Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L9/00—Disinfection, sterilisation or deodorisation of air
  • A61L9/01—Deodorant compositions
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L9/00—Disinfection, sterilisation or deodorisation of air
  • A61L9/16—Disinfection, sterilisation or deodorisation of air using physical phenomena
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D39/00—Filtering material for liquid or gaseous fluids
  • B01D39/14—Other self-supporting filtering material ; Other filtering material
  • B01D39/16—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
  • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
  • B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
  • B03C3/28—Plant or installations without electricity supply, e.g. using electrets
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H3/00—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length
  • D04H3/08—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length characterised by the method of strengthening or consolidating
  • D04H3/16—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length characterised by the method of strengthening or consolidating with bonds between thermoplastic filaments produced in association with filament formation, e.g. immediately following extrusion

Definitions

• the present invention relates to electrets and electret filters.
• porous filters for dust collection, protection, and ventilation.
• filters made of fibrous materials have advantages of high porosity, long life and low airflow resistance.
• a nonwoven fabric is preferably used as a filter made of such a fibrous material.
• Electrets are materials capable of sustaining and utilizing electrostatic forces through various manipulations of various dielectric materials. Filters that are charged and formed as electrets are widely used as electret filters.
• the inventor of the present invention focused on zinc oxide as an inorganic particle having functionality, and studied compatibility between its functionality and electret properties. However, we faced the problem that it could not be handled in the same way as the conventional electret.
• the present invention has been made in view of the above problems, and an object thereof is to provide an electret and an electret filter containing zinc oxide particles with excellent charge stability.
• an electret and an electret filter containing specific zinc oxide particles can achieve both functions of the electret and zinc oxide particles and have excellent properties. arrived at the invention.
• the invention is shown below.
• the value of a/b is 0.3 or less, where a is the maximum value of the depolarization current at 50 to 100°C measured by the TSC method, and b is the maximum value of the depolarization current at 100°C or higher. 3.
• the electret according to 1 or 2 above characterized in that: 4. 4.
• the electret according to any one of 1 to 4 above which is charged by a liquid contact method.
• 7. The electret filter as described in 6 above, wherein the filter medium quality factor QF value is 1.3 mmAq -1 or more.
• the electret of the present invention uses a polyolefin resin that is hydrophobic and has high electrical resistance, from the viewpoint of the degree of freedom of shape and the electret's charge stability.
• polyolefin resins include homopolymers of olefins such as ethylene, propylene, butylene, hexene, octene, butadiene, isoprene, chloroprene, methyl-1-pentene, and cyclic olefins, and two or more of the above olefins and halogenated olefins.
• a copolymer such as One type of polyolefin resin may be selected and used alone, or two or more types may be selected and used in combination.
• the polyolefin resin preferably contains at least one selected from polyethylene, polypropylene and polymethylpentene, and more preferably contains polypropylene.
• the content of the polyolefin resin in 100% by mass of the electret is preferably 80% by mass or more, more preferably 85% by mass or more, still more preferably 90% by mass or more, and 95% by mass or more. is particularly preferable, and 97% by mass or more is most preferable.
• the resin used in the present invention preferably has a stereoregularity of 85% or more, more preferably 90% or more, still more preferably 90% or more, and most preferably 95% or more.
• isotactic or syndiotactic can be preferably used.
• two or more types of polypropylene it is preferable that one or more types are contained in the contained polyolefin.
• polyolefin resin used in the present invention those having various molecular weight distributions and viscosity characteristics can be preferably used, and the branched chain structure and the like can be selected according to the required final shape and workability. . Also in this case, it is preferable to use one or a combination of two or more.
• the electret in the present invention is characterized by containing zinc oxide particles in polyolefin resin.
• zinc oxide particles have the desired properties, it is also preferable to use one or a combination of two or more of them depending on the required properties.
• Specific functions of zinc oxide particles include dielectric properties, opacity, coloring properties, antibacterial properties, antifungal properties, odor removing properties, antiviral properties, and antiallergenic properties.
• the shape of the zinc oxide particles used in the present invention may be plate-like, needle-like, rectangular, spherical, elliptical, or any other shape. These may be monocrystalline and polycrystalline primary particles, secondary particles with strong or weak bonds. For the purpose of improving the charge stability of the electret, it is preferably spherical, rectangular, or tabular with a small aspect ratio. It is preferred that the particles are primary particles, and most preferably the primary particles have the following sizes. Unintended grain refinement is suppressed during extrusion and mixing processing, and the surface area can be reduced, so that a composition preferable for maintaining electret properties can be obtained.
