JP2002201303A - Porous sheet material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a porous sheet material having fine and uniform pores, capable of being thinned and diversified, applicable to various fields and uses. SOLUTION: This porous sheet material is obtained by mixing a polar solvent-soluble polymer material with a powdery inorganic material in the ratio of 30-500 pts.wt. of the powdery inorganic material to 100 pts.wt. of the polar solvent-soluble polymer material and has open pores with <=10 μm average pore diameters in the sheet material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel porous sheet material, such as paper, nonwoven fabric, or perforated film, which is different from conventional thin-leaf porous materials. Protective clothing, roofing, flooring, wall materials, ceiling materials, roofing materials, concrete curing, waste material coating, etc. The present invention relates to a porous material used for a filter medium, a base material for a cleaning roll of a copying machine, an electrode of a battery, a separator, and the like.

[0002]

2. Description of the Related Art As a porous sheet material having continuous pores, paper, a nonwoven fabric, a perforated film and the like are conventionally known. Such porous sheet materials include clothing, building materials,
It is used in various fields such as industrial materials. The reason is that since these porous sheet materials are thin leaf-shaped, they are easy to process and handle such as impregnation, lamination, and sticking, and various functions caused by the pores in the porous sheet material have been used in various fields. This is because it contributes to improvement of required performance. Here, the various functions caused by the pores include, for example, moisture permeability and water pressure resistance in a moisture-permeable waterproof clothing, particle trapping property in a filter medium, a surface material and a base material of a polymer foam such as polyvinyl chloride and polyurethane. Liquid permeability and gas permeability of the resin in the laminated material for building, oil permeability in the cleaning roll of copying machine, etc., permeability, shielding property, filtration property, retention property, absorption property of various properties And so on.

[0003] Here, as the pore size increases, the permeability increases, but the shielding property, filtration property, retention property and absorption property decrease. For example, an increase in permeability is a preferable phenomenon in terms of suppressing a pressure loss in a filter medium, but has a drawback that filterability, that is, trapping of particles is reduced. Therefore, such a change in function due to an increase in pore size is not a preferable phenomenon in many fields including the above-mentioned applications.

Since the above function largely depends on the size and distribution of the pores in the porous material, it is important to control them in order to improve the performance and stabilize the quality. In other words, a porous sheet material with smaller and more uniform pores is desired.

[0005] In addition, various functions caused by pores are not enough to cope with various fields.
It is required for a porous sheet material to provide various functions such as catalytic activity, water repellency, conductivity, flame retardancy, heat resistance, and sinterability (multifunctionalization).

[0006]

[0005] Paper and nonwoven fabrics are obtained by opening and dispersing fibrous materials such as pulp, organic fibers, and inorganic fibers by stirring or carding in water, depositing them on a paper net or a conveyor belt. Pressing is performed in accordance with the above, mechanically or chemically entangled, and formed into a sheet shape, thereby manufacturing. Since paper and nonwoven fabric are aggregates on which fibers are deposited, the size of pores is governed by the thickness of the deposited fibers and the thickness of the fibers. Accordingly, the control of the pores is performed in principle by the thickness, the press, and the fiber diameter, but is generally performed by adjusting the fiber diameter in terms of increasing the voids and reducing the thickness.

That is, thin fibers are used to reduce pores, and thick fibers are used to increase pores. The limitation of fiberizing techniques, for example because the following fine fibers manufacturing is difficult as 1 [mu] m, has the disadvantage that 10 ⁰ [mu] m order following a small pore formation is difficult. Also, there is a limit to the thinning technique, and the thickness is, for example, 100
When the thickness is less than μm, the above-mentioned limit of the reduction in the diameter of the fiber is added, and the accumulation and entanglement of the fibers become insufficient. In addition, there is a limit in uniformly depositing the fibers, and the fibers are liable to be rough and dense, and the pore distribution is widened.

On the other hand, a perforated film is produced by utilizing a phase separation of a polymer solution and / or by mixing a polymer melt with a lubricant or an inorganic filler to form a film and stretching the film. It is used for reverse osmosis membranes, ultrafiltration membranes, microfiltration membranes, etc. Since such a film is produced by coating or extrusion, a thin and uniform sheet can be obtained.In addition, pore formation is caused by evaporation of a solvent in a polymer melt or replacement with a non-solvent. It is easy to obtain a porous film.

As described above, a perforated film is excellent in terms of thinning and imparting various functions caused by pores, but there are the following problems in coping with the aforementioned multifunctionalization.

