JPH0363405B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a woven fabric or a nonwoven fabric as a base material, which has an open pore structure of a thermoplastic resin or a thermosetting resin containing a fibrous or particulate conductive filler on one side. The present invention relates to a method for manufacturing a bag filter cloth that has porous polymer layers laminated together and has excellent surface conductivity and dust collection efficiency.

In air filters, which are generally used in air conditioning, etc., static electricity is generated in the filter medium to increase dust collection efficiency. It is preferable to reduce the amount of charge as much as possible for the purpose of eliminating safety and health hazards such as electrostatic shock and electric shock.

In order to suppress the generation of static electricity in such fiber aggregates, there are two methods: 1. A method of reducing friction and preventing static electricity using an oil agent.

2. A method that uses an antistatic agent to impart conductivity to the surface of fibers and prevent the accumulation of electric charge.

3. A method of coating the surface of fibers with a conductive substance to prevent static electricity.

4. A method of blending hydrophilic polymers or conductive substances into fibers to modify the fibers themselves to prevent static electricity.

5. A method of blending conductive fibers such as metal fibers and carbon fibers to prevent static electricity.

However, methods 1 and 2 require harsh conditions for using the filter cloth, and it is not as durable as textiles for general clothing. Since the properties are more strongly required, a sufficient antistatic effect cannot be expected.
Method 4 is a very good method compared to methods 1 and 2, but it cannot be used when the heat resistance or chemical resistance is inferior to that of the main fibers constituting the filter cloth. Method 3 is an effective method for preventing static electricity because it is sufficient to treat the main fibers constituting the filter cloth. Method 5 is an effective antistatic method as well as method 3, and its advantages over method 3 are that there is no problem of peeling of the coating, and metal fibers and carbon fibers make up the filter cloth. It has superior heat resistance and chemical resistance compared to conventional fibers. However, in the conventional methods 1 to 5 shown above, it is not possible to satisfy the other conditions required for the bag filter cloth at the same time.

Other important conditions required for bag filter cloth include: 1. Good removability of dust accumulated on the surface of bag filter cloth.

2. Low pressure loss.

3. High dust collection rate.

There is. To meet these conditions, bag filter cloth for dust collection has been developed in the past, in which a polymer containing a continuous pore structure is laminated on one side of a woven or non-woven fabric. 52-80579), the polymer layer containing a continuous pore structure has electrical conductivity and lowers the surface resistivity value, increasing dust collection efficiency and reducing friction during powder transportation, powder and bag filters. A bag filter cloth that prevents the generation of static electricity caused by friction during collision with cloth, friction between bag filter cloth and bag filter cloth or metal parts, and eliminates the risk of dust explosion has not yet been developed.

On the other hand, by adding carbon fiber, metal-coated glass fiber, finely powdered carbon black, etc. to polymers to give them conductivity, they prevent the generation of static electricity and protect electronic components. When such fibrous conductive filler or finely powdered carbon black is mixed into the material, it takes a long time to obtain a uniform dispersion state. In order to obtain a uniform dispersion state in a short time, there is a method of adding a large amount of oil or wax. however,
The polymer layer containing the conductive filler obtained by this method has a significant decrease in physical properties such as abrasion resistance.
Bug filter cloth cannot maintain sufficient durability against the external forces it receives during use. However, in order to obtain sufficient safety against static electricity, bag filter cloth requires a surface resistivity value of 10 ⁴ Ω or less, and in order to satisfy this value, it varies depending on the type of resin. However, the fibrous conductive filler must be contained in an amount of 5% by weight or more based on the weight of the resin, and the finely powdered carbon black must be contained in an amount of 15% by weight or more.

In order to solve this problem in the present invention,
By dispersing the conductive filler in water using a surfactant in advance and adding the aqueous dispersion of the conductive filler to the resin, uniform dispersion can be obtained in a short time, thereby containing the conductive filler, Moreover, it was possible to obtain a bag filter cloth having a surface resistivity value of 10 ⁴ Ω or less, which is formed by integrally laminating polymer layers containing a continuous pore structure.

The present invention will be explained in detail below.

As the resin used in the present invention, any resin that is stably dispersed in water can be used, and a resin in the form of an emulsion is most preferred. For example, styrene butadiene rubber, acrylonitrile butadiene rubber, acrylic ester resin, polyester resin, polyurethane resin,
polyamide resin, silicone resin, acrylic resin,
Futsuso resin, phenolic resin, epoxy resin,
It is an emulsion such as a copolymer of these resins.

