JP2012077312A - Dust treatment agent composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composition for a dust preventive treatment agent made of a fluorine-containing polymer aqueous dispersion which has high dust preventive effect equally to the conventional dust preventive composition, and which also has the low risk of an environmental problem.SOLUTION: The composition for a dust preventive treatment agent is made of a fluorine-containing polymer aqueous dispersion as an aqueous dispersion of polytetrafluoroethylene having a fluorine-containing emulsifier content of ≤50 ppm, in which the specific gravity of the polytetrafluoroethylene is ≤2.27, while the average particle diameter is 0.1 to 0.5 μm, and which contains a hydrocarbon based anionic surfactant as an emulsion stabilizer. The composition is mixed with a dusting substance, and the mixture is subjected to a compressing-shearing action at a temperature of about 20 to 200°C to fibrillate the polytetrafluoroethylene, thus is used for inhibiting the dust of the dusting substance.

Description

The present invention relates to a dust control agent composition for dusting substances, which is made of an aqueous dispersion of polytetrafluoroethylene (hereinafter referred to as PTFE) having a high dustproof effect and less concern for the environment. More specifically, the present invention is a dust-controlling agent composition of a dusting substance having a high dustproof effect and less environmental concerns, comprising an aqueous dispersion of PTFE containing a fluorine-containing emulsifier at a specific low level. About.

Technology for suppressing dust from powdery substances that generate dust is an important technology for daily life and for industry because of other health, safety, environmental and other requirements.
As such dust control technology, in Japanese Patent Publication No. 52-32877, PTFE is fibrillated by mixing PTFE with a powdery substance and subjecting the mixture to a compression-shearing action at a temperature of about 20 to 200 ° C. Thus, a method for suppressing dust generation of a powdery substance has been proposed.

  PTFE is a homopolymer of tetrafluoroethylene in composition and fine powder or emulsion in form Teflon (registered trademark) 6 or Teflon (registered trademark) 30, and a composition in modified polymer of tetrafluoroethylene in form. It is also Teflon (registered trademark) 6C, which is also finen powder.

  JP-A-8-20767 proposes a stable dust control method using an aqueous emulsion containing 1.0% by weight or more of a hydrocarbon-based anionic surfactant with respect to PTFE. Cement has been shown to have a dust control effect. According to the publication, PTFE particles are produced by emulsion polymerization disclosed in US Pat. No. 2,559,752, that is, an anionic interface having tetrafluoroethylene as a water-soluble polymerization initiator and a fluoroalkyl group as a hydrophobic group. It is manufactured in the form of an aqueous emulsion by press-fitting into an aqueous medium containing an activator (hereinafter referred to as a fluorine-containing emulsifier) as an emulsifier, and polymerized, but an emulsion stabilizer is further added to increase the stability. .

Recently, these dust control agents have been used in large amounts in fertilizers, soil stabilizers, soil conditioners, and landfill materials such as coal ash, and the scope of application of dust control agents has increased. Has become a concern.
A surfactant (fluorine-containing emulsifier) contained as an emulsifier in an aqueous PTFE dispersion is used for polymerization, but it is hardly decomposable and there is a concern about influence on the environment. Moreover, since it is not biodegradable but classified as an environmental pollutant, it has been possible to pollute groundwater, lakes and rivers.
Therefore, the present inventors have reached the present invention as a result of intensive efforts to develop a method that has a dust suppressing effect and can suppress dust without concern about the influence on the environment.

Japanese Patent Publication No. 52-32877 JP-A-8-20767 US Pat. No. 2,559,752

The present inventors have disclosed that surfactants (fluorine-containing emulsifiers) contained as an emulsifier in PTFE aqueous dispersions are indispensable in polymerization to obtain PTFE aqueous dispersions, but are hardly decomposable and have an impact on the environment. Focusing on the concerns, we proceeded with the development of dust control agents that are less likely to cause environmental problems.
That is, the present invention provides a dust suppression treatment agent comprising a fluoropolymer aqueous dispersion having a dust suppression effect as high as that of a conventional dust suppression treatment composition and a low possibility of environmental problems. Objective.

