JP2006302793A - Destaticizing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a destaticizing method of charged powders securing safety by avoiding dust explosion and fire due to electrostatic charges in a manufacturing process using charged powders and reducing weighing and measuring errors, and improving production efficiency with destaticizing in short period of time. <P>SOLUTION: This is a destaticizing method of charged powders and destaticizes by supplying an ionized inert gas to the charged powders in fluid state. Fluid state of the charged powders is obtained by free dropping of the powders or by using ionized inert gas to the transferred gas. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for removing charge from a charged powder, and more particularly, to a method for removing charge from a powder used in an industrial product manufacturing process.

  Since organic powders such as polymer compounds or inorganic powders such as ceramics are easily charged, when these charged powders are used as raw materials, it is necessary to consider the influence on safety and production efficiency in various processes.

  For example, a laminated board used as a printed wiring board substrate on which electronic parts are mounted is mixed with an inorganic powder such as silica powder, talc powder or alumina powder as an additive in a resin varnish containing an epoxy resin or the like. This is manufactured by molding. Such inorganic powders are less charged than conventional organic powders and are easy to handle. However, in order to form high-performance laminates, fine particles and surface treatments are being studied and powders that are easily charged It has become a body. For this reason, when powder is transported from a powder supply unit such as a raw material tank filled with powder to a mixing tank for mixing with other components, charged powder tends to adhere to the inner wall of the pipe. In the weight loss method by measuring the weight loss in the powder supply unit, accurate measurement is not possible, and the prescribed amount of other components cannot be blended, and powder adhering to the inner wall of the pipe is added to the mixing tank. In order to carry it, it is necessary to apply vibration from outside the piping, and there is a problem that the production efficiency is remarkably lowered. In addition, when powder is mixed with a flammable liquid such as an organic solvent to prepare a resin varnish, discharge may occur due to electrification, and dust explosion and fire may occur in a flammable gas atmosphere such as air. .

For this reason, it is necessary to neutralize the charge. As a charge neutralization method for the charged powder, it is necessary to neutralize the outer wall of the powder supply unit filled with powder, to supply an inert gas into the powder supply unit in advance, For example, it has been proposed to spray a neutralizing agent while stirring the powder (for example, Patent Document 1).
JP-A-7-192886

  However, since the charge removal from the outer wall of the powder supply unit is an indirect charge removal, it is necessary to remove the charge for a long time with a charged object such as a powder that is difficult to remove. In addition, once static elimination is performed, recharging occurs due to contact between powders in the powder supply unit, and when powder is conveyed from a powder supply unit such as a raw material tank, charging due to contact with the inner wall of the pipe It is not an essential solution because of the occurrence.

  In addition, since the introduction of inert gas is only gas supply, the effect of static elimination is low, and in the case of fine and bulky powder, the inert gas does not reach the inside of the powder layer, so sufficient static elimination cannot be performed. It is. For example, the inorganic powder used in the production of the laminated plate described above needs to have a charge amount of less than 20 kV in order to ensure safety, but it is 40 kV for static elimination only with an inert gas in the powder supply unit. It was found that static electricity can only be removed to a certain extent.

  Furthermore, since the composition varies in the blending process in the method of adding a static eliminating agent, it cannot be used in the manufacturing process of mixing with other components.

  On the other hand, a long charged object such as a film is set in a running state, and the surface of the film is neutralized with a rod-shaped electrode or the like. However, when the charged object is a powder, There is a problem that only the surface is neutralized due to the thickness of the powder layer, and if neutralization more than the charged charge is performed, the neutralization of the surface may progress too much and the reverse polarity may be charged. Thus, it is difficult to obtain a powder that has been neutralized, and it is difficult to change the neutralization condition according to the amount of charge of the powder.

  The present invention solves the above-described problems, and an object of the present invention is to provide a method for eliminating charge from a charged powder that can improve production efficiency while ensuring safety in a manufacturing process in which the charged powder is used.

  According to a first aspect of the present invention, there is provided a method for neutralizing a charged powder, wherein the charged powder is made into a fluidized state, and the charge is removed by supplying an ionized inert gas to the charged powder in the fluidized state. It is a feature.

  The neutralization method of the invention according to claim 2 of the present invention is characterized in that in the neutralization method of the invention according to claim 1, the flow state of the charged powder is formed by free fall of the powder.

  According to a third aspect of the present invention, there is provided a static elimination method for forming a fluidized state of a charged powder by using an ionized inert gas as a powder carrier gas in the neutralization method according to the first aspect of the present invention. It is characterized by this.