In addition, the polymer laminated to the woven fabric or non-woven fabric that is the base material of the bag filter cloth of the present invention is made of a resin that has superior properties such as heat resistance and chemical resistance to the main fibers that make up the woven fabric or non-woven fabric. It is preferable that The fibers constituting the woven or nonwoven fabric include general synthetic fibers such as polyethylene fiber, polypropylene fiber, polyamide fiber, polyester fiber, polyacrylonitrile fiber, and natural fibers such as wool, cotton, or heat-resistant organic fiber. In addition to polybenzimidazole fiber, polyphenylene sulfite fiber, Conex (trade name of heat-resistant nylon manufactured by Teijin Ltd.), glass fiber, carbon fiber, etc. can be used.

The mechanical strength required for the bag filter cloth of the present invention can be achieved mainly by the woven fabric or nonwoven fabric that is the base material, so the laminated polymer layer and the main fibers constituting the base material It is necessary to sufficiently increase the adhesive strength of the Preferably, a resin that can provide the necessary adhesive strength to the fibers constituting the base material should be used, but if the required adhesive strength cannot be obtained, a resin that does not excessively impair breathability should be used. Infiltrate the resin in the thickness direction of the base material to form a three-dimensional network structure in the base material to obtain peeling resistance, or apply adhesive strength to the main constituent fibers that make up the base material in advance. It is desirable to obtain high adhesive strength by applying surface treatment to increase the adhesive strength.

As a surface treatment agent for the base material, an organic silane coupling agent, a chromium-based adhesion promoter, an organic titanium-based adhesion promoter, etc. can be used.
As the organic silane coupling agent, γ-glycidoxypropyltrimethoxysilane, vinyltriethoxysilane, etc. can be used. As the organic titanium adhesion promoter, tetraisopropyl titanate, tetrabutyl titanate, etc. can be used.

In order to form a polymer layer with an open pore structure according to the present invention, a conductive filler and various additives are added to the resin as described above to prepare a foamable composition, and mechanical force is applied to the polymer layer. After foaming to a predetermined magnification, the foam is applied to a base.

First, regarding the conductive filler added to the resin, carbon fiber, metal fiber, metal-coated glass fiber, etc. can be used as the fibrous conductive filler, and the amount added is determined by the surface resistivity value.
This is the amount necessary to reduce the resistance to 10 ⁴ Ω or less. The required amount differs depending on the type of resin, and
It is 5.0 to 25.0% by weight. Further, carbon black as a fine powder conductive filler is a furnace black manufactured by a furnace method, a channel black manufactured by a contact method, etc., and preferably has a large specific surface area.
Carbon blacks produced by the furnace method that can provide high conductivity with a small amount added to the resin, such as super contact furnaces, electric conductive furnaces, Kettien blacks (manufactured by Lion-Akzo), and acetylene blacks. be. Also, when using a fibrous conductive filler and carbon black, which is a particulate conductive filler, the total amount of both added to the resin should be within the above range of addition so that the surface resistivity value is 10 ⁴ Ω or less. It is important to add it, and whatever the ratio, it is sufficient that the surface resistivity value is 10 ⁴ Ω or less.

These conductive fillers are prepared by dispersing a surfactant such as highly condensed naphthalene sulfonic acid sodium salt or polycarboxylic acid ammonium salt in water containing about 0.5 to 2.0% by weight, and adding the aqueous dispersion to the resin. . By doing so, the conductive filler can be uniformly dispersed in the resin in a short period of time, without causing any significant deterioration in the physical properties of the foamed polymer layer.

Next, various additives will be described.

In order to form a polymer layer having an open pore structure according to the present invention, various additives are added to the resin in which the conductive filler is uniformly dispersed to prepare a foamable composition, and mechanical force is applied to the resin. After foaming to a predetermined magnification using the foam, coating is performed on the base material. Foamable compositions are prepared by adding blowing agents, foam stabilizers, thickeners, etc. to the resin. When using a resin that forms an emulsion using a surfactant, the surfactant used plays the role of a foaming agent, so it is often not necessary to add it. When added, many types of surfactants can be used as blowing agents, such as fatty acid salts, inorganic ester salts of fatty acid alcohols such as ammonium lauryl sulfate, sulfonated paraffinic hydrocarbon salts, and fluorocarbon surfactants; A mixture of these may be used.
Foam stabilizers are used to obtain foam stability,
For example, lauryl alcohol, sodium laurate, lower aliphatic alcohols, dodecyl alcohol, lower aliphatic salts, lauric acid, fatty acids, and mixtures thereof are used.

