JPH07213880A - Tubular membrane - Google Patents

Abstract

PURPOSE:To prepare a tubular membrane used to dissolve ozone in a liquid by extruding polytetrafluoroethylene (PTFE) into a tube, stretching the tube to obtain a porous tube, and laminating a porous film obtd. by stretching a PTFE sheet around the outer surface of the tube. CONSTITUTION:This tubular membrane is used to an ozone-dissolving module to dissolve ozone in a liquid to be processed by bringing ozone into contact with the liquid to be processed through a porous PTFE tubular membrane. The tubular membrane consists of a porous tube 1 and a porous film 2. The tube 1 is obtd. by extruding PTFE into a tube and stretching the tube. The film 2 is obtd. by stretching PTFE laminated on the porous tube 1. With the obtd. tubular membrane, ozone can be efficiently dissolved in a liquid with a specified concn. without causing loss or flowing of ozone to the outside, so that problems concerning to influence on a human body are avoided. Further, ozone gas can easily be dissolved in water to obtain the max. 16ppm, and normally 12ppm concn.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a tubular membrane for dissolving ozone in a liquid.

[0002]

2. Description of the Related Art Conventionally, ozone gas has been known to have activity as ozone such as sterilization, deodorization, and promotion of oxidation, but it is actually used as a by-product in the industrial field, but it is actually directly used. It was never used. Recently, however, ozone has begun to be used in small amounts in the fields of sterilization, deodorization by chlorine and chemical substances, and fields of promoting oxidation.

Specifically, it is used by bubbling ozone gas into the liquid from the tip of the fluororesin tube to dissolve ozone in the liquid. In addition, Japanese Patent Laid-Open No. 3-18
No. 8988 publication, polytetrafluoroethylene (hereinafter,
It is called PTFE. It is described that the porous tube obtained by stretching the extruded tube of 1) is used as a film of an ozone dissolution module.

[0004]

However, in the method using the fluororesin tube described above, the amount of ozone dissolved in the liquid relative to the ozone supply amount when the ozone gas is dissolved in the liquid is small, and the efficiency is very poor. When dissolved in a liquid, there are inconveniences such as ozone gas flowing out to the surroundings to oxidize the substance, harm to human health, and the amount of dissolved ozone in the liquid cannot be made constant. Therefore, the ozone activity could not be effectively utilized industrially by such a method.

The above-mentioned problem is decisively caused by the inability to stably dissolve ozone with a constant dissolution amount under a constant condition. However, as described in JP-A-3-188988, the problem of PTFE When a porous tube obtained by drawing an extruded tube is used as a film of an ozone dissolution module, these are solved to some extent, and the ozone dissolution module has a possibility of being industrially used. However, the pore size of the porous body is not uniform and the amount of permeation of ozone cannot be made constant, and the pressure resistance and compression resistance are inferior, that is, the liquid to be treated is inside the tube and ozone is outside the tube. In this case, since the tube is uniaxially stretched, the pressure resistance is insufficient, and the tube is torn in the length direction, and when ozone is present inside the tube and the liquid to be treated is present outside the tube, the compression resistance is low. The tube is crushed due to lack, JP-A-3-188988 describes that impurities can be removed, but the removal of impurities in ozone is not sufficient due to variations in the pore diameter of the porous body, etc. There was a problem.

[0006]

SUMMARY OF THE INVENTION The present invention has been made for the purpose of solving the above-mentioned problems of the prior art. A tube constituted only by an extruded tube has the above-mentioned problems, but the PTFE It was found that these problems can be solved by using a porous film obtained by stretching a sheet as a part or the whole of a tube material.

That is, the present invention relates to a tubular film used in an ozone dissolution module for bringing ozone and a liquid to be treated into contact with each other through a tubular film of porous PTFE to dissolve ozone in the liquid to be treated. , The tubular membrane is
A porous tube obtained by stretching an extruded PTFE tube, and laminated on the outer periphery of the porous tube,
A porous film obtained by stretching a PTFE sheet, or a porous film obtained by stretching a PTFE sheet, for dissolving ozone in a liquid It is in a tubular membrane.