According to the present invention, an aqueous dispersion of polytetrafluoroethylene having a fluorine-containing emulsifier content of 50 ppm or less, wherein the polytetrafluoroethylene has a specific gravity of 2.27 or less and an average particle size of 0.1 ~0.5μm der is, consists fluoropolymer aqueous dispersion contains a hydrocarbon-based anionic surfactant as an emulsion stabilizer, is mixed with dusting material, about 20 to 200 ° C. to the mixture By applying a compression-shearing action at a temperature of 1, a dust suppressing treatment agent composition used for fibrillating polytetrafluoroethylene to suppress dust of dusting substances is provided.

  The fluorine-containing polymer aqueous dispersion having a content of the fluorine-containing emulsifier of 50 ppm or less is obtained by removing the fluorine-containing emulsifier from the polymer aqueous dispersion obtained by polymerizing tetrafluoroethylene using the fluorine-containing emulsifier. The above-described dust suppression treatment agent composition obtained by the above method is a preferred embodiment of the present invention.

According to the present invention, there is provided a dust suppression treatment agent comprising a fluoropolymer aqueous dispersion having a dust suppression effect as high as that of a conventional dust suppression treatment composition and having a low possibility of environmental problems.
ADVANTAGE OF THE INVENTION According to this invention, the dust suppression processing agent which not only has a high dust suppression effect and has a low possibility of an environmental problem, but can be utilized effectively by collect | recovering and reusing an expensive fluorine-containing emulsifier. Is provided.

  The present invention provides a dust suppressing treatment agent composition comprising a fluoropolymer aqueous dispersion having a fluorine-containing emulsifier content of 50 ppm or less.

The fluoropolymer of the present invention includes a tetrafluoroethylene (TFE) homopolymer (PTFE) called a homopolymer and a tetrafluoroethylene copolymer (modified PTFE) containing 1% or less of a comonomer called a modified polymer. ). The fluoropolymer is preferably a TFE homopolymer.
The dust suppression treatment agent composed of the modified PTFE aqueous dispersion has a lower dust suppression effect than the dust suppression treatment agent composed of the PTFE aqueous dispersion, and the amount of the treatment agent used is often 50% or more in order to produce the same dust suppression effect. There are things you have to do.

  The fluoropolymer in the fluoropolymer aqueous dispersion of the present invention is desirably a colloidal particle having an average particle size of about 0.1 to 0.5 μm, preferably about 0.1 to 0.3 μm. Colloidal particles having an average particle size of less than 0.1 μm have a low dustproof effect, while aqueous dispersions of colloidal particles having an average particle size of more than 0.5μ tend to be less stable.

  The specific gravity is 2.27 or less, preferably 2.22 or less, more preferably 2.20 or less. Polytetrafluoroethylene having a specific gravity exceeding 2.27 also tends to have a low dustproof effect.

  The concentration of the fluoropolymer in the aqueous fluoropolymer dispersion of the present invention is not particularly limited, but in order to enhance the effect of dispersing the fluoropolymer in the dust generating substance, the lower the concentration, the better. On the other hand, when the fluoropolymer aqueous dispersion is transported, the higher the concentration, the more the transportation cost can be saved. Therefore, it is usually 10% by weight or more, preferably 20 to 70% by weight. A higher concentration is not preferable because it impairs the stability of the aqueous fluoropolymer dispersion. Accordingly, the concentration of the fluoropolymer in the dust control agent composition sold as a product is 20 to 70% by weight, and when mixed into a dust generating substance, it is diluted with water to 5% by weight or less. It can also be used as the fluoropolymer concentration.

  The fluorine-containing emulsifier of the fluoropolymer aqueous dispersion of the present invention is hardly decomposable and is likely to accumulate in the environment, so it is desired that the content is low. It is preferable that it is 50 ppm or less that can be produced at a reduced content.

