CN114269804A - Process for preparing flexible polyurethane foam - Google Patents

Process for preparing flexible polyurethane foam Download PDF

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Publication number
CN114269804A
CN114269804A CN202080058755.0A CN202080058755A CN114269804A CN 114269804 A CN114269804 A CN 114269804A CN 202080058755 A CN202080058755 A CN 202080058755A CN 114269804 A CN114269804 A CN 114269804A
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China
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polyurethane foam
flexible polyurethane
water
mixed solution
volume
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Granted
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CN202080058755.0A
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CN114269804B (en
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近藤智幸
广川惣一郎
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Nisshinbo Chemical Inc
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Nisshinbo Chemical Inc
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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F3/00—Biological treatment of water, waste water, or sewage
    • C02F3/02—Aerobic processes
    • C02F3/10—Packings; Fillings; Grids
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/08—Processes
    • C08G18/10—Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W10/00—Technologies for wastewater treatment
    • Y02W10/10—Biological treatment of water, waste water, or sewage

Abstract

A process for producing a flexible polyurethane foam for use as a carrier for immobilizing microorganisms for water treatment, which comprises a step of injecting a mixed solution containing a urethane prepolymer and a polyisocyanate compound (a) into a foaming vessel and foaming the mixed solution to obtain a flexible polyurethane foam, wherein the temperature T of the wall surface of the foaming vessel in contact with the mixed solution is the temperature T of the wall surfaceWIs 21 to 60 ℃, and the swelling density of the flexible polyurethane foam is 25 to 70kg/m when swelling with water3The average number of pores in swelling with water is9 to 30 per 25mm, and a volume swelling ratio of 110 to 1000% in terms of a ratio of a volume when swollen with water to a volume in an absolutely dry state.

Description

Process for preparing flexible polyurethane foam
Technical Field
The present invention relates to a process for the preparation of flexible polyurethane foams.
Background
Conventionally, carriers comprising flexible polyurethane foam having excellent microorganism immobilization performance, hydrophilicity, durability, and water sedimentation properties have been studied as carriers used in sewage treatment apparatuses for treating sewage with microorganisms.
Patent document 1 describes a water-swellable carrier for water treatment, which is composed of a polyurethane foam having pores communicating from the surface to the inside of the carrier, wherein the polyurethane foam is a cube, a rectangular parallelepiped or a cylinder, the length of all sides of the cube or the rectangular parallelepiped after water swelling or the diameter and the height of the cylinder after water swelling is 8 to 100mm, the average number of pores after water swelling is 10 to 50/25 mm, and the volume swelling ratio is 150 to 1000%.
Patent document 2 describes a water-swellable polyurethane foam to which drug resistance is imparted, a method for producing the same, and a support for a bioreactor using the same, wherein the polyurethane foam is obtained by reacting a polyisocyanate compound (a)1) A hydrophilic urethane prepolymer (c) having at least 2 terminal isocyanate groups in 1 molecule obtained by reaction with a polyol compound (b), and a polyisocyanate compound (a)2) The polyisocyanate compound (a) to be used in the polyurethane foam of (1)1) And/or (a)2) At least a part of (a) is a purified diphenylmethane diisocyanate substantially free of polymerizable components.
Documents of the prior art
Patent document
Patent document 1: chinese utility model No. 204454746 specification
Patent document 2: japanese patent laid-open publication No. 2004-359950
Disclosure of Invention
The flexible polyurethane foam for a microorganism-immobilized carrier for water treatment is generally prepared by mixing and foaming a polyisocyanate compound and a polyol compound, or a urethane prepolymer and a polyisocyanate compound with a foaming agent, a foam stabilizer, and the like. Among them, in the case of producing a flexible polyurethane foam by a batch method, production efficiency can be improved by increasing the floor area or height of each slab (スラブ), but when the slab becomes large, the amount of the mixed liquid to be charged increases, and there is an upper limit to increase the amount of the discharged liquid, and when the mixed liquid is charged into the foaming vessel, since the mixed liquid charged first is solidified, the density, water-swelling property and cell structure (hereinafter referred to as "cell structure") are greatly varied in the flexible polyurethane foam slab, and it is difficult to ensure uniformity of physical properties.
On the other hand, when the mat becomes small, since the density, the water swelling property and the cell structure are different between the central portion and the peripheral portion (upper surface, lower surface and side surface) in the mat, the portion ensuring the uniformity of the physical properties is reduced, resulting in a decrease in the yield.
In addition, in the case of producing a polyurethane foam sheet by slicing a flexible polyurethane foam horizontally (hereinafter, also referred to as "horizontal direction") on the bottom surface of a slab, the area of the arched portion is small at the time of slicing, the usable range is small, and there is a problem of low production efficiency, and the like.
The present invention has been made to solve the above problems, and an object thereof is to provide a method for efficiently producing a flexible polyurethane foam having excellent density, water-swelling property, and homogeneity of cell structure by a batch method.