Fluorine resin is currently the only resin having resistance to ozone gas. Since this fluororesin has liquid repellency, by making it porous, it is possible to form a film that is permeable to liquid but not permeable to ozone gas. Therefore, if the liquid to be treated is passed through the porous fluororesin tube and the ozone gas is passed to the outside, or conversely, if the ozone gas is passed through the porous fluororesin tube and the liquid to be treated is passed to the outside, the ozone gas is exposed. It can be dissolved in the processing liquid. According to this method, the contact area between the liquid and the ozone gas expands in accordance with the surface area of the tube, so it is easy to select the shape of the tube itself, the diameter, the length, and the number of the tubes so that the liquid and the ozone gas can be easily contacted. It is possible to increase the contact area with the liquid, and thus it is possible to significantly increase the dissolution efficiency of ozone in the liquid. Further, in this method, the liquid to be treated or the ozone gas can be brought into contact with the ozone gas in a state of being hermetically sealed in the case, therefore, it is possible to prevent the ozone gas from flowing out to the surroundings or causing a loss, In addition, it is possible to prevent health problems to the human body due to ozone gas.

However, as described above, in the tube disclosed in Japanese Unexamined Patent Publication No. 3-188988, only the extruded tube cannot dissolve ozone in a constant amount, and the pressure resistance and compression resistance are inferior. There are problems such as insufficient removal of impurities in ozone. However, the inventors of the present invention have found that these problems are caused by the fact that a tube composed only of an extruded tube has variations in pore size, and a porous film obtained by stretching a PTFE sheet is used as a tube. It has been found that these problems can be solved because the pore size and the like can be controlled as desired when used as a part or all of the material.

The fluororesin which can be used in the present invention includes polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA). ), Tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer (EPE), tetrafluoroethylene-ethylene copolymer (ETF
E), etc. can be used, but from the viewpoint of decomposition of fluororesin by active ozone by long-term or contact with high-concentration ozone, binding force between carbon and fluorine of fluororesin and ozone decomposition power. Most preferred is polytetrafluoroethylene.

The tubular membrane of the present invention is characterized in that a porous film obtained by stretching a PTFE sheet is used as a part or all of the membrane material. A porous body obtained by stretching a molded PTFE product is, for example, Japanese Patent Publication No. 51-1.
It is manufactured by the method described in Japanese Patent Publication No. 8991 and Japanese Patent Publication No. 56-17216. That is, a polytetrafluoroethylene resin having a crystallinity of about 95% or more is mixed with a liquid lubricant, for example, solvent naphtha, hydrocarbon oil such as white oil, petroleum ether, etc. to prepare a preform.
The mixing ratio in this case is, for example, polytetrafluoroethylene.
20 parts by weight of liquid lubricating oil to 80 parts by weight. Next, this preform is extruded from a die into a sheet shape, a tube shape, or the like using an extruder to obtain a molded article. The obtained molded product is stretched at a high speed of 10% or more per second in the unsintered state at 327 ° C. or lower with or without removing the liquid lubricant.
Next, the stretched product is heat-treated at 200 to 390 ° C. in the stretched state to prevent shrinkage and obtain the intended porous body of polytetrafluoroethylene resin. In the above step, in the case of a porous film obtained by stretching a sheet-shaped extrudate, a uniaxially stretched film is obtained by carrying out a stretching operation in one direction, and a biaxially stretched film is obtained by carrying out in a biaxial direction. . The polytetrafluoroethylene resin porous body thus obtained is composed of very fine fibrils called fibrils and granular nodules called nodes connecting them, and these fibrils Micropores exist in a continuous state between each other and the node, forming a so-called continuous porous structure.

The PTFE stretched film thus produced can not only make an extremely thin film, but can also control the porosity arbitrarily so that the pore diameter becomes uniform. Therefore, the ozone permeation amount can be made uniform (the performance of the filter for removing impurities in ozone is also excellent), and the strength can be high and the pressure resistance and compression resistance can be excellent. Note that such characteristics are
Although it can be obtained by uniaxial stretching or biaxial stretching, the biaxially stretched film is superior.

On the other hand, it is difficult to obtain a uniform pore size in a porous tube obtained by uniaxially stretching a tubular extrudate in the above-mentioned porous body manufacturing process. In addition, pressure resistance and compression resistance are also weak. This is because in a uniaxially drawn tube, the draw ratio must be increased in order to increase the porosity, so that a tube that is weak and easily broken without stiffness is created, and increasing the draw ratio changes the pore size. Because. As described above, in the case of an extruded uniaxially drawn tube, the draw ratio and the hole diameter are linked, so that the porosity and the hole diameter cannot be arbitrarily set to make a target tube.

As a concrete embodiment of a tubular membrane using the above-mentioned expanded PTFE porous film as a part or all of the membrane material, a PTFE porous film is wrapped on the outside of a PTFE extruded porous tube. It is preferable that they are fused. Since it may be desirable to accelerate ozone dissolution by bubbling ozone gas into the liquid by increasing the pressure of the ozone gas above that of the liquid or by utilizing the difference in concentration of the ozone gas, the pressure resistance of the tube , To enhance the compression resistance.

