JP2014005365A - Production method of porous materials, three-dimensional reticulated porous materials, liquid filters and liquid-absorbing sponges - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing three-dimensional reticulated porous materials consisting of thermoplastic elastomer having little influence on work environments or on cost increase, and allowing safe, easy, and stable production of homogeneous porous materials, three-dimensional reticulated porous materials produced by the method, and liquid filters with a superior filtration performance and liquid-absorbing sponge with superior liquid-absorbing ability with the use of the three-dimensional reticulated porous materials.SOLUTION: To provide a method for producing porous materials including the steps of: defoarming and molding a mixture consisting of thermoplastic elastomers, inorganic salt particles, and polyalcohols; solidifying the molded product; and performing aqueous extraction and drying of the inorganic salt particles in which the proportion of the polyalcohols in the composition is equal to or greater than 55 mass% with respect to the maximum proportion of the polyalcohols that are homogeneously mixed with the thermoplastic elastomers in the event of the thermofusion of the thermoplastic elastomers, three-dimensional reticulated porous materials produced by the method, and liquid filters and liquid-absorbing sponges with the use of the three-dimensional reticulated porous materials.

Description

  The present invention relates to a method for producing a three-dimensional network porous body made of a thermoplastic polymer. The present invention also relates to a three-dimensional network porous body that can be produced by the production method described above. The present invention further relates to a liquid filter using the three-dimensional network porous body, and a liquid absorbing sponge such as a liquid draining sponge or a squeezing sponge.

  A three-dimensional network porous body made of a thermoplastic polymer is generally lightweight. Also, functions such as permeating liquid and gas, absorbing liquid, discharging absorbed liquid by external force, storing absorbed liquid, absorbing sound, sorting solid by its diameter, absorbing impact, etc. Excellent. Therefore, it is used for ink rolls, penetrating marks, brush pens, filters, cosmetic sponges, and the like.

  Such a three-dimensional network porous body can be produced by various methods as described below. For example, in Non-Patent Document 1, a polyurethane foam formed of cells having a skeleton and a thin film is formed by chemical foaming using polyol, isocyanate, water or the like as a raw material, and this film is treated with an alkali treatment method or a heat treatment method. A method for producing a three-dimensional network porous body by removing the layer by means of a method is disclosed.

  In Patent Document 1, water-soluble inorganic salt particles, polyurethane resin and a solvent are kneaded and molded, and then the solvent is desolvated and coagulated in water, and the inorganic salt particles are removed from the molded body by water extraction. Thus, a cosmetic sponge having a three-dimensional network structure is obtained.

  Further, in Patent Document 2, polyurethane, a solvent, and calcium chloride as a pore forming agent are kneaded to form a clay-like compatible material, which is solidified in water, and calcium chloride is added to water. It is described that a three-dimensional network-like continuous pore elastic body is obtained by extraction and removal.

  Further, in Patent Document 3, after kneading a water-soluble organic particle pore-forming agent (a pore-forming agent) into an olefinic thermoplastic resin, at least a part of the obtained molded product is higher than the melting point of the resin. It is described that a three-dimensional network-like porous body can be obtained by immersing in a liquid at a temperature and then eluting the pores with an aqueous solvent.

  However, the polyurethane foam produced by the chemical foaming method described in Non-Patent Document 1 is a porous body mainly composed of bubbles having a diameter of 200 μm or more, and is small applied to a liquid filter, a liquid absorbent sponge, or the like. It is difficult to produce a porous body mainly composed of bubbles by this production method.

  In the production methods described in Patent Document 1 and Patent Document 2, a solvent having compatibility with water, such as dimethylformamide, is used. This solvent causes problems in the working environment, so it is difficult to use and waste liquid treatment becomes a problem. In order to treat a waste liquid such as dimethylformamide, treatment such as biological treatment and thermal catalytic oxidation is required, and detoxification treatment is expensive. Furthermore, the production method described in Patent Document 1 requires a special mold that can permeate the solvent and water, and it takes time until demolding. Therefore, there is a problem that a large number of molds are required for mass production. In the production method described in Patent Document 2, it is difficult to control the pore diameter of the porous body, and it is difficult to stably produce a porous body having a desired pore diameter.

  The manufacturing method of Patent Document 3 includes a step of immersing the kneaded molded product in a liquid having a temperature higher than the melting point of the resin after obtaining the kneaded molded product. . That is, it is a time-consuming and dangerous method, and increases the cost because the number of steps increases. Furthermore, depending on the conditions at the time of immersion, there may be a difference in the pore structure due to the difference between the vicinity of the surface of the porous body and the inside or the location of the surface.

Japanese Patent No. 4588357 Japanese Patent No. 3935907 JP 2008-24899 A

Keiji Iwata "Polyurethane resin handbook", published on September 25, 1987, P170, published by Nikkan Kogyo Shimbun

  The present invention has been made in view of such circumstances, and is made of a thermoplastic elastomer such as urethane, and is applied to a liquid-absorbing sponge, for example, 50 μm or less, or a liquid filter, for example, 10 μm or less. Is a method of manufacturing a porous body of a three-dimensional network (structure) mainly composed of small bubbles, which has less problems such as impact on the working environment and cost increase, and makes a homogeneous porous body safe and easy It is an object to provide a method that can be stably manufactured.

  Another object of the present invention is to provide a three-dimensional network porous body obtained by the above method.

  The present invention further provides a highly permeable liquid filter comprising the three-dimensional network porous material, such as a liquid filter capable of filtering fine particles having a particle size in the range of 1 to 10 μm in a short time with a low pressure loss. It is an issue to provide.

  It is another object of the present invention to provide a liquid-absorbing sponge, such as a draining sponge or a squeezed sponge, which is made of the three-dimensional network porous body and has excellent liquid-absorbing properties and properties of discharging the liquid that has been absorbed. .

  As a result of extensive research, the present inventor defoamed, molded, solidified, extracted with water, and dried a kneaded product composed of a thermoplastic elastomer, water-soluble inorganic salt particles, and a water-soluble solvent. In the method for producing a porous body, a polyalcohol soluble in water is used as the solvent, and the content of the polyhydric alcohol in the kneaded product is set within a predetermined range, whereby a liquid filter or a liquid absorbing sponge is used. It has been found that a three-dimensional network-like and homogeneous porous body that can be suitably applied to the above can be manufactured safely and easily and stably, and problems such as working environment and cost increase can be reduced.

  The present inventor has also found that the three-dimensional network porous body obtained in this way has pores with high uniformity in pore diameter, has good liquid permeability, and instantaneously drops alcohol and other liquid droplets. The inventors have found that the present invention has excellent liquid absorbability that can be absorbed, and that it has excellent properties for discharging the liquid that has been absorbed, and has completed the present invention having the following constitution.

The invention described in claim 1
A step of kneading a thermoplastic elastomer, water-soluble inorganic salt particles, and a composition containing water-soluble polyhydric alcohol as a main raw material to obtain a kneaded product,
Defoaming and molding the kneaded product to obtain a molded product,
A step of solidifying the obtained molded product,
A step of water-extracting the inorganic salt particles and the polyhydric alcohol from the solidified molding, and a step of drying the molding after water extraction,
In the inorganic salt particles, the content of particles having a particle size exceeding 150 μm is 35% by mass or less,
Porous, characterized in that the blending amount of the polyhydric alcohol in the composition is 55% by mass or more based on the maximum blending amount of the polyhydric alcohol uniformly mixed with the thermoplastic elastomer at the time of hot melting of the thermoplastic elastomer. It is a manufacturing method of a mass.

  The thermoplastic elastomer used in the production method of the present invention (invention of claim 1) shows the properties of vulcanized rubber (properties as an elastomer) at room temperature, but it can be plastically deformed at high temperatures and is a plastic processing machine. It refers to a polymer material that can be molded and can measure the melting temperature (by the method described later).

