Storage container for polymer flocculant emulsion, and method for storing polymer flocculant emulsion.

Abstract

The present invention provides a storage container suitable for storing a water-in-oil polymer flocculant emulsion, which contains a water-soluble polymer in the aqueous phase comprising at least one of cationic monomers, anionic monomers, or nonionic monomers as constituent units, and at least one of hydrocarbons, mineral oils, synthetic oils, or vegetable oils in the oil phase. [Solution] A storage container for polymer flocculant emulsion is used, characterized in that a polyolefin, in which an alkyl group is bonded to each monomer unit of the carbon chain constituting the main chain, adheres closely to the metal surface and coats the surface.

Description

Technical Field

[0001] The present invention relates to a storage container for a polymer flocculant emulsion and a method for storing a polymer flocculant emulsion.

Background Art

[0002] Polymer flocculants widely used in polymer flocculants for water treatment and papermaking chemicals generally exist in powder type and liquid type. Among these, the liquid type is widely adopted because of advantages such as easy handling during use, fast dissolution rate, and quantitative supply using a pump or the like. In particular, liquid polymer flocculants supplied as water-in-oil emulsions (W / O emulsions) play an important role in various industrial applications such as water treatment and papermaking processes because the dissolution process is simple.

[0003] Conventionally, these water-in-oil emulsion products are filled and supplied in cans with an inner surface coated with resin or the like, or in atron cans provided with an inner bag made of polyolefin inside a metal can in order to appropriately protect the contents and maintain the quality. These containers aim to reduce the risk of corrosion and quality deterioration by preventing direct contact between the contents and the metal. However, the following problems remain.

[0004] First, in the case of an inner surface coated can, during long-term storage or transportation, the coating may peel off due to the influence of oil or surfactant in the oil phase constituting the continuous phase of the emulsion. As a result, the quality of the contents may deteriorate. In addition, when the coating peels off, the moisture contained in the dispersed phase of the emulsion may directly contact the metal material constituting the can, causing corrosion (rust), which also has an adverse effect on the durability of the container and the quality of the contents. On the other hand, while Atron cans have a structure that avoids direct contact between the contents and metal by incorporating a polyolefin inner bag inside the metal can, there are challenges in disposal. These include the need to separate the inner bag from the metal can, which complicates the recycling process and increases disposal costs. Furthermore, if the inner bag is damaged during the discharge of the contents, it may become difficult to completely discharge the contents.

[0005] Furthermore, even if the polymer flocculant emulsion itself has high storage stability, its stability may be significantly reduced depending on the container in which it is stored.

[0006] These challenges necessitate technological solutions to improve the long-term storage and quality maintenance of emulsion products during transportation, as well as to enhance the recyclability and ease of disposal of containers. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 3976660 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] The present invention aims to solve various problems encountered in storage containers for conventional polymer flocculants in the form of water-in-oil emulsions used as polymer flocculants for water treatment and chemicals for papermaking. Specifically, it aims to improve the long-term storage and transportation of emulsion products, maintain quality, and enhance the recyclability and ease of disposal of containers. [Means for solving the problem]

[0009] Conventionally, polyethylene or polyethylene terephthalate has been used as the coating material for internally coated cans. However, when polyethylene and mineral oil are in contact for a long period of time in a high-temperature environment, the molecular motion of polyethylene becomes active, and the mineral oil may penetrate between the polyethylene molecules, reach the interface between the coating and the metal surface that makes up the can, and cause the coating to peel off. In addition, there is a possibility that the mineral oil may penetrate through low-density areas of the coating or through pinholes formed by impacts during transportation, and there is a possibility that the emulsifier may slightly corrode the polyethylene. As a result of diligent research into the above-mentioned problems, the present inventors have discovered that a container in which a polyolefin, in which an alkyl group is bonded to each monomer unit of the carbon chain constituting the main chain, adheres closely to and coats a metal surface can stably store a polymer flocculant in the form of a water-in-oil emulsion for a long period of time, and have completed the present invention.

[0010] The present invention, which solves the above problems, is described below.

