Method for producing vinyl polymer

Abstract

To provide a method for producing a vinyl polymer, which can suppress a temperature increase of a reaction solution in a living radical polymerization reaction and can produce the vinyl polymer stably.SOLUTION: Provided is a method for producing a vinyl polymer by living radical polymerization, comprising a polymerization step of adding a monomer(s) and a polymerization solvent in a reactor and polymerizing the monomer(s) in the polymerization solvent. Polymerization is carried out while continuously supplying at least a part of the whole monomer used for polymerization during the polymerization step for at least a certain period during the polymerization step in a situation where the polymerization solvent is boiling.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing a vinyl polymer, and more particularly to a technique for producing a vinyl polymer by living radical polymerization. [Background technology]

[0002] A precision polymerization method called living polymerization has attracted attention because it can produce polymers with narrow molecular weight distributions and can easily produce terminally functionalized polymers and block copolymers. Among them, living radical polymerization is highly useful due to its high versatility and is widely used industrially. Various living radical polymerization methods are known, such as reversible addition-fragmentation chain transfer polymerization (RAFT), nitroxy radical polymerization (NMP), atom transfer radical polymerization (ATRP), polymerization using organotellurium compounds (TERP), polymerization using organoantimony compounds (SBRP), polymerization using organobismuth compounds (BIRP), and iodine transfer polymerization.

[0003] In the field of industrial applications such as paints, pressure sensitive adhesives, adhesives, and sealants, resin compositions containing vinyl block copolymers obtained by living radical polymerization have been developed (see, for example, Patent Document 1). Patent Document 1 discloses the production of block copolymers for adhesive tapes by copolymerizing monomers by living radical polymerization using an organotellurium compound as a polymerization initiator. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-023237 A Summary of the Invention [Problem to be solved by the invention]

[0005] In living radical polymerization, it is important to reduce the amount of initiator relative to the polymerization control agent as much as possible to increase the living property, and to reduce the amount of polymerization solvent to prevent chain transfer to the solvent. On the other hand, if the amount of polymerization solvent is reduced to increase the monomer concentration, the heat generated by the reaction heat in the polymerization reaction (hereinafter also referred to as "polymerization heat") increases, and the need for heat removal may arise. While polymerization heat is rarely a particular problem on a lab scale, it tends to be difficult to remove the heat when it comes to a large production scale, for example, 400 L or more. If heat removal is not performed sufficiently, there is a concern that the temperature of the reaction solution will rise during polymerization, making it impossible to stably produce a polymer.

[0006] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a method for producing a vinyl polymer, which can suppress a temperature rise of a reaction solution in a living radical polymerization reaction and can stably produce a vinyl polymer. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above problems, and have focused on the fact that the boiling point of the initial reaction solution at atmospheric pressure can be lowered by continuously supplying at least a portion of the monomers used in the polymerization reaction into a reactor, and have completed the present invention based on this finding. Specifically, the present invention provides the following means.

[0008] [1] A method for producing a vinyl polymer by living radical polymerization, comprising a polymerization step of charging a monomer and a polymerization solvent into a reactor and polymerizing the monomer in the polymerization solvent, wherein polymerization is carried out while continuously supplying at least a part of the total amount of monomers to be used in the polymerization in the polymerization step into the reactor in a state in which the polymerization solvent is boiling during at least a part of the polymerization step.

[0009] [2] The method for producing a vinyl polymer according to [1] above, wherein in the polymerization step, polymerization is carried out at a pressure in the reactor lower than atmospheric pressure during at least a part of a period during which the monomers are continuously supplied into the reactor. [3] The method for producing a vinyl polymer according to [2] above, wherein in the polymerization step, polymerization is carried out by maintaining the pressure in the reactor at 20 kPa or more and 70 kPa or less during at least a part of a period during which the monomers are continuously supplied into the reactor. [4] The method for producing a vinyl polymer according to any one of the above [1] to [3], wherein the polymerization solvent has a boiling point lower than a boiling point of the monomer. [5] The method for producing a vinyl polymer according to any one of the above [1] to [4], wherein the polymerization solvent has a boiling point of 50° C. or more and 100° C. or less at atmospheric pressure. [6] The method for producing a vinyl polymer according to any one of the above [1] to [5], wherein in the polymerization step, the polymerization solvent is refluxed. [7] The method for producing a vinyl polymer according to any one of the above [1] to [6], wherein the monomer comprises a (meth)acrylic monomer. Effect of the Invention

[0010] According to the present invention, the temperature rise of the reaction solution in a living radical polymerization reaction can be suppressed, and as a result, a vinyl polymer can be stably produced. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention will be described in detail below. In this specification, "(meth)acrylic" means acrylic and / or methacrylic. "(meth)acrylate" means acrylate and / or methacrylate.

[0012] The method for producing a vinyl polymer of the present invention (hereinafter also referred to as "the present production method") relates to a method for producing a vinyl polymer by living radical polymerization. The present production method includes a polymerization step in which a monomer and a polymerization solvent are placed in a reactor and the monomer is polymerized in the polymerization solvent. In this polymerization step, polymerization is carried out while continuously supplying at least a part of the total amount of monomers used in the polymerization in the polymerization step to the reactor in a state in which the polymerization solvent in the reactor is boiling for at least a part of the period.

[0013] <Polymerization process> In the polymerization step of this production method (hereinafter also referred to as "this step"), a known polymerization method can be adopted as the living radical polymerization method. Specific examples of the living radical polymerization method in this step include a living radical polymerization method based on an exchange chain mechanism, a living radical polymerization method based on a bond-dissociation mechanism, and a living radical polymerization method based on an atom transfer mechanism.

[0014] Specific examples of these include reversible addition-fragmentation chain transfer polymerization (RAFT), iodine transfer polymerization, polymerization using an organotellurium compound (TERP), polymerization using an organoantimony compound (SBRP), and polymerization using an organobismuth compound (BIRP), as living radical polymerization methods using a bond-dissociation mechanism, the nitroxy radical method (NMP), as living radical polymerization methods using an atom transfer mechanism, and the atom transfer radical polymerization (ATRP). Among these, the living radical polymerization methods using the exchange chain mechanism are preferred because they can be applied to a wide range of vinyl monomers and have excellent controllability over polymerization, and the RAFT method is particularly preferred from the viewpoint of ease of implementation.

