JP7631791B2 - Method for producing vinyl polymer - Google Patents

Description

The present invention relates to a method for producing vinyl polymers, and in particular to a technology for producing vinyl polymers by reversible addition-fragmentation chain transfer living radical polymerization.

As living radical polymerization methods, various polymerization methods are known, such as reversible addition-fragmentation chain transfer polymerization (RAFT method), nitroxy radical method (NMP method), atom transfer radical polymerization (ATRP method), polymerization method using organotellurium compounds (TERP method), polymerization method using organoantimony compounds (SBRP method), polymerization method using organobismuth compounds (BIRP method), and iodine transfer polymerization. Among these, the RAFT method, the NMP method, and the ATRP method are used industrially from the viewpoint of polymerization controllability and ease of implementation. In particular, the RAFT method is attracting attention as a metal-free polymerization method that can be applied to the widest range of vinyl monomers.

Vinyl polymers obtained by the RAFT method (hereinafter also referred to as "RAFT polymers") can have a problem with coloration due to the thiocarbonylthio groups derived from the RAFT agent. Therefore, studies have been conducted on post-treatment of the RAFT polymer to remove the thiocarbonylthio groups derived from the RAFT agent from the RAFT polymer (see, for example, Patent Documents 1 to 3).

Patent Document 1 discloses that sponge nickel is brought into contact with a RAFT polymer, and the thiocarbonylthio groups of the RAFT polymer are replaced with hydrogen atoms to remove the thiocarbonylthio groups of the RAFT polymer. Patent Document 2 discloses that thiocarbonylthio groups derived from a RAFT agent are removed by treating the RAFT polymer with an azo compound or peroxide. Patent Document 3 discloses that thiocarbonylthio groups of a RAFT polymer are removed by treating the RAFT polymer with an amine compound. Of these, the method using an amine compound is easy and quantitative, and can be said to be industrially useful.

JP 2017-197649 A International Publication No. 2011/093401 International Publication No. 2013/086585

When industrially producing polymers, it is common to recover the solvent used in the polymerization and reuse the recovered solvent as the polymerization solvent. However, the inventors of the present invention have found that when a vinyl polymer is produced by the RAFT method, the resulting vinyl polymer is treated to remove thiocarbonylthio groups by reacting it with an amine compound, and the solvent recovered after the treatment is reused as the polymerization solvent, the molecular weight distribution of the resulting vinyl polymer becomes broad.

The present invention has been made in view of the above circumstances, and its purpose is to provide a method for producing a vinyl polymer that can produce a vinyl polymer with a sufficiently narrow molecular weight distribution by reacting an amine compound with a vinyl polymer obtained by the RAFT method and then reusing the recovered solvent for polymerization.

The present inventors have speculated that when the recovered solvent recovered after the reaction of a vinyl polymer having a thiocarbonylthio group obtained by the RAFT method with an amine compound is reused for polymerization, the molecular weight distribution of the vinyl polymer obtained by the polymerization becomes broad due to the amine compound remaining unreacted in the recovered solvent. Based on this speculation, the present inventors have conducted extensive research and have completed the present invention. Specifically, the present invention provides the following means.

[1] A method for producing a vinyl polymer, comprising: a polymerization step of polymerizing monomers in a polymerization solvent by a reversible addition-fragmentation chain transfer living radical polymerization method to obtain a polymer solution (S1) containing a vinyl polymer (P1) having a thiocarbonylthio group; and a reaction step of reacting the thiocarbonylthio group of the vinyl polymer (P1) with at least one amine compound selected from the group consisting of primary amines and secondary amines in the polymer solution (S1) to obtain a polymer solution (S2) containing a vinyl polymer (P2), in which the polymerization step is carried out using a solvent (S3) containing a recovered solvent recovered from the polymer solution (S2) after the reaction between the vinyl polymer (P1) and the amine compound as the polymerization solvent, and the content of the amine compound in the solvent (S3) is 0.025 mmol/g or less.

