JP6364769B2 - Resin composition, microorganism-immobilized carrier and purification method - Google Patents

Description

  The present invention relates to a resin composition obtained by heating a mixture containing a polyolefin resin (A), a maleic anhydride copolymer (B), and a polyethyleneimine (C), and purifies wastewater. The present invention relates to a microorganism-immobilized carrier that is used by immobilizing microorganisms on the surface when performing.

  There are methods for biochemical treatment of domestic wastewater and factory wastewater using microorganisms, aerobic treatment performed by aeration of air and oxygen in large quantities, and anaerobic treatment performed in an anaerobic atmosphere without aeration of air etc. Broadly divided into sex processing. Anaerobic treatment has advantages such as less generation of surplus sludge than aerobic treatment, biogas such as methane can be obtained by treatment, and oxygen supply is unnecessary, so less power is required than aerobic treatment. And is expected to spread further in the future.

  In addition, as anaerobic treatment methods, an anaerobic microorganism is retained, an upflow anaerobic sludge bed method (UASB) using granules, an expanded sludge bed method (EGSB), an anaerobic membrane or carrier. There are anaerobic fixed bed method, anaerobic fluidized bed method and the like as a method using a biofilm on which anaerobic microorganisms are immobilized.

  Among these, the microorganism immobilization method that purifies the wastewater by immobilizing microorganisms that purify the wastewater on the surface of the inorganic or organic matter can increase the concentration of microorganisms in the wastewater. Therefore, there is an advantage that the purification efficiency of the wastewater in the wastewater is improved, the wastewater treatment can be performed even if the organic matter concentration in the wastewater is high, and the septic tank can be downsized.

In addition, the fluidized bed method in which the microorganism-immobilized carrier is purified by floating and flowing in the wastewater not only increases the purification efficiency, but also because the gap between the carriers is constantly changing, it is difficult to block and can be operated stably for a long time. Has attracted attention in recent years. Specifically, as a microorganism-immobilized carrier for an aerobic fluidized bed, a method using a polyurethane or polyolefin foam (Patent Documents 1 and 2) or a gel obtained by crosslinking PVA or PEG is generally used. (Patent Documents 3 and 4)
Examples of the anaerobic fluidized bed include those obtained by molding high density polyethylene (HDPE) and those obtained by subjecting the foam surface to a hydrophilic treatment (Non-patent Documents 1 and 5).

  In general, it is known that anaerobic microorganisms have a slower growth rate than aerobic microorganisms. Accordingly, there is a problem that it takes more time to fix anaerobic microorganisms on the surface of the carrier and to make the microorganism-immobilized carrier exhibit performance as an anaerobic fluidized bed than when an aerobic microorganism is used.

  In addition, foam-shaped microorganism-immobilized carriers made of polyurethane, polyolefin, etc. have the advantage that microorganisms are fixed inside the foam and the surface area is increased, so that the growth area of microorganisms is expanded. If this is not possible, there has been a problem that the function of the microorganisms to purify the wastewater cannot be fully exhibited.

  As a material for the microorganism-immobilized carrier, polyolefin resins such as polyethylene and polypropylene are considered to be used as a microorganism-immobilized carrier because of their excellent mechanical strength and high durability. However, since the polyolefin resin generally has little polarity, it is difficult for microorganisms to be immobilized on the surface, and when used as a microorganism immobilization carrier, there has been a problem in the method for immobilizing microorganisms.

  Therefore, as a conventional method for solving the above-mentioned problem, in order to improve the fixability of microorganisms on the surface of the microorganism-immobilized carrier, a hydrophilic treatment such as a surfactant (Patent Document 1), or a foam surface such as cellulose is used. A device such as a crosslinking treatment of a cationic polymer with an epoxy compound or the like (Patent Document 5) has been made. However, even when the surface of the polyolefin-based resin-immobilized carrier is subjected to hydrophilic treatment, the fixability of the microorganism is not greatly improved. In addition, when a crosslinking treatment is performed with an epoxy compound or the like, a waste liquid treatment is required. There were problems such as an increase in cost.

JP 2003-2111175 A JP-A-10-257858 JP 2001-089574 A JP 2004-275113 A JP-A-8-256773

Water Science & Technology, Vol. 56, no. 2, P1-7 (2007)

  An object of the present invention is to provide a novel resin composition and a microorganism-immobilized carrier used for purifying anaerobic wastewater, which has high durability and can easily fix microorganisms, using the above-described composition. It is in providing the purification method of the waste_water | drain using the.

  As a result of intensive studies on the above problems, a novel composition obtained by heating a mixture containing a polyolefin resin (A), a maleic anhydride copolymer (B), and a polyethyleneimine (C) is provided. It became possible. In addition, the composition can be used as a microorganism-immobilized carrier. Furthermore, the surface of the resin composition has a zeta potential having a specific value, whereby a microorganism-immobilized carrier that is excellent in immobilizing microorganisms has been developed, and the present invention has been achieved.

That is, the present invention is as follows.
(1) Polyethyleneimine (C) is 0.01 to 99 parts by weight with respect to 100 parts by weight of a resin mixture containing 1 to 99 parts by weight of polyolefin resin (A) and 99 to 1 part by weight of maleic anhydride copolymer (B). A resin composition obtained by heating a mixture containing 10 parts by weight at 120 to 250 ° C.
(2) The resin composition according to (1), further containing a filler (D).
(3) The resin composition according to (1) or (2), wherein the surface zeta potential is −15 to +15 mV.
(4) A microorganism-immobilized carrier comprising the resin composition according to any one of (1) to (3).
(5) The microorganism-immobilized carrier according to (4), which is a microorganism-immobilized carrier for anaerobic fluidized beds for wastewater purification.
(6) A method for purifying wastewater, wherein the microorganism-immobilized carrier according to (4) or (5) is brought into contact with wastewater.

