WO2023053984A1

WO2023053984A1 - Microorganism-fixing carrier for water treatment, and method for producing same

Info

Publication number: WO2023053984A1
Application number: PCT/JP2022/034513
Authority: WO
Inventors: 一宏大西; 雅弘内藤; 惣一郎廣川
Original assignee: 日清紡ケミカル株式会社
Priority date: 2021-09-28
Filing date: 2022-09-15
Publication date: 2023-04-06

Abstract

Provided are: a microorganism-fixing carrier for water treatment, the microorganism-fixing carrier having exceptional durability while maintaining organic wastewater treatment performance; and a method for producing the microorganism-fixing carrier for water treatment. In the microorganism-fixing carrier for water treatment according to the present invention, at least part of the peripheral side surface of a columnar body 1 made of soft polyurethane foam is coated with a coating member 2 that is harder than the soft polyurethane foam.

Description

Microorganism immobilization carrier for water treatment and method for producing the same

The present invention relates to a microorganism-immobilizing carrier for water treatment (hereinafter also simply referred to as "carrier") and a method for producing the same.

In the water treatment of organic wastewater such as sewage, night soil, and industrial wastewater, there is a method of purifying water by decomposing organic matter using microorganisms. As one of water treatment methods using microorganisms, there is known a method using a fixed bed or a fluidized bed of a carrier such as resin or ceramics on which microorganisms effective for water treatment are adhered (immobilized). In the case of a fluidized bed, for example, the carrier is used in a state in which it can be moved by stirring with a stirring blade, aeration with a pump, or the like in a water treatment tank.

For efficient water treatment, for example, Patent Document 1 describes a hollow tubular plastic carrier with a large specific surface area as a carrier. The introduction of water-soluble polymers containing microorganisms into the pores of the material is disclosed.

In addition, as a carrier that can withstand long-term use, in Patent Document 2, a porous resin obtained by extruding and foaming a thermoplastic resin is preheated, and a coating material extruded from an extruder is adhered to the outer surface of the resin. A carrier that suppresses the deformation of the porous resin and the accompanying increase in water flow resistance is described.

JP-A-11-276164 JP-A-2001-231554

However, the carrier described in Patent Document 1 has a risk that the water-soluble polymer may peel off during water treatment due to physical stirring or the like, and it is difficult to maintain the organic wastewater treatment performance for a long time, and it does not have sufficient durability. I couldn't say I did. In addition, the water-soluble polymer containing microorganisms has a small contact area between the water-soluble polymer portion and the organic wastewater, and the organic wastewater treatment capacity is not sufficient.

In addition, the carrier described in Patent Document 2 is obtained by bonding a porous resin and a coating material made of a thermoplastic resin, and the pore (cell) structure of the preheated porous resin allows microorganisms to reach the inside of the carrier. A uniform state that facilitates penetration was not maintained, and it could not be said that the organic wastewater treatment performance was good.

The present invention has been made to solve such problems, and it is an object of the present invention to provide a microorganism-immobilizing carrier for water treatment that is excellent in durability while maintaining organic wastewater treatment performance, and a method for producing the same. aim.

The present invention is based on the discovery that by coating a flexible polyurethane foam with a predetermined coating member, it is possible to obtain a microorganism-immobilizing carrier for water treatment that has excellent durability while maintaining organic wastewater treatment performance. is.

That is, the present invention provides the following means.
[1] A microorganism-immobilizing carrier for water treatment, wherein at least part of the side peripheral surface of a columnar body of flexible polyurethane foam is coated with a coating member harder than the flexible polyurethane foam.
[2] The above [1], wherein the covering member is integrally formed and has one or more slits in a portion of the covering member that covers the side peripheral surface of the columnar body. Microorganism immobilization carrier for water treatment of.
[3] The above [2], wherein one of the slits is a communicating slit extending from one bottom-side end of the columnar body to the other bottom-side end of the covering member. ] The microorganism immobilizing carrier for water treatment according to .
[4] The microorganism-immobilizing carrier for water treatment according to any one of [1] to [3] above, wherein the columnar body is a columnar body.

[5] A method for producing a microorganism-immobilizing carrier for water treatment, in which the side peripheral surface of a columnar body of flexible polyurethane foam is coated with an integrally formed coating member having slits, wherein the coating member comprises: A hollow elongated member having a slit extending in the length direction is used, and a flexible polyurethane foam composition is poured into the hollow portion of the elongated member through the slit or the end portion in the length direction of the elongated member. Manufacture of a microorganism-immobilizing carrier for water treatment, comprising the steps of injecting and foaming to obtain a rod-shaped object having the flexible polyurethane foam in the hollow part of the elongated material, and cutting the rod-shaped object into a predetermined length. Method.

