JP2015223575A - Fine bubble generating gas-permeable film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas-permeable substance, in the cleansing of a precision component, the production of an air-containing food or the like, in which the contamination of a foreign substance, even if a little, is not allowed, capable of blocking the contamination of the foreign substance from a bubble generating device for supplying fine bubble, and forming minute bubbles of a uniform size.SOLUTION: In a gas permeable part of a fine bubble generating device for feeding minute bubbles, there is arranged a gas permeable film not allowing foreign substances such as dust or dirt contained in a gas to be sucked. The gas permeating face of said gas permeable film is formed with fine irregularities of micro nano sizes, to give a hydrophilic property and a foam releasing property to said gas permeating face, so that gas bubbles just after formed are promoted to leave said gas permeable film early thereby to form uniform minute bubbles in the water.

Description

  The present invention provides a microbubble generator for supplying micro / nano-sized micro / ultra-fine micro-bubbles in liquids such as fresh water, sea water, and a chemical solution, for the purpose of efficiently generating micro-bubbles having a desired size. The present invention relates to a gas permeable film for generating fine bubbles, which is disposed in a gas permeable portion of a fine bubble generator.

  Gas supply methods such as oxygen in the aquarium for aquarium fish, live fish cages, etc. for the purpose of maintaining and nurturing seafood and aquatic organisms include electric air pumps, oxygen cylinders, oxygen generators. In general, electric air pumps are widely used because of their convenience in that they are easy to handle. In the use of the electric air pump, a large amount of gas such as oxygen taken into the air pump is released into the water in a foam form through a large number of micropores provided in the gas discharge section.

  However, the foam released into the water through a large number of micropores provided in the gas discharge part is of a size that has sufficient buoyancy, and many foams rise from the early stage of foam release in the gas release part and enter the atmosphere. It is released one after another and is not an efficient method for supplying oxygen and the like.

  Therefore, in the patent No. 3806008 owned by the present applicant, a fine gas permeable material is used as a gas permeable material, which is a gas permeable material (hereinafter referred to as a “craze-generating gas permeable film”) formed by forming crazes on a polymer resin film. The gas permeation amount of the craze-generating gas permeable film is adjusted by adjusting the pressure condition of the gas that is disposed in the gas permeation part of the bubble generating device and expands voids (fine communication holes) constituting the craze and permeates. A technique for generating micro / nano-sized fine / ultrafine microbubbles (hereinafter referred to as “miniature bubbles”) that easily stagnate in water by controlling the restriction is disclosed.

  In recent years, the use of air bubbles is not limited to the supply of oxygen, etc., for the purpose of maintaining the survival of fish and shellfish, but in many areas such as purification of water, various types of washing, production of aerated food, cultivation of agricultural products, and improvement of combustion efficiency. Diversified.

  In various types of cleaning, we have recognized that it is useful to generate microbubbles of uniform size in the cleaning of precision parts and in the manufacture of some aerated foods. No. 4,325,973, by combining a foam material made of a non-woven fabric having hydrophilicity on the gas permeable surface of the crazed gas permeable film to give the gas permeable surface a defoaming property, and the bubble growth generated sequentially A technique is disclosed in which bubbles that stagnate in the gas permeation port immediately after the generation that hinders the generation of air are quickly separated from the gas permeation surface to generate uniform microbubbles in water.

Japanese Patent No. 3806008 Japanese Patent No. 4325973

  The problem to be solved is that the technology disclosed in Japanese Patent No. 4325973 is concerned with the generation of tiny bubbles in the cleaning of precision parts, the production process of aerated food, etc., which are not allowed even if a slight amount of foreign matter is mixed. The following issues will be proposed.

  Japanese Patent No. 4325973 is sequentially generated by combining a foaming material made of a nonwoven fabric having hydrophilicity on the gas permeable surface of the craze-generating gas permeable film and providing the gas permeable surface with foam releasing properties. It is a patent that discloses a technique for quickly detaching bubbles that are trapped in the gas permeation port immediately after generation, which can be an obstacle to the growth of bubbles from the gas permeation surface, and the use of a foam sealant made of a hydrophilic nonwoven fabric or the like. It is indispensable.