• the average particle size of the zinc oxide particles used in the present invention ranges from 0.1 ⁇ m to 10 ⁇ m. It is preferably 0.1 ⁇ m to 8 ⁇ m, more preferably 0.1 to 5 ⁇ m, even more preferably 0.1 to 3 ⁇ m, most preferably 0.1 to 2 ⁇ m. If the particle size is small, there is concern about handling as nanoparticles, which is an important characteristic in dealing with various nano-substance regulations. On the other hand, if it is too large, the dispersibility becomes poor and it is necessary to add a large amount in order to develop the functionality. In addition, the polyolefin resin containing zinc oxide particles tends to become brittle and deteriorate in workability.
• the amount of zinc oxide particles to be added can be preferably adjusted according to the required functionality. is 0.05 to 7% by mass, more preferably 0.1 to 5% by mass, most preferably 0.15 to 3% by mass. If it is too small, the antibacterial effect will be insufficient, and if it is too large, workability and mechanical strength will be lowered.
• the zinc oxide particles used in the present invention are characterized by having specific characteristics in photoluminescence (PL) measurement, thereby achieving both electret characteristics and functionality due to the addition of zinc oxide particles. Specifically, it is excited by laser light with a wavelength of 325 nm, and luminescence obtained as photoluminescence is detected with a CCD detector in a wavelength range of 350 to 700 nm.
• the ratio (B/A) of the photoluminescence intensity A in the wavelength range of 350 nm to 400 nm and the photoluminescence intensity B in the wavelength range of 500 nm to 700 nm. is 0.1 or less.
• B/A is preferably 0.09 or less, more preferably 0.05 or less, still more preferably 0.025 or less, and most preferably 0.01 or less.
• the intensity is obtained by correcting the detection sensitivity of the CCD with the detection sensitivity for each wavelength, and allows relative comparison as the amount of photons for each wavelength.
• the maximum height in each of the above ranges is used as the value of A and B. When it exists as a peak, it means the peak value, and when it exists as a tail, it means the maximum value existing on the peak boundary side. It is interpreted as a spectrum of continuously occurring photoluminescence, and is clearly distinguished from large spike-like noise and measurement abnormal values.
• the smaller the B/A value affects charge stability and electret properties due to mechanisms such as the electrical resistivity of the zinc oxide particles themselves or the resin composition that becomes the electret, the oxidation of the electret, and the photochemical reaction. it is conceivable that.
• the detection sensitivity and baseline noise value are low and stable, and the noise value and the measured value obtained by photoluminescence are strictly different.
• a microscopic system capable of measuring in a minute area.
• the method of adding zinc oxide particles to the polyolefin resin used in the present invention is not particularly limited as long as the desired properties can be obtained. Examples include a method of adding zinc oxide particles or precursors during production, a method of adding zinc oxide particles or precursors during molding, and a method of melting and adhering to the surface of molded polyolefin, which are used alone or in combination. be able to.
• zinc oxide particles having predetermined properties are added in advance to the resin during masterbatch or compound production, or they are added together with the resin into the extruder during the production of molded articles such as fibrous materials, films, and extruded materials.
• a method of melt-mixing is preferably used.
• the resin and zinc oxide particles may be mixed in advance using a tumbler or various mixers, or may be separately supplied using a feeder, which can be preferably selected according to the characteristics of the apparatus.
• the resin and the zinc oxide particles may be introduced simultaneously, or the zinc oxide particles may be mixed into the molten resin in the middle.
• a dispersant can be used to improve the dispersibility of the zinc oxide particles during melt mixing and molding.
• the material is not particularly limited as long as it is suitable for exhibiting dispersibility, electret properties, and functionality of zinc oxide particles.
• Those having a hydrophilic group such as an ether group and a hydrophobic group such as a hydrocarbon group and a perfluoro group in a single molecule can be preferably used.
• the molecular weight an appropriate one can be used, taking into account the viscosity and the size and dispersibility of the zinc oxide particles of interest. It may also be substantially the same chemical substance as the surfactant.
• the dispersant it is preferable to attach it to the zinc oxide particles in advance or to add it during mixing.