INDUSTRIAL APPLICABILITY According to the present invention, a microorganism-immobilizing carrier for water treatment is provided which is excellent in durability while maintaining organic wastewater treatment performance.
Further, according to the present invention, there is also provided a method for easily producing the microorganism-immobilized carrier for water treatment.

1 is a perspective view showing one embodiment of a microorganism-immobilizing carrier for water treatment of the present invention. FIG. Fig. 2 is a perspective view showing another embodiment of the microorganism-immobilizing carrier for water treatment of the present invention;

Hereinafter, embodiments of the microorganism-immobilizing carrier for water treatment of the present invention and the method for producing the same will be described in detail.

[Microorganism immobilization carrier for water treatment]
In the microorganism-immobilizing carrier for water treatment of the present invention, at least a part of the side peripheral surface of the columnar body of flexible polyurethane foam is coated with a coating member harder than the flexible polyurethane foam.
The carrier as described above maintains the organic wastewater treatment performance of the flexible polyurethane foam, and has good durability against physical agitation by stirring blades and the like, impact by water flow, and self-weight pressure in a fixed bed. .
Embodiments of the carrier of the present invention include, for example, those shown in FIGS. The carrier shown in FIGS. 1 and 2 includes a covering member 2 having slits S on the side peripheral surface of a columnar body 1 of flexible polyurethane foam. The covering member 2 may cover the entire side peripheral surface of the columnar body 1, but preferably has a slit S as shown in FIGS. In FIG. 1, the columnar body 1 is a cylindrical body, and in FIG. 2, the columnar body 1 is a quadrangular prism.

<Covering member>
The covering member 2 covering the flexible polyurethane foam pillars 1 is made of a material harder than the flexible polyurethane foam.
Since the coating member 2 is harder than the flexible polyurethane foam forming the columnar body 1, deformation and breakage of the columnar body 1 are suppressed during use of the carrier. Therefore, in the above-described carrier in which the columnar bodies 1 are covered with the hard coating member 2, the contact surface with the organic wastewater is secured by the flexible polyurethane foam constituting the columnar bodies 1, and the organic wastewater treatment performance is maintained. , the covering member 2 provides excellent durability.

The covering member 2 itself is integrally formed from the viewpoint of manufacturing efficiency and cost during mass production of the carrier, and the portion of the covering member 2 that covers the side peripheral surface of the columnar body 1 It is preferable to have one or more slits S in the .
Since the covering member 2 is a single member, it is possible to reduce the labor and burden of forming the covering member compared to the case where a plurality of members are combined. is likely to be retained, and separation and detachment can also be suppressed.

The shape of the slit S is not particularly limited. 1 and 2, one of S is a communication slit extending from one bottom end of the columnar body 1 of the covering member 2 to the other bottom end thereof. is preferred.
If one of the slits S is a communicating slit, the contact surface between the flexible urethane foam columnar body 1 and the organic waste water can be easily secured when the carrier is used while maintaining the integrity of the coating member 2. It is also preferable from the viewpoint of manufacturing efficiency during mass production.

The covering member 2 only needs to cover at least a part of the side peripheral surface of the columnar body 1, and from the viewpoint of not increasing the water flow resistance inside the carrier, the bottom surfaces of the columnar body 1 are not covered. is preferred. That is, it is preferable that the flexible polyurethane foam is exposed on both bottom surfaces of the columnar body 1 .

The material of the covering member 2 is not particularly limited as long as it is harder than the flexible polyurethane foam forming the columnar body 1 . From the viewpoints of preventing damage to the water treatment tank, facilitating integration with the flexible polyurethane foam, versatility, etc., it is preferable that the resin contains a thermoplastic resin. Examples of thermoplastic resins include polyvinyl chloride, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-(meth)acrylate copolymer, Polystyrene, acrylonitrile-butadiene-styrene copolymer (ABS resin), nylon, polycarbonate, polyethylene terephthalate, poly(meth)acrylate, polyvinyl alcohol and the like.

For example, when the specific gravity of the columnar body 1 of flexible polyurethane foam is small, the coating member 2 increases the specific gravity of the carrier so that the carrier quickly settles in water when it is put into the water treatment tank, thereby preventing the adhesion of microorganisms. While facilitating, it may also have a specific gravity adjusting role such as ensuring good carrier fluidity in organic waste water. Therefore, it is also preferable to select the material of the covering member 2 from the viewpoint of adjusting the specific gravity.

