Method for producing aqueous amphiphilic polymer solution

Abstract

To provide a method for producing an amphiphilic polymer aqueous solution which can suppress foaming when an organic solvent is distilled off from an amphiphilic polymer solution.SOLUTION: There is provided a method for producing an amphiphilic polymer aqueous solution, which comprises: a first step of polymerizing a monomer composition containing a vinyl monomer having an acid group and a vinyl monomer having no acid group in an organic solvent to prepare a polymer-containing solution containing a polymer (X) having an acid value of 30 mg KOH / g to 250 mg KOH / g; a second step of adding water to the polymer-containing solution to precipitate at least a portion of the polymer to prepare a polymer dispersion; a third step of distilling off an organic solvent from the polymer dispersion solution to prepare a polymer aqueous dispersion; and a fourth step of adding a basic component to the polymer aqueous dispersion to neutralize an acidic group possessed by the polymer (X).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing an aqueous solution of an amphiphilic polymer. [Background technology]

[0002] The recording method using an inkjet printer involves generating ink droplets from a fine nozzle, ejecting them onto a recording material such as paper, film, or fabric, and then depositing the ink onto the material. This method is quiet and produces little noise because there is no direct contact between the recording head and the recording material. In addition, because it is easy to make the printer smaller and faster, it has rapidly spread not only to industrial use but also to home use, and significant growth is expected in the future.

[0003] Ink (coloring composition) used in inkjet printers is composed of a colorant, a dispersion medium, and additives such as surfactants that are blended as needed. Two types of colorants are known for use in inkjet inks: water-soluble dyes and colorants that are substantially water-insoluble, such as pigments, disperse dyes, and oil-soluble dyes. Images recorded using water-insoluble colorants among these have excellent fastness to light, ozone, water, and the like. Meanwhile, water-based inks are in demand for inkjet inks due to environmental considerations, and water-based inks using water-insoluble colorants are widely used.

[0004] Because water-based inks contain water as a solvent, amphipathic dispersants are used to disperse water-insoluble colorants. For example, Patent Document 1 describes, as examples of such amphipathic dispersants, a neutralized product obtained by polymerizing a hydrophilic monomer having an acidic group and a hydrophobic monomer, and neutralizing the copolymer with an alkali, as well as an aqueous solution of this neutralized product (Patent Document 1).

[0005] Here, amphiphilic polymers are usually produced by polymerizing monomers in a hydrophilic organic solvent and then adding an alkaline aqueous solution to neutralize the acidic groups of the polymer. One method for obtaining an aqueous solution of an amphiphilic polymer involves precipitating and filtering the neutralized polymer from the reaction solution and redissolving the polymer in water, but this method places a heavy burden on the production process. Therefore, a method for replacing the hydrophilic organic solvent with water in a reaction solution containing a neutralized polymer (amphiphilic polymer) has been sought. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-98835 Summary of the Invention [Problem to be solved by the invention]

[0007] One method for replacing the hydrophilic organic solvent in a solution containing an amphiphilic polymer and a hydrophilic organic solvent with water is to distill off the hydrophilic organic solvent. However, since the amphiphilic polymer has a surfactant effect, the solution tends to foam when it contains water, and the solution foams when stimulated by stirring, decompression treatment, etc., making it difficult to distill off the hydrophilic organic solvent.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing an aqueous amphiphilic polymer solution that can suppress foaming when an organic solvent is distilled off from the amphiphilic polymer solution. [Means for solving the problem]

[0009] The method for producing an amphipathic polymer aqueous solution of the present invention, which has been able to solve the above-mentioned problems, is characterized by comprising: a first step of polymerizing a monomer composition containing a vinyl monomer having an acidic group and a vinyl monomer not having an acidic group in an organic solvent to prepare a polymer-containing solution containing a polymer (X) having an acid value of 30 mgKOH / g to 250 mgKOH / g; a second step of adding water to the polymer-containing solution to precipitate at least a portion of the polymer, thereby preparing a polymer dispersion; a third step of distilling off the organic solvent from the polymer dispersion to prepare an aqueous polymer dispersion; and a fourth step of adding a basic component to the aqueous polymer dispersion to neutralize the acidic groups of the polymer (X).

[0010] In the method for producing an amphiphilic polymer aqueous solution of the present invention, the polymer (X) obtained by polymerization is precipitated in an unneutralized or low-neutralized state to form a polymer dispersion, and the hydrophilic organic solvent in this polymer dispersion state is replaced with water. By precipitating the polymer component, foaming during distillation of the hydrophilic organic solvent can be suppressed, and the hydrophilic organic solvent can be removed efficiently. [Effects of the Invention]

[0011] According to the present invention, foaming can be suppressed when a hydrophilic organic solvent in a polymer-containing solution is replaced with water, and the hydrophilic organic solvent can be efficiently removed, thereby increasing the productivity of the amphiphilic polymer aqueous solution. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a photograph substituted for a drawing showing the results of foaming evaluation. DETAILED DESCRIPTION OF THE INVENTION

[0013] The method for producing an amphiphilic polymer aqueous solution of the present invention is characterized by comprising: a first step of polymerizing a monomer composition containing a vinyl monomer having an acidic group and a vinyl monomer not having an acidic group in an organic solvent to prepare a polymer-containing solution containing a polymer (X) having an acid value of 30 mgKOH / g to 250 mgKOH / g; a second step of adding water to the polymer-containing solution to precipitate at least a portion of the polymer to prepare a polymer dispersion; a third step of distilling off the organic solvent from the polymer dispersion to prepare an aqueous polymer dispersion; and a fourth step of adding a basic component to the aqueous polymer dispersion to neutralize the acidic groups of the polymer (X).

[0014] In the present invention, "vinyl monomer" refers to a monomer having a radically polymerizable carbon-carbon double bond in the molecule. "Structural unit derived from a vinyl monomer" refers to a structural unit in which the radically polymerizable carbon-carbon double bond of a vinyl monomer is polymerized to form a carbon-carbon single bond. "(Meth)acrylic" refers to "at least one of acrylic and methacrylic." "(Meth)acrylate" refers to "at least one of acrylate and methacrylate." "(Meth)acryloyl" refers to "at least one of acryloyl and methacryloyl." In the present invention, "A block" can be rephrased as "A segment," and "B block" can be rephrased as "B segment."

[0015] <1st process> In the first step, a monomer composition containing a vinyl monomer having an acidic group and a vinyl monomer having no acidic group is polymerized in an organic solvent to prepare a polymer-containing solution containing a polymer (X).

[0016] (Vinyl monomer having an acidic group) Examples of the acidic group contained in the vinyl monomer having an acidic group include a carboxyl group (-COOH), a sulfonic acid group (-SO3H), a phosphoric acid group (-OPO3H2), a phosphonic acid group (-PO3H2), and a phosphinic acid group (-PO2H2). The vinyl monomer having an acidic group is preferably at least one selected from the group consisting of a vinyl monomer having a carboxyl group, a vinyl monomer having a sulfonic acid group, and a vinyl monomer having a phosphoric acid group.

[0017] Examples of the vinyl monomer having an acidic group include (meth)acrylic acid and (meth)acrylate having an acidic group.

[0018] Examples of the (meth)acrylate having an acidic group include (meth)acrylates having a carboxy group such as a monomer obtained by reacting a hydroxyalkyl (meth)acrylate with an acid anhydride such as maleic anhydride, succinic anhydride, or phthalic anhydride (for example, 2-acryloyloxyethyl hydrogen succinate, 2-methacryloyloxyethyl hydrogen succinate, 2-(acryloyloxy)ethyl hydrogen hexahydrophthalate, 2-(methacryloyloxyethyl) hydrogen hexahydrophthalate, 1-(2-acryloyloxyethyl) phthalate, and 1-(2-methacryloyloxyethyl) phthalate); (meth)acrylates having a sulfonic acid group such as ethyl sulfonate (meth)acrylate; and (meth)acrylates having a phosphoric acid group such as 2-(phosphonooxy)ethyl (meth)acrylate.

[0019] The vinyl monomer having an acidic group may be used alone or in combination of two or more thereof. The vinyl monomer having an acidic group is preferably (meth)acrylic acid and / or a (meth)acrylate having a carboxy group, more preferably (meth)acrylic acid.

[0020] (Vinyl monomer without acidic group) Examples of the vinyl monomer having no acidic group include (meth)acrylic vinyl monomers having no acidic group, α-olefins, aromatic vinyl monomers, heterocycle-containing unsaturated monomers, vinylamides, vinyl carboxylates, dienes, and the like, and one or more of these may be used in combination.

