JPWO2021045103A1 - Manufacturing method of flexible polyurethane foam - Google Patents

Abstract

A method for producing a flexible polyurethane foam used as a microbial immobilization carrier for water treatment, in which a mixed solution containing a urethane prepolymer and a polyisocyanate compound (a) is injected into a foam container and foamed to obtain a flexible polyurethane foam. The flexible polyurethane foam has a swelling density of 25 to 70 kg / m3 at the time of water swelling, and the temperature TW of the wall surface of the foam container in contact with the mixed solution is 21 to 60 ° C. A method for producing a flexible polyurethane foam, in which the average number of pores at the time of swelling is 9 to 30/25 mm, and the volume swelling rate expressed by the ratio of the volume at the time of water swelling to the volume in an absolutely dry state is 110 to 1000%. ..

Description

The present invention relates to a method for producing a flexible polyurethane foam.

Conventionally, as a carrier used in a sewage treatment apparatus that treats sewage using microorganisms, a carrier formed of a flexible polyurethane foam having excellent microbial immobilization performance, hydrophilicity / durability, and water sedimentation property has been studied.
According to Patent Document 1, in a water treatment carrier having water swelling property, which is made of a polyurethane foam having pores communicating from the surface of the carrier to the inside, the polyurethane foam is a cube, a rectangular parallelepiped, or a column, and is after water swelling. The length of all sides of a cube or a rectangular parallelepiped, or the diameter and height of a column after water swelling is 8 to 100 mm, the average number of pores after water swelling is 10 to 50/25 mm, and the volume swelling rate is 150. Water treatment carriers characterized by ~ 1000% are described.

Patent Document 2 describes a hydrophilic polyurethane prepolymer (c) and a polyisocyanate compound having at least two terminal isocyanate groups in one molecule obtained by reacting the _{polyisocyanate compound (a 1) with the polyol compound (b).} A polyurethane foam obtained by adding water to a mixture with (a ₂ ) and reacting the mixture, and at least a part of the _{polyisocyanate compound (a 1} ) and / or (a _{2) does not substantially contain a polypeptide component.} A water-swellable polyurethane foam imparted with drug resistance, which is a purified diphenylmethane diisocyanate, a method for producing the same, and a carrier for a bioreactor using the same are described.

China Utility Model No. 2044547446 Japanese Unexamined Patent Publication No. 2004-359950

A flexible polyurethane foam for a microbial immobilization carrier for water treatment is generally produced by mixing a polyisocyanate compound and a polyol compound, or a urethane prepolymer and a polyisocyanate compound together with a foaming agent, a foam stabilizer, or the like and foaming. Will be done. Above all, when the flexible polyurethane foam is manufactured by the batch method, the production efficiency can be improved by manufacturing the individual slabs with a large bottom area and a high height. The density, water swellability, and pore structure (hereinafter referred to as “poor structure”) are due to the fact that the previously charged mixed liquid hardens while the mixed liquid is being charged into the foam container, while there is an upper limit to increasing the discharge amount. The “cell structure”) varied widely in the flexible polyurethane foam slab, and it was difficult to ensure the homogeneity of the physical properties.
On the other hand, when the slab becomes smaller, the density, water swellability, and cell structure differ between the central portion and the peripheral portion (upper surface, lower surface, side surface) in the slab, so that the portion where the homogeneity of physical properties is ensured decreases, and the yield is reduced. Decreases.
In addition, since the upper part of the foam container is usually in an open state, the upper part of the slab is arched, and the flexible polyurethane foam is sliced horizontally on the bottom surface of the slab (hereinafter, also referred to as "horizontal direction") to form a urethane foam sheet. In the case of manufacturing, the arch-shaped portion has a problem that the area is small when sliced and the usable range is small, so that the production efficiency is lowered.

The present invention has been made to solve such a problem, and provides a method for efficiently producing a flexible polyurethane foam having excellent density, water swellability, and cell structure homogeneity by a batch method. The purpose is to do.

According to the present invention, a flexible polyurethane foam having excellent density, water swellability, and cell structure homogeneity is efficiently produced by a batch method in which a mixed solution containing a predetermined component is injected into a foam container having a predetermined wall surface temperature and foamed. It is based on the finding that it can be obtained.