<Flexible polyurethane foam>
In the present invention, a flexible polyurethane foam is used as a porous material for immobilizing microorganisms. Flexible polyurethane foams are thermosetting, have excellent heat resistance compared to thermoplastic resins, and have good flexibility with excellent adhesiveness to microorganisms, and are suitably used as carriers. be able to.
In the carrier of the present invention, the flexible polyurethane foam is columnar body 1 . If it is a columnar body, it is advantageous in terms of production efficiency, cost, and the like during mass production of the carrier.
Examples of the columnar body 1 include a columnar body as shown in FIG. 1, a prismatic body as shown in FIG. 2, and a columnar body having a star-shaped polygonal bottom surface. Among these, cylindrical bodies are preferable from the viewpoint of homogeneity and strength of the carrier. When the columnar body 1 is a cylindrical body, it is preferable that the covering member 2 covering the side peripheral surface of the cylindrical body has, for example, a C-shaped cross section in the bottom direction, as shown in FIG.

Flexible polyurethane foam is mainly composed of polyurethane resin (the content ratio is the largest), and optional components such as inorganic fillers, colorants, etc., and curing agents and Other ingredients may be included, such as ingredients derived from blowing agents, foam stabilizers, surfactants, catalysts, and the like. The content of these other components in the flexible polyurethane foam is within a range that does not interfere with the effects of the present invention.

For the flexible polyurethane foam, a known flexible polyurethane foam for microorganism immobilization carriers for water treatment can be used. Among them, those produced using the flexible polyurethane foam composition described later are preferable.

The flexible polyurethane foam preferably has a swelling density of 20 to 70 kg/m ³ , more preferably 25 to 65 kg/m ³ , still more preferably 30 to 60 kg/m ³ when swollen with water, from the viewpoint of efficient water treatment. is.
The term "swelling density" as used herein refers to a value obtained by dividing the absolute-dry mass of flexible polyurethane foam by the volume when swollen with water. The "absolutely dry state" is also referred to as an absolutely dry state, and refers to a state in which the flexible polyurethane foam is dried at 110°C, which is the heat-resistant temperature of the polyurethane resin or less, and no weight reduction is observed. "When swollen with water" refers to a state in which the flexible polyurethane foam is immersed in pure water at 25°C for 1 hour.

The flexible polyurethane foam preferably has an absolute dry density of 30 to 100 kg/m ³ , more preferably 35 to 95 kg/m ³ , still more preferably 40 to 90 kg/m ³ from the viewpoint of a moderate volume swelling rate. be.

From the viewpoint of good hydrophilicity, the flexible polyurethane foam preferably has a volume swelling ratio of more than 100% to 1000% or less, more preferably 105 to 600%, and still more preferably 110 to 300% when swelled with water.
As used herein, the term "volume swelling rate" refers to a value expressed by the ratio of the volume of a flexible polyurethane foam when swollen with water to the volume of the flexible polyurethane foam in an absolutely dry state.
The absolute dry volume includes the volume of the pores (cells) of the flexible polyurethane foam, and is the volume determined based on the external dimensions. For example, if the outer shape is a rectangular parallelepiped or a cube, the value is calculated as the product of the length, width and height of the three sides. The volume when swollen with water is also the volume determined based on the external dimensions, and includes the volume of water inside and the cells of the flexible polyurethane foam.

The cell structure of the flexible polyurethane foam should be a continuous pore structure from the viewpoint of allowing microorganisms, oxygen, and substrates that serve as nutrients for microorganisms in water to penetrate sufficiently into the interior of the foam, thereby facilitating the immobilization of microorganisms on the carrier. is preferred. In addition, it is preferable that the polyurethane skeleton constituting the cell structure has a so-called wall structure in which adjacent cells are partially film-like and partitioned by wall surfaces having a large surface area.
As for the cell structure, the average number of pores when swollen with water is preferably 2 to 8/5 mm, more preferably 3 to 7/5 mm, and still more preferably 4 to 6/5 mm.
The term "average number of pores" as used herein refers to the average number of pores existing on a straight line of arbitrary three lengths of 5 mm in flexible polyurethane foam when swollen with water.

The average pore size of the flexible polyurethane foam when swollen with water is preferably 0.2 to 5 mm, more preferably 0.4 to 3 mm, still more preferably 0.5 to 2 mm.
The average pore diameter is the average diameter of 50 pores, assuming that the pores in the microscopic image are perfect circles whose diameter is the average value of the long and short diameters.

In addition, the flexible polyurethane foam preferably exhibits good hydrophilicity, and as an indicator of hydrophilicity, the settling time in water is preferably 1 hour or less, more preferably 30 minutes or less, and still more preferably 15 minutes. It is below.
As used herein, the term “submersion time” refers to the time until all cubic pieces of flexible polyurethane foam with a side length of 5 mm dropped on the surface of distilled water at 25° C. settle below the water surface (in water). say the time

The above various physical properties of the flexible polyurethane foam are specifically determined by the methods described in the examples below.

