JP2003082111A - Production method for fluororesin and filtration dehydration apparatus used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method for a fluororesin whereby the water content can be lowered and the handleability (fluidity) after drying can be improved without changing the physical properties; and a filtration dehydration apparatus which can filtrate coagulated particles in a short time, can quantitatively discharge the coagulated particles after dehydration, and is used in the production method for the fluororesin. SOLUTION: The filtration dehydration apparatus is equipped with a filtration cylinder having an inlet and an outlet ports for coagulated particles and a wire screen arranged in the peripheral direction; a rotation support for freely rotatably supporting the filtration cylinder; a rotating means for rotating the filtration cylinder; a spiral transport means arranged on the inner wall of the filtration cylinder for transporting the coagulated particles to the outlet port by rotation; and a quantitative discharge mechanism arranged on the downstream side of the filtration cylinder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluororesin production method and a filtration / dehydration apparatus used in the production method. More specifically, the present invention relates to a method for producing a fluororesin which separates (dehydrates) water from aggregated particles after polymerization or coagulation and further after granulation in the production process of a fluororesin, and a filtration dehydrator used in the method.

[0002]

2. Description of the Related Art Conventionally, a dispersion of a fluororesin prepared by emulsion polymerization is produced by coagulating, then dehydrating and drying the fluororesin. In the case of suspension polymerization in which particles are precipitated during the polymerization, dehydration and drying are carried out after washing. Further, when granulating them using hot water or a solvent after polymerization, they are similarly dehydrated and dried to produce a fluororesin. As an apparatus used for producing the fluororesin, there is an apparatus for dehydrating by gravity filtration (hereinafter, simply gravity filtration). The dehydration after coagulation in this apparatus is usually carried out by passing through a wire net and filtering. However, the polymer adheres to the filtration surface of the wire mesh, causing clogging. Therefore, the filtration rate is rapidly reduced, and a sufficient filtration area cannot be secured. Also, in order to reduce the drying load in the next step, it is preferable that the water content is as low as possible. For example, polytetrafluoroethylene (PTF
In the gravity filtration of E), the water content is about 100% (dry standard).

If it is attempted to reduce the water content by applying mechanical force to the agglomerated particles instead of the mere gravity filtration, the physical properties of the product may change after drying and the agglomerated particles may become fibrous. For this reason, it will adversely affect the product during extrusion molding, such as uneven quality, and it is necessary to dehydrate with care so as not to apply a local load to the agglomerated particles during handling. Gravity filtered.

Further, a method of continuously coagulating and granulating is
It has already been published, but on the other hand, batch-type coagulation is also used. In this batch type coagulation, a stirring tank using an end plate is used to enhance the effect of coagulation.
When a batch of agglomerated particles is discharged to the outside of the coagulation tank, unless a large amount of entrained water and a water flow are generated and discharged, many agglomerated particles remain in the stirring tank. For this reason, it is necessary to discharge the agglomerated particles containing a large amount of entrained water at one time and to filter, and it is difficult to discharge the required amount. Therefore, in most of the conventional devices, a separate filtering facility for discharging the particles all together for filtration is installed to dehydrate, and then the required amount is again taken out manually.

Although various methods are used in the drying method in the post-process, a constant quantity discharge performance is required in both the continuous method and the batch method.

[0006] As described above, under the present circumstances, it is required that the transition from the batch system to the continuous system can be carried out smoothly, and at the same time, the required physical properties of the product at the time of drying can be maintained to improve the handling property and improve the quantitative performance. Equipment that can be discharged to

In view of the above circumstances, the first object of the present invention is to provide a fluororesin which can reduce the water content without changing the physical properties and improve the handling property (fluidity) after drying. It is to provide a manufacturing method.

A second object of the present invention is to provide a filtration / dehydration apparatus for use in the above-mentioned fluororesin production method, which is capable of filtering aggregated particles in a short time and quantitatively discharging the aggregated particles after dehydration. That is.

[0009]

The method for producing a fluororesin of the present invention comprises: agglomerating particles containing a fluororesin are rotated in a circumferential direction by a filter cylinder having a wire screen, and the gravity of the agglomerated particles is reduced. It is characterized in that it is dehydrated by using it to roll it.

