Copolymer latex for carbon dioxide separation membrane, composition for carbon dioxide separation membrane, carbon dioxide separation membrane, and method for producing carbon dioxide separation membrane

Abstract

To provide: a carbon dioxide separation membrane which has excellent carbon dioxide selective permeability and sufficient carbon dioxide permeability, and has excellent strength and flexibility; and a copolymer latex for the carbon dioxide separation membrane, a composition for the carbon dioxide separation membrane, and a method for preparing the carbon dioxide separation membrane.SOLUTION: A copolymer latex for a carbon dioxide separation membrane contains a copolymer having an aliphatic conjugated diene monomer unit, where the content of the aliphatic conjugated diene monomer unit in the copolymer is 10-80 mass%. A carbon dioxide separation membrane contains the copolymer. A method for preparing the carbon dioxide separation membrane comprises a step of coagulating a composition for a carbon dioxide separation membrane by a salt coagulation method, where the composition for a carbon dioxide separation membrane contains the copolymer.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a copolymer latex for a carbon dioxide separation membrane, a composition for a carbon dioxide separation membrane, a carbon dioxide separation membrane, and a method for producing a carbon dioxide separation membrane.

Background Art

[0002] In recent years, for the purpose of reducing the emission amount of greenhouse gases, methods for separating and recovering greenhouse gases have been studied.

[0003] As a method for separating and recovering carbon dioxide, which is one of the typical greenhouse gases, for example, separation by a separation membrane and separation by an adsorbent have been studied. More specifically, in Patent Document 1, separation of carbon dioxide by a resin membrane composed of a resin composition containing a polyimide resin and an ionic liquid has been studied, and in Patent Document 2, absorption and desorption of carbon dioxide by an absorber mainly composed of a polymer having a specific structure and having a plurality of pores have been studied.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, various carbon dioxide separation membranes have been studied in addition to the separation membrane described in Patent Document 1 above, but there is still a demand for a carbon dioxide separation membrane having excellent carbon dioxide selective permeability. In addition, the carbon dioxide separation membrane is required to have excellent strength and flexibility.

[0006] An object of the present invention is to provide a carbon dioxide separation membrane having excellent carbon dioxide selective permeability and sufficient carbon dioxide permeability, and having excellent strength and flexibility. Another object of the present invention is to provide a copolymer latex for a carbon dioxide separation membrane, a composition for a carbon dioxide separation membrane, and a method for producing a carbon dioxide separation membrane.

Means for Solving the Problems

[0007] The present inventors have found that a carbon dioxide separation membrane formed from a composition containing a copolymer latex having an aliphatic conjugated diene monomer unit in a specific content has excellent carbon dioxide selective permeability and sufficient carbon dioxide permeability, and also has excellent membrane strength and flexibility.

[0008] That is, the present invention provides the following [1] to [6]. [1] A copolymer latex for a carbon dioxide separation membrane, containing a copolymer having an aliphatic conjugated diene monomer unit, wherein the content of the aliphatic conjugated diene monomer unit in the copolymer is 10 to 80% by mass. [2] The copolymer latex for a carbon dioxide separation membrane according to [1], wherein the copolymer further has an ethylenically unsaturated carboxylic acid monomer unit, and the content of the ethylenically unsaturated carboxylic acid monomer unit in the copolymer is 0.1 to 10% by mass. [3] A composition for a carbon dioxide separation membrane, containing the copolymer latex for a carbon dioxide separation membrane according to [1] or [2]. [4] The composition for a carbon dioxide separation membrane according to [3], further containing zinc oxide. [5] A carbon dioxide separation membrane, containing a copolymer having an aliphatic conjugated diene monomer unit, wherein the content of the aliphatic conjugated diene monomer unit in the copolymer is 10 to 80% by mass. [6] A method for producing a carbon dioxide separation membrane, comprising a step of coagulating a composition for a carbon dioxide separation membrane by a salt coagulation method. The composition for a carbon dioxide separation membrane contains a copolymer having an aliphatic conjugated diene monomer unit. A method wherein the content of the aliphatic conjugated diene monomer unit in the copolymer is 10 to 80% by mass.

Advantages of the Invention

[0009] According to the present invention, it is possible to provide a carbon dioxide separation membrane having excellent carbon dioxide selective permeability and sufficient carbon dioxide permeability, and having excellent strength and flexibility. Further, according to the present invention, it is possible to provide a copolymer latex for a carbon dioxide separation membrane, a composition for a carbon dioxide separation membrane, and a method for producing a carbon dioxide separation membrane.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

[0011] [Copolymer Latex for Carbon Dioxide Separation Membrane] The copolymer latex for a carbon dioxide separation membrane according to an embodiment of the present invention (hereinafter, also simply referred to as "copolymer latex") contains a copolymer having an aliphatic conjugated diene monomer unit. The content of the aliphatic conjugated diene monomer unit in the copolymer is 10 to 80% by mass. Hereinafter, this copolymer is also referred to as "copolymer A".