The size of the carrier is not particularly limited, and can be set as appropriate in consideration of the shape and scale of the water treatment tank, water swelling, microbial adhesion, handling, manufacturing efficiency, and the like. For example, when the carrier is for a fluidized bed and the columnar body 1 is a cylindrical body, the diameter of the bottom surface and the height of the columnar body 1 (the length in the direction perpendicular to the bottom surface) are each preferably 3. It is about to 200 mm, more preferably 5 to 100 mm, still more preferably 6 to 80 mm, still more preferably 7 to 50 mm.

The thickness of the coating member 2 that covers the columnar body 1 is not particularly limited, and the size and thickness of the carrier are within the range in which deformation and breakage of the columnar body 1 are suppressed and excellent durability of the carrier is obtained. It can be appropriately set according to the material of the covering member 2 and the like. For example, when the diameter and height of the bottom surface of the support of the columnar body 1 are each about 3 to 200 mm, the thickness of the covering member 2 is preferably 0.1 to 10 mm, more preferably 0.2 to 8 mm. , more preferably 0.3 to 5 mm.

[Method for producing microorganism-immobilized carrier for water treatment]
Although the method for producing the carrier described above is not particularly limited, it is preferably produced by the production method of the present invention, for example.
The production method of the present invention is a method for producing a carrier in which the side peripheral surface of a columnar body of flexible polyurethane foam is covered with an integrally formed covering member having slits. A hollow elongated member having an extended slit is used, and a flexible polyurethane foam composition is injected and foamed into the hollow portion of the elongated member through the slit or the longitudinal end of the elongated member, and the elongated member is and a step of cutting the resulting rod into a predetermined length.

The flexible polyurethane foam composition injected and foamed from the slit or the end of the long material has a uniform cell structure throughout the hollow part of the long material. Polyurethane foams can be formed. Injection and foaming through a slit is more preferable from the viewpoint of performing more uniform injection and foaming in the length direction of the elongated material.
As described above, the slit or the end of the elongated material is used to obtain a rod in which the flexible polyurethane foam columnar body and the covering member are integrated, and by cutting the rod, the same shape is obtained. The cell structure of the porous body (soft polyurethane foam) is uniform, and the carrier in which the covering member and the porous body are integrated can be mass-produced efficiently.

Specifically, the manufacturing method can be performed, for example, by the following steps.
First, a single linear slit is processed in the length direction of a cylindrical pipe made of thermoplastic resin, and a cylindrical body having a C-shaped cross section in the radial direction (bottom direction) of the pipe (hereinafter referred to as “C-shaped ) is obtained.
Next, a flexible polyurethane foam composition is injected and foamed into the hollow portion of the C-shaped tubular body through a slit or an end portion in the length direction of the tubular body, and the flexible polyurethane foam is injected into the hollow portion of the C-shaped tubular body. to obtain a bar having
Then, by cutting the bar into a predetermined length according to the size of the desired carrier, a carrier in which a cylindrical body of flexible polyurethane foam is covered with a C-shaped cylindrical body can be produced. .

<Flexible polyurethane foam composition>
As the flexible polyurethane foam composition of the present invention, known raw material compositions for producing flexible polyurethane foams for carriers can be used. For example, a flexible polyurethane foam composition containing a urethane prepolymer, a polyisocyanate compound, a curing agent and a foaming agent, and optionally other components such as a foam stabilizer and a catalyst is preferably used. A polyol compound can also be used instead of the urethane prepolymer.
A flexible polyurethane foam is obtained by foaming and curing the flexible polyurethane foam composition.
In addition, the polyisocyanate compound is referred to as "polyisocyanate compound (a)" in order to distinguish it from the polyisocyanate compound that is a raw material for synthesizing the urethane prepolymer, which will be described later. It may be described as "polyisocyanate compound (b)".

(urethane prepolymer)
The urethane prepolymer is a polymer obtained by reacting a polyol compound with an amount of polyisocyanate compound (b) in which the molar equivalent ratio of the isocyanate group to the hydroxyl group of the polyol compound is excessive. has two or more isocyanate groups. The urethane prepolymer may be used alone or in combination of two or more.
By using such a prepolymer as a raw material component, the production reaction of a flexible polyurethane foam is facilitated, and a flexible polyurethane foam having excellent homogeneity with little variation in cell structure can be easily obtained.

The urethane prepolymer is preferably a reaction product of a polyether polyol and a polyisocyanate compound (b), and is a polyether urethane prepolymer having two or more isocyanate groups in one molecule.
Both polyether polyols and polyester polyols can impart hydrophilicity to the resulting flexible polyurethane foams, but polyether polyols are superior in hydrolysis resistance to polyester polyols. Since flexible polyurethane foams are used in water, polyether polyols are preferable to polyester polyols as the polyol compound used as the raw material for synthesizing the urethane prepolymer from the viewpoint of the durability of the carrier.