Thickeners that can be mixed with foaming agents and foam stabilizers to form a viscous product together with them include sodium polyacrylate, acrylic acid copolymers, polyvinyl alcohol, natural gums, and starches. , cellulose derivatives and mixtures thereof are used. Preferably, one that does not significantly increase the tackiness of a polymer layer formed from a composition containing a thickener upon heating or humidification is suitable. For example, polyacrylic acid or sodium polyacrylate can provide a thickening effect in small amounts and does not significantly increase the tackiness of the polymer layer upon heating or humidification. Although cellulose derivatives are easy-to-handle thickeners, their viscosity increases due to moisture absorption, which increases their ability to adsorb dust, resulting in clogging of the pore structure of the polymer layer and deterioration of dust removal performance. Therefore, when a cellulose derivative is used as a thickener, a fluorine-based or silicone-based water repellent agent is also used. When the mucilage is prepared, thickeners, foam stabilizers, and blowing agents are premixed in proportions that vary widely depending on the desired properties of the final foam.

The foamable composition for forming the polymer layer of the present invention contains approximately 10-30% resin by weight, a foam stabilizer approximately 0.5-5.0% by weight, and a thickener by weight. Contains approximately 0.1 to 2.0%. Preferably, the weight ratio of foam stabilizer to thickener is from 25:1 to 3:1, with the thickener being 0.1 to 1.0%.
A range of is desirable. Additional substances such as PH stabilizers such as bases or acids, inorganic additives for increasing the heat distortion temperature, etc. can also be incorporated into the foamable composition. Inorganic additives such as mica, calcium carbonate, and talc are used to increase heat resistance and reduce the stickiness of the laminated polymer layers.

It is important that the additionally added substances do not significantly deteriorate the physical properties of the polymer layer, and the amount of inorganic substances added must be kept at a weight ratio of 5:1 or less to the resin. Typical liquid media used in foamable compositions include water, methanol, and the like.

A foamable composition formed of a resin, a conductive filler, various other additives and a liquid medium is
After the addition of the liquid medium, foaming is carried out to a predetermined foaming ratio using a mechanical foaming machine (for example, a foaming machine manufactured by Mihiro Kakuki Co., Ltd.). The foaming ratio is 2 to 5.
2.5 times to 3.5 times, preferably 2.5 times to 3.5 times. The expansion ratio is determined by measuring the weight of a given volume of foam compared to the weight of the same volume of the composition before foaming. The density of the foam generally ranges from 0.2 to 0.5 g/cc, preferably from 0.28 to 0.4 g/cc.

Bag filter cloth is required to have a surface resistivity of 10 ⁴ Ω or less and to be breathable.
Although it depends on the size of the dust, bag filter cloth generally has an air permeability of 5 to 13 c.c./sec/cm ² (Frangier type air permeability tester: JIS L-1096-6-27)
-1A method) is said to have the highest performance in terms of dust collection efficiency and power load (pressure loss) balance.

In order to reduce the pressure loss of the bag filter cloth, which is one of the objectives of the present invention, it is necessary to collect dust mainly using a polymer layer integrally laminated on the base material. The thickness of the combined layer is
In the range of 0.1mm to 0.5mm, the pore size is 1.0μ to 50.0μ
A range of 1 is desirable. Preferably the thickness is 0.15
mm to 0.25 mm, and the pore size of the pores ranges from 3.0 μ to 20.0 μ. Therefore, in order to obtain an air permeability of 5.0 to 13.0 cc/sec/cm ² , the woven or nonwoven fabric serving as the base material should have an air permeability of 15.0 to 30.0 cc/sec/cm ² .

The foam is applied onto a substrate, but the foam must be sufficiently stable and suitable for application to the substrate, woven or nonwoven. It is important that the foam is not destroyed, especially between the time it is applied to the substrate and the time the foam is dried and set. The amount of the foam applied to the substrate is 30 to 100 g/m ² , preferably 40 to 70 g/m ² . The thickness of the foam immediately after being applied to the substrate is 0.7 mm to 1.0 mm, and in order to obtain the desired air permeability as mentioned, the thickness of the polymer layer is reduced to 0.15 mm by pressing. ~0.25
compressed to mm.