[0012] Examples of the aliphatic conjugated diene monomer include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, pentadienes (for example, substituted linear conjugated pentadienes), and hexadienes (for example, substituted and side-chain conjugated hexadienes). Copolymer A may have one or more aliphatic conjugated diene monomer units. From the viewpoint of more excellent strength and flexibility of the obtained carbon dioxide separation membrane, copolymer A preferably has a structural unit derived from 1,3-butadiene as the aliphatic conjugated diene monomer unit.

[0013] The content of the aliphatic conjugated diene monomer unit in the copolymer A is 10 to 80% by mass. When the content of the aliphatic conjugated diene monomer unit is 10% by mass or more, it becomes possible to form a film of the composition containing the copolymer A, and a carbon dioxide separation membrane can be produced. When the content of the aliphatic conjugated diene monomer unit is 80% by mass or less, excellent carbon dioxide selective permeability, sufficient carbon dioxide permeability, strength, and flexibility can be realized. From the viewpoint that the carbon dioxide permeability of the obtained carbon dioxide separation membrane is more excellent, the content of the aliphatic conjugated diene monomer unit in the copolymer A is preferably 20% by mass or more, and more preferably 30% by mass or more. From the viewpoint that the strength and flexibility of the obtained carbon dioxide separation membrane are more excellent, the content of the aliphatic conjugated diene monomer unit in the copolymer A is preferably 75% by mass or less, and more preferably 70% by mass or less. From these viewpoints, the content of the aliphatic conjugated diene monomer unit in the copolymer A is preferably 20 to 75% by mass, and more preferably 30 to 70% by mass.

[0014] In addition to the aliphatic conjugated diene monomer unit, the copolymer A may have a vinyl cyanide monomer unit, an aromatic vinyl monomer unit, an unsaturated carboxylic acid alkyl ester monomer unit, an unsaturated monomer unit containing a hydroxyalkyl group, an ethylenically unsaturated carboxylic acid monomer unit, an unsaturated carboxylic acid amide monomer unit, a polyfunctional ethylenically unsaturated monomer unit containing two or more unsaturated double bonds, etc. From the viewpoint that the strength and flexibility of the carbon dioxide separation membrane are more excellent, the copolymer A may have an ethylenically unsaturated carboxylic acid monomer unit. The copolymer A may have one or two or more of these monomer units.

[0015] Examples of the vinyl cyanide monomer include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, and α-ethylacrylonitrile. The copolymer A may have one or more vinyl cyanide monomer units. The copolymer A may have a structural unit derived from acrylonitrile as a vinyl cyanide monomer unit.

[0016] The content of the vinyl cyanide monomer unit in the copolymer A is preferably 50% by mass or less, more preferably 40% by mass or less, and still more preferably 30% by mass or less. The content of the vinyl cyanide monomer unit in the copolymer A may be 1% by mass or more, 3% by mass or more, or 5% by mass or more.

[0017] Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, methyl-α-methylstyrene, vinyltoluene, and divinylbenzene. The copolymer A may have one or more aromatic vinyl monomer units. The copolymer A may have a structural unit derived from styrene as an aromatic vinyl monomer unit.

[0018] The content of the aromatic vinyl monomer unit in the copolymer A may be 80% by mass or less, 70% by mass or less, or 65% by mass or less, and may also be 20% by mass or more, 25% by mass or more, or 30% by mass or more.

[0019] Examples of the unsaturated carboxylic acid alkyl ester monomers include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, glycidyl methacrylate, dimethyl fumarate, diethyl fumarate, dimethyl maleate, diethyl maleate, dimethyl itaconate, monomethyl fumarate, monoethyl fumarate, and 2-ethylhexyl acrylate. The copolymer A may have one or more unsaturated carboxylic acid alkyl ester monomer units. The copolymer A may have a structural unit derived from methyl methacrylate as an unsaturated carboxylic acid alkyl ester monomer unit.

[0020] The content of the unsaturated carboxylic acid alkyl ester monomer unit in the copolymer A may be 80% by mass or less, 70% by mass or less, or 60% by mass or less, and may also be 1% by mass or more, 2% by mass or more, or 3% by mass or more.

[0021] Examples of the unsaturated monomers containing a hydroxyalkyl group include hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, 3-chloro-2-hydroxypropyl methacrylate, di-(ethylene glycol) maleate, di-(ethylene glycol) itaconate, 2-hydroxyethyl maleate, bis(2-hydroxyethyl) maleate, and 2-hydroxyethyl methyl fumarate. The copolymer A may have one or more unsaturated monomer units containing a hydroxyalkyl group. The copolymer A may have a structural unit derived from β-hydroxyethyl acrylate as an unsaturated monomer unit containing a hydroxyalkyl group.

[0022] The content of the unsaturated monomer unit containing a hydroxyalkyl group in the copolymer A may be 10% by mass or less, 5% by mass or less, or 3% by mass or less, and may also be 0.1% by mass or more, 0.5% by mass or more, or 1% by mass or more.

[0023] Examples of the unsaturated carboxylic acid amide monomers include acrylamide, methacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, and N,N-dimethylacrylamide. The copolymer A may have one or more unsaturated carboxylic acid amide monomer units. The copolymer A may have a structural unit derived from acrylamide as the unsaturated carboxylic acid amide monomer unit.