  There is no particular limitation on the method for obtaining the aqueous fluoropolymer dispersion in which the content of the fluoroemulsifier of the present invention is 50 ppm or less. For example, emulsification as disclosed in US Pat. No. 2,559,752 Fluorine-containing polymer obtained by injecting and polymerizing in an aqueous medium containing a polymerization method, that is, an aqueous surfactant containing tetrafluoroethylene as a water-soluble polymerization initiator and an anionic surfactant having a fluoroalkyl group as a hydrophobic group (fluorine-containing emulsifier). A known method for removing a fluorine-containing emulsifier from an aqueous dispersion containing about 0.02 to 1% by weight of an emulsifier (perfluorooctanoic acid in the form of an ammonium salt and / or an alkali salt) based on the weight of the fluorine-containing polymer, for example, Included in JP 2005-501956 (WO 2003/020836) and JP 2002-532583 (WO 00/35971) Removal by contact with an effective amount of anion exchanger and separation or removal by ultrafiltration of fluoropolymer aqueous dispersion described in US Pat. No. 4,369,226 Can be obtained. The method for removing the fluorine-containing emulsifier is not limited to these.

  A surfactant (fluorinated emulsifier) contained as an emulsifier in an aqueous PTFE dispersion is indispensable because of reaction inactivity in polymerization, but it is difficult to decompose and there is a concern about the influence on the environment. It is desirable to remove as much as possible. Moreover, since the fluorine-containing emulsifier is expensive, it is desirable to collect and reuse it.

In the emulsion polymerization method for obtaining the fluoropolymer aqueous dispersion of the present invention described above, the emulsifier disclosed in US Pat. No. 2,559,752 can be selected and used as the emulsifier. For this purpose, emulsifiers that are sometimes called non-telogenic emulsifiers are preferred, for example, F (CF ₂ ) _n (CH ₂ ) _m COOH having about 6 to 20 carbon atoms, preferably about 6 to 12 carbon atoms. The fluorine-containing alkanoic acid represented by (m: 0 or 1, n: 6-20) or its salt, the fluorine-containing alkylsulfonic acid or its salt, etc. can be mentioned. Examples of the salt include alkali metal salts, ammonium salts, and amine salts. Specific examples include perfluoroheptanoic acid, perfluorooctanoic acid, and salts thereof, 2-perfluorohexylethanesulfonic acid, and salts thereof, but are not limited thereto.

  Furthermore, the fluoropolymer aqueous dispersion of the present invention may contain an emulsion stabilizer in order to improve the stability of the fluoropolymer aqueous dispersion. As the emulsion stabilizer, a hydrocarbon-based anionic surfactant is preferable. This surfactant forms a salt that is insoluble or sparingly soluble in water with calcium, aluminum and iron, which are essentially components in the soil, thus avoiding river, lake and groundwater contamination caused by the surfactant. .

Examples of such hydrocarbon anionic surfactants include higher fatty acid salts, higher alcohol sulfate esters, liquid fatty oil sulfate esters, aliphatic alcohol phosphate esters, dibasic fatty acid ester sulfonates, alkyl allyls. Although there are sulfonates, etc., in particular, polyoxyethylene alkylphenyl ether ethylene sulfonic acid (wherein polyoxyethylene n is 1 to 6, alkyl has 8 to 11 carbon atoms), alkylbenzene sulfonic acid (alkyl has 10 to 10 carbon atoms). 12) and Na, K, Li, and NH ⁴ salts such as dialkylsulfosuccinic acid esters (wherein the alkyl has 8 to 10 carbon atoms) give high mechanical stability to the aqueous PTFE emulsion, and should be exemplified as preferred. I can do it.

  The addition amount of the emulsion stabilizer is 1.0% by weight or more per weight of PTFE, preferably in the range of 1.5 to 5% by weight. When the addition amount is less than 1.0% by weight, the effect of stabilizing the fluoropolymer aqueous dispersion is low, and when the addition amount is 10% by weight or more, it is economically disadvantageous.

  The dust control agent composition of the present invention fibrillates polytetrafluoroethylene by mixing a fluoropolymer with a dusting substance and subjecting the mixture to a compression-shearing action at a temperature of about 20 to 200 ° C. Therefore, it is preferably used in a method for suppressing dust of a dust-generating substance, for example, a method such as Japanese Patent No. 2827152, Japanese Patent No. 2538783 and the like.

