JP4196222B2 - Cleaning device for membrane separator for ultrapure water production - Google Patents

Description

  The present invention relates to a cleaning apparatus for a membrane separation apparatus for producing ultrapure water. More specifically, the present invention effectively prevents amine elution into ultrapure water used in manufacturing plants such as silicon wafers and system LSIs, and stably supplies ultrapure water with extremely high purity. The present invention relates to a cleaning device for an ultrapure water production membrane separator.

In the manufacture of electronic parts such as semiconductors and liquid crystals, a large amount of pure water or ultrapure water is used. Ultrapure water has a specific resistance value very close to the specific resistance of theoretical pure water of 18.24 MΩ · cm at 25 ° C. FIG. 1 is a system diagram of an example of an ultrapure water supply apparatus. In the ultrapure water supply apparatus, city water, industrial water, well water, and the like are used as raw water and processed by a pretreatment apparatus, a primary pure water apparatus, and a secondary pure water apparatus to produce ultrapure water. In the pretreatment device, pretreatment by filtration, coagulation sedimentation, microfiltration membrane or the like is performed. In the primary pure water device, ion exchange, membrane separation, gas diffusion, ultraviolet irradiation, and the like are performed, and each device is appropriately combined according to the quality of raw water and the required quality of treated water. Secondary pure water equipment consists of pure water tanks, pumps, heat exchangers, UV oxidation equipment, ion exchange polishers, ultrafiltration membrane equipment, etc., and trace amounts of ions, silica, organic matter remaining in primary pure water, Fine particles are removed to obtain ultrapure water. A porous ion exchange membrane device may be used as the ion exchange polisher, and a microfiltration membrane or a reverse osmosis membrane may be used instead of the ultrafiltration membrane. Further, membrane deaeration is performed before the ultrafiltration membrane. May include device. The manufactured ultrapure water is sent to a use point such as a cleaning process for electronic parts and used. At the point of use, concentrated drainage, diluted drainage, and pure water that has not been used are generated. Concentrated wastewater is drained and then discharged or recovered and reused in a wastewater treatment system. The diluted waste water is processed by the waste water recovery device, and the pure water is processed by the pure water recovery device, and each is supplied to the primary pure water device and reused.
Using such an ultrapure water supply device, organic carbon, inorganic salts, bacteria, and dissolved gas are removed as much as possible, and in terms of theoretical water quality, ultrapure water has almost reached a satisfactory level. However, at the system LSI manufacturing factory, after replacing the ultrafiltration membrane of the secondary pure water device, the oxide film has poor pressure resistance and the silicon surface is damaged, and the product is in a defective state for one week to one month. There was a problem of doing. The oxide film was also thick. The ultrafiltration membrane is manufactured by the manufacturer, washed with ultrapure water for product inspection, and the permeated water quality is confirmed to be TOC elution 20 μg / L or less and resistivity 17.5 MΩ · cm. Shipped and delivered to electronics industry factories. Therefore, the guaranteed water quality of ultrapure water is satisfactory, but the problem is that the required quality of the product has increased, and that the substance that causes some trouble is eluted from the ultrafiltration membrane. Estimated.
When the present inventors diligently examined the cause, it was concluded that the amine in the ultrapure water was a causative substance of the product defect. In addition, when the source was identified, potting materials such as microfiltration membranes, ultrafiltration membranes, reverse osmosis membranes, porous ion exchange membranes, deaeration membranes used in primary and secondary pure water devices, It was found that the amine was eluted from the adhesive. For this reason, it has become an urgent issue to reduce elution of amines separately from inorganic ions that have been attracting attention as impurities in ultrapure water.
Japanese Patent Laid-Open No. 7-80260 JP-A-4-305231

  INDUSTRIAL APPLICABILITY The present invention can effectively prevent amine elution into ultrapure water used in manufacturing plants such as silicon wafers and system LSIs, and can stably supply ultrapure water with extremely high purity. The object of the present invention is to provide a cleaning device for a membrane separation device for producing ultrapure water.