Hereinafter, the present invention will be described in detail.
Examples of the polyolefin resin (A) include polyethylene resin, polypropylene resin, and polybutene.

  Examples of the polyethylene resin include low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, ethylene-α-olefin copolymer having ethylene as a main component, ethylene-vinyl acetate copolymer, Examples thereof include an ethylene-ethyl acrylate copolymer and an ethylene-methacrylate copolymer. Examples of the α-olefin constituting the ethylene-α-olefin copolymer include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene and the like. Is mentioned.

  Examples of the polypropylene resin include a polypropylene homopolymer, a propylene-α-olefin copolymer having propylene as a main component, and an ethylene-propylene-butene terpolymer having propylene as a main component. Examples of the α-olefin constituting the propylene-α-olefin copolymer include ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene and the like. Is mentioned.

  The polyolefin resin (A) of the present invention is preferably a polyethylene resin or a polypropylene resin, and further a low density polyethylene, a linear low density polyethylene, a high density polyethylene, or an ethylene-vinyl acetate copolymer. It is preferable in terms of mechanical properties and availability. These may be used alone or in combination of two or more.

  The melt flow rate (MFR) of the polyolefin resin (A) is not particularly limited, but when used as a microorganism-immobilized carrier, the preferred MFR differs depending on the method of molding the carrier. The MFR of the system resin (A) is preferably 1 to 100 g / min, and in the case of extrusion molding or the like, it is 0.01 to 20 g / min, and more preferably 0.1 to 10 g / min. If it exists in this range, a moldability will become favorable in each shaping | molding method.

  The polyolefin resin (A) may be a recycled resin as long as it does not impair the effects of the present invention, and is desirable from the viewpoint of cost reduction and waste reduction.

  In the present invention, the resin composition is cationized by containing maleic anhydride copolymer (B) and polyethyleneimine (C). Since polyethyleneimine (C) has a molecular structure with particularly high polarity, when polyethyleneimine (C) is generally added to polyolefin resin (A) having almost no polarity, the compatibility is poor, so polyethyleneimine (C) Tends to elute from the surface of the mixture, and the cationization treatment cannot be continued for a long time. The composition of the present invention is obtained by heating a mixture containing a maleic anhydride copolymer (B), polyethyleneimine (C), and a polyolefin resin (A). It is increasing.

  The maleic anhydride copolymer (B) used for such purpose may be any resin as long as it is a resin copolymerized with maleic anhydride, but the polyolefin maleic anhydride copolymer is a polyolefin resin. The compatibility with (A) is high, and both formability and durability can be increased, which is preferable.

Examples of the polyolefin-based maleic anhydride copolymer include ethylene-α, β-unsaturated carboxylic acid alkyl ester-maleic anhydride copolymer, maleic anhydride graft-modified ethylene-α-olefin copolymer, and maleic anhydride. Examples thereof include a grafted polypropylene copolymer. Examples of the ethylene-α, β-unsaturated carboxylic acid alkyl ester-maleic anhydride copolymer include, for example, ethylene-methacrylate-maleic anhydride copolymer, ethylene-ethacrylate-maleic anhydride copolymer, and ethylene-butyl acrylate. -Maleic anhydride copolymer, ethylene-vinyl acetate-maleic anhydride copolymer, etc., and maleic anhydride graft-modified ethylene-α-olefin copolymer, for example, maleic anhydride graft low density Examples include polyethylene, maleic anhydride graft-modified linear low density polyethylene, maleic anhydride grafted high density polyethylene, maleic anhydride grafted ethylene-vinyl acetate copolymer, maleic anhydride graft modified ethylene-propylene rubber, and the like. The maleic anhydride graft-modified ethylene-α-olefin copolymer can be produced, for example, by allowing the ethylene-α-olefin copolymer, peroxide, and maleic anhydride to coexist and allowing the graft reaction to proceed. Specific examples of these maleic anhydride copolymers (B) include OREVAC G, OREVAC T, BONDINE (trade name, manufactured by Arkema), Umex (trade name, manufactured by Sanyo Kasei) and the like.

  The content of maleic anhydride contained in the maleic anhydride copolymer (B) is preferably 0.05 to 10% by mass, and more preferably 0.1 to 5% by mass. If the content of maleic anhydride is small, as will be described later, the number of reactive sites with polyethyleneimine decreases, and it is necessary to increase the amount of maleic anhydride copolymer (B) in order to react with polyethyleneimine (C). As a result, it tends to be disadvantageous in cost.

  In the present invention, the ratio of the polyolefin resin (A) and the maleic anhydride copolymer (B) is 1 for a total of 100 weights of the polyolefin resin (A) / maleic anhydride copolymer (B). / 99 to 99/1, preferably 90/10 to 99/1. Even if a large amount of the maleic anhydride copolymer (B) is used, there is no effect on the immobilization of microorganisms. When the maleic anhydride copolymer (B) is below the above range, the maleic acid group that reacts with the polyethyleneimine (C) decreases as described later, and the polyethyleneimine (C) is likely to elute from the resin composition. As a result, it is not preferable because the effect of improving the microorganism fixing property is hardly sustained.

  Polyethyleneimine (C) is a polymer obtained by polymerizing ethyleneimine, and is a cationic water-soluble polymer containing a primary to tertiary amine structure in the molecule. The molecular structure of the polyethyleneimine (C) is not particularly limited, and examples thereof include branched and linear molecular structures. In order to have a molecular spread in water, a branched polyethyleneimine is used. Particularly preferred. The molecular weight of the polyethyleneimine (C) is preferably 300 to 2,000,000, more preferably 300 to 30,000, and particularly preferably 500 to 5,000. If the molecular weight is too large, the viscosity will increase, and problems such as reduced workability may occur during processing.

