JPH07136431A - Coarse and dense structural filter medium and production thereof - Google Patents

Abstract

PURPOSE:To obtain a coarse and dense structural filter medium ensuring gaps necessary for ventilation and causing no thermal deterioration of fibers. CONSTITUTION:A coarse and dense structural filter medium is composed of a fiber layer 11 containing thermoplastic fibers having crimps and thermoplastic fibers collapsed in crimps and the single surface of the fiber layer 11 is composed of a dense layer part 15 containing thermoplastic fibers collapsed in crimps and the other surface thereof is constituted by a coarse layer part 14 containing thermoplastic fibers having crimps.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coarse-dense structure filter medium and a method for producing the same. More specifically, the present invention relates to a coarse / fine structure filter medium in which voids necessary for ventilation are secured and fibers are not deteriorated by heat, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
As the coarse-dense structure filter medium, as shown in FIG. 4, fiber layers having different fiber diameters or fiber layers produced by different manufacturing methods are used, one of which is a coarse layer 2 and the other is a dense layer 3, which are laminated and integrated. is there.

However, this filter medium is manufactured through a process in which a fiber layer to be a rough layer or a dense layer is separately produced, and then the respective layers are laminated and integrated, so that the number of steps is increased. In many cases, it is complicated, and delamination may occur depending on the method of integration.

To solve this, the present inventor heat-pressurizes one side of the fiber layer 4 at a temperature near the melting point of the constituent fibers as shown in FIG. A filter medium in which the constituent fibers are bonded to each other to densify one side of the fiber layer 4 was examined. This filter medium can be manufactured by a simple operation of heating and pressing one fiber layer at a predetermined temperature, and this filter medium has one continuous surface of one fiber layer as a rough layer portion. Since the other surface is formed as a dense layer portion, there is no possibility of causing a problem such as delamination.

However, in this filter medium, as shown in FIG. 5, a film is formed in the bonded portion 5 due to the fiber bonding, so that the voids are blocked and the airflow resistance of the filter medium increases. Was there. Further, since this filter material causes fiber adhesion by high heat treatment, there is a problem that the fiber is deteriorated by heat.

The present invention has been made in view of the above problems, and an object thereof is to provide a coarse-dense structure filter medium in which voids necessary for ventilation are secured and fibers are not deteriorated by heat, and a method for producing the same. It is what

[0007]

In order to achieve the above object, in the invention according to claim 1, a fiber layer containing a thermoplastic fiber having a crimp and a thermoplastic fiber having a crimp collapsed is formed. And a coarse-dense structure filter medium characterized in that one side of the fiber layer is a dense layer portion containing a thermoplastic fiber in which a crimp is collapsed, and the other surface is a coarse layer portion containing a thermoplastic fiber having a crimp. I made it the summary.

According to the second aspect of the invention, one side of the fiber layer containing the crimped thermoplastic fiber is higher than the temperature for heat setting the crimp of the crimped thermoplastic fiber and the temperature for fiber bonding. By heating and pressurizing at a lower temperature than that, the crimp of the thermoplastic fiber having the crimp contained on one side of the fiber layer is broken, and the thickness of one side of the fiber layer is thinned and densified. The manufacturing method of the coarse-dense structure filter medium is defined as the gist.

In the invention of claim 3, the crimp of the thermoplastic fiber having crimp has a heat setting temperature of 90.
The gist is a method for producing a filter material having a coarse and fine structure, which is characterized in that the temperature is 140 ° C.

The coarse and dense structure filter medium and the method for producing the same according to the present invention will be described in more detail below. First, the coarse / fine structure filter medium of the present invention will be described. As shown in FIG. 1, the coarse-dense structure filter medium of the present invention includes a fiber layer 11 containing thermoplastic fibers 12 having crimps and thermoplastic fibers 13 having crimps collapsed.
Consists of. The crimp-containing thermoplastic fiber refers to a crimped fiber in which a mechanically formed crimp (crimp) is fixed by heat setting. The crimping process includes, for example, a stuffing box method and a heating gear method, and crimps having a zigzag shape or a coil shape are applied to the fibers by heat setting. In the present invention, the heat setting temperature for crimping is preferably lower than the normal processing temperature. This is because by lowering the heat setting temperature, it is possible to lower the heating temperature in the process of breaking the crimp and forming the dense layer, and by lowering this heating temperature, adhesion of fibers or film formation, or heat There is no need to worry about deterioration. Therefore, the heat setting temperature for applying the crimp varies depending on the type of fiber, but is preferably 90 to 140 ° C.