Further, the filtration / dehydration apparatus of the present invention has an inlet and an outlet for the aggregated particles, and a filtration cylinder in which a wire screen is arranged in the circumferential direction, and the filtration cylinder is rotatably supported. A rotation supporting part, a rotation driving means for driving the filtration cylinder to rotate, a spiral feed plate disposed on the inner wall of the filtration cylinder for moving the aggregated particles to an outlet by rotation, and It is characterized by comprising a fixed amount discharge mechanism arranged on the downstream side.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Usually, a fluororesin is manufactured as follows. First, the fluorine monomer is mixed with a medium such as water and other raw materials. The raw material is polymerized by suspension polymerization, emulsion polymerization or the like to produce a polymer from a monomer. Unreacted monomer, solvent, catalyst, etc. are removed from the reaction system to separate the produced polymer. Then, this polymer is dehydrated and dried, and if necessary, molded to produce. Here, when polymerized by suspension polymerization, the polymer particles often have an average particle size of 100 μm or more in many cases, and can be directly applied to this method. However, in the case of emulsion polymerization, the separation operation is complicated. The obtained polymer is an emulsion (emulsified state), and when it is aggregated, dehydrated, and dried, a powdery fluororesin can be obtained. The present invention can be applied to a fluororesin polymerized by either suspension polymerization or emulsion polymerization.

When the average particle size of the polymer fine particles is small, it can be granulated in hot water, water, a solvent, a mixture of a solvent and water, or the like to a size applicable to the present method. As a granulation method, Japanese Patent Publication No. 44-22619
Japanese Patent Publication, Japanese Examined Patent Publication No. 3-39105, Japanese Patent Publication No. 48-3
Japanese Patent Publication No. 7576, Japanese Patent Publication No. 49-17855, Japanese Patent Publication No. 60-21694, and a method of stirring PTFE powder in water in the presence of an organic liquid.
No. 3-47447, a method of precipitating a filler by a chemical reaction in a PTFE aqueous dispersion to agglomerate both, an organic liquid forming a liquid-liquid interface with water described in WO97 / 11111. And a method of stirring a mixture of PTFE powder and a filler in water in the presence of a nonionic surfactant, WO 97/1
After the PTFE powder and the filler described in the No. 5611 pamphlet are separately put into water and stirred in the presence of a surfactant to be mixed to form a slurry, or PT
Examples include a method in which only the FE powder is made into a slurry state, a filler is added, and further stirring is performed in the presence of an organic liquid. In the present invention, it can be applied to a fluororesin granulated by any of these methods.

The particle size to which the present method is applicable depends largely on the size of the screen and is not particularly limited. However, in terms of improving the dehydration efficiency, 1
It is preferably larger than 00 μm, more preferably larger than 150 μm. Further, the upper limit is preferably 3 mm, and more preferably 1 mm.

The resin to which this method can be applied is not particularly limited as long as it contains a fluororesin, but from the viewpoint of improving the performance of the fluororesin, a resin containing a filler such as glass or carbon. It is also applicable to. The present invention is particularly preferably applied when the resin is agglomerated particles obtained by coagulating dispersion.

Next, the agglomerated particles are put into a filtration cylinder having a wire screen arranged in the circumferential direction. Dehydration is performed by rotating the filtration cylinder and rolling the agglomerated particles using its own gravity. At this time, the rotation speed of the filtration cylinder is determined by the size of particles and the like, but the peripheral speed is preferably 0.5 to 1.5 m / s. Further, it is preferably 0.7 to 1.3 m / s, and particularly preferably 0.8 to 1.2 m / s. When the rotation speed is less than 0.5 m / s, the agglomerated particles tend to slide on the inner surface of the filtration cylinder but do not roll. Further, when the rotation speed exceeds 1.5 m / s, the particles tend to be enlarged.

The method for producing the fluororesin of the present invention and the filtration dehydrator used in the method will be described below with reference to the accompanying drawings.

FIG. 1 is a vertical sectional view showing an embodiment relating to the filtration and dehydration apparatus of the present invention, FIG. 2 is a sectional view taken along the line I--I of FIG. 1, and FIG. 3 is a sectional view of a main part of a wedge wire screen.
FIG. 4 is a sectional view taken along line II-II in FIG.

As shown in FIGS. 1 to 4, a filtration and dehydration apparatus 1 according to one embodiment of the present invention has a liquid receiving section 2 for storing water separated from agglomerated particles at a lower portion thereof and is made of a steel material. A cylindrical filter cylinder 6 supported by the assembled base body 3 and having an inlet 4 and an outlet 5, a rotary support 7 for rotatably supporting the filter cylinder 6, and the filter cylinder. It is composed of a rotation driving means for rotating the body 6, a spiral feed plate 8 arranged on the inner wall of the filtration cylinder 6, and a fixed amount discharge mechanism A arranged on the downstream side of the filtration cylinder 6. ing. The rotation driving means and the fixed amount discharge mechanism A are controlled by a controller (not shown) so as to perform a predetermined operation. In addition, F is a rotation direction.