The present invention has been completed based on the following findings: a flexible polyurethane foam excellent in density, water-swellability, and homogeneity of cell structure can be efficiently obtained by a batch method in which a mixed solution containing a predetermined component is poured into a foaming vessel having a predetermined wall surface temperature and foamed.
Namely, the present invention provides the following [1] to [7 ].
[1] A preparation method of soft polyurethane foam, which is a preparation method of soft polyurethane foam for a microorganism immobilization carrier for water treatment,
the production process comprises a step of injecting a mixed solution containing a urethane prepolymer and a polyisocyanate compound (a) into a foaming vessel and foaming the mixture to obtain a flexible polyurethane foam,
temperature T of a wall surface of the foaming container in contact with the mixed solutionWThe temperature is between 21 and 60 ℃,
the soft polyurethane foam has a swelling density of 25 to 70kg/m when swollen with water3The average number of pores in the swollen state is 9 to 30 per 25mm, and the volume swelling ratio expressed by the ratio of the volume in the swollen state to the volume in the completely dry state is 110 to 1000%.
[2] The process according to the above [1], wherein in the step of obtaining the flexible polyurethane foam, a cap is placed on the upper surface of the foam container.
[3] The process according to the above [1] or [2], wherein the flexible polyurethane foam has a height of 300 to 1200 mm.
[4]According to the above [1]～[3]The process for producing a flexible polyurethane foam according to any one of the above, wherein the volume of the flexible polyurethane foam is from 0.03 to 0.8m3。
[5] The process for producing a flexible polyurethane foam according to any one of the above [1] to [4], wherein the mixed solution is injected at an injection rate of 5 to 200 kg/min.
[6] The process according to any one of the above [1] to [5], wherein the mixed solution is injected along a wall surface of a foaming vessel.
[7]According to the above [1]～[6]The process for producing a flexible polyurethane foam as described in any one of the above, wherein the temperature T of the mixed solutionSTemperature T of the wall surfaceWThe absolute value of the difference is 0 to 40 ℃.
According to the production process of the present invention, a flexible polyurethane foam excellent in density, water-swellability, and homogeneity of cell structure can be efficiently obtained by a batch process.
Detailed Description
The process for producing a flexible polyurethane foam of the present invention is a process for producing a flexible polyurethane foam for a microorganism-immobilized carrier for water treatment.
The production method comprises a step of injecting a mixed solution containing a urethane prepolymer and a polyisocyanate compound (a) into a foaming vessel and foaming the mixed solution to obtain a flexible polyurethane foam, wherein the temperature T of a wall surface of the foaming vessel in contact with the mixed solutionWIs 21 to 60 ℃.
The soft polyurethane foam has a swelling density of 25 to 70kg/m when swollen with water3The average number of pores in the swollen state is 9 to 30 per 25mm, and the volume swelling ratio expressed by the ratio of the volume in the swollen state to the volume in the completely dry state is 110 to 1000%.
Here, the term "when swollen with water" in the present invention means a state in which the flexible polyurethane foam is immersed in water at 25 ℃ for 1 hour.
The "swollen density" in the present invention means a value obtained by dividing the mass in an absolutely dry state by the volume at the time of swelling with water. The swelling density can be measured specifically by the method described in the examples described later.
The "absolutely dry state" means a state in which the flexible polyurethane foam is dried at 100 ℃ and no mass reduction is observed. Sometimes also referred to as an absolute dry state.
The "volume swelling ratio" in the present invention means a value represented by a ratio of a volume when swollen with water to a volume in an absolutely dry state. The "volume in the oven-dried state" also includes pores of the flexible polyurethane foam, and is a volume determined from the external dimensions of the flexible polyurethane foam in the oven-dried state. The "volume when swollen with water" also includes the air pores of the flexible polyurethane foam and water absorbed by the pores, and means a volume determined from the external dimensions of the state in which the flexible polyurethane foam is swollen. For example, when the flexible polyurethane foam is in a rectangular parallelepiped shape, a value calculated as a product of three side lengths of a length, a width, and a height of the rectangular parallelepiped is taken as a volume of the flexible polyurethane foam.
As described above, by injecting the mixed solution into a foaming vessel whose wall surface temperature is controlled and foaming the mixed solution, a flexible polyurethane foam excellent in density, water-swellability, and homogeneity of cell structure can be efficiently produced by a batch method.
[ procedure for obtaining Flexible polyurethane foam ]
The step of obtaining a flexible polyurethane foam is a step of injecting a mixed solution containing a urethane prepolymer and a polyisocyanate compound (a) into a foaming vessel and foaming the mixed solution to obtain the flexible polyurethane foam, wherein the temperature T of a wall surface of the foaming vessel which is in contact with the mixed solution isW(hereinafter also referred to as the temperature T of the wall surface)W) Is 21 to 60 ℃. In addition, the temperature T of the wall surfaceWThe temperature of the mixed solution is in the range of 21-60 ℃ until foaming is completed.