  Water-soluble inorganic salt particles are used as a pore-generating agent in this production method. The inorganic salt particles are characterized in that the content of the inorganic salt particles having a particle size exceeding 150 μm is not more than 35% by mass, preferably not more than 5% by mass. When the content of particles having a particle size exceeding 150 μm exceeds 35% by mass, a porous body having a three-dimensional network structure (three-dimensional network porous body) cannot be obtained.

  If inorganic salt particles having a submicron particle size with a maximum mass frequency are used, they are fine, and therefore, secondary agglomeration is likely to occur after processing, which makes manufacturing operations difficult. In practice, inorganic salt particles containing a large amount of such fine particles are difficult to manufacture from both the viewpoint of equipment and processing cost. Accordingly, the inorganic salt particles are preferably those having a particle size of 1 μm or less and a content of 5% by mass or less.

  By changing the particle size of the inorganic salt particles, the pore diameter of the three-dimensional network porous body can be adjusted. On the other hand, the optimum pore diameter varies depending on the use of the three-dimensional network porous material. For example, the optimum pore diameter is different for a liquid filter, a draining sponge, and a squeezed sponge. Therefore, inorganic salt particles having an optimum particle size distribution (that is, producing an optimum pore size) are selected according to the intended use of the produced porous body.

  The polyhydric alcohol used in the production method of the present invention refers to alcohols in which a plurality of hydrogen atoms of a hydrocarbon are substituted with hydroxyl groups.

  When the present inventors gradually add a liquid polyhydric alcohol at a temperature to a thermoplastic elastomer that is in a molten state by heating, it melts uniformly up to a certain addition amount, but the addition amount exceeds a certain value. It has been found that a phase separation state occurs, that is, excess polyhydric alcohol starts to separate. In the molten state of the thermoplastic elastomer, the addition amount of the polyhydric alcohol when starting separation, that is, the maximum blending amount of the polyhydric alcohol when separation does not occur is hereinafter referred to as “limit addition amount”.

  The inventors of the present invention made the structure of the produced porous body from a three-dimensional film shape to a three-dimensional network by setting the blending amount of the polyhydric alcohol in the composition to 55 mass% or more of the limit addition amount. I found out that That is, the change from the three-dimensional film shape to the three-dimensional network shape can be controlled by the blending amount of the polyhydric alcohol. When the blending amount of the polyhydric alcohol is less than 55% by mass of the limit addition amount, the three-dimensional film In the case of 55% by mass or more, a three-dimensional network-like porous body is obtained. In the production method of the present invention, the blending amount of the polyhydric alcohol in the composition is a limit that is the maximum blending amount of the polyhydric alcohol that is uniformly mixed with the thermoplastic elastomer in the molten state of the thermoplastic elastomer (when melted). It is characterized by being 55 mass% or more based on the amount added.

  According to a second aspect of the present invention, the blending amount of the polyhydric alcohol in the composition is 60% by mass with respect to the maximum blending amount of the polyhydric alcohol that is uniformly mixed with the thermoplastic elastomer at the time of thermal melting of the thermoplastic elastomer. It is the above, It is the manufacturing method of the porous body of Claim 1 characterized by the above-mentioned.

  By setting the blending amount of the polyhydric alcohol in the composition to 60% by mass or more of the limit addition amount, a porous body having a three-dimensional network shape can be obtained more clearly. Further, when the thermoplastic elastomer is polyurethane, the later-described ethanol permeation time can be less than 55 seconds, and particularly when the polycarbonate-based polyurethane is used, the later-described ethanol permeation time can be less than 35 seconds.

  Invention of Claim 3 is manufactured by the manufacturing method of the porous body of Claim 1 or Claim 2, Ethanol permeation | transmission time is less than 100 second, The three-dimensional network porous body characterized by the above-mentioned It is.

  The thermoplastic polymer porous body produced by a conventional production method in which a polyhydric alcohol is not used or the amount of polyhydric alcohol used is less than 55% by mass of the limit addition amount has a three-dimensional membrane structure. The three-dimensional film structure refers to a structure in which the bubbles constituting the porous body are continuous with each other in the three-dimensional direction, but a part of the bubbles is a film. That is, the contact portion between the bubbles is formed by a hole connecting the film and the bubble (the area ratio of the film to the hole is referred to as “the area ratio of the film”). The three-dimensional network structure refers to a structure in which bubbles forming a porous body are continuous with each other in a three-dimensional direction, and a film is hardly observed at a contact portion between the bubbles of the porous body.

  Thus, the three-dimensional membrane structure and the three-dimensional network structure are distinguished by the presence / absence of a film at the contact portion between the bubbles of the porous body, specifically, the area ratio of the film occupying the contact portion. . The area ratio of the film occupying the contact portion can be measured by an electron micrograph of the cut surface of the porous body, but usually the measurement is complicated and accurate measurement is often difficult. The inventor of the present invention has a strong correlation between the ethanol permeation time (a time required for a predetermined amount of ethanol to permeate through a 2 mm-thick porous body) and the area ratio of the membrane occupying the contact portion. It has been found that the measured value of time can be used as an index of the area ratio of the film occupying the contact portion, and further as an index for distinguishing between the three-dimensional film structure and the three-dimensional network structure. That is, when the area ratio of the membrane occupying the contact portion is large (three-dimensional membrane structure), ethanol hardly permeates through the porous body and the ethanol permeation time is long, but when the area ratio of the membrane occupying the contact portion is small ( In the three-dimensional network structure, ethanol easily permeates through the porous body, and the ethanol permeation time is shortened.

  Specifically, those having an ethanol permeation time of 100 seconds or more can be classified into a three-dimensional membrane structure because the area ratio of the membrane occupying the contact portion is relatively large, while those having an ethanol permeation time of less than 100 seconds Can be classified as a three-dimensional network structure because the area ratio of the film is relatively small. However, the production method of the present invention, that is, when the blending amount of the polyhydric alcohol is 55% by mass or more of the limit addition amount, there is a significant difference in the ethanol permeation time of the porous body obtained compared to the case of less than 55% by mass. As described above, in the production method of the present invention, by further increasing the blending amount of the polyhydric alcohol, a porous body whose ethanol permeation time is much shorter than 100 seconds, that is, more clearly in a three-dimensional network structure. A certain porous body can be obtained easily.

  The invention according to claim 4 is the three-dimensional network porous body according to claim 3, wherein the ethanol permeation time is less than 55 seconds.

  In order to exhibit excellent liquid permeability and liquid absorbency and to further improve the properties of discharging the liquid that has been absorbed, a porous body having a clearer three-dimensional network structure is required. Specifically, a porous body having an ethanol permeation time of less than 55 seconds is preferable, and a porous body having a time of less than 35 seconds is more preferable. As described above, in the production method of the present invention, by increasing the blending ratio of the polyhydric alcohol with respect to the limit addition amount, an ethanol permeation time of less than 55 seconds can be easily obtained, and if the blending ratio is further increased. Also, a product of less than 35 seconds can be easily obtained.

  The invention according to claim 5 is the three-dimensional network porous body according to claim 3 or 4, wherein the thermoplastic elastomer is made of polyurethane.

  The invention according to claim 6 is the three-dimensional network porous body according to claim 3 or 4, wherein the thermoplastic elastomer is made of polyolefin.

  As the thermoplastic elastomer constituting the three-dimensional network porous body of the present invention (continuous pore elastic body: invention of claim 3 or claim 4), a polyurethane-based thermoplastic elastomer and a polyolefin-based thermoplastic elastomer are liquid filters. In addition, it can be mentioned as preferred for the use of a liquid-absorbing sponge such as a draining sponge or a squeezing sponge. However, the thermoplastic elastomer is not limited to these.

