for 0.5 to 5 hours, preferably 0.5 to 2
It is desirable to carry out the reaction with a reaction time of the order of hours. in this way,
Since the pitch fiber made from the nitration-oxidized spinning pitch as a raw material contains a nitrogen-containing functional group, this functional group is desorbed at the time of activation, and the activation reaction is further caused by the reaction between the functional group and the activation gas. Since it is promoted and the micropores are formed throughout the activated carbon fiber, a high-performance activated carbon fiber can be obtained. Since the heavy oil after nitration oxidation contains impurities such as unreacted nitrating reagent, acid catalyst, emulsifier, and water, it is necessary to separate and remove it by means such as atmospheric distillation.

The thus-obtained nitrate-oxidized heavy oil containing a silver compound is used to obtain a spinning pitch suitable for spinning, and the silver compound added to the heavy oil is used as metallic silver or the like. 250 more to disperse on the spinning pitch
Polymerization is carried out by heating above ℃ to 400 ℃. The heating temperature used in the present invention is a heavy oil having a relatively low viscosity. Therefore, if the heating temperature is less than 250 ° C., the polymerization takes a long time, which is not preferable. Further, if it exceeds 400 ° C, coking occurs, which is not preferable. Further, the softening point is adjusted to 220 ° C. or higher and 350 ° C. or lower by subsequently performing vacuum distillation to remove light components.

The softening point of the obtained spinning pitch is 220 ° C.
If it is less than 350, it takes a long time to infusibilize, which is not preferable.
If the temperature exceeds ℃, the spinning temperature becomes so high as to change the pitch, which is not preferable. Further, the pitch fiber obtained by spinning the spinning pitch having such a softening point smoothly undergoes infusibilization in a temperature range of 150 ° C. to 400 ° C., which will be described later, in a relatively short time. From the viewpoint of production and performance of activated carbon fiber, the raw material pitch is preferably an optically isotropic pitch, more preferably an optically anisotropic pitch, and the spinning pitch of the present invention is almost an optically isotropic pitch. Since it can be obtained, this aspect is also suitable. If there is no hindrance to the production such as activation, mixing of some optically anisotropic pitch is
It does not significantly affect the performance of the activated carbon fiber.

(Iii) Production Process of Activated Carbon Fiber 1) Production of Pitch Fiber The pitch for spinning thus obtained is restricted so that addition of a silver compound is suitable for spinning, and the pitch is determined according to a conventional method. Fibers can be produced. That is, a method commonly used for pitch melt spinning can be used. For example, a spun bond method, a melt blow method, a melt spinning method, a centrifugal spinning method or the like can be used. The melt blow method is particularly preferable in terms of productivity.

2) Production of infusible fiber The infusibilizing treatment of the pitch fiber is usually carried out in an oxidizing gas atmosphere such as oxygen, oxygen-rich gas, air or NO _{2 in} a temperature range of 150 ° C. to 400 ° C., preferably 200 ° C. ℃ to 35
It can be performed by performing an oxidation treatment in the temperature range of 0 ° C.

3) Activation Treatment The activation treatment can be carried out according to a conventional method. For example,
In an atmosphere of activated gas such as steam, carbon dioxide, oxygen,
Activation can be carried out by treating at a temperature of 00 to 1100 ° C., preferably 850 to 1000 ° C. for about 10 to 150 minutes. In this activation treatment, since the infusible fiber contains a nitrogen-containing functional group, this functional group is desorbed at the time of activation, and the activation reaction is further promoted by the reaction between the functional group and the activation gas. A high-performance activated carbon fiber can be provided by being formed on the entire activated carbon fiber.

(Iv) Water Purifying Device Containing Antibacterial Activated Carbon Fiber of the Present Invention The antibacterial activated carbon fiber of the present invention may be used by mixing it with a conventional activated carbon fiber as long as its effectiveness is not impaired.
In addition, it can be used as a filler for a water purifier, particularly as a cartridge, as a single layer or in combination with a microporous membrane layer such as polyethylene or polypropylene.

[0026]

In the antibacterial activated carbon fiber of the present invention, since metallic silver is dispersed in the form of fine particles inside the activated carbon fiber, it does not substantially inhibit the formation of pores during activation treatment, and The antibacterial action of silver can be exhibited without disturbing the purifying action. Furthermore, since a silver compound is added at the manufacturing stage of the pitch for spinning, there is less risk of metallic silver peeling from the surface compared to conventional activated carbon containing silver or fibrous activated carbon. Since it is uniformly dispersed, its antibacterial action is stable and lasts for a long time.