Further, the crimp-collapsed thermoplastic fiber means that the thermoplastic fiber having the crimp is heated and pressed at a temperature higher than the temperature at the time of heat setting for crimping, and lower than the temperature at which the fiber is bonded. It is a fiber that is fixed in a planarly compressed state due to collapse of the three-dimensional crimp structure of the fiber because the strain of the fiber molecule is released and rearranged. The fiber layer is not substantially affected by the heating temperature for breaking the crimp in order to impart strength to the fiber layer, in addition to the thermoplastic fiber having the crimp and the thermoplastic fiber having the crimp collapsed. The fibers may be fibers or fibers that bond the fibers together, but may be composed only of crimp-containing thermoplastic fibers and crimp-collapsed thermoplastic fibers.

As shown in FIG. 1, one side of the fiber layer 11 contains the thermoplastic fiber 12 having the crimp as it is, and a rough layer portion in which a constant gap is secured between the fibers by the crimp. It is 14. On the other hand, the other surface has a thickness higher than the temperature at the time of heat setting for crimping the fiber and is heated and pressed at a temperature lower than the temperature for fiber bonding to collapse the crimp of the thermoplastic fiber having the crimp. The dense layer portion 15 is thin and has a dense fiber structure with a small fiber gap. In addition, since the thermoplastic fibers with the crimp collapsed are not heat-sealed together, even if they are densified, the fiber gap does not block the fiber gap, so a sudden pressure loss (air flow resistance) Is not invited.

The content of the crimp-containing thermoplastic fiber and the crimp-collapsed thermoplastic fiber in the fiber layer is preferably 50% or more, more preferably 100%. This is because when the content of the crimped thermoplastic fiber and the crimp-collapsed thermoplastic fiber is 50% or less, the coarse layer portion containing the crimped thermoplastic fiber and the crimp-collapsed thermoplastic fiber are included. This is because it becomes difficult to reveal a clear dense and dense structure with the layer portion.

The ratio of the coarse layer portion and the dense layer portion in the filter medium of the present invention and the difference in the porosity between the coarse layer portion and the dense layer portion of the filter medium are not particularly limited, and conventional fibers produced separately. As in the case of the filter material of the type in which layers are laminated and integrated, it may be appropriately determined in consideration of the use, size, usage condition and the like of the filter material. If necessary, the coarse-dense structure filter medium of the present invention may be used in combination with another filter medium.

Next, the method for producing the coarse and dense filter medium of the present invention will be described. The method for manufacturing the coarse-dense structure filter medium of the present invention comprises:
One side of the fiber layer is heated and pressed at a temperature higher than the temperature for heat-setting the crimp of the thermoplastic fiber having a crimp and lower than the temperature at which the fiber is adhered to one side of the fiber layer containing the thermoplastic fiber having the crimp. The crimp of the thermoplastic fiber having the crimp contained in is broken, and the thickness of one side of the fiber layer is reduced to densify.

As shown in FIG. 2, the fiber layer 11 contains the crimped thermoplastic fibers 12. The crimp-containing thermoplastic fiber is a fiber having a bulky structure in which voids are formed between the fibers by crimping the fibers, and the fibers are contained in the fiber layer, and air is present between the fibers in the fiber layer. A constant void is formed to pass through.

One side of this fiber layer is heated and pressed at a temperature higher than the temperature for heat setting the crimp of the thermoplastic fiber having the crimp and lower than the temperature for fiber bonding. In the crimp-containing thermoplastic fiber used in the present invention, the heat-setting temperature of the crimp is lower than the heat-setting temperature of 150 to 200 ° C. which is usually performed in the crimping process.
It is desirable that the temperature is 140 ° C. This is because at a normal heat setting temperature, the temperature is relatively close to the softening point, so that the fibers may be fused and may be thermally deteriorated. If fibers having a heat setting temperature of 90 to 140 ° C., more preferably 90 to 120 ° C. are used, the heating temperature in this step can be lowered, so that there is no such concern. As the heating method, in addition to the above method, one of the facing rolls is a heating roll which is heated at a temperature higher than the temperature for heat setting the fibers and lower than the temperature for fiber bonding, and the other roll is added. As a pressure roll, there is also a method of passing the fiber layer between these rolls.

