JPH08299725A - Production of dust collecting filter cloth - Google Patents

Abstract

PURPOSE: To provide a production method of filter cloth in which a nonwoven fabric sheet comprising ultra-fine fibers and a needle felt are joined into one body by needle punching and the needle holes produced on the nonwoven fabric sheet surface by punching are sealed to improve the surface smoothness while the surface trapping property for fine particles is not lost. CONSTITUTION: A nonwoven fabric sheet 3 comprising ultra-fine fibers and a needle felt 2 are laminated and joined into one body by needle punching. The needle holes 7 remaining on the surface of the nonwoven fabric sheet 3 by needle punching are reduced in size by heating, or the needle holes 7 are closed by melting the structural fibers 6 of the needle felt 2 projecting through the needle holes 7 to the surface of the nonwoven fabric sheet 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter cloth mainly used as a bag filter for collecting dust, particularly suitable for collecting fine particles, and the filter cloth is not clogged with dust and dust is removed. The present invention relates to a method for producing a filter cloth, which is excellent in dropping property and has a stable and stable pressure drop for a long time.

[0002]

2. Description of the Related Art Conventionally, woven fabrics and felts have been mainly used as filter cloths for bag filters. Although these have sufficient strength and shape retention, they collect fine particles such as dyes, cement and toner. Dust was difficult, and it tended to cause clogging and increase the pressure loss of the filter cloth.

Therefore, the inventors of the present invention have disclosed in Japanese Patent Laid-Open No. 3-6071.
As shown in Japanese Patent Publication No. 2, a non-woven fabric sheet made of ultrafine fibers having an average fineness of 0.2 d or less is spot-bonded to the surface of the needle felt to achieve both prevention of clogging by fine particles and strength / shape retention. A filter cloth for dust collection was proposed.

The method disclosed in Japanese Patent Laid-Open No. 3-60712 is a method for laminating and integrating a non-woven sheet and a needle felt, and after applying a thermoplastic or thermosetting resin adhesive to the joint surface or screen coating, Adhesion method, or a method of sandwiching a hot-melt type net-like or non-woven fabric-like binder between them and adhering, and a method of melting the needle felt surface layer without using an adhesive and performing point adhesion. Was there.

In the method of adhering the non-woven sheet and the needle felt by melting the resin adhesive, the non-woven binder and the surface layer of the needle felt, the non-woven sheet and the needle felt may still have insufficient adhesive strength. However, there has been a problem in manufacturing technology for uniform adhesion, or a problem of cost increase due to use of a hot melt binder.

[0006]

Therefore, the present inventors have constructed a non-woven fabric sheet and a needle felt by laminating and integrating them by needle punching to provide a filter cloth having a strong adhesive force and excellent durability without delamination. Found to get.

However, when the non-woven sheet and the needle felt are integrated by needle punching, not only the surface of the non-woven sheet has needle holes and the smoothness of the surface is deteriorated, but also the non-woven sheet made of ultrafine fibers is characterized. This resulted in impairing the surface trapping property of certain fine particles.

In view of the above points, the present invention has a surface smoothness obtained by closing a needle hole formed on the surface of a nonwoven fabric sheet when a nonwoven fabric sheet made of ultrafine fibers and needle felt are integrated by needle punching to obtain a filter cloth. It is an object of the present invention to provide a method for producing a filter cloth that improves the above-mentioned properties and does not impair the surface capturing property of fine particles.

Another object of the present invention is to provide a method of manufacturing a filter cloth which can effectively reduce the size of the needle hole. Another object of the present invention is to provide a method for producing a filter cloth, in which needle holes formed on the surface of a non-woven fabric sheet are melted and blocked by using constituent fibers of needle felt.

[0010]

[Means for Solving the Problems] To achieve the above object, the present invention provides a non-woven fabric sheet composed of ultrafine fibers,
A needle felt is laminated and integrated by needle punching, and the needle holes remaining on the surface of the nonwoven fabric sheet at the time of needle punching can be reduced by heat.