  By using a polyurethane-based thermoplastic elastomer, a porous body that is flexible and has rebound resilience, has excellent wear resistance, mechanical strength, low temperature elasticity, heat resistance, and can withstand a use temperature of 70 ° C. or more. Can do. By using a polyolefin-based thermoplastic elastomer, a porous body resistant to chemicals such as strong acid and strong alkali can be obtained.

  A seventh aspect of the present invention is a liquid filter using the three-dimensional network porous body according to any one of the third to sixth aspects.

  Conventionally, various liquid filters have been used for solid-liquid separation for removing unnecessary solids contained in a liquid or recovering useful solids. In particular, liquid filters targeting solids with a size of 0.1 μm to 10 μm are called precision filters, and those targeting larger solids are called particle filters. Used as an osmotic prefilter.

  The three-dimensional network porous body of the present invention (the invention according to any one of claims 3 to 6) has a fine pore size, high uniformity of pores, and has a three-dimensional network structure, so that the liquid can be used. Easy to penetrate. Therefore, when used as a liquid filter for filtering fine particles in a liquid, particularly as a precision filter, the fine particles can be removed with high efficiency, and the pressure loss due to filtration is small, so that it is preferably used. For example, it is possible to provide a liquid filter capable of separating fine particles having a particle diameter in the range of 1 to 10 μm from the liquid in a short time with a low pressure loss.

  The invention according to claim 8 is a liquid-absorbing sponge using the three-dimensional network porous body according to any one of claims 3 to 6. A sponge means a continuous pore elastic body, and examples of the liquid absorbing sponge include a liquid draining sponge and a squeezed sponge.

  In recent years, with the development of the electronic equipment industry, there are various uses as described below as members used in the manufacture of precision parts and electronic parts, and the use of continuous pore elastic bodies is expected for these uses. .

1) In the chemical treatment process for precision equipment and electronic parts, for example, the development process, etching process, and electroless plating process, the chemicals used for each process, that is, the developer, etching liquid, electroless plating liquid, etc. are taken to the next process. Liquid draining sponge used for liquid draining rollers to absorb liquid.
2) A squeezing sponge used for a squeezing roller for uniformly and cleanly wiping off water and other solvents adhering to the surface of the washed product (object to be cleaned) in the cleaning step after the chemical treatment step.
3) A so-called scrub cleaning sponge that cleans insoluble particle stains from silicon wafers, glass plates for photomasks and liquid crystal displays, aluminum or glass disks for magnetic disks, precision processed metal parts, and the like.

  Liquid draining sponges and squeezed sponges are required to have the property of quickly absorbing and absorbing liquid (absorbing property) and the property of discharging the absorbed liquid efficiently by discharging with external force (discharging property). Further, the liquid draining sponge is required to have chemical resistance.

  Further, the liquid draining sponge may be required to have a property that a low molecular weight compound such as a plasticizer does not elute due to a chemical solution or the like. Conventionally, liquid draining sponges and squeezed sponges made of polyvinyl chloride softened with a plasticizer are known and commercially available, but these sponges have a problem that the plasticizer is eluted.

  As the liquid draining sponge and the squeezing sponge, those made of a continuous pore elastic body of Japanese Patent No. 4702774 are known, and the performance of the liquid draining sponge and the squeezing sponge is excellent. However, in recent years, the line spacing of printed wiring and semiconductor wiring tends to be extremely narrow (specifically, the line spacing has been about 25 μm in 2005 for printed circuit boards, but has recently become about 10 μm, and about 2005 for semiconductors. In recent years, it is expected to be about 20 to 30 nm, and is expected to be about 10 nm in the future.) However, liquid draining sponges and squeezed sponges that are further superior in liquid absorption and discharge properties are desired. Yes.

  By using the three-dimensional network porous material of the present invention, it is possible to provide a draining sponge and a squeezed sponge having excellent liquid absorption and discharge properties that satisfy recent requirements.

  The invention according to claim 9 is the liquid-absorbing sponge according to claim 8, characterized by containing a surfactant of HLB 8 or higher.

  By adding a surfactant having an HLB value of 8 or more to the three-dimensional network porous material of the present invention, it provides excellent water absorption that instantaneously absorbs liquid such as water adhering to precision products. be able to. Therefore, the three-dimensional network porous material of the present invention containing a surfactant having an HLB value of 8 or more has excellent water absorption and adheres to the product surface after washing the product in water in the manufacture of precision products. It can be suitably used as a liquid-absorbing sponge that cleans and evenly drains water droplets, and the residual moisture content of precision products can be significantly reduced. Specifically, the measurement value of the method for measuring the residual water content described in the examples described later can be 0.1 g or less. When the HLB value of the surfactant is smaller than 8, it is difficult to obtain this effect.

Here, the HLB value is a well-known index indicating the balance between the hydrophilicity and hydrophobicity of the surfactant, and the method for obtaining it is described in Michinori Oki et al., Chemical Dictionary published by Tokyo Chemical Doujin, page 178, etc. Has been. For example, when the surfactant is a fatty acid ester, it is calculated according to the following formula.
HLB = 20 × (1-SV / NV)
Here, SV is the saponification value of ester, and NV is the neutralization value of fatty acid.

  This surfactant preferably has an HLB value of 8 or more and 19 or less. By setting the HLB value to 19 or less, it is possible to obtain a three-dimensional network porous body that is also excellent in discharging properties (property of discharging water efficiently by compressing with an external force).

  The content of the surfactant is preferably in the range of 0.5 to 40 parts with respect to 100 parts by weight of the thermoplastic elastomer. If it is less than 0.5 parts by weight, the property of instantly absorbing water into the continuous pore elastic body becomes insufficient. If the content exceeds 40 parts by weight, the surfactant may move from the continuous pore elastic body to the outside, and the mechanical strength of the continuous pore elastic body may be lowered.

  According to the method for producing a porous body of the present invention, a homogeneous porous body having a three-dimensional network shape can be produced safely and easily. This manufacturing method has few problems such as influence on the working environment and cost increase.

  The three-dimensional network porous body of the present invention manufactured by this manufacturing method has pores with a highly uniform fine pore diameter and good liquid permeability. Therefore, it can be suitably used for applications such as liquid filters and liquid absorbing sponges. The liquid filter of the present invention using this three-dimensional network porous body can filter fine particles in the liquid with high filtration efficiency and low pressure loss (or large flow rate).

  Furthermore, the three-dimensional network-like porous body of the present invention has a high liquid absorbency capable of instantaneously sucking droplets of alcohol or the like. In addition, when a surfactant having an HLB of 8 or more is contained, the water absorption property is excellent in absorbing water instantly and the discharging property of the absorbed water is excellent. Therefore, the liquid-absorbing sponge of the present invention using this three-dimensional mesh-like porous body is excellent in liquid-absorbing and discharging properties, and is suitably used as a liquid draining sponge, a squeezing sponge, etc. used in the manufacture of precision products. be able to.