The crimped thermoplastic fibers contained on one side of the heated fiber layer are rearranged by releasing the strain of the fiber molecules under the influence of the heat. In this case, the crimped thermoplastic fiber in the fiber layer is heated at a temperature higher than the temperature for heat setting but lower than the temperature for fiber bonding, and thus is damaged by heat and deteriorates. Nor does it cause thermal bonding.

The thermoplastic fiber having a crimp on one side of the fiber layer loses its shape-retaining property due to heating, and the fiber on the other side which is not affected by heat remains the shape-retaining property of the crimp. ing. By pressing the fiber layer in this state, the fiber layer is compressed according to the pressure and fixed to a constant thickness. At this time, since the crimp of the thermoplastic fiber having the crimp is broken on the other surface side of the fiber layer, the thickness is reduced accordingly, the fiber gap is reduced, and the fiber is densified and fixed. Thus, as shown in FIG. 1, one side of the fiber layer 11 is formed into the rough layer portion 14 containing the crimped thermoplastic fibers 12, and the other surface is formed into the dense layer portion 15 containing the crimp-collapsed thermoplastic fibers 13. It is possible to obtain a coarse and dense structure filter medium.

[0020]

【Example】

Example 1 Fineness of heat-set 12 pieces / inch of coiled crimp at a heat setting temperature of 100 ° C. 60% of polyester fiber having a fineness of 3 denier and 12 pieces / inch of a coiled crimp at a heat setting temperature of 170 ° C. A fiber web having a basis weight of 125 g / m ² mixed with 40% of 3 denier polyester fiber was needle punched. Then, the above-mentioned fibrous web was passed between the rolls heated to 130 ° C. at a speed of 6 m / min to densify the side of the fibrous web in contact with the heating roll, and then the acrylic resin emulsion 65 g / m ² Was impregnated in a foamed state and dried to obtain a coarse and dense filter medium having a basis weight of 190 g / m ² and a thickness of 2.5 mm.

The obtained filter medium was mounted in a duct, and the JIS
When 8 kinds of test dusts were used and passed through at a wind speed of 40 cm / sec, the pressure loss was 5 mmH ₂ O and the collection efficiency was 9
It was 8.2%.

Comparative Example 1 Example 1 was repeated except that the fiber web was made of 100% polyester fiber having a fineness of 3 denier, which was heat set with 12 pieces / inch of coil crimps at a heat setting temperature of 170 ° C. A filter medium was manufactured in the same manner. In this filter medium, the densification of the fibrous web hardly occurred on the side in contact with the heating roll at 130 ° C., and the thickness was 2.8 mm.
Met.

When a test was conducted in the same manner as in Example 1, the pressure loss was as low as 4.5 mmH ₂ O, which was excellent, but the collection efficiency was 89.0%, and dust could not be collected sufficiently. .

Comparative Example 2 40 g of a basis weight made of rayon fiber having a fineness of 1.5 denier
50 g with a fiber layer of / m ² and rayon fiber with a fineness of 1.5 denier 60%, polyester fiber with a fineness of 3 denier 25% and rayon fiber with a fineness of 7 denier 15%
/ M ² fiber layer and a fiber layer having a basis weight of 50 g / m ² consisting of 40% polyester fiber having a fineness of 3 denier and 60% rayon fiber having a fineness of 7 denier, and needle-punched, and then an acrylic resin Emulsion 90g / m
² was impregnated in a frothed state. Due to the impregnation, the layer having a higher proportion of rayon fibers is more densified and is dried in this state to obtain a coarse-structure filter medium having a basis weight of 230 g / m ² and a thickness of 3.0 mm.

When a test was conducted in the same manner as in Example 1, the collection efficiency was 98.1%, which was almost the same as that of the filter medium of Example 1 and excellent, but the pressure loss was as high as 9.0 mmH ₂ O. .

Example 2 Acrylic resin emulsions were formed on both sides of a fiber web having a basis weight of 160 g / m ² and made of 100% polyester fiber having a fineness of 15 denier, which was heat-set with a coil crimp of 9 pieces / inch at a heat setting temperature of 110 ° C. after spraying the 30 g / m ^2, an acrylic resin emulsion 100 g /
m ² was impregnated in a foamed state and dried. Then, the above-mentioned fibrous web was passed between the rolls heated to 140 ° C. at a speed of 4 m / min to densify the side of the fibrous web which was in contact with the heating roll, and had a basis weight of 320 g / m ² and a thickness of 13 mm. A coarse-dense structure filter medium was obtained.