Further, in the present invention, the heat for reducing the needle hole is equal to or higher than the glass transition point of the fibers constituting the nonwoven sheet,
Within the temperature range below the melting point, the shrinking treatment can be effectively performed without deteriorating the fibers.

Further, according to the present invention, a nonwoven fabric sheet made of ultrafine fibers and needle felt are laminated and integrated by needle punching, and needle holes remaining on the surface of the nonwoven fabric sheet at the time of needle punching are passed through the needle holes to make the nonwoven fabric. It is configured such that the constituent fibers of the needle felt protruding to the seat surface are melted and closed.

Furthermore, according to the present invention, a nonwoven fabric sheet made of ultrafine fibers and needle felt are laminated and integrated by needle punching, and the needle holes remaining on the surface of the nonwoven fabric sheet at the time of needle punching are reduced by heat. The constituent fibers of the needle felt protruding to the surface of the nonwoven fabric sheet through the needle hole are melted.

In the above case, the ultrafine fibers constituting the non-woven fabric sheet preferably have an average fiber diameter of 6.0 μm or less. In addition, the needle gauge size is 0. 0 as a condition of needle punching for minimizing the damage of the nonwoven fabric sheet.
75mm or less, the throat depth of the barb shape is 30μ
It is effective to use a needle needle of m or more.

Further, as a method of applying heat for reducing the needle holes remaining on the surface of the nonwoven fabric sheet, hot air setting or hot pressing is suitable. Further, as a method of melting the constituent fibers of the needle felt protruding to the surface of the non-woven fabric through the needle hole, a hot plate heated above the melting temperature of the fibers, a heating roll is brought into contact with the protruding fibers, an infrared heater or a burner, etc. It is better to heat and melt by using.

[0016]

[Operation] While a nonwoven fabric sheet made of ultrafine fibers and needle felt are laminated and integrated by needle punching to increase the peel strength, needle holes are made on the surface of the nonwoven fabric sheet. Is reduced by applying heat within the temperature range from the glass transition point to the melting point of the fibers forming the nonwoven sheet, or by melting the fibers forming the needle felt protruding through the needle hole into the nonwoven sheet surface during needle punching. The needle hole is closed by using the above method, or by using both of these methods in combination, the smoothness of the surface of the nonwoven fabric sheet and the surface trapping property of fine particles can be improved.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a description will be given with reference to the drawings. As shown in FIG. 1, the filter cloth 1 of the present invention is formed by laminating a nonwoven fabric sheet 3 made of ultrafine fibers on the upper surface of a needle felt 2 and integrating them by needle punching. The needle felt 2 has a base cloth 5 and fiber bats 4 and 4 laminated on both sides thereof, which are previously integrated by needle punching.

The needle felt 2 and the non-woven fabric sheet 3
The needle punching is performed by driving the needle N from the side of the needle felt 2 as shown in FIG. 2 and penetrating the non-woven fabric sheet 3 as indicated by a chain line. That is, when the needle N penetrates, the fibers 6 forming the needle felt 2 are anchored by the barbs B formed around the needle N and protrude from the needle hole 7 formed on the surface of the nonwoven fabric sheet 3. By penetrating the constituent fibers 6 of the needle felt 2, sufficient bonding strength between the needle felt 2 and the nonwoven fabric sheet 3 can be obtained.

The needle felt 2 and the non-woven fabric sheet 3
The following points are taken into consideration as conditions for needle punching in order to combine and with a sufficient bonding strength and to make the needle hole 7 as small as possible.

The gauge size of the needle N is 0.75
mm or less (30th count), preferably 0.60 mm or less (36th count), and the throat depth of the barb B of the needle needle N is 30 μm or more, preferably 6
Select one having a thickness of 0 μm or more. This is because if it is less than 30 μm, the effect of catching the batt fibers of the needle felt in the barb is small, and sufficient bonding strength cannot be obtained.