As a result of intensive studies to solve the above problems, the present inventors have used ultrapure water with extremely high purity before attaching the membrane separation apparatus for producing ultrapure water to the secondary pure water apparatus. Even if a new ultrapure water production device is installed or a membrane separation device is replaced by repeating a washing cycle comprising a water flow step, a dipping step, and a discharge step for the membrane separation device, It has been found that there is no elution of amine and the occurrence of defective products can be prevented, and the present invention has been completed based on this finding.
That is, the present invention
(1) A washing water supply pipe having a detachable connecting portion with a water supply inlet of the membrane separation device, a permeated water outlet piping having a permeable water outlet and a detachable connecting portion, a concentrated water outlet of the membrane separation device, Concentrated water discharge pipe having a detachable connecting part, a cleaning water supply pipe is provided with a valve and a flow rate adjusting means, a permeate water discharge pipe is provided with a valve, and a concentrated water discharge pipe is provided with a cleaning water supply. A cleaning device for a membrane separator for ultrapure water production, characterized in that a blow water piping having a valve branched to the piping is connected,
(2) A cleaning device for a membrane separator for ultrapure water production according to item 1, wherein a gas supply pipe having a valve is connected to the concentrated water discharge pipe, and
(3) A cleaning device for a membrane separator for ultrapure water production according to item 1, wherein a plurality of membrane separators for ultrapure water production are attached in parallel,
Is to provide.

  According to the cleaning apparatus for a membrane separator for ultrapure water production of the present invention, the elution of amine from the membrane separator installed in the secondary pure water apparatus of the ultrapure water production apparatus is prevented, immediately after the installation of a new membrane separator. Therefore, it is possible to produce ultrapure water with good water quality and prevent the generation of defective products in the electronic material factory.

In the method for cleaning a membrane separation apparatus for producing ultrapure water of the present invention, the number of fine particles having a particle size of 0.05 μm or more is 1 / mL or less, the TOC (organic carbon) concentration is 2 μgC / L or less, and the resistivity is 18 .2 MΩ · cm or more of ultrapure water is used as washing water, and the washing water is passed through a membrane separation device for producing ultrapure water, and the passage of water is stopped while the membrane separation device holds the washing water. The cleaning cycle including the immersion step and the discharge step of discharging the cleaning water from the membrane separation apparatus is repeated.
The number of fine particles with a particle size of 0.05 μm or more is used in the ultra-pure water used in the electronics industry, especially in the production of high-precision electronic materials such as silicon wafers and system LSIs such as highly integrated products such as flash memory. Is 1 piece / mL or less, the TOC concentration is 2 μgC / L or less, and the resistivity is 18.2 MΩ · cm or more. Wash the membrane separator for ultrapure water production with the same quality cleaning water as the ultrapure water used, and when the permeated water quality of the membrane separator is the same as the quality of the washing water, wash the membrane separator. Therefore, it is possible to guarantee that the ultrapure water produced satisfies the required water quality standard by installing the membrane separation device in the secondary pure water device of the ultrapure water production device.

In the method of the present invention, the amine concentration of the washing water is preferably 50 ng / L or less, and more preferably 20 ng / L or less. The ultrapure water used in a high-precision electronic material manufacturing factory is required to have an amine concentration of 20 ng / L or less. The amine contained in the ultrapure water is mainly a long-chain amine having 10 to 30 carbon atoms used as a curing agent for an epoxy resin that is a potting material, a hydrophilic heterocyclic diamine, or the like. The amine is eluted from the membrane separator by bringing the membrane separator into contact with the washing water, but the elution of the amine is almost independent of the amine concentration in the washing water, and the contact time between the washing water and the membrane separator. In response, the amine migrates from the membrane separator to water. The amine that has migrated to water will not migrate again to the membrane separator. Therefore, even if ultrapure water having an amine concentration of 50 ng / L is used as the washing water, the elution of amine from the membrane separation device into water proceeds. And even if some washing water containing amine remains in the membrane separation device after the washing is finished, if this washed membrane separation device is installed in the secondary pure water device to produce ultrapure water, the remaining washing water is Ultra-pure water having an amine concentration below a predetermined value is produced after being eliminated in a short time.
The amine concentration in the washing water is preferably very low, and ultrapure water obtained by an ultrapure water production apparatus equipped with a membrane separation apparatus for producing ultrapure water washed by the washing method of the present invention is used. More preferably. That is, it is preferable to clean using ultrapure water having a high purity that does not adversely affect the production of products such as silicon wafers, and the quality of the ultrapure water varies depending on the quality required for the product. However, the amine concentration is more preferably 20 ng / L or less.