  Furthermore, the static elimination method of the invention according to claim 4 of the present invention is the static elimination method according to any one of claims 1 to 3, wherein the inorganic powder is a charged powder. A flow state is formed while supplying at 2 to 6 kg / min, and the ionized inert gas is supplied to the inorganic powder in the flow state at 30 to 300 L / min while the ionized inert gas is supplied to the inorganic powder. The charge amount is reduced by contact with the active gas for 30 seconds to 2 minutes.

  According to the static elimination method of the invention according to claim 1, since the static elimination is performed with the ionized inert gas, the static elimination effect is high, and the electrically charged powder is electrically charged in a shorter time than the static elimination with the inert gas alone. In addition to neutralization, it is possible to carry out static elimination with excellent safety because no flammable gas is used. In addition, since the inert gas is supplied to the charged powder in a fluidized state, continuous processing is possible, and charge removal can be performed to the inside of the powder layer, so that the charge amount of the entire processed powder is uniformized. And can reduce the adhesion of powder to the inner wall of the pipe, etc., so that it can be used for manufacturing processes where charged powder is used, so that it can be transported in a short time, and the measurement error is also reduced, resulting in production efficiency. Can be improved. Further, since the charge removal is performed by supplying an ionized inert gas, it is easy to change the charge removal conditions, and even when a powder with a different charge amount is removed, a desired charge removal suitable for the charged powder can be performed. .

  According to the static elimination method of the invention according to claim 2, since the flow state of the charged powder is formed by free fall, it is possible to eliminate static electricity while the powder is being conveyed in the manufacturing process, and it is necessary to separately provide a static elimination treatment facility. There is no. In addition, since the static elimination method of the present invention can perform static elimination in a short time, even when a fluidized state is formed by freely dropping the powder when the powder is conveyed from the powder supply unit, the static elimination is sufficiently performed. be able to.

  According to the static elimination method of the invention according to claim 3, in the case where it is desired to reduce the charged powder having a large charge amount or the charge amount after static elimination, contact between the charged powder and the ionized inert gas in the free fall of the powder. Since ionized inert gas is used as the carrier gas for the powder when sufficient time cannot be secured, the powder can be sufficiently discharged, and adhesion to piping and the like can be further reduced.

  According to the static elimination method of the invention according to claim 4, when the charged powder is an inorganic powder, the charge amount is reduced, and the safety of the manufacturing process at the time of manufacturing a laminated board mixed with a combustible liquid such as an organic solvent. And can improve the production efficiency.

(Embodiment 1)
FIG. 1 is a schematic configuration diagram showing an example of a processing apparatus for performing a static elimination method according to an embodiment of the present invention, in which a charged powder 1 is neutralized in the middle of a resin pipe 2, a mixing tank 3 and a pipe 2. It consists of an inert gas supply unit 4 that supplies ionized inert gas 5 to the pipe 2. Further, the processing apparatus is disposed in an explosion-proof area in a state of being electrically grounded. Although not shown, a raw material tank as a powder supply unit is disposed above the pipe 2, and an inert gas is provided. The supply part 4 is connected with the static elimination apparatus which ionizes an inert gas.

  Specific examples of the charged powder 1 to be neutralized in the present invention include inorganic powders such as silica powder, talc powder, and alumina powder, and organic powders such as polymer compounds. it can. In particular, the amount of charge increases as the silica powder becomes finer, and the silica powder, which is an industrial raw material for laminate production, uses fine particles with a particle size of 1 to 100 μm. The charge removal time tends to be prolonged, and when the powder is transported to the mixing tank 3, it is attached to the inner wall of the pipe 2 connecting the powder supply unit and the mixing tank 3. In addition, when a combustible organic solvent or the like is charged in the mixing tank 3, there is a problem in safety. For example, the above silica powder has a charge amount of about 40 kV when it is not neutralized, but it is necessary to make it less than 20 kV, preferably 10 kV or less, in order to avoid adhesion to the inner wall of the pipe and discharge due to charging. .

  Therefore, in the present invention, when the powder is transported from the raw material tank to the mixing tank 3, the charged powder 1 is in a fluid state by freely falling in one direction from the powder supply port of the pipe 2 to the discharge port in the middle of the pipe 2. Then, the ionized inert gas 5 is supplied into the pipe 2, and the charge is continuously removed by adjusting the gas flow rate so that the charged powder 1 has a predetermined charge amount.