[0021] Examples of the (meth)acrylic vinyl monomer that does not have an acidic group include (meth)acrylates having a chain alkyl group (a linear alkyl group or a branched alkyl group), (meth)acrylates having a cyclic alkyl group, (meth)acrylates having a polycyclic structure, (meth)acrylates having an aromatic group, (meth)acrylates having a polyalkylene glycol structural unit, (meth)acrylates having a hydroxy group, (meth)acrylates having a lactone-modified hydroxy group, (meth)acrylates having an alkoxy group, and (meth)acrylates having an oxygen-containing heterocyclic group.

[0022] The (meth)acrylate having a linear alkyl group is preferably a (meth)acrylate having a linear alkyl group with a carbon number of 1 to 20, and more preferably a (meth)acrylate having a linear alkyl group with a carbon number of 1 to 10. Examples of the (meth)acrylate having a linear alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, n-lauryl (meth)acrylate, and n-stearyl (meth)acrylate.

[0023] The (meth)acrylate having a branched chain alkyl group is preferably a (meth)acrylate having a branched chain alkyl group with a carbon number of 3 to 20, and more preferably a (meth)acrylate having a branched chain alkyl group with a carbon number of 3 to 10. Examples of the (meth)acrylate having a branched chain alkyl group include isopropyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isononyl (meth)acrylate, and isodecyl (meth)acrylate.

[0024] The (meth)acrylate having a cyclic alkyl group is preferably a (meth)acrylate having a cyclic alkyl group with a carbon number of 6 to 12. Examples of the cyclic alkyl group include a cyclic alkyl group having a monocyclic structure (for example, a cycloalkyl group). Specific examples of the (meth)acrylate having a cyclic alkyl group with a monocyclic structure include cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, and cyclododecyl (meth)acrylate.

[0025] The (meth)acrylate having a polycyclic structure is preferably a (meth)acrylate having a polycyclic structure with 6 to 12 carbon atoms in the polycyclic structure. Examples of the polycyclic structure include cyclic alkyl groups having a bridged ring structure (e.g., adamantyl group, norbornyl group, isobornyl group). Specific examples of the (meth)acrylate having a polycyclic structure include isobornyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, 2-ethyl-2-adamantyl (meth)acrylate, etc.

[0026] The (meth)acrylate having an aromatic group is preferably a (meth)acrylate having an aromatic group with 6 to 12 carbon atoms. Examples of the aromatic group include an aryl group, an alkylaryl group, an aralkyl group, an aryloxy group, an aryloxyalkyl group, an alkylaryloxy group, and an aralkyloxy group, and particularly preferred are a phenyl group, a benzyl group, a tolyl group, and a phenoxyethyl group. Specific examples of the (meth)acrylate having an aromatic group include benzyl (meth)acrylate, phenyl (meth)acrylate, and phenoxyethyl (meth)acrylate.

[0027] Examples of the (meth)acrylate having a polyalkylene glycol structural unit include (meth)acrylates having a polyethylene glycol structural unit such as polyethylene glycol (degree of polymerization = 2 to 10) methyl ether (meth)acrylate, polyethylene glycol (degree of polymerization = 2 to 10) ethyl ether (meth)acrylate, polyethylene glycol (degree of polymerization = 2 to 10) propyl ether (meth)acrylate, and polyethylene glycol (degree of polymerization = 2 to 10) phenyl ether (meth)acrylate; and (meth)acrylates having a polypropylene glycol structural unit such as polypropylene glycol (degree of polymerization = 2 to 10) methyl ether (meth)acrylate, polypropylene glycol (degree of polymerization = 2 to 10) ethyl ether (meth)acrylate, polypropylene glycol (degree of polymerization = 2 to 10) propyl ether (meth)acrylate, and polypropylene glycol (degree of polymerization = 2 to 10) phenyl ether (meth)acrylate, with (meth)acrylates having a polyethylene glycol structural unit being preferred.

[0028] Examples of the (meth)acrylate having a hydroxy group include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxylauryl (meth)acrylate.

[0029] Examples of the (meth)acrylate having a lactone-modified hydroxy group include those obtained by adding lactone to the (meth)acrylate having a hydroxy group, and preferred are those obtained by adding caprolactone. The amount of lactone added is preferably 1 mol to 10 mol, more preferably 1 mol to 5 mol. Preferred examples of the (meth)acrylate having a lactone-modified hydroxy group include a 1-mol caprolactone adduct of 2-hydroxyethyl (meth)acrylate, a 2-mol caprolactone adduct of 2-hydroxyethyl (meth)acrylate, a 3-mol caprolactone adduct of 2-hydroxyethyl (meth)acrylate, a 4-mol caprolactone adduct of 2-hydroxyethyl (meth)acrylate, a 5-mol caprolactone adduct of 2-hydroxyethyl (meth)acrylate, and a 10-mol caprolactone adduct of 2-hydroxyethyl (meth)acrylate.

[0030] Examples of the (meth)acrylate having an alkoxy group include methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, and phenoxyethyl (meth)acrylate.

[0031] The (meth)acrylate having an oxygen-containing heterocyclic group is preferably a (meth)acrylate having a 4- to 6-membered oxygen-containing heterocyclic group. Specific examples of the (meth)acrylate having an oxygen-containing heterocyclic group include glycidyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, (3-ethyloxetan-3-yl)methyl (meth)acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, 2-[(2-tetrahydropyranyl)oxy]ethyl (meth)acrylate, and 1,3-dioxane-(meth)acrylate.

[0032] Examples of the α-olefin include 1-hexene, 1-octene, and 1-decene. Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, 4-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methoxystyrene, 2-hydroxymethylstyrene, and 1-vinylnaphthalene. Examples of the heterocycle-containing unsaturated monomer include 2-vinylthiophene, N-methyl-2-vinylpyrrole, 2-vinylpyridine, and 4-vinylpyridine. Examples of the vinylamide include N-vinylformamide and N-vinylacetamide. Examples of the vinyl carboxylate include vinyl acetate, vinyl pivalate, and vinyl benzoate. Examples of the dienes include butadiene, isoprene, 4-methyl-1,4-hexadiene, and 7-methyl-1,6-octadiene.

[0033] The vinyl monomer having no acidic group is preferably at least one selected from the group consisting of (meth)acrylates having a chain alkyl group (straight-chain alkyl group or branched-chain alkyl group), (meth)acrylates having a cyclic alkyl group, (meth)acrylates having a polycyclic structure, (meth)acrylates having an aromatic group, (meth)acrylates having a polyalkylene glycol structural unit, (meth)acrylates having a hydroxy group, (meth)acrylates having a lactone-modified hydroxy group, (meth)acrylates having an alkoxy group, (meth)acrylates having an oxygen-containing heterocyclic group, and aromatic vinyl monomers.

[0034] (organic solvent) The polymerization reaction is carried out in an organic solvent. The organic solvent is not particularly limited, and an aprotic organic solvent or a protic organic solvent generally used in radical polymerization can be used. The solvents may be used alone or in combination of two or more. The organic solvent is preferably one that can dissolve the polymer (X). The organic solvent is preferably a hydrophilic organic solvent. Examples of the aprotic solvent include acetonitrile, methyl ethyl ketone, anisole, benzene, toluene, propylene glycol monomethyl ether acetate, ethyl acetate, tetrahydrofuran (THF), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), acetone, dioxane, chloroform, carbon tetrachloride, tetrahydrofuran (THF), and trifluoromethylbenzene. Examples of the protic solvent include methanol, ethanol, isopropanol, n-butanol, ethyl cellosolve, butyl cellosolve, 1-methoxy-2-propanol, hexafluoroisopropanol, and diacetone alcohol.

[0035] The amount of the organic solvent used may be adjusted as appropriate. For example, it is preferably 0.01 ml or more, more preferably 0.05 ml or more, and even more preferably 0.1 ml or more, per 1 g of vinyl monomer, and is preferably 50 ml or less, more preferably 10 ml or less, and even more preferably 1 ml or less.

[0036] (polymerization method) As the polymerization method for polymerizing the monomer composition, either a free radical polymerization method or a living radical polymerization method can be adopted. As the polymerization method, living radical polymerization is preferred. Living radical polymerization is preferred in that it maintains the simplicity and versatility of conventional radical polymerization methods, while being less susceptible to termination reactions and chain transfer, and allows growth without being hindered by side reactions that deactivate the growing ends, making it easy to precisely control the molecular weight distribution and produce a polymer with a uniform composition.

[0037] (living radical polymerization method) Living radical polymerization methods include those using compounds capable of generating nitroxide radicals (nitroxide method; NMP method), those using metal complexes such as copper or ruthenium to initiate polymerization of halogenated compounds (ATRP), those using dithiocarboxylic acid esters or xanthates (RAFT method), those using organotellurium compounds (TERP method), those using organic iodine compounds (ITP method), and those using iodine compounds as initiators and organic compounds such as phosphorus compounds, nitrogen compounds, oxygen compounds, or hydrocarbons as catalysts (reversible transfer catalyzed polymerization; RTCP method, reversible catalyst-mediated polymerization; RCMP method). Among these methods, the TERP method is preferred due to its versatile monomer compatibility, molecular weight control in the polymer range, uniform composition, and colorability.

