JP3758469B2 - Continuous production method of thin fired mat of PTFE powder - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a continuous production method of a thin fired mat of polytetrafluoroethylene (hereinafter referred to as PTFE). More specifically, the present invention relates to a continuous manufacturing method of a sintered mat of PTFE powder having a thickness of about 3 mm and a bulk specific gravity of about 0.5, which is used for manufacturing a crosslinked PTFE powder. .
[0002]
[Prior art]
PTFE has excellent heat resistance, chemical resistance, corrosion resistance, releasability, slipperiness, and the like, and is widely used in various fields such as industrial fields and household products.
[0003]
One form of using PTFE is PTFE powder.
[0004]
The PTFE powder is produced by first producing a firing mat of the intermediate PTFE powder, and then producing a PTFE powder by finely pulverizing the firing mat of the intermediate PTFE powder. ing.
[0005]
FIG. 4 is a cross-sectional explanatory view showing a conventional method for producing a firing mat of PTFE powder.
[0006]
In FIG. 4, 1 is a jig for mat production, and 2 is a PTFE powder mat.
[0007]
That is, the conventional method for producing a firing mat of PTFE powder has been produced as follows.
[0008]
First, a mat manufacturing jig 1 as shown in FIG. 4 is prepared. The mat manufacturing jig 1 is formed by assembling two parallel flat plates so as to have a predetermined interval so as to have a narrow width and to close a lower portion thereof.
[0009]
Next, the upper opening of the mat manufacturing jig 1 is placed vertically so that the PTFE powder is put through the upper opening (not shown).
[0010]
Next, the PTFE powder is tamped by a slight self-adhesiveness by poking from the upper part, thereby forming a PTFE powder mat 2 having a thin predetermined bulk density.
[0011]
Next, the mat manufacturing jig 1 is disassembled, and the PTFE powder mat 2 is taken out.
[0012]
Next, the molded PTFE powder mat 2 is placed on a tray.
[0013]
Next, the PTFE powder mat 2 placed on the tray is put into a firing furnace, heated and fired for a predetermined time.
[0014]
[Problems to be solved by the invention]
However, the conventional PTFE powder firing mat manufacturing method has a drawback that the PTFE powder mat 2 formed with the mat manufacturing jig 1 is brittle and easily collapses.
[0015]
For this reason, in the conventional method for manufacturing a firing mat of PTFE powder, assembly of the mat manufacturing jig 1 → input of PTFE powder, tamping molding → disassembly of the mat manufacturing jig 1, and removal of the PTFE powder mat 2 → Tray loading → Tray loading PTFE powder mat 2 into firing furnace, firing → Tray loading PTFE powder mat 2 from the firing furnace must be manually performed.
[0016]
For this reason, the conventional method of manufacturing a PTFE powder firing mat is time-consuming, inefficient, and difficult to improve productivity and quality.
[0017]
Accordingly, a method for forming PTFE powder as shown in FIG. 5 has been proposed as an improvement method of the conventional method for producing a firing mat of PTFE powder.
[0018]
FIG. 5 is an explanatory front view showing a method for improving the conventional PTFE powder molding method.
[0019]
In FIG. 5, 3 is a flat plate, 4 is a PTFE powder, 5 is a blade for ironing, and 6 is a gap portion of the mat.
[0020]
That is, a conventional method for improving the molding of PTFE powder is performed as follows.
[0021]
First, a horizontal flat plate 3 is prepared, and PTFE powder 4 is piled on the flat plate 3.
[0022]
Next, an ironing blade 5 is installed vertically on one end side of the flat plate 3 on which the PTFE powder 4 is piled up. At this time, the distance between the lower end of the ironing blade 5 and the flat plate 3 is set to be the thickness of the PTFE mat to be molded.
[0023]
Next, when the straight ironing blade 5 is moved in the direction of the arrow, the PTFE powder 4 piled on the flat plate 3 is leveled to a uniform thickness.