  However, it is unexpected that if the foam material to be combined with the gas permeable surface of the craze-generating gas permeable film is composed of a nonwoven fabric, there are fiber scraps that may be present in the nonwoven fabric and bacteria that may be propagated in the nonwoven fabric. However, it is an undeniable fact that the use of non-woven fabrics is regarded as a problem as a cause of foreign matters being mixed in the liquid, which is a problem to be solved.

  The present invention provides a microbubble generator for supplying microbubbles in liquids such as fresh water, seawater, and chemicals, with the purpose of efficiently generating microbubbles having a uniform size without mixing foreign substances into the liquid. It is an improvement technology of gas permeable film for generating fine bubbles, which is arranged in the gas permeable part of the fine bubble generating device. Micro / nano-sized fine irregularities are formed on the gas permeable surface of the crazed gas permeable film. In addition to having hydrophilicity on the gas permeable surface, it also has the ability to release bubbles quickly from the gas permeable surface by reducing the contact between the surface of the bubbles generated in the liquid and the gas permeable surface. Make it.

Micro / nano-sized fine irregularities are made of UV, ozone, plasma, corona discharge, surface modification using alkaline chemicals such as sodium hydroxide solution, acidic chemicals such as chromic acid and sulfuric acid. Surface modification treatment using gas, surface modification of the gas permeable surface by flame treatment, etc., or calcium chloride hydroxide (CaCl (OH)), magnesium chloride hydroxide (MgCl (OH)), sodium bicarbonate (NaHCO 3) ₃ ), using a means such as attaching inorganic salt crystals produced by a chemical substance such as calcium phosphate (Ca ₃ (PO ₄ ) ₂ ) to the gas permeable surface on the gas permeable surface of the craze-generating gas permeable film. Let it form.

  In the present invention, micro / nano-sized fine irregularities are formed on the gas permeable surface of the gas permeable film, the gas permeable surface is hydrophilic, the bubbles generated in the liquid on the gas permeable surface, the gas permeable surface, The main gist of the present invention is that it has a defoaming property that quickly removes bubbles from the gas-permeable surface, and has micro- and nano-sized fine irregularities formed on the gas-permeable surface. The resulting gas-permeable film can be used to liquefy uniform microbubbles by using only a single gas-permeable film without compounding hydrophilic non-woven fabric, etc. Since it can be produced in the inside, it becomes a useful technique in many fields such as cleaning of precision parts, production of aerated food, etc., which are not permitted even if a small amount of foreign matter is mixed.

FIG. 1 is a schematic explanatory view showing the configuration of the gas permeation section of the microbubble generator. FIG. 2 is a schematic explanatory view for explaining the gist of the present invention.

  The present invention is an improvement technique of a gas permeable film arranged in a gas permeable portion of a fine bubble generating device for supplying microbubbles, and a micro-nano-sized fine film is formed on a gas permeable surface of a crazed gas permeable film. By forming a rough surface, the gas permeable surface is hydrophilic, and the gas permeable surface reduces the contact between the surface of the bubble generated in the liquid and the gas permeable surface, so that the gas permeable surface can be quickly evacuated. By combining it with the ability to release bubbles, it is uniform by using only a single gas permeable film, without compounding hydrophilic nonwoven fabrics, etc., that foreign matter may be discharged and mixed into the liquid. It is a gas-permeable film for generating fine bubbles that can generate microbubbles in a liquid.

  For long-term use, it is assumed that germs and the like propagate on the gas permeation surface of the craze-generating gas permeable film formed with micro / nano-sized fine irregularities. Breeding is easy to wash and can be wiped with a cleaning solution or the like. In addition, it is easy to suppress the propagation of germs and the like by producing a crazing gas permeable film employing an antibacterial material and antibacterial treatment of the gas permeable surface within an allowable range.

  The formation of micro- and nano-sized fine irregularities on the gas permeable surface of the crazed gas permeable film is achieved by surface modification using alkaline chemicals such as UV irradiation, ozone treatment, plasma irradiation, corona discharge treatment, and sodium hydroxide solution. Quality treatment, surface modification treatment using acidic chemicals such as chromic acid / sulfuric acid, flame treatment, etc., or UV irradiation, ozone treatment, plasma irradiation, corona discharge treatment, sodium hydroxide solution, etc. Any combination of surface modification treatment using alkaline chemicals, surface modification treatment using acidic chemicals such as chromic acid / sulfuric acid, flame treatment, etc. is applied to the gas permeable surface of the craze-generating gas permeable film. By applying, the gas permeation surface is surface-modified.