It is a SEM photograph of the section of the porous body of a three-dimensional membrane structure. It is a SEM photograph of the section of a three-dimensional network porous body. 4 is a SEM photograph of a cross section of a porous body obtained in Comparative Example 1. 4 is a SEM photograph of a cross section of a porous body obtained in Comparative Example 2. 3 is a SEM photograph of a cross section of the porous body obtained in Example 1. 3 is a SEM photograph of a cross section of a porous body obtained in Example 2. 5 is a SEM photograph of a cross section of a porous body obtained in Comparative Example 3. 4 is a SEM photograph of a cross section of the porous body obtained in Example 3. 4 is a SEM photograph of a cross section of a porous body obtained in Example 4. 6 is a SEM photograph of a cross section of the porous body obtained in Example 5. 6 is a SEM photograph of a cross section of a porous body obtained in Comparative Example 4. 6 is a SEM photograph of a cross section of a porous body obtained in Comparative Example 5. 6 is a SEM photograph of a cross section of the porous body obtained in Example 6. 6 is a SEM photograph of a cross section of the porous body obtained in Example 7. 6 is a SEM photograph of a cross section of a porous body obtained in Comparative Example 6. 6 is a SEM photograph of a cross section of a porous body obtained in Example 8. 10 is a SEM photograph of a cross section of a porous body obtained in Comparative Example 7. 6 is a SEM photograph of a cross section of a porous body obtained in Example 9. 2 is a SEM photograph of a cross section of a porous body obtained in Example 10. 2 is a SEM photograph of a cross section of a porous body obtained in Example 11. 4 is a SEM photograph of a cross section of a porous body obtained in Example 12. 10 is a SEM photograph of a cross section of a porous body obtained in Comparative Example 8. It is sectional drawing which shows typically the measuring method of ethanol permeation | transmission time. It is a graph which shows the particle size distribution of the powder for JIS testing. 4 is a SEM photograph of a cross section of a porous body obtained in Example 13. 4 is a SEM photograph of a cross section of a porous body obtained in Example 14. 6 is a SEM photograph of a cross section of a porous body obtained in Example 15.

  Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments and examples, and various modifications may be made within the same and equivalent scope as the present invention. Is possible.

As the thermoplastic elastomer used in the production method of the present invention,
SBS block copolymer (styrene-butadiene-styrene block copolymer), SIS block copolymer (styrene-isoprene-styrene block copolymer), SEBS block copolymer (styrene-ethylene-butylene-styrene block copolymer), SEPS block copolymer (Styrene-ethylene-propylene-styrene block copolymer), polystyrene-based thermoplastic elastomers such as HSBR block copolymer (hydrogenated styrene / butadiene rubber),
Polyolefin thermoplastic elastomers such as simple blend type, implant type and dynamic vulcanization type
Syndiotactic 1,2-polybutadiene, trans 1,4-polyisoprene, natural rubber, and other polydiene thermoplastic elastomers,
Chlorinated thermoplastic elastomers such as polyvinyl chloride and chlorinated polyethylene, polyurethane thermoplastic elastomers,
Engineering plastic thermoplastic elastomers such as polyester, polyamide, and fluorine,
Examples thereof include an ethylene-vinyl acetate thermoplastic elastomer, a silicone thermoplastic elastomer, and a biodegradable thermoplastic elastomer.

  As described above, polyolefin-based thermoplastic elastomers and polyurethane-based thermoplastic elastomers are preferred. Polyurethane-based thermoplastic elastomers are characterized by being excellent in wear resistance despite being flexible. Polyolefin thermoplastic elastomers are characterized by excellent chemical resistance, solvent resistance (a property that they are difficult to swell in polar solvents and are difficult to elute low molecular weight compounds), and weather resistance.

  Here, the polyurethane is obtained by reacting a polyol component composed of a polymer polyol and a chain extender and a polyisocyanate compound.

  Examples of the polymer polyol include polyether polyols such as polypropylene glycol, polytetramethylene glycol, and polymer polyols, polyester polyols such as adipate polyol and polycaprolactone polyol, polycarbonate polyols, and polyolefin polyols. Can be used alone or in combination of two or more. The desirable molecular weight of the polymer polyol is 500 to 10,000.

  Examples of the chain extender include ethylene glycol, 1,4 butanediol, 1,6 hexanediol, 1,5 pentanediol, 3-methyl-1,5 pentanediol, 1,3 propanediol and the like.

  Examples of the polyisocyanate compound include methylene diphenyl diisocyanate, tolylene diisocyanate, xylylene diisocyanate, naphthylene 1,5-diisocyanate, tetramethylene xylylene diisocyanate and other aromatic isocyanates, isophorone diisocyanate, dicyclohexylmethane diisocyanate and other alicyclic isocyanates, and the like. Examples thereof include aliphatic isocyanates such as hexamethylene diisocyanate, dimer acid diisocyanate, and norbornene diisocyanate.

  As described above, there are three types of polyolefin-based thermoplastic elastomers: a simple blend type, an implant type, and a dynamic vulcanization type. In any case, polypropylene or polyethylene is mainly used for the hard segment, and the soft segment is used for the soft segment. EPDM, NBR, etc. are mainly used. However, it is divided into more types depending on the difference and combination of the molecular structures of the components.

  The inorganic salt particles used in the production method of the present invention are not limited as long as they are water-soluble and have the predetermined particle size distribution. Specifically, chlorides such as sodium, potassium, magnesium and calcium, sulfates and the like can be used. These may be used alone or in combination of two or more.

  In the composition, the inorganic salt particles are preferably contained in an amount of 100 to 2000 parts by weight, preferably 300 to 1200 parts by weight, with respect to 120 parts by weight of the thermoplastic elastomer. If it is 100 parts by weight or less, the inorganic salt particles are dispersed without being connected in the composition, and it may be difficult to obtain a three-dimensional network porous body. On the other hand, when the amount exceeds 2000 parts by weight, the mechanical strength of the obtained three-dimensional network porous body may be extremely lowered, and may not be able to be used.

  Specific examples of the water-soluble polyhydric alcohol used in the production method of the present invention include ethylene glycol, ethylene glycol dimethyl ethers, ethylene glycol monoallyl ether, ethylene glycol monobutyl ether, ethylene that can be arbitrarily dissolved in warm water. Glycol mono t-butyl ether, polyethylene glycol, trimethylol ethane, trimethylol propane, glycerin, diglycerin, polyglycerin, erythritol, glucose, maltose, D-sorbitol, mannitol, maltitol, inositol, pentaerythritol, pinacol Etc.

  As described above, the production method of the present invention is characterized in that the content of the polyhydric alcohol is 55% by mass or more of the limit addition amount. The limit addition amount can be measured as follows using, for example, a mixing roll.

1) Anhydrous sodium sulfate having a mass twice that of the thermoplastic elastomer is added to the thermoplastic elastomer. If anhydrous sodium sulfate is not added, the thermoplastic elastomer is easily peeled from the surface of the mixing roll when polyhydric alcohol is added. As anhydrous sodium sulfate, SS-3 (described in Table 7) used in Examples described later can be mentioned as having a preferable particle size distribution.
2) At a temperature equal to or higher than the melting temperature of the thermoplastic elastomer and the polyhydric alcohol (preferably 10 to 30 ° C. higher than the melting temperature), the polyhydric alcohol is added to the thermoplastic elastomer added with anhydrous sodium sulfate obtained in 1). Kneading while adding. The added polyhydric alcohol is kneaded with the thermoplastic elastomer to form a substantially uniform hot melt. Here, the melting temperature means that when pelletized or flaky resin is put into a melting point measuring instrument and heated, the pelletized or flaky particles begin to melt, and the boundary between the particles is visually observed. Says the temperature when it runs out.
3) Polyhydric alcohol is added little by little, and when the amount exceeds a certain amount, excess polyhydric alcohol begins to separate. The amount of polyhydric alcohol added at the start of the separation is measured by visual observation or the like to obtain the limit addition amount. The limit addition amount is divided by the mass of the thermoplastic elastomer at the start of kneading, and a value multiplied by 100 is referred to as the “mixing limit value”.

  In the production method of the present invention, first, a step of kneading a composition containing the thermoplastic elastomer, inorganic salt particles, and polyhydric alcohol as main raw materials is performed. Here, “contained as a main raw material” means that the thermoplastic elastomer, inorganic salt particles and polyhydric alcohol are essential components, but other components may be used as necessary and within the scope of the present invention. It may mean that an ingredient may be included.