< 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 excess amount, preferably 110% or more, of the molar equivalent ratio of isocyanate groups to hydroxyl groups of the polyol compound, and has 2 or more isocyanate groups in 1 molecule. The urethane prepolymer may be used alone in 1 kind, or may be used in combination in 2 or more kinds.
By using such a prepolymer as a raw material compound, a flexible polyurethane foam excellent in water-swelling property, small in variation in density and cell structure, and excellent in homogeneity can be easily obtained.
Examples of the urethane prepolymer include polyether urethane prepolymers having 2 or more isocyanate groups in 1 molecule obtained by reacting a polyether polyol with a polyisocyanate compound (b), and polyester urethane prepolymers having 2 or more isocyanate groups in 1 molecule obtained by reacting a polyester polyol with a polyisocyanate compound (b).
Both polyether polyols and polyester polyols can impart hydrophilicity, but polyether polyols have better hydrolysis resistance than polyester polyols. In the present invention, since the produced flexible polyurethane foam is used in water as a water treatment microorganism-immobilizing carrier, polyether urethane prepolymers are more preferable than polyester urethane prepolymers in view of durability of the flexible polyurethane foam.
From the viewpoint of ease of handling and the like, the viscosity of the urethane prepolymer is preferably not too high, and the viscosity is preferably 300 to 9500mPa · s, more preferably 300 to 9000mPa · s, and still more preferably 300 to 8500mPa · s, as measured at 25 ℃ with a spindle viscometer.
Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, and the like. They are obtained by ring-opening polymerization of Ethylene Oxide (EO), Propylene Oxide (PO) and tetrahydrofuran, respectively, which are cyclic ether compounds. The polyether polyol may be used alone in 1 kind, or may be used in combination in 2 or more kinds. Further, a copolymer of a cyclic ether compound may be used, and since it is used in water as a carrier for immobilizing microorganisms for water treatment, an EO-PO copolymer is particularly preferable from the viewpoint of hydrophilicity of a flexible polyurethane foam.
The monomer composition ratio of EO and PO in the EO-PO copolymer is preferably 70/30-30/70, more preferably 65/35-40/60, and further preferably 60/40-50/50 in terms of mass ratio.
The polyisocyanate compound (b) is a compound having 2 or more isocyanate groups in 1 molecule, and is not particularly limited. Examples of the polyisocyanate compound (b) include Tolylene Diisocyanate (TDI), xylylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, biphenyl diisocyanate, diphenylether diisocyanate, tolidine diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate. The polyisocyanate compound (b) may be used alone in 1 kind or in combination of 2 or more kinds.
When the polyisocyanate compound (b) is a compound having isomers, it may be only 1 of the isomers, or may be a mixture of 2 or more isomers. For example, TDI has two isomers of toluene-2, 4-diisocyanate (2,4-TDI) and toluene-2, 6-diisocyanate (2,6-TDI), only one of 2,4-TDI and 2,6-TDI may be used, or a mixture of both may be used.
From the viewpoint of the degree of thickening of the obtained prepolymer, the polyisocyanate compound (b) is preferably toluene diisocyanate.
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 still more preferably 30 to 60% by mass.
(polyisocyanate Compound (a))
The polyisocyanate compound (a) is not particularly limited, and specific examples thereof include the same compounds as exemplified for the polyisocyanate compound (b) used for the synthesis of the urethane prepolymer. The polyisocyanate compound (a) may be used alone in 1 kind or in combination of 2 or more kinds.
The polyisocyanate compound (a) may be the same as or different from the polyisocyanate compound (b) used for the synthesis of the urethane prepolymer.
The polyisocyanate compound (a) is preferably tolylene diisocyanate from the viewpoint of obtaining a flexible polyurethane foam for a water-treatment microorganism-immobilized carrier having excellent 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 still more preferably 2 to 10% by mass.
The mixed solution preferably contains a foaming agent.
Examples of the blowing agent include hydrocarbons such as water, Hydrofluorocarbons (HFC), Hydrofluoroolefins (HFO), Hydrochlorofluoroolefins (HCFO), carbon dioxide, and cyclopentane. These blowing agents may be used alone in 1 kind, or may be used in combination in 2 or more kinds. Among the above blowing agents, water is preferable from the viewpoints 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 which affects the microorganism immobilization performance of the microorganism-immobilized carrier for water treatment.
The mixed solution preferably contains a curing agent. The curing agent is added for crosslinking and curing the urethane prepolymer and the polyisocyanate compound (a), and may be referred to as a crosslinking agent.
Examples of the curing agent include water; polyhydric alcohols such as glycerin, 1, 4-butanediol, and diethylene glycol; and amine compounds such as ethanolamines and polyethylenepolyamines. Further, there may be mentioned polyols obtained by ring-opening polymerization of ethylene oxide, propylene oxide, etc. onto the above-mentioned polyol, and products obtained by adding a small amount of propylene oxide onto the above-mentioned amine compound. These curing agents may be used alone in 1 kind, or may be used in combination in 2 or more kinds. Among the curing agents, water is preferable from the viewpoints of reactivity, ease of handling, cost, and the like.