• the dispersant is a compound containing an ester group
• glycerin fatty acid esters, sorbitan fatty acid esters, fatty acid esters, etc. can be exemplified, and the affinity and melting point of the zinc oxide particles and polyolefin can be improved. It can be used with consideration.
• the melting point of the dispersant mixed during melting is preferably the same or lower than that of the electret polyolefin resin, more preferably 20° C. or more, in consideration of the melting and dispersing functions in the extruder. , and more preferably 50°C or higher.
• the dispersant When the dispersant has a significantly high reactivity with the zinc oxide particles and/or has a higher melting point than the polyolefin resin which is the main component of the electret, it is pre-oxidized using coating or heat mixing in a solution or precursor state. It is also preferable to attach it to the zinc particle surface.
• the surface of the zinc oxide particles with an organic or inorganic material, and various silane coupling agents, organic acids, nitrogen-containing organic compounds, inorganic elements and inorganic oxides can be used. can be done.
• various silane coupling agents, organic acids, nitrogen-containing organic compounds, inorganic elements and inorganic oxides can be used. can be done.
• the molecular structure, viscosity, and flow characteristics of the resin material that serves as the base material for manufacturing the masterbatch or compound that mixes the zinc oxide particles can be adjusted as necessary.
• adjustment of affinity and wettability with zinc oxide particles, adjustment of electret and resin viscosity on the side to be added which is the final form, dispersion of zinc oxide particles, adjustment of surface precipitation and fixed state, phase separation structure examples include the purpose of regulation, the uneven distribution of zinc oxide particles, and the expression of other types of functions. These can be used without being limited to polyolefin resins.
• the present invention it is also preferable to mix various functional materials in the masterbatch or compound at the same time.
• various functional materials for example, nitrogen-containing compounds, various antioxidants, heat resistance improvers, and Viscosity and crystallinity modifiers, pigments, lubricants, antiadhesives and the like can be exemplified. It is also preferable to use the same dispersant for the zinc oxide particles and the functional material.
• the present invention is an electret made of polyolefin resin containing zinc oxide particles.
• Conventionally known methods can be used for electretization, for example, a method of electric field polarization at room temperature or at an elevated temperature, a method of giving positive and negative charges by contacting with electrodes and energizing, photoelectric conversion by light or radiation, etc.
• Methods of imparting electric charge using effects methods of imparting electric charge by contact or friction of liquids or solids, methods of imparting electric charge by crushing or splitting, methods of imparting electric charge by collision of charged particles or charged ions, bending, phase change, etc. can be exemplified.
• the liquid contact method in which the material is electretized by contact with water or a liquid containing water, is preferable. Further, by adding a nitrogen-containing compound as an electrification enhancer, it becomes possible to effectively impart an electric charge.
• the liquid contact method is not particularly limited as long as it can be effectively electretized.
• a method of contacting and passing a liquid in the thickness direction, then removing and drying is preferably used.
• the method of contacting and passing the liquid is not particularly limited as long as the desired effect can be obtained, but methods such as injection, injection, condensation, and suction can be used. Heating using suction, atmospheric pressure reduction, heat, electromagnetic waves, or the like can be used.
• a combination of spraying, vacuum and drying is preferred as a continuous process step.
• each treatment of the liquid contact method is shown below.
• the material to be charged is a fibrous material such as non-woven fabric
• the fibrous material is placed on a mesh support having an air permeability of 50 to 400 cm 3 /cm 2 /sec, and water is sprayed from above.
• the air permeability can be measured using a frandil type tester described in JIS L1096.
• the above-mentioned net-like support is specifically a porous structure made of a fabric of metal yarn or plastic yarn, and includes woven shapes such as plain weave, twill weave, and satin weave.
• metal materials include stainless steel and bronze
• plastic materials include polypropylene, polyester, polyurethane, nylon, and polyphenylene sulfide.
• water is jetted from a nozzle placed several cm above the object to be charged at a pressure sufficient to wash and pass the water in the thickness direction.
• Sufficient pressure is not specified, but varies depending on the shape of the nozzle hole, the basis weight of the charged body, and the manufacturing method.
• the fibrous material to be charged is, for example, a polyolefin melt-blown nonwoven fabric with a basis weight of 5 to 50 g/m 2 , 0.3 to 3 MPa, for a polyolefin melt blown nonwoven fabric of 50 to 200 g/m 2 , It is preferably ⁇ 4 MPa. If the injection pressure is too high, pinholes and breaks will occur. On the other hand, if the pressure is too low, sufficient water cannot pass through, resulting in insufficient electretization.