[0015] In the RAFT method, polymerization proceeds through a reversible chain transfer reaction in the presence of a polymerization control agent (RAFT agent) and a radical polymerization initiator. As the RAFT agent, various known RAFT agents such as dithioester compounds, xanthate compounds, trithiocarbonate compounds, and dithiocarbamate compounds can be used. Among these, trithiocarbonate compounds can be preferably used in terms of excellent polymerization control of (meth)acrylic acid esters, and specific examples thereof include S,S-dibenzyltrithiocarbonate, bis[4-(2,3-dihydroxypropoxycarbonyl)benzyl]trithiocarbonate, bis[4-(2-hydroxyethoxycarbonyl)benzyl]trithiocarbonate, and 1,4-bis(n-dodecylsulfanylthiocarbonylsulfanylmethyl)benzene. The amount of the RAFT agent used is appropriately adjusted depending on the type of monomer and RAFT agent used, etc.

[0016] In the polymerization by the RAFT method, known radical polymerization initiators such as azo compounds, organic peroxides and persulfates can be used as the radical polymerization initiator. Among these, azo compounds are preferred because they are safe and easy to handle, and side reactions during radical polymerization are unlikely to occur. Specific examples of azo compounds include 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), dimethyl-2,2'-azobis(2-methylpropionate), 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis[N-(2-propenyl)-2-methylpropionamide], and 2,2'-azobis(N-butyl-2-methylpropionamide). The radical polymerization initiator may be used alone or in combination of two or more kinds.

[0017] The amount of radical polymerization initiator used is not particularly limited, but from the viewpoint of obtaining a polymer with a narrower molecular weight distribution, it is preferably 0.5 mol or less, more preferably 0.4 mol or less, per 1 mol of the RAFT agent. Also, from the viewpoint of stably carrying out the polymerization reaction, the lower limit of the amount of radical polymerization initiator used is preferably 0.01 mol or more, more preferably 0.05 mol or more, per 1 mol of the RAFT agent. The amount of radical polymerization initiator used per 1 mol of the RAFT agent is preferably 0.01 to 0.5 mol, more preferably 0.05 to 0.4 mol.

[0018] In the case of the RAFT method, the polymerization reaction may be carried out, if necessary, in the presence of a chain transfer agent such as an alkylthiol compound having a carbon number of 2 to 20. In addition, if necessary, a dehydrating agent such as trimethyl orthoacetate or triethyl orthoacetate may be mixed into the reaction system.

[0019] The monomer used in the polymerization in this step is not particularly limited, and various vinyl monomers can be used. The monomer used in the polymerization preferably contains a (meth)acrylic monomer, because a vinyl polymer can be produced relatively easily by a living radical polymerization method and because there is a high degree of freedom in the selection of the monomer.

[0020] In the above polymerization, as the (meth)acrylic monomer, at least one selected from the group consisting of (meth)acrylic acid alkyl ester compounds, (meth)acrylic acid aliphatic cyclic ester compounds, (meth)acrylic acid aromatic ester compounds, and compounds represented by the following formula (1) can be preferably used. CH2=CR 1 -C(=O)O-(R 2 O) n -R 3 …(1) (In formula (1), R 1 represents a hydrogen atom or a methyl group, R 2 represents a linear or branched alkylene group having 2 to 6 carbon atoms; R 3represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms. n represents an integer of 1 to 100.

[0021] (Meth)acrylic acid alkyl ester compounds Specific examples of the (meth)acrylic acid alkyl ester compound include methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, and icosyl (meth)acrylate.

[0022] Considering the fluidity of the vinyl polymer obtained by the present production method, among these, the (meth)acrylic acid alkyl ester compound is preferably a (meth)acrylic acid alkyl ester compound in which the alkyl group (R) in the alkyl ester portion (-COOR) has 1 to 20 carbon atoms. The (meth)acrylic acid alkyl ester compound constituting the present polymer is more preferably a (meth)acrylic acid alkyl ester compound having an alkyl group having 2 to 20 carbon atoms, even more preferably a (meth)acrylic acid alkyl ester compound having an alkyl group having 2 to 18 carbon atoms, and even more preferably includes a (meth)acrylic acid alkyl ester compound having an alkyl group having 4 to 18 carbon atoms.

[0023] Aliphatic cyclic ester compounds of (meth)acrylic acid Specific examples of the aliphatic cyclic ester compounds of (meth)acrylic acid include cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, tert-butylcyclohexyl (meth)acrylate, cyclododecyl (meth)acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and dicyclopentanyl (meth)acrylate.

[0024] Aromatic ester compounds of (meth)acrylic acid Specific examples of the aromatic ester compounds of (meth)acrylic acid include phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxymethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, and 3-phenoxypropyl (meth)acrylate.

[0025] A compound represented by formula (1) Regarding the compound represented by the above formula (1), when n in the above formula (1) is 1, the compound represented by the above formula (1) has an oxyalkylene structure such as an oxyethylene chain, an oxypropylene chain, and an oxybutylene chain. Specific examples of the compound in which n in the above formula (1) is 1 (i.e., an (meth)acrylic acid alkoxyalkyl ester compound) include methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, n-propoxyethyl (meth)acrylate, n-butoxyethyl (meth)acrylate, methoxypropyl (meth)acrylate, ethoxypropyl (meth)acrylate, n-propoxypropyl (meth)acrylate, n-butoxypropyl (meth)acrylate, methoxybutyl (meth)acrylate, ethoxybutyl (meth)acrylate, n-propoxybutyl (meth)acrylate, and n-butoxybutyl (meth)acrylate.

[0026] When n in the above formula (1) is 2 or more, the compound represented by the above formula (1) has a polyoxyalkylene structure such as a polyoxyethylene chain, a polyoxypropylene chain, or a polyoxybutylene chain.2 may be the same or different from each other. Therefore, the compound in which n in the above formula (1) is 2 or more may have different types of polyoxyalkylene structures in one molecule, such as a block structure consisting of polyoxyethylene / polyoxypropylene.