[0038] The TERP method is a method of polymerizing a radically polymerizable compound (vinyl monomer) using an organic tellurium compound as a chain transfer agent, and is a method described, for example, in WO 2004 / 14848, WO 2004 / 14962, WO 2004 / 072126, and WO 2004 / 096870.

[0039] Specific polymerization methods of the TERP method include the following (a) to (d). (a) A method of polymerizing a vinyl monomer using an organotellurium compound represented by formula (1). (b) A method of polymerizing a vinyl monomer using a mixture of an organotellurium compound represented by formula (1) and an azo-based polymerization initiator. (c) A method of polymerizing a vinyl monomer using a mixture of an organic tellurium compound represented by formula (1) and an organic ditelluride compound represented by formula (2). (d) A method of polymerizing a vinyl monomer using a mixture of an organic tellurium compound represented by formula (1), an azo-based polymerization initiator, and an organic ditelluride compound represented by formula (2).

[0040] [ka] [In formula (1), R 1 R is an alkyl group having 1 to 8 carbon atoms, an aryl group, or an aromatic heterocyclic group. 2 and R 3 are each independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. 4 is an alkyl group having 1 to 8 carbon atoms, an aryl group, a substituted aryl group, an aromatic heterocyclic group, an alkoxy group, an acyl group, an amido group, an oxycarbonyl group, a cyano group, an allyl group, or a propargyl group. In equation (2), R 1 is an alkyl group having 1 to 8 carbon atoms, an aryl group, or an aromatic heterocyclic group.]

[0041] Specific examples of the organic tellurium compound represented by formula (1) include ethyl 2-methyl-2-n-butyltellanyl propionate, ethyl 2-n-butyltellanyl propionate, (2-hydroxyethyl) 2-methyl-methyltellanyl propionate, and the organic tellurium compounds described in WO 2004 / 14848, WO 2004 / 14962, WO 2004 / 072126, and WO 2004 / 096870. Specific examples of the organic ditelluride compound represented by formula (2) include dimethyl ditelluride and dibutyl ditelluride. The azo polymerization initiator can be any azo polymerization initiator used in ordinary radical polymerization without any particular limitation, and examples thereof include 2,2'-azobis(isobutyronitrile) (AIBN), 2,2'-azobis(2,4-dimethylvaleronitrile) (ADVN), 1,1'-azobis(1-cyclohexanecarbonitrile) (ACHN), and 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70).

[0042] In the polymerization step, a vinyl monomer and an organotellurium compound of formula (1) are mixed in a vessel purged with an inert gas, and depending on the type of vinyl monomer, an azo polymerization initiator and / or an organic ditelluride compound of formula (2) is further added for the purpose of promoting the reaction and controlling the molecular weight and molecular weight distribution. Examples of inert gases used in this step include nitrogen, argon, and helium. Argon and nitrogen are preferred. The amounts of vinyl monomer used in steps (a), (b), (c), and (d) can be adjusted appropriately depending on the physical properties of the desired polymer.

[0043] The reaction temperature and reaction time in living radical polymerization may be adjusted appropriately depending on the molecular weight or molecular weight distribution of the resulting polymer component, but are usually carried out at 0° C. to 150° C. and stirring for 1 minute to 100 hours. The pressure during this polymerization is usually normal pressure, but may be increased or decreased.

[0044] The growing end of the polymer obtained by the polymerization reaction is -TeR derived from tellurium compounds. 1 (In the formula, R 1is the same as above), and is deactivated by handling in air after the polymerization reaction is completed, but tellurium atoms may remain. A polymer with tellurium atoms remaining at the end will be colored and have poor thermal stability, so it is preferable to remove the tellurium atoms. Methods for removing tellurium atoms include radical reduction; adsorption with activated carbon, etc.; and metal adsorption with ion exchange resin, etc., and these methods can also be used in combination. The other end of the polymer obtained by the polymerization reaction (the end opposite to the growing end) is formed from -CR derived from the tellurium compound. 2 R 3 R 4 (In the formula, R 2 , R 3 and R 4 is R in Eq. (1) 2 , R 3 and R 4 (The same as above.) After the removal of the tellurium atoms, tellurium compounds derived from the chain transfer agent may remain in the polymer as impurities (more than 0 ppm). The content of the tellurium compounds can be controlled by a purification step (liquid separation step) after the polymerization reaction is completed. From the viewpoints of coloration and thermal stability, the content of tellurium in the polymer is preferably 500 ppm by mass or less, more preferably 100 ppm by mass or less, calculated as metal, relative to the polymer.

[0045] (Free radical polymerization method) The free radical polymerization method may be a conventionally known method. Examples of polymerization initiators used in free radical polymerization include azo polymerization initiators and peroxide polymerization initiators. Examples of the azo polymerization initiators include 2,2'-azobis(isobutyronitrile) (AIBN), 2,2'-azobis(2-methylbutyronitrile) (AMBN), 2,2'-azobis(2,4-dimethylvaleronitrile) (ADVN), 1,1'-azobis(1-cyclohexanecarbonitrile) (ACHN), dimethyl-2,2'-azobisisobutyrate (MAIB), 4,4'-azobis(4-cyanovaleric acid) (ACVA), 1,1'-azobis(1-acetoxy-1-phenylethane), 2,2'-azobis(2-methylbutyramide), 2,2'-azobis(2-methylbutyramide), 2,2'-azobis(2-methylbutyronitrile ... Examples include azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70), 2,2'-azobis(2-methylamidinopropane) dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane], 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], 2,2'-azobis(2,4,4-trimethylpentane), 2-cyano-2-propylazoformamide, 2,2'-azobis(N-butyl-2-methylpropionamide), and 2,2'-azobis(N-cyclohexyl-2-methylpropionamide).

[0046] The reaction temperature and reaction time in the free radical polymerization may be adjusted appropriately depending on the molecular weight or molecular weight distribution of the resulting polymer component, but the reaction is usually carried out at 0° C. to 150° C. and for 1 minute to 100 hours with stirring. The pressure during this process is usually normal pressure, but may be increased or decreased.

[0047] (Polymer(X)) The polymer (X) obtained in the first step has structural units derived from a vinyl monomer having no acidic group and structural units derived from a vinyl monomer having an acidic group, and has an acid value of 30 mgKOH / g to 250 mgKOH / g.

[0048] The content of the structural units derived from the vinyl monomer having no acidic group is preferably 50% by mass or more, more preferably 65% ​​by mass or more, and even more preferably 75% by mass or more, and is preferably 98% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less, based on 100% by mass of the polymer (X).

[0049] The content of the structural units derived from the vinyl monomer having an acidic group is preferably 2% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, and is preferably 50% by mass or less, more preferably 35% by mass or less, and even more preferably 25% by mass or less, based on 100% by mass of the polymer (X).

[0050] The acid value of the polymer (X) is 30 mgKOH / g or more, preferably 50 mgKOH / g or more, more preferably 70 mgKOH / g or more, and 250 mgKOH / g or less, preferably 150 mgKOH / g or less, more preferably 120 mgKOH / g or less. If the acid value is 30 mgKOH / g or more, good solubility is exhibited in the fourth step, and if it is 250 mgKOH / g or less, the hydrophilic organic solvent can be distilled off with reduced foaming in the third step.

[0051] The molecular weight of the polymer (X) is measured by gel permeation chromatography (hereinafter referred to as "GPC"). The weight average molecular weight (Mw) of the polymer (X) is preferably 5,000 or more, more preferably 7,500 or more, and even more preferably 10,000 or more, and is preferably 50,000 or less, more preferably 35,000 or less, and even more preferably 20,000 or less. If the weight average molecular weight is within the above range, the dispersing performance when used as a dispersant will be better.

[0052] The molecular weight distribution (Mw / Mn) of the polymer (X) is preferably 3.0 or less, more preferably 2.5 or less, and even more preferably 2.0 or less. In the present invention, the molecular weight distribution (Mw / Mn) is calculated by (weight average molecular weight (Mw) of the block copolymer) / (number average molecular weight (Mn) of the block copolymer). The smaller the Mw / Mn, the narrower the molecular weight distribution, resulting in a copolymer with a uniform molecular weight. When the Mw / Mn value is 1.0, the molecular weight distribution is narrowest. In other words, the lower limit of Mw / Mn is 1.0. When the molecular weight distribution (Mw / Mn) of the block copolymer exceeds 3.0, the copolymer will contain both low and high molecular weight copolymers.

