JPH06257040A - Warp knitted fabric for filter bag - Google Patents

Abstract

PURPOSE:To provide filter fabric for bag filters to be used in dust collectors for environmental protection or powder recovery, excellent in filtration rate, filtration efficiency and dimensional stability. CONSTITUTION:The warp knitted fabric for filter bags can be obtained, using a double raschel knitting machine, by combining the insertion texture of textured filament yarns and/or spun yarns with the chain texture of such filament yarns and/or spun yarns. This fabric has the following physical properties: (1) longitudinal elongation at break: <=60%; (2) lateral elongation at break: <=80%; and (3) air permeability: 5-50cm<3>/cm<2>.sec. By combining the chain-knitted ground texture contributing to the mechanical strength of the final knit fabric and the insertion texture contributing to the filtration efficiency thereof, knit texture can be freely constructed for the purpose of powder recovery or dust collection. Besides, seamless knitted bag filters made from the above warp knitted fabrics, which have excellent dimensional stability and air permeability without developing locally strained yarns therein due to its sewing, can maintain high filtration efficiency with low pressure loss for a long period of time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter bag used in a dust collector for environmental protection and powder recovery.

[0002]

2. Description of the Related Art Separation and collection of dust from soot and smoke generated from boilers, steel-related furnaces, cast iron blast furnaces, cement kilns, aggregate drying furnaces, non-ferrous metal industry furnaces, refuse incinerators, etc.,
Alternatively, a woven fabric or a felt-like filter cloth is usually used in a dust collector for the purpose of collecting valuable powder such as fertilizers and chemicals. The properties of dust and gas vary depending on the type of source, structure, and operating conditions, and the quality and performance required for filtering cannot be summarized. Also, the required quality for the filter cloth differs depending on the amount of processing gas, the filtration speed, the shape of the filter cloth, and the type of the dust removal mechanism. Generally, in order to obtain a high dust collection rate, mechanical vibration or an intermittent air-blow-off mechanism typified by a reverse air flow type is used, and a woven fabric with good dust releasability may be used for the filter cloth. Many.

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 when further heat resistance is required, glass fibers, aromatic polyamide fibers, polyimide fibers and the like. .

However, the filter cloth of the woven fabric has drawbacks that the filtration speed of gas is low and the seam shrinks to form 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 the filter cloth for bag filters used in a dust collector for environmental protection and powder recovery, that is, the filtration speed is low. Solving problems such as low dimensional stability, filtration speed,
The purpose is to provide a material for a bag filter, which has excellent filtration efficiency and dimensional stability.

[0006]

That is, according to the present invention, the filter-bug warp knitted fabric is composed of a double Russell warp knitted fabric, and has an insertion structure of a filament processed yarn and / or a spun yarn,
A warp knitted fabric for a filter-bag, which has a longitudinal elongation at break of 60% or less, a lateral elongation of 80% or less, and an air permeability of 5 to 50 cm ³ / cm ² · sec.

The warp knitted fabric of the present invention must have a tensile strength of 30 kgf / 3 cm or more in the longitudinal direction and 30 kgf / 3 cm or more in the transverse direction. If the tensile strength is less than 30 kgf / 3 cm in the longitudinal direction and 30 kgf / 3 cm in the lateral direction, damage and perforation of the filter cloth are likely to occur, and the life of the filter cloth is shortened. The upper limit of the tensile strength is not particularly limited, but 400 kgf / 3 cm or less in both length and width may be used. It is preferably 50 to 250 kgf / 3 cm in the vertical direction and 50 to 200 kgf / 3 cm in the horizontal direction. The tensile strength referred to here is a value measured by the JIS L1096 6.12 (1) A method (strip method).

Further, the elongation needs to be 60% or less in the longitudinal direction, and if it is higher than this, dimensional stability in the longitudinal direction tends to be impossible to be guaranteed. The lower limit must be 5%, and if it is lower than this, processing such as sewing becomes difficult. More preferably, 5
~ 50%. Also, in order to prevent blow-out in the lateral direction, 80% or less is necessary, and more preferably 60%.
It is the following. To obtain such elongation, it is achieved, for example, by using a textured filament yarn and / or a spun yarn as an insertion structure.