In order to secure a needle-punching depth during needle punching between the nonwoven fabric sheet 3 and the needle felt 2,
The needle needle N has a penetration depth of 3 mm or more, preferably 5 mm or more, starting from the first barb. This is because if the thickness is less than 3 mm, sufficient bonding strength cannot be obtained.

Needle punching density of 100 needles / in ² or more, 4
000 lines / in ² or less, preferably 300 lines / in ² or more and 3000 lines / in ² or less. 100 / in ²
If it is less than 4,000, sufficient bonding strength cannot be obtained. Conversely, if it exceeds 4000 fibers / in ² , the bonding strength is sufficient, but the structure of the fine fibers of the non-woven sheet may be damaged, leading to a decrease in fine particle trapping property. Because there is.

The non-woven sheet 3 is preferably a sheet obtained by a melt-blowing method effective for obtaining ultrafine fibers. Further, a non-woven sheet made of splittable fibers for forming an ultrafine fiber layer by a mechanical means such as carding or needling, or a chemical means such as heat treatment or melting treatment can be used. The basis weight is preferably 30 g / m ² or more and 150 g / m ² or less. If it is less than 30 g / m ² , the strength is insufficient and the damage due to needle punching is large, and the effect of reducing the needle hole by heat treatment is small. 1
If it exceeds 50 g / m ² , it does not particularly affect the fine particle capturing property, but it causes an increase in cost.

Next, as a means for reducing the needle hole 7 formed on the surface of the non-woven sheet 3 by the needle punching, the non-woven sheet 3 is reduced by heat as shown by reference numeral 11 in FIG. 3 to close the needle hole 7. To do so. in this case,
Heat is applied to the nonwoven fabric sheet 3 in a temperature range not lower than the glass transition point and not higher than the melting point of the fibers constituting the nonwoven fabric sheet. In this case, the nonwoven fabric sheet 3 and the needle felt 2 may be shrunk in the same manner. However, since the shrinking effect of the needle hole 7 is larger when the shrinkage of the nonwoven fabric sheet 3 is slightly larger than that of the needle felt 2, It is preferable that the heat shrinkage ratio ≧ (the heat shrinkage ratio of the needle felt).

As a means for closing the needle hole 7 formed on the surface of the nonwoven fabric sheet 3 by the needle punching, the constituent fibers 6 of the needle felt protruding to the surface of the nonwoven fabric sheet through the needle hole are melted, as shown in FIG. Lid 12
Try to do In this case, the non-woven sheet 3
In order to prevent the melting of the fibers, it is necessary to provide a difference in melting point between both fibers so that (melting point of non-woven sheet)> (melting point of needle felt). For example, when a composite fiber having a melting point lower than that of the non-woven sheet is mixed and spun into the fiber bat of the needle felt 2 and the composite fiber is projected onto the surface of the non-woven sheet 3 by needle punching, the above-mentioned melting point difference occurs. , More effective.

The fiber diameter of the fiber butt 4, 4 of the needle felt 2 is preferably 40 μm or less, more preferably 20 μm or less, in consideration of the heat treatment of the fibers protruding on the surface of the nonwoven fabric sheet 3. If it exceeds 40 μm, the heat treatment effect is lowered, and the fibers easily become fluffed, resulting in an adverse effect on the removal property.

In the heat shrinking method, the nonwoven fabric sheet 3 is shrunk by hot air setting or hot pressing so that the area shrinkage rate is 5% or more in the temperature range of the glass transition point (TgN) or higher and the melting point (TmN) or lower. Is essential.

Here, the area shrinkage rate [%] is calculated by (area before shrinkage-area after shrinkage) / (area before shrinkage) × 100.