• An example of the nozzle is one in which holes with a diameter of 0.05 to 0.2 mm are arranged in one or more rows at a pitch of 0.5 to 3 mm.
• the net-like support is movable and the fibrous material can be conveyed in the longitudinal direction so that the jetting treatment can be continuously performed.
• the conveying speed is not particularly limited, but a preferable range is 1 to 100 m/min.
• the optimum number of injections and the treatment surface are not particularly limited because they depend on the basis weight and average fiber diameter of the fibrous material.
• the negative pressure during suction is not particularly limited, but is preferably -0.01 to -0.5 kPa, for example.
• water can effectively pass through the fibrous material and the amount of retained water can be reduced.
• the hot air drying method is preferable because continuous treatment is possible.
• the temperature must be such that the fibers do not melt or form a film. It is preferably 140° C. or lower, more preferably 120° C. or lower, and even more preferably 100° C. or lower.
• the water preferably used in the liquid contact method is not particularly limited as long as it can be effectively electretized, but it is preferably less inorganic salts and high boiling point organic substances, and ion exchange resins, reverse osmosis membranes, etc. It is particularly preferable to use one that has been used and highly purified.
• the pH can also be set in consideration of the solubility, charge polarity, amount of charge, etc., depending on the presence and properties of the zinc oxide particles and charge enhancer. Generally, the range of pH is 1-12, more preferably 2-11, still more preferably 3-10, and most preferably 4-9.
• the present invention by adding a nitrogen-containing compound as an electrification enhancer, electretization by a liquid contact method can be made effective.
• the content of the nitrogen-containing compound in the electret polyolefin resin composition is preferably 0.1 to 5% by mass, more preferably 0.5 to 3% by mass, and more preferably 0.75 to 1.5% by mass. 5% by weight is most preferred.
• two or more types of fibers are mixed in the electret, or when two or more types of resin are mixed in one fiber, it refers to the ratio of the nitrogen-containing compound contained in the polyolefin resin.
• the electret contains a resin other than polyolefin, it can be distinguished because the resin other than polyolefin dissolves in solvents and acid bases and has different dyeability, and quantitative methods such as DSC and NMR Even polyolefin resin can be distinguished. If the content of the nitrogen-containing compound is less than 0.1% by mass, the amount of charge is low, resulting in deterioration in filtration characteristics. will be
• the nitrogen-containing compound is not particularly limited as long as desired charging, processing, and mixing properties can be obtained, but it should be a hindered amine compound containing at least one of a 2,2,6,6-tetramethylpiperidine structure and a triazine structure. is preferred, and the hindered amine compound more preferably contains both a 2,2,6,6-tetramethylpiperidine structure and a triazine structure.
• the secondary nitrogen in the piperidine structure can be preferably used in any form such as NH, NOR, and NR.
• hindered amine compound examples include, but are not limited to, poly[ ⁇ 6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl ⁇ (2,2,6,6-tetramethyl-4-piperidyl)imino ⁇ hexamethylene ⁇ 2,2,6,6-tetramethyl-4-piperidyl)imino ⁇ ] (Kimasorb (registered trademark) 944LD, BASF Japan) ), dimethyl succinate-1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethyl-4-piperidine polycondensate (Tinuvin (registered trademark) 622LD, manufactured by BASF Japan), 2-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]-2-butylpropanedioate bis[1,2,2,6,6-pentamethyl-4-piperidinyl] (tinuvin (registered trademark
• Chimasorb (registered trademark) 944LD or Chimasorb (registered trademark) containing 2,2,6,6-tetramethylpiperidine structure and triazine structure 2020FD, SABO STAB (registered trademark) UV119 is preferably used.
• the hindered amine compound one type may be used alone, or two or more types may be used in combination.
• the above are examples, equivalent functions and structures may be reagents and industrial raw materials having
• additives such as dispersants and surfactants used to enhance the dispersibility and functionality of zinc oxide particles are water. It is preferable to reduce the elution with respect to, and it is also preferable to combine with the above nitrogen-containing compound. This is because having a polar group has affinity with zinc oxide particles, has compatibility with polyolefin resin, and enhances the hydrophilicity of the electret while maintaining charge stability. Hydrophilicity has a beneficial effect on charging efficiency in liquid contact methods and water-mediated functionalities such as antibacterial, antiviral, and antiallergenic properties.