  As the static eliminator of the present invention, a conventionally known device for generating ions for neutralizing the charge can be used, and there is no particular limitation as long as it can ionize an inert gas such as nitrogen or argon. For example, a method of applying a high voltage to the electrode to generate corona discharge to positively and negatively ionize the gas around the electrode, a method of ionizing an inert gas by irradiating energy such as soft X-rays, etc. Among them, an AC type static eliminator that generates positive and negative ions alternately by applying a voltage is preferable. If such a static elimination apparatus is used, the amount of ions can be controlled by the flow rate of the inert gas passing through the electrode portion. A suitable commercially available static neutralizer includes PAS801AL manufactured by Kasuga Electric Co., Ltd.

  The method for supplying the ionized inert gas 5 to the charged powder 1 is not particularly limited, and in addition to blowing with a fan or the like, blowing with a compressed gas, suction by reducing the pressure in the piping, or the like can be used.

  In the present invention, when the charged powder 1 is a fine inorganic powder such as silica powder, the amount of the inorganic powder supplied into the pipe for efficient charge removal to a charge amount of less than 20 kV is 2-6 kg / Minutes are preferred. In addition, the flow rate of the inert gas ionized at that time is preferably 30 to 300 L / min, and more preferably 100 to 200 L / min. By making the amount of the inorganic powder 2 kg / min or more and the flow rate of the ionized inert gas 30 L / min or more, efficient neutralization can be performed, and the amount of the inorganic powder is ionized 6 kg / min or less. By setting the flow rate of the inert gas to 300 L / min or less, even when a fine powder is used, floating in the pipe 2 can be suppressed and the dropping time to the mixing tank 3 can be reduced. Moreover, it is preferable to set it as 30 second-2 minutes, and it is more preferable to set it as 1-2 minutes as the contact time which the inorganic powder contacts with the ionized inert gas in the piping 2 which is a static elimination part. By setting the contact time to 30 seconds to 2 minutes, the charge amount can be reduced to 10 kV or less, the adhesion of fine powder can be prevented, and the processing efficiency can be increased.

  If neutralization is performed under the above-described neutralization conditions, the inorganic powder is sufficiently neutralized, so it is sufficient to fill the inside of the pipe 2 that is the neutralization section with an inert gas, and the inside of the mixing tank is made an inert gas atmosphere. There is also an advantage that it is not necessary. In the present invention, the charge amount after neutralization of the charged powder can be set to 0 kV by increasing the processing time. However, in order to reduce the production efficiency, a predetermined amount is considered in consideration of the discharge generation potential of the charged powder. What is necessary is just to neutralize so that it may become charge amount.

  By neutralizing the charged powder by the above-mentioned static elimination method, even if it is a bulky powder of fine particles, the entire treated powder charged in the mixing tank is removed because it is statically eliminated in a fluidized state where it falls freely in the pipe. The charge can be removed uniformly. In addition, since the charged powder is in a fluidized state by freely dropping the charged powder from the powder supply unit, it is not necessary to separately provide a processing facility, and continuous charge removal is possible. Further, since neutralization is performed by supplying an ionized inert gas, neutralization of charges is fast, and sufficient neutralization can be performed even in a short-time treatment in which free fall in the piping.

(Embodiment 2)
In the present invention, it is also a preferred embodiment that the powder that has been neutralized before being supplied to the mixing tank in the first embodiment is temporarily retained, and then further neutralized with an ionized inert gas.

  If you want to further reduce the amount of charge, or if you want to remove a large amount of charged powder, not only supply the inert gas ionized in the flow state due to free fall, but also before removing the discharged powder into the mixing tank It is preferable to remove static electricity.

  FIG. 2 is a schematic configuration diagram showing an example of the processing apparatus of the present embodiment, so that the powder falling on the end of the pipe 2 on the mixing tank 3 side can be temporarily held before being supplied to the mixing tank 3. It is the same as that of Embodiment 1 except having become. For this reason, description is abbreviate | omitted about the same part as Embodiment 1, and the static elimination process in the edge part of the piping 2 is described below.

  As shown in FIG. 2, the charged powder 1 that is transported from the powder supply unit to the pipe 2 and freely falls and is in a fluid state is discharged to a certain charge amount by the ionized inert gas 5 from the inert gas supply unit 4. And transported in the piping. The end of the pipe 2 on the side of the mixing tank 3 is closed by a damper 6 so that the conveyed powder is deposited, and an inert gas 5 ionized for a certain period of time is supplied to the deposited powder. It can be done. The amount of the charged powder and the flow rate of the ionized inert gas 5 in this embodiment can be the same as those in the first embodiment, and the supply time to the powder deposited at the end of the pipe 2 is 1 It is preferable to set it to -2 minutes. When the charge removal at the end of the pipe 2 is completed, the damper 6 is opened and conveyed to the mixing tank 3. In the present embodiment, the powder can be held at the end of the pipe 2 on the mixing tank 3 side. However, if the structure can supply ionized inert gas, the powder holding section is provided separately from the pipe 2. It can also be provided.