That is, the present invention provides the following [1] to [7].
[1] A method for producing a flexible polyurethane foam used as a microbial immobilization carrier for water treatment.
It has a step of injecting a mixed solution containing a urethane prepolymer and a polyisocyanate compound (a) into a foam container and foaming the mixture to obtain a flexible polyurethane foam.
Temperature _{T W} of the wall in which the mixed solution of the foam container is in contact is a 21 to 60 ° C.,
The flexible polyurethane foam has a swelling density of 25 to 70 kg / m ³ at the time of water swelling, an average number of pores of 9 to 30 at the time of water swelling / 25 mm, and a volume at the time of water swelling with respect to a volume in an absolutely dry state. A method for producing a flexible polyurethane foam, wherein the volume swelling rate represented by the ratio of
[2] The method for producing a flexible polyurethane foam according to the above [1], wherein the upper surface of the foam container is covered with a lid in the step of obtaining the flexible polyurethane foam.
[3] The method for producing a flexible polyurethane foam according to the above [1] or [2], wherein the height of the flexible polyurethane foam is 300 mm to 1200 mm.
[4] The method for producing a flexible polyurethane foam according to any one of the above [1] to [3], wherein the volume of the flexible polyurethane foam is 0.03 to 0.8 m ^3.
[5] The method for producing a flexible polyurethane foam according to any one of [1] to [4] above, wherein the mixed solution is injected at an injection rate of 5 to 200 kg / min.
[6] The method for producing a flexible polyurethane foam according to any one of [1] to [5] above, wherein the mixed solution is injected along the wall surface of the foam container.
[7] the absolute value of the difference between the temperature T _S and the temperature T _W of the walls of the mixed solution, process for producing a flexible polyurethane foam according to any one of [1] to [6] is 0 to 40.

According to the production method of the present invention, a flexible polyurethane foam having excellent density, water swellability, and cell structure homogeneity can be efficiently obtained by the batch method.

The method for producing a flexible polyurethane foam of the present invention is a method for producing a flexible polyurethane foam for a microbial immobilization carrier for water treatment.
The production method includes a step of injecting a mixed solution containing a urethane prepolymer and a polyisocyanate compound (a) into an effervescent container and foaming the mixture to obtain a flexible polyurethane foam, and the mixed solution of the effervescent container comes into contact with the mixed solution. temperature _{T W} of the wall is a 21~60 ℃.
The flexible polyurethane foam has a swelling density of 25 to 70 kg / m ³ at the time of water swelling, an average number of pores at the time of water swelling of 9 to 30/25 mm, and a volume at the time of water swelling with respect to a volume in an absolutely dry state. The volume swelling rate represented by the ratio of is 110 to 1000%.
Here, the term "at the time of water swelling" as used in the present invention refers to a state in which the flexible polyurethane foam is immersed in water at 25 ° C. for 1 hour.
Further, the "swelling density" referred to in the present invention refers to a value obtained as a value obtained by dividing the mass in an absolutely dry state by the volume at the time of water swelling. Specifically, the swelling density can be measured by the method described in Examples described later.
The "absolutely dry state" refers to a state in which the flexible polyurethane foam is dried at 100 ° C. and no decrease in mass is observed. It may be called an absolutely dry state.
Further, the "volume swelling rate" referred to in the present invention refers to a value represented by the ratio of the volume at the time of water swelling to the volume in the absolutely dry state. Further, the "volume in the absolute dry state" shall include the pores of the flexible polyurethane foam, and shall be the volume obtained based on the outer dimensions of the flexible polyurethane foam in the absolute dry state. Further, the "volume at the time of water swelling" shall include the pores of the flexible polyurethane foam and the water absorbed therein, and shall be the volume obtained based on the external dimensions of the swelled flexible polyurethane foam. For example, when the flexible polyurethane foam has a rectangular parallelepiped shape, the value calculated as the product of the lengths of the three sides of the rectangular parallelepiped, that is, the length, the width, and the height, is taken as the volume of the flexible polyurethane foam.
As described above, by pouring the mixed solution into a foam container whose wall surface temperature is controlled and foaming, a flexible polyurethane foam having excellent density, water swellability, and cell structure homogeneity can be efficiently produced by the batch method. Can be manufactured as a target.

[Process to obtain flexible polyurethane foam]
The step of obtaining the flexible polyurethane foam is a step of injecting a mixed solution containing the urethane prepolymer and the polyisocyanate compound (a) into a foam container and foaming the mixture to obtain the flexible polyurethane foam, and the mixing of the foam container. temperature _{T W} (hereinafter, also referred to as temperature _{T W} of the walls.) of wall the solution is in contact is 21 to 60 ° C.. The temperature T _W of the walls, the mixed solution was injected until foaming is complete, in the range of 21-60 ° C..

<Mixed solution>
The mixed solution contains a urethane prepolymer and a polyisocyanate compound (a).

(Urethane prepolymer)
The urethane prepolymer is a polymer obtained by reacting a polyol compound with a polyisocyanate compound (b) in an amount such that the molar equivalent ratio of isocyanate groups is excessive, preferably 110% or more, with respect to the hydroxyl group of the polyol compound. It has two or more isocyanate groups in one molecule. The urethane prepolymer may be used alone or in combination of two or more.
By using such a prepolymer as a raw material compound, it is easy to obtain a flexible polyurethane foam having excellent water swelling property, a small variation in density and cell structure, and excellent homogeneity.