[0024] Examples of the ethylenically unsaturated carboxylic acid monomers include monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; and dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid. The copolymer A may have one or more ethylenically unsaturated carboxylic acid monomer units. The copolymer A may have a structural unit derived from at least one selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, and fumaric acid as the ethylenically unsaturated carboxylic acid monomer unit.

[0025] The content of the ethylenically unsaturated carboxylic acid monomer unit in copolymer A is preferably 0.1 to 10% by mass. When the content of the ethylenically unsaturated carboxylic acid monomer unit is 0.1% by mass or more, copolymer A can be stably polymerized, so that the formation of aggregates can be suppressed, and the strength and flexibility of the resulting carbon dioxide separation membrane are more excellent. When the content of the ethylenically unsaturated carboxylic acid monomer unit is 10% by mass or less, it is possible to suppress the viscosity of copolymer A from becoming too high during synthesis, so that it can be sufficiently stirred and copolymer A can be stably polymerized. Furthermore, the resulting copolymer A tends to be easily formed into a film. The content of the ethylenically unsaturated carboxylic acid monomer unit in copolymer A is more preferably 0.5% by mass or more, and still more preferably 1% by mass or more. The content of the ethylenically unsaturated carboxylic acid monomer unit in copolymer A is more preferably 8% by mass or less, and still more preferably 7% by mass or less. The content of the ethylenically unsaturated carboxylic acid monomer unit in copolymer A is more preferably 0.5 to 8% by mass, and still more preferably 1 to 7% by mass.

[0026] Examples of the polyfunctional ethylenically unsaturated monomer containing two or more unsaturated double bonds include allyl methacrylate; polyethylene glycol di(meth)acrylate such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, and triethylene glycol di(meth)acrylate; and divinyl compounds such as divinylbenzene. Copolymer A may have one or more polyfunctional ethylenically unsaturated monomer units. Copolymer A may have a structural unit derived from at least one selected from the group consisting of allyl methacrylate, ethylene glycol dimethacrylate, and divinylbenzene as the polyfunctional ethylenically unsaturated monomer.

[0027] In addition to the monomers described above, copolymer A may have a structural unit derived from any monomer commonly used in emulsion polymerization such as ethylene, propylene, vinyl acetate, vinyl propionate, vinyl chloride, and vinylidene chloride.

[0028] For the polymerization of copolymer A, known emulsifiers and surfactants can be used. Examples of surfactants include anionic surfactants such as sulfate salts of higher alcohols, alkylbenzene sulfonates (e.g., sodium dodecylbenzene sulfonate), alkyl diphenyl ether disulfonate salts (e.g., sodium alkyl diphenyl ether disulfonate), aliphatic sulfonate salts, aliphatic carboxylate salts, dehydroabietic acid salts, formalin condensates of naphthalene sulfonic acid, and sulfate salts of nonionic surfactants; nonionic surfactants such as alkyl ester type of polyethylene glycol, alkyl phenyl ether type (e.g., polyoxyethylene lauryl ether), and alkyl ether type. The emulsifier and surfactant may be used alone or in combination of two or more.

[0029] For the polymerization of copolymer A, known chain transfer agents can be used. Examples of chain transfer agents include alkyl mercaptan compounds such as n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, and n-stearyl mercaptan; xanthate compounds such as dimethyl xanthate disulfide and diisopropyl xanthate disulfide; thiuram compounds such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, and tetramethylthiuram monosulfide; phenolic compounds such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; allyl compounds such as allyl alcohol; halogenated hydrocarbon compounds such as dichloromethane, dibromomethane, and carbon tetrabromide; vinyl ethers such as α-benzyloxystyrene, α-benzyloxyacrylonitrile, and α-benzyloxyacrylamide; triphenylethane, pentaphenylethane, acrolein, methacrolein, thioglycolic acid, thiomalic acid, 2-ethylhexyl thioglycolate, terpinolene, and α-methylstyrene dimer. These may be used alone or in combination of two or more.

[0030] For the polymerization of copolymer A, known polymerization initiators can be used. Examples of the polymerization initiator include water-soluble polymerization initiators such as lithium persulfate, potassium persulfate, sodium persulfate, ammonium persulfate, etc.; oil-soluble polymerization initiators such as cumene hydroperoxide, benzoyl peroxide, t-butyl hydroperoxide, acetyl peroxide, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, etc. The polymerization initiator is preferably at least one selected from the group consisting of potassium persulfate, sodium persulfate, cumene hydroperoxide, and t-butyl hydroperoxide. The amount of the polymerization initiator used is not particularly limited and can be appropriately adjusted in consideration of the composition of the monomer, the pH of the polymerization reaction system, and the combination with other additives.

[0031] For the polymerization of copolymer A, known reducing agents can be used. Examples of the reducing agent include reducing sugars such as dextrose, sucrose, etc.; amines such as dimethylaniline, triethanolamine, etc.; carboxylic acids such as L-ascorbic acid, erythorbic acid, tartaric acid, citric acid, etc. and their salts; sulfites, bisulfites, pyrosulfites, dithionites, thionates, thiosulfates, formaldehyde sulfonates, and benzaldehyde sulfonates. The reducing agent is preferably L-ascorbic acid or erythorbic acid. The amount of the reducing agent used can be appropriately adjusted in consideration of the composition of the monomer, the pH of the polymerization reaction system, and the combination with other additives.