In the method of the present invention, the amount of water flow in the water flow step is preferably the design maximum flow rate of the membrane separation device. FIG. 2 is an explanatory diagram of an example of a membrane separation apparatus. The membrane separation device in this figure is a hollow fiber module, in which hollow fibers 1 made of ultrafiltration membranes are bundled and stored in a pressure vessel 2, and both ends of the hollow fibers are fixed at an adhesive portion 3 by an epoxy resin. Yes. Washing water is supplied from the lower part of the module and flows outside the hollow fiber. The permeated water that has permeated the membrane and entered the inside of the hollow fiber is taken out through the hollow fiber. The water that has not permeated the membrane is discharged from the concentrated water outlet 4 as concentrated water.
In such a membrane separation device, water easily flows on the permeate side, but water hardly flows on the supply water side, and drift tends to occur. By making the amount of water flow the design maximum flow rate of the membrane separation device, it is possible to prevent the occurrence of uneven flow and allow water to flow uniformly into the membrane separation device. Further, in the vicinity of the adhesion portion of the membrane separation apparatus, the hollow fibers are densely gathered and water does not flow easily, so that a pool is easily generated. By repeating the water flow, immersion and discharge to the membrane separation device, it is possible to prevent water from being accumulated in the vicinity of the bonding portion. Not only in hollow fiber modules, but also in flat membrane modules, tube modules, spiral modules, monolith modules, etc., problems of drift and accumulation occur, but by making the amount of water flow the design maximum flow rate of the membrane separator, Can be solved.

In the method of the present invention, the water passing time in the water passing step is preferably 1 to 10 minutes, and more preferably 2 to 5 minutes. The water flow time is the time from when the inside of the membrane separation device is completely filled with water until the water flow is stopped. In the water passing step, it is preferable to pass water until the permeated water has a resistivity of 18.0 MΩ · cm or more. In a 6-inch hollow fiber module, the permeate resistivity typically reaches 18.0 MΩ · cm in 2 to 5 minutes.
In the method of the present invention, the temperature of the washing water is preferably 23 to 50 ° C, and more preferably 25 to 40 ° C. When the temperature of the washing water is less than 23 ° C., the elution rate of the amine is slow and there is a possibility that a long time is required for washing. When the temperature of the washing water exceeds 50 ° C., the separation membrane may be deteriorated.
In the method of the present invention, after the water flow process is completed, the process proceeds to an immersion process in which the water flow is stopped while the cleaning water is retained in the membrane separation device. In the dipping process, water-soluble components such as amines are eluted from the membrane separator into the washing water. The immersion time in the immersion process is preferably 0.5 to 6 hours, and more preferably 2 to 4 hours. If the immersion time is less than 0.5 hours, the washing water retained before the water-soluble components are sufficiently eluted may be discharged, and the washing water may be consumed wastefully. When the immersion time exceeds 6 hours, the water-soluble component of the membrane separation device and the eluted water-soluble component approach the equilibrium, and the elution rate of the water-soluble component may be reduced.

In the method of the present invention, when the predetermined immersion process is completed, the process proceeds to a discharge process for discharging the washing water from the membrane separation device. In the discharge process, all the water on the concentrated water side of the membrane separation device is discharged, so that, for example, all washing water in the portion where water is likely to accumulate, such as the bonded portion of the hollow fiber module, is also discharged. Since the cleaning water can be refilled in the process, the cleaning water can be effectively washed in a shorter time by using a smaller amount of the washing water than when the washing water is continuously passed and washed. Can do. In the discharging step, it is preferable to discharge the washing water held by sending gas into the concentrated water side of the membrane separation apparatus.
The gas to be fed is preferably nitrogen having a purity of 99.999% by volume or more, or air filtered with a filter of HEPA (High Efficiency Particulate Air) or more. Contamination of the membrane separator and mixing of fine particles can be prevented by sending air filtered through a filter having a purity of 99.999% or more by nitrogen or a HEPA filter or more. The HEPA filter is a filter that collects 0.3 μm particles at 99.97% or more at a rated air volume with a pressure loss of 25 mmH ₂ O or less. Examples of the filter that exceeds the HEPA filter include a ULPA (Ultra Low Penetration Air) filter that collects 0.1 μm particles at a rate of 25 mmH ₂ O or less at a rated air volume at 99.9995% or more. .
The pressure of the gas to be fed is preferably 5 to 20 kPa, and more preferably 8 to 15 kPa. If the pressure of the gas to be fed is less than 5 kPa, it may take a long time to discharge the cleaning water. If the pressure of the gas to be fed exceeds 20 kPa, the separation membrane may be damaged. In the method of the present invention, it is preferable to transfer the gas to the concentrated water side of the membrane separator and leave it for 10 to 30 minutes, and then shift to the water flow step. By feeding the gas and leaving it for 10 to 30 minutes, the washing water inside the membrane separation apparatus can be completely discharged, and the washing efficiency can be improved.