In addition, any chemical substance such as calcium chloride hydroxide (CaCl (OH)), magnesium chloride hydroxide (MgCl (OH)), sodium hydrogen carbonate (NaHCO ₃ ), calcium phosphate (Ca ₃ (PO ₄ ) ₂ ) or the like , Calcium chloride hydroxide (CaCl (OH)), magnesium chloride hydroxide (MgCl (OH)), sodium hydrogen carbonate (NaHCO ₃ ), calcium phosphate (Ca ₃ (PO ₄ ) ₂ ), etc. Crystals of the inorganic salt produced by the above can be attached to the gas permeable surface of the craze-generating gas permeable film to form micro / nano-sized fine irregularities on the gas permeable surface.

  A micro-nano-sized fine unevenness is formed on the gas permeable surface of the gas permeable porous membrane according to claim 4 to impart hydrophilicity and defoaming property to the gas permeable surface. The gas-permeable film for generating microbubbles is formed in a liquid by forcibly permeating gas using a pressurized gas, although the porous film normally has a low gas permeability. It has a structure that can generate microbubbles.

  Hereinafter, the gas permeable film for generating fine bubbles of the present invention will be described in detail with reference to the drawings. In addition, since the main body of this invention exists in the gas-permeable film for microbubble production | generation, description of a microbubble generator is simplified.

  The gas permeable film for generating microbubbles of the present invention is a microbubble generator for supplying microbubbles into liquids such as fresh water, seawater, and chemicals. The microbubble generator of the microbubble generator shown in FIG. A micro- / nano-sized film is formed on the gas-permeable surface 3 of the craze-generating gas-permeable film 1, which is disposed in a gas-permeable portion (hereinafter referred to as “gas-permeable portion”) 2 together with a permeable material fixing frame, packing and the like. It is a gas permeable film in which fine irregularities 5 are formed, and by limiting the amount of gas permeation of compressed air, compressed oxygen, etc. filled in the gas permeable portion 2 with fine communication holes, the microbubbles 7 are contained in the liquid. Is generated.

  FIG. 2 is a schematic explanatory view for explaining the gist of the present invention. The gas-permeable film for generating fine bubbles according to the present invention is formed by forming micro / nano-sized fine irregularities 5 on the gas-permeable surface 3 of the craze-generating gas-permeable film 1 so that the gas-permeable surface 3 has hydrophilicity and gas. Contact between the surface of the microbubble 7 generated in the liquid W on the permeable surface 3 and the gas permeable surface 3 is reduced, and a bubble releasing property that allows the tiny bubble 7 to be quickly detached from the gas permeable surface 3 is imparted. Thus, it is possible to easily generate uniform microbubbles 7 in the liquid W by using only a single gas permeable film.

  In FIG. 2, A is an initial bubble generated in the gas permeable opening 8 formed on the gas permeable surface. Since the gas permeable surface 3 has hydrophilicity and the liquid permeates toward the gas permeable opening 8 at the initial stage of the generation of the bubbles A, the bubble growth is blocked at an early stage and a very small bubble is generated.

In FIG. 2, B is a very small bubble generated in the liquid. The micro-nano-sized fine irregularities 5 formed on the gas permeable surface 3 of the crazing gas permeable film 1 and the liquid W penetrating the gas permeable surface 3 facilitate the separation of the microbubbles 7 on the gas permeable surface 3. Is done.
In the figure, ← W indicates the penetration direction of the liquid.

  As shown in the figure, the gas-permeable film 1 for generating fine bubbles according to the present invention is formed by forming micro / nano-sized fine irregularities 5 on the gas-permeable surface 3 of the craze-generating gas-permeable film 1. The permeation surface 3 is imparted with hydrophilicity and defoaming property, and since the liquid permeates toward the gas permeable opening 8 at the initial stage of bubble generation due to the hydrophilicity, the bubble growth is blocked at an early stage and is minimal. Bubbles are generated, and the detachment of microbubbles on the gas permeable surface 3 is promoted by the bubble releasing property.