[0032] For the polymerization of copolymer A, water and known organic solvents can be used. As the organic solvent, for example, hydrocarbon compounds such as saturated hydrocarbons like pentane, hexane, heptane, octane, cyclohexane, cycloheptane; unsaturated hydrocarbons like pentene, hexene, heptene, cyclopentene, cyclohexene, cycloheptene, 4-methylcyclohexene, 1-methylcyclohexene; aromatic hydrocarbons like benzene, toluene, xylene can be used. The organic solvent preferably has a moderately low boiling point, can be recovered and reused easily by steam distillation or the like after the polymerization, and from the viewpoint of environmental protection, is cyclohexene or toluene.

[0033] For the polymerization of copolymer A, known additives such as an oxygen scavenger, a chelating agent, a dispersant, an antifoaming agent, an antioxidant, a preservative, an antibacterial agent, a flame retardant, an ultraviolet absorber can be used as necessary. These additives are not particularly limited in terms of type and amount used, and can be used as appropriate.

[0034] As a method of adding components other than the monomer components such as the above-mentioned monomer components and additives to the reaction system during the polymerization of copolymer A, for example, a batch addition method, a divided addition method, a continuous addition method, and a power feed method can be mentioned.

[0035] Copolymer A can be obtained by polymerizing the above-mentioned monomers by known polymerization methods such as emulsion polymerization, suspension polymerization, solution polymerization, bulk polymerization.

[0036] The temperature of the polymerization reaction varies depending on the type of monomer components used, etc., but may be, for example, 40 to 150°C. The reaction time of the polymerization reaction may be, for example, 5 to 15 hours.

[0037] The polymerization of copolymer A is preferably terminated by confirming that the polymer conversion rate at the end of the polymerization reaction of the monomer components added to the reaction system exceeds 97%. That is, the polymer conversion rate at the end of the polymerization reaction of copolymer A is preferably more than 97%. The polymer conversion rate can be calculated from the mass of the solid content in the reaction system or the amount of heat cooled in the tank of the polymerization reactor.

[0038] To terminate the polymerization reaction, a polymerization terminator may be used. After the completion of the polymerization reaction, unreacted monomer components and the like may be removed by distillation or the like.

[0039] The glass transition temperature, gel content, and number average particle diameter of the copolymer latex are not particularly limited, but from the viewpoint of the polymerization stability of the copolymer latex and the like, they are preferably in the following ranges. The glass transition temperature of the copolymer latex is preferably -40 to 60°C, more preferably -35 to 30°C. The number average particle diameter of the copolymer latex is preferably 50 to 300 nm, more preferably 70 to 250 nm. The gel content of the copolymer latex is preferably 20 to 95% by mass. The glass transition temperature, gel content, and number average particle diameter of the copolymer latex can be adjusted by appropriately adjusting the types, amounts used, and addition methods of emulsifiers, polymerization initiators, chain transfer agents, etc. used during the polymerization of the copolymer latex, as well as the proportion of water, etc. The glass transition temperature, gel content, and number average particle diameter of the copolymer latex can be measured by the methods described in the examples below, respectively.

[0040] It is preferable that the unreacted monomer components and other low-boiling components are removed from the copolymer latex by methods such as heating under reduced pressure distillation and steam distillation.

[0041] From the viewpoints of dispersion stability and coating property on the active material, the pH of the copolymer latex may be adjusted by adding a pH adjuster such as ammonia, potassium hydroxide, or sodium hydroxide. The pH of the copolymer latex is preferably 5 to 9, more preferably 5.5 to 8.5.

[0042] [Composition for carbon dioxide separation membrane] The above-mentioned copolymer latex can be used as a composition for a carbon dioxide separation membrane (hereinafter, also referred to as "Composition B"). That is, another embodiment of the present invention is a composition for a carbon dioxide separation membrane containing the above-mentioned copolymer latex. Composition B contains at least copolymer A. The content of copolymer A in Composition B may be, for example, 80% by mass or more, 85% by mass or more, 90% by mass or more, 93% by mass or more, or 95% by mass or more.

[0043] Composition B preferably further contains zinc oxide in addition to the copolymer latex. When Composition B further contains zinc oxide, it becomes easier to obtain a carbon dioxide separation membrane having excellent carbon dioxide selective permeability, sufficient carbon dioxide permeability, and strength.

[0044] The content of zinc oxide is preferably 0.5 part by mass or more, and may be 0.8 part by mass or more, or 1 part by mass or more, based on 100 parts by weight (on a solid content basis) of the copolymer latex. The content of zinc oxide is preferably 3 parts by mass or less, and may be 5 parts by mass or less, 4 parts by mass or less, 3 parts by mass or less, 2.5 parts by mass or less, 2 parts by mass or less, 1.8 parts by mass or less, or 1.5 parts by mass or less, based on 100 parts by weight (on a solid content basis) of the copolymer latex.

[0045] Composition B may further contain a rubber latex such as natural rubber latex or isoprene rubber latex. That is, the above-mentioned copolymer latex may be mixed with other latexes according to the purpose of use.