The urethane prepolymer is a polyether urethane prepolymer having two or more isocyanate groups in one molecule, which is obtained by reacting a polyether polyol with a polyisocyanate compound (b), and a polyester polyol and a polyisocyanate compound. Examples thereof include a polyester-based urethane prepolymer having two or more isocyanate groups in one molecule obtained by reacting with (b).
Both the polyether polyol and the polyester polyol can impart hydrophilicity, but the polyether polyol is more excellent in hydrolysis resistance than the polyester polyol. In the present invention, since the produced flexible polyurethane foam is used in water as a microbial immobilization carrier for water treatment, the polyether urethane prepolymer is polyester-based from the viewpoint of durability of the flexible polyurethane foam. Preferable over urethane prepolymer.
Further, the urethane prepolymer preferably has a viscosity that is not too high from the viewpoint of ease of handling, and the viscosity is preferably 300 to 9500 mPa · s as measured by a spindle viscometer at 25 ° C. , 300 to 9000 mPa · s, more preferably 300 to 8500 mPa · s.

Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol and the like. These are obtained by ring-opening polymerization of the cyclic ether compounds, ethylene oxide (EO), propylene oxide (PO), and tetrahydrofuran, respectively. The polyether polyol may be used alone or in combination of two or more. Further, it may be a copolymer of a cyclic ether compound and is used in water as a microbial immobilization carrier for water treatment. Therefore, from the viewpoint of hydrophilicity of the flexible polyurethane foam, EO-PO co-weight is particularly important. Coalescence is preferred.
The monomer composition ratio of EO and PO in the EO-PO copolymer is preferably 70/30 to 30/70 by mass ratio, more preferably 65/35 to 40/60, and further preferably 60/40. ~ 50/50.

The polyisocyanate compound (b) 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 (TDI), xylylene diisocyanate, diphenylmethane diisocyanate, naphthylene diisocyanate, biphenylenedi isocyanate, diphenyl ether diisocyanate, trizine diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate and the like. Be done. The polyisocyanate compound (b) may be used alone or in combination of two or more.

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

The polyisocyanate compound (b) is preferably toluene diisocyanate from the viewpoint of increasing the viscosity of the obtained prepolymer.

The content of the urethane prepolymer in the mixed solution is preferably 20 to 80% by mass, more preferably 25 to 70% by mass, and further preferably 30 to 60% by mass.

(Polyisocyanate compound (a))
The polyisocyanate compound (a) is not particularly limited, and specific examples thereof include those similar to those exemplified for the polyisocyanate compound (b) used in the synthesis of the urethane prepolymer. The polyisocyanate compound (a) may be used alone or in combination of two or more.
Further, the polyisocyanate compound (a) may be the same as or different from the polyisocyanate compound (b) used in the synthesis of the urethane prepolymer.
The polyisocyanate compound (a) is preferably toluene diisocyanate from the viewpoint of obtaining a flexible polyurethane foam for a microbial immobilization carrier for water treatment, which is excellent in durability (elasticity and abrasion resistance).

The content of the polyisocyanate compound (a) in the mixed solution is preferably 1 to 30% by mass, more preferably 1.5 to 20% by mass, and further preferably 2 to 10% by mass.

The mixed solution preferably contains a foaming agent.
Examples of the foaming agent include water, hydrofluorocarbon (HFC), hydrofluoroolefin (HFO), hydrochlorofluoroolefin (HCFO), carbon dioxide, and hydrocarbons such as cyclopentane. These foaming agents may be used alone or in combination of two or more. Among the foaming agents, water is preferable from the viewpoint of ease of handling, cost, environmental protection and the like.
The type and content of the foaming agent in the mixed solution can be appropriately set in consideration of the pore size of the flexible polyurethane foam that affects the microbial immobilization performance of the microbial immobilization carrier for water treatment.

The mixed solution preferably contains a curing agent. The curing agent is added for cross-linking and curing the urethane prepolymer and the polyisocyanate compound (a), and is sometimes called a cross-linking agent.
Examples of the curing agent include water; polyhydric alcohols such as glycerin, 1,4-butanediol and diethylene glycol; amine compounds such as ethanolamines and polyethylene polyamines. In addition, polyols obtained by ring-opening polymerization of ethylene oxide, propylene oxide and the like to the polyhydric alcohol, and those in which a small amount of propylene oxide is added to the amine compound can also be mentioned. These curing agents may be used alone or in combination of two or more. Among the curing agents, water is preferable from the viewpoint of reactivity, ease of handling, cost and the like.
The content of the curing agent in the mixed solution is appropriately set in consideration of the flexibility, elasticity, strength, etc. of the flexible polyurethane foam, which affects the microbial immobilization performance and strength of the microbial immobilization carrier for water treatment. be able to.

As described above, water is preferably used as a foaming agent and a curing agent in the production of flexible polyurethane foam used as a microbial immobilization carrier for water treatment. When water is used as the foaming agent and the curing agent, the content of water in the mixed solution is preferably 20 to 55% by mass, more preferably 25 to 50% by mass.