The content of the curing agent in the mixed solution may be appropriately set in consideration of flexibility, elasticity, strength, and the like of the flexible polyurethane foam which affect the microorganism immobilization performance and strength of the microorganism immobilization carrier for water treatment.
As described above, water is preferably used as a foaming agent and a curing agent in the production of a flexible polyurethane foam used as a carrier for immobilizing microorganisms for water treatment. When water is used as the blowing 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. The specific gravity of the flexible polyurethane foam prepared can be adjusted by using the inorganic filler, and when the microorganism-immobilized carrier for water treatment prepared by using the flexible polyurethane foam is put into water, the carrier can be rapidly precipitated into the water.
Examples of the inorganic filler include barium sulfate, calcium carbonate, talc, silica, alumina, activated carbon, zeolite, and the like. The inorganic filler may be used alone in 1 kind, or may be used in combination in 2 or more kinds. The inorganic filler is preferably an inorganic filler having a small bulk volume, and barium sulfate having a large specific gravity is preferred from this viewpoint.
The average particle diameter of the inorganic filler is preferably 0.1 to 100. mu.m, more preferably 0.5 to 70 μm, and still more preferably 1 to 50 μm, from the viewpoint of uniform dispersibility in the flexible polyurethane foam to be produced.
The "average particle diameter" in the present invention refers to the particle diameter (D) at which the cumulative value of the particle size distribution obtained by the laser diffraction scattering method is 50%50). Specifically, D was measured using a laser diffraction scattering particle size distribution measuring apparatus "MT 3300" (manufactured by Microtrac BEL Co., Ltd.)50The value is obtained.
When the mixed solution contains an inorganic filler, the content of the inorganic filler may be appropriately adjusted depending on physical properties such as a specific gravity of the flexible polyurethane foam to be produced, and is preferably 30 parts by mass or less, more preferably 1 to 25 parts by mass, and still more preferably 2 to 20 parts by mass, based on 100 parts by mass of the urethane prepolymer.
The mixed solution may contain additives such as a foam stabilizer, a catalyst, a solvent, a colorant, an antioxidant, and an ultraviolet absorber, as needed, in addition to the urethane prepolymer, the polyisocyanate compound (a), the blowing agent, the curing agent, and the inorganic filler.
The foam stabilizer is added to obtain a flexible polyurethane foam having more uniform cell size, density, and the like. Examples of the foam stabilizer include a surfactant, a silicone oil, and the like. These foam stabilizers may be used alone in 1 kind, or may be used in combination in 2 or more kinds. Among the foam stabilizers, surfactants having a hydroxyl group at the molecular end and capable of chemically bonding to isocyanate are preferable from the viewpoint of being difficult to elute when charged into a treatment tank as a microorganism-immobilized carrier for water treatment. Among the surfactants, nonionic surfactants which foam less than anionic surfactants are preferred.
The catalyst may be added in order to promote the reaction of the urethane prepolymer with the polyisocyanate compound (a). As the catalyst, known catalysts used in the synthesis of flexible polyurethane foams can be used, and examples thereof include amine catalysts such as triethylamine, triethylenediamine, diethanolamine, dimethylaminomeorpholine, N-ethylmorpholine, tetramethylguanidine, and the like; tin catalysts such as stannous octoate and dibutyltin dilaurate; and other metal catalysts such as phenylmercuric propionate and lead octenoate. Among the catalysts, an amine catalyst is preferable.
When the additive is contained in the mixed solution, the content of the additive in the mixed solution is preferably 0.01 to 5% by mass, and more preferably 0.1 to 3% by mass.
The method of mixing the components contained in the mixed solution is not particularly limited, and it is preferable to foam a mixture containing the urethane prepolymer and the polyisocyanate compound (a) by mixing the urethane prepolymer and the polyisocyanate compound (a) in advance and adding a foaming agent to the mixture. In addition to the above components, the components may be added to a mixture containing a urethane prepolymer and a polyisocyanate compound (a) or a blowing agent in consideration of the characteristics thereof.
< foaming Container >
The foaming vessel used in the present invention is not particularly limited, but the temperature T of the wall surface in contact with the mixed solutionWThe temperature of the mixed solution is in the range of 21-60 ℃ until foaming is completed.