[0053] The polymer (X) may be any of a random copolymer, a block copolymer, and a graft copolymer, and is preferably a block copolymer. The polymer (X) is preferably a block copolymer having an A block containing structural units derived from a vinyl monomer having an acidic group and a B block substantially free of structural units derived from a vinyl monomer having an acidic group.

[0054] The content of structural units derived from vinyl monomers having an acidic group in the A block is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, based on 100% by mass of the A block, and is preferably 95% by mass or less, more preferably 80% by mass or less, and even more preferably 60% by mass or less.

[0055] The vinyl monomer having an acidic group capable of forming the A block is preferably (meth)acrylic acid and / or a (meth)acrylate having a carboxy group, more preferably (meth)acrylic acid.

[0056] The A block may contain a structural unit derived from a vinyl monomer having no acidic group. When the A block contains a structural unit derived from a vinyl monomer having no acidic group, the content thereof is preferably 5% by mass or more, more preferably 20% by mass or more, and even more preferably 40% by mass or more, and is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less, based on 100% by mass of the A block.

[0057] The vinyl monomer having no acidic group capable of forming the A block is preferably at least one selected from the group consisting of (meth)acrylates having a chain alkyl group (straight-chain alkyl group or branched-chain alkyl group), (meth)acrylates having a cyclic alkyl group, (meth)acrylates having a polycyclic structure, (meth)acrylates having an aromatic group, (meth)acrylates having a polyalkylene glycol structural unit, (meth)acrylates having a hydroxy group, (meth)acrylates having a lactone-modified hydroxy group, (meth)acrylates having an alkoxy group, (meth)acrylates having an oxygen-containing heterocyclic group, and aromatic vinyl monomers.

[0058] When two or more types of structural units are contained in the A block, the various structural units contained in the A block may be contained in the A block in any form, such as random copolymerization or block copolymerization, and from the viewpoint of uniformity, they are preferably contained in the A block in the form of random copolymerization. For example, the A block may be formed from a copolymer of structural units consisting of the a1 block and structural units consisting of the a2 block.

[0059] The content of structural units derived from vinyl monomers having an acidic group in the B block is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less, based on 100% by mass of the B block.

[0060] The B block contains structural units derived from vinyl monomers having no acidic groups, and the content of structural units derived from vinyl monomers having no acidic groups is preferably 95% by mass or more, more preferably 97% by mass or more, and even more preferably 99% by mass or more, based on 100% by mass of the B block.

[0061] The vinyl monomer having no acidic group capable of forming the B block is preferably at least one selected from the group consisting of (meth)acrylates having a chain alkyl group (straight-chain alkyl group or branched-chain alkyl group), (meth)acrylates having a cyclic alkyl group, (meth)acrylates having a polycyclic structure, (meth)acrylates having an aromatic group, (meth)acrylates having a polyalkylene glycol structural unit, (meth)acrylates having a hydroxy group, (meth)acrylates having a lactone-modified hydroxy group, (meth)acrylates having an alkoxy group, (meth)acrylates having an oxygen-containing heterocyclic group, and aromatic vinyl monomers.

[0062] When two or more types of structural units are contained in the B block, the various structural units contained in the B block may be contained in the B block in any form, such as random copolymerization or block copolymerization, and from the viewpoint of uniformity, they are preferably contained in the B block in the form of random copolymerization. For example, the B block may be formed from a copolymer of structural units consisting of the b1 block and structural units consisting of the b2 block.

[0063] The content of the A block is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, based on 100% by mass of the entire block copolymer, and is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less. The content of the B block is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, and is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less, based on 100% by mass of the entire block copolymer. By adjusting the contents of the A block and the B block within the above ranges, the dispersing performance when used as a dispersant is further improved.

[0064] The mass ratio of the A block to the B block in the block copolymer (A block / B block) is preferably 0.3 or more, more preferably 0.5 or more, and is preferably 3.0 or less, more preferably 2.5 or less. If the mass ratio of the A block to the B block is within the above range, the dispersing performance when used as a dispersant is further improved.

[0065] The structure of the block copolymer is preferably a linear block copolymer. The linear block copolymer may have any structure (arrangement). However, from the viewpoint of the physical properties of the linear block copolymer or the physical properties of the composition, when the A block is represented as A and the B block is represented as B, the structure is (AB) m Type, (AB) m -A type and (BA) m It is preferable that the copolymer has at least one structure selected from the group consisting of -B type (m is an integer of 1 or more, for example, an integer of 1 to 3).

[0066] Among these, AB diblock copolymers, ABA triblock copolymers, and BAB triblock copolymers are preferred from the viewpoints of ease of handling during processing and the physical properties of the composition. By constructing an AB diblock copolymer, ABA triblock copolymer, or BAB triblock copolymer, it is believed that structural units derived from vinyl monomers having acidic groups in the A block are localized, allowing for efficient and favorable interaction with the pigment and the dispersion medium (solvent). In the case of a triblock copolymer represented by ABA, the two A blocks located at both ends may be the same or different. In the case of a triblock copolymer represented by BAB, the two B blocks located at both ends may be the same or different. The block copolymer may also have blocks other than the A block and the B block.

[0067] Examples of methods for producing a diblock copolymer include a method in which an A block is first produced by a polymerization reaction of a vinyl monomer and then a monomer for a B block is polymerized onto the A block; a method in which a B block is first produced and then a monomer for an A block is polymerized onto the B block; and a method in which the A block and the B block are produced separately and then the A block and the B block are coupled together.

[0068] Examples of methods for producing a triblock copolymer include a method in which an A1 block is first produced by a polymerization reaction of a vinyl monomer, a B block monomer is polymerized onto the A1 block to produce an A1-B block, and then a A2 block monomer is polymerized onto the A1-B block; and a method in which a B1 block is first produced by a polymerization reaction of a vinyl monomer, an A block monomer is polymerized onto the B1 block to produce a B1-A block, and then a B2 block monomer is polymerized onto the B1-A block.

[0069] When polymer (X) is an A1-B-A2 triblock copolymer, the mass ratio (A1 / A2) is preferably 0.5 or more, more preferably 0.7 or more, and preferably 2 or less, more preferably 1.5 or less. When polymer (X) is a B1-A-B2 triblock copolymer, the mass ratio (B1 / B2) is preferably 0.5 or more, more preferably 0.7 or more, and preferably 2 or less, more preferably 1.5 or less.

[0070] (Preparation of polymer-containing solution) If the polymer is uniformly dissolved in the reaction solution after polymerization, this reaction solution can be used as the polymer-containing solution in the second step described below. If the reaction solution does not contain a hydrophilic organic solvent, it is preferable to add a hydrophilic organic solvent to the reaction solution. If the polymer produced is not dissolved after the polymerization reaction is complete, it is preferable to add an organic solvent to dissolve the polymer and prepare a polymer-containing solution.

[0071] (liquid separation) The reaction solution after polymerization may be subjected to a separation treatment, which can reduce impurities in the polymer-containing solution. In the liquid separation treatment, a hydrophilic organic solvent and a hydrophobic organic solvent are added to and mixed with the reaction liquid after polymerization, and then the liquid is separated into a hydrophobic organic solvent phase and a hydrophilic organic solvent phase, and the hydrophobic organic solvent phase is removed to obtain a polymer-containing solution (hydrophilic organic solvent phase).

[0072] The hydrophilic organic solvent is not particularly limited as long as it is an organic solvent that is miscible with water, dissolves the polymer (X), and does not react with the polymer (X). The hydrophilic organic solvent preferably has a solubility parameter (SP value) of 9.3 or more and 15.0 or less. The solubility parameter is the Hildebrand solubility parameter (at 25°C, unit (cal / cm 3 ) 1 / 2 )

[0073] Examples of the hydrophilic organic solvent include primary alcohols such as methanol (SP value: 14.5), ethanol (SP value: 12.7), n-butanol (SP value: 11.4), and n-hexanol (SP value: 10.7); secondary alcohols such as isopropanol (SP value: 11.5); tertiary alcohols such as t-butanol (SP value: 10.6); ethylene glycol (SP value: 14.6), tetrahydrofuran (SP value: 9.1), methyl ethyl ketone (SP value: 9.3), acetone (SP value: 10.0), 1-methoxy-2-propanol (SP value: 11.3), and acetonitrile (SP value: 11.9), and may also be mixed solvents thereof. When the hydrophilic organic solvent is a mixed solvent, the mixed solvent preferably has a liquid composition with an SP value of 9.3 or more and 15.0 or less. The SP value of the mixed solvent can be calculated as the sum of the products of the SP values ​​of each solvent and the volume fraction.

[0074] The hydrophobic organic solvent is an organic solvent that is immiscible with the hydrophilic organic solvent. The hydrophobic organic solvent preferably does not dissolve the polymer (X) and does not react with the polymer (X). The hydrophobic organic solvent preferably has an SP value of less than 9.3.