  Further, the polyethyleneimine (C) may be in the form of an aqueous solution or not dissolved in water. However, in the case of non-foaming in the molding described later, since the water of the solvent is easy to serve as a foaming agent, the polyethyleneimine (C) should be one that is not dissolved in water. Is particularly preferred.

  Specific examples of such polyethyleneimine (C) include Epomin SP-006, Epomin SP-012, Epomin SP-018 (trade name, manufactured by Nippon Shokubai Co., Ltd.), Lupasol FG (trade name, manufactured by BASF) and the like. be able to.

  Furthermore, a molecular structure in which a functional group is previously reacted with a part of the amino group of the molecular structure of polyethyleneimine (C) may be used. Examples of such functional groups include isocyanate compounds, propylene oxide, and the like, for example, Epomin PR-20 (trade name, manufactured by Nippon Shokubai), Epomine PR-061 (trade name, manufactured by Nippon Shokubai), and the like. Can do.

  In the present invention, the addition amount of polyethyleneimine (C) is 0.01 to 10 parts by weight with respect to a total of 100 parts by weight of polyolefin resin (A) and maleic anhydride copolymer (B), 0.05-5 weight part is preferable and 0.1-3 weight part is especially preferable. When the amount added is less than the above range, the amount of amino groups of polyethyleneimine (C) decreases, and the microbial carrier is not sufficiently cationized. When the amount added exceeds this range, the microbial immobilized carrier is too cationized. This is not preferred because it adversely affects the microorganisms to be fixed, impairs processability, and lowers economic efficiency.

  Further, a molar amount Mc obtained by dividing the amount of polyethyleneimine (C) added in the composition by the average molecular weight of polyethyleneimine (C), and a carboxylic anhydride based on the maleic anhydride copolymer (B) contained in the composition When the ratio of the molar amount Mb of the group is [Mc / Mb], the range of [Mc / Mb] is preferably 0.05 to 5 times, particularly preferably 0.1 to 2 times. If it is smaller than this range, the effect of cationization is not sufficient. If it is too large, the amount of polyethyleneimine (C) that does not react with the maleic anhydride copolymer (B) increases as described later. As a result, polyethyleneimine (C ) Is likely to elute.

  The resin composition of the present invention comprises 1 to 99 parts by weight of a polyolefin resin (A) and 100 parts by weight of a resin mixture containing 99 to 1 part by weight of a maleic anhydride copolymer (B). It can be obtained by heating a mixture containing 0.01 to 10 parts by weight of C) at 120 to 250 ° C, preferably 150 to 180 ° C.

  By heating at this temperature, it is considered that at least a part of the polyethyleneimine (C) of the resin mixture reacts with the maleic anhydride copolymer (B) to form a covalent bond and / or an ionic bond. As a result, the elution of polyethyleneimine (C) from the resin composition can be reduced, and the effect of imparting cationicity can be sustained, so that the effect of immobilizing microorganisms can be maintained.

  The heating described above may be performed also for kneading and / or molding of the resin mixture, or may be performed separately.

  In general, the zeta potential on the surface of the polyolefin resin (A) is in the range of −50 to −20 mV, and the zeta potential is too low, so that immobilization of microorganisms is poor. In the resin composition of the present invention, the surface can be cationized by the copolymer of maleic anhydride copolymer (B) and polyethyleneimine (C) to increase the zeta potential. The zeta potential on the surface of the resin composition of the present invention is desirably adjusted to a range of −15 to +15 mV, more preferably −10 to +10 mV, when used as a microorganism-immobilized carrier. If it is smaller than this range, the effect of the cationization treatment is small, and the initial immobilization of microorganisms is not improved, and if it is larger than this range, the growth of the immobilized microorganisms tends to decrease.

  The specific gravity of the resin composition of the present invention is not particularly limited, but when it is used as a microorganism-immobilizing support, if it floats on the water surface, contact with wastewater decreases when used for wastewater purification, and purification efficiency decreases. Therefore, the specific gravity is preferably larger than that of water. However, when the microorganism-immobilized carrier of the present invention is used for a fluidized bed, the specific gravity of the microorganism-immobilized carrier is set within the range of 0.95 to 1.20 in order to flow and circulate the carrier by stirring with less power. Preferably, the range of 0.97 to 1.15 is more preferable, and 1.00 to 1.10 is particularly preferable.

  The specific gravity of the polyolefin resin (A) is generally in the range of 0.86 to 0.97 and is lighter than the waste water. Therefore, the filler for the purpose of adjusting the specific gravity of the resin composition of the present invention to the above range. It is preferable to add an appropriate amount of (D). Examples of the filler (D) include calcium carbonate, talc, barium sulfate, clay, mica, glass particles, and glass fiber, and one or more of these may be used. Among these, calcium carbonate and talc are preferable because they are easily available at low cost.

  The content of the filler (D) is preferably adjusted so that the specific gravity of the resin composition of the present invention is in the above range. Specifically, in the case of calcium carbonate having a specific gravity of 2.7, although it depends on the specific gravity of the resin composition of the present invention, it is preferably 0 to 75 parts by weight, more preferably 5 to 50 parts per 100 parts by weight of the resin composition. What is necessary is just to contain a weight part.

  As long as the effects of the present invention are not impaired, other resins, fillers, additives, processing aids, hydrophilizing agents, coloring agents, and the like may be added, but they are used as microbial immobilization carriers for wastewater purification. In some cases, it is desirable to minimize the amount added to the environment and organisms as little as possible.

  Examples of such additives include phenol-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, lactone-based antioxidants, light-resistant stabilizers, and antistatic agents. Examples of processing aids include waxes, metal soaps, fatty acids such as stearic acid, lubricants such as fluorine compounds, and the like. Examples of the hydrophilizing agent include amphoteric surfactants, ionic surfactants, and nonionic surfactants.