In general, a flexible polyurethane foam used for a microorganism-immobilized carrier for water treatment generates heat during foaming. The central portion of the slab of the flexible polyurethane foam is retained inside by heat generated during foaming and the temperature rises, but since the temperature of the portion near the side surface of the slab (the portion near the wall surface of the foaming vessel) is lower than that of the central portion, the reaction rates of the central portion and the portion near the side surface are different, and as a result, a phenomenon in which physical properties such as the density, the water-swelling property, and the cell structure of the flexible polyurethane foam are different between the central portion and the portion near the side surface easily occurs. On the other hand, when the temperature of the foaming vessel is higher than the center portion of the slab of the flexible polyurethane foam, the reaction rate is higher in the portion near the side surface than in the center portion, and as a result, the physical properties such as the density, water-swelling property, and cell structure of the flexible polyurethane foam are different between the center portion and the portion near the side surface, and the density is also decreased as a whole. By making the temperature T of the wall surfaceWWithin the above range, a rapid temperature decrease and a rapid temperature increase of the mixed solution present in the wall surface portion can be suppressed, and as a result, a flexible polyurethane foam having excellent homogeneity of physical properties can be efficiently produced.
The temperature T of the wall surface in the step of obtaining a flexible polyurethane foam is determined from the viewpoint of obtaining a flexible polyurethane foam having excellent density, water swellability and homogeneity of the cell structure and from the viewpoint of efficiently producing a flexible polyurethane foamWPreferably 22 ℃ or higher, more preferably 23 ℃ or higher, and still more preferably 24 ℃ or higher, and from the same viewpoint, preferably 55 ℃ or lower, more preferably 50 ℃ or lower, and still more preferably 45 ℃ or lower.
In addition, the temperature T of the mixed solutionSTemperature T with wall surfaceWThe absolute value of the difference is preferably 0 to 40 ℃. Here, the "temperature T of the mixed solution" in the present inventionS"means the temperature of the mixed solution immediately after all the components of the mixed solution are mixed and stirred. By controlling the temperature T of the mixed solutionSTemperature T with wall surfaceWWhen the absolute value of the difference is within such a range, a flexible polyurethane foam having more excellent density, water-swellability, and homogeneity of the cell structure can be produced more efficiently.
The temperature T of the mixed solution is set so that the flexible polyurethane foam is obtained which is excellent in the density, water swellability and homogeneity of the cell structure and the flexible polyurethane foam is efficiently producedSTemperature T with wall surfaceWThe absolute value of the difference is preferably 0 to 30 ℃, more preferably 0 to 25 ℃.
The shape of the foaming container is preferably a cubic shape or a rectangular parallelepiped shape from the viewpoint of efficiently producing the flexible polyurethane foam. In addition, from the viewpoint of efficiently producing the flexible polyurethane foam, the foaming container preferably has a container body whose upper surface is open and a lid that closes the open upper surface of the container body.
In the step of obtaining a flexible polyurethane foam, by using such a foaming container and capping the upper surface of the foaming container, a flexible polyurethane foam having a desired shape can be produced, and a flexible polyurethane foam can be efficiently produced.
The temperature of the lid is not particularly limited, and may be adjusted to an appropriate desired temperature such as the same temperature as the wall surface of the foamer container that contacts the mixed solution, without adjusting the temperature.
Further, since the shape of the foaming container is a cubic shape or a rectangular parallelepiped shape, the shape of the flexible polyurethane foam can be obtained as a cube or a rectangular parallelepiped. As a result, when the flexible polyurethane foam is cut for use in a desired microorganism-immobilized carrier for water treatment, the amount of waste is reduced, and the flexible polyurethane foam can be efficiently produced.
From the viewpoint of ensuring the density, water-swellability, and homogeneity of the cell structure of the flexible polyurethane foam and at the same time, efficiently producing the foam, the height of the inner dimension of the foaming container is preferably 300mm to 1200mm, more preferably 400mm to 1000mm, and further preferably 500mm to 800 mm.
From the viewpoint of efficiently producing the flexible polyurethane foam, the volume of the mixing solution that can be contained inside the foaming container is preferably 0.03 to 0.8m3More preferably 0.1 to 0.6m3More preferably 0.2 to 0.5m3。
The method of pouring the mixed solution into the foaming vessel is not particularly limited, and for example, the mixed solution can be poured by mixing using a mixing head.
When the mixed solution is injected into the foaming container, the mixed solution is preferably injected along the wall surface of the foaming container. By thus injecting, the mixed solution being injected can be injected below the mixed solution already injected, and the bubbles formed by foaming included in the mixed solution already injected can be suppressed from being crushed by the mixed solution to be injected later. As a result, a flexible polyurethane foam having more excellent density, water-swelling property and homogeneity of the cell structure can be efficiently produced.
From the viewpoint of obtaining a flexible polyurethane foam excellent in density, water-swelling property and homogeneity of cell structure, the injection rate at the time of injecting the mixed solution into the foaming container is preferably 5 to 200kg/min, more preferably 50 to 150kg/min, and still more preferably 75 to 125 kg/min.
When the top surface of the foaming container is capped, the mixed solution may be injected into the foaming container with a part or all of the top surface capped, the cap may be added during the injection of the mixed solution, or the cap may be added before the injection of the mixed solution and the foaming of the mixed solution are completed.