  Moreover, the dust suppressing treatment agent composition of the present invention can be used as a fibrillating PTFE described in JP-A No. 2000-185556, JP-A No. 2000-185959, and JP-A No. 2002-60738.

  In the present invention, the dust generating powdery substance to be subjected to dust suppression treatment is an inorganic and / or organic dust generating substance, and the substance, shape, etc. are not particularly limited. The present invention can also be effectively applied to a dusting powdery substance as a dusting substance. Particularly suitable dust generating materials are dust generating materials that are produced in large quantities and are transported in large quantities by ships, freight cars or automobiles. For example, cement powder, slaked lime powder, quick lime powder, calcium carbonate Examples thereof include powder, slag powder, fly ash, gypsum, and particulate metal. Furthermore, various fillers, such as talc, talc, silica, carbon black, various activated carbons, clay, metal oxides, and pigments, can be mentioned.

  The dust suppressing treatment agent of the present invention is suitably used for dust suppressing treatment in the building material field, soil stabilizing material field, solidifying material field, fertilizer field, incineration ash and hazardous substance landfill disposal field, explosion-proof field, cosmetic field, and the like.

  The present invention will be described more specifically with reference to examples and comparative examples below, but this description does not limit the present invention.

In the present invention, each physical property was measured by the following method.
(1) Average particle diameter of fluoropolymer particles The average particle diameter of the fluoropolymer particles was measured by Microtrac UPA150 Model No. It measured using 9340 (made by Nikkiso Co., Ltd.).
(2) Particle size of dust generating powder Using a laser diffraction / scattering particle size distribution measuring instrument manufactured by Horiba, Ltd., ethanol was measured as a dispersion medium.

(3) Standard specific gravity of fluoropolymer Measured by ASTM D-4894.
The PTFE aqueous dispersion obtained by emulsion polymerization is adjusted to a concentration of 15% by weight using pure water. Thereafter, the polymer is aggregated by vigorously shaking about 750 ml in a polyethylene container (1000 ml capacity). The polymer powder separated from the water is dried at 150 ° C. for 16 hours. The dried resin powder 12.0g break were placed in cylindrical mold having a diameter of 2.85Cm, gradually increasing the pressure to a final pressure becomes 350 kg / cm ² after 30 seconds, at a final pressure of 350 kg / cm ² Hold for 2 minutes. The preform thus obtained was fired in an air furnace at 380 ° C. for 30 minutes, cooled to 294 ° C. at a rate of 1 ° C. for 1 minute, held at 294 ° C. for 1 minute, and then from the air furnace. Take out and cool at room temperature (23 ± 1 ° C.) to make a standard sample. The weight ratio of the standard sample to the weight of the same volume of water at room temperature (23 ° C. ± 1 ° C.) is defined as the standard specific gravity.
This standard specific gravity is a measure of the average molecular weight. In general, the lower the standard specific gravity, the higher the molecular weight.

(4) Concentration of fluorinated emulsifier in fluororesin aqueous dispersion The fluororesin aqueous dispersion was frozen in a −20 ° C. freezer, and the fluoropolymer was aggregated and separated from water. Transfer the entire contents of the plastic container to a Soxhlet extractor and extract with about 80 ml of methanol for 7 hours.
Methanol used for extraction is distilled with an evaporator and concentrated to 50 ml or less. Concentrated methanol is placed in a 50 ml volumetric flask and diluted with pure water. The sample solution that has been made up is subjected to a liquid chromatograph for measurement, and the concentration of the fluorinated emulsifier in the aqueous fluororesin dispersion is calculated.

(5) Amount of falling dust 200 g of the sample is naturally dropped from the top inlet of a cylindrical container having an inner diameter of 39 cm and a height of 59 cm, and the amount of suspended dust (relative concentration (CPM: Count per minute) in the container at a height of 45 cm from the bottom. ) Is measured with a scattered-light digital dust meter, and the amount of airborne dust is measured five times for 1 minute after the sample is added, and the geometric average value obtained by subtracting the measured value (dark count) before the sample is added. Is the “falling dust amount.” The geometric mean value x is determined by the following equation.
Log x = 1/5 · Σlog (xi-d)
Here, xi: individual suspended dust amount, d: dark count.