  For raw materials to be used, especially powders and liquids, a master batch (MB) that is kneaded into a resin in advance may be used. There are no particular limitations on the raw material used for the master batch, and a part of powder or liquid raw material may be used, or all powder or liquid raw material may be used. A plurality of master batches may be mixed and used. The resin used for the masterbatch is not particularly limited as long as the effects of the present invention are not impaired, but a polyolefin resin (A) and / or a maleic anhydride copolymer (B) may be used. Although there is no restriction | limiting in particular in the density | concentration of the material in a masterbatch, A raw material should just disperse | distribute uniformly at the time of shaping | molding etc. In the case of a masterbatch of a filler (D), it is 10-80 mass%, for example, Preferably 25- 80% by mass. Outside this range, the economic superiority, productivity, dispersibility, and the like of using the master batch are likely to deteriorate, which is not preferable.

  The production method of the masterbatch may be an ordinary method for producing a masterbatch for polyolefin, and examples thereof include a Banbury mixer, a pressure kneader, a twin screw extruder, a kneader, and a kneader ruder.

  As a method for kneading the material used for the resin composition of the present invention, a normal kneader for producing a composite material (compound) of an olefin resin can be used. Examples thereof include continuous production machines such as a screw extruder, a kneader, a single screw extruder, and a kneader ruder, and batch production machines such as a Banbury mixer, a pressure kneader, and a roll. Absent. When the kneaded product is formed into a pellet shape, a pelletizer or the like used for normal compound processing may be used.

  Furthermore, as a method of supplying the material to the kneader, a method of supplying all the materials at once, a method of supplying the material in a plurality of parts, a method of supplying by removing a part of the materials (in this case, the remaining material at the time of molding A method with high productivity of the resin mixture may be selected, such as adding a material). When the polyethyleneimine (C) is in a liquid state, when it is kneaded with a twin screw extruder or a kneader, it may be supplied separately from other raw materials. For example, there are a method of directly adding to a hopper of an extruder using a pump, a method of supplying in the middle of an extruder cylinder, and the like.

  The material kneading conditions may be the same as the method for kneading ordinary resin composite materials. However, when polyethyleneimine (C) is added, polyethyleneimine (C) is susceptible to thermal degradation. The kneading temperature is 250 ° C. or lower, preferably 200 ° C. or lower, more preferably 180 ° C. or lower. The lower temperature range is the melting point or softening point of the resin used.

The resin composition of the present invention can be used as a carrier for immobilizing microorganisms.
In the present invention, the microorganism refers to a minute organism whose individual presence cannot be identified with the human eye, and is not particularly limited. In addition, prokaryotes such as bacteria and actinomycetes, eukaryotes such as yeast and fungi, lower algae, viruses, and the like are included. Cells include hybridomas, cultured cells derived from animals and plants, and the like.

  The microorganism-immobilized carrier of the present invention is a carrier for immobilizing microorganisms, which is a carrier for immobilizing microorganisms.

  An anaerobic microorganism means a microorganism that can survive in the absence or presence of air completely or partially.

  Examples of the shape of the microorganism-immobilized carrier of the present invention include a hollow tubular shape, a sphere, a columnar shape, a cube, a rectangular parallelepiped, a sheet shape, and the like. The hollow tubular shape includes a circular cross section, an elliptical shape, and a triangular shape. Further, it may be a tubular shape of any shape such as a quadrilateral or more polygonal shape or an irregular cross section. Furthermore, the shape of the carrier may be a combination of these shapes, for example, the shape as shown in FIG. Since the amount of microorganisms immobilized increases as the surface area of the microorganism-immobilized carrier increases, a hollow tubular shape having a large surface area per carrier unit weight is particularly preferred.

  A hollow tubular shape in which one end face is closed, such as a cup shape, is not preferable because the gas generated during drainage purification stays and the buoyancy tends to change. A tubular shape is preferred.

  The size of the microorganism-immobilized carrier of the present invention is not particularly limited as long as the effects of the present invention are not impaired. However, in the case of a hollow tubular shape, a spherical shape, etc., the outer diameter and length are preferably 3 to 30 mm, particularly 3 10 mm is preferred. If the size of the carrier is too small from this range, the hollow part will be small and the gas attached to the hollow part of the carrier will be difficult to be released, so the buoyancy will change easily. Therefore, since the fixed amount of microorganisms may decrease, it is not preferable. Moreover, as thickness of a hollow tubular shape, 0.05-2 mm is preferable, 0.1-1 mm is still more preferable, 0.15-0.6 mm is especially preferable. If the thickness of the hollow tubular carrier is larger than this range, the surface area per unit weight of the material is reduced and the material cost is likely to increase, and if it is thinner than this range, not only the strength of the carrier is decreased, This is because the moldability is lowered and the production cost of the carrier is likely to increase.

  The foam-shaped microorganism-immobilized carrier used in the aerobic wastewater purification method has the advantage that microorganisms are immobilized inside the foam, but the wastewater cannot be sufficiently diffused into the foam, and in the case of anaerobic treatment, the foam The growth of internal microorganisms may be slow, and purification efficiency may not be sufficient.

  The microorganism-immobilized carrier of the present invention is preferably a non-foamed material because microorganisms can be effectively immobilized by the effect of modifying the carrier surface due to the inclusion of the carboxylic anhydride copolymer (B) and the polyethyleneimine (C), A particularly preferable shape is a non-foamed cylindrical hollow tubular shape.

  As a method for forming the microorganism-immobilized carrier, injection molding, extrusion molding, press molding, or the like may be used as it is, and further, the secondary processing such as cutting, crushing, fusing, and bonding the carrier into a predetermined size. You may use it. In particular, the productivity is high, and extrusion molding with continuous molding is preferred, and hollow tubular extrusion molding is particularly preferred.