[0010] For example, as one means for achieving multifunctionality, there is a method of mixing a powdery inorganic material having various functions into a matrix at a high rate. However, in the case of the stretching method typified by polytetrafluoroethylene (PTFE) or polyethylene, if the powdered inorganic material is mixed at a high rate, the film strength is reduced, and it is difficult to control the stretching appropriately for pore formation. However, it is difficult to form fine and uniform pores. In addition, according to the stretching method, pores are formed after the film is formed. Therefore, when the film is combined with a porous substrate such as a nonwoven fabric, the film is compression-bonded at a heat deformation temperature or near a melting point according to the material. Need to be done. However, since the pores in the film are destroyed due to deformation during thermocompression bonding, it is difficult to bury the film in a porous substrate, and there has been a drawback that the means of compounding is limited to lamination.

As for the wet coagulation method represented by polyurethane, there is an example in which a powdery inorganic material such as silica or alumina is added to apply to a moisture-permeable waterproof clothing. But,
Since the mixing ratio of the powdered inorganic material is too small, its function is hardly exerted sufficiently, and it has hardly been developed for various uses other than clothing in terms of multifunctionality.

The present invention has been made in view of the above problems of the prior art, and has as its object to provide a porous sheet material which has uniform pores, is thin and multifunctional, and is applicable to various fields and applications. And

[0013]

According to a first aspect of the present invention, there is provided a porous sheet material comprising a polar solvent-soluble polymer material mixed with a powdered inorganic material to achieve the above object. The polar solvent-soluble polymer material 100
The powdered inorganic material is mixed at a ratio of 30 to 500 parts by weight with respect to parts by weight, and an average pore diameter in the sheet material is 10%.
It has continuous pores of not more than μm.

The mixing ratio of the powdered inorganic material is 50 to 3 with respect to 100 parts by weight of the polar solvent-soluble polymer material.
00 parts by weight, and the average pore diameter of the continuous pores is 1
It is preferably not more than μm (claim 2).

As the powdered inorganic material, one or more selected from the group consisting of porous materials having pores, clay compounds, materials having catalytic activity, and hydrophobic silica can be used ( Claim 3).

The polar solvent-soluble polymer material includes:
Polyurethane, polyether sulfone, polysulfone,
One or more selected from the group consisting of polyamide and polyester can be used (claim 4).

The thickness of the porous sheet material is 100 μm.
m or less (claim 5).

[0018] The composite porous material according to claim 6 is characterized in that:
5. The porous sheet material according to any one of the items 5 is attached or embedded in at least a part of a porous substrate selected from the group consisting of paper, nonwoven fabric, woven fabric, and knitted fabric.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Configuration of Porous Sheet Material and Composite Porous Sheet Material The porous sheet material of the present invention is prepared by adding a powder to a polar solvent-soluble polymer material in order to solve the above-mentioned problems in conventional paper, nonwoven fabric, and perforated film. By adding and mixing the powdered inorganic material at a relatively high rate, fine and uniform pores are formed in the obtained mixed sheet, and the characteristics and functions of the powdered inorganic material are exhibited. Is what you do.

In other words, the present inventor has found that when a powdered inorganic material is mixed with a polar solvent-soluble polymer material at a high rate, not only the material inherently exhibits functions such as adsorptivity and decomposition performance, but also the polymer It has been found that pores smaller and more uniform than the pores obtained with the material alone are formed. From this viewpoint, as a result of diligent studies on the formation of small pores, thinning, and multi-functionalization, the polar solvent-soluble polymer material 100
It was determined that 30 to 500 parts by weight of a powdery inorganic material was mixed with respect to parts by weight, and that the above object could be achieved when continuous pores having a pore size of 10 μm or less were formed in the obtained mixed sheet. It has been reached.

Examples of the powdery inorganic material used in the present invention include: calcium carbonate; talc; silica; alumina; calcium silicates such as the zonotlite family;
Activated carbon, zeolite, crystalline aluminophosphate type molecular sieve, silica gel, diatomaceous earth, palygoskite,
Porous inorganic particles having micropores in particles such as sepiolite; montmorillonite, bentonite, smectite,
Clay compounds such as vermiculite and kanemite; silica particles having a hydrophobic surface; particles having catalytic activity such as titanium oxide and manganese oxide; aluminum hydroxide;
Those having a particulate form including whiskers in the form of fine short fibers such as magnesium hydroxide and potassium titanate are exemplified.

The particle size of the powdery inorganic material suitable for use depends on the application and is not particularly limited, but is usually 10 ^-2.
It is preferably on the order of 10 to 10 ¹ μm. As a specific example, for example, when used for filter media,
About 300 mesh pass with Tyler mesh (about 44m
μ) is preferred.