[0046] Composition B may further contain a pH adjuster (such as potassium hydroxide, sodium hydroxide, aqueous ammonia, etc.), a vulcanizing agent (such as colloidal sulfur, thiuram disulfide, etc.), a vulcanization accelerator (such as dialkyldithiocarbamate, xanthate, etc.), a vulcanization accelerator aid (such as litharge (PbO), red lead (Pb3O4), magnesium oxide, etc.), an antioxidant (such as styrenated phenol, imidazoles, paraphenylenediamine, etc.), a colorant (such as titanium dioxide, fast yellow, phthalocyanine blue, ultramarine, etc.).

[0047] [Carbon dioxide separation membrane] A carbon dioxide separation membrane can be formed from the composition for a carbon dioxide separation membrane described above. The carbon dioxide separation membrane contains at least copolymer A. That is, another embodiment of the present invention is a carbon dioxide separation membrane containing a copolymer having an aliphatic conjugated diene monomer unit, and the content of the aliphatic conjugated diene monomer unit in the copolymer is 10 to 80% by mass.

[0048] In addition to copolymer A, the carbon dioxide separation membrane may contain components that composition B can contain (for example, zinc oxide, latex other than the above-described copolymer latex). By containing zinc oxide, the carbon dioxide separation membrane can more easily achieve more excellent carbon dioxide selective permeability, carbon dioxide permeability, and strength.

[0049] The carbon dioxide permeability of the carbon dioxide separation membrane is 10×10 11 cm 3 ·cm / cm 2 ·s·cmHg or more, 30×10 11 cm 3 ·cm / cm 2 ·s·cmHg or more, 60×10 11 cm 3 ·cm / cm 2 ·s·cmHg or more, 100×10 11 cm 3 ·cm / cm 2 ·s·cmHg or more, 150×10 11 cm 3 ·cm / cm 2·s·cmHg or more, 200×10 11 cm 3 ·cm / cm 2 ·s·cmHg or more, 250×10 11 cm 3 ·cm / cm 2 ·s·cmHg or more, or 300×10 11 cm 3 ·cm / cm 2 ·s·cmHg or more may be sufficient. The carbon dioxide permeability of the carbon dioxide separation membrane is, for example, 500×10 11 cm 3 ·cm / cm 2 ·s·cmHg or less may be sufficient. The carbon dioxide permeability of the carbon dioxide separation membrane can be measured by the method described in the examples below.

[0050] The nitrogen permeability of the carbon dioxide separation membrane is, for example, 12×10 11 cm 3 ·cm / cm 2 ·s·cmHg or less, 9×10 11 cm 3 ·cm / cm 2 ·s·cmHg or less, 6×10 11 cm 3 ·cm / cm 2 ·s·cmHg or less, 3×10 11 cm 3 ·cm / cm 2 ·s·cmHg or less, or 1.5×10 11 cm 3 ·cm / cm 2 ·s·cmHg or more may be sufficient. The nitrogen permeability of the carbon dioxide separation membrane is, for example, 0.1×10 11 cm 3 ·cm / cm 2 ·s·cmHg or more may be sufficient. The nitrogen permeability of the carbon dioxide separation membrane can be measured by the method described in the examples below.

[0051] The carbon dioxide selective permeability (carbon dioxide permeability / nitrogen permeability) of the carbon dioxide separation membrane may be 25 or more, 30 or more, or 34 or more from the viewpoint of more excellent carbon dioxide selective permeability. The carbon dioxide selective permeability (carbon dioxide permeability / nitrogen permeability) of the carbon dioxide separation membrane may be, for example, 50 or less.

[0052] The stress at 100% elongation of the carbon dioxide separation membrane may be 10 MPa or less, 8 MPa or less, 5 MPa or less, or 3 MPa or less from the viewpoint of more excellent flexibility. The stress at 100% elongation of the carbon dioxide separation membrane may be, for example, 1.0 MPa or more. The stress at 100% elongation of the carbon dioxide separation membrane can be measured by the method described in the examples below.

[0053] The breaking stress of the carbon dioxide separation membrane may be 5 MPa or more, 10 MPa or more, 15 MPa or more, 20 MPa or more, or 25 MPa or more from the viewpoint of more excellent strength. The breaking stress of the carbon dioxide separation membrane may be, for example, 50 MPa or less. The breaking stress of the carbon dioxide separation membrane can be measured by the method described in the examples below.

[0054] The thickness of the carbon dioxide separation membrane may be, for example, 5 μm or more, 50 μm or more, or 100 μm or more, and may also be 1000 μm or less, 500 μm or less, or 300 μm or less.

[0055] The carbon dioxide separation membrane can be produced, for example, by a method including a step of coagulating the above-described composition for a carbon dioxide separation membrane by a salt coagulation method. That is, another embodiment of the present invention includes a step of coagulating a composition for a carbon dioxide separation membrane by a salt coagulation method, the composition for a carbon dioxide separation membrane contains a copolymer having an aliphatic conjugated diene monomer unit, and the content of the aliphatic conjugated diene monomer unit in the copolymer is 10 to 80% by mass, which is a method for producing a carbon dioxide separation membrane.