The mixed solution preferably contains an inorganic filler. By using an inorganic filler, the specific gravity of the produced flexible polyurethane foam can be adjusted, and when the microbial immobilization carrier for water treatment prepared using the flexible polyurethane foam is put into water, it quickly settles in water. Can be made to.
Examples of the inorganic filler include barium sulfate, calcium carbonate, talc, silica, alumina, activated carbon, and zeolite. The inorganic filler may be used alone or in combination of two or more. The inorganic filler preferably has a small bulk volume, and from this viewpoint, barium sulfate having a large specific gravity is preferable.
Further, the inorganic filler preferably has an average particle size of 0.1 to 100 μm, more preferably 0.5 to 70 μm, and further preferably 0.5 to 70 μm, from the viewpoint of uniform dispersibility in the produced flexible polyurethane foam. It is preferably 1 to 50 μm.
The "average particle size" referred to in the present invention refers to _{the particle size (D 50} ) at an integrated value of 50% in the particle size distribution obtained by the laser diffraction / scattering method. Specifically, a measured D ₅₀ value using a laser diffraction-scattering type particle size distribution measuring device "MT3300" (manufactured by Microtrac Bell Co., Ltd.).

When the mixed solution contains an inorganic filler, the content of the inorganic filler is appropriately adjusted according to physical properties such as the specific gravity of the produced flexible polyurethane foam, but is 30 mass by mass with respect to 100 parts by mass of the urethane prepolymer. The amount is preferably 1 part or less, more preferably 1 to 25 parts by mass, and further preferably 2 to 20 parts by mass.

In addition to the urethane prepolymer, the polyisocyanate compound (a), the foaming agent, the curing agent and the inorganic filler, the mixed solution contains, if necessary, a foam stabilizer, a catalyst, a solvent, a coloring agent, an antioxidant, and an ultraviolet absorber. And other additives may be included.

The foam stabilizer is added to obtain a flexible polyurethane foam having a more uniform pore size, density and the like. Examples of the foam stabilizer include surfactants, silicone oils and the like. These foam stabilizers may be used alone or in combination of two or more. Among the defoaming agents, a surfactant having a hydroxyl group at the molecular terminal and capable of chemically bonding with isocyanate is preferable because it is difficult to dissolve when it is put into a treatment tank as a microbial immobilization carrier for water treatment. .. Among the surfactants, nonionic surfactants, which have less foaming than anionic surfactants, are preferable.

The catalyst may be added to accelerate the reaction between the urethane prepolymer and the polyisocyanate compound (a). As the catalyst, a known catalyst used for the synthesis of flexible polyurethane foam can be used, for example, an amine catalyst such as triethylamine, triethylenediamine, diethanolamine, dimethylaminomorpholine, N-ethylmorpholin, tetramethylguanidine; Tin catalysts such as ate and dibutyltin dilaurate; other metal catalysts such as phenylmercury propionate and lead octenoate can be mentioned. Among the catalysts, amine catalysts are preferable.

When the mixed solution contains an additive, the content of the additive in the mixed solution is preferably 0.01 to 5% by mass, more preferably 0.1 to 3% by mass.

The method for mixing the components contained in the mixed solution is not particularly limited, but the urethane prepolymer and the polyisocyanate compound (a) are mixed in advance, and a foaming agent is added to the mixture to obtain the urethane prepolymer. It is preferable to foam the mixture containing the polyisocyanate compound (a). Ingredients other than the above may be added to a mixture containing the urethane prepolymer and the polyisocyanate compound (a) or a foaming agent in consideration of its characteristics.

<Foam container>
Foam container used in the present invention is not particularly limited, the temperature T _W of the walls mixed solution is in contact, the mixed solution was injected until foaming is completed, is within the range of 21-60 ° C. ..
Flexible polyurethane foams such as those used in water treatment microbial immobilization carriers generally generate heat when foamed. The temperature of the central part of the flexible polyurethane foam slab is high because the heat generated during foaming is trapped inside, but the temperature of the part near the side surface of the slab (the part close to the wall surface of the foam container) is lower than that of the central part. As a result, the reaction rate differs between the central portion and the portion close to the side surface, and as a result, the phenomenon that the physical properties such as the density, water swellability, and cell structure of the flexible polyurethane foam differ between the central portion and the portion close to the side surface is likely to occur. On the other hand, when the temperature of the foam container is higher than the central part of the slab of the flexible polyurethane foam, the reaction rate becomes faster in the part closer to the side surface than the central part, and as a result, the density, water swelling property of the flexible polyurethane foam, In addition, a phenomenon in which the physical properties such as the cell structure are different between the central portion and the portion close to the side surface is likely to occur, and the density is lowered as a whole. The temperature T _W of the walls within the above range, it is possible to suppress a rapid temperature drop or rise in temperature of the mixed solution present in the wall portion, as a result, the flexible polyurethane foam which is excellent in uniformity of physical properties, It can be manufactured efficiently.