Polyether polyols include, for example, polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycol. These are obtained by ring-opening polymerization of cyclic ether compounds such as ethylene oxide (hereinafter referred to as "EO"), propylene oxide (hereinafter referred to as "PO") and tetrahydrofuran. Polyether polyols may be used singly or in combination of two or more. A copolymer of a cyclic ether compound may also be used, and an EO-PO copolymer is preferable from the viewpoint of the flexibility and hydrophilicity of the resulting flexible polyurethane foam.
The monomer composition ratio of EO and PO in the EO-PO copolymer is preferably 90/10 to 10/90, more preferably 85/15 to 15/85, and still more preferably 80/20 in mass ratio. ~20/80.

From the viewpoint of ease of handling, the polyether polyol preferably has a viscosity that is not too high, and preferably has a number average molecular weight of 1,000 to 8,000, more preferably 2,000 to 7,000, and still more preferably 2,500 to 5,000. .

The polyisocyanate compound (b) to be reacted with the polyether polyol is a compound having two or more isocyanate groups in one molecule, and is not particularly limited.
Examples of the polyisocyanate compound (b) include toluene diisocyanate (hereinafter referred to as "TDI"), xylylene diisocyanate, diphenylmethane diisocyanate, naphthylene diisocyanate, biphenylene diisocyanate, diphenyl ether diisocyanate, tolidine diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate. , dicyclohexylmethane diisocyanate, and the like. The polyisocyanate compound (b) may be used singly or in combination of two or more.

When the polyisocyanate compound (b) is a compound having isomers, it may be one type of each isomer or a mixture of two or more isomers. For example, TDI has two isomers, toluene-2,4-diisocyanate (2,4-TDI) and toluene-2,6-diisocyanate (2,6-TDI). ,6-TDI alone or a mixture of the two may be used.

(Polyisocyanate compound (a))
The polyisocyanate compound (a) is not particularly limited, and specific examples thereof include the same as those exemplified for the polyisocyanate compound (b), which is the starting material for synthesizing the urethane prepolymer. The polyisocyanate compound (a) may be used alone or in combination of two or more.
Moreover, the polyisocyanate compound (a) may be the same as or different from the polyisocyanate compound (b) used as the starting material for synthesizing the urethane prepolymer.

The content of the polyisocyanate compound (a) is set in consideration of the viscosity of the flexible polyurethane foam composition, the hydrophilicity of the flexible polyurethane foam, etc., and is preferably 35 parts by mass with respect to 100 parts by mass of the urethane prepolymer. Below, it is more preferably 1 to 30 parts by mass, still more preferably 2 to 25 parts by mass.

(curing agent)
The curing agent is a compounding component for cross-linking and curing the urethane prepolymer and the polyisocyanate compound (a), and is also called a cross-linking agent.
Examples of curing agents include water; polyhydric alcohols such as glycerin, 1,4-butanediol and diethylene glycol; amine compounds such as ethanolamines and polyethylenepolyamines. Polyols obtained by ring-opening polymerization of polyhydric alcohol with ethylene oxide, propylene oxide, etc., and those obtained by adding a small amount of propylene oxide to the above-mentioned amine compounds may also be used. These may be used individually by 1 type, or may use 2 or more types together. Among these, water is preferably used from the viewpoint of reactivity, ease of handling, cost, and the like.
The content of the curing agent in the flexible polyurethane foam composition can be appropriately set in consideration of the flexibility, elasticity, strength, etc. of the flexible polyurethane foam obtained from the composition.

(foaming agent)
A blowing agent is a formulation ingredient for the foam formation of flexible polyurethane foams. The foaming agent generates carbon dioxide gas by reacting with an isocyanate group during a reaction to produce polyurethane, or evaporates itself during an exothermic reaction to foam polyurethane.
Examples of foaming agents include water, hydrofluorocarbons (HFC), hydrofluoroolefins (HFO), hydrochlorofluoroolefins (HCFO), carbon dioxide, and hydrocarbons such as cyclopentane. These may be used individually by 1 type, or may be used in combination of 2 or more types. Among the foaming agents, water is preferably used alone from the viewpoint of ease of handling, cost, environmental protection, and the like.
The content of the foaming agent in the flexible polyurethane foam composition is appropriately set in consideration of the foaming speed (foam generation speed) of the flexible polyurethane foam produced using the composition, the mixing state of the composition, and the like. can do.

As described above, water works both as a curing agent and as a foaming agent, and is suitable as a compounding component of a flexible polyurethane foam composition. The content of water when used as a curing agent and a foaming agent in the flexible polyurethane foam composition is preferably 20 to 90 parts by mass with respect to a total of 100 parts by mass of the urethane prepolymer and the polyisocyanate compound (a). More preferably 25 to 85 parts by mass, still more preferably 30 to 80 parts by mass.

