JPH10102047A - Dust-preventing treatment and dust-preventing treatment composition produced by the treatment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for a dust-preventing treatment, capable of inhibiting dusting of a dusting powdery material without requiring outer heat, reaction heat, a heating device and a reacting raw material for the heat. SOLUTION: This method for a dust-preventing treatment comprises mixing a dusting powdery material comprising at least one of quick lime, slaked lime, a lime-solidifying agent, a cement, a slag, calcium carbonate and gypsum with a small amount of polytetrafluoroethylene resin powder under a shear action and a compression actin in a high speed mixer to generate heat and fibrillate the polytetrafluoroethylene resin powder. The polytetrafluoroethylene resin powder is preferably added in an amount of 0.01-0.1wt.% based on the dusting powdery material. The mixer is preferably a Herschel mixer, especially an S-shaped stirring blade-having mixer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dust-proofing method for suppressing dust generation of dust-producing powders that generate a large amount of dust, and a dust-proofing composition prepared thereby.

[0002]

2. Description of the Related Art Hitherto, in order to perform dustproofing of dust-forming powder by fibrillation of polytetrafluoroethylene resin powder, it has been necessary to apply heat, compress and shear. For example, in Japanese Patent Publication No. 52-32877,
An effective amount of particulate polytetrafluoroethylene resin powder is mixed with a highly dusty powdery substance, and the mixture is subjected to compression and shearing action under a heating temperature condition at which the polytetrafluoroethylene resin powder can be fibrillated. A method for suppressing dust in powdery substances other than polytetrafluoroethylene resin powder by performing compression and shearing operations is described in the following: a low-speed electric mixer equipped with an impeller, a sigma blade mixer, A mixing device such as a heavy cone type mixer or a Simpson type mortar is usually used.

In order to complete the fibrillation of such polytetrafluoroethylene resin powder within an industrially practical time, it is desirable to set the heating temperature to 80 ° C. or higher. That can be performed by reaction heat such as a hydration reaction and an oxidation reaction,
For example, a dust-proofing composition comprising a mixture of a polytetrafluoroethylene resin powder and one of two types of solid particulate substances that generate heat by reacting with each other is known. JP-A-64-81883).

[0004]

However, such a dust-proofing technique requires an external heating source, requires a heating device in addition to a normal mixing device, and results in excessive utilities and cost burdens. When heat of reaction is used, there are various problems such as the necessity of the other reaction material for dust-proofing, which inevitably increases the cost as a whole.

[0005] Under such circumstances, the present invention provides a simple and inexpensive dust-proofing device capable of suppressing the generation of dust-producing powder without the need for external heat or reaction heat, and hence no heating device or reactive material. The purpose is to provide a processing method.

[0006]

SUMMARY OF THE INVENTION The present inventors have developed a dust-proofing method having the above-mentioned preferable characteristics by
As a result of various studies, they have found that the object can be achieved by mixing the dust-generating substance and the polytetrafluoroethylene resin powder while generating heat in a high-speed mixing mixer. I've reached the point.

That is, the present invention relates to a method for producing a polytetrafluoroethylene resin powder by mixing a dust-producing powder and a small amount of the polytetrafluoroethylene resin powder in a high-speed mixing mixer while generating heat under shearing action and compression action. To provide a dust-proofing method for dust-producing powder, characterized in that And the dustproofing composition is prepared by such a method.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The dust-producing powder used in the present invention is not particularly limited as long as it generates dust, and examples thereof include quick lime, slaked lime, lime-based solidifying material, and the like. Examples include cement, slag, calcium carbonate, gypsum and the like. These may be used alone or in combination of two or more.

The lime-based solidifying material is obtained by mixing a setting hardening material or a material having hydraulic or air-hardening properties, such as gypsum, slag, pozzolan, cement, etc., in quick lime or slaked lime. As the above cement, ordinary type, early-strength type, ultra-high-strength type, various kinds of Portland cement such as moderate heat type, blast furnace cement, fly ash cement, silica cement,
In addition to various mixed cements such as pozzolan cement, special cements such as alumina cement, water glass cement, and acid-resistant cement, and various cement-based solidifying materials are included. Examples of the gypsum include natural gypsum and chemical gypsum. Examples of the slag include granulated blast furnace slag, non-ferrous refining slag, garbage incineration slag, and the like. Quick lime, slaked lime, lime-based solidifying material, cement,
Among them, it is particularly preferable to use quicklime or slaked lime because dust generation is more effectively suppressed.