Temperature T _W of the walls in the step of obtaining a flexible polyurethane foam, density, water-swellable, and the viewpoint of obtaining a flexible polyurethane foam which is excellent in homogeneity of the cell structure, and from the viewpoint of producing a flexible polyurethane foam efficiently, preferably It is 22 ° C. or higher, more preferably 23 ° C. or higher, still more preferably 24 ° C. or higher, and from the same viewpoint, preferably 55 ° C. or lower, more preferably 50 ° C. or lower, still more preferably 45 ° C. or lower.

The absolute value of the difference between the temperature T _W of the temperature T _S and the wall surface of the mixed solution is preferably 0 to 40 ° C.. Here, the "temperature T _S of the mixed solution" in the present invention refers to the temperature of the mixed solution immediately after the components of the mixed solution was stirred and mixed all. The absolute value of the difference between the temperature T _S and the wall temperature T _W of the mixed solution, With such a range, more density, water-swellable, and a flexible polyurethane foam which is excellent in homogeneity of the cell structure, more efficient Can be manufactured as a target.
Absolute value of the difference between the temperature T _W of the temperature T _S and the wall surface of the mixed solution, density, water-swellable, and the viewpoint of obtaining a flexible polyurethane foam which is excellent in homogeneity of the cell structure, and the production of flexible polyurethane foams efficient From the viewpoint, it is preferably 0 to 30 ° C, more preferably 0 to 25 ° C.

The shape of the foam container is preferably a cube type or a rectangular parallelepiped type from the viewpoint of efficiently producing the flexible polyurethane foam. Further, from the viewpoint of efficiently producing flexible polyurethane foam, the foam container preferably has a container body with an open upper surface and a lid for closing the open upper surface of the container body.
In the process of obtaining the flexible polyurethane foam, by using such a foam container and covering the upper surface of the foam container with a lid, it becomes possible to manufacture the flexible polyurethane foam having a desired shape, and the flexible polyurethane foam can be efficiently produced. Can be manufactured.
The temperature of the lid is not particularly limited, and the temperature may not be adjusted, and may be appropriately adjusted to a desired temperature such as the same temperature as the wall surface in contact with the mixed solution of the foam container.
Further, since the shape of the foam container is a cube or a rectangular parallelepiped, the shape of the flexible polyurethane foam can also be obtained as a cube or a rectangular parallelepiped. As a result, when the flexible polyurethane foam is cut for use in a desired microbial immobilization carrier for water treatment, the amount of waste is reduced, and efficient production can be achieved.

The height of the inner dimension of the foam container is preferably 300 mm to 1200 mm, more preferably 300 mm to 1200 mm, from the viewpoint of efficient production while ensuring the density, water swellability, and homogeneity of the cell structure of the flexible polyurethane foam. It is 400 mm to 1000 mm, more preferably 500 mm to 800 mm.

The volume capable of accommodating the mixed solution inside the foam container is preferably 0.03 to 0.8 m ³ from the viewpoint of efficiently producing the flexible polyurethane foam, and more preferably 0.1 to 0. .6m ^3, more preferably from 0.2 to 0.5 m ^3.

The method of injecting the mixed solution into the foam container is not particularly limited, but can be carried out by, for example, a method of mixing and injecting using a mixing head.
When injecting the mixed solution into the foam container, it is preferable to inject the mixed solution along the wall surface of the foam container. By injecting in this way, the mixed solution being injected can be injected below the already injected mixed solution, and bubbles formed by foaming contained in the already injected mixed solution are injected later. It is possible to prevent the mixture from being crushed by the mixed solution. As a result, a flexible polyurethane foam having higher density, water swellability, and cell structure homogeneity can be efficiently produced.
The injection rate when injecting the mixed solution into the foam container is preferably 5 to 200 kg / min, more preferably 50 to 150 kg, from the viewpoint of obtaining a flexible polyurethane foam having excellent density, water swellability, and homogeneity of the cell structure. / Min, more preferably 75-125 kg / min.

When the upper surface of the foam container is covered, the mixed solution may be injected into the foam container with the upper surface partially or completely covered, or the mixed solution may be covered in the middle of the injection of the mixed solution. The lid may be closed before the injection is complete and the foaming of the mixed solution is complete.

<Soft polyurethane foam>
The flexible polyurethane foam obtained by the present invention is obtained by injecting a mixed solution containing a urethane prepolymer and a polyisocyanate compound (a) into a foam container and foaming the foam, and the swelling density at the time of water swelling is 25 to 25 to. It is 70 kg / m ³ , the average number of pores at the time of water swelling is 9 to 30/25 mm, and the volume swelling rate expressed by the ratio of the volume at the time of water swelling to the volume in the absolute dry state is 110 to 1000%. be.