Various measurements of the present invention are carried out by the following methods. Softening point: Measured according to ASTM D-3104. Analysis of metallic silver content in activated carbon fiber: JIS K01
21 by atomic absorption spectrometry. Trihalomethane concentration (ppb): JIS K0125
Headspace method. Free residual chlorine concentration (ppm): measured by the residual chlorine measuring method of JIS K0101. General bacterium count: Measured according to the bacteria test method of JIS K0101.

The dispersed state of the silver particles was prepared by preparing a thin film fragment of activated carbon fiber (set to a thickness of about 2000 to 2500Å), and observed and analyzed on a transmission electron microscope (TEM) photograph (see FIG. 1). did.

EXAMPLES The present invention will be specifically described by the following examples, but the scope of the present invention is not limited thereto.

Example 1 (a) Production of Pitch for Spinning As a heavy oil, a catalytic cracking oil having a viscosity of 9 cSt at 100 ° C. was used, and a 20 wt% silver nitrate aqueous solution was added to the heavy oil. Then, it was added so as to have a ratio of 0.2% by weight in terms of silver, and a nitric acid aqueous solution of 40% by weight (8N) was further added at a ratio of 20% by weight to the heavy oil over 60 minutes. Gradually add and emulsify and mix using a stirrer, perform nitration oxidation treatment at a temperature of 50 ° C for 1 hour, and then distill under atmospheric pressure at 120 ° C for 3 hours to remove unreacted nitric acid and water separately. A nitrated oxidized heavy oil was obtained. Next, the nitrated oxidized heavy oil was heat-polymerized at 350 ° C. for 5 hours to obtain a pitch having a softening point of 90 ° C. Continue to 300
By vacuum distillation at 5 ° C. and 5 torr, an optically isotropic spinning pitch having a softening point of 285 ° C. was obtained with a yield of 40%. The silver content of the spinning pitch was 0.5% by weight.

(B) Production of Activated Carbon Fiber The spinning pitch was melted at a spinning temperature of 3 by a melt blow method.
At 35 ° C, a diameter of 0.2m in a slit of width 1.5mm
Using a spinneret having 400 mφ spinning holes in a row, heated air was ejected from the slit to pull the molten pitch to obtain a pitch fiber having an average diameter of 13 μm. The pitch fiber was heated in an air atmosphere at a temperature rising rate of 3 ° C./min, heat-treated at 320 ° C. for 10 minutes to infusibilize, and then steamed at 950 ° C.
Activated carbon fiber having a specific surface area of 1560 m ² / g was obtained at a yield of 46% by performing activation treatment at 20 ° C. for 20 minutes. When the metallic silver content of the activated carbon fiber was measured, it was 1.1% by weight.

(C) Antibacterial Property of Activated Carbon Fiber After immersing the activated carbon fiber in unsterilized ion-exchanged water for 6 hours and 24 hours, the immersed water is collected and subjected to a standard agar plate culture method (35 ° C., 2 days). ) Was used to measure the number of general bacteria.
The results are shown in Table 1.

[Table 1]

It was found that the activated carbon fiber had a remarkable antibacterial action as compared with Comparative Example 1 described below.
In addition, as a result of carrying out X-ray diffraction measurement of the activated carbon fiber,
The diffraction line of metallic silver was obtained. Further, a thin piece of the activated carbon fiber (about 2000 to 2500 Å thickness, fiber diameter about 12 μm)
Fig. 1 shows a photograph of a cross section of the above prepared and observed with a transmission electron microscope. This photograph shows that the diameter is approximately 0.1-0.
Metallic silver within the range of 5 μm (fine black dots on the photograph indicate the presence of metallic silver, and slightly larger white voids are judged to be the places where metallic silver fell off during sample preparation) inside the activated carbon fiber. It can be seen that they are relatively evenly dispersed in the.