[0056] A method for solidifying Composition B by the salt coagulation method will be described. First, a coagulating liquid is applied to the surface of a substrate. The coagulating liquid is a metal salt (coagulant) such as calcium salts like calcium chloride, calcium nitrate, calcium acetate; magnesium salts like magnesium chloride, etc., dissolved in water or a hydrophilic organic solvent such as alcohol or ketone. The concentration of the metal salt in the coagulating liquid may be 5 to 50% by mass, preferably 10 to 30% by mass. The coagulating liquid may contain surfactants such as nonionic surfactants and anionic surfactants; fillers such as calcium carbonate, talc, and silica gel, if necessary.

[0057] After applying the coagulating liquid to the substrate and drying it, a coating film containing a coagulant is formed on the surface of the substrate. Next, the composition for carbon dioxide separation membrane is applied to the coating film containing the coagulant. At this time, the coagulant reacts with the copolymer latex, and a film is formed on the surface of the substrate. After removing the excess composition for carbon dioxide separation membrane that did not react with the coagulant, the film formed on the surface of the substrate is washed with water and dried, and then the film is peeled off from the surface of the substrate to obtain a carbon dioxide separation membrane.

[0058] The carbon dioxide separation membrane can be produced, for example, by a method including the step of drying the above-described composition for carbon dioxide separation membrane. That is, another embodiment of the present invention is a method for producing a carbon dioxide separation membrane, which includes the step of drying a composition for carbon dioxide separation membrane, the composition for carbon dioxide separation membrane contains a copolymer having an aliphatic conjugated diene monomer unit, and the content of the aliphatic conjugated diene monomer unit in the copolymer is 10 to 80% by mass.

[0059] As a method for drying the composition for carbon dioxide separation membrane, for example, after applying the composition for carbon dioxide separation membrane to a substrate (for example, a glass substrate), it may be left at room temperature (20 to 25°C) for 24 hours or more. From the viewpoint of shortening the drying time, the carbon dioxide separation membrane may be heated and dried. After drying, the carbon dioxide separation membrane can be obtained by peeling off the film formed on the substrate.

Examples

[0060] Hereinafter, the present invention will be described more specifically by way of examples. However, the present invention is not limited to the following examples.

[0061] <Preparation of copolymer latex 1 (Polymerization Example 1)> Into a pressure-resistant polymerization reactor, 90 parts by mass of pure water as a solvent, 0.6 parts by mass of sodium dodecylbenzenesulfonate as a surfactant, and 0.6 parts by mass of potassium persulfate as a polymerization initiator were added and stirred. Next, the monomer components (unit: parts by mass) and other compounds (unit: parts by mass) shown in Table 1 were added to the polymerization reactor. After the temperature was raised to 70 °C (polymerization temperature), polymerization was carried out for 8 hours (polymerization time). After confirming that the polymer conversion rate of the added monomer components exceeded 97%, a polymerization terminator was added to terminate the polymerization, and the temperature inside the tank of the polymerization reactor was cooled until it reached 35 °C or lower. Next, 0.4 parts by mass (solid content) of an aqueous sodium hydroxide solution was added as a pH adjuster and held for 30 minutes. Then, unreacted monomer components and the like were removed by heating under reduced pressure distillation to obtain copolymer latex 1 (Polymerization Example 1).

[0062] <Preparation of copolymer latexes 2 to 13 (Polymerization Examples 2 to 13)> Copolymer latexes were obtained in the same manner as copolymer latex 1 (Polymerization Example 1), except that the components (unit: parts by mass) used in the polymerization and the polymerization conditions were changed to the conditions shown in Table 1.

[0063]

Table 1

[0064] <Measurement of glass transition temperature> Each of the prepared copolymer latexes was applied to a glass plate at about 0.5 g, and dried at 70 °C for 4 hours to prepare a film. The film was set in an aluminum pan for DSC test, and a DSC curve was obtained using a differential scanning calorimeter (DSC6200, manufactured by Seiko Instruments Inc.) at a measurement temperature of -100 to 100 °C and a heating rate of 10 °C / min. The starting point of the endotherm of the phase change was read from the peak of the obtained DSC curve, and the glass transition temperature (°C) of the copolymer latex was determined. When two or more phase changes were confirmed, the starting point of the endotherm with the lowest temperature was taken as the glass transition temperature. The measurement results are shown in Table 1.

[0065] <Measurement of Gel Content (Toluene Insoluble Content)> Using each of the prepared copolymer latexes, a film was prepared in an atmosphere at a temperature of 80 °C and a humidity of 85%. The prepared film was weighed at about 1 g (weight value: X (g)), placed in 400 mL of toluene, left for 48 hours, and swollen and dissolved. Then, it was filtered through a 300-mesh wire mesh, and the toluene insoluble content trapped by the wire mesh was dried and then weighed (weight value: Y (g)). The gel content was calculated from the percentage of the weight value Y of the toluene insoluble content to the weight value X of the prepared film. The measurement results are shown in Table 1. Gel content (mass%) = (Y / X) × 100

[0066] <Measurement of Number Average Particle Diameter> The number average particle diameter (μm) of each of the prepared copolymer latexes was measured by the dynamic light scattering method using the photon correlation method. The measurement of the number average particle diameter was performed using FPAR-1000 (manufactured by Otsuka Electronics Co., Ltd.). The measurement results are shown in Table 1.