[0027] Specific examples of the compound in which n in the above formula (1) is 2 or more include polyoxyethylene (meth)acrylate, polyoxypropylene (meth)acrylate, polyoxybutylene (meth)acrylate, polyoxyethylene-polyoxypropylene (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, lauroxypolyethylene glycol (meth)acrylate, stearoxypolyethylene glycol (meth)acrylate, octoxypolyethylene glycol polypropylene glycol (meth)acrylate, nonylphenoxypolypropylene glycol (meth)acrylate, and phenoxypolyethylene glycol polypropylene glycol (meth)acrylate.

[0028] For example, when a vinyl polymer having high fluidity is produced by the present production method, the (meth)acrylic monomer used is preferably a (meth)acrylic acid alkyl ester compound, more preferably contains a (meth)acrylic acid alkyl ester compound having an alkyl group having 2 to 18 carbon atoms, and even more preferably contains a (meth)acrylic acid alkyl ester compound having an alkyl group having 4 to 18 carbon atoms. Moreover, the (meth)acrylic monomer constituting the present polymer preferably contains at least an acrylic monomer, and more preferably contains an acrylic acid alkyl ester compound in that a polymer having excellent mechanical strength and fluidity can be obtained.

[0029] The amount of the (meth)acrylic acid alkyl ester compound used is preferably 40 mass% or more, more preferably 50 mass% or more, even more preferably 60 mass% or more, still more preferably 70 mass% or more, even more preferably 80 mass% or more, and even more preferably 90 mass% or more, based on the total amount of monomers used in the polymerization to obtain a vinyl polymer in this process.

[0030] In this step, a vinyl monomer (hereinafter also referred to as "other monomer") other than the above-mentioned (meth)acrylic monomer and copolymerizable therewith may be further used. Examples of the other monomer include a styrene compound, a maleimide compound, an amide group-containing vinyl compound, and a vinyl monomer having a crosslinkable functional group. The other monomer may be one or more of these.

[0031] Styrene-based compounds Specific examples of styrene-based compounds include styrene, α-methylstyrene, β-methylstyrene, vinylxylene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o-ethylstyrene, m-ethylstyrene, p-ethylstyrene, pn-butylstyrene, p-isobutylstyrene, pt-butylstyrene, o-methoxystyrene, m-methoxystyrene, p-methoxystyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, p-hydroxystyrene, m-hydroxystyrene, o-hydroxystyrene, p-isopropenylphenol, m-isopropenylphenol, o-isopropenylphenol, o-vinylbenzoic acid, m-vinylbenzoic acid, p-vinylbenzoic acid, divinylbenzene, and vinylnaphthalene.

[0032] The amount of the styrene-based compound used is, for example, 30% by mass or less, preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, based on the total amount of monomers used in the polymerization reaction in this step.

[0033] Maleimide compounds Specific examples of the maleimide compound include maleimide and N-substituted maleimide compounds. Examples of the N-substituted maleimide compound include N-alkyl-substituted maleimide compounds such as N-methylmaleimide, N-ethylmaleimide, Nn-propylmaleimide, N-isopropylmaleimide, Nn-butylmaleimide, N-isobutylmaleimide, N-tert-butylmaleimide, N-pentylmaleimide, N-hexylmaleimide, N-heptylmaleimide, N-octylmaleimide, N-laurylmaleimide, and N-stearylmaleimide; N-cyclopentylmaleimide; imide, and N-cycloalkyl-substituted maleimide compounds such as N-cyclohexylmaleimide; and N-aryl-substituted maleimide compounds such as N-phenylmaleimide, N-(4-hydroxyphenyl)maleimide, N-(4-acetylphenyl)maleimide, N-(4-methoxyphenyl)maleimide, N-(4-ethoxyphenyl)maleimide, N-(4-chlorophenyl)maleimide, N-(4-bromophenyl)maleimide, and N-benzylmaleimide.

[0034] The amount of the maleimide compound used is, for example, 30% by mass or less, preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, based on the total amount of monomers used in the polymerization reaction in this step.

[0035] Amide group-containing vinyl compounds Specific examples of the amide group-containing vinyl compound include (meth)acrylamide, (meth)acrylamide derivatives, and N-vinylamide monomers. Specific examples of the (meth)acrylamide derivatives include tert-butyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide, and (meth)acryloylmorpholine. Specific examples of the N-vinylamide monomers include N-vinylacetamide, N-vinylformamide, and N-vinylisobutylamide.

[0036] The amount of the amide group-containing vinyl compound used is, for example, 20% by mass or less, preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 2% by mass or less, based on the total amount of monomers used in the polymerization reaction in this step.

[0037] · Vinyl monomers with crosslinkable functional groups Examples of the crosslinkable functional group include a crosslinkable silyl group, a silanol group, a carboxyl group, a hydroxyl group, an epoxy group, an oxazoline group, an isocyanate group, and a polymerizable unsaturated group. Examples of the crosslinkable silyl group include an alkoxysilyl group and a halogenosilyl group. Among these, an alkoxysilyl group is preferred in terms of easy control of reactivity, and examples of the alkoxysilyl group include a trimethoxysilyl group, a methyldimethoxysilyl group, a dimethylmethoxysilyl group, a triethoxysilyl group, a methyldiethoxysilyl group, and a dimethylethoxysilyl group.

[0038] Examples of vinyl monomers having a crosslinkable functional group include crosslinkable silyl group-containing vinyl compounds, unsaturated carboxylic acids, unsaturated acid anhydrides, hydroxy group-containing vinyl compounds, epoxy group-containing vinyl compounds, primary or secondary amino group-containing vinyl compounds, oxazoline group-containing vinyl compounds, and isocyanate group-containing vinyl compounds.

[0039] Examples of the crosslinkable silyl group-containing vinyl compound include vinyl silanes such as vinyl trimethoxysilane, vinyl triethoxysilane, vinyl methyl dimethoxysilane, and vinyl dimethyl methoxysilane; alkoxysilyl group-containing (meth)acrylic acid esters such as trimethoxysilylpropyl (meth)acrylate, triethoxysilylpropyl (meth)acrylate, methyl dimethoxysilylpropyl (meth)acrylate, and dimethyl methoxysilylpropyl (meth)acrylate; alkoxysilyl group-containing vinyl ethers such as trimethoxysilylpropyl vinyl ether; and alkoxysilyl group-containing vinyl esters such as vinyl trimethoxysilyl undecanoate. The crosslinkable silyl group-containing vinyl compound forms a crosslinked structure by dehydration condensation between crosslinkable silyl groups, and is therefore suitable in that it can efficiently carry out the polymerization reaction and the subsequent crosslinking reaction when producing a polymer.