[0011] [1] A metal container for storing a water-in-oil polymer flocculant emulsion, the aqueous phase containing a water-soluble polymer composed of at least one of cationic monomers, anionic monomers, or nonionic monomers, and the oil phase containing at least one of hydrocarbons, mineral oil, synthetic oil, or vegetable oil, The aforementioned metal container is a storage container for polymer flocculant emulsions, characterized in that a polyolefin, in which an alkyl group is bonded to each monomer unit of the carbon chain constituting the main chain, adheres closely to the metal surface and coats the surface.

[0012] [2] The storage container for polymer flocculant emulsion according to [1], wherein the polyolefin is polypropylene.

[0013] [3] A method for storing a water-in-oil polymer flocculant emulsion, the aqueous phase containing a water-soluble polymer composed of at least one of cationic monomers, anionic monomers, or nonionic monomers, and the oil phase containing at least one of hydrocarbons, mineral oil, synthetic oil, or vegetable oil, A method for storing a polymer flocculant emulsion, characterized by storing the polymer flocculant emulsion in contact with a polyolefin in which an alkyl group is bonded to each monomer unit of the carbon chain constituting the main chain, in a storage container, and by closely coating the metal surface constituting the storage container that comes into contact with the polymer flocculant emulsion with the polyolefin.

[0014] [4] A method for storing the polymer flocculant emulsion described in [3], wherein the polyolefin is polypropylene. [Effects of the Invention]

[0015] The present invention provides a storage container and a storage method that enable the stable long-term storage of a polymer flocculant in the form of a water-in-oil emulsion. [Modes for carrying out the invention]

[0016] The present invention will be described in detail below. In this specification, PE refers to polyethylene, PP refers to polypropylene, PET refers to polyethylene terephthalate, and TFS refers to Wuxi steel sheet. In this specification, acrylates and / or methacrylates may be referred to as (meth)acrylate; acrylamides and / or methacrylamides as (meth)acrylamide; and acrylic acid and / or methacrylic acid as (meth)acrylic acid. Additionally, acrylic acid and / or its salts may be referred to as acrylic acid (salt).

[0017] 1. Storage container for polymer flocculant emulsion The storage container for the polymer flocculant emulsion of the present invention is a metal container for storing a water-in-oil type polymer flocculant emulsion containing a water-soluble polymer having at least one kind of cationic monomer, anionic monomer, or nonionic monomer as a structural unit in the aqueous phase and containing at least one kind of hydrocarbon, mineral oil, synthetic oil, or vegetable oil in the oil phase. This metal container is characterized in that a polyolefin in which an alkyl group is bonded to each monomer unit of the carbon chain constituting the main chain adheres to the metal surface in contact with the polymer flocculant emulsion and covers the surface thereof.

[0018] 1-1. Polymer flocculant emulsion The storage container of the present invention targets a water-in-oil type polymer flocculant emulsion containing a water-soluble polymer having at least one kind of cationic monomer, anionic monomer, or nonionic monomer as a structural unit in the aqueous phase and containing at least one kind of hydrocarbon, mineral oil, synthetic oil, or vegetable oil in the oil phase.

[0019] Examples of the cationic monomer include tertiary salts such as hydrochlorides and sulfates of dialkylaminoalkyl (meth) acrylates such as dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, and diethylamino-2-hydroxypropyl (meth) acrylate; quaternary salts such as alkyl halide adducts such as methyl chloride adducts of dialkylaminoalkyl (meth) acrylates and aryl halide adducts such as benzyl chloride adducts; tertiary salts such as hydrochlorides and sulfates of dialkyl (meth) acrylamides such as N,N-dimethyl (meth) acrylamide; and quaternary salts such as alkyl halide adducts such as methyl chloride adducts of dialkyl (meth) acrylamides and aryl halide adducts such as benzyl chloride adducts.

[0020] Examples of anionic monomers include (meth)acrylic acid and its alkali metal salts or ammonium salts such as sodium salt; maleic acid and its alkali metal salts; acrylamide alkylalkanesulfonic acids such as acrylamide-2-methylpropanesulfonic acid and its alkali metal salts or ammonium salts; and vinylsulfonic acid and its alkali metal salts or ammonium salts.

[0021] Examples of nonionic monomers include (meth)acrylamide, dialkylaminoalkyl (meth)acrylates such as dimethylaminoethyl (meth)acrylate, dialkylaminoalkyl (meth)acrylamides such as dialkylaminopropyl (meth)acrylamide, styrene, acrylonitrile, vinyl acetate, alkyl acrylates, alkyl methacrylates, vinyl pyridine, vinyl imidazole, and allylamine.