• polymer having a triazine structure such as Kimasorb (registered trademark) 944LD, Kimasorb (registered trademark) 2020FD, SABO STAB (registered trademark) UV119, and the like. These can be added during masterbatch or compound production, or during molding into final shapes (eg, various fibrous materials).
• the present invention relates to an electret comprising a polyolefin resin containing zinc oxide particles, which may also include, for example, various crystal nucleating agents, fatty acid metal salts, hindered amines different from the above charge enhancers, hindered phenolic antioxidants, phosphorus Antioxidants such as antioxidants, sulfur antioxidants, UV absorbers, pigments, etc. may be added as necessary.
• various crystal nucleating agents such as sorbitol and trisamides, fatty acid magnesium, and fatty acid aluminum are effective in stabilizing the charge of the electret. can be suppressed.
• Addition of a lubricant component composed of fatty acid amide, fatty acid, fatty acid metal salt, and perfluoro derivative is also suitable for suppressing clumps adhering to the nozzle and clogging the nozzle when zinc oxide particles are mixed.
• the TSC (thermally stimulated current) method can be used to evaluate the charge stability of the electret. Specifically, (1) the compact is charged to form an electret. (2) Two electrodes are placed facing each other on both sides of the electret. (3) Connect a high-impedance picoammeter to the electrodes on both sides of the electret. (4) After being placed in a heating bath at 30° C. or lower and short-circuited, the temperature is raised from 25° C. at a rate of 5° C./min to the melting point of polyolefin, which has the highest melting point among the constituent materials of the electret, +10° C. or higher.
• the depolarization temperature of the TSC method is associated with the charge stability of the electret and the performance stability as a filter (for example, Osaka Institute of Technology Bulletin, 66 (1), 1-18, Japanese Patent No. 3199947, etc.).
• the inventors have also found that there is a correlation in charge stability between electrets obtained by the corona charging method used for the TSC method and electrets obtained by the liquid contact method.
• the corona discharge method is used to unevenly distribute the charges (amount and polarity) in the thickness direction so that a sufficient depolarizing current can be observed in the TSC method.
• the atmosphere and sample temperature during charging should be 30° C. or less so as not to affect the measurement results in the TSC method. Since the corona discharge method in the present invention is not intended for surface treatment such as oxidation or etching, it is essential that the equipment and conditions are used for manufacturing and researching electrets.
• the TSC method After performing the charging, start measurement by the TSC method within 10 minutes in an environment with an ambient temperature of 30°C or less.
• an electret that has undergone a history of transportation, storage, heating, etc. after production it is necessary to electretize the electret again by the above-described method in advance and measure it.
• the purpose of the evaluation by the TSC method in the present invention is to evaluate the intrinsic charge stability against heat of the molded product material, and to eliminate the effects of changes in the amount of charge due to various processes and the passage of time. That is, even if the fibrous material or laminate has undergone various histories (time, temperature, etc.), the electret portion can be separated, charged, and then subjected to TSC measurement. It is essential to evaluate In other words, having a high QF and the following a/b ratios are electrets and electret filters with good filtration properties and charge stability.
• a/b (/ is divided is preferably 0.3 or less, more preferably 0.2 or less, and most preferably 0.1 or less. It is important to use a reasonable value with continuity as the data for the maximum current value shown above. Judgment is made based on reasonable figures. If the current polarities are different between the maximum value up to 100° C. and the maximum value above 100° C., the absolute values of both are divided.
• the amount of depolarization charge is expressed as an a/b ratio, and it goes without saying that the amount of depolarization charge during corona charging is preferably large on the high temperature side.
• the depolarization current at 100°C or higher preferably has a peak temperature at which the maximum value and a start temperature are high and has a narrow half-value width.
• the peak temperature is 120°C or higher, more preferably 130°C or higher, and most preferably. 140° C. or higher.
• the rising temperature is preferably 80° C. or higher, more preferably 90° C. or higher, still more preferably 100° C. or higher, and most preferably 110° C. or higher.
• the rise temperature is obtained as the intersection of the tangents of the measured values before and after the peak.
• the electret of the present invention can be made into a molded body of any required shape, but a fibrous material is suitable for use.
