JPH08144163A - Warp knitted fabric for filter cloth - Google Patents

Abstract

PURPOSE: To provide a warp-knitted fabric which comprises a combination of the ground fabric and the lap fabric and is suitably used as a filter cloth for dust collectors or the like because it has excellent dimensional stability and mechanical strength and can maintain high filtration efficiency with pressure drop reduced for a prolonged period of time. CONSTITUTION: A twin-needle bed warp-knitting machine having at least 6 reeds is used to carry out the knitting, as one reed is arranged each in the front and the rear of the ground fabric and another reed each in the front and the rear of the lap fabric. Continuous textured yarns or spun yarns of synthetic fibers of 10 or more impulse (expressed by the formula: [strength at break in g/d ×elongation at break in %]<1/2> ) and 50-600 denier fineness are knitted as the ground fabric in a 1-3 needle rack, while continuous textured filament yarns or spun yarns made of a mixture of synthetic fibers having less than 5% shrinkage and fibers of less than 1.0 denier filament fineness at a weight ratio of (20-50)/(50-80) are knitted as the lap fabric in a 2-6 needle rack to give this warp-knitted fabric for filtration. The ground warp-knitted fabric and the lap warp-knitted fabric are overlapped and knitted utilizing 2 middle reeds in a 1-3 needle rack to form a cylinder whereby a seamless bag filter is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dust collecting device for environmental protection and powder recovery, and a filter cloth used for filtration.

[0002]

Boilers, steel-related furnaces, cast iron blast furnaces,
Usually used as a dust collector for the purpose of separating and collecting dust from soot smoke generated from a cement kiln, an aggregate drying oven, a non-ferrous metal industry oven, a refuse incinerator, etc., or recovering valuable powder such as fertilizers and chemicals. , Woven fabrics and felt-like filter cloths are used.
The properties of dust and gas vary depending on the type of source, structure, and operating conditions, and the quality and performance required for filter cloth cannot be summarized. Also, the required quality of the filter cloth varies depending on the amount of processing gas, the filtration rate, the shape of the filter cloth, and the type of the dust removing mechanism. Generally, in order to obtain high filtration efficiency, a mechanical vibration or an intermittent type sweep-off mechanism typified by a reverse air flow type is adopted, and a woven fabric with good dust releasability is often used as the filter cloth. .

As a material for the woven fabric, an appropriate material is selected from general fibers including natural fibers, but synthetic fibers having excellent physical properties are widely used. Examples thereof include polyolefin fibers, polyester fibers, polyamide fibers, polyacrylonitrile fibers, and glass fibers, aromatic polyamide fibers, and polyimide fibers when heat resistance is required. .

However, the woven filter cloth has the drawbacks that the filtration rate of gas is low and the seam shrinks into a banana shape, resulting in easy tearing from the seam. In the case of felt, breathability is very excellent, but it has drawbacks such as mechanical vibration and difficulty in applying a reverse airflow type scrubbing mechanism. In order to compensate for these drawbacks, a filter made of a woven fabric using a processed yarn and a filter of a seamless woven fabric have been devised, but it cannot be said that the filtration speed is sufficient and the pressure loss is high.
There are drawbacks such as high cost. A seamless knit filter has been devised to compensate for these drawbacks.
It has a drawback that it has a large longitudinal elongation and lacks dimensional stability.

[0005]

DISCLOSURE OF THE INVENTION The present invention has the above-mentioned conventional drawbacks in filter cloths such as bag filters used in dust collectors for environmental protection and powder recovery, that is, low filtration speed, With the aim of solving the problems such as low dimensional stability, and providing a material for filter cloth with excellent filtration speed, filtration efficiency, and dimensional stability, as a result of diligent studies, warp knitted fabric was found to be useful in solving this problem. Heading, proposed earlier patent. However, although the warp knitted fabric of the present proposal is excellent in characteristics such as dimensional stability and air permeability, it is slightly unsatisfactory in terms of filtration efficiency, and the object is to solve this and obtain a well-balanced filter cloth fabric. I am trying.