< Flexible 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 foaming vessel and foaming the mixture, and the swelling density when swollen with water is 25 to 70kg/m3The average number of pores in the swollen state is 9 to 30 per 25mm, and the volume swelling ratio expressed by the ratio of the volume in the swollen state to the volume in the completely dry state is 110 to 1000%.
The swelling density of the flexible polyurethane foam when swollen with water is preferably 28 to 60kg/m as a flexible polyurethane foam suitable for a microorganism-immobilized carrier for water treatment3More preferably 28.5 to 50kg/m3。
The swelling density of the water swelling agent is less than 25kg/m3The flexible polyurethane foam of (2) has an excessively small amount of resin, is low in strength and is easily deformed, and the microorganism-immobilized carrier for water treatment produced by using the flexible polyurethane foam may cause problems such as clogging of a filter in a treatment tank and leakage of the deformed filter from the treatment tank. In addition, if the amount of resin is small, the resistance to physical abrasion is weak, and the volume reduction (consumption) becomes rapid.
On the other hand, the swelling density at the time of swelling with water exceeds 70kg/m3In the case of the above, the cost of raw materials is undesirably high.
The cell structure of the flexible polyurethane foam is preferably a communicated pore structure from the viewpoint of sufficiently penetrating microorganisms, oxygen necessary for respiration of microorganisms, nutrients necessary for activity and proliferation of microorganisms, and a substrate such as an object to be removed by microorganisms (organic matter (hydrocarbon), nitrogen compound, or phosphorus compound) into water to immobilize the microorganisms on the microorganism-immobilized carrier for water treatment. The average number of pores in swelling with water is 9 to 30 per 25mm, preferably 10 to 25 per 25mm, and more preferably 11 to 20 per 25 mm.
The "average number of pores upon swelling with water" means an average number of pores present on any 3 straight lines having a length of 25mm in the flexible polyurethane foam upon swelling with water. Specifically, the measurement can be performed by the method described in the examples described later.
The flexible polyurethane foam obtained by the present invention has a volume swell ratio of 110 to 1000%, preferably 120 to 800%, more preferably 140 to 500%, and still more preferably 150 to 300% due to swelling with water, from the viewpoint of excellent hydrophilicity and the like.
The flexible polyurethane foam having a volume swell ratio of less than 110% is not sufficient in affinity with water, and is hardly said to have excellent hydrophilicity.
On the other hand, the flexible polyurethane foam having a volume swell ratio of more than 1000% is not preferable because it is difficult to maintain durability required as a carrier for immobilizing microorganisms for water treatment.
The oven-dried density is preferably 48 to 130kg/m3More preferably 49 to 110kg/m3More preferably 50 to 90kg/m3。
The average pore diameter when swollen with water is preferably 0.20 to 2.00mm, more preferably 0.50 to 1.90mm, and still more preferably 0.70 to 1.80 mm. When the average pore diameter in the water swelling is within this range, the microorganisms, oxygen necessary for respiration of the microorganisms, nutrients necessary for activity and growth of the microorganisms, and substrates such as objects to be removed by the microorganisms (organic substances (hydrocarbons), nitrogen compounds, and phosphorus compounds) are allowed to sufficiently enter the water, and thus the microorganisms are easily immobilized.
The term "average pore diameter upon swelling with water" as used herein means that the major axis and the minor axis of one pore in the cross section of the flexible polyurethane foam upon swelling with water are measured and the average of the major axis and the minor axis is regarded as a perfect circle of the diameter, and similarly, the average of the diameters of 50 pores in total is regarded as a perfect circle.
In addition, from the viewpoint of maintaining a sufficient pore diameter and surface area, the width of the smallest portion of the skeleton portion of the soft polyurethane constituting the cell structure in the skeleton between adjacent pores when swelling with water is preferably 0.05 to 0.50mm, more preferably 0.07 to 0.40mm, and further preferably 0.10 to 0.30 mm.
In addition, as a cell structure suitable for immobilizing a large amount of microorganisms in water, it is preferable that the skeleton portion has a so-called wall structure in which the space between adjacent pores is partially in a film shape and is divided by wall surfaces to have a large surface area, as compared with a so-called rib structure composed of a thin rod-like skeleton.
From the viewpoint of efficiently producing the flexible polyurethane foam, the flexible polyurethane foam is preferably produced as a slab. The height of the flexible polyurethane foam produced in the form of a slab is preferably 300mm to 1200mm, more preferably 400mm to 1000mm, and still more preferably 500mm to 800mm, from the viewpoint of efficiently producing the flexible polyurethane foam.
From the viewpoint of efficiently producing the flexible polyurethane foam, the volume of the flexible polyurethane foam is preferably from 0.03 to 0.8m3More preferably 0.1 to 0.6m3More preferably 0.2 to 0.5m3。
The "volume of the flexible polyurethane foam" in the present invention also includes the cells of the flexible polyurethane foam, and means the volume determined based on the external dimensions of the flexible polyurethane foam.