• the fibrous materials include fibrous materials such as woven and knitted fabrics, non-woven fabrics, and cotton-like materials made of long fibers or short fibers, and fibrous materials obtained from stretched films, and have an appropriate shape and thickness depending on the application. can be molded into When the electret is used as a filter, it is most preferably a nonwoven fabric.
• Methods for obtaining nonwoven fabrics include a method of sheeting monocomponent fibers, composite fibers such as core-sheath fibers and side-by-side fibers, and short fibers such as split fibers by carding, airlaid, wet papermaking, etc., and a spunbond method using continuous fibers. , a melt blowing method, an electrospinning method, a force spinning method, a method of forming a sheet by a laser stretching method, and the like, and other conventionally known methods can be used.
• long-fiber nonwoven fabrics obtained by a meltblowing method, a melt electrospinning method, a melt force spinning method, a spunbond method, or a laser drawing method are more preferable for electret applications from the viewpoint of not using a spinning oil and a solvent.
• the average fiber diameter (diameter) of the fibers used in the fibrous material of the present invention is preferably 0.001 to 100 ⁇ m, more preferably 0.005 to 20 ⁇ m, and 0.01 to 10 ⁇ m. is more preferred, 0.02 to 5 ⁇ m is particularly preferred, and 0.03 to 3 ⁇ m is most preferred. If the average fiber diameter is larger than 100 ⁇ m, it is difficult to obtain a practical collection efficiency, and the efficiency is greatly reduced during charge decay. When the diameter of the fiber is smaller than 0.001 ⁇ m, it is difficult to impart an electric charge as an electret.
• the fibrous material in the present invention may be a uniform material made of a single manufacturing method and material, or a mixture of two or more materials with different manufacturing methods, materials and fiber diameters. At least a part of the portion having electret properties must be the composition of the present invention for manifestation of the properties.
• the electret of the present invention can be used together with other constituent members as necessary.
• the electret of the present invention is preferably used in combination with, for example, a prefilter layer, a fiber protection layer, a reinforcing member, or a functional fiber layer.
• An electret filter using the electret of the present invention is also included in the scope of the present invention.
• the collection properties of fine particles can also be used to evaluate the charge amount or charge stability of the electret.
• the liquid contact method is effective as an evaluation method when the uneven distribution of charges in the thickness direction is insufficient and direct evaluation by the TSC method is difficult.
• a filter medium quality factor (QF value) as a parameter related to the charge amount
• a method of evaluating charge stability uses the natural logarithmic ratio of transmittance before and after various treatments (herein referred to as performance maintenance ratio).
• the particles those artificially generated may be charged in equilibrium, or atmospheric dust may be used.
• concentration or number may be obtained.
• electrostatic attraction it is preferable that electrostatic attraction is dominant, and as an example, the passing wind speed is 10 cm / s, the pressure difference before and after the sample using a differential pressure gauge, and the diameter using a laser particle counter of 0.3 to 0.
• Particle transmittance [-] (particle number concentration on the downstream side of the sample) / (particle number concentration on the upstream side of the sample)
• Particle collection efficiency [%] (1-particle transmittance [-]) x 100
• Filter media quality factor (QF value) [mmAq -1 ] - (ln (particle permeability [-]) / (ventilation resistance [mmAq]))
• Performance retention rate [-] ln (particle transmittance after treatment [-]) / ln (particle transmittance before treatment [-])
• the value of the filter medium quality factor QF in the above is generally 0.1 or less when fibrous materials that have not been electretized are used.
• the electret is used as a filter, it is preferably 0.5 or more, more preferably 1.0 or more, still more preferably 1.1 or more, and most preferably 1.2 or more.
• the filter medium quality factor QF is maintained not only immediately after electretization but also after heat treatment.
• the electret of the present invention can have both the function of an electret and the function of zinc oxide particles, and is widely used as a fibrous material and a filter due to its functions such as dust collection, protection, ventilation, antifouling, and waterproofing. be able to.
• a fibrous material and a filter due to its functions such as dust collection, protection, ventilation, antifouling, and waterproofing.
• it can be used not only as a function of the zinc oxide particles alone, but also in an air conditioner combined with a discharge device, an electrostatic precipitator, a light irradiation device, or the like.
• Collection efficiency [%] (1-particle transmittance [-]) x 100 The value measured immediately after the sample was air-dried after charging was taken as the initial collection efficiency.
• QF value Frter material quality factor (QF value)
• QF value The QF value defined below was used as an index of the electret charge amount and filter performance.