  The extruder used for extrusion molding is not particularly limited, but a normal single-screw extruder, twin-screw extruder, etc. may be used, and in order to obtain a non-foamed molded product, the cylinder of the extruder is deaerated. What has an apparatus (vent) is preferable. This is because polyethyleneimine (C), maleic anhydride copolymer (B), and, in some cases, a filler (D), which are highly hygroscopic, are used as the material to be used. This is because the portion is degassed during extrusion. It is also effective to dry the material well before molding for the purpose of preventing foaming. In this case, a normal drying method such as vacuum drying, dehumidifying drying, hot air drying or the like can be selected.

  Further, there is no restriction on the material kneading at the time of molding the carrier, but for example, it may be molded using a same-direction twin screw extruder, a single screw extruder, or the like. Further, in this case, like the kneading method described above, the material supply method is not limited by any method, but in order to improve the material supply and dispersibility, a filler, polyethyleneimine or the like is used as a part of the material. Is preferably supplied in a masterbatch.

  In order to increase the surface area of the carrier, it is particularly preferable to provide plate-like protrusions and fine irregularities on the surface in order not only to increase the fixed amount of microorganisms but also to prevent the fixed microorganisms from falling off.

  As a method for forming fine irregularities on the surface of the carrier, for example, a method of forming irregularities on an extrusion mold, a method of forming by generating a melt fracture phenomenon of a resin, and forming irregularities by adding a filler And the like.

  In order to form fine irregularities on the surface of the carrier, for example, in the case of extrusion molding, it can be formed by forming grooves at regular intervals on the outer surface or inner surface of the extrusion mold. More specifically, using a mold obtained by cutting a plurality of grooves having a width of 0.5 to 2 mm and a depth of 0.5 to 5 mm at regular intervals along the outer periphery of the extrusion mold, A carrier on which a plurality of plates are formed can be manufactured.

  Further, as a method of making the support surface uneven by utilizing the melt fracture phenomenon of the resin, it is preferable to apply a phenomenon at the time of molding of the resin such as shark skin, melt fracture, gloss melt fracture or the like in extrusion molding or the like. In order to use such a phenomenon, for example, if a polyolefin resin (A) is a resin having a narrow molecular weight distribution such as linear low-density polyethylene or high-density polyethylene, shark skin is likely to occur, which is preferable. .

  The depth of the irregularities on the surface of the carrier is preferably 0.01 to 2 mm. If the unevenness is larger than this, the effect of preventing the immobilized microorganisms from peeling off becomes small.

  To form a hollow tubular body, for example, a hollow tubular die (die) is attached to the tip of the extruder, such as a hose, pipe, or straw, and the resin is extruded at a temperature equal to or higher than the melting point of the resin. Can be molded. The extruded product is cooled in a cooling water tank or the like, and cut into a predetermined size with an appropriate cutting machine (for example, a pelletizer for pellet cutting) to form a carrier. Further, immediately after being extruded from the mold, for example, it may be produced by continuously cutting and cooling with a cutting machine such as a continuous rotary cutter in an atmosphere sprayed with cooling water.

  As the extrusion temperature, it is sufficient that the microorganism-immobilized carrier can be molded. However, if the molding temperature is high, polyethyleneimine is likely to be deteriorated by heat. Conversely, if the molding temperature is too low, an extrusion load during molding is likely to be applied. Therefore, the range of 120 to 250 ° C. is preferable, and the range of 150 to 180 ° C. is particularly preferable.

  There is no restriction | limiting in particular as a usage method of the microorganisms fixed support | carrier of this invention, What is necessary is just to fix microorganisms suitably and to use. For example, when used for purification of waste water, microorganisms used for purification of waste water are immobilized on the surface of the carrier. Furthermore, an appropriate amount of the microorganism-immobilized carrier may be used in the wastewater depending on the properties and temperature of the wastewater to be purified, the structure of the septic tank, and the like.

  As a purification method of waste water using the microorganism-immobilized carrier of the present invention, any method of a fixed bed method and a fluidized bed method may be used, but since the clogging of the gap between the microorganism-immobilized carriers is small, it is used for the fluidized bed method. Is preferred. Examples of the method for flowing the microorganism-immobilized carrier of the present invention in the wastewater by the fluidized bed method include, for example, a method of stirring with a stirring blade attached to the tip of a motor, and stirring by sucking and discharging a part of the wastewater with a pump. The method of stirring the drainage by aeration of an appropriate gas, the method of stirring naturally by providing a baffle plate in the drainage tank and flowing the drainage between them, etc. There is no particular limitation in any direction. If the agitation is too weak, the microorganism-immobilized carrier does not flow in the waste water, and the contact between the waste water and the microorganism-immobilized carrier is reduced, resulting in a decrease in purification efficiency. Since the microorganisms are peeled off, it is desirable to stir at an appropriate strength (speed). Further, it is desirable to provide a partition having a mesh smaller than the outer diameter and length of the carrier at the outlet of the purified waste water in order to prevent the microorganism-immobilized carrier of the present invention from flowing out.

  As a method for immobilizing microorganisms on the microorganism-immobilized carrier of the present invention, the carrier may be directly injected into the waste water and the microorganisms may be naturally immobilized, but the present invention is applied to a water tank in which microorganisms have been grown to a high concentration in advance. A microorganism-immobilized carrier may be inserted to fix microorganisms, and then removed and put into a wastewater septic tank. The method of injecting the microorganism-immobilized carrier into the wastewater after immobilizing microorganisms in this way is preferable because it can shorten the time until normal purification, and anaerobic microorganisms are particularly slow growing, especially in the case of anaerobic treatment preferable. Alternatively, microorganisms may be fixed in advance on some of the microorganism-immobilized carriers and then charged into the septic tank.