[0075] Examples of the hydrophobic organic solvent include aliphatic hydrocarbons such as pentane (SP value: 7.0), hexane (SP value: 7.3), heptane (SP value: 7.4), octane (SP value: 7.6), nonane, and decane; alicyclic hydrocarbons such as cyclohexane (SP value: 8.2); and aromatic hydrocarbons such as benzene (SP value: 9.2) and toluene (SP value: 8.9). Mixed solvents of these may also be used. When the hydrophobic organic solvent is a mixed solvent, the mixed solvent preferably has a liquid composition with an SP value of less than 9.3. The SP value of the mixed solvent can be calculated as the sum of the products of the SP values ​​of the individual solvents and their volume fractions.

[0076] The difference (SP1-SP2) between the SP value (SP1) of the hydrophilic organic solvent and the SP value (SP2) of the hydrophobic organic solvent is preferably 1.0 or more, more preferably 3.0 or more, and even more preferably 5.0 or more. When the difference (SP1-SP2) is 1.0 or more, separation into the hydrophobic organic solvent phase and the hydrophilic organic solvent phase can be more easily performed. The upper limit of the difference (SP1-SP2) is not particularly limited, but is usually about 8.0.

[0077] <Second process> In the second step, water is added to the polymer-containing solution obtained in the first step to precipitate at least a portion of the polymer, thereby preparing a polymer dispersion.

[0078] The content of polymer (X) in the polymer-containing solution is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, and is preferably 70% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less. If the content of polymer (X) is 10% by mass or more, separation into a hydrophobic organic solvent phase and a hydrophilic organic solvent phase can be carried out more efficiently, and if it is 70% by mass or less, the viscosity of the hydrophilic organic solvent phase does not become too high, and working efficiency is further improved.

[0079] The mass ratio of the polymer-containing solution to the water added (water / polymer-containing solution) is preferably 0.1 or more, more preferably 0.3 or more, and even more preferably 0.5 or more, and is preferably 5.0 or less, more preferably 4.0 or less, and even more preferably 2.0 or less. If the mass ratio (water / polymer-containing solution) is 0.1 or more, at least a portion of the polymer can be precipitated, and if it is 5.0 or less, there is no need to distill off more than necessary.

[0080] The liquid temperature when water is added to the polymer-containing solution is not particularly limited, and may be adjusted so that at least a portion of the polymer precipitates.

[0081] After adding water to the polymer solution, it is preferable to stir the solution, which can reduce the particle size of the precipitated polymer.

[0082] In the obtained polymer dispersion, at least a portion of the polymer (X) is precipitated. It is not necessary for all of the polymer (X) to be precipitated, as long as the polymer (X) is precipitated to an extent that foaming in the distillation step described below can be suppressed. The proportion of the precipitated polymer (X) in the total polymer (X) in the polymer dispersion is preferably 10% by mass or more, more preferably 50% by mass or more, even more preferably 90% by mass or more, and particularly preferably 99% by mass or more. The amount of precipitated polymer (X) can be adjusted by the amount of water added and the liquid temperature.

[0083] In the polymer dispersion, the number average particle diameter of the precipitated polymer (X) is preferably 500 μm or less, more preferably 300 μm or less, and even more preferably 150 μm or less. If the number average particle diameter is 500 μm or less, it becomes easier to dissolve the polymer when finally neutralizing the polymer (X) to prepare a polymer aqueous solution. The lower limit of the number average particle diameter is not particularly limited, and is greater than 0 μm.

[0084] In the second step, a basic component may be added together with water to neutralize some of the acidic groups of the polymer (X). Neutralizing some of the acidic groups of the polymer (X) can reduce the particle size of the precipitated polymer. In addition, the hardness of the precipitated polymer decreases, making it easier to reduce the particle size by stirring.

[0085] Examples of the basic component include alkali metal hydroxides, alkaline earth metal hydroxides, aliphatic amine compounds, alcohol amines, ammonia, etc., and these may be used alone or in combination. The basic component is preferably an alkali metal hydroxide or an alkaline earth metal hydroxide, more preferably an alkali metal hydroxide. Examples of the alkali metal include lithium, sodium, potassium, rubidium, cesium, and francium, and examples of the alkaline earth metal include magnesium, calcium, strontium, barium, and radium.

[0086] Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, and potassium hydroxide, and sodium hydroxide and potassium hydroxide are preferred. Examples of the alkaline earth metal hydroxides include beryllium hydroxide, magnesium hydroxide, calcium hydroxide, and strontium hydroxide. Examples of the aliphatic amine compound include monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, and triethylamine, and preferably triethylamine. Examples of the alcoholamine compound include monoethanolamine, diethanolamine, triethanolamine, monopropanolamine, dipropanolamine, tripropanolamine, methylethanolamine, dimethylethanolamine, and N-methyldiethanolamine, and are preferably tertiary amines, and more preferably triethanolamine.

[0087] These basic components are preferably added as an aqueous solution. When the basic component is added as an aqueous solution, the concentration of the basic component in the aqueous solution is preferably 1.0% by mass to 50% by mass.

[0088] When a portion of the acidic groups of the polymer (X) is neutralized in the second step, the degree of neutralization of the acidic groups of the polymer (X) is preferably more than 0 mol% and less than 40 mol%, more preferably 20 mol% or less, and even more preferably 5 mol% or less. If the degree of neutralization of the acidic groups of the polymer (X) is less than 40 mol%, foaming in the distillation step described below can be suppressed.

[0089] <3rd process> In the third step, the organic solvent is distilled off from the polymer dispersion to prepare an aqueous polymer dispersion. In the production method of the present invention, the organic solvent is distilled off from the polymer dispersion in which at least a portion of the polymer has been precipitated, so that foaming is suppressed and the organic solvent can be distilled off efficiently.

[0090] The viscosity of the polymer dispersion when the organic solvent is distilled off is preferably 10,000 mPa·s or less, more preferably 5,000 mPa·s or less, and even more preferably 1,000 mPa·s or less. A viscosity of 10,000 mPa·s or less allows stirring without placing a strain on the equipment. There is no particular lower limit to the viscosity of the polymer dispersion when the organic solvent is distilled off, but it is usually 1 mPa·s.

[0091] The liquid temperature of the polymer dispersion when distilling off the organic solvent is preferably 25° C. or higher, more preferably 30° C. or higher, and even more preferably 40° C. or higher, and is preferably 100° C. or lower, more preferably 80° C. or lower, and even more preferably 60° C. or lower. If the liquid temperature is 25° C. or higher, the organic solvent can be distilled off efficiently and workability can be improved, and if the liquid temperature is 100° C. or lower, decomposition of the polymer can be suppressed.

[0092] The pressure when distilling off the organic solvent is preferably 10 kPa or more, more preferably 20 kPa or more, and preferably 40 kPa or less, more preferably 30 kPa or less. If the pressure is 10 kPa or more, bumping of the polymer dispersion is suppressed, making it easier to distill off the organic solvent, and if the pressure is 40 kPa or less, the organic solvent can be efficiently distilled off even when the temperature of the polymer dispersion is 25°C to 100°C.

[0093] The content of the organic solvent in the aqueous polymer dispersion is preferably 1.0% by mass or less, more preferably 0.8% by mass or less, even more preferably 0.2% by mass or less, and particularly preferably 0.02% by mass or less.

[0094] <4th process> In the fourth step, a basic component is added to the aqueous polymer dispersion to neutralize the acidic groups of the polymer (X), thereby obtaining an aqueous solution of an amphiphilic polymer.

[0095] Examples of the basic component include alkali metal hydroxides, alkaline earth metal hydroxides, aliphatic amine compounds, alcohol amines, ammonia, etc., and these may be used alone or in combination. The basic component is preferably an alkali metal hydroxide or an alkaline earth metal hydroxide, more preferably an alkali metal hydroxide. The basic component may be any of those exemplified in the second step.

[0096] These basic components are preferably added as an aqueous solution. When the basic component is added as an aqueous solution, the concentration of the basic component in the aqueous solution is preferably 1.0% by mass to 50% by mass.

[0097] The liquid temperature of the polymer aqueous dispersion when the basic component is added is preferably 25° C. or higher, more preferably 30° C. or higher, and even more preferably 40° C. or higher, and is preferably 100° C. or lower, more preferably 80° C. or lower, and even more preferably 60° C. or lower. If the liquid temperature is 25° C. or higher, dissolution of the polymer can be promoted, and if it is 100° C. or lower, decomposition of the polymer can be suppressed.