[0024]
However, when the PTFE mat is thin in this improvement method, the PTFE powder has a solidification property due to slight self-adhesion at room temperature, so that the powder is loosely solidified by the vertical component force transmitted from the ironing blade 5. Become. When the powders are loosely solidified in this way, the powder 4 in the vicinity of the portion where the ironing blade 5 contacts is dragged to produce irregular voids 6, and the resulting PTFE mat has these irregularities. A defective portion called a regular gap portion 6 is generated.
[0025]
The present invention has been made in view of such a point. The purpose of the present invention is to eliminate the disadvantages of the prior art described above, and to perform a pre-forming operation for forming a PTFE powder into a mat having an initial thickness, and a preliminary operation thereof. PTFE powder capable of automatically and continuously performing a forming operation to form an unfired mat by compression-molding the formed initial thickness mat, and further, a firing operation to heat and fire the formed unfired mat Another object of the present invention is to provide a continuous production method of a fired mat.
[0026]
[Means for Solving the Problems]
The gist of the present invention is that a nonwoven fabric is slidably moved on a flat plate with a small hole on the top surface of a flat plate with a small hole, and the PTFE powder is thickly stacked on the nonwoven fabric. In addition, the upper part of the PTFE powder is rubbed with a powder ironing blade while moving the PTFE powder and the nonwoven fabric while keeping the negative pressure by sucking the hollow chamber with a blower. A mat having an initial thickness is preformed, and then the mat having an initial thickness preformed on the nonwoven fabric is compressed into a mat having a predetermined thickness by a compression roll to form an unfired mat, and then the mat is formed on the nonwoven fabric. The nonwoven fabric is separated from the molded unfired mat, and then the separated unfired mat is heated and fired at a temperature slightly higher than the melting point of the PTFE to form a fired mat. In a continuous manufacturing method of a thin sintered mat of PTFE powder that.
[0027]
In the present invention, the nonwoven fabric preferably has pores slightly smaller than the minimum particle size of the PTFE powder.
[0028]
In the present invention, the powder ironing blade is preferably mounted on the outer peripheral surface of a roll rotating bladed spreader roll.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of a method for continuously producing a firing mat of PTFE powder of the present invention will be described.
[0030]
The continuous production method of the PTFE powder firing mat of the present invention is characterized by the following.
[0031]
(1) A non-woven fabric whose pore size is smaller than the particle size of PTFE powder is placed on the upper surface of a chamber composed of a flat plate with a large number of small holes on the upper surface, and the upper surface is covered with PTFE powder. To.
[0032]
Next, when the inside of the chamber is sucked with a prower or a vacuum bump in such a state, atmospheric pressure acts and the PTFE powder is pressed against the nonwoven fabric.
[0033]
Thus, under the state where the PTFE powder is pressed against the non-woven fabric, even if it is squeezed, the powder is not dragged and a void is not generated.
[0034]
(2) While moving the PTFE powder together with the non-woven fabric, squeezing the upper part of the irregularly thick powder with a rotating jig with a blade that rotates at a fixed position, so that the bulk density of the uniform initial thickness is small A PTFE mat is preformed.
[0035]
Next, the preformed PTFE mat is compressed by a pressure roller that rotates in synchronization with the nonwoven fabric, thereby forming an unsintered PTFE mat having a predetermined thickness and a predetermined bulk density.
[0036]
(3) Next, the nonwoven fabric and the unsintered PTFE mat are separated.
[0037]
Next, the unsintered PTFE mat separated here is fed into a firing furnace where it is heated and fired to form a fired PTFE mat.
[0038]
By performing these series of operations continuously and automatically, a high-quality thin fired PTFE mat can be produced continuously and efficiently.
[0039]
【Example】
Next, an example of a method for continuously producing a firing mat of PTFE powder of the present invention will be described.
[0040]
(First Example of Continuous Manufacturing Method of Firing Mat of PTFE Powder of the Present Invention)
FIG. 1 is a plan view showing a first embodiment of a method for continuously producing a firing mat of PTFE powder of the present invention, and FIG. 2 is a front view thereof.