[0040] Examples of the unsaturated carboxylic acid include (meth)acrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, citraconic acid, cinnamic acid, and further, monoalkyl esters of unsaturated dicarboxylic acids (monoalkyl esters of maleic acid, fumaric acid, itaconic acid, citraconic acid, etc.), etc. Examples of the unsaturated acid anhydrides include maleic anhydride, itaconic anhydride, citraconic anhydride, etc.

[0041] Examples of the hydroxy group-containing vinyl compound include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, mono(meth)acrylic acid esters of polyalkylene glycols (e.g., polyethylene glycol, polypropylene glycol, etc.); styrene-based compounds such as o-hydroxystyrene, m-hydroxystyrene, and p-hydroxystyrene; maleimide compounds such as N-(4-hydroxyphenyl)maleimide, etc. Among the compounds represented by the above formula (1), R 3 The compound in which is a hydrogen atom is also a vinyl monomer having a crosslinkable functional group.

[0042] Examples of the epoxy group-containing vinyl compound include glycidyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, and 3,4-epoxycyclohexylmethyl (meth)acrylate.

[0043] Of these, the vinyl monomer having a crosslinkable functional group is preferably a crosslinkable silyl group-containing vinyl compound from the viewpoints of the breaking elongation and breaking strength of the cured product.

[0044] The amount of the vinyl monomer having a crosslinkable functional group used is not particularly limited, but from the viewpoint of obtaining a vinyl polymer having excellent mechanical strength, it can be, for example, 0.01% by mass or more, and preferably 0.5% by mass or more, based on the total amount of monomers used in the polymerization reaction in this step. The upper limit of the amount of the vinyl monomer having a crosslinkable functional group used is, for example, 40% by mass or less, and preferably 30% by mass or less, based on the total amount of monomers used in the polymerization reaction in this step, from the viewpoint of ensuring the flexibility of the obtained vinyl polymer.

[0045] When a block copolymer having polymer block (A) and polymer block (B) is produced by this production method, a polymer (hereinafter also referred to as "polymer (a)") that constitutes polymer block (A) and has a thiocarbonylthio group together with a monomer that constitutes polymer block (B) can be used as a raw material. In this case, by making polymer (a) a polymer obtained by using a monofunctional RAFT agent, an (A)-(B) diblock material consisting of polymer block (A) / polymer block (B) can be obtained. In addition, by making polymer (a) a polymer obtained by using a bifunctional RAFT agent such as S,S-dibenzyltrithiocarbonate, an (A)-(B)-(A) triblock material consisting of polymer block (A) / polymer block (B) / polymer block (A) can be obtained. Furthermore, by using a block copolymer having two or more polymer blocks as polymer (a) in the above, a higher order block copolymer can be obtained.

[0046] The polymerization reaction in this step is carried out in a polymerization solvent known in living radical polymerization. As the polymerization solvent, various solvents can be used, such as saturated hydrocarbon compounds, aromatic compounds, ester compounds, ketone compounds, alcohol compounds, ether compounds, nitrile compounds, water, etc. As the polymerization solvent, it is preferable to use a solvent capable of dissolving the monomer. The polymerization solvent may be used alone or in combination of two or more.

[0047] Of these, the polymerization solvent can preferably be one having a boiling point at atmospheric pressure of 50° C. or more and 100° C. or less. Use of a solvent having a boiling point within the above temperature range is preferable in that it is easy to set the reaction temperature when polymerizing the monomers in a state where the polymerization solvent is boiling (hereinafter also referred to as "boiling point polymerization"), and that it is relatively easy to remove the solvent when removing the solvent after polymerization.

[0048] Specific examples of such polymerization solvents include saturated hydrocarbon compounds such as hexane (69°C), heptane (98°C), and cyclohexane (81°C); aromatic compounds such as benzene (80°C); ester compounds such as methyl acetate (57°C), ethyl acetate (77°C), ethyl formate (54°C), and methyl propionate (99°C); ketone compounds such as acetone (56°C) and methyl ethyl ketone (80°C); alcohol compounds such as methanol (65°C), ethanol (78°C), and isopropanol (80°C); ether compounds such as tetrahydrofuran (66°C); and nitrile compounds such as acetonitrile (82°C). Water (100°C) may also be used as the polymerization solvent. The temperatures in parentheses for each of the above polymerization solvents represent the boiling points at atmospheric pressure. As the polymerization solvent, ester compounds are preferred because of their small chain transfer constant, and among ester compounds, ethyl acetate is particularly preferred because of its easy availability.

[0049] The boiling point of the polymerization solvent under atmospheric pressure is more preferably 55° C. or higher and 100° C. or lower, further preferably 60° C. or higher, and even more preferably 65° C. or higher. The upper limit of the boiling point is more preferably 99° C. or lower, and even more preferably 95° C. or lower.

[0050] In addition, it is preferable to use a solvent having a boiling point lower than that of the monomer used in the polymerization in this step as the polymerization solvent. According to this embodiment, polymerization can be performed in a state where the polymerization solvent is boiled while the boiling point of the reaction solution is kept as low as possible. When two or more monomers are used, the boiling point of the monomer that occupies the largest proportion of the total amount of monomers used in polymerization is compared with the boiling point of the polymerization solvent. When two or more polymerization solvents are used, the boiling point of the polymerization solvent that occupies the largest proportion of the total amount of polymerization solvent used in polymerization is compared with the boiling point of the monomer. When there are multiple monomers as the monomer that occupies the largest proportion of the total amount of monomers used in polymerization, it is preferable that the boiling point of the polymerization solvent is lower than each of the boiling points of the multiple monomers. The same applies to the polymerization solvent.

