JPH07729A - Independent filter medium - Google Patents

Abstract

PURPOSE:To obtain a filter medium having heat resistance, hardly clogging, long in service life and having air permeability by keeping an independent stereoscopic structure obtained by fusing a heat resistant molded body made of a polyimide fiber having a repeating unit expressed by a formula with a thermoplastic polyimide. CONSTITUTION:An air permeable molding (A) 2 and an air permeable molding (B) 3 are formed by inserting a polyimide fiber made felt between two of the upper and lower metallic die, heating and pressurizing. Successively the filter medium 1 having the independent stereoscopic structure is formed by superposing two pieces of air permeable molding 2 and 3, inserting the thermoplastic polyimide, having a repeating unit expressed by formula 1 and, for instance, worked into a tape shape, into parts showed by (a), (b) and (c), heating the parts of (a), (b) and (c) and pressurizing by pressing a heat plate to fuse. Then, the complicated shaped and large sized heat resistant filter medium having the independent stereoscopic structure and used over a long time even at the temp. of 260 deg.C is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molded body made of polyimide fiber having heat resistance, less clogging, long life, and breathability, which is formed by a bonding process so that it has a complex and large-scale rigidity that enables self-supporting. To produce a filter agent having

[0002]

2. Description of the Related Art Polyimide is a material polymer having excellent properties such as excellent thermal stability and flame retardancy. However, this polyimide is difficult to melt without decomposition, and also has the property of being dissolved only in a polar solvent having a high boiling point, for example, when forming a film, a usual melt film forming method or a solution film forming method is used. It is difficult to use. Attempts have been made to mold compacts using polyimide powder materials, but it is difficult to obtain powders with a uniform particle size distribution for polyimide, and this molding method can be used to process preforms. It is not a simple molding method that may be necessary.

First, polyimide fibers are used, and the polyimide fibers are preformed into a nonwoven fabric or felt, and the polyimide fiber nonwoven fabric or felt is heated / pressurized at a temperature exceeding the glass transition point of the polyimide for an appropriate time. The heat-resisting air-permeable molded product having a desired shape having sufficient rigidity to be self-sustaining by being contracted by the above, and succeeded in obtaining a heat-resistant filter material, was successfully applied for a patent (Japanese Patent Application No. 5-62534).
No.) The heat-resistant breathable molded product from this polyimide fiber is a filter material when processed into a tubular shape, a box shape, or the like,
The tubular filter medium can be integrally formed, but when it is processed into a box-like shape, a joining process is required, and the joining for that is performed by stitching with a thread.

[0004]

The molded article having rigidity obtained by heating and shrinking the above-mentioned non-woven fabric made of polyimide fiber or felt requires a joining process in order to form a box shape as a filtering material, Conventionally, the parts to be joined are sewn together with thread, but it is difficult to make a complicated and large shape with the suture method using thread, and the powder to be filtered leaks from the seam of the suture part, and the filtration time There has been a problem that the seam expands and the leakage increases with the passage of. It should be noted that conventional attempts to bond with a curable adhesive require a long time to cure the adhesive while maintaining it under pressure. Furthermore, if the viscosity of the adhesive is low, the nonwoven fabric or felt fibers may be There was a problem that it penetrated deeply into the space and the strength of the adhesive surface decreased. The present invention eliminates the drawbacks of the prior art, is heat resistant, is less likely to clog,
An object of the present invention is to provide a method for producing a heat-resistant filter material which has a long life and is made of polyimide fiber having air permeability, and at the same time, which has such a complicated and large size and is self-supporting and rigid.

[0005]

The object of the present invention is achieved by the self-supporting filter material of the present invention and the method for producing the same. That is, (1) a self-sustaining three-dimensional structure is obtained by fusing a heat-resistant air-permeable molded article made of polyimide fibers having a repeating unit represented by the following general formula (1) with a thermoplastic polyimide. A self-supporting filter material characterized by:

[0006]

[Chemical 3]

And (2) A filter material having a three-dimensional structure which can be self-supported by fusing a heat-resistant air-permeable molded article made of a polyimide fiber having a repeating unit represented by the following general formula (1) with a thermoplastic polyimide. A method for manufacturing a filter medium, the method comprising:

[0008]

[Chemical 4]

(3) In the method of fusing the above heat-resistant air-permeable molded body with thermoplastic polyimide,
The method for producing a filter medium according to claim ² , wherein the pressure is applied to 0.5 to 50 kg / cm ² in a temperature range of 315 ° C. to heat-seal. (4) In the method of fusing the heat-resistant air-permeable molded body with thermoplastic polyimide, the frequency is 50 to 400H.
mechanical vibration of z at a pressure of 1 to 10 kg / cm ² ,
The method for producing a filter medium according to claim 2, wherein heat fusion is performed by adding for 1 to 4 seconds.