In the hot pressing method, the temperature of the hot plate in contact with the non-woven sheet 3 is Ta, the temperature of the hot plate in contact with the needle felt 2 is Tb, and Ta is higher than Tb by 30 ° C. or more. It is effective in increasing the shrinkage of the sheet and promoting its densification. That is, Ta ≧ T
b + 30 [° C] and TgN ≦ Ta <TmN.

In the hot-melting method, the needle felt-side bat fibers protruding toward the nonwoven fabric sheet by needle punching are brought into contact with a hot plate or a hot roll heated to a temperature higher than the melting temperature, or an infrared heater or a burner is used. Then, the needle hole 7 is closed by heating and melting.

The surface of the filter cloth obtained by laminating and integrating the non-woven fabric sheet 3 and the needle felt 2 is subjected to a conventional resin processing, for example, a treatment such as a hard finish for increasing strength or pleating molding processing. It goes without saying that there is no restriction as long as the pores formed by the ultrafine fibers of the non-woven fabric sheet are not clogged.

[Example 1] PE on both sides of 100 g / m ² of base fabric made of polyethylene terephthalate (PET)
100 g / m ^{2 of} card webs made of T short fibers (average fiber diameter 17.5 μm) were laminated and needle punched to obtain a PET needle felt having a basis weight of 300 g / m ² .

The above needle felt and basis weight 30 g / m
^2. Laminated PET ultrafine fiber nonwoven fabric sheets with an average fiber diameter of 3.2 μm, using a needle needle having a barb shape with a gauge size of 0.60 mm (36th count) and a throat depth of 50 μm, starting from the first barb. Needle depth 10m
m, needle punching density was 600 / in ² , and needle punching was performed to integrate them.

Then, heat setting was carried out at 180 ° C. for 5 minutes with a hot air dryer, and then 220 ° C. with a hot roll calender.
When a press treatment of × 2 m / min was performed, needle holes on the surface of the non-woven fabric sheet were hardly recognized. The area shrinkage rate after processing was 9.8% after the filter cloth density after pressing was 0.3.
Met. Further, the obtained filter cloth exhibits a bonding strength between the non-woven fabric sheet 3 and the needle felt 2 which is more than twice as high as that of the conventional point bonding method shown in [Comparative Example-1] to be described later, and has durability. Has improved.

The particle-capturing property (≈dust-collection efficiency) in the dust-collection test was significantly improved by laminating the ultrafine fiber layers. In particular, the amount of blowout is only 1 with the needle felt of the material.
It was reduced to about 1/10 of [Comparative Example-6] in which 4.40 mg / m ³ was recorded. Moreover, the same performance was exhibited as compared with the filter cloth obtained by the conventional spot adhesion method [Comparative Example-1] (see FIG. 5).

Example-2 PET base cloth 100 g / m ²
100 g / m ^{2 of a} card web made of nylon 6 short fibers (fiber diameter 19.3 μm) were laminated on both sides of the above and needle punched to obtain a needle felt having a basis weight of 300 g / m ² .

The above-mentioned needle felt and a basis weight of 30 g /
m ² and a nonwoven fabric sheet made of PET ultrafine fibers having an average fiber diameter of 3.2 μm were laminated and joined and integrated under the same needle punching conditions as in Example 1 above.

After that, the felt side batt fibers protruding on the surface of the non-woven sheet are heated and melted by contacting with a hot plate heated to 230 ° C., and further heated at 160 ° C. × 2 m / min with a hot roll calender. A press treatment was applied to give a filter cloth density of 0.3.

The area shrinkage rate after the treatment was 3.0%, but the nylon 6 fibers on the felt side protruding onto the non-woven fabric sheet were melted by the melting treatment of the fluff, and the effect of closing the needle hole 7 was high. The dust collection efficiency was obtained.

[Example 3] The same needle felt and non-woven fabric sheet as in [Example 1] above were laminated and a barb-shaped needle needle having a gauge size of 0.45 mm and a throat depth of 35 µm was used. Needle punching with a needle depth of 8 mm and a needle punching density of 1600 needles / in ² was performed starting from 1 barb to join and integrate them. This is heat-treated under the same conditions as in [Example-1] above, and the area shrinkage ratio is set to 9.
It was set to 1%.