Further, the fineness of the multifilament yarn or the processed yarn used in the present invention is as follows.
The total number of composite yarns such as a child may be 100 to 500 denier. If it is less than 100 denier, it becomes difficult to obtain the above-mentioned required tensile strength, and if it exceeds 500 denier, it becomes difficult to set the basis weight and the air permeability in the double needle bed warp knitting machine. It is preferably 150 to 400 denier.

Further, it is desirable that the single fiber strength and elongation of the multifilament processed yarn used in the present invention is basically such that the breaking strength is 3.5 g / denier or more and the breaking elongation is 40% or less. That is, when the strength of the single fiber is less than 3.5 g / denier, it becomes difficult to obtain the above-mentioned tensile strength even if the total fineness is 100 denier or more. Further, when the breaking elongation exceeds 40%, when the filter bag is used, especially when the dust is wiped off, the fabric is easily stretched, and the blowout tends to occur due to the opening.
The dimensional stability cannot be guaranteed when using a filter bug. It is preferably 30% or less.

Further, the single fiber denier may be 0.1 to 10 denier, and may be the same denier or different denier mixed fibers. If it is less than 0.1 denier, it is difficult to manufacture and the cost is high. On the other hand, if it is 10 denier or more, problems such as an increase in the loop diameter of the knitted fabric, a decrease in the specific surface area and a decrease in the efficiency of trapping fine particles, and a problem of blowout during backwashing occur. The single fiber denier is preferably selected according to the size of the target dust, and preferably 0.2 to 8 denier.

The term "permeability" as used in the present invention refers to an initial value, which is the JIS Z8908 5.5 method (Frazier type method).
It is a measured value in water of 12.7 mm, and is an important value for obtaining the intended effect of the present invention. That is, the air permeability may be from 5 to 50 cm ³ / cm ² · sec, and if it is less than 5 cm ³ / cm ² · sec, clogging occurs in a short period after use, and the effect of the present invention is obtained. Disappear. On the contrary, 50
If it exceeds cm ³ / cm ² · sec, it will be in a blowout state and the target dust or valuable powder will not be collected effectively. It is preferably 10 to 40 cm ³ / cm ² · sec. The air permeability is selected according to the size of the dust particles of interest.

Further, the warp knitted fabric for filter bag of the present invention is preferably knitted with spun yarn for the purpose of improving the filtration efficiency. The spun yarn thickness is selected from 10 to 100 count. 1
If it is thinner than the 00 count, it becomes difficult to design the strength and fill the voids of the knitted fabric. If it is thicker than 10th, it is difficult to increase the knitting density of the knitted fabric. It is preferably 20-80. The characteristics of the single fiber used for the spun yarn are not particularly limited. It is selected according to the properties required for the filter bag, that is, air permeability and dust size.

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.
Polyether imide, 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). It has a low elongation in the warp direction, which is the main characteristic of a filter bag, and can be made as low as a woven fabric by applying an insert structure. (2). The knitting structure is firm, the stitches do not run like weft knitting, and do not fray like fabrics. (3). The diameter of the cylinder knitting can be easily changed on the same machine depending on the purpose of use (machines need to be changed for weft knitting and circular loom).
Etc.

The warp knitted fabric for filter bag of the present invention is 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. Selected from the points. Usually, 18 to 36 gauge is selected, but a preferable gauge number is 22 to 28 gauge.

The warp knitted fabric for the filter bag according to the present invention is knitted seamlessly (cylindrical) according to the desired bag warp (φ mm). In order to make it seamless, it is preferable to knit in a cylindrical shape with multiple reeds, as shown in FIG. 1 as an example.
No. No. 2 and 5 reeds for chain knitting Seamless knitted fabric can be obtained by connecting the front and back knitted fabrics with No. 3, 6 reeds for insert yarn and No. 3, 4 reeds with double denby.