[Gas permeability of crazed gas permeable film]
Compressed air, compressed oxygen, and the like charged in an oxygen replenisher vary depending on the type of resin used, but generally have a gas permeability of oxygen and nitrogen gas of 0.3 to 100,000 × 10 ⁴ cm ³ / m ^2. Within the range of 24 hr · atm, the amount of permeation is restricted by the craze-generating gas permeable film and discharged into water in the form of fine bubbles.

[Fine uneven shape]
The micro / nano-sized fine irregular shape formed on the gas permeable surface 3 of the crazing gas permeable film 1 varies depending on the means for forming the irregularities, but is needle-like, columnar, cubic, dendritic, fibrous, Gas permeation through fine irregularities of any shape such as thread shape, plate shape, dimple shape or any composite shape such as needle shape, column shape, cube shape, dendritic shape, fiber shape, thread shape, plate shape, dimple shape, etc. Form on surface 3. Since the contact between the outer peripheral surface of the microbubble and the gas permeable surface 3 is reduced, it is necessary to promptly release the microbubble on the gas permeable surface 3, so that fluffy fine irregularities are formed on the gas permeable surface 3. It is also desirable that

  The present invention is to form micro / nano-sized fine irregularities on the gas permeable surface of the craze-generating gas permeable film, and to make the gas permeable surface hydrophilic and the surface of the bubbles generated in the liquid and the gas permeable surface. One of the gist is to quickly detach micro / nano-sized micro / ultra-fine micro bubbles generated in the liquid from the gas permeation surface by reducing contact with the gas. However, microbubbles also include bubbles of a size that can remain attached to the gas permeable surface after being generated. In addition, even in the micro-nano-sized fine irregularities formed on the gas permeable surface of the craze-generating gas permeable film, there are irregularities of a size that can express the defoaming property for the size of the generated bubbles included.

[Attached bubbles]
When only a craze-generating gas permeable film with no micro / nano-sized fine irregularities formed is used as a gas permeable material, adhering air bubbles are quickly formed on the gas permeable surface from the gas permeable surface. The attached bubbles are formed without being bubbled, and the bubbles are eventually released into the water in a united state. Therefore, the purpose of the present invention is to efficiently generate uniform and extremely small bubbles of the intended size. I can't.

The micro / nano-sized fine irregularities formed on the gas permeable surface of the crazed gas permeable film are calcium chloride hydroxide (CaCl (OH)), magnesium chloride hydroxide (MgCl (OH)), sodium bicarbonate ( Any chemical substance such as NaHCO ₃ ), calcium phosphate (Ca ₃ (PO ₄ ) ₂ ), calcium chloride hydroxide (CaCl (OH)), magnesium chloride hydroxide (MgCl (OH)), sodium bicarbonate (NaHCO 3) ₃ ), crystals of inorganic salts produced by combining chemical substances such as calcium phosphate (Ca ₃ (PO ₄ ) ₂ ) can be formed by adhering to the gas permeable surface.

One method of attaching crystals to the gas permeable surface is represented by the following equation.
Ca (OH) ₂ + CO ₂ → CaCO ₃ + H ₂ O (1)
In the above formula, Ca (OH) ₂ is calcium hydroxide, CO ₂ is carbon dioxide, CaCO ₃ is calcium carbonate, and H ₂ O is water.

  The craze-generating gas permeable film is partly described in Japanese Patent Application Laid-Open No. 7-256676 and Japanese Patent No. 3156058 by the applicant of the present invention, and is provided with a striped craze region in a polymer resin film. Thus, a gas such as air is allowed to pass through in a slightly pressurized state, but a liquid or water-like gel or gel-like solution cannot be passed.

  The polymer resin used as the material of the polymer resin film can be formed into a film or a sheet, such as polyolefin, polyester, polyamide, styrene resin, polycarbonate, halogen-containing thermoplastic resin, nitrile resin, etc. A thermoplastic resin can be mentioned.

  The polyolefin is an α-olefin homopolymer or a copolymer with another α-olefin and / or α-olefin as a main component and another ethylenically unsaturated monomer. Here, the copolymer may be a block, random, graft, or a composite thereof. Examples of the ethylenically unsaturated monomer include unsaturated carboxylic acids or anhydrides such as methacrylic acid, methyl methacrylate, and maleic acid.