[0098] Polymer (X) or polymer (X) in which some of the acidic groups have been neutralized becomes an amphiphilic polymer by neutralizing the acidic groups in the polymer. The degree of neutralization of the acidic groups in the resulting amphiphilic polymer is preferably 30 mol% or more, more preferably 40 mol% or more, and even more preferably 50 mol% or more, and is preferably 100 mol% or less, more preferably 90 mol% or less, and even more preferably 80 mol% or less.

[0099] The polymer content in the amphiphilic polymer aqueous solution is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 25% by mass or more, and is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 35% by mass or less. If the polymer content is 10% by mass or more, a decrease in production efficiency can be suppressed, and if it is 50% by mass or less, the amphiphilic polymer aqueous solution can be easily handled in terms of viscosity. [Example]

[0100] The present invention will be described in more detail below, specifically with reference to examples. The present invention is not limited to the following examples, and can be practiced with appropriate modifications within the scope of the present invention. Various physical properties in the examples and comparative examples were measured according to the following methods.

[0101] The meanings of the abbreviations are as follows: BTEE: Ethyl 2-methyl-2-n-butyltellanyl propionate DBDT: Dibutyl ditelluride AIBN: 2,2'-azobis(isobutyronitrile) BMA: n-butyl methacrylate MAA: methacrylic acid BzMA: benzyl methacrylate MEK: Methyl ethyl ketone ACN: acetonitrile MeOH: Methanol

[0102] (Polymerization rate) Using a nuclear magnetic resonance (NMR) measurement device (Bruker Biospin, model: AVANCE500 (frequency 500 MHz)), 1 H-NMR was measured (solvent: CDCl3, internal standard: tetramethylsilane). For the obtained NMR spectrum, the integral ratio of the peak derived from the monomer to the peak derived from the polymer was determined, and the polymerization rate of the monomer was calculated.

[0103] (Weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn)) The values ​​were determined by gel permeation chromatography (GPC) using a high-performance liquid chromatograph (Tosoh, Model HLC-8320). Two SKgel SuperMultipore HZ-H (Tosoh) columns were used, tetrahydrofuran was used as the mobile phase, and a differential refractometer was used as the detector. The measurement sample was prepared by dissolving 20 mg of the substance to be measured in 2 mL of tetrahydrofuran and 0.5 mL of methanol, followed by the addition of 250 mg of a 0.6 mol / L hexane solution of trimethylsilyldiazomethane. The measurement conditions were a column temperature of 40°C, a sample injection volume of 10 μm, and a flow rate of 0.2 mL / min. A calibration curve was created using polystyrene (molecular weights: 2,890,000, 1,090,000, 775,000, 427,000, 190,000, 96,400, 37,900, 10,200, 2,630, and 420) as a standard substance, and the weight-average molecular weight (Mw) and number-average molecular weight (Mn) were measured. The molecular weight distribution (Mw / Mn) was calculated from these measurements.

[0104] (acid number) The acid value represents the mass of potassium hydroxide required to neutralize the acidic components per gram of solid content. The sample to be measured was dissolved in tetrahydrofuran, and a few drops of 1.0 w / v% phenolphthalein ethanol (90) solution were added to the resulting solution as an indicator. The solution was then titrated for neutralization with potassium hydroxide (0.1 mol / L)-2-propanol solution. The titration endpoint was determined to be when a slight reddish color remained, and the acid value was calculated using the following formula: A=56.11×Vs×0.1×f / w A: Acid value (mgKOH / g) Vs: Amount (mL) of potassium hydroxide (0.1 mol / L)-2-propanol solution required for titration f: Potassium hydroxide (0.1 mol / L)-2-propanol solution w: Measurement sample mass (g) (solid content equivalent)

[0105] (viscosity) The viscosity was measured using an E-type viscometer (trade name: TVE-22L, manufactured by Toki Sangyo Co., Ltd.) with a cone rotor (0.8°×R24) at 25° C. and a rotor rotation speed of 60 rpm.

[0106] (number average particle size) The polymer dispersion was placed on a petri dish and observed under a microscope (product name: VH-Z100R RZ100-1000, manufactured by KEYENCE Corporation), and the particle diameters (major diameters) of 30 or more polymer particles within the field of view were measured and the average value was calculated.

[0107] (Foaming evaluation) 30 g of polymer dispersion (solid content 13% by mass) was weighed into a 300 ml measuring cylinder. Air was fed into this polymer dispersion at 125 ml / min using a flow meter (Kusano Scientific), and bubbling was carried out for 1 minute. After that, the total volume of the polymer dispersion and the bubbles was read.

[0108] <Production of copolymer> Manufacturing method No.1 (Polymerization process) A flask equipped with an argon gas inlet tube and a stirring blade was charged with 104.1 g of BMA, 45.9 g of MAA, 9.0 g of BTEE, 5.5 g of DBDT, 1.0 g of AIBN, 112.5 g of methyl ethyl ketone, and 37.5 g of acetonitrile, and the mixture was reacted at 60°C for 17 hours to polymerize the A block. The conversion was 99%. The resulting A block had a weight-average molecular weight (Mw) of 7,910, a number-average molecular weight (Mn) of 5,309, and a molecular weight distribution (weight-average molecular weight (Mw) / number-average molecular weight (Mn)) of 1.49.

[0109] A previously argon-purged mixture of 150.0 g of BzMA, 0.5 g of AIBN, 112.5 g of methyl ethyl ketone, and 37.5 g of acetonitrile was added to the reaction solution and reacted at 60 °C for 22 hours to polymerize the B block, yielding a reaction solution containing an AB block copolymer. The polymerization rate was 98%. The resulting AB block copolymer had a weight-average molecular weight (Mw) of 14,680, a number-average molecular weight (Mn) of 9,800, a molecular weight distribution (Mw / Mn) of 1.50, an acid value of 101 mg KOH / g, and a content of structural units derived from vinyl monomers having acidic groups of 15.5% by mass based on 100% by mass of polymer (X). Furthermore, the content of structural units derived from vinyl monomers having an acidic group in 100% by mass of the A block was 30.6% by mass, the content of structural units derived from vinyl monomers having an acidic group in 100% by mass of the B block was 0.3% by mass, and the mass ratio (A block / B block) was 1.0.

[0110] (liquid separation process) To the reaction solution, 800 g of heptane as a hydrophobic organic solvent and 480 g of methanol as a hydrophilic organic solvent were added and stirred. The SP value of the hydrophilic organic solvent (MEK, ACN, and MeOH mixed solvent) was 12.8, and the SP value of the hydrophobic organic solvent (heptane) was 7.4, with a difference (SP1 - SP2) of 5.4. After stirring, the mixture was allowed to stand until the hydrophobic organic solvent phase and the hydrophilic organic solvent phase separated, and then the hydrophilic organic solvent phase was removed to obtain a polymer-containing solution (hydrophilic organic solvent phase). The AB block copolymer was dissolved in the hydrophilic organic solvent phase. The recovered polymer-containing solution was distilled under reduced pressure at 25°C and a pressure of 20 to 40 kPa to adjust the polymer content to 40% to 50% by mass.

[0111] (Precipitation process) To the polymer-containing solution, 900 g of water was added under stirring, and the mixture was stirred for 30 minutes to precipitate at least a portion of the polymer, thereby obtaining a polymer dispersion. The proportion of the precipitated polymer (X) in the total polymer (X) in the polymer dispersion was 99 mass% or more.

[0112] (Distillation process) This polymer dispersion was distilled under reduced pressure at 50°C and a pressure of 10 to 40 kPa to obtain an aqueous polymer dispersion. During distillation, foaming of the polymer dispersion was suppressed, and the distillation could be carried out easily. The total content of organic solvents (MEK, MeOH, and ACN) in the obtained aqueous polymer dispersion was 0.6 mass% or less.

[0113] (neutralization process) To the aqueous polymer dispersion obtained above, 50.5 g of 30% by mass potassium hydroxide solution was added, and the mixture was stirred at 60°C for 1 hour to dissolve the polymer. Further water was added, and the mixture was stirred at 60°C for 1 hour to obtain a uniform aqueous polymer solution (polymer content: 30% by mass).

[0114] Manufacturing method No.2 (Polymerization process, liquid separation process) The polymerization step and the liquid separation step were carried out in the same manner as in Production Method No. 1, to obtain a polymer-containing solution in which the polymer content was adjusted to 40% by mass to 50% by mass.

[0115] (Precipitation process) To the polymer-containing solution, 30.3 g of a 5% by mass potassium hydroxide solution was added dropwise over 30 minutes while stirring to neutralize some of the carboxy groups in the polymer. Next, 900 g of water was added, and the mixture was stirred for 30 minutes to precipitate at least a portion of the polymer, yielding a polymer dispersion. The proportion of the precipitated polymer (X) in the total polymer (X) in the polymer dispersion was 90% by mass or more.