As explained above, the present invention is a bag filter in which a polymer layer having a continuous pore structure containing a fibrous or finely powdered conductive filler is laminated on one side of a woven or nonwoven fabric as a base material. It has better conductivity than conventional bag filter cloth, and because the conductive filler is uniformly dispersed, there is no significant decrease in the mechanical strength of the polymer layer, and it has a continuous pore structure. Since dust is collected in the polymer layer, dust can be easily brushed off and pressure loss is reduced, providing performance not found in conventional bag filter cloths.

Examples of the bag filter cloth of the present invention obtained as described above are shown in FIGS. 1 and 2. 1st
The figure shows an enlarged cross-section of a bag filter cloth of the present invention in which a polymer layer 4 containing a fibrous conductive filler 3 and having a continuous pore structure 2 is integrally laminated on one side of a woven fabric 1. This figure shows an enlarged cross section of another embodiment of the bag filter cloth of the present invention, in which a polymer layer 8 containing a fine powder conductive filler 7 and having a continuous pore structure 6 is integrally laminated on the surface of a nonwoven fabric 5. . Furthermore, in the bag filter cloth of the present invention, the surface state of the polymer layer having a continuous pore structure formed on the base material is shown in FIG. Figure 3A is a drawing showing the surface state of the bag filter cloth of the present invention magnified 75 times, and Figure 3B is
A similar drawing enlarged 150 times.

The present invention will be explained below with reference to Examples.

To measure the surface resistivity value in each example, electrodes were made into two types of rings using silver paste (for example, Dotite, manufactured by Fujikura Kasei Co., Ltd.), and the distance between the electrodes was 5.0 mm. did. Further, the voltage at the time of measuring the electrical resistance was 100 V, and the logarithmic average value of the measured values at 10 locations was taken as the surface specific resistance value of the bag filter cloth.

Example 1 20 parts by weight of a conductive filler aqueous dispersion in which 7 parts by weight of acetylene black was dispersed in water containing 2.0% by weight of highly condensed naphthalene sulfonic acid sodium salt (solid content of acetylene black 35% by weight) was mixed with 35 parts by weight. modified acrylic ester resin emulsion (solid content 35% by weight), and after uniformly dispersing, 5 parts by weight of methylolmelamine (purity content 50% by weight), 1 part by weight of sodium polyacrylate (thickener) A foamable composition was prepared by mixing 4 parts by weight of sodium laurate (foam stabilizer), 3 parts by weight of mica (inorganic additive), and 32 parts by weight of water. The total solids content in this formulation was 28.5% by weight. In this case, there is no particular need to add a blowing agent, and the surfactant added to make the resin into an emulsion type plays the role of a blowing agent. If foaming is insufficient, ammonium stearate can be added in an amount of 0.1 to 0.3% by weight based on the foamable composition. This composition was foamed to a 3x expansion ratio using a mechanical foamer. This foamed composition was applied in an amount of 50 g/m ² by knife coating onto a nonwoven fabric made by needle punching as a base material. The nonwoven fabric used is made of polyester and has a basis weight of 490g/
^m2 , air permeability is ^{26c.c./sec/cm2} , thickness is 1.8mm
It was hot. 5 at 120℃ immediately after coating.
Dry for a minute. Thereafter, curing was carried out at 160° C. for 2 minutes, and then the approximately 0.8 mm polymer layer was compressed by rolls to approximately 0.2 mm to provide the desired air permeability and pore size. The air permeability of the bag filter cloth made in this way is approximately 11.0cc/
sec/cm ² , the surface specific resistance value was 0.4×10 ⁴ Ω, the frictional charging voltage was 25 V (JIS L-1094 (1980) 8.1.A method), and the half-life was so short that it could not be measured (JIS L-1094 (1980) 8.1.A method). −1094 (1980)
Method 8.1.B) Bag filter cloth made from conventional polyester fibers without antistatic treatment had a charging voltage of 5700V and a half-life of 180 seconds.
In dust collection of pulverized coal, the present invention and the conventional product were used in two ways.
After using the product for a month, the pressure loss was 15 to 17 cm in water column for the product of the present invention, and 20 to 23 cm for the conventional product. In addition, the amount of dust accumulated is 215g/m ² for the product of the present invention.
In contrast, the conventional product had a weight of 380 g/m ² . The form of shedding was done with counter pressure.