[0051] The amount of the polymerization solvent used is preferably 5 to 200 parts by mass, more preferably 10 to 100 parts by mass, relative to 100 parts by mass of the total amount of the monomers used in the polymerization reaction. When the amount of the polymerization solvent used is 100 parts by mass or less, it is preferable in that the chain transfer to the polymerization solvent can be sufficiently suppressed and a high polymerization rate can be achieved in a short time. In addition, when the amount of the polymerization solvent used is 10 parts by mass or more, it is preferable in that the polymerization heat can be efficiently removed and an increase in the reaction temperature can be suppressed.

[0052] In this step, in addition to raw materials such as monomers and a polymerization solvent, a radical polymerization initiator, a polymerization control agent, etc. are charged into a reactor, and a polymerization reaction is carried out in the polymerization solvent. When charging the monomers into the reactor, all of the monomers to be used in the polymerization are not charged into the reactor all at once, but at least a part of the total amount of the monomers to be used in the polymerization is continuously fed into the reactor after the start of polymerization.

[0053] The mode of continuously supplying the monomer into the reactor is not particularly limited, as long as the monomer is continuously supplied into the reactor during at least a part of the polymerization process. For example, a method may be adopted in which a part of the total amount of the monomers used in the polymerization in this process is charged into the reactor before the start of polymerization, and the remaining monomers are continuously supplied into the reactor after the start of polymerization. In addition, a method may be adopted in which a part of the total amount of the monomers used in the polymerization in this process is charged into the reactor before the start of polymerization, and a part of the remaining monomers is continuously supplied into the reactor after the start of polymerization, and then the remaining monomers are further supplied into the reactor all at once. Alternatively, a method may be adopted in which the polymerization is performed while continuously supplying all of the monomers used in the polymerization into the reactor.

[0054] From the viewpoint of sufficiently lowering the boiling point of the initial reaction solution and effectively suppressing the temperature rise of the reaction solution, it is preferable to continuously supply the monomer during a period including the first half of the polymerization process. In addition, it is preferable to start the continuous supply of the monomer at the beginning of the polymerization process. Specifically, it is preferable to start the continuous supply of the monomer within 2 hours from the start of polymerization, and more preferably within 1 hour. Here, the start of polymerization refers to the time when the reaction solution in the reactor starts to boil in the case of boiling point polymerization.

[0055] During the continuous supply of the monomer into the reactor, the polymer is allowed to grow to obtain a vinyl polymer having a narrow molecular weight distribution, so it is preferable to carry out the polymerization without withdrawing the product from the reactor until the end of the polymerization. The method for continuously supplying the monomer into the reactor is not particularly limited, and can be carried out by a known method such as, for example, a method of dropping the monomer into the reactor.

[0056] The feed rate when the monomer is continuously fed into the reactor is not particularly limited, and can be appropriately set according to the volume of the reactor, the amount of polymerization solvent used, etc. In addition, the time during which the monomer is continuously fed into the reactor is also not particularly limited. From the viewpoint of suppressing an increase in the boiling point of the reaction solution and efficiently removing the heat of polymerization, the time during which the monomer is continuously fed into the reactor can be, for example, 0.2 or more, and is preferably 0.3 to 0.95, assuming that the time required from the start of polymerization to the end of polymerization is 1.

[0057] A preferred embodiment of the method of feeding the monomer into the reactor includes a method in which a part of the total amount of the monomer used for polymerization is charged into the reactor before the start of polymerization, and the remaining monomer is continuously fed into the reactor after the start of polymerization. In this case, the ratio of the monomer continuously fed into the reactor to the total amount of the monomer used for polymerization is preferably 10% by mass or more. By setting the ratio to 10% by mass or more, the boiling point of the reaction solution at the beginning of polymerization can be sufficiently lowered, which is preferable in that the polymerization can be stably performed. The ratio of the monomer continuously fed into the reactor is more preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, and even more preferably 50% by mass or more, to the total amount of the monomer used for polymerization.

[0058] During the period in which the monomer is continuously supplied into the reactor, it is preferable to control the pressure in the reactor so that the polymerization solvent in the reactor is boiling during at least a part of the period. Specifically, during at least a part of the period in which the monomer is continuously supplied into the reactor, it is preferable to control the pressure in the reactor to a pressure lower than atmospheric pressure, and it is more preferable to control the pressure in the reactor to a pressure of 20 kPa or more and 70 kPa or less. By controlling the pressure in the reactor within the above range, it is possible to continue polymerization in a state in which the polymerization solvent is boiling while lowering the boiling point of the reaction solution. This makes it possible to suppress the generation of polymerization heat and to continue polymerization stably. During polymerization in a state in which the polymerization solvent in the reactor is boiling, it is preferable to reflux the polymerization solvent using, for example, a condenser (condenser) in order to suppress the decrease of the polymerization solvent in the reactor.

[0059] In addition, according to the study by the present inventors, it was found that when the pressure in the reactor is lowered, the temperature at which the polymerization solvent condenses in the condenser (condenser) is lowered, and the polymerization solvent cannot be sufficiently recovered by the condenser, and the amount of solvent in the reactor tends to decrease. In this respect, in this process, since the polymerization is carried out while continuously supplying at least a part of the monomers used in the polymerization into the reactor, the boiling point of the initial reaction solution at atmospheric pressure can be lowered. Therefore, the degree of vacuum in the reactor can be set relatively low to make the polymerization solvent boil at the target reaction temperature, and the polymerization solvent can be sufficiently recovered by the condenser. This is preferable in that the decrease in the amount of solvent in the reactor can be suppressed and the polymerization heat can be efficiently removed.

[0060] From the above viewpoint, the pressure in the reactor during the polymerization reaction is preferably 25 kPa or more, more preferably 30 kPa or more, and even more preferably 35 kPa or more. The upper limit of the pressure in the reactor during the polymerization reaction is preferably 65 kPa or less, and more preferably 60 kPa or less. The preferred pressure range in the reactor can be appropriately set by appropriately combining the above-mentioned lower and upper limits. That is, the pressure range in the reactor is preferably 20 kPa or more and 65 kPa or less, more preferably 25 kPa or more and 65 kPa or less, and even more preferably 30 kPa or more and 60 kPa or less.