The flexible polyurethane foam can be provided as a microorganism-immobilized carrier for water treatment, for example, by cutting a slab-shaped product into a desired size.
Examples
The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto.
[ preparation of raw Material ]
The raw material compounds used for the production of the flexible polyurethane foam are shown in detail below.
Urethane prepolymer (1): TDI modified EO-PO copolymers; EO/PO mass ratio: 55/45, number average molecular weight of EO-PO copolymer: 2700 (theoretical), NCO (isocyanate group) content: 4.5 mass%, viscosity (25 ℃): 8000mPa s
Urethane prepolymer (2): TDI modified EO-PO copolymers; EO/PO mass ratio: 50/50, number average molecular weight of EO-PO copolymer: 2500 (theoretical), NCO (isocyanate) content: 4.5 mass%, viscosity (25 ℃): 8000mPa s
Polyisocyanate compound (a): TDI; "CORONATE (registered trademark) T-80", manufactured by Tosoh corporation, 2,4-TDI/2,6-TDI by mass ratio: 80/20
Inorganic fillers: barium sulfate; made by Sakai chemical industry Co., Ltd., average particle diameter of 20 to 30 μm, specific gravity of 4.3
Curing agent/foaming agent: water (W)
Foam stabilizer: a nonionic surfactant; "NEWPOL (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>
400kg of TDI-modified EO-PO copolymer (urethane prepolymer (1)), 53.4kg of TDI (polyisocyanate compound (A)), and 50.0kg of barium sulfate (inorganic filler) were mixed with stirring to prepare an A1 solution.
Separately from the solution A1, 350kg of water and 7kg of a foam stabilizer were separately stirred and mixed to prepare a solution B1.
Next, A1 liquid (28 ℃ C.) and B1 liquid (14 ℃ C.) were each transferred from the tanks to the mixing head by a pump at a mixing mass ratio of 1.48(A1 liquid/B1 liquid). Discharging a raw material mixture of solution A1 and solution B1 from the mixing head to an internal dimension of 800mm in length, 800mm in width, 660mm in height, and a wall surface temperature TWAfter the completion of the injection into the foaming vessel at 25 ℃, the foaming vessel was closed and allowed to stand for 2 hours to prepare a slab-like flexible polyurethane foam.
A flexible polyurethane foam in the form of a slab was prepared 2 times by the above-mentioned method.
< example 2 and comparative examples 1 and 2>
To make the wall surface temperature TWFlexible polyurethane foams were prepared in the same manner as in example 1, except that the temperatures were as shown in Table 1, respectively. In addition, preparation was carried out 5 times in example 2Slab-shaped flexible polyurethane foam, 1 slab-shaped flexible polyurethane foam was prepared in comparative example 1, and 4 slab-shaped flexible polyurethane foams were prepared in comparative example 2.
< example 3>
400kg of TDI-modified EO-PO copolymer (urethane prepolymer (2)), 53.4kg of TDI (polyisocyanate compound (A)), and 50.0kg of barium sulfate (inorganic filler) were mixed with stirring to prepare A2 liquid.
Separately from the solution A2, 350kg of water, 29kg of a foam stabilizer and 6.7kg of a catalyst were stirred and mixed to prepare a solution B2.
Next, the wall temperature T was adjusted using A2 liquid (28 ℃ C.) and B2 liquid (14 ℃ C.)WFlexible polyurethane foams were prepared in the same manner as in example 1, except that the temperatures shown in Table 1 were used. Further, a flexible polyurethane foam was prepared in a slab form 2 times.
[ evaluation ]
< yield >
The slab-shaped flexible polyurethane foams obtained in the examples and comparative examples were sliced in the horizontal direction at a position 10mm below the topmost part and in the horizontal direction at a position 10mm above the lower surface.
Next, the sheet was sliced at intervals of 10mm in the horizontal direction to obtain a flexible polyurethane foam sheet having a thickness of 10 mm.
Each of the obtained flexible polyurethane foam sheets was pressed in the thickness direction to obtain a flexible polyurethane foam sheet having a length of 10 mm. times.a width of 10 mm. times.a thickness of 10mm (hereinafter, also referred to as "flexible polyurethane foam sheet"). After the punching, the flexible polyurethane foam sheet entirely existing inside a region X10 mm or more inside the side peripheral surface of the flexible polyurethane foam sheet is recovered, and the flexible polyurethane foam sheet entirely or partially existing outside the region X is removed and discarded.
The yield of the flexible polyurethane foams prepared in the examples and comparative examples was evaluated by the following method.
Specifically, the yield is determined as a value obtained by multiplying a value obtained by dividing the total weight of the recovered flexible polyurethane foam sheet by the weight of the mixed solution poured into the foaming vessel by 100.
The results of the yield evaluation are shown in table 1.