  Since the microorganism-immobilized carrier of the present invention is a chemically stable substance containing the resin composition of the present invention and has good long-term storage stability, there is no particular limitation on the storage method. From the viewpoint of transportability, storage in a dry state is preferable. Further, since a polyolefin-based material is used, when the carrier is exchanged, the used carrier can be subjected to material recycling, thermal recycling, and the like.

  The resin composition of the present invention can be used as a microorganism-immobilizing carrier, contains polyolefin, a maleic anhydride copolymer and polyethyleneimine, and can efficiently immobilize microorganisms by applying heat. It became. As a result, the microorganism-immobilized carrier of the present invention is excellent in abrasion resistance and high mechanical strength because the microorganisms are fixed for a long time and uses a polyolefin resin. It is useful as a carrier for immobilizing microorganisms in a fluidized bed. Furthermore, by making the shape of the microorganism-immobilized carrier into a non-foamed hollow shape, it is possible to obtain a microorganism-immobilized carrier in which the microorganism fixation and drainage purification efficiency, the fluidity of the carrier in the fluidized bed method, etc. are ensured, Since the portion of the air stayed by aeration is small and the change in buoyancy is small, it is useful as an aerobic fluidized bed immobilization carrier.

It is a figure which shows an example of the shape of the microorganisms fixed support | carrier of this invention. 6 is a view showing a microorganism-immobilized carrier of Example 4. FIG.

  The present invention will be described in more detail based on the following examples. However, these are examples to help understanding of the present invention, and the present invention is not limited to these examples. Commercially available products were used unless otherwise specified.

(Reagents, etc.)
Polyolefin resin (A)
a1) Nipolon L F15R (trade name, manufactured by Tosoh Corporation) linear low density polyethylene, density 925 kg / m ³ , MFR 0.8 g / 10 min
a2) Nipolon Hard 8022 (trade name, manufactured by Tosoh Corporation) High-density polyethylene, density 958 kg / m ³ , MFR 0.35 g / 10 min
a3) Petrocene 173R (trade name, manufactured by Tosoh Corporation) low density polyethylene, density 924 kg / m ³ , MFR 0.3 g / 10 min
a4) Ultrasen 627 (trade name, manufactured by Tosoh Corporation) ethylene-vinyl acetate copolymer, density 941 kg / m ³ , MFR 0.8 g / 10 min,
a5) Novatec BC8 (trade name, manufactured by Nippon Polypro), polypropylene, density 900 kg /
m ³ , MFR 1.8 g / 10 min
Maleic anhydride copolymer (B)
b1) Bondine AX8390 (trade name, manufactured by Arkema), ethylene-ethacrylate-maleic anhydride copolymer, maleic anhydride amount 1.3%
b2) OREVAC18360 (trade name, manufactured by Arkema) maleic anhydride graft LLD
PE, density 914 kg / m ³
Polyethyleneimine (C)
c1) Epomin SP018 (trade name, manufactured by Nippon Shokubai) Branched polyethyleneimine, average molecular weight of about 1800
c2) Epomin SP006 (trade name, manufactured by Nippon Shokubai) Branched polyethyleneimine, average molecular weight of about 600
Filler (D)
d1) BF300 (trade name, manufactured by Bihoku Powder Chemical Co., Ltd.) calcium carbonate, average particle size 8 μm
Antioxidant e1) Adeka AO-60 (trade name, manufactured by ADEKA) Phenolic antioxidant (Production of calcium carbonate MB)
Calcium carbonate (d1) 50% by mass and Petrocene 173R (a3) 50% by mass are mixed and extruded and kneaded in the same direction twin screw extruder (TEM-50B manufactured by Toshiba Machine), and pellet-shaped master batch (d1MB) Manufactured.

(Measurement of zeta potential)
A sheet having a thickness of 0.5 mm was prepared by extrusion molding, and the zeta potential was measured using ELZS-1000ZS manufactured by Otsuka Electronics in an aqueous solution of NaCl 0.01M.

(Evaluation of stability of zeta potential)
The sheet on which the zeta potential was measured was placed in 1 liter of water, and the change in the zeta potential was evaluated after leaving for one week while changing the water every day.

(Evaluation of liquidity)
In a container having a capacity of about 1 L, 0.5 L of water and about 10 g of the carrier were put, stirred at 300 rpm, the submergence and fluidity of the carrier were observed, and evaluated in the following three stages. The state that can be used as a carrier is a double circle that can flow in water and a circle.

Evaluation Double circle (good): The carrier is submerged and fluidized in the whole water. ○ (Normal): The carrier is almost submerged, but fluidized above the water. Flowable as a whole)
X (impossible): The carrier is hardly submerged and floats on the water surface (there are many carriers that are not submerged even if the agitation is increased).
(Abrasion resistance evaluation)
A water-resistant sandpaper (No. 100) is affixed to the inside of a glass container with a capacity of about 1 L, about 20 g of carrier and 0.5 L of water are added and stirred at 500 rpm for 4 days, and the mass change before and after the test (after drying) ).
Mass change rate (%) = [(dry mass before test−dry mass after test) / (dry mass before test)] × 100
A mass change rate of less than 5% was defined as a range with good wear resistance, and a mass change rate of 5% or more was defined as a range with poor wear resistance.
As a reference example, as a result of evaluating the abrasion resistance of a polyurethane foam (an approximate cube having one side of about 5 mm), the weight change was 25%, and the abrasion resistance was not so good.

(Judgment method of comprehensive evaluation)
The overall evaluation was evaluated as follows, with the zeta potential and the evaluation of stability, fluidity, and durability of the zeta potential being all good.