  Specific examples of useful polyolefins include low density branched polyethylene, high density linear polyethylene, low density linear polyethylene, isotactic polypropylene, syndiotactic polypropylene, poly (1-butene), poly (4-methyl-1 -Pentene) and the like.

  Polyamide is a condensation product containing, as an essential component, a repeating unit having an aromatic or / and aliphatic amide group. Useful polyamides include nylon-4, nylon-6, nylon-6,6, nylon-4,6, nylon-12, amorphous nylon and the like. Among these, preferred polyamides are nylon-6, nylon-6,6, and amorphous nylon.

  Examples of the polyester include, for example, a thermoplastic polyester produced by condensing a dicarboxylic acid or a lower alkyl ester thereof, an acid halide or an acid anhydride derivative and a glycol or a dihydric phenol according to a usual method. Can do. Among these polyesters, it is preferable to use saturated polyesters, particularly polyethylene terephthalate, polybutylene terephthalate, and polynaphthalene terephthalate.

  The styrene resin is a polymer of a vinyl aromatic compound, and specific examples of the vinyl aromatic compound include styrene, α-methylstyrene, paramethylstyrene, vinyl toluene, vinyl xylene, and the like. Styrenic resins are homopolymers and copolymers of these vinyl aromatic compounds. Among these, polystyrene is preferable, and rubber graft polystyrene (HIPS) and acrylonitrile / butadiene / styrene copolymer are preferably used.

  Examples of the polycarbonate include aromatic polycarbonate, aliphatic polycarbonate, and aliphatic / aromatic polycarbonate. Among these, aromatic polycarbonates composed of 2,2-bis (4-oxyphenyl) alkane-based, bis (4-oxyphenyl) ether-based, bis (4-oxyphenyl) sulfone, sulfide or sulfoxide-based bisphenols are used. It is preferable to use it.

  Examples of the halogen-containing thermoplastic resin include homopolymers and copolymers such as tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, vinylidene fluoride, and vinyl fluoride. In addition, homopolymers and copolymers derived from vinylidene chloride can be mentioned. Among these, preferable halogen-containing thermoplastic resins include homopolymers of polyvinylidene fluoride, copolymers with tetrafluoroethylene, hexafluoropropylene, and chlorotrifluoroethylene, and vinylidene chloride.

  The nitrile resin contains 50% by weight or more of α-β olefinic unsaturated mononitrile. Among these unsaturated mononitriles, it is preferable to use acrylonitrile and methacrylonitrile and mixtures thereof.

  Among the thermoplastic resins, polyolefin, polyester, styrene resin, and halogen-containing thermoplastic resin are preferably used from the viewpoint of moldability to a film or sheet and economical efficiency. These thermoplastic resins may be used alone, combined and used as a composition, or may be blended with another polymer resin, and two or more types of resins may be multilayered. It may be used.

In view of the ease of formation of crazes, it is desirable to use a resin having a glass transition temperature of −45 ° C. or higher, preferably −30 ° C. or higher, particularly preferably −15 ° C. or higher.
When used as a composition or in a multilayered form, it is preferable that the glass transition temperature of the thermoplastic resin, which is the main component, is within the above range. In the case of a thermoplastic resin exhibiting a glass transition temperature lower than this, it is difficult to efficiently form a craze because it is too flexible.

  The polymer resin film or sheet obtained by using a thermoplastic resin is not particularly limited in its production method, and can be obtained by applying various molding methods. A product obtained by applying a molding method or a blow-up inflation molding method is industrially advantageous.

  The thickness of the polymer resin film is generally 0.5 to 1,000 μm, preferably 1 to 800 μm, particularly preferably 2 to 500 μm.

The polymer resin film has a degree of molecular orientation having a birefringence of 0.5 × 10 ⁻³ or more, preferably 1 × 10 ⁻³ or more, particularly preferably 1.5 × 10 ⁻³ or more. This is effective for the formation of crazes. In a film having a molecular orientation whose birefringence is out of the above range, it is difficult to easily form an intended craze. The degree of orientation refers to the molecular structure such as the resin temperature, take-off speed, cooling rate, resin molecular weight, molecular weight distribution, tacticity, etc. at the time of forming the film, especially the draw ratio in the case of the T-die method, and in particular the inflation method. If there is, the film can be controlled by changing the blow-up ratio and the like, and thus a film having an orientation degree in a desired preferable range can be produced by appropriately controlling these.