[0041]
1 and 2, 4 is PTFE powder, 7 is a flat plate with small holes, 8 is a suction chamber, 9 is a blower, 10 is a nonwoven fabric coil, 11 is a drive device for the nonwoven fabric winding device, 12 is a nonwoven fabric winding device, 13 is a long non-woven sheet, 14 is a blade for powder ironing, 15 is a spreader roll with blade, 16 is a spreader roll driving device, 17 is a compression roll, 18 is a compression roll driving device, 19 is a side plate, and 20 is a raw material powder. Hopper, 21 is a feeder for powder, 22 is an initial thickness mat, 23 is an unfired mat, 24 is an electric heater, 25 is a drive device for a mesh conveyor, 26 is a mesh conveyor, 27 is a firing furnace, and 28 is a firing Matt.
[0042]
Next, the operation procedure of the first embodiment of the method for continuously producing a firing mat of PTFE powder of the present invention will be described.
[0043]
(1) First, the inside of the suction chamber 8 having the small hole flat plate 7 on the upper surface is sucked by the blower 9.
[0044]
(2) Next, the non-woven fabric 13 drawn out from the non-woven fabric coil 10 and pulled and moved at a constant speed by the non-woven fabric winding device 12 equipped with the non-woven fabric winding device drive device 11 is passed through the upper surface of the suction chamber 8. .
[0045]
In addition, what has the following characteristics is used as a nonwoven fabric.
[0046]
a Pore size is slightly smaller than the minimum particle size of PTFE powder.
[0047]
b The tensile strength must be sufficiently large.
[0048]
(3) A spreader roll 15 with a blade having a powder ironing blade 14 is placed on the perforated metal flat plate 7 at a distance corresponding to the initial thickness of the nonwoven fabric 7.
[0049]
And this spreader roll 15 with a blade is rotated by the spreader roll drive device 16 in the direction opposite to the moving direction of the nonwoven fabric 7.
[0050]
(4) Next, on the downstream side of the spreader roll with blade 15, a compression roll 17 having a smooth surface is installed at a predetermined interval from the nonwoven fabric 7.
[0051]
Then, the roll surface speed of the compression roll 17 is rotated by the compression roll driving device 18 so as to synchronize with the moving speed of the nonwoven fabric 7.
[0052]
(5) Next, in the vicinity of the spreader roll with blade 15 and the compression roll 17, the side plate 19 is installed on the nonwoven fabric 7 at intervals corresponding to a predetermined mat width while maintaining a narrow gap.
[0053]
(6) Next, the blower 9 is operated, the long nonwoven fabric sheet 13 is moved at a constant speed, and the bladed spreader roll 15 and the compression roll 17 are rotated. A constant amount of PTFE powder is charged from the raw material hopper 20 installed in the front.
[0054]
Here, the PTFE powder charged from the raw material hopper 20 is sent to the powder feeder 21.
[0055]
(7) Next, the PTFE powder fed from the powder feeder 21 is fed to the 15 parts of the spreader roll with blade, where it is preformed into a mat 22 having an initial thickness.
[0056]
(8) Next, the mat 22 of the initial thickness preformed here is fed into the compression roll 17 and formed into an unfired mat 23 having a predetermined thickness and a predetermined bulk density.
[0057]
(9) Next, the unfired mat 23 formed here is provided with a mesh conveyor 26 using a mesh belt that is operated in synchronism with the nonwoven fabric 7 by an electric heater 24 and a mesh conveyor driving device 25. It is fed into the firing furnace 27.
[0058]
Here, the atmospheric temperature in the firing furnace 27 is kept slightly higher than the melting point of the PTFE powder.
[0059]
The unfired mat 23 is fired while passing through the firing furnace 27 at a constant speed, and becomes a firing mat 28 and is sent out from the firing furnace 27.