[0006]

The above-mentioned object of the present invention is knitted by using a two-needle bed warp knitting machine of 6 reeds,
Synthetic fiber yarns are arranged on each one of the front reed and the rear reed, and each of the yarns is knitted with 1 or more and 3 or less needles to form a ground structure, and each of the other front and rear ones Each reed is provided with a composite yarn of a high shrinkage yarn and an ultrafine fiber yarn, and each yarn is knitted by swinging from 2 to 6 stitches. The present invention provides a warp knitted fabric for filter cloth, which is knit-joined by swinging 2 to 3 needles to form a tubular shape.

The tensile strength of the warp knitted fabric of the present invention is preferably 30 kgf / 5 cm ² or more in the longitudinal direction and 30 kgf / 5 cm ² or more in the transverse direction. Tensile strength is 30kgf / 5cm ^{2 in the} vertical direction
If the width is less than 30 kgf / 5 cm ² in the lateral direction, the filter cloth is apt to be damaged or punctured, which shortens the life of the filter cloth. The upper limit of tensile strength is not particularly limited, but it is 4 in both length and width.
00 kgf / 5 cm ² or less is sufficient. Preferably, the longitudinal direction 40
~ 250kgf / 5cm ² , lateral direction 40 ~ 250kgf / 5cm
² The tensile strength referred to here is JIS L1096 6.
12 (1) A value measured by method A (cut strip method).

In order to obtain the warp knitted fabric for filter cloth of the present invention, it is necessary to use a two-needle bed warp knitting machine having 6 or more reeds as a knitting machine. The multi-filament yarn and / or the false twisted yarn are preferable as the synthetic fiber yarns arranged for the ground structure in the front reed and the rear reed one by one, and the total denier is a single yarn, a twin yarn, or a triple yarn It is sufficient that the total number of combined yarns is 50 to 600 denier. If it is less than 50 denier, it will be difficult to obtain the tensile strength required for the ground structure, and if it exceeds 600 denier, it will be difficult to set the basis weight and air permeability in the two-needle bed warp knitting machine. It is preferably 100 to 500 denier. Further, since the main purpose of this ground structure is mainly to impart longitudinal strength, a monofilament may be used.

Further, the impulse of the single fiber strength / elongation of the multifilament yarn and / or the false twist textured yarn used in the present invention (breaking strength (g / d) × (breaking elongation (%)) ^1/2 ) Is preferably 10 or more, and the breaking strength is basically 3.5 cm ² / d
As described above, the breaking elongation is preferably 100% or less.
That is, when the strength of the single fiber is less than 3.5 cm ² / d, even if the total fineness is 50 denier or more,
It becomes difficult to obtain the above-mentioned tensile strength. When the elongation at break exceeds 100%, when the filter cloth is used, especially when mechanical vibration is applied, the cloth easily stretches, and blowout tends to occur due to the openings, and dimensional stability during use. Cannot be guaranteed. The preferred breaking elongation is 70% or less. The yarn preferably has a small swing width for the purpose of reducing the longitudinal elongation of the fabric, and chain knitting is desirable. An insertion thread may be inserted for the purpose of further reducing the elongation.

The composite yarns arranged on the remaining one piece of the front reed and one piece of the rear reed, that is, the synthetic fiber threads used for the wrap structure, are
The main purpose is the function of filtration and the addition of strength in the lateral direction, and it is selected with this in mind. That is, the total denier of the thickness of the composite yarn is determined by the balance between the required strength and the swing width. The larger the swing width, the higher the fabric weight, and the higher the filtration efficiency and lateral strength. The range of swing width that can be used is 2 to 6 needles. One needle does not sufficiently close the opening, and if the swing width is 7 or more, smooth production cannot be performed. It is preferably within 3 to 5 needles. The swing width referred to here is the swing width when forming one course, and does not mean that it moves more than 7 stitches in multiple courses like an atlas pattern.

Here, it is preferable that the high shrinkage yarn and the ultrafine fibers constituting the composite yarn to be used are mixed by an interlace or the like in advance, but they may be aligned and used during knitting. The fineness of the composite yarn is 50 to 600 denier, preferably 100 to 500 denier. If it is less than 50 denier, the opening of the bundling part is not sufficiently blocked and blowout easily occurs, and if it is more than 600 denier, it can be blocked, but the number of implants cannot be increased, the tissue becomes rough, and the smoothness of the filtering surface is descend.