  The birefringence referred to here is expressed as a difference between the main refractive indexes. For example, the difference between the refractive index (n1) in the film forming direction and the refractive index (n2) in the direction perpendicular thereto (n1-n2). ) And is one of the indexes expressing the degree of molecular orientation. In actuality, these birefringence can be measured by using a deflection microscope and a compensator, and the larger the value, the greater the anisotropy and the more likely to cause crazing.

  The striped craze of the craze-generating gas permeable film used in the present invention is basically substantially parallel to the direction of molecular orientation of the polymer resin film and generally has a width of 0.5 to 100 μm, preferably 1 ˜50 μm. The ratio of the number of crazes penetrating in the thickness direction of the film is 10% or more, preferably 20% or more, particularly preferably 40% or more, and penetrating. If the ratio is less than the above range, sufficient air permeability cannot be obtained.

  The craze is formed in a direction substantially parallel to the molecular orientation direction. The craze is formed by pulling in the direction perpendicular to the molecular chain orientation direction, and the craze is formed in a direction perpendicular to the molecular chain orientation direction. Because it is difficult to do. The craze mentioned here includes a surface craze appearing on the surface of the polymer resin film and an internal craze generated inside, and refers to a region having a fine crack-like pattern. This craze is composed of molecular bundles (fibrils) and microvoids, and the gas permeability of various gases is generated in this portion.

The crazing gas permeable film as described above varies depending on the type of resin used, but as an example, when a homopolymer of polyvinylidene fluoride is used, the gas permeability of oxygen and nitrogen gas is generally 0.3 to 100, 000 × 10 ⁴ cm ³ / m ² · 24 hr · atm. The moisture permeability is generally 10 to 100,000 × 10 ⁴ g / m ² · 24 hr. The transparency is generally 1 to 99.5 haze, preferably 2 to 90 haze, particularly preferably 5 to 80 haze. The tensile strength is generally 50 to 500 kg / cm ² , preferably 60 to 500 kg / cm ² , particularly preferably 75 to 500 kg / cm ² .

  The craze formed on the polymer resin film is generally formed in an interval of 0.1 to 1,000 μm, preferably 1 to 800 μm, and is an amount that can be recognized as a striped region.

  Since the craze-generating gas permeable film used in the present invention has the above-mentioned striped craze, it has functions of air permeability and moisture permeability. The mechanism is that the craze formed in stripes penetrates in the thickness direction of the film or sheet, so that gas such as oxygen, nitrogen or water vapor passes by diffusing through this craze zone and air permeability is developed. .

  The degree of breathability of the craze-generating gas permeable film can be adjusted by changing the width of the crazes formed in the polymer resin film, the distance between the crazes, and the ratio of the number of crazes penetrated. Specifically, by adjusting the degree of molecular orientation of the polymer resin film, the temperature at which the craze is formed, the tension of the polymer resin film (tension in the tension state), the folding angle of the film, etc. Breathability can be controlled and a breathable film can be provided according to the intended use.

  For example, increasing the tension when forming a craze or reducing the folding angle reduces the spacing between the generated crazes and increases the percentage of the number of crazes penetrated, resulting in increased breathability. . The craze-generating gas permeable film adjusted by changing the width of the craze, the distance between the crazes, and the ratio of the craze penetrated is the gas permeability, moisture permeability, transparency, tensile strength of the oxygen and nitrogen gas. Strength etc. can be controlled.

  One aspect of the present invention is to form micro / nano-sized fine irregularities on the gas permeable surface of the gas permeable porous membrane, so that the gas permeable surface is hydrophilic and the gas permeable surface is submerged in the liquid. Foreign matter is discharged and mixed into the liquid by reducing the contact between the surface of the generated bubbles and the gas permeable surface, and also having a defoaming property that allows the bubbles to be quickly detached from the gas permeable surface. It is a gas-permeable film for generating fine bubbles that can generate uniform microbubbles in a liquid by using only a single gas-permeable film without combining a hydrophilic non-woven fabric and the like.