The polar solvent-soluble polymer material used in the present invention is soluble in a polar solvent such as N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, tetrahydrofuran, dioxane, N-methylpyrrolidone. If it is not particularly limited, for example, polyurethane resin, polyacrylate, acrylic resin such as polyacrylonitrile, polyvinyl chloride, polyvinyl acetate, vinyl resin such as polyvinyl fluoride, epoxy resin, polysulfone And polyethersulfone, phenolic resin, polystyrene, polyamide, polyester, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, fluorine and silicone derivatives thereof.

In the present invention, other additives can be used as needed. Examples include inorganic fibers such as short fibrous slag fibers, ceramic fibers, glass fibers, carbon fibers, and activated carbon fibers, and water repellents such as silicones, fluorocarbons, long-chain fatty acid salts, and long-chain amine salts. And / or oil repellents, surfactants, metal salts and the like.

The mixing ratio of the powdered inorganic material to the polar solvent-soluble polymer material is 30 to 30 parts by weight per 100 parts by weight of the polar solvent-soluble polymer material.
It must be 500 parts by weight. If the amount of the powdered inorganic material is less than 30 parts by weight, pores in the film are likely to be large and nonuniform. As a result, various functions are reduced or fluctuated due to the pores, and the content of the powdered inorganic material is reduced, so that the functions cannot be sufficiently exhibited. On the other hand, when the amount exceeds 500 parts by weight, the content of the polar solvent-soluble polymer material is reduced, so that the mechanical strength is reduced and the workability of pleats, corrugates and the like is reduced.

The mixing ratio depends on the use of the porous sheet material and the type of the resin, but is preferably 50 to 300 parts by weight, more preferably 100 to 300 parts by weight. When pores are formed by the wet coagulation method, macropores are generally formed, but 50 to 100 parts by weight or more of the powdery inorganic material is used.
Mixing in the range of 00 parts by weight makes it difficult to form the macropores, and further promotes the reduction of pores and the uniformity of the pore diameter.

Although the thickness of the porous sheet material of the mixture of the polar solvent-soluble polymer material and the powdered inorganic material is not particularly limited, it is easy to perform various processes such as impregnation, lamination, pleating and corrugating. In this respect, the thickness is preferably 100 μm or less, and more preferably 50 μm or less.

Next, the composite porous sheet material of the present invention comprises:
A layer made of a mixture of the above-mentioned polar solvent-soluble polymer material and a powdery inorganic material is provided or embedded in at least a part of a porous substrate described later. The attachment or embedding may be performed on the entire area of the porous base material, may be performed on a part thereof, may be provided on one surface, or may be embedded inside. The amount of the mixture adhering to the porous substrate is not particularly limited, but is preferably 10 g / m ² or more in terms of solid content. If it is less than 10 g / m ² , the content is too small, and the pores of the porous substrate cannot be reduced, and the function of the powdery inorganic material is hardly exhibited.

The porous substrate on which the mixture layer is provided or embedded is made of natural or synthetic pulp; organic fibers such as nylon, polyolefin, and aramid; and inorganic fibers such as glassy, carbonaceous, and alumina / silica. Further, paper, non-woven fabric, woven fabric, knitted fabric or the like may be any porous sheet-like material, and is not particularly limited. Examples include pulp or various fibers and powders. Nonwoven fabrics, woven fabrics, knitted fabrics, etc. made by various dry methods such as wet method of dispersing paper and short fibers in water and forming web, card type, air lay type, spun bond type, melt blown type is there. The thickness, basis weight, fiber type and shape of the porous substrate are not particularly limited.

The average pore diameter in the present invention is determined by image analysis of a SEM image of a longitudinal section of the porous sheet layer.
It is represented by the number average value of the values calculated as the equivalent circle diameter after the binarization processing. If the value exceeds 10 μm, large pores comparable to paper or nonwoven fabric will result, and various functions due to the pores will be reduced. In terms of improvement of the above-mentioned various functions, the average pore diameter is more preferably 1 μm or less.

2. Method for Producing Porous Sheet Material and Composite Porous Sheet Material The porous sheet material of the present invention is obtained by mixing a polymer dissolved in a polar solvent and a powdered inorganic material, forming a film of the resulting mixed slurry, and forming a sheet. It is obtained by making things. More specifically, coating the mixed slurry on a non-porous sheet substrate such as a polyester film, forming a film by a wet coagulation method or evaporating a solvent to an external atmosphere, drying, and then peeling the film. It is manufactured by

A composite porous sheet material is produced by attaching or embedding the obtained membrane to a porous substrate such as the above-mentioned paper, nonwoven fabric, woven fabric, or knitted fabric, if necessary. Specifically, for example, the above-mentioned film is laminated on a porous substrate to form a composite. Alternatively, the slurry is applied and / or impregnated on a porous substrate sheet, and a film is formed on the surface or inside of the substrate sheet by a wet coagulation method, evaporation of a solvent to an external atmosphere, or the like, followed by drying.