The filtering cylinder 6 comprises a frustoconical input part 9, a body 11 having a framed screen 10 and a discharge part 12. In the present embodiment, the screen 10 is a longitudinal part of the body 11. It is arranged in three rows of positions. A cylindrical charging chute 13 is inserted through the charging port 4 of the charging unit 9 for charging the aggregated particles. The screen 10 includes a plurality of wedge wires 14 each having a wedge-shaped cross section and assembled with the tip edge portions 14a facing outward, and is reinforced from the outside by a reinforcing member 15. The wedge wire screen 10 is extremely less clogged except for the reinforcing member 15.
The occupancy rate and array shape of the screen 10 can be appropriately set in consideration of the particle size and amount of the agglomerated particles, the dehydration work efficiency, and the like. For example, the wedge wire 14
The arrangement of each wedge wire depends on the particle size of the agglomerated particles.
The gap S between the four can be about 125μ.

As the rotation supporting portion 7, the filter cylinder 6 is used.
The structure is not particularly limited as long as it can support the rotating body (not shown), which is rotatably attached to the base body 3 and supports the lower part of the charging unit 9 at two points.
The cylindrical portion 16 of the discharge portion 12 may be configured to include a rotating body (not shown) that supports the cylindrical portion 16 at two points. Further, in the present embodiment, in order to support the movement of the filtering cylinder 6 in the thrust direction, the rotating body group 17 that engages with the half-moon frame 17a having a U-shaped cross section attached to the base body 3.
Are attached to the input portion 9 and the cylindrical portion 16, respectively. A roller or the like can be used as the rotating body and the rotating body of the rotating body group 17.

The rotation driving means comprises a sprocket 18 fixed to the cylindrical portion 16, a drive motor (not shown) to which a sprocket (not shown) is attached, and a chain 19 wound around both sprockets. ing. This rotation drive means can be set so that the filtration cylinder 6 is rotated, for example, 12 times per minute.

The spiral feed plate 8 is a double spiral that moves the aggregated particles to the discharge port 5 by rotation, and has a total length of 7.5 turns. The spiral feed plate 8 uses the gravity of the particles without directly applying a mechanical force to the agglomerated particles to drop and move the agglomerated particles toward the discharge unit 12 side by rotation. A spiral shape (width of feed plate, pitch, lead, etc.)
Can be appropriately selected depending on the inner diameter of the filter cylinder 6, the body length, and the speed at which the agglomerated particles are moved to the discharge section 12 side by rotation.

The fixed amount discharge mechanism A has a plurality of water wheel-shaped buckets 20 arranged so as to surround the discharge port 5 on the outer peripheral portion of the discharge port 5, and is inserted into the discharge port 5 from the outside. Emission control means 21 for controlling the discharge amount of aggregated particles
And a delivery means 22 for delivering the agglomerated particles discharged by the discharge control means 21. This quantitative discharge mechanism A
Is capable of discharging agglomerated particles according to the number of rotations of the filtration cylinder 6 by sequentially changing the gradient of the bucket 20 with the rotation of the filtration cylinder 6, whereby the discharge amount can be adjusted. . The bucket 20 has a base portion 20a fixed to the inner wall of the discharge portion 12, and has a curved front end and an open upper end and rear end. The opening at the rear end is directed to the discharge port 5. The discharge restricting means 21 includes a discharge gate member 25 including a pair of parallel supporting portions 23 arranged to face each other and an inclined plate 24 fixed to an inclined surface at the tip of the supporting portion 23, and the inclined plate. And a drive unit such as a drive motor 26 for reversing 24. The delivery means 22 receives the agglomerated particles that have passed through the discharge gate member 25.
7 and a discharge hopper 28 that sequentially discharges the agglomerated particles sent from the discharge bell mouth 27 by vibration. Below the discharge hopper 28, a discharge feeder 29 equipped with a vibrator is arranged. As a result, when the discharge gate member 25 is inverted after the filtration cylinder 6 has rotated a predetermined number of times, the discharge bell mouth 27 has
A predetermined amount of aggregated particles are sent out through the discharge gate member 25. Therefore, the discharge amount can be adjusted by the timing of rotating the filtration cylinder 6 and reversing the discharge gate member 25. Therefore, a large amount of the aggregated particles collectively charged into the charging unit 9 is dehydrated and then discharged by a necessary amount. can do.