  Moreover, in this Embodiment, it is preferable to divide the supply to the piping 2 of the charged powder 1 into predetermined amount, and to perform by batch processing. Since the amount of deposition at the end of the pipe 2 can be reduced by performing batch processing, the accumulated powder layer can be neutralized in a short time, and the processing efficiency can be improved.

(Embodiment 3)
The present invention is also a preferred embodiment in which the charge amount of the charged powder is measured in advance before the charge removal in the first embodiment, and the charge removal condition is changed according to the measurement result of the charge amount.

  It is preferable to measure the charge amount of the charged powder before the charge removal in advance, so that appropriate charge removal can be performed, so that the processing time can be shortened and the charge to the reverse polarity can be prevented.

  FIG. 3 is a schematic configuration diagram illustrating an example of the processing apparatus according to the present embodiment. A measurement unit 7 that measures the charge amount of the charged powder 1 is disposed above the pipe 2 and is in the measurement unit 7. The same as the first embodiment except that the potential of the charged powder 1 can be measured. For this reason, the description of the same parts as those in the first embodiment is omitted, and the processing in the measurement unit 7 will be described below.

  The measurement unit 7 is connected to a charge amount measuring device 8 such as an electrostatic sensor so that the charge amount and polarity of the charged powder 1 in the measurement unit 7 can be detected. When measuring the charge amount of the powder using such a measuring device, for example, the terminal of the charge amount measuring device 8 is installed on the inner wall surface of the measuring unit 7, and the charge amount of the charged powder falling by the terminal is measured. can do.

  In the present embodiment, the static elimination conditions such as the flow rate of the inert gas 5 ionized, the supply amount of powder, and the contact time are controlled based on the charge amount measured above. For example, the charge amount of the powder is detected as a potential, and the detection result is converted into an analog signal, which is fed back to the opening of the gas flow valve of the inert gas supply unit 4 to charge the discharged powder. There is a method of controlling the gas flow rate from the inert gas supply unit 4 into the pipe 2 so that the amount falls within a predetermined range.

(Embodiment 4)
In each of the embodiments described above, the case where the flow state of the charged powder is formed by the free fall of the powder has been described. However, the present invention is directed to the flow state of the charged powder by conveying the charged powder with an ionized inert gas. It is also a preferable form to form a static electricity.

  If you want to reduce the charge amount of a charged powder with a large amount of charge or the charge removal, and if the contact time between the charged powder and the ionized inert gas cannot be secured sufficiently by free fall of the powder, It is preferable to use an ionized inert gas because efficient charge removal can be performed. In addition, in the case of a charged fine particle powder, since the powder is in a floating state by being conveyed in a gas, the entire treated powder can be neutralized efficiently.

  FIG. 4 is a schematic configuration diagram illustrating an example of the processing apparatus according to the present embodiment. The processing apparatus is disposed in the explosion-proof area in the state of being electrically grounded as in the other embodiments, and the pipe 2 has an inert gas supply unit 4 of the inert gas 5 whose one end is ionized. The other end is connected to the vacuum pump 9, and the gas flowing in from the inert gas supply unit 4 is sucked by the vacuum pump 9 so that a gas flow path can be formed inside the pipe 2. Then, the charged powder 1 put into the pipe from the hopper 10 which is a powder supply unit is conveyed to the vacuum pump 9 side by the ionized inert gas 5 flowing in the pipe 2 and is transferred from the powder supply port to the discharge port. A flow state is formed that travels in one direction. Since the charged powder 1 flowing in the pipe 2 during the conveyance comes into contact with the ionized inert gas 5, the entire treated powder can be discharged efficiently and continuously.

  A separation part 11 made of a screen of a predetermined size or the like is formed at the pipe end on the vacuum pump 9 side, and the powder conveyed by the ionized inert gas 5 is separated into gas and powder by the separation part 11. It can be separated. And the isolate | separated powder is thrown in in the mixing tank 3 installed below.

  In the present embodiment, when the charged powder is a fine inorganic powder such as silica powder, the amount of the inorganic powder supplied into the pipe and the flow rate of the ionized inert gas are in the same range as in the first embodiment. However, it is preferable that the amount of powder for conveyance is 3 to 6 kg / min and the gas flow rate is 100 to 200 L / min.