[0067] <Preparation of Composition for Carbon Dioxide Separation Membrane> (Examples 1 to 10, Comparative Examples 1 to 2) The following components were added to each of the prepared copolymer latexes to obtain a composition for carbon dioxide separation membrane (solid content concentration: 32 mass%). <Composition for Carbon Dioxide Separation Membrane> (Solid Content Amount) Copolymer latex 100.0 parts by mass Zinc oxide 1.5 parts by mass 0.6 parts by mass of colloidal sulfur 0.6 parts by mass of zinc diethyldithiocarbamate 1.5 parts by mass of titanium dioxide 0.7 parts by mass of potassium hydroxide

[0068] (Examples 11 to 14) A carbon dioxide separation membrane composition was obtained in the same manner as in Examples 1 to 10, except that the type of the copolymer latex used and the amount of zinc oxide compounded with respect to 100 parts by mass of the copolymer latex were changed to the conditions shown in Table 2.

[0069] (Preparation of carbon dioxide separation membrane (salt coagulation method)) (Examples 1 to 14, Comparative Examples 1 to 2) An aqueous calcium nitrate solution with a concentration of 15% by mass was prepared as a coagulation liquid, and it was applied to the surface of a coated paperboard (substrate) using a Wirebar #12 and dried in a hot air circulation dryer at 120°C for 1 minute. A box-shaped substrate was formed with the surface of the substrate coated with the coagulation liquid on the inside. A sufficient amount of the carbon dioxide separation membrane composition was cast onto this box-shaped substrate and allowed to stand for 30 seconds. After removing the uncoagulated composition, it was allowed to stand for an additional 40 seconds to form a film on the side of the box-shaped substrate coated with the coagulation liquid. Next, a sufficient amount of warm water at 45°C was cast onto the box-shaped substrate with the film formed thereon, and it was washed with warm water for 60 seconds. The film formed on the box-shaped substrate was dried at room temperature for 2 hours and then heat-treated at 120°C for 15 minutes. Then, the dried film was peeled off from the substrate to obtain a carbon dioxide separation membrane with a thickness of about 100 μm.

[0070] (Preparation of carbon dioxide separation membrane (drying method)) (Examples 15 to 20) An aqueous solution of 2% by mass of carboxymethyl cellulose (Cellogen EP, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was added to 100 parts by mass of the carbon dioxide separation membrane composition so that the solid content was 2 parts by mass to obtain a coating solution. The obtained coating solution was applied onto a glass plate using an applicator with a clearance of 500 μm, dried at room temperature for 24 hours, and then heat-treated at 120°C for 15 minutes. Then, the dried film was peeled off from the glass plate to obtain a carbon dioxide separation membrane with a thickness of about 100 μm.

[0071] <Measurement of Gas Permeability> The gas permeabilities of carbon dioxide single gas and nitrogen single gas of each prepared carbon dioxide separation membrane were measured under the following measurement conditions, respectively. The measurement results are shown in Table 2. Measuring instrument: Gas Permeability Measuring Device GTR-10XACT (manufactured by GTR Tech Co., Ltd.) Detector: Gas Chromatograph G2700 (manufactured by Yanaco Technical Science Co., Ltd.) Measurement temperature: 22 °C Measurement area: 15.2 cm 2 Sample gas pressure: 76 cmHg

[0072] <Calculation of Carbon Dioxide Selective Permeability> Using the above measurement results of gas permeability, the carbon dioxide selective permeability was calculated from the following formula. The measurement results are shown in Table 2. Carbon dioxide selective permeability = (Gas permeability of carbon dioxide) / (Gas permeability of nitrogen)

[0073] <Evaluation of Strength and Flexibility> According to JIS K6251, a tensile test was performed on each prepared carbon dioxide separation membrane, and the stress at 100% elongation and the stress at break were measured. The measurement results are shown in Table 2.

[0074]

Table 2

Industrial Applicability

[0075] As described above, by using a copolymer latex for a carbon dioxide separation membrane containing a copolymer having an aliphatic conjugated diene monomer unit and having a content of the aliphatic conjugated diene monomer unit in the copolymer of 10 to 80% by mass, a carbon dioxide separation membrane having excellent carbon dioxide selective permeability and sufficient carbon dioxide permeability and having excellent strength and flexibility can be obtained.

[0076] The carbon dioxide separation membrane described above can be suitably used, for example, in an air conditioning (ventilation) system. Places where an air conditioning (ventilation) system using a carbon dioxide separation membrane is installed include buildings such as ordinary homes and office buildings; and transportation equipment such as automobiles, trains, aircraft, and ships. The carbon dioxide separation membrane according to one embodiment of the present invention has excellent strength and flexibility, so it can be formed even in a complex shape. In addition, the carbon dioxide separation membrane according to one embodiment of the present invention has excellent carbon dioxide selective permeability and sufficient carbon dioxide permeability, so it can be suitably used for an air conditioning (ventilation) system installed in a narrow space (for example, transportation equipment such as automobiles).