Swelling density during the water swelling of the soft polyurethane foam, as applied to microbial immobilization carrier for water treatment, preferably 28~60kg / m ^3, more preferably 28.5~50kg / m ^{3.
The flexible polyurethane foam having a swelling density of less than 25 kg / m 3} at the time of water swelling has too little resin, has low strength, and is easily deformed. There is a risk of inconveniences such as clogging of the screen, deformation of the screen, passing through the screen, and leakage from the processing tank. Further, when the amount of resin is small, it is vulnerable to physical wear and the volume is reduced (consumed) quickly.
On the other hand, if the swelling density at the time of water swelling exceeds 70 kg / m ³ , the raw material cost becomes excessive, which is not preferable.

The cell structure of the flexible polyurethane foam includes microorganisms, oxygen required for respiration of microorganisms, nutrients necessary for activity and proliferation of microorganisms, and objects (organic substances (hydrogens), nitrogen compounds, phosphorus) to be removed by microorganisms. From the viewpoint of allowing a substrate such as compound) to sufficiently penetrate into the inside and immobilizing the microorganism on the microorganism immobilization carrier for water treatment, it is desirable to have a continuous ventilation hole structure. The average number of pores at the time of water swelling is 9 to 30 pores / 25 mm, preferably 10 to 25 pores / 25 mm, and more preferably 11 to 20 pores / 25 mm.

The "average number of pores at the time of water swelling" refers to the average value of the number of pores existing on any three 25 mm long straight lines of the flexible polyurethane foam at the time of water swelling. Specifically, it can be measured by the method described in Examples described later.

The flexible polyurethane foam obtained by the present invention has a volume swelling rate of 110 to 1000%, preferably 120 to 800%, more preferably 140 to 500, still more preferably 140 to 500, from the viewpoint of good hydrophilicity and the like. Is 150-300%.
The flexible polyurethane foam having a volume swelling rate of less than 110% cannot be said to have sufficient compatibility with water, and cannot be said to be excellent in hydrophilicity.
On the other hand, the flexible polyurethane foam having a volume swelling rate of more than 1000% is not preferable because it becomes difficult to maintain the durability required as a microbial immobilization carrier for water treatment.

Further, absolute dry density representing the density in absolutely dry conditions, preferably 48~130kg / ^{m 3,} more preferably 49~110kg / ^{m 3,} more preferably a 50~90kg / ^{m 3.}

The average pore diameter at the time of water swelling is preferably 0.25 to 2.00 mm, more preferably 0.50 to 1.90 mm, and further preferably 0.70 to 1.80 mm. When the average pore diameter at the time of water swelling is within this range, microorganisms, oxygen required for respiration of microorganisms, nutrients necessary for activity and proliferation of microorganisms, and objects removed by microorganisms (organic matter (hydrogen)) , Nitrogen compound, phosphorus compound) and the like can be sufficiently invaded inside to facilitate the immobilization of microorganisms.
Here, the "average pore diameter at the time of water swelling" means that the major axis and the minor axis are measured for one pore in the cross section of the flexible polyurethane foam at the time of water swelling, and the average value of the major axis and the minor axis is the diameter. In the same way, for a total of 50 pores, the average value of the diameters when they are regarded as perfect circles is used.

Further, from the viewpoint of maintaining a sufficient pore diameter and surface area, the width of the minimum portion of the skeleton between adjacent pores at the time of water swelling is preferably 0.05 to the skeleton portion of the flexible polyurethane constituting the cell structure. It is 0.50 mm, more preferably 0.07 to 0.40 mm, still more preferably 0.10 to 0.30 mm.
Further, as a cell structure suitable for immobilizing many microorganisms in water, the skeleton portion has a partially membranous structure between adjacent pores rather than a so-called rib structure composed of a thin rod-shaped skeleton. It is preferable to have a so-called wall structure having a large surface area by being partitioned by a wall surface.

The flexible polyurethane foam is preferably produced in the form of a slab from the viewpoint of efficiently producing the flexible polyurethane foam. The height of the flexible polyurethane foam produced as a slab is preferably 300 mm to 1200 mm, more preferably 400 mm to 1000 mm, and further preferably 500 mm to 800 mm from the viewpoint of efficiently producing the flexible polyurethane foam.

The volume of flexible polyurethane foams, from the viewpoint of producing a flexible polyurethane foam efficiently, preferably 0.03～0.8M ^3, more preferably 0.1～0.6M ^3, more preferably 0.2 It is ~ 0.5 m ^3.
Here, the "volume of the flexible polyurethane foam" referred to in the present invention is assumed to include the pores of the flexible polyurethane foam, and is a volume obtained based on the outer dimensions of the flexible polyurethane foam.

The flexible polyurethane foam can be provided as a microbial immobilization carrier for water treatment by, for example, cutting a slab-like product into a desired size or the like.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.