[0022] Any of these monomers can be used alone or in combination of two or more. Examples of monomer combinations include copolymers composed of a tertiary or quaternary salt of a dialkylaminoalkyl acrylate as a cationic monomer, acrylate as an anionic monomer, and acrylamide as a nonionic monomer; copolymers composed of a tertiary or quaternary salt of a dialkylaminoalkyl methacrylate as a cationic monomer, acrylate as an anionic monomer, and acrylamide as a nonionic monomer; and copolymers composed of a tertiary or quaternary salt of a dialkylaminoalkyl methacrylate as a cationic monomer, a tertiary or quaternary salt of a dialkylaminoalkyl acrylate, acrylate as an anionic monomer, and acrylamide as a nonionic monomer.

[0023] As a method for producing a polymer flocculant emulsion, an emulsification step of mixing an aqueous phase composed of an aqueous solution of the above-mentioned monomer mixture with an oil phase containing a hydrocarbon substantially immiscible with water and a surfactant to form a water-in-oil type monomer emulsion; A polymerization step of polymerizing monomers in the dispersed phase of a water-in-oil monomer emulsion in the presence of a radical polymerization initiator to produce a water-in-oil polymer emulsion containing a polymer, which is a polymer of the monomer, in the dispersed phase; A manufacturing method consisting of the above can be given as an example.

[0024] The polymer flocculant emulsion targeted by the present invention contains at least one of hydrocarbons, mineral oils, synthetic oils, or vegetable oils in the oil phase. Hydrocarbons with a boiling point in the range of 65 to 180°C at atmospheric pressure are preferred, and those with a boiling point in the range of 65 to 130°C are more preferred. Specifically, examples include n-hexane, cyclohexane, n-heptane, n-octane, and isooctane. Examples of mineral oils include paraffinic mineral oils and naphthenic mineral oils. Examples of synthetic oils include poly-α-olefins, silicone oils, and ester oils. Examples of vegetable oils include soybean oil, rapeseed oil, and castor oil. These oil phases are substantially immiscible with water. Substantially immiscible with water means that the solubility in water at 25°C is less than 1000 mg / L. These components that make up the oil phase may be used individually or in combination. The amount of oil phase used is preferably 15 to 50% by mass of the total amount of the water-in-oil emulsion.

[0025] Examples of surfactants used in polymer flocculant emulsions covered by the present invention include nonionic surfactants. Specifically, these include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, and polyoxyethylene oleyl ether; sorbitan alkylates such as sorbitan monooleate, sorbitan sesquioleate, and sorbitan monolaurate; polyoxyethylene monooleates such as polyoxyethylene sorbitan monooleate and polyoxyethylene sorbitan monolaurate; and polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitan tetraoleate, polyethylene glycol monooleate, polyethylene glycol dioleate, oleic acid diethanolamide, lauric acid monoethanolamide, stearic acid monoethanolamide, and the like.

[0026] The amount of surfactant added is preferably 0.25 to 15% by mass, and more preferably 0.5 to 10% by mass, relative to the total amount of the water-in-oil emulsion.

[0027] The emulsification conditions are set appropriately according to the composition of the aqueous and oil phases and the emulsifier used. While there are no particular restrictions on the ratio of aqueous phase to oil phase in a water-in-oil emulsion, the W / O ratio, which is the value obtained by dividing the mass of the aqueous phase by the mass of the oil phase, is generally between 2.0 and 3.5. By setting the W / O ratio within this range, polymerization stability and storage stability can be increased, and the water-in-oil emulsion can be easily inverted during use. If the W / O ratio is less than 2.0, the large amount of oil phase can cause the emulsion particles to settle easily, which may reduce storage stability.

[0028] The polymer purity in water-in-oil emulsions is 10-50% by mass. A higher polymer purity allows for a reduced amount of polymer flocculant, resulting in greater cost-effectiveness. The polymer purity in water-in-oil emulsions is substantially equal to the purity of the starting monomer.

[0029] The median diameter of emulsified particles in polymer flocculant emulsions is generally around 0.7 to 10 μm. In this invention, the median diameter of emulsified particles is the median diameter (D) in the volume-average particle size distribution measured by laser diffraction. 50 ) means.