The high shrinkage yarn used in the composite yarn is made into a bulky fiber by shrinking it with a heat set of the knitted fabric to prevent the knitted fabric from being clogged with the heat set and to prevent air permeability. Used to secure filtration and improve filtration efficiency through three-dimensional filtration. For this reason, the above object cannot be achieved with a yarn having an SHD of 5% or less, and if it is too high, the smoothness of the surface is impaired and the performance as a filter material is impaired. The SHD is preferably 5 to 25%, more preferably 10 to 20%.

Further, the single fiber denier of the yarn used for the composite yarn is preferably as small as possible for the purpose of improving the filtration efficiency, and usually 5 denier or less. When it is 5 denier or more, the specific surface area is reduced, so that the trapping efficiency of fine particles is lowered, and problems such as blowout occur. Therefore, the single fiber denier is preferably designed according to the particle size of the target dust or powder or the like, and is preferably 3 denier or less, more preferably 1 denier or less.

Further, the shrinkage ratio used for the present composite yarn is 5%.
The composite ratio of the synthetic fiber yarn and the ultrafine fiber yarn having a single yarn denier of 1 denier or less is 50:50 to 20:80. If the ratio of the ultrafine fiber yarn is 50% or less, the desired filtration performance cannot be obtained, and if the ratio of the high shrinkage yarn is less than 20%,
The increased density and bulkiness of the knitted fabric described above are insufficient, and the air flow rate and filtration efficiency are reduced.

Further, the filtration efficiency can be increased by replacing a part or all of the composite yarn with spun yarn. of course,
Also in this case, it is preferable that the diameter of the single fiber is as small as possible within the range in which spinnability is allowed. The thickness of spun yarn is selected from 9 to 100 count. If it is thinner than 100th, it becomes difficult to design the strength and to fill the voids of the knitted fabric. If it is thicker than 9th, it is difficult to increase the knitting density of the knitted fabric, and the filtration surface becomes rough due to the decrease in the number of knitting yarns as described above. Preferably,
20th to 80th.

The fiber material used in the present invention is selected according to the desired level of desired temperature, chemical resistance and the like. For example, polypropylene, polyethylene terephthalate, polyacrylonitrile, etc., may be added up to 220 ° C at up to 130 ° C.
Polyetherimide, polyether sulfone,
Aramid, polyphenylene sulfide, etc.
Polyetheretherketone, polyetherketone, etc. are used at 0 ° C., and polytetrafluoroethylene, polybenzimide, glass, polyimide, etc. are used at ˜260 ° C.

The warp knitted fabric for filter bag of the present invention is
It has the following features, which are achieved by a double needle bed warp knitting machine. The features are: (1) Low elongation in the longitudinal direction. (2) Due to the application of a structure having a large swing width, for example, half, satin, quins coat, etc., the opening is unlikely to occur during lateral extension. (3) The knitting structure is firm, the stitch does not run (wire) unlike weft knitting, and the fraying like a woven fabric does not occur. (4) According to the purpose of use, the diameter of the cylinder knit can be easily changed with the same machine (for weft knitting and circular loom, it is necessary to change the machine).

The warp knitted fabric for filter cloth of the present invention is mainly knitted by a two-needle bed warp knitting machine. The model of the warp knitting machine is selected according to the desired knitted fabric, knitting density, etc., and the gauge number is the knitting density. Chosen from the point of. Usually, 18 to 36 gauge is selected, but a preferable gauge number is 22 to 28 gauge.

The warp knitted fabric for filter cloth of the present invention has a desired bag warp (φ
cm) and can be knitted seamlessly (cylindrical).
In order to make it seamless, it is preferable to knit in a tubular shape with multiple reeds. For example, as shown in FIG. No. 1 and 6 reeds for chain knitting Nos. 2 and 5 are for lap. The 3rd and 4th reeds are made of double denby, and a seamless knitted fabric is obtained by connecting the front and back knitted fabrics. If seamless is not required, the connection of the knitted fabrics on the front and back should be omitted.