[0116] (Distillation process) A distillation step was carried out to obtain an aqueous polymer dispersion in the same manner as in Production Method No. 1. During the distillation, foaming of the polymer dispersion was suppressed, and the distillation could be carried out easily.

[0117] (neutralization process) To the aqueous polymer dispersion obtained above, 45.5 g of 30% by mass potassium hydroxide solution was added, and the mixture was stirred at 60°C for 1 hour to dissolve the polymer. Further water was added, and the mixture was stirred at 60°C for 1 hour to obtain a uniform aqueous polymer solution (polymer content: 30% by mass).

[0118] Manufacturing method No.3 (Polymerization process, liquid separation process) The polymerization step and the liquid separation step were carried out in the same manner as in Production Method No. 1, to obtain a polymer-containing solution in which the polymer content was adjusted to 40% by mass to 50% by mass.

[0119] (Precipitation process) To the polymer-containing solution, 121.2 g of a 5% by mass potassium hydroxide solution was added dropwise over 30 minutes while stirring to neutralize some of the carboxyl groups in the polymer. Next, 900 g of water was added, and the mixture was stirred for 30 minutes to precipitate at least a portion of the polymer, yielding a polymer dispersion. The proportion of the precipitated polymer (X) in the total polymer (X) in the polymer dispersion was 10% by mass or more.

[0120] (Distillation process) A distillation step was carried out to obtain an aqueous polymer dispersion in the same manner as in Production Method No. 1. During the distillation, foaming of the polymer dispersion was suppressed, and the distillation could be carried out easily.

[0121] (neutralization process) To the aqueous polymer dispersion obtained above, 30.3 g of a 30% by mass potassium hydroxide solution was added, and the mixture was stirred at 60°C for 1 hour to dissolve the polymer. Further water was added, and the mixture was stirred at 60°C for 1 hour to obtain a uniform aqueous polymer solution (polymer content: 30% by mass).

[0122] Manufacturing method No.4 (Polymerization process) A flask equipped with an argon gas inlet tube and a stirring blade was charged with 52.1 g of BMA, 23.0 g of MAA, 75.0 g of BzMA, 4.5 g of BTEE, 2.8 g of DBDT, 0.5 g of AIBN, 112.5 g of methyl ethyl ketone, and 37.5 g of acetonitrile. The mixture was reacted at 60 °C for 17 hours to polymerize a random copolymer, yielding a reaction solution containing the random copolymer. The conversion was 96%. The resulting random copolymer had a weight-average molecular weight (Mw) of 17,080, a number-average molecular weight (Mn) of 11,070, a molecular weight distribution (Mw / Mn) of 1.54, an acid value of 100 mg KOH / g, and a content of structural units derived from vinyl monomers having acidic groups of 15.3% by mass per 100% by mass of polymer (X).

[0123] (liquid separation process) To the reaction solution, 400 g of heptane as a hydrophobic organic solvent and 160 g of methanol as a hydrophilic organic solvent were added and stirred. The SP value of the hydrophilic organic solvent (MEK, ACN, and MeOH mixed solvent) was 12.3, and the SP value of the hydrophobic organic solvent (heptane) was 7.4, with a difference (SP1 - SP2) of 4.9. After stirring, the mixture was allowed to stand until the hydrophobic organic solvent phase and the hydrophilic organic solvent phase separated, and then the hydrophobic organic solvent phase was removed to obtain a polymer-containing solution. The random copolymer was dissolved in the hydrophilic organic solvent phase. The recovered polymer-containing solution was distilled under reduced pressure at 25°C and a pressure of 20 to 40 kPa to adjust the polymer content to 40% to 50% by mass.

[0124] (Precipitation process) To the polymer-containing solution, 15 g of a 5% by mass potassium hydroxide solution was added dropwise over 30 minutes while stirring to neutralize some of the carboxyl groups in the polymer. Next, 450 g of water was added, and the mixture was stirred for 30 minutes to precipitate at least a portion of the polymer, thereby obtaining a polymer dispersion.

[0125] (Distillation process) This polymer dispersion was distilled under reduced pressure at 50°C and a pressure of 10 to 40 kPa to obtain an aqueous polymer dispersion. During distillation, foaming of the polymer dispersion was suppressed, and the distillation could be carried out easily. The total content of organic solvents (MEK, MeOH, and ACN) in the obtained aqueous polymer dispersion was 0.6 mass% or less.

[0126] (neutralization process) To the aqueous polymer dispersion obtained above, 22.5 g of 30% by mass potassium hydroxide solution was added, and the mixture was stirred at 60°C for 1 hour to dissolve the polymer. Further water was added, and the mixture was stirred at 60°C for 1 hour to obtain a uniform aqueous polymer solution (polymer content: 30% by mass).

[0127] Manufacturing method No.5 (Polymerization process) A flask equipped with an argon gas inlet tube and a stirring blade was charged with 34.7 g of BMA, 15.3 g of MAA, 6.0 g of BTEE, 3.7 g of DBDT, 0.7 g of AIBN, 24.5 g of methyl ethyl ketone, and 25.0 g of acetonitrile, and the mixture was reacted at 60°C for 20 hours to polymerize the A1 block. The polymerization rate was 99%. The resulting A1 block had a weight-average molecular weight (Mw) of 3,840, a number-average molecular weight (Mn) of 2,577, and a molecular weight distribution (weight-average molecular weight (Mw) / number-average molecular weight (Mn)) of 1.49.

[0128] A mixed solution of 100.0 g of BzMA, 50.0 g of methyl ethyl ketone, and 0.7 g of AIBN, which had been previously purged with argon, was added to the reaction solution and reacted at 60°C for 21 hours to polymerize an A1-B block copolymer. The conversion was 99%. The resulting A1-B block had a weight-average molecular weight (Mw) of 10,020, a number-average molecular weight (Mn) of 6,770, and a molecular weight distribution (weight-average molecular weight (Mw) / number-average molecular weight (Mn)) of 1.48.

[0129] A previously argon-purged mixture of 34.7 g of BMA, 15.3 g of MAA, 0.3 g of AIBN, and 60.0 g of methyl ethyl ketone was added to the reaction solution and reacted at 60°C for 18 hours to polymerize the A2 block, yielding a reaction solution containing an A1-B-A2 block copolymer. The polymerization rate was 99%. The resulting A1-B-A2 block copolymer had a weight-average molecular weight (Mw) of 14,850, a number-average molecular weight (Mn) of 9,881, a molecular weight distribution (Mw / Mn) of 1.50, an acid value of 99 mg KOH / g, and a content of structural units derived from vinyl monomers having acidic groups of 15.3% by mass based on 100% by mass of polymer (X). Furthermore, the content of structural units derived from vinyl monomers having an acidic group in 100% by mass of the A1 block was 30.6% by mass, the content of structural units derived from vinyl monomers having an acidic group in 100% by mass of the B block was 0.2% by mass, the content of structural units derived from vinyl monomers having an acidic group in 100% by mass of the A2 block was 30.3% by mass, the mass ratio (A block / B block) was 1.0, and the mass ratio (A1 / A2) was 1.0.

[0130] (liquid separation process) To the reaction solution, 540 g of heptane as a hydrophobic organic solvent and 320 g of methanol as a hydrophilic organic solvent were added and stirred. The SP value of the hydrophilic organic solvent (MEK, ACN, and MeOH mixed solvent) was 12.9, and the SP value of the hydrophobic organic solvent (heptane) was 7.4, resulting in a difference (SP1 - SP2) of 5.5. After stirring, the mixture was allowed to stand until the hydrophobic organic solvent phase and the hydrophilic organic solvent phase separated, and then the hydrophobic organic solvent phase was removed to obtain a polymer-containing solution. The A1-B-A2 block copolymer was dissolved in the hydrophilic organic solvent phase. The recovered polymer-containing solution was distilled under reduced pressure at 25°C and a pressure of 20 to 40 kPa to adjust the polymer content to 40% to 50% by mass.

[0131] (Precipitation process) To the polymer-containing solution, 19.8 g of a 5% by mass potassium hydroxide solution was added dropwise over 30 minutes while stirring to neutralize some of the carboxyl groups in the polymer. Next, 600 g of water was added, and the mixture was stirred for 30 minutes to precipitate at least a portion of the polymer, thereby obtaining a polymer dispersion.

[0132] (Distillation process) This polymer dispersion was distilled under reduced pressure at 50°C and a pressure of 10 to 40 kPa to obtain an aqueous polymer dispersion. During distillation, foaming of the polymer dispersion was suppressed, and the distillation could be carried out easily. The total content of organic solvents (MEK, MeOH, and ACN) in the obtained aqueous polymer dispersion was 0.6 mass% or less.