[0030] Polymerization conditions are set appropriately depending on the monomers, initiators, and properties of the polymer used. The polymerization temperature is generally 0 to 100°C. The monomer concentration in the monomer aqueous solution is approximately 20 to 50% by mass. The polymerization time is generally 1 to 10 hours.

[0031] Examples of polymerization initiators include persulfates such as sodium persulfate and potassium persulfate; organic peroxides such as benzoyl peroxide, t-butyl hydroperoxide, and paramenthane hydroperoxide; redox catalysts formed by combining these with sodium disulfite, ferrous ammonium sulfate, sulfur dioxide, etc.; and known azo compounds such as 2,2'-azobis-(amidinopropane) hydrochloride, azobiscyanovaleric acid, 2,2'-azobisisobutyronitrile, and 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide]. These polymerization initiators may be used alone or in combination of two or more.

[0032] As a method for adjusting molecular weight, known chain transfer agents can be used. Known chain transfer agents include thiol compounds such as mercaptoethanol and mercaptopropionic acid, reducing inorganic salts such as sodium sulfite, sodium bisulfite and sodium hypophosphate, alcohols such as ethanol and isopropyl alcohol, and allyl compounds such as sodium methallyl sulfonate.

[0033] After polymerization, a hydrophilic surfactant called a phase inversion agent can be added. Typically, polymer flocculant emulsions are first dissolved in water at a suitable concentration before being added to the water to be treated (wastewater, etc.). Adding a phase inversion agent causes the emulsion to be phase-inverted or deemulsified, making the emulsion particles containing the polymer more compatible with water and easier to dissolve in water. Examples of surfactants used as phase inversion agents include cationic surfactants and nonionic surfactants with an HLB value of 9 to 17. Specifically, examples include polyethylene glycol monooleate and polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether. The amount of phase inversion agent added is 1 to 5% by mass of the total mass of the emulsion.

[0034] In addition, additives such as stabilizers, pH adjusters, and antioxidants may be added.

[0035] The viscosity of the polymer flocculant emulsion is preferably between 100 and 100,000 mPa·s. If the viscosity exceeds 100,000 mPa·s, it may be difficult to remove the polymer flocculant emulsion from the container.

[0036] 1-2. Structure of a storage container for polymer flocculant emulsions The storage container for polymer flocculant emulsion of the present invention is characterized in that a polyolefin, in which an alkyl group is bonded to each monomer unit of the carbon chain constituting the main chain, adheres closely to and coats the surface of a metal surface that can come into contact with the polymer flocculant emulsion. Alternatively, the polyolefin, in which an alkyl group is bonded to each monomer unit of the carbon chain constituting the main chain, may be formed in close contact with the metal surface via other layers.

[0037] Examples of polyolefins in which an alkyl group is bonded to each monomer unit of the carbon chain constituting the main chain used in the container of the present invention include polypropylene and ethylene-butene copolymer. Among these, polypropylene in which a methyl group is added to the carbon chain constituting the main chain is preferred.

[0038] The metal materials used in the containers of the present invention are generally cold-rolled steel sheets, plated steel sheets, aluminum, etc., in order to ensure the strength, corrosion resistance, and workability of the containers.

[0039] In this invention, a coating layer made of polyolefin, in which alkyl groups are bonded to each monomer unit of the carbon chain constituting the main chain, is formed on the inner surface of a metal can. Conventional known methods can be used to form the coating layer. First, a degreasing treatment is performed to remove oil and dirt from the metal surface. In this case, an organic solvent or an alkaline cleaning solution is used. After that, surface roughening may be performed by sandblasting or chemical etching in order to improve adhesion to the surface. In addition, an epoxy-based or polyolefin-based primer may be applied in order to improve adhesion with the polyolefin. The polyolefin material used as a coating is supplied in granular or sheet form and applied to the metal surface by a molding method described later. Methods for forming the polyolefin layer include melt extrusion coating, lamination, and spray coating. In the melt extrusion coating method, polyolefin resin is heated to 180-300°C to a molten state and uniformly applied to the inner surface of the metal can. During this process, an extruder is used to directly press the resin against the metal surface, and cooling allows for the formation of a strong adhesive layer. In contrast, the lamination method involves attaching a polyolefin film to the inner surface of the metal can, then heating and pressing it at 180-250°C, followed by cooling to form an adhesive layer. The spray coating method involves spraying molten polyolefin onto the metal surface, followed by heating and cooling processes to form a uniform coating layer. To completely cure the coating layer, a baking treatment at 180-250°C may be performed after coating. The final thickness of the coating layer is preferably 10-200 μm, and more preferably 20-100 μm. The metal material formed in this manner is cut to predetermined dimensions and processed into parts for the can's body, bottom, and lid. To form the body, metal sheets are bent into a cylindrical or prismatic shape and joined together with adhesive or welding. A sealant may be applied to these joints to prevent leaks. The bottom is formed separately, flanged to join with the body, and then double-sealed to ensure a tight seal. In the lid manufacturing process, holes for the pouring spout and ventilation are made in the lid body, and metal or plastic spout parts are attached thereto. The body, bottom, and lid are finally joined together by double-sealing or other methods to ensure airtightness.