  Other components that may be included in addition to this thermoplastic elastomer, inorganic salt particles and polyhydric alcohol include colorants, antioxidants, antifungal agents, antibacterial agents, surfactants and materials that exhibit various lubricant functions, Functional materials such as a flame retardant and a conductive material such as carbon black can be given.

  Kneading is performed by heating. The heating temperature at the time of kneading needs to be not less than the temperature at which the composition raw material such as the thermoplastic elastomer is melted and less than the temperature at which discoloration or decomposition occurs, and is preferably 80 ° C to 230 ° C.

  For kneading the composition, a mixing roll, a kneader, a screw extruder or the like can be used. During the heating and kneading, since the composition is plasticized and becomes close to clay, it is preferable to use an apparatus capable of easily stirring the composition.

  After kneading the composition, a step of defoaming and molding the kneaded composition is performed. The purpose of defoaming is to remove bubbles in the composition. The molding method is not particularly limited, and any method such as extrusion molding, compression molding, injection molding and the like is possible. More specifically, for example, a method of performing degassing under reduced pressure using a vent type extruder is exemplified, and a method of forming a desired shape by connecting a molding die to the extruder is preferably exemplified.

  After defoaming and molding, a step of solidifying the obtained molded product is performed. The molded composition is a clay-like plastic material when heated, and is extruded directly into water or extruded onto a support such as a conveyor, and cooled to a temperature lower than the melting temperature of the extruded composition. Solidify. Examples of the solidification method include a cooling method using air, water, or the like.

  After solidification, a step of removing the pore-forming agent (inorganic salt particles) and the polyhydric alcohol from the solidified molding by water extraction is performed. There is no restriction | limiting in particular in the method of extracting this water, For example, it can carry out by immersing in the warm water of about 60 degreeC one day or more. In addition, after leaving most of the inorganic salt particles to stand in warm water as described above, this is put into a general washing machine and washed with water at 20 ° C. to 80 ° C. for about 15 minutes to 90 minutes. The inorganic salt particles and the like can be removed by performing water exchange several times.

  The three-dimensional network porous body (continuous pore elastic body) of the present invention can be obtained by carrying out a step of drying by removing inorganic salt particles and the like after extraction. Drying is preferably performed at 110 ° C. or lower. This drying can be performed using a box-type dryer or a tumbler-type dryer.

  The liquid filter of the present invention can be produced by grinding or slicing the three-dimensional network porous body of the present invention as necessary, and then forming it into a cylindrical shape or a sheet shape. That is, the three-dimensional mesh-like porous body of the present invention is simply formed into a cylindrical shape or a sheet shape, exhibits a filter function, and achieves high filtration efficiency and low pressure loss (or high flow rate and filtration processing speed). be able to.

Conventionally, commercially available liquid filters include cellulose acetate, polyethylene terephthalate, tetrafluoroethylene resin, polyethersulfone, polypropylene and other non-woven fabrics, fiber laminates, thread windings, sintered bodies, etc., cylindrical, plate However, there were the following problems.
-In order to increase the cylindrical filtration area and increase the processing speed, there are many filters with complicated structures, such as processing the filter medium into pleats, winding and fixing, and the assembly cost is high.
-There are fibrils coming off the nonwoven fabric and fibers.

  Further, since a large amount of used filters are generated, disposal of such filters has become a major issue, and it has been desired to reduce the amount of waste. It has also been desired to reduce the maintenance cost by reducing the clogging of the filter and extending its life.

On the other hand, the liquid filter using the three-dimensional network porous body of the present invention has the following characteristics.
-Filtration efficiency and collection rate (ratio of the amount of solid separated by the filter to the amount of solid flowing into the filter) are high.
・ Processing speed is high. That is, when the pressure loss is the same as the conventional one, the volume (or mass) of the liquid flowing in the unit area of the filter per unit time is large. Or when the volume (or mass) is made the same as before, pressure loss is small.
-Long filtration life. That is, it takes a long time until the filter is clogged and a predetermined filtration rate cannot be obtained, or until a predetermined differential pressure (difference between the filtration primary side pressure and the filtration secondary side pressure) occurs.

Therefore, by the liquid filter using the three-dimensional network porous body of the present invention,
・ Because it is excellent in liquid permeability, it is possible to obtain a high processing speed without a complicated structure such as processing in a pleat shape, winding and fixing, and the assembly cost can be reduced.
・ The problem of fibril dropout and waste volume can be greatly reduced.
・ Maintenance cost can be reduced because filter clogging is small.
It is possible to achieve excellent effects such as.

  The liquid filter of the present invention having such characteristics is used in, for example, general chemical fields such as clarification of chemical products and process filters, purification of cutting oil, lubricating oil and hydraulic fluid (oil system, water system), etc. It is suitable as a liquid filter used in the mechanical field, health industry such as swimming pool and bath water clarification, and electronic parts industry such as plating liquid clarification and parts cleaning liquid purification.

  The liquid-absorbing sponge of the present invention, such as a draining sponge or a squeezing sponge, can be used after being processed into a roller. In this case, the three-dimensional network porous body of the present invention can be formed into a cylindrical shape, and a shaft can be attached to the center hole. At this time, you may adhere | attach using an adhesive agent between a shaft and sponge. Next, in order to increase the outer diameter of the roller, the smoothness of the surface of the outer diameter, and the roundness, a polishing process is usually performed.

  Examples of surfactants of HLB8 or higher that can be contained in the liquid-absorbing sponge of the present invention include sorbitan fatty acid ester, beef tallow glyceride ethoxylate, partial fatty acid ester of polyhydric alcohol such as polyglycerin fatty acid ester, polyethylene glycol lauryl ether, Ethylene oxide adducts of fatty alcohols such as polyethylene glycol stearyl ether, ethylene oxide adducts of fatty acids such as polyoxyalkylene ether taroates, polyoxyethylene glycol oleates, polyethylene glycol monostearate, or ethylenes of fatty amino or fatty acid amides Oxide adducts, ethylene oxide adducts of alkylphenols such as nonylphenol ethoxylate and octylphenol ethoxylate, Ethylene oxide adducts of Kill naphthol, ethylene oxide adducts of partial fatty acid esters of polyhydric alcohols.

  As a method for containing a surfactant having an HLB value of 8 or more, a composition containing a thermoplastic elastomer, inorganic salt particles and a polyhydric alcohol as main raw materials is further added to a surfactant having an HLB value of 8 or more. Thus, a method of performing the subsequent steps in the method of claim 1 or claim 2 is exemplified. In the case of this method, when the HLB value exceeds 19, the surfactant is extracted with water in the washing step when producing the three-dimensional network porous body, and the surfactant remaining in the three-dimensional network porous body is removed. The water absorption performance may be insufficient. Therefore, from this point as well, the HLB value of the surfactant is preferably 19 or less.

  As another method for containing a surfactant having an HLB value of 8 or more, a molded product obtained after water extraction or further drying of inorganic salt particles or the like in the method of claim 1 or claim 2 above. An example is a method in which a surfactant having an HLB value of 8 or more is added. Examples of the method of adding the surfactant include a method of immersing the obtained molded article in a liquid containing the surfactant and impregnating and drying.

  Next, the present invention will be described more specifically based on examples, but the scope of the present invention is not limited by these examples.