[0060]
The fired mat 28 obtained by performing the series of operations (1) to (9) automatically and continuously is of high quality with excellent dimensions, appearance and various characteristics, and its production. High nature.
[0061]
(Second embodiment of the continuous production method of the firing mat of PTFE powder of the present invention)
FIG. 3 is a partially omitted front explanatory view showing a second embodiment of the continuous production method of the firing mat of PTFE powder of the present invention.
[0062]
In FIG. 3, 4 is PTFE powder, 7 is a perforated metal flat plate, 8 is a suction chamber, 9 is a blower, 10 is a non-woven fabric coil, 12 is a non-woven fabric winding device, 19 is a side plate, 20 is a raw material powder hopper, 21 Is a feeder for powder, 22 is a mat having an initial thickness, 23 is an unfired mat, 29 is a fixed blade for powder ironing, and 30 is a fixed press plate for compressing the powder mat.
[0063]
That is, in the second embodiment of the continuous production method of the firing mat of PTFE powder of the present invention, instead of the spreader roll with blade 15 and the compression roll 17 used in the first embodiment, a powder as shown in FIG. The ironing fixed blade 29 and the mat compression fixing presser plate 30 are used.
[0064]
【The invention's effect】
According to the continuous production method of a thin fired mat of PTFE powder of the present invention, a fired mat of high quality PTFE powder having a small thickness, high dimensional accuracy, low specific gravity, and excellent appearance and various characteristics is automatically produced. And can be manufactured continuously and is industrially useful.
[Brief description of the drawings]
FIG. 1 is a plan view showing a first embodiment of a continuous production method of a PTFE powder firing mat according to the present invention.
FIG. 2 is an explanatory front view of FIG. 1;
FIG. 3 is a partially omitted front explanatory view showing a second embodiment of the method for continuously producing a firing mat of PTFE powder of the present invention.
FIG. 4 is a cross-sectional explanatory view showing a conventional method for producing a PTFE powder firing mat.
FIG. 5 is a front explanatory view showing a method for improving the conventional PTFE powder molding method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Mat manufacturing jig 2 PTFE powder mat 3 Flat plate 4 PTFE powder 5 Ironing blade 6 Matt gap 7 Flat plate with small holes 8 Suction chamber 9 Non-woven coil 11 Non-woven fabric winding device drive 12 Non-woven fabric winding Degreasing device 13 Long nonwoven fabric sheet 14 Powder ironing blade 15 Spreader roll with blade 16 Spreader roll drive device 17 Compression roll 18 Compression roll drive device 19 Side plate 20 Raw material powder hopper 21 Powder feeder 22 Mat of initial thickness 23 Unsintered mat 24 Electric heater 25 Mesh conveyor drive unit 26 Mesh conveyor 27 Firing furnace 28 Firing mat 29 Fixed ironing blade 30 for compacting powder mat Fixed presser plate for compressing powder mat

Claims (3)

A non-woven fabric is slidably moved on the flat plate with small holes formed on the flat plate with small holes on the upper surface, and a thick pile of PTFE powder is piled on the non-woven fabric. The mat of the initial thickness is preformed on the nonwoven fabric by squeezing the upper part of the PTFE powder with a powder ironing blade while moving the PTFE powder and the nonwoven fabric while maintaining a negative pressure by sucking with Then, after the mat with the initial thickness preformed on the nonwoven fabric is compressed into a mat with a predetermined thickness by a compression roll to form an unfired mat, the nonwoven fabric is formed from the unbaked mat formed on the nonwoven fabric. A thin fired PTFE powder characterized in that the fired mat is heated and fired at a temperature slightly higher than the melting point of the PTFE. Continuous manufacturing method of the door. The method for continuously producing a thin fired mat of PTFE powder according to claim 1, wherein the nonwoven fabric has pores slightly smaller than the minimum particle size of the PTFE powder. 2. The method for continuously producing a thin fired mat of PTFE powder according to claim 1, wherein the powder ironing blade is mounted on the outer peripheral surface of a roll-rotating bladed spreader roll.

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