[Manufacturing raw materials]
Details of the raw material compounds used in the production of the flexible polyurethane foam are shown below.
-Urethane prepolymer (1): TDI-modified EO-PO copolymer; EO / PO mass ratio: 55/45, number average molecular weight of EO-PO copolymer: 2700 (theoretical value), containing NCO (isocyanate group) Amount: 4.5% by mass, viscosity (25 ° C): 8000 mPa · s
-Urethane prepolymer (2): TDI-modified EO-PO copolymer; EO / PO mass ratio: 50/50, number average molecular weight of EO-PO copolymer: 2500 (theoretical value), containing NCO (isocyanate group) Amount: 4.5% by mass, viscosity (25 ° C): 8000 mPa · s
Polyisocyanate compound (a): TDI; "Coronate (registered trademark) T-80", manufactured by Tosoh Corporation, 2,4-TDI / 2,6-TDI mass ratio: 80/20
-Inorganic filler: barium sulfate; manufactured by Sakai Chemical Industry Co., Ltd., average particle size 20 to 30 μm, specific gravity 4.3
-Hardener / foaming agent: water-foaming agent: nonionic surfactant; "New Pole (registered trademark) PE-75", manufactured by Sanyo Chemical Industries, Ltd.-Catalyst: bis (2-dimethylaminoethyl) ether; "Niax (registered trademark) Catalyst A-1", manufactured by Momentive Performance Materials, Inc.

<Example 1>
400 kg of TDI-modified EO-PO copolymer (urethane prepolymer (1)), 53.4 kg of TDI (polyisocyanate compound (a)), and 50.0 kg of barium sulfate (inorganic filler) were stirred and mixed to prepare A1 solution. ..
Separately from the A1 liquid, 350 kg of water and 7 kg of the foam stabilizer were stirred and mixed to prepare the B1 liquid.
Next, the A1 liquid (28 ° C.) and the B1 liquid (14 ° C.) were pumped from the respective tanks to the mixing head at a compounding mass ratio of 1.48 (A1 liquid / B1 liquid). Wherein the mixing head, a liquid material mixture of Solution A1 and B1 liquid, vertical 800 mm × inner dimensions transverse 800 mm × height 660 mm, wall temperature _{T W} is ejected in the bubbling container is 25 ° C., after completion of injection, foam containers Was closed and allowed to stand for 2 hours to produce a slab-shaped flexible polyurethane foam.
By the above method, a slab-shaped flexible polyurethane foam was produced twice.

<Example 2 and Comparative Examples 1 and 2>
The wall surface temperature T _W, respectively the temperature shown in Table 1, and otherwise in the same manner as in Example 1 to produce flexible polyurethane foams. A slab-shaped flexible polyurethane foam was produced 5 times in Example 2, 1 time in Comparative Example 1, and 4 times in Comparative Example 2.

<Example 3>
400 kg of TDI-modified EO-PO copolymer (urethane prepolymer (2)), 53.4 kg of TDI (polyisocyanate compound (a)), and 50.0 kg of barium sulfate (inorganic filler) were stirred and mixed to prepare an A2 solution. ..
Separately from the A2 solution, 350 kg of water, 29 kg of the defoaming agent, and 6.7 kg of the catalyst were stirred and mixed to prepare the B2 solution.
Next, using the A2 solution (28 ° C.) and B2 liquid (14 ° C.), a wall surface temperature T _W to a temperature shown in Table 1, and otherwise in the same manner as in Example 1 to produce flexible polyurethane foams. The slab-shaped flexible polyurethane foam was produced twice.

[evaluation]
<Yield>
The slab-shaped flexible polyurethane foams obtained in the above Examples and Comparative Examples were sliced horizontally at a position 10 mm below the top and sliced horizontally at a position 10 mm above the bottom surface.
Subsequently, it was sliced horizontally at intervals of 10 mm to obtain a flexible polyurethane foam sheet having a thickness of 10 mm.
Each of the obtained flexible polyurethane foam sheets was punched in the thickness direction so as to obtain a flexible polyurethane foam piece having a length of 10 mm, a width of 10 mm, and a thickness of 10 mm (hereinafter, also referred to as "soft polyurethane foam piece"). After punching, the flexible polyurethane foam piece having all the inside of the region X 10 mm or more inside the side peripheral surface of the flexible polyurethane foam sheet was collected, and the flexible polyurethane having all or part outside the region X was collected. The foam pieces were removed and discarded.

The yield of the flexible polyurethane foam produced in the above Examples and Comparative Examples was evaluated by the following method.
Specifically, the yield was defined as the value obtained by dividing the total weight of the recovered flexible polyurethane foam pieces by the weight of the mixed solution injected into the foam container and multiplying by 100.
Table 1 summarizes the yield evaluation results.