Measurement of the limit addition amount of polyhydric alcohol:
Using a mixing roll (MR-31 / 2 × 8 manufactured by Inoue Seisakusho Co., Ltd.), 50 g of the thermoplastic elastomer was heat-melted at a temperature 10 to 30 ° C. higher than the melting temperature of the thermoplastic elastomer to obtain anhydrous neutral sodium sulfate (Table SS-3) 100 g described in 7 is divided into three and mixed. At the same time, the polyhydric alcohol was added and kneaded little by little, and the amount of addition until the separation of the polyhydric alcohol was visually confirmed was taken as the limit addition amount. The mixing limit value was determined by the following formula from the limit addition amount thus measured and the mass of the thermoplastic elastomer, and is shown in Table 1.
Mixing limit value = (limit addition amount / mass of thermoplastic elastomer) × 100

In addition, the thermoplastic elastomer used for the measurement of a limit addition amount is as follows.
-Ethylene vinyl acetate copolymer: Ultrasen 626 (manufactured by Tosoh Corporation)
・ High density polyethylene: Nipolon Hard 1200 (manufactured by Tosoh Corporation)
Polyolefin (olefinic thermoplastic elastomer): Miralastomer 4010N (Mitsui Chemicals)
-Polyether polyurethane: Milactolan E380 (manufactured by Nippon Polyurethane Industry Co., Ltd.)
Polycarbonate polyurethane: Milactolan E980 (manufactured by Nippon Polyurethane Industry Co., Ltd.)

  First, the evaluation method of the porous body obtained by each Example and the comparative example is shown.

1. Ethanol permeation time:
As shown in FIG. 23 (a), a glass tube having a length of 300 mm and an inner diameter of 17.4 mm is placed vertically, and a stopper having a hole having a diameter of 6.8 mm is opened at the bottom thereof. Thereafter, as shown in FIG. 23 (b), the hole is closed with a test piece (porous body) sliced to a thickness of 2.0 mm using a fixture. Further, a polyethylene film is applied from the outside of the test piece and pressed with a finger to be sealed. A position at a height of 30 mm from the bottom in the glass tube is a lower scale, and a position at 130 mm is an upper scale. After injecting ethyl alcohol to a height of 200 mm, the polyethylene film is removed and the ethyl alcohol is poured off. The time from when the upper end of ethyl alcohol passed through the upper scale until it passed through the lower scale was measured with a stopwatch and used as the ethanol permeation time. The measurement temperature is 25 ° C.

2. SEM photograph: A scanning electron microscope JSM-5500LV manufactured by JEOL Ltd. was used.

3. Determination of sponge structure:
From the measurement results of “ethanol permeation time” and “SEM photograph”, it is determined whether it is a three-dimensional film structure or a three-dimensional network structure.

1) Judgment by SEM photograph Objective to determine whether a 3D film structure or a 3D network structure is obtained by taking a SEM photograph of the surface of a porous body (sponge), whose structure is to be judged, cut with a sharp blade cutter. Can be distinguished from each other. In this SEM photo, the cut surface of the resin and its vicinity are the brightest part, and the pores (bubbles) are darker inside, but the internal structure can be determined by adjusting the contrast of light and dark in the SEM picture. can do.

  FIG. 1 is an example of an SEM photograph of a porous body having a three-dimensional membrane structure, and FIG. 2 is an example of an SEM photograph of a porous body having a three-dimensional network structure. In FIG. 1, traces of water extraction of inorganic salt particles and the like are easy to understand, and bubbles corresponding to the particle size of the used inorganic salt can be seen. By adjusting the contrast of light and dark in the SEM photograph, it can be seen that the film is continuously connected to the bubble part and the through-holes are scattered as fine pores in the film, and it is determined that it has a three-dimensional film structure. Can do.

On the other hand, in FIG. 2, it is difficult to find traces of water extraction such as water-soluble inorganic salt particles having a thick skeleton and a pore-generating agent. When the contrast of light and dark in the SEM photograph is adjusted, it can be seen that there is no film between the skeletons, and it can be determined that the structure is a three-dimensional network structure. In the examples and comparative examples, the results of determination by SEM photographs in this way are shown in the column of “sponge structure” in the table. In the table, “film” indicates a three-dimensional film structure, and “net” indicates a three-dimensional network structure.
2) Determination by ethanol permeation time In Examples and Comparative Examples, the ethanol permeation time measured by the above method is shown in the column of “ethanol permeation time second” in the table. The ethanol permeation time can also be used to determine whether the structure is a three-dimensional membrane structure or a three-dimensional network structure. In the case of a three-dimensional network structure, the ethanol permeation time is 85 seconds or less.

4). Filtration test:
1) Filter holder:
A filter (Type KST-142 DIA 142MM, effective filtration diameter = 120 mm) manufactured by Toyo Roshi Kaisha, Ltd. was used, and a jig (filter holder) was prepared so that the effective filtration area of the filter was 33.2 cm ² .
2) Filtration test solution: 7 types or 11 types of JIS test powder (both Kanto Loam baked products) were dispersed in purified water to prepare a 5% by mass slurry, which was used as a filtration test solution. The particle size distribution of the slurry before filtration is shown in FIG. 24 (a) for 11 types and in FIG. 24 (b) for 7 types.
3) A filtration test was conducted under the conditions shown in Table 6 using the above apparatus and filtration test solution.

  The filtration pressure in Table 6 is a pressure when the filtration test solution is pressurized with compressed air, and is a value representing a difference (differential pressure, pressure loss) from atmospheric pressure. The filtration time is a value obtained by measuring the time from when 50 g of the filtration test solution starts to pass through the porous filter having a thickness of 2 mm to the end with a stopwatch. The maximum filtration particle size is the maximum particle size value in the particles contained in the filtrate after passing through the porous body filter.

5. Residual moisture:
1) Using a perforated copper plate (copper-clad glass epoxy plate) under the following measurement conditions, the weight of water remaining on the surface of the copper plate was measured with a precision balance. Incidentally, the relationship between the residual moisture content and the touch feeling when touched by hand is as follows.
0.40 g or more: Obviously wet.
0.10 g or more and less than 0.40 g: slightly wet.
0.10 g or less: Does not feel wet.

2) Measurement conditions A polyvinyl chloride shaft having an outer diameter of 22 mm and having a double-sided tape attached thereto was press-fitted into an inner hole of a cylindrical porous body having an outer diameter of approximately 42 mm and an inner diameter of 19 mm. Thereafter, in order to increase the smoothness and roundness of the roller surface, the cylindrical porous body was polished to an outer diameter of 40 mm and cut to a length of 300 mm to produce a roller. Similarly, a total of four rollers were produced. Prior to the test, these four rollers were sufficiently moistened with tap water and set in the following apparatus.

3) Roller configuration:
Two sets of the upper roller and the lower roller were arranged before and after (the total number of rollers was 4).
Vertical axis spacing: 37 mm, longitudinal axis spacing: 50 mm

4) Feeding and taking out the test substrate from the upper and lower rollers:
An electric conveyor having a length of 300 mm synchronized with the rotation speed of the roller was placed before and after the roller assembly so that the test substrate was smoothly fed and taken out.
5) Test substrate: Perforated plate with 840 through-holes having a diameter of 1.0 mm made of a copper-clad glass epoxy plate having a length of 200 mm, a width of 150 mm, and a thickness of 1.6 mm.

6) Method of adhering moisture to the test substrate surface before passing through the roller:
Immerse the test substrate in water (water temperature: 25 ± 2 ° C.), take it out, place it on the conveyor as it is (at this point, the amount of moisture adhering is about 2 g), and until it is sandwiched between the upper and lower rollers To 20 g of water was added dropwise.

  The following examples 1-7 and comparative examples 1-5 examine the influence on the pore structure by changing the addition amount of polyhydric alcohol using polycarbonate-based polyurethane, polyether-based polyurethane, and polyolefin as the thermoplastic elastomer. did.