The polytetrafluoroethylene resin powder used in the present invention has an average particle diameter of 350 to 450 μm.
Are preferred.

In the present invention, the polytetrafluoroethylene resin powder is used in an amount of 0.01 to 0.1% by weight, preferably 0.01 to 0.07% by weight, based on the dust-forming powder. Is preferred. If this ratio is less than 0.01% by weight, a sufficient dust-proofing effect cannot be obtained. In addition, troubles such as difficulty in discharging the powder are likely to occur, and the use of expensive polytetrafluoroethylene resin powder increases, which inevitably increases the cost.

The mixing of the dust-generating powder and the polytetrafluoroethylene resin powder may be carried out by simultaneously supplying them into a high-speed mixing mixer, or may be carried out by sequentially supplying them.

This mixing is carried out in a high-speed mixing mixer while generating heat under the action of shear and compression. Examples of the high-speed mixing mixer include a Henschel mixer, an Eirich mixer, a Plowshare mixer, a Redige mixer, and a high-speed mixer. Among them, the Henschel mixer is preferable. Henschel mixer uses S
A letter, a letter Z, a Simpson type, and especially a letter S is preferred because a sufficient stirring force can be obtained and uniform mixing can be performed.
However, a mixer such as a paddle mixer, a Hobart mixer, a mortar mixer, and a screw conveyor cannot obtain a temperature and a shearing force suitable for fibrillation, and cannot obtain a dustproof effect.

When a Henschel mixer is used, mixing is preferably carried out by mixing the Henschel mixer with a stirring blade at a peripheral speed of 10 to 60.
m / s, especially at 20-40 m / s. When the peripheral speed of the stirring blade is less than 10 m / sec, the shearing action and the compressing action are insufficient and fibrillation does not sufficiently occur. The fiber of the powder is easily cut, and the dustproof effect is reduced. The heat generated during the mixing is presumed to be frictional heat generated by the powder particles rubbing each other. Mixing is carried out at a temperature suitable for fibrillation due to this exotherm, preferably 70 ° C.
The above steps are performed until the temperature reaches the range of 80 to 200 ° C.

The mixing is carried out usually for 2 to 10 minutes, preferably 2 to 5 minutes, depending on the mixing speed and the like.
If the mixing time is too short, the temperature will not rise sufficiently, and if it is too long, the shearing action will be too strong, and the fibrillated polytetrafluoroethylene resin fiber will be easily cut, and the dustproof effect will be reduced.

[0016]

According to the dustproofing method of the present invention, it is possible to simply and inexpensively suppress the dusting of the dusting powder without requiring external heat or reaction heat, and hence no heating device or reactive material therefor. .
Further, the dustproofing composition prepared in this way has advantages such as suppression of dust generation, reduction of dust generation, excellent environmental protection and safety, and improved workability.

[0017]

Next, the present invention will be described in more detail by way of examples, which should not be construed as limiting the present invention.

Example 1 60 kg of quicklime powder was put into a Henschel mixer (S-shaped stirring blade diameter 0.55 m), and then 0.03% by weight of quicklime of polyflon MPA FA-500 (trade name, Daikin Industries, Ltd.) , A polytetrafluoroethylene resin powder), and a stirring blade rotation speed of 960 rpm
The mixing was performed for 2 minutes by rotating the stirring blade at a high speed (peripheral speed 27 m / sec). By this treatment, the powder temperature was raised to 120 ° C., and the polyflon MPA FA-500 was fibrillated to obtain a dust-proof treated powder in which dust generation was suppressed. The raw lime powder and the dust-proof powder thereof as the raw materials were respectively charged into a wind tunnel at a wind speed of 2 m / sec, and the amount scattered by 1.5 m or more was determined as the scattering rate. Table 1 shows the results.