[Example-4] PET base cloth 100 g / m ²
Both sides of PET short fiber and PET-based core-sheath type composite fiber (melting point of sheath 140 ° C, trade name = Yumetikameruti)
50/50 mixed card web 100 g / m ²
(Average fiber diameter 19.0 μm) were laminated and needle punched to obtain a PET needle felt having a basis weight of 300 g / m ² . The same non-woven fabric sheet as in [Example 1] was used for this, and needle punching was performed under the same needle conditions to join and integrate them.

The heat treatment was also carried out in the same manner as in [Example-2], and the area shrinkage ratio after the treatment was 4.0%. The obtained filter cloth had the effect of closing the needle hole by melting the low melting point fibers protruding toward the non-woven fabric sheet side, and had high dust collection efficiency and strong bonding strength.

[Comparative Example-1] The same needle felt and non-woven fabric sheet as in [Example-1] above were used, and a hot melt mesh (PET type, basis weight 20 g /
m ² and Tm 160 ° C), and heat roll press 1
Spot adhesion was carried out at 80 ° C. × 2 m / min. The bonding strength between the nonwoven fabric sheet of the filter cloth and the needle felt thus obtained was 0.6 kg / 5 cm.

[Comparative Example-2] The same needle felt, non-woven fabric sheet and needle as those used in [Example-1] were used. The needle conditions were a needle depth of 2 mm (from the first barb starting point) and a needle punching density. Bonding was performed at 3000 lines / in ² . The heat treatment was performed in the same manner as in [Example-1] to obtain a filter cloth. The interlayer bond strength of this filter cloth is 0.2 kg / 5 cm
Was low and the joining strength was insufficient.

[Comparative Example-3] The same needle felt, nonwoven fabric sheet and needle as those used in [Example-1] were used, and the needle conditions were a needle depth of 12 mm (from the first barb starting point) and a needle punching density. The pieces were joined and integrated at 5000 pieces / in ² , and the same heat treatment as in [Example-1] was performed.

[Comparative Example 4] The same needle felt and non-woven fabric sheet as in [Example 1] above were joined and integrated under the same needle conditions, and heated at 160 ° C by a hot roll calender.
A press treatment of × 2 m / min was performed. The area shrinkage after the treatment was 3.0%. In Comparative Example 3, the fiber density of the non-woven sheet was damaged because the needle punching density was too high, and in Comparative Example 4, the needle hole remained in the non-woven sheet because the shrinkage was small, and the dust collection efficiency was low. Further, Comparative Example-3 showed a tendency that the pressure loss of the filter cloth was high.

[0047] and the same needle felt as Comparative Example -5] above Example -1], basis weight F10G / m ^2, a nonwoven sheet of PET ultrafine fibers having an average fiber diameter of 3.2μm stacked, Example - Processing was performed under the same needle conditions and heat treatment conditions as in 1). The area shrinkage rate after such treatment was 9.8%, but the obtained filter cloth had a small basis weight of the nonwoven fabric sheet and had insufficient strength, so that the damage due to needle punching was large and the dust collection efficiency was lowered.

[Comparative Example-6] The same needle felt as in [Example-1] was treated under the same heat treatment conditions as in [Example-1] to obtain the same filter cloth density as in [Example-1]. I adjusted it so that The dust collection efficiency of only this needle felt was low as shown in FIG.

Next, using the filter cloths of the present invention of [Examples 1 to 4] and the filter cloths of [Comparative Examples 1 to 6], a repeated filtration-shredding test was conducted under the following conditions. The change in cloth pressure loss, the amount of dust leak, the dust collection efficiency, and the dust removal rate were calculated, and the results are shown in FIG.