Example 1
The following polyurethane, pore generator, and polyhydric alcohol were used as main raw materials.
・ Milactolane E980 120 parts by mass (polycarbonate polyurethane manufactured by Nippon Polyurethane Industry Co., Ltd.)
・ Anhydrous sodium sulfate (pore forming agent) 800 parts by mass (anhydrous sodium sulfate corresponding to SS-2 in Table 7)
・ Glycerin (manufactured by Sakamoto Pharmaceutical Co., Ltd.) 80 parts by mass

Auxiliary raw materials:
-Adeka Stub AO-80 1 part by mass (antioxidant: high molecular weight hindered phenol manufactured by Asahi Denka Kogyo Co., Ltd.)

  These raw materials were put into a pressure kneader and kneaded at a rotation speed of 30 rpm and 170 ° C. for 15 minutes. This was extruded at 170 ° C. from a vent type extruder having a screw diameter of 40 mm connected to a tube forming die having an outer diameter of 46 mm and an inner diameter of 20 mm, and cooled and solidified in a 20 ° C. water shower. Subsequently, it was left in 50 degreeC water for 1 week. Then, it washed with water with the washing machine, and dried with the box-type dryer, and obtained the porous body. The porous body thus obtained was cut to a length of 100 mm and sliced in the length direction to obtain a porous sheet having a width of 35 mm, a length of 100 mm and a thickness of 2 mm.

  The evaluation results of the porous body thus obtained are shown in Table 2. Moreover, this scanning electron micrograph is shown in FIG. As is apparent from this SEM photograph, the obtained porous body has a three-dimensional network structure.

Example 2
In Example 1, the same operation and evaluation were performed except that the amount of glycerin was 90 parts by mass, and the evaluation results are shown in Table 2. The SEM photograph is shown in FIG.

Comparative Example 1
In Example 1, the same operation and evaluation were performed except that the amount of glycerin was 63 parts by mass, and the evaluation results are shown in Table 2. The SEM photograph is shown in FIG.

Comparative Example 2
In Example 1, the same operation and evaluation were performed except that the amount of glycerin was 69 parts by mass, and the evaluation results are shown in Table 2. The SEM photograph is shown in FIG.

Example 3
The following polyurethane, pore generator, and polyhydric alcohol were used as main raw materials.
・ Milactolane E380 120 parts by mass (polyether polyurethane manufactured by Nippon Polyurethane Industry Co., Ltd.)
・ Anhydrous sodium sulfate (pore forming agent) 800 parts by mass (anhydrous sodium sulfate corresponding to SS-2 in Table 7)
・ Glycerin (Sakamoto Pharmaceutical Co., Ltd.) 69 parts by mass

Auxiliary raw material, ADK STAB AO-80 1 part by mass (Antioxidant High molecular weight hindered phenol manufactured by Asahi Denka Kogyo Co., Ltd.)

  These raw materials were put into a pressure kneader, and thereafter, the same operation and evaluation as in Example 1 were performed. The evaluation results are shown in Table 3. The SEM photograph is shown in FIG.

Example 4
The same operation and evaluation as in Example 3 were performed except that the amount of glycerin was 80 parts by mass. The evaluation results are shown in Table 3. Further, this SEM photograph is shown in FIG.

Example 5
The same operation and evaluation as in Example 3 were performed except that the amount of glycerin was 90 parts by mass. The evaluation results are shown in Table 3. Further, this SEM photograph is shown in FIG.

Comparative Example 3
The same operation and evaluation as in Example 3 were performed except that the amount of glycerin was 40 parts by mass. The evaluation results are shown in Table 3. The SEM photograph is shown in FIG.

Example 6
The following polyolefin and pore generator were used as main raw materials.
-120 parts by mass of Miralastomer 4010N (olefinic thermoplastic elastomer manufactured by Mitsui Chemicals)
-Anhydrous sodium sulfate (pore forming agent) 760 parts by mass (anhydrous sodium sulfate corresponding to SS-2 in Table 7)
・ Glycerin (Sakamoto Pharmaceutical Co., Ltd.) 44 parts by mass

Auxiliary raw material, ADK STAB AO-80 1 part by mass

  These raw materials were put into a pressure kneader, and each process after kneading was performed in the same manner as in Example 1 to obtain a porous body. The evaluation results are shown in Table 4. The SEM photograph is shown in FIG.

Example 7
The same operation and evaluation as in Example 6 were performed except that the amount of glycerin was 55 parts by mass. The evaluation results are shown in Table 4. The SEM photograph is shown in FIG.

Comparative Example 4
The following polyolefin and pore generator were used as main raw materials.
-120 parts by mass of Miralastomer 4010N (olefinic thermoplastic elastomer manufactured by Mitsui Chemicals)
-Anhydrous sodium sulfate (pore forming agent) 760 parts by mass (anhydrous sodium sulfate corresponding to SS-2 in Table 7)
・ Glycerin (Sakamoto Pharmaceutical Co., Ltd.) 34 parts by mass

Auxiliary raw material, ADK STAB AO-80 1 part by mass

  These raw materials were put into a pressure kneader, and each process after kneading was performed in the same manner as in Example 1 to obtain a porous body. The evaluation results are shown in Table 4. The SEM photograph is shown in FIG.

Comparative Example 5
In Comparative Example 4, the same operation and evaluation were performed except that the amount of glycerin was 39 parts by mass. The evaluation results are shown in Table 4. The SEM photograph is shown in FIG.

From the results shown in Tables 2 to 4, the following is clear.
1) When the amount of polyhydric alcohol added is increased, the porous structure of the porous body changes from a three-dimensional film structure to a three-dimensional network structure. The boundary is in the vicinity of (actual addition amount of polyhydric alcohol / limit addition amount) (alcohol ratio in the table) of 55% by mass.
2) The ethanol permeation time is clearly shorter in the case of a three-dimensional network porous body than in the case of a porous body having a three-dimensional membrane structure. It shows that the net-like porous body is far superior.
The above results are the same when the types of thermoplastic resins are different.

  In Examples 8 and 9 and Comparative Examples 6 and 7 below, the kind of polyhydric alcohol was changed, and it was examined that the amount of addition affects the pore structure of the porous body.

Example 8
The same operation and evaluation as in Example 1 were performed except that glycerin was changed to erythritol. The evaluation results are shown in Table 5. The SEM photograph is shown in FIG.

Example 9
The same operation and evaluation as in Example 1 were performed except that glycerin was changed to mannitol. The evaluation results are shown in Table 5. The SEM photograph is shown in FIG.

Comparative Example 6
In Example 8, the same operation and evaluation as in Example 8 were performed except that the amount of erythritol was 40 parts by mass. The evaluation results are shown in Table 5. The SEM photograph is shown in FIG.

Comparative Example 7
The same operation and evaluation as in Example 9 were performed except that the amount of mannitol was 40 parts by mass. The evaluation results are shown in Table 5. The SEM photograph is shown in FIG.

  According to Table 5, “When the amount of polyhydric alcohol added increases, the pore structure of the porous body changes from a three-dimensional membrane structure to a three-dimensional network structure. The boundary is (actual amount of polyhydric alcohol added / limit amount added). ) Is in the vicinity of 55% by mass. ”, It is shown that the result is the same even when the polyhydric alcohol is changed.

  In Examples 10 to 12 and Comparative Example 8 below, various inorganic salt particles having different particle size distributions are used in order to study the influence of the particle size of the inorganic salt particles that are pore-generating agents, and claim 1 (or claim 2). ) To prepare a porous body. Table 7 shows the particle size distribution of the various inorganic salt particles used. Moreover, in order to examine whether the produced porous body is useful as a liquid filter capable of separating particles of 1 to 10 μm, a filtration test was performed under the above-described conditions and methods.