  The porous film having gas permeability is generated by heating and stretching a polymer resin film such as baked polytetrafluoroethylene (PTFE). Striped fibrils are generated by uniaxial stretching, and granular nodes and radial fibrils are generated by biaxial stretching, and the pores formed in the film have air permeability. it can.

  The porous membrane will be described in more detail with reference to polytetrafluoroethylene (hereinafter referred to as PTFE). Since PTFE is a filamentous crystalline polymer (98.5% or more) having a molecular weight of about 0.1 μm / 50,000, Then, melt extrusion molding is not possible. Therefore, about 15 to 25% of kerosene or naphtha is mixed as a lubricant, and then thinly stretched with a calender roll at 80 ° C. and heated to remove the lubricant. Here, uniaxial or biaxial stretching is performed and sintering is performed at 327 ° C.

  At this time, the amorphous capacity increases and is fixed. In this way, a porous membrane having fine pores having a pore diameter of 0.02 to 15 μm and a porosity of 25 to 95% can be formed. When heated and uniaxially stretched, striped fibrils are generated, and biaxially stretched to generate granular nodes and radial fibrils, expanding fine pores in the film and venting. It has a sex.

  The present invention can generate uniform microbubbles in a liquid by using only a single gas permeable film without compounding a hydrophilic nonwoven fabric or the like that is likely to be contaminated due to foreign matter being discharged. Therefore, it is a technique that is useful in many fields, such as cleaning of precision parts and production of aerated food, which are not permitted even if a small amount of foreign matter is mixed.

DESCRIPTION OF SYMBOLS 1 Craze production | generation gas permeable film 2 Gas permeation | transmission part of a microbubble generator 3 Gas permeation surface 5 Micro-nano size minute unevenness 7 Micro bubble 8 Gas permeation opening formed in the gas permeation surface A Initial generation in liquid Bubble B B Minimal bubble generated in liquid W Liquid E Gas M Microvoid (fine communication hole)
F fibril (molecular bundle)

Claims (4)

  In a micro-bubble generator that supplies micro / nano-sized micro / ultra-fine micro-bubbles in fresh water, seawater and chemicals, etc., the micro-bubbles are generated for the purpose of efficiently generating micro-bubbles of uniform size. It is a gas permeable film that is arranged in the gas permeable part of the device, and has micro / nano-sized fine irregularities on the gas permeable surface of the gas permeable film formed by forming a crazed region in a polymer resin film. A gas permeable film for generating fine bubbles, wherein the gas permeable surface is provided with hydrophilicity and defoaming property by being formed.   Micro / nano-sized fine irregularities formed on the gas permeable surface of a gas permeable film formed by forming a crazed region in a polymer resin film are UV irradiation, ozone treatment, plasma irradiation, corona discharge treatment, sodium hydroxide Surface modification treatment using alkaline chemicals such as solution, surface modification treatment using acidic chemicals such as chromic acid / sulfuric acid, flame treatment, etc., UV irradiation, ozone treatment, plasma irradiation , Corona discharge treatment, surface modification treatment using alkaline chemicals such as sodium hydroxide solution, surface modification treatment using acidic chemicals such as chromic acid / sulfuric acid, flame treatment, etc. The gas permeable film for generating fine bubbles according to claim 1, wherein the gas permeable surface is surface-modified. Micro / nano-sized fine irregularities formed on the gas permeable surface of the gas permeable film formed by forming a crazing region in the polymer resin film, calcium chloride hydroxide (CaCl (OH)) on the gas permeable surface, Any chemical substance such as magnesium chloride hydroxide (MgCl (OH)), sodium hydrogen carbonate (NaHCO ₃ ), calcium phosphate (Ca ₃ (PO ₄ ) ₂ ), or calcium chloride hydroxide (CaCl (OH)), chloride Crystals of inorganic salts produced by the combination of any chemical substance such as magnesium hydroxide (MgCl (OH)), sodium hydrogen carbonate (NaHCO ₃ ), calcium phosphate (Ca ₃ (PO ₄ ) ₂ ), etc. are attached. The gas-permeable film for generating fine bubbles according to claim 1.   2. The gas permeation surface of the porous membrane having gas permeability is formed with micro / nano-sized fine irregularities to impart hydrophilicity and defoaming property to the gas permeation surface. Gas-permeable film for generating fine bubbles.

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