[0040] 2. Storage method for polymer flocculant emulsions The present invention provides a method for storing a water-in-oil polymer flocculant emulsion, comprising a water-soluble polymer in the aqueous phase, comprising at least one of a cationic monomer, anionic monomer, or nonionic monomer as a constituent unit, and an oil phase comprising at least one of a hydrocarbon, mineral oil, synthetic oil, or vegetable oil. The method is characterized by storing a polymer flocculant emulsion and a polyolefin, in which an alkyl group is bonded to each monomer unit of the carbon chain constituting the main chain, in contact in a storage container, and by closely coating the metal surface of the storage container that comes into contact with the polymer flocculant emulsion with the polyolefin.

[0041] As explained earlier, polymer flocculant emulsions and polyolefins in which alkyl groups are bonded to each monomer unit of the carbon chain that constitutes the main chain are as described above.

[0042] By storing a polymer flocculant emulsion in a storage container in contact with a polyolefin in which alkyl groups are bonded to each monomer unit of the carbon chain that constitutes the main chain, the generation of coagulated material (hereinafter referred to as "coagulum") caused by the separation of the emulsion can be suppressed. [Examples]

[0043] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The methods for various tests are as follows.

[0044] [Presence or absence of peeling] The presence or absence of peeling of the coating layer covering the metal surface of the container was visually observed and evaluated according to the following criteria. ×: Delamination between the metal surface and the coating layer is observed. △: Slight delamination between the metal surface and the coating layer is observed. ○: No delamination between the metal surface and the coating layer was observed.

[0045] [Presence or absence of rust] The presence or absence of rust on the metal surface of the container was visually inspected and evaluated according to the following criteria. ×: Rust is observed on the metal surface. △: Slight rust is observed on the metal surface. ○: No rust is observed on the metal surface.

[0046] [Presence or absence of core group] The presence or absence of coagulants of polymer flocculant in the container was visually observed and evaluated according to the following criteria. ×: Accept the coagule. △: Coagules are present, but the emulsified state is maintained and redispersible. ○: Do not recognize the coagule.