Example 2 80 kg of slaked lime powder was charged into a Henschel mixer (S-shaped stirring blade diameter: 0.55 m), and then 0.08% by weight of slaked lime based on polyflon MPA FA-500 (trade name, Daikin Industries, Ltd.) , A polytetrafluoroethylene resin powder), and a stirring blade rotation speed of 980 rpm
The mixing was performed for 5 minutes by rotating the stirring blade at a high speed (peripheral speed: 28 m / sec). In this process, the powder temperature was raised to 82 ° C., and the polyflon MPA FA-500 was fibrillated to obtain a dust-resistant powder in which dust generation was suppressed. Each of the raw lime powder and the dust-proof powder obtained from the above raw material was blown at a wind speed of 2.
It was thrown into a m / sec wind tunnel, and the amount scattered by 1.5 m or more was determined as the scattering rate. Table 1 shows the results.

Example 3 60 kg of a lime-based solidified material composed of 60% by weight of quick lime powder, 20% by weight of gypsum and 20% by weight of granulated blast furnace slag was charged into a Henschel mixer (S-shaped stirring blade diameter 0.55 m). Next, 0.03% by weight of polyflon MPA FA-500 (trade name, manufactured by Daikin Industries, Ltd., polytetrafluoroethylene resin powder) was added to the lime-based solidified material, and the stirring blade rotation speed was 980 rpm (peripheral speed 28 m / sec). )
The mixing was performed for 2 minutes by rotating the stirring blade at a high speed. By this treatment, the powder temperature was raised to 97 ° C., and the polyflon MPA FA-500 was fibrillated to obtain a dust-resistant powder in which dust generation was suppressed. The above-mentioned lime-based solidified material and its dust-proofed powder were each introduced into a wind tunnel at a wind speed of 2 m / sec, and the amount scattered by 1.5 m or more was determined as the scattering rate. Table 1 shows the results.

Example 4 100 kg of cement was put into a Henschel mixer (S-shaped stirring blade diameter 0.55 m), and then 0.07% by weight of polyflon MPA FA-50 based on the weight of cement.
0 (trade name, manufactured by Daikin Industries, Ltd., polytetrafluoroethylene resin powder), and the stirring blade rotation speed was 980 r.
The mixing process was performed for 5 minutes by rotating the stirring blade at a high speed of pm (the circumferential speed of the stirring blade was 28 m / sec). By this treatment, the powder temperature was raised to 90 ° C., and the polyflon MPA FA-500
Was fibrillated to obtain a dust-proofed powder in which dust generation was suppressed. The above-mentioned raw material cement and its dust-proofed powder were each introduced into a wind tunnel having a wind speed of 2 m / sec, and the amount scattered by 1.5 m or more was determined as the scattering rate. Table 1 shows the results.

[0022]

[Table 1] From this, it was found that the dustproof treated powder had a greatly reduced scattering rate and was excellent in dustproofness.

Claims (7)

[Claims] 1. A dust generating powder and a small amount of a polytetrafluoroethylene resin powder with respect to the dust generating powder are mixed in a high-speed mixing mixer while generating heat under a shearing action and a compressing action to fibrillate the polytetrafluoroethylene resin powder. A dust-proofing method for dust-generating powder, comprising: 2. The dust-proofing method according to claim 1, wherein the dust-forming powder is at least one selected from quick lime, slaked lime, lime-based solidifying material, cement, slag, calcium carbonate, and gypsum. 3. The use ratio of the polytetrafluoroethylene resin powder to the dusting powder is 0.01 to 0.1% by weight.
The dustproofing method according to claim 1 or 2, wherein 4. The dustproofing method according to claim 1, wherein the high-speed mixing mixer is a Henschel mixer. 5. A Henschel mixer wherein the stirring blade is S
The dust-proofing method according to claim 4, wherein the dust-proofing method is used. 6. The dustproofing method according to claim 4, wherein the mixing is performed at a peripheral speed of the stirring blade of 10 to 60 m / sec. 7. A dust-proofing composition prepared by the method according to claim 1.