The insert yarn incorporated into the warp knitted fabric of the present invention is for suppressing longitudinal and transverse elongation, and is a processed yarn and / or
Alternatively, spun yarn is inserted. The swing width of the inserted yarn during one course knitting is within 2 to 10 needles, preferably within 2 to 5 needles. When it is swung with 11 or more needles, the lateral elongation is the same as that of a woven fabric, but smooth production cannot be achieved. Further, as shown in FIG. 2, when using an 8-ply reed, the longitudinal elongation of the knitted fabric is further lowered by inserting a thread into the knitting structure with 2 reeds with a swing width of 0 to 2 needles. I can do things.

The warp knitted fabric obtained with the above yarn structure and knitting structure still has a large longitudinal elongation rate, and in order to obtain the longitudinal elongation rate that should be provided as a bag filter, heat setting is performed with tension in the longitudinal direction. Is important. 16 while applying sufficient tension so that the vertical elongation after heat setting is 60% or less
It is necessary to perform heat treatment at 0 ° C or higher. 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. The preferred stretch ratio of the warp knitted fabric is 50% or less in the longitudinal direction and 70% or less in the transverse direction.

[0020]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto. In order to make the warp knitted fabrics of Examples 1 and 2, knitting was performed using the yarn, knitting structure and knitting conditions shown in Table 1. In addition, these warp knitted fabrics were knitted by a 6-needle warp knitting machine with 2 needle beds equipped with 28 gauge.

FIG. 1 is a diagram showing a knitting structure. The front side of the tubular knitting is knitted with L1 and L2.
The rear surface was knitted with L5 and L6. Middle reed No. A tubular knit was formed by connecting the front and back knitted fabrics with the L3 and L4 yarns.

The first embodiment is No. 150d / for L2 thread
No. 48f textured yarn is used to form a chain stitch as a ground structure. The yarn of L1 maintained 70s / 2 mainly for strength in the transverse direction, and was arranged as an inserted yarn to improve the air flow rate and the filtration efficiency to form the front surface of the tubular knit. The swing width of the inserted yarn during one course knitting was 5 needles as shown in the figure. Similarly, the back surface of the tubular knitting is reed No. L5 150d /
The 48f textured yarn was The 70s / 2 spun yarn is arranged on L6 and knitted, and the medium reed No. Using 34s / 2 spun yarns arranged in L3 and L4, double denby (double tricot) knitting was used to connect the front and back to form a tubular knit. In Example 2 as well, knitting was performed in the same manner while changing the yarn usage, and the characteristics of the resulting greige were as shown in Table 2.

Comparative Example 1 has the same yarn structure as that of Example 1, but the fineness of the processed yarn is reduced. In Comparative Examples 2 and 3,
A seamless knit weft knitted fabric and a seamless woven fabric were fried for comparison, respectively.

As can be seen from Table 2, Examples 1 and 2 according to the present invention are both compared with the weft knitted fabric of Comparative Example 2.
The problems of high elongation and low strength peculiar to knitwear have been greatly improved, and the burst strength is also improved by balancing the strength and elongation in the length and width directions. Further, as compared with the woven fabric of Comparative Example 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 a significant improvement in air permeability. Comparative Example 1 is an example of the case where the scope of claims of the present invention is not satisfied.

[0025]

[Table 1]

[0026]

[Table 2]

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 shortcomings of low breathability of the woven cloth. It had excellent characteristics sufficient for

[0028]

INDUSTRIAL APPLICABILITY The warp knitted fabric obtained according to the present invention has a purpose of powder collection and dust collection by combining a chain knitted ground structure mainly contributing to the strength of the knitted fabric and an insertion structure mainly contributing to filtration efficiency. The knitting structure can be freely configured by
Furthermore, the seamless bag filter according to the present invention has excellent dimensional stability and excellent air permeability without pulling fishing due to 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 organization chart showing a reference example.

Claims (1)

[Claims] 1. A warp knitted fabric for a filter bag is made of a double Russell warp knitted fabric, and has a longitudinal elongation at break of 60% or less due to an insertion structure of a filament processed yarn and / or a spun yarn.
Lateral elongation is 80% or less, and air permeability is 5 to 50 cm ³ / cm
^A warp knitted fabric for filter bugs characterized by a length of ² sec.