Example 10
Preparation of anhydrous sodium sulfate ground product:
Since a commercial product of anhydrous sodium sulfate having a particle size of 5 μm is not usually available, SS-1 anhydrous sodium sulfate in Table 7 was pulverized using the following pulverizer. When measured using the following particle size distribution analyzer, the average particle size after pulverization was 4.5 to 4.9 microns.
・ Crushing classifier: Hosokawa Micron ACM pulperizer type H Model: ACM-30H
-Particle size distribution analyzer: Microwell HRA model 9320-x100 manufactured by Honeywell

  A porous material was obtained in the same manner as in Example 1 except that the anhydrous sodium sulfate pulverized product produced as described above was used. The SEM photograph of the obtained porous body is shown in FIG. 19, and the results of the filtration test are shown in Table 6.

Example 11
A porous material was obtained in the same manner as in Example 1 except that anhydrous sodium sulfate having a particle size distribution represented by SS-1 in Table 7 was used. The SEM photograph of the obtained porous body is shown in FIG. 20, and the results of the filtration test are shown in Table 6. In addition, the particle size distribution of the inorganic salt granular material shown in Table 7 is a value measured according to JIS Z 8801-1 (metal screen sieve) and JIS Z 8815 (general rule of sieving method). Represents mass%.

Example 12
A porous material was obtained in the same manner as in Example 1 except that anhydrous sodium sulfate having a particle size distribution indicated by SS-3 in Table 7 was used. The SEM photograph of the obtained porous body is shown in FIG. 21, and the results of the filtration test are shown in Table 6.

Comparative Example 8
A porous material was obtained in the same manner as in Example 1 except that anhydrous sodium sulfate having a particle size distribution indicated by SS-4 in Table 7 was used. The SEM photograph of the obtained porous body is shown in FIG. 22, and the results of the filtration test are shown in Table 6.

The results shown in Table 6 indicate the following.
When anhydrous sodium sulfate (inorganic salt fine particles) is used, SS-4 containing 35% of particles having a particle diameter of 150 μm or more (described in Table 7: 43% of particles of 150 to 500 μm are contained) (comparison) In Example 8), the conditions such as the type of thermoplastic elastomer and polyhydric alcohol and the amount of polyhydric alcohol added are the same as in Examples 1 and 12 (the blending ratio of polyhydric alcohol with respect to the limit addition amount is 63%). Nevertheless, a three-dimensional network porous body has not been obtained (a three-dimensional membrane structure, see FIG. 22).

  In the filtration test using the porous material obtained in Comparative Example 8, both the filtration pressure and the filtration time were large, and the maximum filtration particle size was as large as 18.5 μm. Therefore, it is shown that it is not suitable as a filter for filtering out particles having a particle size of 1 to 10 μm.

  On the other hand, in Examples 10 to 12 using anhydrous sodium sulfate that does not contain particles having a particle size of 150 μm or more, a three-dimensional network porous body was obtained, and this porous body was excellent in a filtration test. It shows filtration performance, and can be used as a filter that can filter out particles close to 1 to 10 μm.

Examples 13-15
Three types of anhydrous sodium sulfate (inorganic salt fine particles) containing 10%, 20% and 30% of particles having a particle size of 150 to 500 μm, mixed at different ratios of SS-3 and SS-4 in Table 7. Adjusted. A porous material was obtained in the same manner as in Example 1 except that these anhydrous sodium sulfate was used. As a result of observing SEM photographs (FIGS. 25, 26, and 27, respectively) of the obtained porous body, all were three-dimensional network porous bodies, and the ethanol permeation time was less than 100 seconds. The results are shown in Table 8.

  From the results shown in Table 8, the content of particles having a particle size of 150 to 500 μm contained in the inorganic salt particles is 35% by mass or less, and the blending ratio of the polyhydric alcohol with respect to the limit addition amount is the present invention. It is shown that a three-dimensional network porous body having an ethanol permeation time of 100 seconds or less can be obtained within the range of. However, the porous bodies obtained in Examples 13 to 15 also included a membrane structure portion as shown in the SEM photographs, and the ethanol permeation time exceeded 55 seconds. From this result, it is considered that the content of particles having a particle diameter of 150 to 500 μm contained in the inorganic salt particles is preferably 5% by mass or less.

  Next, the effect of using the three-dimensional network porous material of the present invention as a liquid-absorbing sponge was examined in Example 16 and Comparative Example 9 below.

Example 16
10 parts by mass of surfactant: Nonion OT-221 (polyethylene glycol sorbitan monooleate HLB value 15.0 manufactured by NOF Corporation) was added to the same raw material used in Example 7, and charged into a pressure kneader. Then, when each step after the kneading was carried out in the same manner as in Example 1, a three-dimensional network porous body was obtained. To process this porous body into a cylindrical porous body, attach a shaft to the center hole of the obtained cylindrical porous body to form a roller, and then increase the smoothness and roundness of the roller surface The residual moisture content was measured according to the above conditions and method. The result was 0.09 g.

Comparative Example 9
When 10 parts by mass of the surfactant: Nonion OT-221 was added to the same raw material as that used in Comparative Example 4 and charged into a pressure kneader, each step after kneading was carried out in the same manner as in Example 1, and 3 A porous body having a three-dimensional membrane structure was obtained. To process this porous body into a cylindrical porous body, attach a shaft to the center hole of the obtained cylindrical porous body to form a roller, and then increase the smoothness and roundness of the roller surface The residual moisture content was measured according to the above conditions and method. The result was 0.23 g.

  From Example 16 and Comparative Example 9, a porous body having a three-dimensional network structure can obtain a water-absorbing sponge having a much lower residual water content than a porous body having a three-dimensional membrane structure. It is clear that the water absorption performance is excellent.

  The present invention has found the limit value of polyhydric alcohol addition amount as described above, and, as seen in Comparative Examples and Examples of Tables 2 to 5, the addition mass of polyhydric alcohol is a fixed limit value (limit addition) It has been clarified for the first time that the pore structure of the porous body changes from a three-dimensional membrane structure to a three-dimensional network structure, and a guideline for controlling the pore structure of the porous body can be obtained. Is applied.

Claims (9)

A step of kneading a thermoplastic elastomer, water-soluble inorganic salt particles, and a composition containing water-soluble polyhydric alcohol as a main raw material to obtain a kneaded product,
Defoaming and molding the kneaded product to obtain a molded product,
A step of solidifying the obtained molded product,
A step of water-extracting the inorganic salt particles and the polyhydric alcohol from the solidified molding, and a step of drying the molding after water extraction,
In the inorganic salt particles, the content of particles having a particle size exceeding 150 μm is 35% by mass or less,
Porous, characterized in that the blending amount of the polyhydric alcohol in the composition is 55% by mass or more based on the maximum blending amount of the polyhydric alcohol uniformly mixed with the thermoplastic elastomer at the time of hot melting of the thermoplastic elastomer. A method for producing a mass.   The blending amount of the polyhydric alcohol in the composition is 60% by mass or more based on the maximum blending amount of the polyhydric alcohol that is uniformly mixed with the thermoplastic elastomer when the thermoplastic elastomer is hot melted. Item 2. A method for producing a porous body according to Item 1.   A three-dimensional network porous body produced by the method for producing a porous body according to claim 1 or 2, wherein the ethanol permeation time is less than 100 seconds.   The three-dimensional network porous body according to claim 3, wherein the ethanol permeation time is less than 55 seconds.   The three-dimensional network porous body according to claim 3 or 4, wherein the thermoplastic elastomer is made of polyurethane.   The three-dimensional network porous body according to claim 3 or 4, wherein the thermoplastic elastomer is made of polyolefin.   A liquid filter using the three-dimensional network porous body according to any one of claims 3 to 6.   A liquid-absorbing sponge using the three-dimensional network porous material according to any one of claims 3 to 6.   The liquid-absorbing sponge according to claim 8, comprising a surfactant having an HLB of 8 or more.