[0061] The period during which the pressure in the reactor is reduced during the polymerization reaction may be at least a part of the period during which the monomer is continuously fed into the reactor. That is, the polymerization may be carried out in a state in which the pressure in the reactor is reduced during the entire period during which the monomer is continuously fed into the reactor, or the polymerization may be carried out in a state in which the pressure in the reactor is reduced during a part of the entire period during which the monomer is continuously fed into the reactor, and the polymerization may be carried out under atmospheric pressure during the remaining period. In addition, during the polymerization reaction, the jacket temperature (external temperature) of the reactor may be adjusted to promote heat removal by utilizing the temperature difference between the inside and outside of the reactor.

[0062] The reaction temperature and reaction time in the polymerization reaction can be appropriately set depending on the type of living radical polymerization method employed, and the type of monomer and polymerization solvent used. For example, in the case of the RAFT method, the reaction temperature is preferably 40°C or more and 100°C or less, more preferably 45°C or more and 90°C or less, and even more preferably 50°C or more and 80°C or less. A reaction temperature of 40°C or more is preferable in that the polymerization reaction can be smoothly carried out, and a reaction temperature of 100°C or less is preferable in that side reactions can be suppressed and restrictions on the initiator and polymerization solvent that can be used are relaxed. In addition, the reaction time is, for example, 1 hour or more and 48 hours or less, and preferably 2 hours or more and 24 hours or less.

[0063] The above polymerization results in a solution containing a vinyl polymer. The vinyl polymer can be isolated by subjecting the obtained polymer solution to a known solvent removal treatment. The obtained polymer solution may be used as is to prepare a polymer composition for various applications, or may be used after carrying out various treatments (e.g., the following reaction steps) as necessary to prepare a polymer composition for various applications.

[0064] <Other processes> The present production method may further include other steps other than the polymerization step. For example, when the vinyl polymer obtained by the polymerization step has a thiocarbonylthio group derived from a RAFT agent, the vinyl polymer may be reacted with a nucleophilic agent (hereinafter, also referred to as a "reaction step"). By this reaction, a thiol group is generated from the thiocarbonylthio group of the vinyl polymer, and the generated thiol group reacts with the remaining monomer to obtain a vinyl polymer from which the thiocarbonylthio group has been removed.

[0065] Examples of the nucleophilic agent include ammonia, primary and / or secondary amine compounds, alkali metal alkoxides, hydroxides, and thiols, etc. Among these, from the viewpoint of reactivity, primary and / or secondary amine compounds can be preferably used as the nucleophilic agent.

[0066] As described above, according to the present production method, the temperature rise of the reaction solution during the polymerization reaction can be effectively suppressed, and a vinyl polymer can be stably produced. Therefore, the present production method is particularly suitable for producing a vinyl polymer on a large scale (e.g., a scale of 400 L or more).

[0067] According to this production method, a block copolymer having two or more polymer blocks can be stably produced even when a large reactor having a volume of, for example, 400 L or more is used. For example, when a (A)-(B)-(A)-(B)-(A) pentablock copolymer consisting of polymer block (A) / polymer block (B) / polymer block (A) / polymer block (B) / polymer block (A) is produced by the RAFT method using a bifunctional RAFT agent, the target product can be efficiently obtained by producing a vinyl polymer by a method including the following three-stage polymerization process.

[0068] That is, first, in the first polymerization step, a polymer block (A) is obtained using a monomer constituting the polymer block (A). Then, in the second polymerization step, a monomer constituting the polymer block (B) is polymerized to obtain an (A)-(B)-(A) triblock body consisting of polymer block (A) / polymer block (B) / polymer block (A). Furthermore, in the third polymerization step, a monomer constituting the polymer block (A) is polymerized to obtain an (A)-(B)-(A)-(B)-(A) pentablock body consisting of polymer block (A)-polymer block (B)-polymer block (A)-polymer block (B)-polymer block (A). When a vinyl polymer is produced by a three-stage polymerization step in this way, the present production method may be applied to at least one of the first to third polymerization steps, or the present production method may be applied to all of the first to third polymerization steps. Furthermore, by the same method as above, a block copolymer having a higher order than a pentablock body can be obtained as a vinyl polymer.

[0069] The vinyl polymer obtained by the present production method has a polystyrene-equivalent number average molecular weight (Mn) measured by gel permeation chromatography (GPC) in the range of, for example, 2,000 to 300,000. The Mn of the vinyl polymer may be 3,000 to 200,000, 4,000 to 150,000, or 5,000 to 100,000.

[0070] In addition, according to the present production method, a polymer having a narrow molecular weight distribution (Mw / Mn) represented by the ratio of the weight average molecular weight (Mw) and the number average molecular weight (Mn) in terms of polystyrene measured by GPC can be obtained. Specifically, the molecular weight distribution (Mw / Mn) of the vinyl polymer obtained by the present production method is, for example, 3.0 or less, may be 2.5 or less, or may be 2.2 or less. In living radical polymerization, in order to maintain living properties, polymerization is generally started after all raw materials are charged into a reactor at once. In contrast, according to the present production method, even when polymerization is performed while continuously supplying at least a part of the total amount of monomers used in polymerization into a reactor, a vinyl polymer having a molecular weight distribution (Mw / Mn) of 2.0 or less can be obtained.

[0071] The vinyl polymer obtained by this production method can be used in a wide range of applications. Specifically, it can be used in a variety of applications, such as sealing materials, adhesives, pressure sensitive adhesives, paints, dispersants, industrial rubber, binders, coating agents, surfactants, etc. In addition, application fields include civil engineering and construction materials, packaging materials, automobile parts, home appliance and office automation equipment parts, medical equipment parts, electric wires, miscellaneous goods, etc. EXAMPLES

[0072] The present disclosure will be specifically described below based on examples, but the present disclosure is not limited to these examples. In the following, "parts" and "%" mean "parts by mass" and "% by mass", respectively, unless otherwise specified. The details of the analysis method for the polymers obtained in the production examples, examples, reference examples, and comparative examples are as follows.