The yarn for wrapping incorporated in the warp knitted fabric for filter cloth of the present invention is used for the purpose of suppressing longitudinal and lateral elongation and closing the gaps generated between the stitches.
Alternatively, spun yarn is preferred. The swing width of the yarn used for wrapping during one course knitting is within 2 to 7 needles, preferably within 2 to 6 needles. The larger the swing width, the more the lateral elongation becomes equal to that of the woven fabric, but smooth production cannot be achieved. Further, by inserting a yarn (especially monofilament) into the above knitting structure using 8 reeds with a swing width of 0 to 2 needles using 2 reeds, the longitudinal elongation of the knitted fabric is further reduced. I can do things.

The warp knitted fabric obtained with the above yarn structure and knitting structure has a large longitudinal elongation rate for use as a target filter cloth, for example, a bag filter, and in order to obtain the longitudinal elongation rate to be provided. , It is important to set heat in the vertical direction with tension or a fixed length. It is necessary to perform heat treatment at 160 ° C. or more while giving sufficient tension so that the longitudinal elongation rate after heat setting becomes 80% or less. It is preferable that the warp knitted fabric is treated at a temperature higher than the heat treatment temperature received during yarn production, and therefore, the tension heat treatment temperature of the warp knitted fabric is more preferably 180 ° C. or higher. At this time, a filter cloth having higher filtration efficiency can be obtained by causing a lateral contraction at the time of setting and making the fabric structure dense in order to close the gap generated between the stitches. The preferred tensile elongation at break of the warp knitted fabric for filter cloth is 80% or less in the longitudinal direction and 160% in the transverse direction.
It is the following. Another feature of the present invention is that the elongation in the vertical direction is low and that the blowout does not occur even when the elongation in the horizontal direction is caused.

[0022]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto. Using the yarns shown in Table 1 for making the warp knitted fabrics of Examples 1, 2 and 3, the knitting structure,
Knitted under the knitting conditions. In addition, these warp knitted fabrics were knitted by a 6-blade reed knitting machine with two needle beds equipped with 22 gauge.

[0023]

[Table 1]

FIG. 1 shows the knitting structure in the front reed N
o.L1 and L2 knitted the front surface of the tubular knit, and rear reeds No.5 and 6 knitted the rear surface. A tubular knit was formed by connecting the front and back knitted fabrics with the middle reed No. L3 and L4 threads.

Example 1 is 150d / 48 as No. L1 thread.
f Chain knitting is formed as a ground structure using processed yarn,
No.L2 threads 70d / 216f 2 processed threads and 75d / 36f
High shrink yarn (160 ° C dry heat shrinkage (SHD) is 5% or more)
Was pre-interlaced to form the front surface of the tubular knit. The mixing ratio of both was 65:35.
The swing width of the knitted yarn in one course knitting was 4 needles as shown in FIG. Similarly, the rear surface of the tubular knit is 150 for reed No. L6.
The d / 48f textured yarn is knitted by arranging the above composite yarn in No.L5, and 150d / 48f and 70d / 216 arranged in the No.L3 and L4 reeds.
Using an f × 2 interlaced composite yarn, a double Denby (double tricot) knitting was used to connect the front and back to form a tubular shape. Example 2 was knitted in the same manner with the same yarn usage but different swing widths, and in Example 3, knitting was performed using spun yarn for wrapping. The obtained raw machine was fixed at 200 ° C. for 30 seconds. The properties of the knit obtained by long-setting are shown in Table 2.

[0026]

[Table 2]

In Comparative Example 1, the same knitting structure as in Example 1 was used but the yarn usage was changed. In Comparative Examples 2 and 3, a seamless knit weft knitted fabric and a seamless woven fabric were fried for comparison, respectively.

As is clear from Table 2, in Examples 1, 2 and 3 according to the present invention, the elongation and the strength peculiar to the knit are higher than those of the weft knitted fabric of Comparative Example 2. Is significantly improved, and the burst strength is also improved by balancing the longitudinal and lateral strength and elongation. Furthermore, Comparative Example 3
Compared with the woven fabric of No. 3, the tear strength was also excellent, and the problem of high pressure loss during filtration due to the low air permeability of the woven fabric was solved by the significant improvement of the air permeability. Comparative Example 1 is an example of the case where the scope of claims of the present invention is not satisfied. In addition, the filtration characteristics should be evaluated by the amount of dust leaked (○: 10 mg / m ³ · min
>, Δ: 20 mg>, ×: 21 mg or more), it can be seen that Examples 1, 2 and 3 according to the present invention have excellent performance.