In the method of the present invention, the washing cycle is preferably repeated for 10 to 60 days. By repeating the washing cycle for 10 to 60 days, the washing of the membrane separator can usually be completed. When the quality of the ultrapure water used as the washing water and the quality of the permeated water of the membrane separation device are the same, it can be determined that the washing has been completed, or the ultrapure water obtained by the membrane separation device If the silicon wafer is cleaned using, and the surface of the silicon wafer is not damaged, it can be determined that the cleaning is completed. In this case, confirmation is performed using SEM observation of the wafer, an ellipsometer, or the like. Furthermore, if the cleaning is repeated using a specific apparatus and the cleaning time until the end of the cleaning can be grasped empirically, the cleaning can be completed after a predetermined time of cleaning.
In the method of the present invention, washing wastewater generated by washing the membrane separator, that is, permeated water that has permeated through the membrane of the membrane separator, concentrated water that does not permeate the membrane and is generated from the concentration side, Since it has almost the same quality as ultrapure water, it can be recovered and returned to the primary deionizer of the ultrapure water production system to make it the raw water for ultrapure water production, or any factory that does not require factory purity It can also be used for other applications.

The cleaning apparatus for a membrane separation apparatus for producing ultrapure water according to the present invention has a cleaning water supply pipe having a connection part that can be detached from a water supply inlet of the membrane separation apparatus, and a connection part that can be detached from a permeate outlet of the membrane separation apparatus. It has a permeate discharge pipe, a concentrate outlet of the membrane separator and a concentrate discharge pipe having a detachable connection part, a valve and flow rate adjusting means in the washing water supply pipe, and a valve in the permeate discharge pipe. Each of the water discharge pipes is provided with a valve, and a blow water pipe having a valve branched to the cleaning water supply pipe is connected thereto. The apparatus of the present invention is preferably an apparatus in which a gas supply pipe having a valve is connected to a concentrated water discharge pipe. The apparatus of the present invention is preferably an apparatus to which a plurality of membrane separation apparatuses for producing ultrapure water are attached in parallel.
FIG. 3 is a process flow diagram of one aspect of the apparatus of the present invention. The apparatus shown in this figure can be equipped with 5 membrane separators for production of ultrapure water in one line and is equipped with 3 lines, so that a total of 15 membrane separators can be attached and cleaned simultaneously. it can. In the figure, for the sake of simplification, only one series of five membrane separators is shown, and the other two series are indicated by a dashed-dotted rectangle. The apparatus of the embodiment shown in FIG. 3 has a wash water supply pipe T having a connection part C that can be attached and detached with a feed water inlet of the membrane separation apparatus M, and a permeate discharge having a connection part D that can be attached and detached with a permeate outlet of the membrane separation apparatus. Concentrated water discharge pipe R having a pipe Q, a concentrated water outlet of the membrane separator and a detachable connecting portion E is provided. The washing water supply pipe T is provided with a sub pipe S provided with a flow meter F, a valve A1, and a valve A2 as a flow rate adjusting means. The permeated water discharge pipe Q is provided with a valve A5, and the concentrated water discharge pipe R is provided with a valve A4. Branching to the cleaning water supply pipe T, a blow water pipe B having a valve A6 and a valve A7 is connected. A gas supply pipe G having a valve A3 is connected to the concentrated water discharge pipe R. Furthermore, a valve Umn1 is provided upstream of the feed inlet of the membrane separator M and the detachable connecting portion C, a valve Umn2 is provided downstream of the permeate outlet of the membrane separator and the detachable connecting portion D, and a concentrated water outlet of the membrane separator. A valve Umn3 is provided after the detachable connecting portion E. However, m is a series number and n is a membrane separator number. Each valve is an automatic valve and can be opened and closed automatically. The flow rate can be adjusted with a separate manual valve as necessary.