< physical Property >
For each of the flexible polyurethane foams prepared in the above examples and comparative examples, a flexible polyurethane foam sheet having a length of 10mm × a width of 10mm × a height of 10mm was prepared in the same manner as for the yield evaluation, and this was used as a sample.
Further, the following physical properties were evaluated for 2 kinds of samples of the slab-like flexible polyurethane foam obtained in examples, which were present in the central portion (a position 300mm or more from each wall surface of the foaming vessel) and in the vicinity of the wall surface of the foaming vessel (between 10 and 50mm from the wall surface of the foaming vessel).
Further, the flexible polyurethane foam produced at the 1 st stage was measured for physical properties.
(Absolute Dry Density)
The lengths of the respective sides of the sample in the dry state were measured with a vernier caliper, and the volume calculated as the product of the measured lengths of the respective sides was regarded as the volume V in the dry stated。
The mass M of the sample in the dry state determined as described abovedDivided by the volume V of the dry statedAnd the obtained value was taken as an absolute dry density.
(swelling Density)
The sample was immersed in water at 25 ℃ for 1 hour, and the length of each side of the sample was measured with a vernier caliper while the sample was immersed in water in a flat state. The volume calculated as the product of the measured side lengths was regarded as the volume V of the sample at the time of swelling with waterw。
Mass M of the absolutely dry statedDivided by the volume V at swelling of the waterwAnd the obtained value was taken as the swelling density.
(volume swelling ratio)
Volume V at swelling of the waterwVolume V relative to the absolute dry statedThe ratio was determined as the volume swelling ratio (%).
(average number of pores)
The center of the surface of the sample whose volume was measured when the sample swelled with water was colored with red ink. A ruler is placed on the colored portion and a picture is taken including the colored portion and the scale of the ruler. In the magnified image of the photographed photograph, the number of air holes observed on any parallel line with the straightedge was counted within the range of the interval position of 25mm of the scale at any position of the straightedge. The same measurement was carried out at 3 arbitrary positions, and the average value of the number of pores obtained by 3 measurements was defined as the average number of pores per 25mm when swelling with water.
[ Table 1]
TABLE 1
Figure BDA0003510691740000181
In examples 1 and 2, the wall temperature T was adjustedWGood yield can be obtained with the temperature set at 25 ℃ and 30 ℃. I.e. by setting the wall temperature TWIs 21-60 ℃, and can effectively prepare the flexible polyurethane foam. The polyurethane foam obtained has a predetermined swelling density during swelling with water, an average number of pores during swelling with water and a volume swelling ratio, and is excellent in homogeneity of physical properties with a small difference in physical property values between the central portion and the vicinity of the side surface.
On the other hand, in comparative examples 1 and 2, the wall surface temperature T of the foaming vessel was measuredWTherefore, the mixed solution near the wall surface is affected by this influence, and the produced flexible polyurethane foam has a mountain-like shape with a high height at the center and a low height at the periphery of the wall surface of the foaming solution. As a result, the yield is low, and the difference in physical property values is large in the center portion and the vicinity of the wall surface of the flexible polyurethane foam.
As described above, according to the production process of the present invention, a flexible polyurethane foam having a predetermined swollen density upon swelling with water, an average number of pores upon swelling with water and a volume swelling ratio, and being excellent in the uniformity of density, water-swellability and cell structure, can be efficiently produced by a batch process.

Claims (7)

1. A preparation method of soft polyurethane foam, which is a preparation method of soft polyurethane foam for a microorganism immobilization carrier for water treatment,
the production process comprises a step of injecting a mixed solution containing a urethane prepolymer and a polyisocyanate compound (a) into a foaming vessel and foaming the mixture to obtain a flexible polyurethane foam,
temperature T of a wall surface of the foaming container in contact with the mixed solutionWThe temperature is between 21 and 60 ℃,
the soft polyurethane foam has a swelling density of 25 to 70kg/m when swollen with water3The average number of pores in the swollen state is 9 to 30 per 25mm, and the volume swelling ratio expressed by the ratio of the volume in the swollen state to the volume in the completely dry state is 110 to 1000%.
2. The process for producing a flexible polyurethane foam according to claim 1, wherein a cap is placed on the upper surface of the foam container in the step of obtaining the flexible polyurethane foam.
3. The process for producing a flexible polyurethane foam according to claim 1 or 2, wherein the height of the flexible polyurethane foam is from 300mm to 1200 mm.
4. The process for producing a flexible polyurethane foam according to any one of claims 1 to 3, wherein the volume of the flexible polyurethane foam is from 0.03 to 0.8m3。
5. 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.
6. The process for producing a flexible polyurethane foam according to any one of claims 1 to 5, wherein the mixed solution is injected along a wall surface of a foaming vessel.
7. The soft poly of any one of claims 1-6Process for the production of a polyurethane foam, wherein the temperature T of the mixed solutionSTemperature T of the wall surfaceWThe absolute value of the difference is 0 to 40 ℃.
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