(Other embodiments)
Each of the embodiments described above is an example, and the present invention may be combined with each of the embodiments not described in the above embodiments. Further, in each of the above embodiments, the neutralization unit uses the inside of the pipe in which the flow state of the charged powder traveling in one direction is formed in the processing apparatus in which the powder supply unit and the mixing tank are continuously connected by the pipe as the static elimination unit. However, the present invention is not limited to this. In other words, in a manufacturing process that does not require a continuous process, the charge removal process is an independent process, and after performing the charge removal process, the powder can be transferred to another process. It is also possible to remove the charge by supplying an ionized inert gas. It should be noted that the specific shape and mounting position of each device can be appropriately changed according to the manufacturing process used. For example, in each of the above embodiments, a straight pipe is used. However, the present invention is not necessarily limited to this as long as the charged powder can be transported and the charge removal process can be performed, and may have a curved shape.

  Using the treatment apparatus of the first embodiment, the charge removal treatment of the silica powder (particle size: 1 μm) was performed under the conditions shown in Table 1. The amount of charge of the silica powder before static elimination was 40 kV as measured by a static electricity measuring device (KSD-0103, manufactured by Kasuga Electric Co., Ltd.) installed in the pipe on the powder supply port side.

  From a raw material tank, 50 kg of silica powder was continuously charged into a resin pipe (diameter: 80 mmφ, length: 8 m). To supply the ionized inert gas, nitrogen gas is supplied to the static eliminator, the inert gas passing through the AC high-voltage amplifier is ionized, and then this gas is supplied into the pipe by a fan and transported by free fall. The silica powder was neutralized, and the silica powder was filled in a mixing tank disposed below the pipe. In order to evaluate the difference in charge removal depending on each condition, the charge amount of the silica powder filled in the mixing tank and the weighing error of the filling amount with respect to the charged amount were measured. For comparison, a case where neutralization is performed by supplying non-ionized nitrogen gas and a case where charging is performed without performing neutralization are shown together.

  As shown in Table 1, the amount of silica powder is 3 to 6 kg / min, the gas flow rate is 30 to 200 L / min, and the charge is measured in the range of contact time 1 to 2 min. It can be seen that the error can be within 3% and the adhesion in the piping is reduced. Moreover, the charge amount after static elimination is 10 kV or less, and it can be seen that it is possible to eliminate static electricity even with no discharge.

  Using the treatment apparatus of the second embodiment, an inert gas obtained by ionizing nitrogen gas is supplied to the silica powder charged in the pipe under the same static elimination conditions as in Experiment 1 with the damper at the pipe end closed. Then, the charge was removed, and the gas was discharged by continuously supplying gas to the deposited silica powder layer for 1 minute. As a result, the charge amount of the silica powder filled in the mixing tank was 0 kV, and the measurement error was within 1%.

  Using the processing apparatus of the fourth embodiment, silica powder is introduced into a pipe (diameter: 80 mmφ, length: 8 m) at 6 kg / min, and an inert gas obtained by ionizing nitrogen gas is supplied at a gas flow rate of 200 L / min. The silica powder was discharged in the same manner as in Experiment 1 with a contact time of 1 minute while suctioning the inside of the pipe with a vacuum pump. As a result, the charge amount of the silica powder filled in the mixing tank was 7 kV, and the measurement error was within 1%.

It is a schematic block diagram which shows the processing apparatus of Embodiment 1 of this invention. It is a schematic block diagram which shows the processing apparatus of Embodiment 2 of this invention. It is a schematic block diagram which shows the processing apparatus of Embodiment 3 of this invention. It is a schematic block diagram which shows the processing apparatus of Embodiment 4 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Charged powder 2 Piping 3 Mixing tank 4 Inert gas supply part 5 Ionized inert gas 7 Measuring part

Claims (4)

  A method for neutralizing a charged powder, wherein the charge is removed by supplying an ionized inert gas to the charged powder in a fluidized state.   The charge eliminating method according to claim 1, wherein the charged powder in the fluidized state is due to free fall of the powder.   The charge eliminating method according to claim 1, wherein the charged powder in the fluidized state is obtained by using the ionized inert gas as a powder carrier gas.   The charged powder is an inorganic powder, and a fluidized state is formed while supplying the inorganic powder at 2 to 6 kg / min, and the ionized inert gas is added to the fluidized inorganic powder in an amount of 30 to 300 L. The static elimination method of any one of Claims 1-3 which performs static elimination by contacting the said inorganic powder with the said ionized inert gas for 30 second-2 minutes, supplying at / min.

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