The thermoplastic polyimide of the present invention has, for example, a repeating unit represented by the following chemical structural formula (2). To heat-seal the heat-resistant breathable molded article of the present invention using the thermoplastic polyimide of the present invention, as a method of applying the thermoplastic polyimide to the heat-resistant breathable molded article, a thermoplastic polyimide string, It can be applied in various forms such as tape and powder. For example, thermoplastic polyimide is processed into a tape shape, sandwiched between the above heat-resistant air-permeable molded articles, and both sides or one side of the portion to be fused is heated and pressed with a hot plate to melt and flow. When the thermoplastic polyimide of the present invention has an appropriate viscosity even when heated, the resin film is cut off. Spreads over the fiber layer of the breathable molded article so that the adhesive strength is not weakened. Thus, the thermoplastic polyimide of the present invention can be used to fuse a heat-resistant air-permeable molded body to give a filter material having a complicated shape and a large-scale self-supporting three-dimensional structure.

[0011]

[Chemical 5]

(Operation) The operation of the present invention will be described with reference to the drawings. The polyimide fiber felt 4 shown in FIG. 2 is sandwiched between the upper and lower two metal molds 5 and 6 as shown in FIG. 3 to be heated and pressed, and the breathable molding (shown in FIGS. 4 and 5 ( A)
2 and a breathable molded body (B) 3. Subsequently, the two breathable moldings 2 and 3 are superposed as shown in FIG. 1, and a book having a repeating unit represented by the chemical structural formula (2) in the portions indicated by a, b and c. For example, a tape-shaped product of the thermoplastic polyimide of the invention is sandwiched, a hot plate is applied to the sandwiched portions a, b, and c, and heat and pressure are applied to fuse them together to form a self-supporting three-dimensional structure shown in FIG. Filter medium 1 was formed.

Here, the thermoplastic polyimide having the repeating unit represented by the chemical structural formula (2) of the present invention has an appropriate viscosity even when heated at the stage of the adhesive,
It spreads to the fiber layer of the breathable molded article to such an extent that the resin film is not broken by pressure and the adhesive strength is not weakened. Then heat
At the stage where the condensation rapidly progresses during the pressurization and the fusion is completed, the molded filter medium can exhibit the desired heat resistance. The properties exhibited by such thermoplastic polyimides of the present invention are due to the degree of condensation of the polyimide at the stage of adhesion, rather than to the chemical structure of its monomers.

As another method for fusing the heat-resistant air-permeable molded body with the thermoplastic polyimide of the present invention, the present thermoplastic polyimide is sandwiched between the air-permeable molded bodies, and both sides of the portion to be fused are bonded. Alternatively, a method in which mechanical vibration is applied to one side to melt and flow one side is also applicable. By this other method of applying mechanical vibration, the adhesive can penetrate into the fiber layer of the breathable molded article to bond the same, similar to the method of heating and pressurizing, to form a complex shape and large-scale self-sustainability. It is possible to provide a filter material having a three-dimensional structure. In this case, a commercially available vibration welder can be applied to the welder by applying mechanical vibration to the adherend. The use condition of the vibration welder for fusion bonding is, for example, by generating mechanical vibration with a frequency of 50 to 400 Hz and an amplitude of 1 to 4 mm and applying it to the adhered portion under a pressure of 1 to 10 kg / cm ² for 1 to 10 seconds. It can be fused.
However, it does not necessarily have to be within this fusion-bonding condition, and the optimum fusion-bonding condition changes depending on the type of welder, the type of adhesive, and the like. Therefore, it suffices to obtain the optimum fusion bonding conditions by trial and fuse them.

According to the present invention, a heat-resistant air-permeable molded article formed from a non-woven fabric or felt made of polyimide fiber with thermoplastic polyimide is fused at a temperature of 260 ° C. with the thermoplastic polyimide of the present invention using an adhesive. Also provides a method capable of producing a filter material having a complicated shape and a large, self-supporting three-dimensional structure that can be used for a long time.

[0016]

The filter material and the method for producing the same according to the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the experimental examples described below.

Experimental Example 1 Benzophenone-indicated by the following chemical structural formula (3):
Needle punch from polyimide fiber made from 3,3 ', 4,4'-tetracarboxylic dianhydride and 4,4'-methylene-bis- (tolylene isocyanate) with a draw ratio of 1: 5 and a thickness of 30 μm Basis weight 47 produced by the method
A needle felt shown in FIG. 2 having a thickness of 5 g / m ² and a thickness of 3 mm was produced.