[Filtration-Shaping-off Repeated Test] Filtration air flow rate: 7.9 × 10 ⁻² m ³ / min Filtration area: 1.7 × 10 ⁻² m ² dust; JIS-10 seed powder (fly ash) pulse Pressure: 4 kg / cm ² pulse time: 0.5 seconds Test method: Filter cloth pressure loss (ΔP): 200 mmH ₂ O
After performing "filtration" up to, stop the filtration and repeat "pulse removal".

[0051]

[0052]

[0053]

In FIG. 5, the joint strength between the non-woven fabric sheet 3 and the needle felt 2 is measured by the T-type peel test method (JIS.
-K6854) was also described.

[0055]

As described above, according to the present invention, a nonwoven fabric sheet composed of ultrafine fibers and a needle felt are laminated,
Since they are integrated by needle punching, as compared with the conventional point bonding method, a binder is not used, so that a filter cloth which is inexpensive, has a strong bonding force, and is excellent in durability can be manufactured at low cost.

When the non-woven sheet and the needle felt are joined by needle punching, the needle holes remaining on the surface of the non-woven sheet are reduced by heat and closed.
The surface smoothness is improved, and the excellent fine particle surface-capturing property of the nonwoven fabric sheet made of ultrafine fibers is obtained.

Further, when the heat for reducing the needle holes is in the temperature range from the glass transition point of the fibers constituting the nonwoven fabric sheet to the melting point thereof, the effect of reducing the needle holes can be further enhanced.

Furthermore, according to the present invention, when the needle holes remaining on the surface of the non-woven fabric sheet during needle punching are melted and occluded by the constituent fibers of the needle felt protruding to the surface of the non-woven fabric sheet through the needle holes, the non-woven fabric is formed by needle punching. The felt fibers on the surface of the sheet are heat-treated and melted to prevent fluffing on the surface, improving durability, and surface smoothness by closing the needle holes as when shrinking. And the excellent surface-capturing property of fine particles of the non-woven fabric sheet made of ultrafine fibers can be obtained. Particularly, when a low melting point fiber is mixed-spun in the felt, a more remarkable effect can be expected.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing a filter cloth according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view schematically showing a state of a needle hole immediately after joining a nonwoven fabric sheet made of ultrafine fibers and a needle felt by needle punching.

FIG. 3 is a cross-sectional view schematically showing a state in which a needle hole is reduced by heat treatment.

FIG. 4 is a cross-sectional view schematically showing a state in which fibers on the needle felt side protruding from the surface of the nonwoven fabric sheet are melted to close the needle holes.

FIG. 5 is a table showing the results of filtration-scraping repetition test and bond strength peeling test using the filter cloths of Examples-1 to 4 and Comparative Examples 1 to 6.

[Explanation of symbols]

1 Filtration Cloth of the Present Application 2 Needle Felt 3 Nonwoven Sheet 4 Fiber Bat 5 Base Fabric 6 Constituent Fiber of Needle Felt Protruding on the Nonwoven Sheet Surface 7 Needle Hole 11 Reduced Needle Hole 12 Lid that closes the needle hole N Needle needle B barb

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area // B01D 46/54 B01D 46/54

Claims (3)

[Claims] 1. A non-woven sheet made of ultrafine fibers and a needle felt are laminated and integrated by needle punching, and the needle holes remaining on the surface of the non-woven sheet during the needle punching are reduced by heat. A method for manufacturing a filter cloth for collecting dust. 2. The filter cloth for dust collection according to claim 1, wherein the heat for reducing the needle holes is in a temperature range of not less than the glass transition point and not more than the melting point of the fibers constituting the nonwoven fabric sheet. Manufacturing method. 3. A non-woven sheet made of ultrafine fibers and a needle felt are laminated and integrated by needle punching, and needle holes remaining on the non-woven sheet surface at the time of needle punching are passed through the needle hole to the non-woven sheet surface. A method for producing a filter cloth for dust collection, which comprises melting and closing the protruding constituent fibers of the needle felt.