Double circle (good): Good in all items Circle (normal): Some evaluations have ○ (normal), but can be used as a microorganism-immobilized carrier × (No): Some items However, there is an evaluation of x (impossible) Example 1
Polyethyleneimine (c1) 0.3 parts by weight and filler (d1) 25 parts by weight with respect to a total of 100 parts by weight of polyolefin resin (a1) 95 parts by weight and maleic anhydride copolymer (b1) 5 parts by weight Were mixed and kneaded at a resin temperature of 165 ° C. using a same-direction twin screw extruder to obtain pellets. This pellet was extruded at 160 ° C. with a lab plast mill to obtain a sheet having a thickness of 0.5 mm.

  After adjusting the state with a NaCl 0.01M aqueous solution, the zeta potential was measured to be -2 mV. When the stability of the zeta potential was evaluated, it was stable with almost no change of -3 mV.

  Extruded at 145 ° C using a tube die with a lab plast mill single-screw extruder, cooled in a cooling water tank, and then cut with a continuous rotary cutter, resulting in an outer diameter of about 4 mm, a length of about 4 mm, and thickness A roughly cylindrical microorganism-immobilized carrier having a thickness of about 0.2 mm was obtained. The obtained carrier was not foamed, and fine irregularities having a depth of about 0.05 to 0.1 mm due to melt fracture were formed on the cylindrical side surface. When the wear resistance of the obtained carrier was evaluated, the amount of wear was 0.5% or less, which was a good result.

Example 2
2 parts by weight of polyethyleneimine (c1) is mixed with 100 parts by weight of the total of 95 parts by weight of the polyolefin resin (a1) and 5 parts by weight of the maleic anhydride copolymer (b1). And kneaded at a resin temperature of 165 ° C. to obtain pellets. A mixture of this pellet and calcium carbonate MB (d1MB) at a ratio of 102/60 was extruded at 160 ° C. by a twin screw extruder of a Laboplast mill to obtain a sheet having a thickness of 0.5 mm.

  After adjusting the state with NaCl 0.01M aqueous solution, the zeta potential was measured and found to be 8 mV. When the stability of the zeta potential was evaluated, it was stable with almost no change of 5 mV.

  Except for using a tube die with a lab plast mill twin screw extruder, it was extruded at 145 ° C. in the same manner as in Example 1, and the cylindrical microorganism had an outer diameter of about 4 mm, a length of about 4 mm, and a thickness of about 0.4 mm. An immobilization carrier was obtained. The obtained carrier was non-foamed, and fine irregularities of 0.05 mm were formed on the surface. When the wear resistance and fluidity of the obtained carrier were evaluated, the performance as a microorganism-immobilized carrier was sufficient.

Example 3
1 part by weight of polyethyleneimine (c2) and 15 parts by weight of filler (d1) are mixed with 100 parts by weight of 90 parts by weight of polyolefin resin (a1) and 10 parts by weight of maleic anhydride copolymer (b2). And it knead | mixed at the resin temperature of 170 degreeC using the same direction twin-screw extruder, and obtained the pellet. This pellet was extruded at 160 ° C. with a Laboplast mill single screw extruder to obtain a sheet having a thickness of 0.5 mm.

  After adjusting the state with NaCl 0.01M aqueous solution, the zeta potential was measured and found to be 1 mV. When the stability of the zeta potential was evaluated, it was stable with almost no change of 2 mV.

  Extrusion was performed at 145 ° C. in the same manner as in Example 1 to obtain a microorganism-immobilized carrier having an outer diameter of about 4 mm, a length of about 4 mm, and a thickness of about 0.3 mm. Fine irregularities of about 0.1 mm or less were formed on the surface of the obtained carrier. When the wear resistance and fluidity of the obtained carrier were evaluated, the performance as a microorganism-immobilized carrier was sufficient.

Example 4
Polyethyleneimine (c1) 0.3 parts by weight with respect to 100 parts by weight in total of 7 parts by weight of polyolefin resin (a1), 90 parts of polyolefin resin (a2) and 3 parts by weight of maleic anhydride copolymer (b1) And kneaded at a resin temperature of 175 ° C. using a same-direction twin-screw extruder to obtain pellets. The pellets were extruded at 165 ° C. with a lab plast mill single screw extruder to obtain a sheet having a thickness of 0.5 mm.

  After adjusting the state with a NaCl 0.01M aqueous solution, the zeta potential was measured and found to be -13 mV. When the stability of the zeta potential was evaluated, it was stable with almost no change of -10 mV.

  A cylindrical die having ribs on the outside as shown in FIG. 2 is used instead of the tube die, and extrusion is performed at 155 ° C. in the same manner as in Example 1 so that the outer diameter of the hollow cylinder having protrusions on the outside is about 4 mm. A microorganism-immobilized carrier having a thickness of about 5 mm, a length of about 4 mm, and a thickness of about 0.3 mm was obtained. When the wear resistance of the obtained carrier was evaluated, the wear amount was 0.1% or less and the durability was good. Since the specific gravity was 0.97, which is smaller than 1, in the fluidity evaluation, if the stirring was strengthened, it flowed in water, so the performance as a carrier was sufficient.

Example 5
Polyethyleneimine (c1) 0.5 weight with respect to a total of 100 weight parts of polyolefin resin (a1) 50 weight part, polyolefin resin (a3) 40 weight part, and maleic anhydride copolymer (b1) 10 weight part. Part and 20 parts by weight of filler (d1) were mixed and kneaded at a resin temperature of 165 ° C. using the same-direction twin screw extruder to obtain pellets. The pellets were extruded at 150 ° C. with a Laboplast mill single screw extruder to obtain a sheet having a thickness of 0.5 mm.

  After adjusting the state with NaCl 0.01M aqueous solution, the zeta potential was measured and found to be -5 mV. When the stability of the zeta potential was evaluated, it was stable with almost no change of -3 mV.

  Extrusion was performed at 140 ° C. in the same manner as in Example 1 to obtain a microorganism-immobilized support having an outer diameter of about 4 mm, a length of about 4 mm, and a thickness of about 0.2 mm. Fine irregularities of 0.01 to 0.05 mm were formed on the surface of the obtained carrier. When the wear resistance and fluidity of the obtained carrier were evaluated, the performance as a microorganism-immobilized carrier was sufficient.