FIG. 2 is a diagram showing the knitting structure of Example 4, in which a 22-needle bed warp knitting machine equipped with a 22 gauge to further suppress the longitudinal elongation, and the following yarns and knitting structures by an 8-blade , Knitted under the knitting conditions. Reed is No.
L1 and L8 are 150d / 48f as insertion yarns respectively, L2 and L7 are 75d / 36f for forming ground texture, and L3 and L6 are 150d for wrapping as in the first embodiment.
/ 48f textured yarn and 70d / 216f × 2 composite yarn are arranged, and as L4 and L5, the same 150d / 48f and 70d / 216f × 2 composite yarns are used as yarns for connecting the front and rear knitted fabrics. I arranged it. The knitting structure was the same as in Example 1 except that L1 and L8 were inserted. The knitting conditions are L1 and L8.
The runner of 253, the runners of L2 and L7 are 119
The runners of 5, L3 and L6 were set to 2505, and the runners of L4 and L5 were set to 1467.

The basis weight of the knitted fabric is 340 (g / m ² ), the number of courses is 51 (pieces / in), the number of wales is 24 (pieces / in), and the thickness is 0.
6 (mm), tubular knitting diameter 204 (mm), tensile strength is
Vertical 92.6 (kgf / 5cm), Width 216 (kgf / 5cm),
Tensile elongation is vertical 38%, horizontal 97%, tear strength (kgf) is vertical 31, horizontal 95, burst strength (kgf / cm ² ) is 281, breathability (cm ³ /cm.s) is 15.0. Met. The longitudinal elongation was improved to the level of a woven fabric and the filtration characteristics were excellent without significantly changing the strength characteristics and the like.

As described above, the warp knitted fabric for bag filters according to the present invention covers the shortcomings of the knit weft knitted fabric having high elongation and low strength, and the low breathability of the woven fabric. It had excellent characteristics sufficient for

[0032]

INDUSTRIAL APPLICABILITY The warp knitted fabric obtained according to the present invention has a combination of a chain knitted ground structure mainly contributing to the strength of the knitted fabric and a wrap structure mainly contributing to filtration efficiency, and thus has a powder collecting property and a dust collecting property. The knitting structure can be freely configured according to the purpose. Furthermore, the seamless bag filter according to the present invention is
It has excellent dimensional stability and excellent breathability without pulling by sewing, and has the effect of maintaining high filtration efficiency with low pressure loss for a long period of time.

[Brief description of drawings]

FIG. 1 is a knitting structure diagram showing an example of a double Russell warp knitted fabric of the present invention.

FIG. 2 is a knitting structure diagram showing an embodiment of the double Russell warp knitted fabric of the present invention.

Claims (6)

[Claims] 1. A knitting machine using a two-needle bed warp knitting machine having at least 6 reeds, wherein one reed is used for the ground structure and one wrap is used for the other reeds. A warp knitted fabric for filter cloth characterized by being knitted. 2. The synthetic fiber yarn used for the ground structure has an impulse (breaking strength (g / d) × (breaking elongation (%)) ^1/2 ) of 10 or more and a total denier of 50 denier. 2. The warp knitted fabric for filter cloth according to claim 1, wherein the warp knitted fabric has a denier to 600 denier. 3. A composite yarn of synthetic fiber yarn having a shrinkage of 5% or more and fiber yarn having a single yarn denier of 1.0 denier or less (mixed 20 to 50). : 50 ~
The warp knitted fabric for filter cloth according to claim 1, wherein the warp knitted fabric is 80% by weight. 4. The warp knitted fabric for filter cloth according to claim 1, wherein the synthetic fiber yarn used for the ground structure and / or the wrap structure is a spun yarn. 5. The yarn used for the ground structure is knitted with a swing of 1 needle or more and 3 needles or less, and the yarn used for the wrap tissue is knitted with a swing of 2 needles or more and 6 needles or less. The warp knitted fabric for filter cloth according to claim 1, which is characterized in that. 6. The filter cloth according to claim 1, wherein the front and rear warp knitted fabrics having a ground structure and a wrap structure are knitted with 1 to 3 needles in two middle reeds to form a tubular shape. Warp knitted fabric.