In the apparatus of the present invention, the number of series can be one series or a plurality of series. Also, the number of membrane separation devices attached in one line is arbitrary, and can be one or plural. The number of membrane separation apparatuses to be washed can be appropriately selected according to the scale of the ultrapure water production apparatus. For example, when the amount of treated water of one membrane separation device installed in the secondary pure water device is 10 t / h and the production amount of ultrapure water is 150 t / h, at least 15 membrane separation devices are required. Become. In the case of such a scale, it is preferable that 15 membrane separation devices are also attached to the cleaning device. In addition, when the production amount of ultrapure water is extremely small, it is sufficient that a single membrane separation device is attached. Usually, however, a plurality of membrane separation devices are required. Preferably a separation device can be attached.
When washing, connect the water inlet, permeate outlet, and concentrated water outlet of the membrane separator to the washing water supply pipe, permeate drain pipe, and concentrated water outlet pipe, respectively, to wash the membrane separator. Attach to the device. When cleaning a plurality of membrane separation devices, a plurality of membrane separation devices are attached. For example, in FIG. 3, when cleaning 15 membrane separators, the membrane separators are attached to all three systems, and when cleaning 5 membrane separators, the membrane separators are attached to only one system, When washing three membrane separation devices, three membrane separation devices are attached in one line, and all valves of the system not attached with the membrane separation device are closed and removed from the target of automatic valve control. be able to.

At the start of the water flow process, the valves A3, A6 and A7 are closed and all other valves are opened. Wash water is supplied through the valve A1, is attached, and the inside of the membrane separator and each pipe are filled with water. The time required to make the water full is governed by the amount of supplied water, but is preferably about 1 minute.
In the water flow process, first, the valves U111, U112, U113, A1, A5, and A4 are opened, all other valves are closed, and only the membrane separation device M1 is passed. At this time, in order to prevent uneven flow in the membrane separation apparatus, it is preferable that the valve A2 of the sub-pipe S is also opened to increase the amount of supplied water and set the water flow rate to the design maximum flow rate of the membrane separation apparatus. By passing water, the water in the membrane separator is replaced, and the water-soluble components eluted from the membrane separator are washed out. The amount of water flow may be about 10 to 30 times the amount of water in the membrane separator, and the water flow time is preferably 1 to 10 minutes, more preferably 2 to 5 minutes.
After passing water through the membrane separator M1 for a predetermined time, the valves U111, U112, and U113 are closed to stop water passing through the membrane separator M1, and the inside of the membrane separator is filled with washing water. The inside of the apparatus is immersed in cleaning water. The immersion state is preferably maintained for 0.5 to 6 hours. During this time, the valves U121, U122 and U123 are opened, and the second membrane separation device M2 is transferred to the water passing step. When the water flow process of the membrane separation device M2 is completed, the process proceeds to the crushing process. In this way, each membrane separator sequentially moves to the immersion process through the water flow process. In the dipping process, the cleaning water and the membrane and the connecting portion of the membrane are in contact with each other for a long time in each membrane separation device, and the elution of the water-soluble component from the connecting portion into the cleaning water gradually proceeds.