Example 6
2 parts by weight of polyethyleneimine (c1) with respect to 100 parts by weight in total of 40 parts by weight of polyolefin resin (a1), 50 parts by weight of polyolefin resin (a4) and 10 parts by weight of maleic anhydride copolymer (b1), 25 parts by weight of the filler (d1) was mixed and kneaded at a resin temperature of 165 ° C. using a same-direction twin screw extruder to obtain pellets. The pellets were extruded at 150 ° C. with a Laboplast mill single screw extruder to obtain a sheet having a thickness of 0.5 mm.

  After adjusting the state with NaCl 0.01M aqueous solution, the zeta potential was measured and found to be 10 mV. When the stability of the zeta potential was evaluated, it was stable with almost no change of 8 mV.

  Extrusion was performed at 140 ° C. in the same manner as in Example 1 to obtain a microorganism-immobilized support having an outer diameter of about 4 mm, a length of about 4 mm, and a thickness of about 0.2 mm. Fine irregularities of about 0.1 mm or less were formed on the surface of the obtained carrier. When the wear resistance and fluidity of the obtained carrier were evaluated, the performance as a microorganism-immobilized carrier was sufficient.

Example 7
80 parts by weight of polyolefin resin (a1), 15 parts by weight of polyolefin resin (a5), 5 parts by weight of maleic anhydride copolymer (b1), 100 parts by weight of polyethyleneimine (c1), 25 parts by weight of filler (d1) and 0.1 part by weight of antioxidant (e1) were mixed and kneaded at a resin temperature of 180 ° C. using a same-direction twin screw extruder to obtain pellets. The pellets were extruded at 170 ° C. with a Laboplast mill single screw extruder to obtain a sheet having a thickness of 0.5 mm.

  After adjusting the state with NaCl 0.01M aqueous solution, the zeta potential was measured and found to be 5 mV. When the stability of the zeta potential was evaluated, it was stable with almost no change of 4 mV.

  Extrusion was performed at 165 ° C. in the same manner as in Example 1 to obtain a microorganism-immobilized support having an outer diameter of about 4 mm, a length of about 4 mm, and a thickness of about 0.3 mm. Fine irregularities of about 0.1 mm were formed on the surface of the obtained carrier. When the wear resistance and fluidity of the obtained carrier were evaluated, the performance as a microorganism-immobilized carrier was sufficient.

Comparative Example 1
100 parts by weight of the polyolefin resin (a1) used in Example 1 was extruded at 160 ° C. with a lab plast mill to obtain a sheet having a thickness of 0.5 mm. When the zeta potential was measured after adjusting the state with a NaCl 0.01M aqueous solution, it was as low as −20 mV.

  Extrusion was performed at 165 ° C. in the same manner as in Example 1 to obtain a microorganism-immobilized support having an outer diameter of about 4 mm, a length of about 4 mm, and a thickness of about 0.2 mm. When the fluidity of the obtained carrier was evaluated, the specific gravity was as low as 0.925. Therefore, even if the stirring of water was strengthened, most of the carrier floated on the water surface and could not be used as a microorganism-immobilized carrier. It was.

Comparative Example 2
100 parts by weight of polyolefin resin (a1), 0.5 part by weight of polyethyleneimine (c1), and 25 parts by weight of filler (d1) without using maleic anhydride copolymer (B) in the composition of Example 1. And pellets and sheets were obtained in the same manner as in Example 1. When the zeta potential of this sheet was measured, it was -5 mV, but as a result of evaluating the stability of the zeta potential, it deteriorated to -18 mV, and there was no long-term stability of the zeta potential, and the performance as a microorganism-immobilized carrier was poor. It was inferior.

Comparative Example 3
Without adding polyethyleneimine (C) in the composition of Example 1, 95 parts by weight of polyolefin resin (a1), 5 parts by weight of maleic anhydride copolymer (b1), and 25 parts by weight of filler (d1) The mixture was mixed and kneaded at a resin temperature of 165 ° C. using a same-direction twin screw extruder to obtain pellets. This pellet was extruded at 160 ° C. with a lab plast mill to obtain a sheet having a thickness of 0.5 mm. After adjusting the state with NaCl 0.01M aqueous solution, the zeta potential was measured and was a very low value of -25 mV.

Microorganism fixation test 20 g of the carrier of Example 1 of the present invention and the carrier of Comparative Example 3 were each added to 1 L of waste water containing activated sludge and slowly stirred, and the microorganism fixability was visually evaluated.

As a result of the evaluation, the carrier of Comparative Example 3 which did not contain polyethyleneimine (C) had very little microorganisms immobilized, but the carrier of Example 1 was about several days to one week away from microorganisms around the carrier. Fixation was observed, and the effect of the present invention was confirmed.
The results are shown in Table 1.

Claims (4)

0.01 to 10 parts by weight of polyethyleneimine (C) with respect to 100 parts by weight of a resin mixture containing 1 to 99 parts by weight of polyolefin resin (A) and 99 to 1 part by weight of maleic anhydride copolymer (B) A method for purifying wastewater, which comprises contacting a wastewater with a microorganism-immobilized carrier comprising a resin composition obtained by heating a mixture containing the mixture at 120 ° C to 250 ° C. The method for purifying wastewater according to claim 1, wherein the microorganism-immobilized carrier is a microorganism-immobilized carrier for anaerobic fluidized bed for wastewater purification. The method for purifying wastewater according to claim 1 or 2, wherein the resin composition further contains a filler (D). The method for purifying wastewater according to any one of claims 1 to 3, wherein the surface of the resin composition has a zeta potential of -15 to +15 mV.

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