(Other ingredients)
The flexible polyurethane foam composition may optionally contain other ingredients such as foam stabilizers, catalysts, inorganic fillers, colorants, and solvents. When other compounding components are included, the content of the other compounding components in 100 parts by mass of the flexible polyurethane foam composition is preferably 15 parts by mass or less, from the viewpoint of production efficiency of flexible polyurethane foams using the composition. It is more preferably 10 parts by mass or less, still more preferably 5 parts by mass or less.

A foam stabilizer is a compounding component for adjusting the foam state of a flexible polyurethane foam, and examples thereof include surfactants and silicone oils. These may be used individually by 1 type, or may use 2 or more types together.
When a foam stabilizer is included, the content of the foam stabilizer in 100 parts by mass of the flexible polyurethane foam composition is such that excess foam stabilizer remains in the flexible polyurethane foam, and from the viewpoint of suppressing foaming when the carrier is used. , preferably 5 parts by mass or less, more preferably 4 parts by mass or less, and even more preferably 3 parts by mass or less.

Examples of catalysts include known catalysts used in the production of flexible polyurethane foams, such as triethylamine, triethylenediamine, diethanolamine, N,N-dimethylaminoethoxyethanol, N-methylmorpholine, N-ethylmorpholine, tetramethylguanidine. tin catalysts such as stannous octoate and dibutyltin dilaurate; and other metal catalysts such as phenylmercuric propionate and lead octenate.

The inorganic filler is a compounding component for adjusting the specific gravity for the purpose of, for example, allowing the flexible polyurethane foam to quickly settle in water. Examples thereof include barium sulfate, calcium carbonate, talc, silica, alumina, activated carbon, zeolite, and graphite. etc. These may be used individually by 1 type, or may use 2 or more types together.

(Two-component composition)
The flexible polyurethane foam composition may be a one-component composition containing all of the ingredients, but is preferably a two-component composition of A and B components. Liquid A preferably contains a urethane prepolymer and a polyisocyanate compound (a), and liquid B preferably contains a curing agent and a foaming agent.
A two-component composition in which two component liquids, A component and B component, are separately prepared and then mixed and foamed, is suitable for stable and efficient production of flexible polyurethane foam.

Liquid A contains the above-described urethane prepolymer and polyisocyanate compound (a), and may contain the other ingredients in the flexible polyurethane foam composition.
The total content of the urethane prepolymer and the polyisocyanate compound (a) in liquid A is preferably 30 parts by mass or more, more preferably 35 to 100 parts by mass in 100 parts by mass of liquid A, from the viewpoint of production efficiency of flexible polyurethane foam. parts by mass, more preferably 40 to 100 parts by mass.

Liquid B contains a curing agent and a foaming agent, and may contain the above-mentioned other compounding ingredients in the flexible polyurethane foam composition.
From the viewpoint of efficiently producing a flexible polyurethane foam having a good cell structure, the total content of the curing agent and foaming agent in liquid B is preferably 45 parts by mass or more, more preferably 60 to 100 parts by mass, more preferably 65 to 100 parts by mass.

As a method for producing a flexible polyurethane foam using a two-component flexible polyurethane foam composition of liquids A and B, a known production method for a two-component flexible polyurethane foam can be applied. For example, a flexible polyurethane foam can be obtained by a method such as mixing liquid A and liquid B using a mixing head and performing injection foaming.
The mass mixing ratio of liquid A and liquid B is preferably 45/55 to 80/20, more preferably 50/50 to 77/23, from the viewpoint of efficiently obtaining a homogeneous flexible polyurethane foam with a desired cell structure. , more preferably 55/45 to 75/25.

The present invention will be described in detail below with reference to examples, but the present invention is not limited by these.

[Preparation of sample carrier]
<Sample carrier (1)>
A cylindrical transparent resin pipe made of polycarbonate having an outer diameter of 22 mm and a wall thickness of 2 mm was slit in the longitudinal direction with a width of about 10 mm to obtain a C-shaped tubular body.
A flexible polyurethane foam composition obtained by mixing the following liquid A and liquid B at a mass mixing ratio of 71/29 was injected into the hollow portion of the C-shaped cylindrical body through a slit and foamed. After removing the soft polyurethane foam protruding from the C-shaped cylindrical body, the carrier was cut into a length of 22 mm, and the cylindrical body of the flexible polyurethane foam was covered with the C-shaped cylindrical body (sample carrier (1)). manufactured.