The obtained filter medium was tested by a method according to JIS B-9908 type 3 under the condition of a wind speed of 2.5 m / sec. The pressure loss was 5.5 mmH ₂ O and the average collection efficiency was 7
It was 0%.

Comparative Example 3 As in Example 2 except that the fiber web was made of 100% polyester fiber having a fineness of 15 denier, which was heat set with a coil crimp of 9 pieces / inch at a heat setting temperature of 170 ° C. A filter medium was manufactured in the same manner. In this filter medium, the densification of the fibrous web hardly occurred on the side in contact with the heating roll at 140 ° C., and the thickness was 17 mm.

When a test was conducted in the same manner as in Example 2, the pressure loss was as low as 4.5 mmH ₂ O, which was good, but the average collection efficiency was 65%, and dust could not be collected sufficiently.

[0030]

According to the present invention, the above-mentioned structure is provided.
In the described coarse-dense structure filter medium, since the fiber gap is not blocked and the space between the fibers through which air passes is secured, there is no adverse effect such as an increase in ventilation resistance. Further, in this coarse-dense structure filter medium, there is no problem of deterioration of the fiber due to heat because the fiber is not bonded by the high heat treatment. Moreover, in this coarse-dense structure filter medium,
Since one continuous fiber layer has a rough layer portion containing thermoplastic fibers having crimps and the other surface has a dense layer portion containing thermoplastic fibers with crimps collapsed, a conventional laminated type filter medium is provided. There is no need to go through the complicated process of separately preparing a fiber layer to be a rough layer or a dense layer, and laminating and integrating each layer, and also delamination does not occur.

In the method for manufacturing the coarse-dense structure filter medium according to the second aspect, one side of the fiber layer containing the crimped thermoplastic fibers is higher than the temperature for heat setting the crimped thermoplastic fibers, and the fiber bonding is performed. By heating and pressing at a temperature lower than the temperature, the crimp of the thermoplastic fiber having the crimp contained on one side of the fiber layer is broken, and the thickness of one side of the fiber layer is thinned and densified to form a coarse and dense structure in the fiber layer. Since it is exposed, the fiber gap is not blocked, and a gap through which air passes between the fibers can be secured. Further, in this coarse-dense structure filter medium, since the fibers are not bonded by the high heat treatment, there is no problem of deterioration of the fibers due to heat.

In the method for producing a coarse-dense structure filter medium according to the third aspect, the crimp of the thermoplastic fiber having crimp contained on one side of the fiber layer is heat-pressed at a relatively low concentration to bond the fibers. It can be securely broken without causing.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view schematically showing a coarse / fine structure filter medium of the present invention.

FIG. 2 is an enlarged cross-sectional view schematically showing a fiber layer.

FIG. 3 is an enlarged cross-sectional view schematically showing a state in which a fiber layer is heated and pressed from one side.

FIG. 4 is an enlarged cross-sectional view schematically showing a conventional coarse-dense structure filter medium.

FIG. 5 is an enlarged cross-sectional view schematically showing a conventional coarse-dense structure filter medium.

[Explanation of Codes] 11 ... Fiber layer 12 ... Thermoplastic fiber having crimp 13 ... Thermoplastic fiber with crimp collapsed 14 ... Rough layer portion 15 ... Dense layer portion

Claims (3)

[Claims] 1. A fiber layer containing a crimp-containing thermoplastic fiber and a crimp-collapsed thermoplastic fiber,
A filter element having a coarse and dense structure, wherein one side of the fiber layer is a dense layer portion containing a thermoplastic fiber having a crimp collapsed, and the other surface is a coarse layer portion containing a thermoplastic fiber having a crimp. 2. One side of the fiber layer containing the crimped thermoplastic fiber is heated and pressed at a temperature higher than the temperature for heat setting the crimp of the crimped thermoplastic fiber and lower than the temperature for fiber bonding. According to the method, the crimp of the thermoplastic fiber having a crimp contained on one side of the fiber layer is broken, and the thickness of one side of the fiber layer is reduced to densify the coarse-dense structure filter medium. 3. The method for producing a coarse-dense structure filter medium according to claim 2, wherein the crimp of the crimped thermoplastic fiber has a heat setting temperature of 90 to 140 ° C.