In the present embodiment, it is preferable that a washing means is provided in order to jet the washing water to the agglomerated particles in the process of dehydration to wash the trace components during the polymerization. As this cleaning means, a cleaning means which is attached to the base body 3 and which comprises a particle cleaning nozzle 31 which is inserted from the outside into the charging port 4 and a water absorption pump (not shown) can be used.
The particle cleaning nozzle 31 has at least one nozzle, and can be appropriately extended to the inside of the filtration cylinder 6. In the present embodiment, the nozzle of the particle cleaning nozzle 31 is set to face the lower part of the filter cylinder 6. As a result, as shown in FIG. 4, in the surface portion of the aggregated particle group having an arcuate cross-sectional shape, after the aggregated particles are lifted by the rotation of the filtration cylinder, most of the particles roll down according to the gradient. Since the surface of the aggregated particle group is renewed by the movement, all the aggregated particles come into direct contact with the washing water, so that efficient washing can be performed.

In the present embodiment, by rotating the filtration cylinder while utilizing the gravity of the agglomerated particles, the free water adhering to the agglomerated particles and a proper compression action during the rolling using the gravity. Thereby, the water trapped in the agglomerated particles can be extruded and separated. Also, at the same time as lowering the water content, the rolling of the agglomerated particles smoothes the surface state of the particles to improve handling, and due to the sliding phenomenon of some agglomerated particles, the clogging particles on the screen filtration surface are impacted. To prevent clogging. Further, the aggregated particles containing a large amount of entrained water can be filtered in a short time to quantitatively discharge the dehydrated aggregated particles.

[0026]

EXAMPLES Next, the filtration and dehydration apparatus according to the present embodiment will be described based on Examples, but the present invention is not limited to such Examples.

Example 1 A dispersion containing polymer particles was obtained from a tetrafluoroethylene monomer by ordinary emulsion polymerization using ammonium persulfate as a catalyst. This dispersion is coagulated with a high-speed stirrer to produce agglomerated particles (particle size 500μ
m).

First, the inner diameter is 600 mm and the total body length is 8
25 mm (of which the rotating bucket length is 75 mm)
A filter dehydrator having a filter cylinder in which three rows of wedge wire screens were arranged on the body was prepared. The area of each wedge wire screen is 0.694 m ² , and the gap between the wedge wires is 125 μ. In addition, the total number of turns of the spiral feed plate installed in this body is 7.
It has 5 rolls.

Then, a slurry liquid containing the agglomerated particles was introduced into the filtration cylinder rotating at 12 revolutions per minute at a rate of 50 liters / minute from a charging chute, and the entrained water passed through the wedge wire screen and was discharged. It was discharged to the receiving part. On the other hand, the agglomerated particles, while being washed by the washing water from the particle washing nozzle, were lifted to the angle of repose by the rotation of the filtration cylinder, and then were sent to the outlet side according to the guide of the spiral feed plate while rolling. .

These operations were repeated in accordance with the rotation of the filter cylinder, and after about 7.5 rotations, the agglomerated particles arrived at the terminal end of the spiral feed plate. Since a large number of buckets were installed at this arrival place, the arrived aggregated particles after dehydration were scooped up by the buckets rotated by the rotary motion of the filtration cylinder. The scooped-up agglomerated particles fell when the bucket had an inclination opposite to the original due to the rotation of the filtration cylinder, and were discharged to the discharge bell mouth by the guide of the reverse discharge gate. Then, the agglomerated particles dropped into the discharge hopper were discharged outside the apparatus by the discharge feeder at a stable discharge rate of 2 kg / min.

Comparative Example 1 A filtration experiment was carried out using a conventional apparatus for filtering and dehydrating by passing through the above-mentioned wire mesh.

As a result, in comparison with Comparative Example 1, the present Example reduces the water content by 20 to 25% without changing the physical properties relating to the molding of various products, and the handling (fluidity) after drying. And a dry powder which is free of blocking and has a smoothness was obtained.