(Flexible polyurethane foam composition)
≪Liquid A≫
TDI-modified EO-PO copolymer as urethane prepolymer (EO/PO mass ratio: 24/76, number average molecular weight of EO-PO copolymer: 2700 (theoretical value), NCO (isocyanate group) content: 4. 5% by mass)) and 88.3 g of TDI ("Coronate (registered trademark) T-80" manufactured by Tosoh Corporation; 2,4-TDI/2,6-TDI molar ratio 80/20) were stirred and mixed. was prepared.
≪Liquid B≫
Water 350 g, foam stabilizer (anionic surfactant, "Beaulite (registered trademark) LCA", manufactured by Sanyo Chemical Industries, Ltd.) 10 g, and amine catalyst ("Kaorizer (registered trademark) No. 26", Kao Corporation manufactured by N,N-dimethylaminoethoxyethanol) was stirred and mixed.

<Comparative sample carrier (1)>
A comparison sample carrier (1) was obtained by cutting the C-shaped tubular body of the sample carrier (1) as it was into a length of 22 mm.

<Sample carrier (2)>
In the manufacture of the above sample carrier (1), instead of the cylindrical transparent resin pipe made of polycarbonate, a cylindrical resin pipe made of ABS resin having the same shape is used, and the rest is the same as the sample carrier (1). , to prepare the sample carrier (2).

<Sample carrier (3)>
In the manufacture of the sample carrier (2), the cylindrical resin pipe made of ABS resin was not subjected to slit processing, but in the same manner as the sample carrier (2), the peripheral surface of the cylindrical body of flexible polyurethane foam was prepared. A carrier (sample carrier (3)) entirely covered with a cylindrical body (without slits) was produced.

<Comparative sample carrier (2)>
A comparison sample carrier (2) was obtained by cutting the C-shaped tubular body of the sample carrier (2) as it was into a length of 22 mm.

<Comparative sample carrier (3)>
A flexible polyurethane foam (without a covering member) hollowed out from the sample carrier (1) was used as a comparative sample carrier (3).

[Evaluation of flexible polyurethane foam]
Flexible polyurethane foams were hollowed out from sample carriers (1) to (3), and test pieces for evaluation were cut out from the center of each of the obtained flexible polyurethane foams, and the following various items were evaluated. Table 1 shows the evaluation results.

<Absolute dry density>
A test piece (approximately 5 mm×approximately 5 mm, thickness of approximately 5 mm when swollen with water) was weighed with an electronic balance, dried in a drier at 110° C., and the absolute dry mass M _d was measured.
In addition, the length of each side of the test piece in the absolute dry state is measured with a vernier caliper (resolution 0.05 mm; hereinafter the same), and the product of the length of each side is the volume of the test piece in the absolute dry state V _d and
The value of M _d /V _d was taken as the absolute dry density.

<Swelling density>
The test piece was immersed in pure water at 25 ° C. for 1 hour, and the length of each side of the test piece was measured with a vernier caliper in a state of being immersed in pure water in a flat state. The volume when swollen with water was taken as _Vw .
The value of M _d /V _w was taken as the swelling density.

<Volume swelling rate>
The volume swelling ratio is the ratio (V w /V _d ) of the volume V _w when swollen with water and the volume V _d in the absolute dry state (V _w /V d ).

<Average number of pores>
After measuring the volume _Vw when swollen with water, the central portion of the flat plate surface of the test piece was colored with red ink. A ruler was applied to the colored portion, and a photograph was taken so that the colored portion and the scale of the ruler were included. In the magnified image of the photograph, the number of pores observed on an arbitrary parallel line with the ruler was counted within the range of 5 mm intervals of the scale at an arbitrary location on the ruler. Similar measurements were performed at three arbitrary locations, and the average number of pores at each measurement location (three measurements) was taken as the average number of pores per 5 mm when swollen with water.
Observation with an electron microscope confirmed that the cell structure was a continuous pore structure and a wall structure.

<Average pore diameter>
After measuring the volume _Vw when swollen with water, an arbitrary point near the center of the surface of the test piece was observed with a microscope, and the major axis and minor axis of one pore in the observed image were measured. The pore shape was regarded as a perfect circle whose diameter was the average value of the major and minor axes, and the diameters of 50 pores were obtained in the same manner. The average value of these diameters was taken as the average pore diameter when swollen with water.

<Underwater sedimentation time>
One test piece (a cube with a length of 5 mm on each side) is placed in a 1 L polypropylene disposable cup and placed on the water surface of 600 mL of distilled water at 25 ° C. After dropping and putting it, the entire test piece is on the water surface. The time until it settled down (under water) was measured. Ten test pieces were measured. If the time until sedimentation (sedimentation time in water) was 1 hour or less, it was determined that the hydrophilicity was good.