[0018]

[Chemical 6]

The needle felt 4 was heated to about 340 ° C. and molded to prepare two breathable molded bodies 2 and 3 shown in FIGS. 4 and 5. The above-mentioned two breathable molded bodies were stacked as shown in FIG. 3, and the thickness of 0.5 was applied to the portions a, b and c.
A thermoplastic polyimide tape having a repeating unit represented by the above chemical structural formula (2) having a width of 10 mm and a width of 10 mm was sandwiched. Then, at the overlapping portion of a, b, and c where the thermoplastic polyimide tape is sandwiched, a temperature of 275
A heating plate at a temperature of 50 ° C. was applied, and a pressure of 50 kg / cm ² was maintained for 15 minutes for fusion to form a filter material having a three-dimensional structure capable of standing as shown in FIG. Width 10 mm, length 120 from the fused part
A rectangular test piece of mm was cut out and the 180 ° peel strength was measured. The results are shown in Table 1.

[0020]

[Table 1]

In the following experimental examples, "two breathable moldings were stacked as shown in FIG. 3 in the above experimental example, and thermoplastic polyimide tape was sandwiched between the portions a, b and c. The molded product is referred to as the molded product of Experimental Example 1 for reference.

Experimental Example 2 In the overlapping portion of a, b and c of the molded article of Experimental Example 1,
A hot plate having a temperature of 295 ° C. is applied, and a pressure of 20 kg / cm ² is kept for 30 minutes for fusion to form a self-supporting three-dimensional filter material having a 180 ° peel strength at the fused portion. It was measured. The results are shown in Table 1.

Experimental Example 3 In the overlapping portions of a, b and c of the molded article of Experimental Example 1,
A hot plate having a temperature of 315 ° C. is applied, and a pressure of 0.5 kg / cm ² is maintained for 20 minutes for fusion to form a self-supporting three-dimensional structure of the filtration material, and 180 ° peeling strength of the fusion bonded portion is formed. Was measured. The results are shown in Table 1.

Experimental Example 4 In the overlapping portion of a, b and c of the molded article of Experimental Example 1,
A hot plate having a temperature of 250 ° C. is applied, and a pressure of 20 kg / cm ² is maintained for 30 minutes for fusion to form a self-supporting three-dimensional filter material having a three-dimensional structure, and the 180 ° peel strength of the fused portion is obtained. It was measured. The results are shown in Table 1.

Experimental Example 5 At the overlapping portions of a, b and c of the molded article of Experimental Example 1,
A hot plate having a temperature of 340 ° C. is applied, and a pressure of 20 kg / cm ² is maintained for 15 minutes for fusion to form a self-supporting three-dimensional filter material having a three-dimensional structure. It was measured. The results are shown in Table 1.

Experimental Example 6 In the overlapping portion of a, b and c of the molded article of Experimental Example 1,
A hot plate having a temperature of 295 ° C. is applied, and a pressure of 60 kg / cm ² is kept for 15 minutes for fusion to form a self-supporting three-dimensional filter material having a 180 ° peel strength at the fused portion. It was measured. The results are shown in Table 1.

Experimental Example 7 On the superposed portions of a, b and c of the molded article of Experimental Example 1,
A hot plate having a temperature of 295 ° C. is applied, and a pressure of 0.2 kg / cm ² is maintained for 20 minutes for fusion to form a filter material having a three-dimensional structure capable of self-sustaining as shown in FIG. Was measured. The results are shown in Table 1.

Experimental Example 8 The overlapping portions of a, b and c of the molded product of Experimental Example 1 were
With a vibration welder (manufactured by Japan Emerson Co., Ltd.), transverse vibration having a frequency of 50 Hz and an amplitude of 1.5 mm was applied for 4 seconds under a pressure of 10 kg / cm ² to cause fusion, and the self-supporting three-dimensional structure shown in FIG. Forming a filter material,
The 180 ° peel strength of the fused portion was measured. The results are shown in Table 2.

[0029]

[Table 2]

Experimental Example 9 The overlapping portions of a, b and c of the molded product of Experimental Example 1 were
With a vibration welder, frequency 240Hz,
A lateral vibration with an amplitude of 1.5 mm was applied under a pressure of 5 kg / cm ² for 3 seconds to fuse the two, to form a self-supporting three-dimensional structure filter material, and the 180 ° peel strength of the fused portion. Was measured. The results are shown in Table 2.