(Comparative Example 1) Using the same raw material oil as in Example 1, but without adding an aqueous solution of silver nitrate, nitration oxidation, heat polymerization treatment, etc. were carried out to obtain a softening point almost the same as in Example 1. An optically isotropic pitch for spinning at 287 ° C. was obtained with a yield of 38%. Using the spinning pitch and in the same manner as in Example 1, activated carbon fibers having a specific surface area of 1580 m ² / g were obtained at a yield of 45%. The results of measuring the number of general bacteria using the activated carbon fiber in the same manner as in Example 1 are combined with those in Example 1 and Table 1 is shown.
It was shown to.

(Examples 2 and 3, Comparative Examples 2 and 3) Example 1
Using the same raw oil as above, except that the addition amount of the silver nitrate aqueous solution was changed as shown in Table 2, nitration oxidation, heat polymerization treatment, etc. were performed in the same manner, and the silver content etc. Four kinds of spinning pitches such as squeeze were obtained. As in Comparative Examples 2 and 3, when the content of silver in the spinning pitch exceeds 1% by weight, the silver dispersed state is extremely deteriorated, probably because silver precipitation occurs due to a silver mirror reaction or the like. It was observed that the silver content tended to be extremely low in a well-dispersed area as compared with the amount of the compound added. Further, using the spinning pitches of Comparative Examples 2 and 3, an attempt was made to carry out spinning in the same manner as in Example 1, but many yarn breakages were unsuitable for the production of activated carbon fibers.

On the other hand, using the spinning pitches of Examples 2 and 3, in the same manner as in Example 1, as shown in Table 2, Example 1 was used.
Two kinds of activated carbon fibers having almost the same specific surface area as those of the above were obtained.
When the metallic silver content of the activated carbon fiber was measured in the same manner as in Example 1, it was found to be commensurate with the addition amount of the silver compound as shown in Table 2. The number of general bacteria was measured using the activated carbon in the same manner as in Example 1. As a result, the number of general bacteria was less than 30 / ml as in Example 1.

[Table 2]

Example 4 4 g of antibacterial activated carbon fiber containing metallic silver obtained in Example 1 and specific surface area 2000 m
After uniformly mixing 11 g of ² / g standard activated carbon fiber,
It was attached to a simple water purifier and continuously passed water for 12 hours at an SV of about 1000. The trihalomethane concentration and the free residual chlorine concentration of the treated water 10 hours after the start of water passage were measured. Table 3 shows the results.

[Table 3] Further, after standing for 24 hours after stopping the water, the water retained in the water purifier was used to measure the antibacterial property in the same manner as in Example 1. As a result, the number of general bacteria was less than 30 cells / ml as in Example 1.

[0037]

The antibacterial activated carbon fiber of the present invention has a diameter of 1
Since the finely divided metallic silver having a particle size of μm or less is stably dispersed inside the fiber, it has an excellent antibacterial effect for a long period of time when it is used in a water purifier or the like.

[Brief description of drawings]

FIG. 1 is a photograph (× 1) of a cross section of a thin film of activated carbon fiber containing metallic silver of the present invention (Example 1) observed by a transmission electron microscope.
0000 times).

Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location C02F 1/28 C02F 1/28 F 1/50 510 1/50 510A 520 520B 531 531E 540 540F 560 560B 560B D01F 1 / 10 D01F 1/10

Claims (4)

[Claims] 1. A silver-containing spinning pitch (B) obtained by adding a silver compound to a coal-based or petroleum-based heavy oil (A), performing an oxidation treatment, and then performing a polymerization treatment.
An antibacterial activated carbon fiber, which is obtained by using as a raw material, and in which finely divided metallic silver having a diameter of 1 μm or less is dispersed inside the fiber. 2. A temperature of 250 ° C. or higher and 400 ° C. or lower after adding a silver compound to a coal-based or petroleum-based heavy oil (A) having a viscosity of 100 poise or less at a temperature of 100 ° C. and performing oxidation treatment. To produce a spinning pitch (B) having a silver content of 1% by weight or less and a softening point of 220 ° C. or more and 350 ° C. or less, and then spinning the pitch to produce a pitch fiber, and then the pitch fiber. The method for producing an antibacterial activated carbon fiber according to claim 1, wherein the infusible fiber is infusibilized to give an infusible fiber, and the fiber is further activated. 3. The spinning pitch (B) is obtained by subjecting the heavy oil (A) to a nitration oxidation treatment.
A method for producing the antibacterial activated carbon fiber described. 4. A water purifier comprising the antibacterial activated carbon fiber according to claim 1.