[Strength evaluation of carrier]
Both bottom surfaces of sample carriers (1) to (3) were adhered to a tensile breaking strength tester (manufactured by Shimadzu Corporation), and tensile strength was measured ^. It was confirmed that the flexible polyurethane foam and the C-shaped cylindrical body covering it did not separate and maintained their integrated state.
The same tensile strength measurement was performed on the flexible polyurethane foams having the same shape and size as the sample carriers (1) to (3) and the comparative sample carrier (3) (both flexible polyurethane foams only). All of them had a tensile breaking strength of about 3 N/cm ² .
From these evaluation results, sample carriers (1) to (3) maintained the state of integration between the flexible polyurethane foam and the covering member even when used for water treatment, and had greater strength than the case without the covering member. It can be said that it is high and has excellent durability.

[Wastewater treatment test]
The following tests (1) and (2) were conducted as wastewater treatment tests using the carrier. In test (1), sample carrier (1) and comparative sample carrier (1) were used, and in test (2), sample carriers (2) and (3), and comparative sample carriers (2) and (3) were used. .

<Test (1)>
2 L of tap water, activated sludge from an aerobic tank as seed sludge, and 0.4 L of test carrier were added to a plastic tank for 2 L test water, and a nitrogen source (sodium nitrate; nitrate nitrogen (NO ₃ —N) 100 mg/ While adding L), the mixture was stirred with a propeller stirrer at 25° C. for 3 days to acclimatize the microorganisms to the sample carrier.
As simulated waste water, test raw water mainly containing sodium nitrate was passed through the tank, and treated water was appropriately sampled from the tank to measure the residual NO ₃ —N concentration (N ₁ ). The NO ₃ —N concentration (N ₀ ) of the test raw water passing through was also measured. The ratio of the NO ₃ -N concentration decrease (N ₀ -N ₁ ) to the NO ₃ -N concentration (N ₀ ) of the test raw water was calculated as the NO ₃ -N removal rate [%].
The NO ₃ —N concentration and raw water flow rate of the test raw water were adjusted, and the nitrogen volume load was changed to a high state, and the treatment effect was confirmed. Table 2 shows the test results for the sample carrier (1) and the comparative sample carrier (1).
Regarding the comparative sample carrier (1), No. The NO ₃ —N removal rate at No. 4 decreased. After 5 trials were discontinued.

<Test (2)>
5 L of tap water, activated sludge from an aerobic tank as seed sludge, and 1 L of sample carrier were added to a plastic tank for 5 L test water, and while adding a COD source (glucose; COD 400 mg/L), the mixture was heated at 25°C for 3 hours. Aeration and stirring with a pump were performed for days to acclimatize the microorganisms to the sample carrier.
As simulated waste water, test raw water mainly containing glucose was passed through the tank, treated water was appropriately sampled from the tank, and the residual COD value (C ₁ ) was measured. The COD value (C ₀ ) of the test raw water passing through was also measured. The ratio of the decrease in COD value (C ₀ −C ₁ ) to the COD value (C ₀ ) of test raw water was calculated as the COD removal rate [%].
The glucose concentration and raw water flow rate of test raw water were adjusted, and the treatment effect was confirmed assuming a state of high COD volume load. Table 3 shows the test results for sample carriers (2) and (3) and comparative sample carriers (2) and (3).
Regarding the comparative sample carrier (2), No. Since the COD removal rate in No. 5 decreased, After 6 trials were discontinued.

As shown in Tables 2 and 3, the sample carriers (1) to (3) coated with the coating member showed sufficiently high NO ₃ —N removal, comparable to the comparative sample carrier (3) without the coating member. and COD removal rate.
In addition, it was confirmed that all of the sample carriers (1) to (3) maintained the integrated state of the flexible polyurethane foam and the covering member even after the test, and were excellent in durability.

REFERENCE SIGNS LIST 1 columnar body (of flexible polyurethane foam) 2 covering member S slit

Claims

A microorganism-immobilizing carrier for water treatment, wherein at least part of the side peripheral surface of a columnar body of flexible polyurethane foam is coated with a coating member harder than the flexible polyurethane foam.
The water treatment according to claim 1, wherein the covering member is integrally formed, and has one or more slits in a portion of the covering member that covers the side peripheral surface of the columnar body. Microorganism immobilization carrier.
3. The slit according to claim 2, wherein one of said slits is a communicating slit extending from one bottom-side end of said columnar body to the other bottom-side end of said covering member. Microorganism immobilization carrier for water treatment.
The microorganism-immobilizing carrier for water treatment according to any one of claims 1 to 3, wherein the columnar body is a columnar body.
A method for producing a microorganism-immobilizing carrier for water treatment, in which the side peripheral surface of a columnar body of flexible polyurethane foam is coated with an integrally formed coating member having slits,
Using a hollow elongated material having a slit extending in the length direction as the covering member,
The flexible polyurethane foam composition is injected and foamed into the hollow part of the elongated material from the slit or the end in the length direction of the elongated material, and the hollow part of the elongated material contains the flexible polyurethane foam. the process of obtaining an object;
and cutting the rod-shaped object into a predetermined length.