Experimental Example 10 The overlapping portions of a, b and c of the molded product of Experimental Example 1 were
Vibration welder, frequency 400H
Transverse vibration with z and amplitude of 1.5 mm is applied for 1 second under a pressure of 1 kg / cm ² to cause fusion to form a self-supporting three-dimensional filter material having a three-dimensional structure, and the fused portion is peeled by 180 °. The strength was measured. The results are shown in Table 2.

Experimental Example 11 The overlapping portions of a, b and c of the molded product of Experimental Example 1 were
With a vibration welder, transverse vibration with a frequency of 40 Hz and an amplitude of 1.5 mm was applied under a pressure of 5 kg / cm ² for 3 times.
The mixture was added for 2 seconds and fused to form a filter material having a three-dimensional structure capable of standing as shown in FIG. 1, and the 180 ° peel strength of the fused portion was measured. The results are shown in Table 2.

Experimental Example 12 The overlapping portions of a, b and c of the molded product of Experimental Example 1 were
With a vibration welder, frequency 240Hz,
Transverse vibration with an amplitude of 1.5 mm was applied for 3 seconds under a pressure of 0.5 kg / cm ² to fuse the two, to form a self-supporting three-dimensional structure filter material as shown in FIG. 1, and peel the fused portion by 180 °. The strength was measured. The results are shown in Table 2.

Experimental Example 13 The overlapping portions of a, b and c of the molded product of Experimental Example 1 were
With a vibration welder, frequency 240Hz,
Transverse vibration with an amplitude of 1.5 mm was applied for 0.5 seconds under a pressure of 5 kg / cm ² to fuse and form a filter material having a self-supporting three-dimensional structure as shown in FIG. 1, and peeling the fused portion by 180 °. The strength was measured. The results are shown in Table 2.

Experimental Example 14 The overlapping parts of a, b and c of the molded product of Experimental Example 1 were
With a vibration welder, frequency 240Hz,
Transverse vibration with an amplitude of 1.5 mm was applied for 3 seconds under a pressure of 15 kg / cm ² to cause fusion to form the self-supporting three-dimensional structure of the filter material, and the 180 ° peel strength of the fused portion. Was measured. The results are shown in Table 2.

[0036]

INDUSTRIAL APPLICABILITY The present invention can produce a heat-resistant filter material having a complicated shape and a large-scale, self-supporting three-dimensional structure which can be used for a long period of time even at a temperature of 260 ° C., which was difficult by the conventional suturing method. It is a thing. When the thermoplastic polyimide used as the adhesive sheet is heated / fused and thermoset, it has heat resistance equivalent to that of a heat-resistant and air-permeable molded article having rigidity, which is obtained by heating / shrinking the polyimide fiber nonwoven fabric or felt. However, since it exhibits thermoplasticity before being fused, the adhesive surfaces of the two molded bodies can be firmly fused, and thus a filter material without powder leakage can be manufactured.

[Brief description of drawings]

FIG. 1 is a perspective view showing a self-supporting filter material of the present invention.

FIG. 2 is a perspective view showing a starting material for manufacturing a filter medium of the present invention.

FIG. 3 is an explanatory view showing a mold forming step of manufacturing the filter medium of the present invention.

FIG. 4 is a perspective view showing one of the intermediate molded products for manufacturing the filter medium of the present invention.

FIG. 5 is a perspective view showing another one of the intermediate molded products for producing the filter medium of the present invention.

[Explanation of symbols]

 1 Filter Body 2 Breathable Molded Body (A) 3 Breathable Molded Body (B) 4 Felt 5 Upper Metallic Mold 6 Lower Metallic Mold a, b, c Joining Part

Claims (4)

[Claims] 1. A heat-resistant air-permeable molded article made of a polyimide fiber having a repeating unit represented by the following general formula (1) is obtained by fusing with a thermoplastic polyimide,
A self-supporting filter material that retains a self-supporting three-dimensional structure. [Chemical 1] 2. A self-standing filter material having a three-dimensional structure is produced by fusing a heat-resistant air-permeable molded article made of a polyimide fiber having a repeating unit represented by the following general formula (1) with a thermoplastic polyimide. A method for producing a filter medium, comprising: [Chemical 2] 3. A method of fusing the above heat-resistant air-permeable molded body with thermoplastic polyimide, comprising:
The method for producing a filter medium according to claim ² , wherein the pressure is applied to 0.5 to 50 kg / cm ² in a temperature range of 5 ° C. to heat-seal. 4. A method of fusing the heat-resistant air-permeable molded article with a thermoplastic polyimide, wherein a frequency of 50 to 50 is used.
The method for producing a filter medium according to claim 2, wherein the heat sealing is performed by applying a mechanical vibration of 400 Hz under a pressure of 1 to 10 kg / cm ² for 1 to 4 seconds.