The pores of the mixture layer formed by mixing the polar solvent-soluble polymer material and the powdered inorganic material are gaps between the particles and / or the polymer, so that the particles can be made smaller and mixed at a high rate. By this, the gap in the mixed layer,
That is, the pores can be made smaller. Therefore, the pores in the mixed layer are small pores having less macropores than the polymer alone, are significantly smaller than paper or nonwoven fabric alone, and have fewer macropores unique to the conventional polyurethane film. Therefore, various functions caused by the pores can be improved.

3. Applications of Porous Sheet Material When the porous sheet material of the present invention is embedded near the surface of the nonwoven fabric and unevenly distributed, the macroporous layer of the nonwoven fabric and the microporous layer (microporous layer) of the mixture layer are different. They can coexist. Therefore, for example, when activated carbon of porous particles is used as the powdered inorganic material and applied to the media of an air filter, arranging the nonwoven fabric surface on the upstream side can promote deep-layer filtration. It is possible to suppress an increase in loss, improve the life, and simultaneously remove odors. On the other hand, if the microporous layer is arranged on the upstream side, the surface filtration is promoted, so that it is suitable for a filter bug that is used by mechanically removing the particle layer deposited on the surface.

When the porous sheet material is used alone and used as a gas adsorption filter formed in a honeycomb or corrugated shape, the porous sheet material of the present invention has smaller pores than paper or nonwoven fabric. Can be formed to be thinner while maintaining the above, so that the porosity of the honeycomb structure can be increased, or the cell can be reduced, so that the surface area of the sheet material per unit volume can be increased. it can. Further, since the gas permeability is superior to that of a non-porous film, not only the surface of the film but also the surface of micropores inside the film can be used. Therefore, the contact area with the gas is increased, and the filter performance and the adsorption performance can be improved. That is, when a powdery inorganic material that adsorbs or decomposes organic substances is contained in the microporous layer,
It is possible to remove not only odors and harmful substances but also an improvement in trapping rate, low pressure loss and long life. Therefore, it can be widely used as various filter media for purifying air and water, removing moisture and odors, and recovering solvents.

Other uses include lining materials for moisture-permeable waterproof clothing, skin or lining materials for dustproof / protective clothing, roofing, flooring materials, wall materials, ceiling materials, surface materials for various foam boards,
Laminated materials for construction and civil engineering used for curing concrete and covering waste, filter media used for deodorizing / dehumidifying equipment, water purification equipment, wastewater treatment equipment, etc., base materials for heat exchangers, copiers Cleaning roll substrate, battery electrode, separator and the like.

[0037]

[Example 1] Polyurethane dissolved in N, N-dimethylformamide and silica having a particle size of 0.1 μm or less whose surface was hydrophobized were mixed in a solid content ratio of the former 1
The mixture was mixed at a ratio of 50 parts by weight to 00 parts by weight to prepare a mixed slurry. After coating this mixed slurry on a polyester film, a microporous film is formed based on a wet coagulation method, and after drying, the coating layer is peeled off from the polyester film to a thickness of 30 μm.
The porous sheet material used for the moisture-permeable waterproof clothing was obtained.

Example 2 The polyurethane dissolved in N, N-dimethylformamide and the activated carbon powder having a particle size of 300 mesh pass were in a solid content ratio of 200 parts by weight to 100 parts by weight of the former. To prepare a mixed slurry. This mixed slurry was coated on a polyester nonwoven fabric having a basis weight of 500 g / m ² manufactured by the needle punching method so as to have a solid content of 50 g / m ^2, and then processed based on the wet coagulation method under the same conditions as in Example 1. Thus, a composite porous sheet material used for a filter medium having a microporous membrane attached to the surface of the nonwoven fabric and its vicinity was obtained.

[Comparative Example 1] The same polyurethane as used in Example 1 was used as a polyurethane dissolved in N, N-dimethylformamide and silica having a hydrophobic particle surface.
The mixed slurry was prepared by mixing so that the former was 100 parts by weight and the latter was 10 parts by weight in terms of solid content ratio. After coating this mixed slurry on a polyester film, a microporous film was formed based on the wet coagulation method under the same conditions as in Examples 1 and 2, and after drying, the coating layer was peeled off from the polyester film to form a 30 μm thick transparent film. A porous sheet material used for wet waterproof clothing was obtained.