To wrap the PTFE porous film on the outside of the PTFE extruded porous tube, pass a suitable core material through the PTFE extruded tube, and then partially overlap the PTFE porous film around it. After lapping in such a manner, the overlapping portion can be joined. Examples of the wrapping method include a spiral winding method, a sushi winding method, and a combination method of these methods. The joining method may be heat fusion or an adhesive. The heat fusion may be performed by heating above the melting point of PTFE. In the case of an adhesive, the adhesive is partially adhered in a dot shape, a linear shape, a grid shape, or the like so as not to lose the ozone gas permeability. The adhesive is preferably a fluororesin-based adhesive such as PFA or FEP.

On the other hand, it is also possible to use only a stretched porous PTFE film and roll it up to form the tubular membrane of the present invention. In other words, use an appropriate core material, and use PTF around it.
The fired stretched porous film of E is wrapped, and the overlapping portion is heat-sealed or adhered to form a tubular film, and then the core material is extracted. Alternatively, an appropriate core material is used, and an unsintered stretched porous film of PTFE is wrapped around the core material and baked at a temperature equal to or higher than the melting point to obtain an integral tubular membrane (the core material is extracted before or after baking. ). As the wrapping method in this case, a spiral, sushi-wrapped, or sushi-wrapped method can be adopted. This tubular membrane is also P
By producing only a stretched porous film of TFE, it is possible to have a uniform pore size and other properties that cannot be obtained with an extruded tube.

When ozone gas is dissolved in a liquid and used in the industrial field, in foods, semiconductors, pure water, tap water, chemicals, special industrial liquids, etc., dust, inorganic substances, organic substances other than ozone gas, etc. Although ozone should not be mixed into the liquid that dissolves it, this object can be easily achieved by providing the PTFE porous tube of the present invention with a function as a filter. With an extrusion-molded porous tube, it is difficult to obtain one having a uniform pore size, and the filter function is not sufficient. The function as a filter has a certain effect even with a uniaxially stretched porous film,
It is desirable to use biaxially expanded porous PTFE that can make the pore diameter of the porous body more completely constant. However, even in the case of a uniaxially stretched film, the filter characteristics can be improved particularly by stacking them on an extruded tube or stacking uniaxially stretched porous bodies.

The thickness, diameter, length and number of the porous PTFE tubular membrane are designed according to the application, but the workability, durability, bending resistance (breakability), pressure resistance, Taking into consideration the pressure resistance of the tube to develop the adhesive force when the wrapping film is fused with the tube due to heat, the thickness of the tubular film is 0.3 to 1 mm, the inner diameter is 0.5 to 8 mm, and the outer diameter is 1 to 10 mm, length is related to the solubility of ozone, but 50
A preferred range is cm to 5 m.

The pore size of the porous PTFE tubular membrane is generally in the range of 0.01 to 5 μm, and the porosity, that is, the porosity is generally in the range of 30 to 95%, but the pore size is set in consideration of the liquid permeation resistance. It is preferably 0.01 to 0.2 μm and the porosity is about 80%. This is because when the porosity is 90% or more, when the tube is fired after lapping, the tube is deformed in the Z direction (thickness direction) to change the pore diameter, and the performance of the filter function is deteriorated.

The porous PTFE tubular film as described above can be used as it is by immersing it in the liquid to be treated and passing ozone gas through the tubular film. Since it impairs the health of the, preferably, a predetermined number of tubular membranes are penetrated in a case that can be sealed, and while the liquid to be treated is passed therein, ozone gas is passed inside the case, that is, outside the tubular membrane, Alternatively, conversely, the ozone gas is allowed to pass through the tubular film while the liquid to be treated can be passed through the outside of the tubular film in the case.

As described above, the case basically needs to be entirely made of fluororesin, but only the portion in contact with ozone may be made of fluororesin. However, in the latter case, if used for a long time, there is a possibility that a small amount of ozone gas may penetrate into the fluororesin and corrode the base material. There are round shape and box shape. A common type is the round flange type, typically 100 to 12 ID.
A flexible tube having a volume of 5 mm, a length of 0.5 to 1 m, and a length of 1.5 m can accommodate 62 to 125 flexible tubes. In addition, a box shape is also possible, which is significant in terms of arranging the inlet and outlet of liquid or ozone gas on the same surface for downsizing. In addition, production processing, maintenance,
The box type is more convenient in consideration of cleaning. By the way, the round type has a diameter of 100 mm and a length of 1 m.
It has a cube size of 20 cm.