• QF [mmAq -1 ] - (ln (particle permeability [-]) / (ventilation resistance [mmAq]) (particle transmittance)
• the sample was attached to an adapter, and the particle transmittance was calculated under the following conditions using a light scattering particle counter KC-01E manufactured by Rion.
• Particles to be evaluated Atmospheric dust particles Wind speed: 10 cm/s
• Efficiency calculation Particle number between 0.3 and 0.5 ⁇ m by light scattering counting method
• Particle transmittance [-] (particle number concentration on the downstream side of the sample) / (particle number concentration on the upstream side of the sample) (ventilation resistance)
• a sample was attached to an adapter, pipes connected to a differential pressure gauge were connected vertically, and ventilation was performed at 10 cm/s to measure airflow resistance (pressure loss) (mmAq) in a state without restriction.
• both electrodes are temporarily short-circuited to set the current value to zero.
• the horizontal axis is the temperature ° C.
• the vertical axis is the current value [-]
• the peak height at 50 to 100 ° C. is a
• the peak height at 100 ° C. to 180 ° C. is b
• average fiber diameter Using a scanning microscope, a plurality of images were obtained with a visual field size of 90 ⁇ m ⁇ 90 ⁇ m, and then 50 fiber diameters were measured so as not to overlap the same fibers. The average fiber diameter was calculated by geometrically averaging the obtained numerical values.
• antibacterial In the antibacterial test, the bacterial liquid absorption method in JIS L 1902 was used to evaluate against Staphylococcus aureus and Escherichia coli.
• Photoluminescence measurement Photoluminescence in the wavelength range of 350 to 700 nm was measured using a microphotoluminescence measuring device under the following conditions. Excitation light: 325 nm (laser), 3 ⁇ W Detector: CCD Measurement temperature: 25°C Objective lens: ⁇ 40
• Zinc oxide particles (b) photoluminescence measurement was performed on a masterbatch in which zinc oxide particles (b) (average particle size 0.8 ⁇ m) were dispersed in polypropylene at a content of 20% by mass.
• the ratio B/A between the photoluminescence intensity A in the wavelength range of 350 nm to 400 nm and the photoluminescence intensity B in the wavelength range of 500 nm to 700 nm was 0.094.
• Example 1> For polypropylene homopolymer of MFR 1300, using the masterbatch of (2) above, zinc oxide particles (a) 0.25% by mass (2.5% by mass as a masterbatch), Chimasorb (registered trademark) 944LD (BASF Japan) (manufacturer) and 0.075% by mass of magnesium stearate were added, and a filament nonwoven fabric having a basis weight of 30 g/m 2 and an average fiber diameter of 3.0 ⁇ m was obtained using a meltblowing apparatus.
• zinc oxide particles (a) 0.25% by mass (2.5% by mass as a masterbatch), Chimasorb (registered trademark) 944LD (BASF Japan) (manufacturer) and 0.075% by mass of magnesium stearate were added, and a filament nonwoven fabric having a basis weight of 30 g/m 2 and an average fiber diameter of 3.0 ⁇ m was obtained using a meltblowing apparatus.
• the obtained nonwoven fabric was placed on a mesh support, and ion-exchanged water having a pH of 6.7 and an electrical conductivity of 0.8 ⁇ S/cm was applied from a nozzle with a diameter of 0.1 mm ⁇ and a pitch of 0.6 mm positioned 2 cm above the support at a pressure of 1 MPa. It was ejected under pressure.
• the sheet was conveyed at a speed of 4 m/min while the pressure was kept under the mesh support just below the nozzle, and the front and back sides of the sheet were treated once each. Then, it was air-dried at 25° C. for 2 hours to form an electret.
• the initial collection efficiency was 99.997%
• the QF value was 1.79
• the performance maintenance rate was 0.90
• the a/b value was 0.04 in the depolarization current measurement by the TSC method
• the maximum peak temperature was 143°C.
• the antibacterial activity value was 5 or more in logarithmic value for any bacterial species, which was the upper limit value for evaluation.
• Example 2 Using the same raw materials and proportions as in Example 1, a melt-blowing apparatus was used to obtain a long-fiber nonwoven fabric having a basis weight of 18 g/m 2 and an average fiber diameter of 2.5 ⁇ m. On the other hand, electretization was performed in the same manner as in Example 1. Initial collection efficiency 99.992%, QF value 1.51, performance maintenance rate 0.88, a/b value 0.04 in depolarization current measurement by TSC method, maximum value of depolarization after 100 ° C. The peak temperature was 144°C. In addition, the antibacterial activity value was 5 or more in logarithmic value for any bacterial species, which was the upper limit value for evaluation.