Comparative Example 2 The same conditions as in Example 2 were used except that the activated carbon powder was not mixed, and a single slurry of polyurethane dissolved in N, N-dimethylformamide was prepared by a needle punching method to a weight of 500 g.
/ ^{M 2} of on a polyester nonwoven fabric with solids 50 g / ^{m 2}
After coating, the coating was treated based on the wet coagulation method under the same conditions as in Examples 1 and 2, to obtain a porous sheet material used for a filter medium in which the powdered inorganic material was not mixed near the surface of the nonwoven fabric.

The physical properties of the porous sheet materials obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were measured under the following conditions. Table 1 shows the results.

[0042]

[Table 1]

[Average pore diameter and pore shape] The average pore diameter is obtained by analyzing the SEM image of the longitudinal section of the porous sheet layer, performing binarization processing, and calculating the number average value of the values calculated as the circle equivalent diameter. I asked. The case where pores having a pore diameter of 10 μm or more existed was determined as “non-uniform”, and the case where they did not exist was regarded as “uniform”.

[Hydraulic pressure resistance] Measured according to JIS L1092.

[Moisture permeability] JIS L1099 (A-1)
Method).

[Deodorization rate] Toluene concentration was 300 ppm
Each of the porous sheet materials of Example 2 and Comparative Example 2 cut into a circle having a diameter of 9 cm was individually enclosed in a 1000 cc container adjusted so as to be as follows. Next, the toluene concentration in the container before and 1 hour after the sample was sealed was measured with a detector tube, and the deodorization rate was calculated by the following equation.

[0047]

(Equation 1)

[Capture rate and pressure loss] JIS B99
In accordance with No. 21, the capture rate of 1 μm dust and the pressure loss at a wind speed of 3 m / min were measured.

[Water repellency] Measured in accordance with JIS L1092.

Rank 1: The entire surface is wet. Rank 4: The surface is not wet, but small water droplets adhere.

As can be seen from Table 1, the porous sheet material and the composite porous sheet material of the present invention have a smaller pore size than the comparative example in which the powdered inorganic material is not added or a small amount is added. And it was uniform. Then, the sheet was a thin sheet in which functions caused by pores such as moisture permeability, water pressure resistance, and particle trapping property and functions of a powdery inorganic material such as deodorization and water repellency were sufficiently exhibited.

[0052]

The porous sheet material of the present invention is obtained by mixing a powdery inorganic material having various functions with a polar solvent-soluble polymer material at a high addition rate, and the resulting porous sheet material is made of paper. It has small and uniform pores as compared to nonwoven fabrics, woven fabrics and perforated films. And, along with various functions caused by pores such as permeability, filtration, shielding, liquid absorption, liquid retention, adsorption, decomposability, water repellency, conductivity,
It becomes possible to exhibit the functions of the powdery inorganic material such as sinterability and catalyst. Further, it is possible to form pores having an average pore diameter of 10 μm or less, which are impossible with a nonwoven fabric, and to reduce the thickness to several tens of μm or less.

Further, the composite porous sheet of the present invention can be embedded in various base material sheets without destroying pores, which was impossible with a perforated film by a stretching method. Excellent. Therefore, it can be applied to various fields such as clothing, building materials, and industrial materials.

Claims (6)

[Claims] 1. A porous sheet material comprising a polar solvent-soluble polymer material mixed with a powdered inorganic material, wherein the powdered inorganic material is 30 to 500 parts by weight per 100 parts by weight of the polar solvent-soluble polymer material. A porous sheet material which is mixed in parts by weight and has continuous pores having an average pore size of 10 μm or less in the sheet material. 2. The mixing ratio of the powdered inorganic material is 50 to 3 with respect to 100 parts by weight of the polar solvent-soluble polymer material.
00 parts by weight, and the average pore diameter of the continuous pores is 1
The porous sheet material according to claim 1, wherein the thickness is not more than μm. 3. The powdery inorganic material is one or more selected from the group consisting of a porous material having pores, a clay compound, a material having catalytic activity, and hydrophobic silica. The porous sheet material according to claim 1 or 2, wherein 4. The polar solvent-soluble polymer material is one or two selected from the group consisting of polyurethane, polyether sulfone, polysulfone, polyamide and polyester.
The porous sheet material according to claim 1, wherein the material is at least one kind. 5. The porous sheet material according to claim 1, having a thickness of 100 μm or less. 6. The porous sheet material according to claim 1, which is provided on at least a part of a porous substrate selected from the group consisting of paper, nonwoven fabric, woven fabric and knitted fabric. Or a composite porous sheet material embedded therein.