Example 2 25 parts by weight of a conductive filler aqueous dispersion (solid content 30% by weight), in which 7.5 parts by weight of acetylene black was dispersed in water containing 20% by weight of highly condensed naphthalene sulfonic acid sodium salt, was mixed with 40 parts by weight of Polychem Supplement. 110
(Product name of silicone and acrylic acid ester copolymer emulsion manufactured by Nippon Pure Chemical Industries, Ltd.: Solid content 35
% by weight), and after uniformly dispersing, 6 parts by weight of sodium laurate (foam stabilizer), 1 part by weight of acrylic ester emulsion, (thickener), 6 parts by weight of mica (inorganic additive). A foamable composition was prepared by mixing 27 parts by weight of water. Foaming was carried out in the same manner as in Example 1 to a foaming ratio of 3 times, and an amount of 60 g/m ² was applied to the substrate by knife coating. Drying is
Cure was carried out at 120°C for 5 minutes, and curing was carried out at 150°C for 2 minutes. As in Example 1, the polymer layer was compressed to about 0.2 mm to obtain the desired air permeability. The base material used was a nonwoven fabric of Connetex (trade name of heat-resistant nylon manufactured by Teijin Ltd.) made by needle punching, and had a basis weight of 420 g/m ² and an air permeability of 29 c.c. /sec/cm ² , the surface specific resistance value is 0.7×10 ⁴ Ω, and the frictional charging voltage is 20V (JIS
L-1094 (1980) 8.1.A method), the half-life was so short that it could not be measured (JIS L-1094 (1980) 8.2.B method). Voltage is 6500V (JIS L-1094 (1980)
8.1.A method) The half-life was 205 seconds (JIS L-
1094 (1980) 8.2.B Law). The weight of this bag filter cloth is 440g/ ^m2 , the thickness is 1.8mm, and the breathability is 16
It was cc/sec/ ^m2 .

As a result of using the product of the present invention and the conventional product for 10 days to collect dust from exhaust gas from a heavy oil boiler, the pressure loss of the product of the present invention was 25 to 30 cm in the water column, while that of the conventional product was 25 to 30 cm.
It was 28-32cm. The amount of dust accumulated by the product of this invention is
It was 180g/m ² while the conventional product was 240g/m ²
It was hot. The brush-off method was performed using counter pressure.

Example 3 3.5 parts by weight of acetylene black and cut length 1.5 mm
7 parts by weight of carbon fibers were dispersed in water containing 20% by weight of highly condensed naphthalene sulfonic acid sodium salt.
35 parts by weight of an aqueous dispersion of conductive filler (solid content 30% by weight) was mixed with 40 parts by weight of Polychem Sup 110 (manufactured by Nippon Pure Chemical Industries, Ltd., trade name of copolymer emulsion of silicone and acrylic ester: solid content 35). (wt%) and dispersed uniformly, foaming can be achieved by mixing 1 part by weight of acrylic ester emulsion (thickener), 6 parts by weight of mica (inorganic additive), and 31 parts by weight of water. A composition was formed. A product of the present invention was produced using the same method and the same nonwoven fabric as in Example 2. The air permeability of the bag filter cloth made in this way is 9.0 cc/sec/cm ² , the surface specific resistance value is 0.2×10 ⁴ Ω, and the friction voltage is 25 V (JIS L
-1094 (1980) 8.1.A method), and the half-life was so short that it could not be measured (JIS L-1094 (1980) 8.2.B method).
Comparison with conventional products was carried out in the same manner as in Example 2,
Almost the same results were obtained.

[Brief explanation of drawings]

1 and 2 are partially enlarged cross-sectional views showing an example of the bag filter cloth of the present invention, FIG. Figure 3B is a plan view of the same surface enlarged 150 times. 1...Woven fabric, 2,6...Continuous pore structure, 3,7
... Conductive filler, 4, 8 ... Polymer layer, 5...
...Non-woven fabric.

Claims (1)

[Claims] 1. Adding an aqueous dispersion of a conductive filler containing a surfactant to a resin emulsion, then adding an additive and foaming the resulting foam is applied to one side of the base material, dried and fixed, and then compressed to create an open-pore structure. The surface specific resistance value of the polymer layers laminated together is
A method for manufacturing bag filter cloth with a value of 10 ⁴ Ω or less.