In the discharge step, the valves A3, Umn3, Umn1, A6, and A7 are opened and the valves A1, A2, U112, and A4 are closed, whereby the washing water in the membrane separation device M1 flows down and is discharged. At this time, clean gas is fed into the membrane separation device from the concentrated water outlet through the valve A3, and the washing water in the membrane separation device is completely discharged by pushing out the washing water in the membrane separation device. . The gas supply pressure is preferably 5 to 20 kPa. In the discharging step, the time required for discharging the washing water is usually 2 to 4 minutes, but it is preferable to leave the water for 10 to 30 minutes to discharge the water reliably.
In the apparatus of the present invention, the water separation process can be carried out by sequentially passing water through each membrane separation device, and water can be passed through all of the attached membrane separation devices at the same time, or a plurality of, if not all, can be passed. It is also possible to simultaneously pass water through the membrane separation apparatus. However, if water is passed through each membrane separation device in the water flow process, the required washing water supply capacity is only one membrane separation device, so that the washing water supply facility can be a small device. If water is passed through five membrane separators at the same time, the washing water supply capacity is required five times.
In the embodiment shown in FIG. 3, the cleaning apparatus is composed of three systems with five membrane separators as one system, but the number of membrane separators attached to one system and the number of systems of cleaning systems are as required. It can be increased or decreased. It is preferable that the automatic valve of the cleaning apparatus is sequence-controlled and automatically shifts the water flow process, the immersion process, and the discharge process sequentially.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the examples, amine analysis was performed by chromatographic column concentration-TD-GCMS.
Example 1
The ultrafiltration membrane device [Kurita Industry Co., Ltd., KU-1510HS] was washed. This ultrafiltration membrane device is a hollow fiber module having a diameter of 176 mm and a length of 1,284 mm, the membrane material is polysulfone, and the permeation flow rate is 15 t / h.
As washing water, ultrapure water having a particle size of 0.3 μm / mL, particle size of 0.05 μm or more, TOC concentration of 1 μg C / L, resistivity of 18.24 MΩ · cm, hexadecylamine 20 ng / L, and water temperature of 30 ° C. is used. It was. For discharging the washing water, air having a pressure of 10 kPa filtered through a HEPA filter was used.
Washing was performed with a water passage time of 4 minutes, an immersion time of 3.5 hours, a discharge time of 3 minutes, a standing time after discharge of 23 minutes, and a cleaning cycle of 4 hours. The concentration of hexadecylamine in the permeated water immediately after the start of washing was 47 μg / L. As the washing cycle was repeated, the hexadecylamine concentration of the permeated water gradually decreased, and after 30 days, when 180 cycles were completed, the concentration was 20 ng / L, which was the same as that of the washing water, and the completion of washing was confirmed.
FIG. 4 shows the relationship between the elapsed days and the hexadecylamine concentration of the permeated water.

  According to the cleaning apparatus for a membrane separator for ultrapure water production of the present invention, the elution of amine from the membrane separator installed in the secondary pure water apparatus of the ultrapure water production apparatus is prevented, immediately after the installation of a new membrane separator. Therefore, it is possible to produce ultrapure water with good water quality and to prevent the occurrence of defective products in an electronic material factory.

FIG. 1 is a system diagram of an example of an ultrapure water supply apparatus. FIG. 2 is an explanatory diagram of an example of a membrane separation apparatus. FIG. 3 is a process flow diagram of one aspect of the apparatus of the present invention. FIG. 4 is a graph showing the relationship between the number of days elapsed and the hexadecylamine concentration of permeated water.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hollow fiber 2 Pressure vessel 3 Bonding part 4 Concentrated water outlet A Valve B Blow water piping C Connection part D Connection part E Connection part F Flow meter G Gas supply pipe M Membrane separation device Q Permeate discharge pipe R Concentrated water discharge pipe S Sub piping T Cleaning water supply piping U valve

Claims (3)

  Washing water supply pipe having a detachable connecting part with a water supply inlet of the membrane separation apparatus, a permeated water discharging pipe having a detachable connecting part with a permeated water outlet of the membrane separation apparatus, and a detachable connection with the concentrated water outlet of the membrane separation apparatus Concentrated water discharge pipe with a connecting part, a valve and flow rate adjusting means are provided in the washing water supply pipe, a valve is provided in the permeated water discharge pipe, a valve is provided in the concentrated water discharge pipe, and the branch to the washing water supply pipe An apparatus for cleaning a membrane separation apparatus for producing ultrapure water, wherein a blow water pipe having a valve is connected.   The apparatus for cleaning a membrane separator for ultrapure water production according to claim 1, wherein a gas supply pipe having a valve is connected to the concentrated water discharge pipe.   The cleaning apparatus for a membrane separator for ultrapure water production according to claim 1, wherein a plurality of membrane separators for ultrapure water production are attached in parallel.

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