[0073] <Molecular weight measurement> The resulting polymer was subjected to gel permeation chromatography (GPC) under the conditions described below to obtain the number average molecular weight (Mn) and weight average molecular weight (Mw) in terms of polystyrene. The molecular weight distribution (Mw / Mn) was calculated from the obtained values. Measurement conditions Column: Tosoh TSKgel SuperMultiporeHZ-M x 4 Solvent: Tetrahydrofuran Temperature: 40℃ Detector: RI Flow rate: 600μL / min

[0074] 1. Polymer production <Production Example 1> In a 100L reactor equipped with a stirring blade, a thermometer, and a condenser, S,S-dibenzyl trithiocarbonate (hereinafter also referred to as "DBTTC") (2.0 kg), 2,2'-azobis(2,4-dimethylvaleronitrile) (85 g), n-butyl acrylate (hereinafter also referred to as "nBA") (17 kg), ethyl acrylate (hereinafter also referred to as "EA") (1.2 kg), tetradecyl acrylate (hereinafter also referred to as "TDA") (4.7 kg), methyldimethoxysilylpropyl methacrylate (4.7 kg), ethyl acetate (24 kg), and trimethyl orthoacetate (hereinafter also referred to as "MOA") (6.0 kg) were charged as RAFT agents, and the mixture was thoroughly degassed by nitrogen bubbling, and the temperature was raised to 58°C to initiate polymerization. The polymerization was carried out under atmospheric pressure. After 2 hours, the temperature was raised to 70°C over 1 hour, and the reaction was continued at 70°C for another 4 hours. The reaction was then stopped by cooling to room temperature. The molecular weight of the resulting polymer a was Mn 4,300, Mw 6,000, and Mw / Mn 1.40 as determined by gel permeation chromatography (GPC) (polystyrene equivalent).

[0075] <Example 1> A 400L reactor equipped with a stirrer, a thermometer, a condenser, and a monomer mixing tank, capable of reducing the pressure inside the vessel, was charged with the polymer a (26 kg) obtained in Production Example 1, nBA (57 kg), EA (3.8 kg), TDA (15 kg), 2,2'-azobis(2-methylbutyronitrile) (hereinafter also referred to as "ABN-E") (97 g), ethyl acetate (136 kg), and MOA (9.4 kg), and was thoroughly degassed by nitrogen bubbling, and heating to 70°C was started. When the internal temperature reached approximately 60°C, the pressure inside the reactor was reduced to 43 kPa. It was confirmed that the reflux became intense when the internal temperature reached approximately 70°C. The point when the internal temperature reached 70°C was regarded as the start of polymerization, and the external temperature was kept constant at 40°C. The internal temperature was kept constant at 70°C by adjusting the degree of vacuum and refluxing. In addition, a monomer mixture solution was prepared by stirring and mixing nBA (113 kg), EA (7.6 kg) and TDA (30 kg) in a monomer mixing tank equipped with the reactor. This prepared monomer mixture solution was continuously supplied to the reactor over 4 hours 30 minutes after the start of polymerization. Three hours after the start of polymerization, the reduced pressure was released and the pressure was returned to atmospheric pressure. After the continuous supply of the monomer mixture solution was completed, a mixed solution of ABN-E (57 g) and ethyl acetate (1.0 kg) was supplied to the reactor, and the internal temperature was increased to 60°C over 30 minutes. Eight hours after the start of polymerization, the polymer solution containing triblock copolymer b in the reactor was cooled to room temperature to stop the reaction. The molecular weight of the obtained triblock copolymer b was Mn 70,200, Mw 84,900, and Mw / Mn 1.21 by GPC measurement (polystyrene equivalent).

[0076] <Reference example 1> The triblock copolymer b obtained by the polymerization in Example 1 was treated as follows. Methyldimethoxysilylpropyl methacrylate (2.1 kg), ABN-E (199 g) and MOA (316 g) were added to the polymer solution containing the triblock copolymer b obtained in Example 1, and the solution was thoroughly degassed by nitrogen bubbling, and the temperature was raised to 60°C to initiate polymerization. After 7 hours, the solution was cooled to room temperature to stop the reaction, and a solution containing a pentablock copolymer c was obtained. The molecular weight of the obtained pentablock copolymer c was Mn 76,500, Mw 98,100 and Mw / Mn 1.28 as measured by GPC (gel permeation chromatography) (polystyrene equivalent). The pentablock copolymer c has a polymer block (A) consisting of nBA, EA, TDA and methyldimethoxysilylpropyl methacrylate, and a polymer block (B) consisting of nBA, EA and TDA, and is a pentablock copolymer having a block structure of (A)-(B)-(A)-(B)-(A). From the polymerization rate, the composition ratio of the polymer block (A) to the polymer block (B) was (A) / (B) / (A) / (B) / (A)=2.4 / 43.7 / 7.8 / 43.7 / 2.4 (wt%), which means that (A) / (B) is ≒13 / 87 (wt%).

[0077] The solution containing the pentablock copolymer c was thoroughly degassed by bubbling with nitrogen, and then n-propylamine (880 g, 5 molar equivalents relative to the trithiocarbonate group of the pentablock copolymer c) was added, and the decomposition reaction of the trithiocarbonate group was initiated in a thermostatic bath at 40°C. After 5 hours, the reaction was stopped by cooling to room temperature, and a solution containing the triblock copolymer d was obtained. The resulting solution was vacuum dried, and the triblock copolymer d was collected.

[0078] The obtained triblock copolymer d is a triblock copolymer having a polymer block (A) consisting of nBA, EA, TDA, and methyldimethoxysilylpropyl methacrylate, and a polymer block (B) consisting of nBA, EA, and TDA, and has a block structure of (A)-(B)-(A). 1From the H-NMR measurement, it was confirmed that the peak (4.8 ppm) of hydrogen bonded to the carbon adjacent to the trithiocarbonate group observed in the pentablock copolymer c disappeared in the triblock copolymer d, and peaks (3.3 ppm, 2.9 ppm) derived from the molecular structure (terminal molecular structure represented by the following formula (3)) due to the Michael addition with the residual acrylate compound appeared. From this result, it can be said that the obtained triblock copolymer is a Michael adduct of the thiol formed by decomposing the trithiocarbonate group of the pentablock copolymer c with n-propylamine and the residual acrylate compound contained in the block copolymer c. The molecular weight of the triblock copolymer d was Mn 44,600, Mw 59,500, and Mw / Mn 1.33. In addition, the number of crosslinkable functional groups per molecule of the polymer block (A) was calculated to be 3.0 on average from the amount of methyldimethoxysilylpropyl methacrylate introduced per RAFT agent. [ka] (In formula (3), R represents an alkyl group.)