[0047] <Manufacturing Example 1> Method for producing a cationic polymer flocculant emulsion 26.9 g of surfactant was weighed into a five-necked separable flask, and 242.0 g of paraffin oil was added and dissolved to prepare 268.8 g of oil phase. The surfactant consisted of 11.7 g (44% by mass) of sorbitan sesquioleate with an HLB value of 3.7, 3.9 g (14% by mass) of oleic acid diethanolamide with an HLB value of 9.2, and 11.3 g (42% by mass) of polyethylene glycol monooleate with an HLB value of 13.5. The weighted average HLB value of the surfactant was 8.6. 389.4 g of a 79% by mass aqueous solution of dimethylaminoethyl acrylate methyl quaternary salt (DAC) and 184.8 g of a 50% by mass aqueous solution of acrylamide (AM) were mixed. 0.008 g of methylenebisacrylamide (MBA), 2.4 g of isopropyl alcohol, 0.2 g of the chelating agent EDTA, 0.01 g of t-butyl hydroperoxide as an initiator, and deionized water were added. The pH was adjusted to 4.0 with 98% sulfuric acid to prepare 672.3 g of aqueous phase. The molar ratio of DAC to AM was 55:45. The amount of MBA added was 20 ppm relative to the total mass of monomers. The amount of surfactant added was 2.9% by mass relative to the total amount of aqueous and oil phases. The mass ratio (W / O ratio) of the aqueous phase to the oil phase was 2.5. An aqueous phase was added to the oil phase while stirring, and the mixture was rapidly stirred in a homogenizer to prepare a water-in-oil emulsion. A nitrogen gas inlet tube, reflux condenser, and thermometer were attached to a five-necked separable flask, and nitrogen gas was supplied while stirring with a stirring blade to replace the gas phase in the system with nitrogen. After the water-in-oil emulsion was brought to 20°C, nitrogen gas containing 0.02 vol% sulfur dioxide was further injected into the water-in-oil emulsion at a rate of 12 ml / min while supplying nitrogen gas, and polymerization was started. After reaching 50°C, this temperature was maintained for 2 hours, then the supply of nitrogen gas containing sulfur dioxide was increased to 190 ml / min, and the mixture was maintained at 50°C for 1 hour. Then the supply of nitrogen gas containing sulfur dioxide was stopped, and 3.9 g of a 1% aqueous solution of sodium disulfite was added and held for 30 minutes. The supply of nitrogen gas was stopped, and polymerization was terminated. To this, 39.4 g of malic acid and 15.4 g of polyethylene glycol monooleate with an HLB value of 13.5 as a phase inversion agent were added to obtain a water-in-oil polymer emulsion with a polymer content of 40.0% by mass and a median diameter of emulsion particles of 1.6 μm.

[0048] <Manufacturing Example 2> Method for producing an anionic polymer flocculant emulsion 23.9 g of surfactant was weighed into a five-necked separable flask, and 249.7 g of paraffin oil was added and dissolved to prepare 273.6 g of oil phase. The surfactant consisted of 15.1 g (63% by mass) of sorbitan sesquioleate with an HLB value of 3.7, 5.0 g (21% by mass) of oleic acid diethanolamide with an HLB value of 9.2, and 3.8 g (16% by mass) of polyethylene glycol monooleate with an HLB value of 13.5. The weighted average HLB value of the surfactant was 6.4. 535.0 g of a 50% by mass aqueous solution of acrylamide (AM) was mixed with 69.4 g of 80% by mass acrylic acid (AcA), neutralized with 48% by mass sodium hydroxide solution, and adjusted to pH 7.0. To this, 0.06 g of the chelating agent EDTA, 1.9 g of isopropyl alcohol, 0.008 g of t-butyl hydroperoxide as an initiator, and deionized water were added to prepare 684.2 g of aqueous phase. The molar ratio of AM to AcA was 83:17. The amount of surfactant added was 2.5% by mass relative to the total amount of aqueous and oil phases. The mass ratio (W / O) of the aqueous phase to the oil phase was 2.5. An aqueous phase was added to the oil phase while stirring, and the mixture was rapidly stirred in a homogenizer to prepare a water-in-oil emulsion. A nitrogen gas inlet tube, reflux condenser, and thermometer were attached to a five-necked separable flask, and nitrogen gas was supplied while stirring with a stirring blade to replace the gas phase in the system with nitrogen. After the water-in-oil emulsion was brought to 10°C, nitrogen gas containing 0.02 vol% sulfur dioxide was added to the emulsion at a rate of 20 ml / min while supplying nitrogen gas, and polymerization was started. After reaching 40°C, this temperature was maintained for 2 hours, then the supply of nitrogen gas containing sulfur dioxide was increased to 160 ml / min, and the mixture was maintained at 40°C for 1 hour. Then the supply of nitrogen gas containing sulfur dioxide was stopped, and 11.3 g of a 30% aqueous solution of sodium disulfite was added and held for 30 minutes. The supply of nitrogen gas was stopped, and polymerization was terminated. To this, 30.8 g of polyethylene glycol monooleate with an HLB value of 13.5 was added as a phase inversion agent to obtain a water-in-oil polymer emulsion with a polymer content of 34.0% by mass and a median diameter of emulsion particles of 1.2 μm.