Further, in this embodiment, even though dehydration utilizing gravity, long-term retention in the filtration cylinder is subjected to a lot of rolling load, so that very hard particles are produced and a great adverse effect occurs during extrusion molding. There is a fear of giving. Therefore, as an additional experiment, the distribution of residence time due to colored particles was also measured, but it was confirmed that the entire amount could be discharged within a specified time with extremely sharp extrusion characteristics.

Comparative Example 2 A test was carried out by using a wire mesh instead of the wedge wire screen of the filtration cylinder of the above-mentioned example. As a result, it was found that the product was dehydrated at first, but immediately after the aggregated particles passed over the wire mesh, it was clogged and clogged, so that it could not be dehydrated and could not be used.

In this example, a slurry containing a large amount of agglomerated particles was put into a batch and a dehydration test was conducted. However, the discharge amount after dehydration was quantified well in proportion to the rotation speed of the filtration cylinder. It turned out that it is possible to discharge various amounts.

[0036]

As described above, according to the production method of the present invention, since no mechanical force is applied, the powder after drying can be dehydrated without changing the physical properties of the powder.

Further, according to the filtration / dehydration apparatus of the present invention, the agglomerated particles, which are put into the filtration cylinder provided with the screen using the wedge wire having the wedge-shaped cross section, are rotated and agglomerated while rolling. Since the free water on the surface of the particles is separated and dehydrated, the water content of the agglomerated particles can be reduced to 4/5 as compared with the conventional method. Further, this can improve the handleability of the PTFE agglomerated particles after drying.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an embodiment of a filtration and dehydration apparatus of the present invention.

FIG. 2 is a sectional view taken along line I-I of FIG.

FIG. 3 is a cross-sectional view of a main part of a wedge wire screen.

FIG. 4 is a sectional view taken along line II-II of FIG.

[Explanation of symbols]

Quantitative discharge mechanism S gap 1 Filter dehydrator 2 liquid receiver 3 base body 4 slot 5 outlets 6 Filter cylinder 7 Rotation support 8 spiral feed plate 9 Input section 10 screens 11 torso 12 Discharge part 13 Input chute 14 wedge wire 14a Tip edge part 15 Reinforcement member 16 Cylindrical part 17 rotating colonies 17a half moon frame 18 sprockets 19 chains 20 buckets 20a base 21 Emission control measures 22 Sending means 23 Support 24 inclined plate 25 Discharge gate member 26 Drive motor 27 Discharge bell mouth part 28 Discharge hopper 29 Discharge feeder 31 cleaning nozzle

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 4D026 BA03 BB01 BC24 BC26 BC30                       BD01 BD06 BF09 BF21 BF22                       BH01                 4F070 AA23 DA39

Claims (8)

[Claims] 1. A fluororesin for dehydrating agglomerated particles containing a fluororesin by rotating a filtration cylinder having a wire screen arranged in the circumferential direction and rolling by using gravity of the agglomerated particles. Manufacturing method. 2. The method for producing a fluororesin according to claim 1, wherein the agglomerated particles containing the fluororesin are agglomerated particles obtained by coagulating latex. 3. The rotation speed of the filtration cylinder is 0.5 peripheral speed.
It is-1.5 m / s, The manufacturing method of the fluororesin of Claim 1 or 2. 4. A filtration cylinder having an inlet and an outlet for aggregated particles and having a wire screen arranged in the circumferential direction,
A rotation support portion that rotatably supports the filtration cylinder, a rotation drive unit that rotationally drives the filtration cylinder, and an inner wall of the filtration cylinder that are arranged to move the aggregated particles to an outlet through rotation. A filtration / dehydration device comprising a spiral feed plate and a fixed amount discharge mechanism arranged on the downstream side of the filtration cylinder. 5. The filtration / dehydration device according to claim 4, wherein the wire screen is a wedge wire screen. 6. The fixed amount discharge mechanism, a plurality of buckets arranged at an outer peripheral portion of the discharge port, discharge regulation means which is inserted into the discharge port from the outside and regulates the discharge amount of the aggregated particles, The filtration / dehydration apparatus according to claim 4 or 5, further comprising a delivery means for delivering the aggregated particles discharged by the discharge control means. 7. The discharge restricting means includes a discharge gate member including a pair of parallel supporting portions and an inclined plate fixed to a tip of the supporting portion, and a driving portion for reversing the supporting portion and the inclined plate. The filtration dehydration apparatus according to claim 4, 5 or 6, which comprises: 8. The filtration / dehydration device according to claim 4, 5, 6 or 7, further comprising a cleaning means that is inserted from the outside into the input port.