In using such an ozone dissolution module, as described above, the PT inside the case is used.
A liquid and a gas (ozone gas) may be passed through the inside and the outside of the FE porous tube, and the gas and the liquid may be contacted through the pores of the porous PTFE. At this time, the pressure of the ozone gas need not be higher than the pressure of the liquid. This is because even if the pressure of ozone gas is lower than the pressure of liquid, ozone is dissolved from the gas into the liquid due to the concentration of ozone. However, as mentioned above, the dissolution can be preferably promoted by increasing the pressure of the gas and bubbling the gas in the liquid.

In the conventional bubbling method, the gas-liquid contact time becomes longer as the depth of the liquid is longer, but the contact time of ozone gas with the liquid is limited. Further, since the contact time with the liquid is short, the dissolution is very little. When the tube according to the method of the present invention is used, the gas-liquid contact time can be freely selected by lengthening the tube, and there is no loss of ozone gas, and the liquid can be contacted at a constant ozone gas concentration for a long time.

The liquid that dissolves ozone is usually water, pure water, etc., but is not particularly limited as long as it is an aqueous system.
It can be used according to the purpose. The liquid in which ozone is dissolved in the module of the present invention is used depending on the purpose.

[0025]

【Example】

Example 1 A porous PTFE tube 1 as shown in FIG. 1 was produced. This is made by mixing 100 parts by weight of PTFE fine particles and 22 parts by weight of petroleum naphtha and then preforming it into a tube shape, extruding this with an extruder, drying and heating to 250 ° C. for 2.1 to 2.
It is a tube made by stretching it twice and then baking it at 360 ℃. The dimensions of this tube are 1.7 mm inside diameter and 2.7 m outside diameter.
The m 2, film thickness was 0.5 mm, average pore size was 0.5 μm, porosity was 50%, and water pressure resistance was 0.9 kg / cm ² .

Further, the porosity is 40%, the average pore diameter is 0.2 μm,
A uniaxially stretched PTFE unsintered film having a thickness of 70 μm was prepared and wrapped around the above extrusion-molded porous tube so as to have two wraps as shown in FIG.
After making an unfired tube with an outer diameter of 3.1 mm,
After firing for a minute, a tube as shown in FIG. 3 was produced. Figure 1,
2 and 3, 1 is an extruded porous PTFE tube,
2 is a stretched porous PTFE film, FIG. 1 and FIG. 2 are perspective views, and FIG. 3 is a transverse sectional view. The tube had an inner diameter of 1.7 mm, an outer diameter of 3.1 mm, and a water pressure resistance of 6.0 kg / cm ² .

As shown schematically in FIG. 4, this tubular membrane was manufactured into a module with 60 tubular membranes (each tubular membrane 1.5 m). In FIG. 4, 11 is a PTFE porous tubular membrane, 12 is a cylindrical P having a diameter of 125 m and a length of 1 m.
A VDF case body, 13 is a PTFE flange, 14 is a FEP manifold forming member to which a tubular membrane is attached, 15 is pure water inlet, 16 is pure water outlet, 17 is ozone gas inlet, and 18 is ozone gas outlet.

In this module, pure water (ozone concentration 0 pp) was flown from the pure water inlet 15 at a pressure of 0.2 kg / cm ² and a flow rate of 5 l / min, while high concentration ozone gas was supplied from the ozone gas inlet 17.
Aeration was carried out at a pressure of 0.21 kg / cm ² . The liquid temperature was 25 ° C. Pure water with ozone dissolved from pure water outlet 16 is 3ppm
The ozone concentration of Next, when the flow rate of pure water was gradually decreased while maintaining the ozone concentration and pressure, the dissolved ozone concentration showed a maximum of 11 to 12 ppm.

The contamination of the collected pure water was measured, but there was no contamination of 0.2 μm or more. No ozone odor was generated around this module. In addition, I used it for 3 months, but PTF
It was also proved that the E-tubular membrane had no change and was ozone resistant.

Example 2 A PTFE porous tubular membrane was prepared in the same manner as in Example 1, and a module was prepared from the PTFE porous tubular membrane, and the same measurement as in Example 1 was carried out. However, the PTFE porous film wrapping around the extruded porous tube has a porosity of 60%, an average pore size of 0.2 μm, and a film thickness of 35 μm.
It was replaced with a PTFE biaxially stretched porous film of m 2. PTF
The E porous tubular membrane has the structure shown in FIGS. 3 and 5 (in these figures, 2 is a PTFE biaxially stretched porous film). FIG. 5 is a vertical cross-sectional view of this PTFE porous tubular membrane, in which the PTFE biaxially stretched porous film 2 is wound around the PTFE extruded porous tube 1 on the inner side to form the PTFE biaxially stretched porous film 2. Has a uniform pore size, and thus has a function as a filter. The tubular membrane has an inner diameter of 1.7 mm and an outer diameter of 2.84.
mm, porosity 50%, average pore size 0.2 μm, water pressure resistance 5.5
It was kg / cm ² .