(material)
The raw materials used in the examples and comparative examples of the present invention are as follows.
(1) PTFE aqueous dispersion (I)
(Average particle size 0.2 μm, resin solid content concentration 30 wt%, fluorine-containing emulsifier content 21 ppm, specific gravity 2.19, anionic surfactant is included 3.5 wt% with respect to the weight of PTFE)
(2) PTFE aqueous dispersion (II)
(Mitsui DuPont Fluorochemicals, 312-J, fluorine-containing emulsifier content 1040 ppm, specific gravity 2.19, containing 3.0% by weight of anionic surfactant based on the weight of PTFE)
(3) Powdered quicklime (CaO 93.5%, MgO 4.2%)
Powdered lime with a 300 μm standard mesh screen throughout, 150 μm standard screen screen residue 0.04%, 90 μm standard screen screen residue 0.17%, 90 μm standard screen screen through 99.83% Normal Portland cement (manufactured by Taiheiyo Cement)
(5) Type II anhydrous gypsum (average particle size 9.0 μm, maximum particle size 101 μm)
(6) Granulated blast furnace slag powder (average particle size 8.9 μm, maximum particle size 100 μm)

Example 1
1. 1,000 g of powdered quicklime was put into a small soil mixer having a volume of 5 liters and stirred at a rotational speed of 140 rpm, 1.67 g of PTFE aqueous dispersion (I) (PTFE resin solid content 0. (Corresponding to 05% by mass) was gradually added to a dispersion of 98.8 g of fresh water.
About 1 minute after the start of charging, steam started to be generated due to the heat of hydration reaction of quick lime, and after about 2 minutes, all of the water was used up for the production of slaked lime due to the hydration of quick lime, and the generation of water vapor was eliminated. After 5 minutes from the start of stirring, stirring of the mixer was stopped. The temperature at this time was 95 ° C. when measured with a mercury thermometer. The quicklime subjected to the dust suppression treatment was a mixture of quicklime and slaked lime containing about 30% of slaked lime newly generated by a hydration reaction. The amount of falling dust of the quicklime that had been dust-suppressed was measured. The results are shown in Table 1.

(Example 2)
Dust in the same manner as in Example 1 except that a dispersion obtained by dispersing 1.00 g of PTFE aqueous dispersion (I) (corresponding to 0.03% by mass of PTFE resin solid content with respect to quicklime) in 99.3 g of fresh water was used. Inhibited quick lime was obtained. The amount of falling dust of the obtained quick lime subjected to the dust suppression treatment was measured. The results are shown in Table 1.

(Example 3)
This is a method of heating dust from ordinary Portland cement (dust generating powder) using the heat of hydration reaction of quicklime and performing dust suppression treatment.
100 g of powdered quicklime was put into a small soil mixer having a volume of 5 liters and stirred at a rotational speed of 140 rpm, 1.67 g of PTFE aqueous dispersion (I) (PTFE resin solid content 0.05 mass relative to quicklime) %) Was gradually added to 35.0 g of fresh water.
About 1 minute after the start of charging, steam started to be generated due to the heat of hydration reaction of quick lime, and after about 2 minutes, all of the water was used up for the production of slaked lime due to the hydration of quick lime, and the generation of water vapor was eliminated. After 5 minutes from the start of stirring, stirring of the mixer was stopped. The temperature at this time was 95 ° C. when measured with a mercury thermometer. The quicklime subjected to the dust suppression treatment was a dumpling mixture of quicklime and slaked lime containing slaked lime newly generated by a hydration reaction.

  Using this as a master of the master batch, 900 g of ordinary Portland cement was gradually added while stirring with a small soil mixer (rotation speed 140 rpm). Mixing of ordinary Portland cement was stopped after about 5 minutes. The temperature at this time was 57 ° C. when measured with a mercury thermometer. The amount of falling dust of the ordinary Portland cement subjected to the dust suppression treatment was measured. The results are shown in Table 1.