[0133] (neutralization process) To the aqueous polymer dispersion obtained above, 29.7 g of 30% by mass potassium hydroxide solution was added, and the mixture was stirred at 60°C for 1 hour to dissolve the polymer. Further water was added, and the mixture was stirred at 60°C for 1 hour to obtain a uniform aqueous polymer solution (polymer content: 30% by mass).

[0134] Manufacturing method No.6 (Polymerization process, liquid separation process) The polymerization step and the liquid separation step were carried out in the same manner as in Production Method No. 1, to obtain a polymer-containing solution in which the polymer content was adjusted to 40% by mass to 50% by mass.

[0135] (Neutralization process, distillation process) To the polymer-containing solution, 606 g of a 5% by mass potassium hydroxide solution was added dropwise over 30 minutes while stirring to neutralize all of the carboxy groups in the polymer. Next, 400 g of water was added, and the mixture was stirred for 30 minutes. The resulting solution was distilled under reduced pressure at 50°C and a pressure of 10 to 40 kPa to obtain an aqueous polymer solution. During distillation, the polymer dispersion foamed significantly, making it difficult to remove the organic solvent. The resulting aqueous polymer solution had a total organic solvent (MEK, MeOH, and ACN) content of 0.6% by mass or less. Water was added to the resulting aqueous polymer solution, and the mixture was stirred at 60°C for 1 hour to obtain a homogeneous aqueous polymer solution (polymer content: 30% by mass).

[0136] Manufacturing method No.7 (Polymerization process, liquid separation process) The polymerization step and the liquid separation step were carried out in the same manner as in Production Method No. 1, to obtain a polymer-containing solution in which the polymer content was adjusted to 40% by mass to 50% by mass.

[0137] (Neutralization process, distillation process) To the polymer-containing solution, 242.4 g of a 5% by mass potassium hydroxide solution was added dropwise over 30 minutes while stirring to neutralize some of the carboxy groups in the copolymer. Next, 700 g of water was added, and the mixture was stirred for 30 minutes. The resulting solution was distilled under reduced pressure at 50°C and a pressure of 10 to 40 kPa to obtain an aqueous polymer solution. During distillation, the polymer dispersion foamed significantly, making it difficult to remove the organic solvent. The resulting aqueous polymer solution had a total organic solvent (MEK, MeOH, and ACN) content of 0.6% by mass or less. Water was added to the resulting aqueous polymer solution, and the mixture was stirred at 60°C for 1 hour to obtain a homogeneous aqueous polymer solution (polymer content: 30% by mass).

[0138] Manufacturing method No.8 (Polymerization process, liquid separation process) The polymerization step and the liquid separation step were carried out in the same manner as in Production Method No. 4, to obtain a polymer-containing solution in which the polymer content was adjusted to 40% by mass to 50% by mass.

[0139] (Neutralization process, distillation process) To the polymer-containing solution, 287 g of a 5% by mass potassium hydroxide solution was added dropwise over 30 minutes while stirring to neutralize all of the carboxy groups in the polymer. Next, 170 g of water was added, and the mixture was stirred for 30 minutes. The resulting solution was distilled under reduced pressure at 50°C and a pressure of 10 to 40 kPa to obtain an aqueous polymer solution. During distillation, the polymer dispersion foamed significantly, making it difficult to remove the organic solvent. The resulting aqueous polymer solution had a total organic solvent (MEK, MeOH, and ACN) content of 0.6% by mass or less. Water was added to the resulting aqueous polymer solution, and the mixture was stirred at 60°C for 1 hour to obtain a homogeneous aqueous polymer solution (polymer content: 30% by mass).

[0140] Tables 1 to 3 show the conditions for the polymerization step, separation step, precipitation step, distillation step, and neutralization step in each production method.

[0141] [Table 1]

[0142] [Table 2]

[0143] [Table 3]

[0144] Table 2 and Figure 1 show the results of foaming evaluation of polymer dispersions in each production method. In Production Methods No. 1 to 5, the polymer obtained by polymerization was precipitated in an unneutralized state or in a state with a low degree of neutralization (neutralization degree less than 40 mol%) to form a polymer dispersion, and the hydrophilic organic solvent was replaced with water in this polymer dispersion state. By precipitating the polymer component, foaming was suppressed when the hydrophilic organic solvent was distilled off, and the hydrophilic organic solvent could be removed efficiently.

[0145] In Production Methods 6 to 8, the polymer obtained by polymerization is neutralized to a high degree (neutralization degree of 40 mol % or more), and then the hydrophilic organic solvent is replaced with water. Therefore, when the hydrophilic organic solvent is distilled off, there is a lot of foaming, making it difficult to distill off the hydrophilic organic solvent.

Claims

1. A method for producing an amphiphilic polymer aqueous solution, which comprises an amphiphilic polymer (X) having a structural unit derived from a vinyl monomer having no acidic group and a structural unit derived from a vinyl monomer having an acidic group, the polymer (X) having an acid value of 30 mg KOH / g to 250 mg KOH / g, the acid groups of which have been neutralized, and the degree of neutralization of the acidic groups being 40 mol % or more and 100 mol % or less, a first step of polymerizing a monomer composition containing a vinyl monomer having an acidic group and a vinyl monomer not having an acidic group in an organic solvent to prepare a polymer-containing solution containing a polymer (X) having an acid value of 30 mgKOH / g to 250 mgKOH / g; a second step of adding water to the polymer-containing solution to precipitate at least a portion of the polymer (X) having a degree of neutralization of acidic groups of less than 40 mol % to prepare a polymer dispersion; a third step of distilling off the organic solvent from the polymer dispersion to prepare an aqueous polymer dispersion; and a fourth step of adding a basic component to the aqueous polymer dispersion to neutralize the acidic groups of the polymer (X).

2. In the second step, a basic component is added together with water, 2. The method for producing an aqueous amphiphilic polymer solution according to claim 1, wherein the degree of neutralization of the acidic groups in the polymer (X) is adjusted to more than 0 mol % and less than 40 mol %.

3. 3. The method for producing an amphiphilic polymer aqueous solution according to claim 1 or 2, wherein in the first step, a hydrophilic organic solvent and a hydrophobic organic solvent are added to and mixed with the reaction liquid after polymerization, followed by separation into a hydrophobic organic solvent phase and a hydrophilic organic solvent phase, and then the hydrophobic organic solvent phase is removed to prepare a polymer-containing solution.

4. The method for producing an amphiphilic polymer aqueous solution according to claim 3, wherein the SP value of the hydrophilic organic solvent is 9.3 or more and 15.0 or less.

5. 5. The method for producing an amphiphilic polymer aqueous solution according to claim 3, wherein the hydrophobic organic solvent has an SP value of less than 9.

3.

6. The method for producing an amphiphilic polymer aqueous solution according to any one of claims 1 to 5, wherein the content of the polymer (X) in the polymer-containing solution is 10% by mass to 70% by mass.

7. The method for producing an amphiphilic polymer aqueous solution according to any one of claims 1 to 6, wherein in the second step, a mass ratio of the polymer-containing solution to the water added (water / polymer-containing solution) is 0.1 to 5.

0.

8. The method for producing an amphiphilic polymer aqueous solution according to any one of claims 1 to 7, wherein the weight average molecular weight (Mw) of the polymer (X) is 5,000 to 50,000.

9. The method for producing an amphiphilic polymer aqueous solution according to any one of claims 1 to 8, wherein the molecular weight distribution (Mw / Mn) of the polymer (X) is 3.0 or less.

10. The method for producing an amphiphilic polymer aqueous solution according to any one of claims 1 to 9, wherein the polymer (X) is a block copolymer having an A block containing a structural unit derived from a vinyl monomer having an acidic group, and a B block substantially not containing a structural unit derived from a vinyl monomer having an acidic group.

11. 11. The method for producing an amphiphilic polymer aqueous solution according to claim 10, wherein the mass ratio of the A block to the B block (A block / B block) in the block copolymer is 0.3 to 3.

0.

12. The method for producing an amphiphilic polymer aqueous solution according to any one of claims 1 to 11, wherein the vinyl monomer having no acidic group is at least one selected from the group consisting of (meth)acrylates having a chain alkyl group, (meth)acrylates having a cyclic alkyl group, (meth)acrylates having a polycyclic structure, (meth)acrylates having an aromatic group, (meth)acrylates having a polyalkylene glycol structural unit, (meth)acrylates having a hydroxy group, (meth)acrylates having a lactone-modified hydroxy group, (meth)acrylates having an alkoxy group, (meth)acrylates having an oxygen-containing heterocyclic group, and aromatic vinyl monomers.

13. The method for producing an amphiphilic polymer aqueous solution according to any one of claims 1 to 12, wherein the vinyl monomer having an acidic group is (meth)acrylic acid and / or (meth)acrylate having a carboxy group.

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