[0079] <Comparative Example 1> A 400L reactor equipped with a stirrer, a thermometer, and a condenser, capable of reducing the pressure inside the vessel, was charged with the polymer a (26 kg) obtained in Production Example 1, nBA (170 kg), EA (11 kg), TDA (45 kg), ABN-E (190 g), ethyl acetate (37 kg), and MOA (9.4 kg), and was thoroughly degassed by nitrogen bubbling, and the temperature was started to be raised to 60°C. When the internal temperature of the reactor reached about 50°C, the pressure inside the reactor was reduced to 17 kPa. It was confirmed that the reflux became intense when the internal temperature of the reactor reached about 60°C. The point at which the internal temperature of the reactor reached 60°C was regarded as the start of polymerization, and the external temperature was kept constant at 40°C. The degree of reduction in pressure was adjusted to keep the internal temperature constant at 60°C. However, even when the valve of the vacuum line was fully opened, the set degree of reduction in pressure could not be maintained, the polymerization solvent was reduced, and the internal temperature of the reactor gradually increased. When the internal temperature of the reactor reached 74° C., an oxygen / nitrogen mixed gas with an oxygen concentration of 5% was blown in to stop the reaction.

[0080] <Comparative Example 2> A 400L reactor equipped with a stirrer, a thermometer, a condenser, and a monomer mixing tank was charged with the polymer a (26 kg) obtained in Production Example 1, nBA (57 kg), EA (3.8 kg), TDA (15 kg), ABN-E (97 g), ethyl acetate (136 kg), and MOA (9.4 kg), and the contents were thoroughly degassed by nitrogen bubbling, and the temperature was raised to 70°C. The polymerization was started when the internal temperature reached 70°C, and the external temperature was lowered to maintain the internal temperature at 70°C. The polymerization was carried out under atmospheric pressure. A monomer mixture solution was prepared by stirring and mixing nBA (113 kg), EA (7.6 kg), and TDA (30 kg) in a monomer mixing tank equipped with the reactor, and 30 minutes after the start of polymerization, an attempt was made to continuously supply this prepared monomer mixture solution to the reactor over a period of 4 hours. However, the external temperature could not be adjusted to keep up, and the internal temperature of the reactor gradually rose. When the internal temperature of the reactor reached 78°C, an oxygen / nitrogen mixed gas with an oxygen concentration of 5% was blown in to stop the reaction.

[0081] 2.Results In the production of a triblock copolymer by living radical polymerization, in Example 1, a triblock copolymer was produced stably in a short time by polymerization of monomers under reduced pressure and under a state where the polymerization solvent was boiling (reduced pressure boiling point polymerization). In addition, the heat of polymerization could be efficiently removed by utilizing the heat removal from the reactor due to the difference in temperature between inside and outside the reactor and the heat removal due to the latent heat in the evaporation of the polymerization solvent (ethyl acetate). This is because, when polymerizing polymer a, nBA, EA, and TDA to produce triblock copolymer b, the boiling point of the initial reaction solution is lowered by continuously dropping a part of the monomers (nBA, EA, and TDA) into the polymerization solvent, and boiling point polymerization can be performed without reducing the pressure in the reactor so much, which allows the polymerization solvent (ethyl acetate) to be efficiently recovered by a condenser, and the concentration of the polymerization solvent in the reactor can be maintained during the polymerization reaction.

[0082] On the other hand, in Comparative Example 1, when polymer a, nBA, EA and TDA were polymerized to produce a triblock copolymer, all the monomers (nBA, EA and TDA) were initially charged into the reactor all at once to carry out reduced pressure boiling point polymerization, but the temperature inside the reactor could not be maintained at a constant temperature, and the triblock copolymer could not be produced. This is believed to be due to the fact that the boiling point of the reaction solution was high, and the pressure inside the reactor was lowered to less than 20 kPa to carry out boiling point polymerization, so the polymerization solvent (ethyl acetate) could not be fully recovered by the condenser, the concentration of the polymerization solvent in the reactor gradually decreased, and the temperature inside the reactor increased with the increase in the boiling point of the reaction solution.

[0083] In addition, in Comparative Example 2, when polymerizing polymer a, nBA, EA, and TDA to produce a triblock copolymer, an attempt was made to carry out polymerization under atmospheric pressure by continuously dropping a portion of the monomers (nBA, EA, and TDA) to produce a triblock copolymer. However, since the heat generated in the early stage of the polymerization was large, the heat could not be removed from the reactor by the difference between the inside and outside temperature alone, and the internal temperature of the reactor rose, making it impossible to carry out stable polymerization.

Claims

1. A method for producing a vinyl polymer by living radical polymerization, comprising the steps of: The method includes a polymerization step of placing a monomer and a polymerization solvent in a reactor and polymerizing the monomer in the polymerization solvent, During at least a part of the polymerization step, polymerization is carried out while continuously supplying at least a part of the total amount of monomers to be used in the polymerization in the polymerization step into the reactor in a state in which the polymerization solvent is boiling; wherein, in the polymerization step, polymerization is carried out by maintaining the pressure in the reactor lower than atmospheric pressure during at least a part of a period during which the monomers are continuously supplied into the reactor.

2. 2. The method for producing a vinyl polymer according to claim 1, wherein in the polymerization step, polymerization is carried out by maintaining a pressure in the reactor at 20 kPa or more and 70 kPa or less during at least a part of a period during which the monomers are continuously supplied into the reactor.

3. The method for producing a vinyl polymer according to claim 1 or 2, wherein the polymerization solvent has a boiling point lower than a boiling point of the monomer.

4. The method for producing a vinyl polymer according to any one of claims 1 to 3, wherein the polymerization solvent has a boiling point of 50°C or more and 100°C or less at atmospheric pressure.

5. The method for producing a vinyl polymer according to any one of claims 1 to 4, wherein in the polymerization step, the polymerization solvent is refluxed.

6. The method for producing a vinyl polymer according to any one of claims 1 to 5, wherein the monomer comprises a (meth)acrylic monomer.

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