<Physical characteristics>
For each of the flexible polyurethane foams produced in the above Examples and Comparative Examples, a flexible polyurethane foam piece having a length of 10 mm, a width of 10 mm, and a height of 10 mm was produced and used as a sample in the same manner as in the yield evaluation.
In each case, the central portion of the slab-shaped flexible polyurethane foam obtained in the examples (at a position 300 mm or more away from each wall surface of the foam container) and the vicinity of the wall surface of the foam container (between 10 and 50 mm from the wall surface of the foam container). The following physical properties were evaluated for the two types of samples present in).
In terms of physical properties, the soft polyurethane foam produced for the first time was measured.

(Absolute dry density)
The length of each side of the sample in the absolutely dry state was measured with a caliper, and the volume calculated as the product of the measured lengths of each side was regarded as _{the volume V d in the absolutely dry state.
The value obtained by dividing the mass M d} of the sample obtained in the above-mentioned state in the absolutely dry state by the volume V _d in the state of absolute dry was defined as the absolute dry density.

(Swelling density)
The length of each side of the sample was measured with a caliper while the sample was immersed in water at 25 ° C. for 1 hour and then placed flat and immersed in water. The volume calculated as the product of the measured lengths of each side was regarded as _{the volume V w at the time of water swelling of the sample.
The value obtained by dividing the mass M d} in the absolutely dry state by _{the volume V w} at the time of water swelling was defined as the swelling density.

(Volume swelling rate)
_{The ratio of the volume V w} at the time of water swelling to the volume V _{d in the} absolutely dry state was determined as the volume swelling rate (%).

(Average number of pores)
After measuring the volume at the time of water swelling in the above, the central portion of the surface of the sample was colored with red ink. A straightedge was applied to the colored portion, and a photograph was taken so that the colored portion and the scale of the straightedge were included. In the enlarged image of the photograph taken, the number of pores observed on an arbitrary parallel line with the straightedge was counted within the range of the 25 mm interval position of the scale at any part of the straightedge. The same measurement was performed at any three places, and the average value of the number of pores measured three times was taken as the average number of pores per 25 mm at the time of water swelling.

In Examples 1 and 2 _{, good yields were obtained by setting the wall surface temperature TW} to 25 ° C. and 30 ° C. That is, by the wall temperature T _W and 21-60 ° C., it has been found that it is possible to produce a flexible polyurethane foam efficiently. Further, the obtained polyurethane foam has a predetermined swelling density at the time of water swelling, an average number of pores at the time of water swelling, and a volume swelling rate, and the difference in physical property values between the central portion and the vicinity of the side surface is small, and the homogeneity of the physical properties is small. It was confirmed that it was excellent.
On the other hand, in Comparative Examples 1 and 2 has a low wall surface temperature T _W of the foam container, the mixed solution near the walls affected by this, a flexible polyurethane foam after production has a high height of the central portion, the foaming solution It had a mountain-like shape with a low height around the wall surface. As a result, the yield was low, and there were many cases where the difference in physical property values was large between the central portion of the flexible polyurethane foam and the vicinity of the wall surface.
As described above, according to the production method of the present invention, the batch method has a predetermined swelling density at the time of water swelling, an average number of pores at the time of water swelling, and a volume swelling rate, and has density, water swelling property, and volume swelling rate. A flexible polyurethane foam having excellent cell structure homogeneity can be efficiently produced.

Claims (7)

A method for producing a flexible polyurethane foam used as a microbial immobilization carrier for water treatment.
It has a step of injecting a mixed solution containing a urethane prepolymer and a polyisocyanate compound (a) into a foam container and foaming the mixture to obtain a flexible polyurethane foam.
Temperature _{T W} of the wall in which the mixed solution of the foam container is in contact is a 21-60 ° C.,
The flexible polyurethane foam has a swelling density of 25 to 70 kg / m ³ at the time of water swelling, an average number of pores of 9 to 30 at the time of water swelling / 25 mm, and a volume at the time of water swelling with respect to a volume in an absolutely dry state. A method for producing a flexible polyurethane foam, wherein the volume swelling rate represented by the ratio of The method for producing a flexible polyurethane foam according to claim 1, wherein the upper surface of the foam container is covered with a lid in the step of obtaining the flexible polyurethane foam. The method for producing a flexible polyurethane foam according to claim 1 or 2, wherein the height of the flexible polyurethane foam is 300 mm to 1200 mm. The method for producing a flexible polyurethane foam according to any one of claims 1 to ³ , wherein the volume of the flexible polyurethane foam is 0.03 to 0.8 m 3. The method for producing a flexible polyurethane foam according to any one of claims 1 to 4, wherein the mixed solution is injected at an injection rate of 5 to 200 kg / min. The method for producing a flexible polyurethane foam according to any one of claims 1 to 5, wherein the mixed solution is injected along the wall surface of the foam container. The absolute value of the difference between the temperature T _W of the temperature T _S and the wall surface of the mixed solution, process for producing a flexible polyurethane foam according to claim 1 which is 0 to 40 ° C..