(Examples 4 to 6)
200 g of the dusting powder shown in Table 1 was preheated to 90 ° C. with an electric heating dryer. 20 g of heated dusting powder and a PTFE aqueous dispersion (I) having a solid content ratio (mass%) shown in Table 1 were heated in advance by an electrothermal dryer at 90 ° C. to a volume of 1 liter of alumina. Mixing and stirring for about 5 minutes in a mortar gave a mixture. The obtained mixture was used as a master, and the remaining 180 g of the heated dust generating powder was added to the master and mixed and stirred for about 5 minutes to obtain a dust generating powder subjected to dust suppression treatment. The amount of falling dust of the resulting dusting powder was measured. The results are shown in Table 1.

(Comparative Example 1)
The amount of falling dust of quicklime was measured. The results are shown in Table 1.

(Comparative Example 2)
The amount of falling dust of normal Portland cement was measured. The results are shown in Table 1.

(Comparative Example 3)
The amount of falling dust of type II anhydrous gypsum was measured. The results are shown in Table 1.

(Comparative Example 4)
The amount of falling dust of granulated blast furnace slag powder was measured. The results are shown in Table 1.

(Reference Example 1)
Dust in the same manner as in Example 1 except that a dispersion in which 1.67 g of PTFE aqueous dispersion (II) (corresponding to a solid content of PTFE resin of 0.05% by weight of quicklime) was dispersed in 98.8 g of fresh water was used. Inhibited quick lime was obtained. The amount of falling dust of the obtained quick lime subjected to the dust suppression treatment was measured. The results are shown in Table 1.

(Reference Example 2)
Dust in the same manner as in Example 1 except that 1.00 g of PTFE aqueous dispersion (II) (corresponding to 0.03% by mass of PTFE resin solid content with respect to quicklime) was dispersed in 99.3 g of fresh water. Inhibited quick lime was obtained. The amount of falling dust of the obtained quick lime subjected to the dust suppression treatment was measured. The results are shown in Table 1.

(Reference Examples 3-5)
Except for using the PTFE aqueous dispersion (II), dust-generating powders with reduced dust were obtained in the same manner as in Examples 4-6. The amount of falling dust of the resulting dusting powder was measured. The results are shown in Table 1.

According to the present invention, there is provided a dust suppression treatment agent comprising a fluoropolymer aqueous dispersion having a high dustproof effect and a low possibility of environmental problems.

Claims (7)

An aqueous dispersion of polytetrafluoroethylene having a fluorine-containing emulsifier content of 50 ppm or less, wherein the polytetrafluoroethylene has a specific gravity of 2.27 or less and an average particle size of 0.1 to 0.5 μm Comprising a fluoropolymer aqueous dispersion containing a hydrocarbon-based anionic surfactant as an emulsion stabilizer , mixed with a dusting substance, and compressed into the mixture at a temperature of about 20 to 200 ° C. A dust suppressing treatment agent composition used for fibrillating polytetrafluoroethylene by applying a shearing action to suppress dust of a dust generating substance.   The dust control agent composition according to claim 1, wherein the specific gravity of the polytetrafluoroethylene is 2.22 or less.   The dust-controlling agent composition according to claim 1 or 2, wherein the fluorinated emulsifier is an anionic fluorinated emulsifier.   2. The aqueous fluoropolymer dispersion is obtained by removing a fluoroemulsifier from an aqueous polymer dispersion obtained by polymerizing tetrafluoroethylene using a fluoroemulsifier. The dust suppression processing agent composition in any one of -3. The dust control method for dusting substances according to claim 1, wherein the hydrocarbon-based anionic surfactant is 1.0 wt% or more and less than 10 wt% per weight of polytetrafluoroethylene. .   The dust generating material is cement powder, slaked lime powder, quick lime powder, calcium carbonate powder, slag powder, fly ash, gypsum, particulate metal, talc, silica stone, carbon black, various activated carbons, metal oxidation The dust control agent composition according to any one of claims 1 to 5, wherein the dust control agent composition is selected from products and pigments.   The dust control agent composition is used in the building materials field, the soil stabilizer field, the solidified material field, the fertilizer field, the landfill disposal field of incinerated ash and harmful substances, the explosion-proof field, or the cosmetic field. The dust control agent composition as described in 1.