Also in this case, pure water having the same ozone concentration as in Example 1 was obtained, and there was no contamination of 0.1 μm or more.
No odor of ozone was generated around the module.
Furthermore, it was also proved that the PTFE tubular film did not change even after being used for 3 months, and that it had ozone resistance. Example 3 An unsintered PTFE biaxially stretched porous film having a porosity of 60%, a film thickness of 35 μm and an average pore diameter of 0.2 μm was applied to a stainless pipe (SUS304) having an outer diameter of 3.0 mm 5 times as shown in FIG. It was wound into a roll, put in a furnace at 360 ° C for 15 minutes, baked and taken out. After cooling, pull out the stainless steel pipe, P
Only TFE tubular membranes were obtained.

After calcination, the porosity of this tubular membrane changed to 55% (average pore diameter 0.2 μm) and the thickness 35 μm.
The thickness of the tubular membrane prepared by stacking five m-thick films in five layers was 140 μm (outer diameter 3.24 mm). The water pressure resistance of this tubular membrane was 3.8 kg / cm ² . Using this tubular membrane, a module as shown in FIG. 4 was produced. The length of one tubular membrane was 30 cm, and 50 tubular membranes were used.

This module was measured as in Example 1. The pure water in which the ozone dissolved from the pure water outlet 16 is
The ozone concentration was 3 ppm. Then, when the pure water flow rate was gradually decreased while keeping the ozone concentration and pressure, the dissolved ozone concentration showed a maximum of 12 to 14 ppm. No ozone odor was generated around this module. After being used for 3 months, there was no change in the PTFE tubular membrane.

[0034]

As described above, according to the tubular film of the present invention, ozone is efficiently dissolved in the liquid at a constant concentration and there is no outflow or loss of ozone to the outside.
It can also solve health problems to the human body. Further, according to the present invention, ozone gas can be easily dissolved in water and pure water, and a maximum of 16 pp
m 2 and 12 ppm at all times, the sterilizing effect is great, the material is not changed by ozone, and it can be used stably and for a long time.

Therefore, according to the present invention, it is possible to eliminate the health hazard to the human body due to residual chlorine due to chlorine sterilization currently used for sterilizing tap water and foods, and to downsize the apparatus. In addition, disinfection can be performed without using chemicals. Further, in the field of semiconductors, it is expected to be industrially effective in that it is effective when used in combination with pure water for cleaning. Further, since sterilization by ozone is a new field, it is expected that future unexpected applications will be expanded.

[Brief description of drawings]

FIG. 1 is a perspective view of an extruded tube for producing an ozone-dissolving tubular film of Example 1.

FIG. 2 is a perspective view showing a process of producing an ozone-dissolving tubular film of Example 1.

3 is a cross section of the ozone-dissolving tubular film of Example 1. FIG.

FIG. 4 is a sectional view schematically showing an ozone dissolution module.

5 is a vertical cross section of the ozone-dissolving tubular film of Example 2. FIG.

FIG. 6 is a perspective view showing a production process of an ozone-dissolving tubular film of Example 3.

[Explanation of symbols]

 1 PTFE Extruded Porous Tube 2,3 PTFE Uniaxially or Biaxially Stretched Porous Film 11 PTFE Porous Tubular Membrane 12 Case 15 Pure Water Inlet 17 Ozone Gas Inlet

Claims (2)

[Claims] 1. Ozone is brought into contact with a liquid to be treated through a tubular film of porous polytetrafluoroethylene,
A tubular membrane used in an ozone dissolution module for dissolving ozone in a liquid to be treated, the tubular membrane comprising a porous tube obtained by stretching an extruded tube of polytetrafluoroethylene, and the porous membrane. A tubular film for dissolving ozone in a liquid, which is formed from a porous film obtained by stretching a polytetrafluoroethylene sheet laminated on the outer circumference of the tube. 2. Ozone is brought into contact with a liquid to be treated through a tubular film of porous polytetrafluoroethylene,
A tubular film used in an ozone dissolution module for dissolving ozone in a liquid to be treated, wherein the tubular film is formed from a porous film obtained by stretching a polytetrafluoroethylene sheet. A tubular film for dissolving ozone in a liquid.