[0049] [Examples 1-2, Comparative Examples 1-5] The cationic polymer flocculant emulsion produced in Production Example 1 was filled into various containers to approximately half their volume, capped and sealed, stored at 50°C, and its condition was observed over time. The evaluation results are shown in Table 1. In the table, PE stands for polyethylene, PP for polypropylene, PET for polyethylene terephthalate, and TFS for Wuxi steel sheet. When written as "PP / TFS," it means that a polypropylene coating layer is tightly laminated onto the inner wall of a can made of Wuxi steel plate. "PE inner bag / TFS" means that an independent polyethylene bag-like container is loaded inside a TFS can. Example 1 and Comparative Examples 1 and 2 are 18-liter cans manufactured by joining the can body joint by adhesive bonding, and joining the bottom to the body and the lid to the body by double seam sealing. Examples 2, Comparative Examples 3 and 4 are 18-liter cans manufactured by welding the can body joint, applying paint to any exposed metal material (or areas where exposure is suspected) due to welding, and joining the bottom to the body and the lid to the body using double seam sealing. Comparative Example 5 is an Atron can (18-liter can), and from the beginning, the inner bag and TFS are not in close contact.

[0050] [Table 1]

[0051] In Examples 1 and 2, no peeling of the coating layer was observed even after storage at 50°C for 7 months, and almost no rust formation was observed. In Comparative Example 1, the coating layer peeled off after being stored at 50°C for one month, so the test was discontinued. In Comparative Example 2, no peeling of the coating layer was observed even after storage at 50°C for 7 months, but rust occurred after 3 months of storage. In Comparative Example 3, no peeling of the coating layer was observed even after storage at 50°C for 3 months, but rust occurred after 1 month of storage, so the test was discontinued. In Comparative Example 4, the coating layer peeled off and rust occurred after storage at 50°C for one month, so the test was discontinued. In Comparative Example 5, wetting was observed on the outside of the PE inner bag immediately after filling, so the test was stopped.

[0052] [Examples 3-4, Comparative Examples 6-10] The anionic polymer flocculant emulsion produced in Production Example 2 was filled into various containers to approximately half their volume, capped and sealed, stored at 50°C, and its condition was observed over time. The evaluation results are shown in Table 2.

[0053] [Table 2]

[0054] In Examples 3 and 4, no peeling of the coating layer was observed even after storage at 50°C for 7 months, and almost no rust was observed. Furthermore, because the PP was stored in contact with the polymer flocculant emulsion, there was almost no coagulation. In Comparative Example 6, the coating layer peeled off after being stored at 50°C for one month, so the test was discontinued. In Comparative Example 7, no peeling of the coating layer was observed even after storage at 50°C for 7 months, but rust occurred after 3 months of storage. In Comparative Example 8, no peeling of the coating layer was observed even after storage at 50°C for 3 months, but rust occurred after 1 month of storage, so the test was discontinued. In Comparative Example 9, the coating layer peeled off and rust formed after storage at 50°C for one month, so the test was discontinued. In Comparative Example 10, wetting was observed on the outside of the PE inner bag immediately after filling, so the test was stopped.

Claims

1. A metal container for storing a water-in-oil polymer flocculant emulsion, the aqueous phase containing a water-soluble polymer composed of at least one of cationic monomers, anionic monomers, or nonionic monomers, and the oil phase containing at least one of hydrocarbons, mineral oil, synthetic oil, or vegetable oil, The aforementioned metal container is a storage container for polymer flocculant emulsions, characterized in that a polyolefin, in which an alkyl group is bonded to each monomer unit of the carbon chain constituting the main chain, adheres closely to the metal surface and coats the surface.

2. The storage container for polymer flocculant emulsion according to claim 1, wherein the polyolefin is polypropylene.

3. A method for storing a water-in-oil polymer flocculant emulsion, comprising a water-soluble polymer composed of at least one of cationic monomers, anionic monomers, or nonionic monomers in the aqueous phase, and at least one of hydrocarbons, mineral oil, synthetic oil, or vegetable oil in the oil phase, A method for storing a polymer flocculant emulsion, characterized by storing the polymer flocculant emulsion in contact with a polyolefin in which an alkyl group is bonded to each monomer unit of the carbon chain constituting the main chain, in a storage container, and by closely coating the metal surface constituting the storage container that comes into contact with the polymer flocculant emulsion with the polyolefin.

4. The method for storing a polymer flocculant emulsion according to claim 3, wherein the polyolefin is polypropylene.

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