• Example 3 The same as Example 2 except that the concentration of zinc oxide particles (a) was 1% by mass using the masterbatch of (2) above, and a melt blowing apparatus was used to produce a basis weight of 18 g/m 2 and an average fiber diameter of 2.6 ⁇ m. A long fiber nonwoven fabric was obtained.
• electretization was performed in the same manner as in Example 1. Initial collection efficiency 99.99%, QF value 1.53, performance retention rate 0.86, a/b value 0.06 in depolarization current measurement by TSC method, peak indicating maximum depolarization after 100 ° C The temperature was 143°C.
• the antibacterial activity value was 5 or more in logarithmic value for any bacterial species, which was the upper limit value for evaluation.
• Example 4 The same as Example 2 except that the concentration of the zinc oxide particles (a) was changed to 5% by mass using the masterbatch of ( 2 ) above. to obtain a long fiber nonwoven fabric.
• electretization was performed in the same manner as in Example 1.
• the antibacterial activity value was 5 or more in logarithmic value for any bacterial species, which was the upper limit value for evaluation.
• Example 5 The zinc oxide particles (a) had a particle diameter of 0.3 ⁇ m, and were added after preparation of a 10 % by mass masterbatch. A 6 ⁇ m long fiber nonwoven fabric was obtained. On the other hand, electretization was performed in the same manner as in Example 1. Initial collection efficiency 99.99%, QF value 1.48, performance maintenance rate 0.88, a/b value 0.04 in depolarization current measurement by TSC method, maximum value of depolarization after 100 ° C. The peak temperature was 140°C. In addition, the antibacterial activity value was 5 or more in logarithmic value for any bacterial species, which was the upper limit value for evaluation.
• Example 1 A long-fiber nonwoven fabric having a basis weight of 18 g/m 2 and an average fiber diameter of 2.5 ⁇ m was obtained using a meltblowing apparatus in the same manner as in Example 2 except that the masterbatch of (3) was used.
• Initial collection efficiency 99.95%, QF value 1.25, performance retention rate at 100 ° C. 0.68, a / b value in depolarization current measurement by TSC method 1.01, maximum value of depolarization after 100 ° C. was a peak temperature of 130°C.
• the antibacterial activity value was 5 or more in terms of logarithmic value for any bacterial species, which was the upper limit value for evaluation.
• Comparative Example 2 The same as Comparative Example 1 except that the masterbatch of (3) above was used and the concentration of the zinc oxide particles ( b ) was 1% by mass. A fibrous nonwoven fabric was obtained. On the other hand, electretization was performed in the same manner as in Example 1. Initial collection efficiency 99.8%, QF value 1.03, performance retention rate at 100 ° C. 0.58, a / b value 1.87 in depolarization current measurement by TSC method, maximum depolarization after 100 ° C. The peak temperature indicating the value was 128°C. In addition, the antibacterial activity value was 5 or more in logarithmic value for any bacterial species, which was the upper limit value for evaluation.
• Example 3 A long-fiber nonwoven fabric having a basis weight of 30 g/m 2 and an average fiber diameter of 2.5 ⁇ m was obtained using a meltblowing apparatus in the same manner as in Example 1 except that no zinc oxide particles were added. On the other hand, electretization was performed in the same manner as in Example 1. Initial collection efficiency 99.993%, QF value 1.53, performance maintenance rate 0.90, a/b value 0.03 in depolarization current measurement by TSC method, maximum depolarization after 100 ° C. The peak temperature was 144°C. In addition, the antibacterial activity value was 1 or less in logarithmic value for any bacterial species, and no effective antibacterial activity was obtained.
• the composition with a small a/b value has a high filter performance retention rate when charged with a liquid, and the use of zinc oxide particles with a small B/A value provides an excellent QF value.
• the a/b value which is a charge stability index, is small, and the filter performance retention rate is excellent even in the electret by liquid charging.
• the particle collection efficiency as a filter and the quality factor of the filter medium at the initial stage and after the heat load are both high, and they have excellent properties as an electret filter.
• it is compatible with the functionality of the zinc oxide particles.

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