[0077] In addition, since humans take in oxygen from the air by breathing and exhale air containing a lot of carbon dioxide, the carbon dioxide concentration increases in a closed space. In particular, the narrower the space and the higher the density of people, the more likely the carbon dioxide concentration is to increase significantly. It is known that an increase in carbon dioxide concentration has an effect on the human body, such as increasing fatigue, decreasing attention, and inducing drowsiness. The carbon dioxide concentration can be reduced by introducing outside air through ventilation, but when cooling or heating is performed, a comfortable room temperature cannot be maintained by ventilation, so a lot of energy needs to be consumed to return the room temperature to a comfortable temperature, resulting in low energy efficiency. On the other hand, according to an air conditioning (ventilation) system using a carbon dioxide separation membrane according to one embodiment of the present invention, the carbon dioxide concentration can be reduced without introducing outside air into the room, so that the energy consumption of cooling and heating can be suppressed and energy efficiency can be improved.

Claims

[

1. ] A copolymer latex for a carbon dioxide separation membrane having a carbon dioxide selective permeability (carbon dioxide permeability / nitrogen permeability) of 25 or more, comprising only an aliphatic conjugated diene monomer unit and at least one selected from the group consisting of a vinyl cyanide monomer unit, an aromatic vinyl monomer unit, and an unsaturated carboxylic acid alkyl ester monomer unit, and a hydroxyalkyl group-containing unsaturated monomer unit, an ethylenically unsaturated carboxylic acid monomer unit, and at least one selected from the group consisting of a polyfunctional ethylenically unsaturated monomer unit containing two or more unsaturated double bonds (however, excluding copolymers of styrene and butadiene, ABS resins, and brominated styrene-butadiene copolymers), wherein the content of the aliphatic conjugated diene monomer unit in the copolymer is 10 to 80% by mass, the content of the hydroxyalkyl group-containing unsaturated monomer unit is 10% by mass or less, the content of the ethylenically unsaturated carboxylic acid monomer unit is 10% by mass or less, and the content of the polyfunctional ethylenically unsaturated monomer unit containing two or more unsaturated double bonds is 0.3% by mass or less, a copolymer latex for a carbon dioxide separation membrane. [

2. ] The copolymer further having an ethylenically unsaturated carboxylic acid monomer unit, The copolymer latex for a carbon dioxide separation membrane according to claim 1, wherein the content of the ethylenically unsaturated carboxylic acid monomer unit in the copolymer is 0.1 to 10% by mass. [

3. ] A composition for a carbon dioxide separation membrane, containing the copolymer latex for a carbon dioxide separation membrane according to claim 1 or 2. [

4. ] The composition for a carbon dioxide separation membrane according to claim 3, further containing zinc oxide. [

5. ] comprising only an aliphatic conjugated diene monomer unit and at least one selected from the group consisting of a vinyl cyanide monomer unit, an aromatic vinyl monomer unit, and an unsaturated carboxylic acid alkyl ester monomer unit, and a hydroxyalkyl group-containing unsaturated monomer unit, an ethylenically unsaturated carboxylic acid monomer unit, and at least one selected from the group consisting of a polyfunctional ethylenically unsaturated monomer unit containing two or more unsaturated double bonds (however, excluding copolymers of styrene and butadiene, ABS resins, and brominated styrene-butadiene copolymers), The content of the aliphatic conjugated diene monomer unit in the copolymer is 10 to 80% by mass, the content of the unsaturated monomer unit containing a hydroxyalkyl group is 10% by mass or less, the content of the ethylenically unsaturated carboxylic acid monomer unit is 10% by mass or less, and the content of the polyfunctional ethylenically unsaturated monomer unit containing two or more unsaturated double bonds is 0.3% by mass or less. A carbon dioxide separation membrane having a carbon dioxide selective permeability (carbon dioxide permeability / nitrogen permeability) of 25 or more.

6. A method for producing a carbon dioxide separation membrane, comprising a step of coagulating a composition for a carbon dioxide separation membrane by a salt coagulation method, wherein the composition for a carbon dioxide separation membrane contains a copolymer (excluding copolymers of styrene and butadiene, ABS resins, and brominated styrene-butadiene copolymers) consisting only of an aliphatic conjugated diene monomer unit and at least one selected from the group consisting of a vinyl cyanide monomer unit, an aromatic vinyl monomer unit, and an unsaturated carboxylic acid alkyl ester monomer unit, and at least one selected from the group consisting of an unsaturated monomer unit containing a hydroxyalkyl group, an ethylenically unsaturated carboxylic acid monomer unit, and a polyfunctional ethylenically unsaturated monomer unit containing two or more unsaturated double bonds, the content of the aliphatic conjugated diene monomer unit in the copolymer is 10 to 80% by mass, the content of the unsaturated monomer unit containing a hydroxyalkyl group is 10% by mass or less, the content of the ethylenically unsaturated carboxylic acid monomer unit is 10% by mass or less, and the content of the polyfunctional ethylenically unsaturated monomer unit containing two or more unsaturated double bonds is 0.3% by mass or less. A method wherein the carbon dioxide selective permeability (carbon dioxide permeability / nitrogen permeability) of the carbon dioxide separation membrane is 25 or more.

Images