[2] The method for producing a vinyl polymer according to [1] above, wherein the vinyl polymer (P2) has a crosslinkable silyl group.
[3] The method for producing a vinyl polymer according to [2] above, wherein the content of alcohol in the solvent (S3) is 5,000 ppm or less.
[4] The method for producing a vinyl polymer according to any one of [1] to [3] above, wherein the recovered solvent is obtained by heating a solvent remaining after separating the vinyl polymer (P2) from the polymer solution (S2).
[5] The method for producing a vinyl polymer according to [4] above, wherein the recovered solvent is a residue obtained by simple distillation of the solvent remaining after separating the vinyl polymer (P2) from the polymer solution (S2).
[6] The method for producing a vinyl polymer according to any one of [1] to [5] above, wherein the vinyl polymer (P2) has a molecular weight distribution (Mw/Mn) of 1.9 or less.
[7] The method for producing a vinyl polymer according to any one of the above [1] to [6], wherein the vinyl polymer (P1) is a block copolymer having two or more polymer blocks.

According to the present invention, even when the solvent recovered after the vinyl polymer obtained by the RAFT method is reacted with an amine compound is reused for polymerization, a vinyl polymer having a sufficiently narrow molecular weight distribution can be obtained. Therefore, according to the present invention, the productivity of the production of vinyl polymers having a narrow molecular weight distribution can be increased.

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.

The method for producing a vinyl polymer of the present invention (hereinafter also referred to as "the present production method") produces a vinyl polymer by reversible addition-fragmentation chain transfer living radical polymerization (RAFT) method, and specifically includes the following polymerization steps and reaction steps:
A polymerization step of polymerizing monomers in a polymerization solvent to obtain a polymer solution (S1) containing a vinyl polymer (P1) having a thiocarbonylthio group.
A reaction step of reacting, in a polymer solution (S1), a thiocarbonylthio group contained in the vinyl polymer (P1) with at least one amine compound selected from the group consisting of primary amines and secondary amines to obtain a polymer solution (S2) containing a vinyl polymer (P2).

In this production method, in the polymerization step, polymerization is carried out using a solvent (S3) that contains a recovered solvent recovered after the reaction between the thiocarbonylthio group of the vinyl polymer (P1) and the amine compound as the polymerization solvent. The content of the amine compound in the solvent (S3) is 0.025 mmol/g or less. The polymerization step and the reaction step in this production method are described in detail below.

<Polymerization step>
This step is a step of obtaining a polymer solution (S1) containing a vinyl polymer (P1) by the RAFT method. In the RAFT method, polymerization proceeds via 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 are preferably used because of their excellent polymerization controllability of (meth)acrylic acid ester compounds, 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.

In polymerization by the RAFT method, known free radical polymerization initiators such as azo compounds, organic peroxides, and persulfates can be used as radical polymerization initiators. Among these, azo compounds are preferred because they are safe to handle and less likely to cause side reactions during radical polymerization. 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). As the radical polymerization initiator, one type may be used alone, or two or more types may be used in combination.

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, and more preferably 0.4 mol or less, per 1 mol of RAFT agent. Furthermore, 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, and more preferably 0.05 mol or more, per 1 mol of RAFT agent. The amount of radical polymerization initiator used per 1 mol of RAFT agent is preferably 0.01 to 0.5 mol, and more preferably 0.05 to 0.4 mol.

When using the RAFT method, the polymerization reaction may be carried out in the presence of a chain transfer agent, such as an alkylthiol compound having 2 to 20 carbon atoms, if necessary. Also, a dehydrating agent, such as trimethyl orthoacetate or triethyl orthoacetate, may be mixed into the reaction system if necessary. By adding a dehydrating agent to the reaction system, it is possible to suppress the crosslinking reaction from proceeding during polymerization.

The monomer used in the polymerization is not particularly limited, and various vinyl monomers can be used. The monomer used in the polymerization preferably contains a (meth)acrylic monomer, since vinyl polymers can be produced relatively easily by the RAFT method and there is a high degree of freedom in the selection of monomers.

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 = ^CR1 -C(=O)O-( ^R2O ) _n - ^R3 ...(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 ³ represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms, and n represents an integer of 1 to 100.)

(Meth)acrylic acid alkyl ester compound 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.

Considering the fluidity of the vinyl polymer obtained by this production method, among these, the (meth)acrylic acid alkyl ester compound can preferably be 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. When a (meth)acrylic acid alkyl ester compound is used as the monomer, the (meth)acrylic acid alkyl ester compound 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.

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.

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.

Compounds represented by formula (1) When n in formula (1) is 1, the compounds represented by formula (1) have an oxyalkylene structure such as an oxyethylene chain, an oxypropylene chain, and an oxybutylene chain. Specific examples of compounds in which n in formula (1) is 1 (i.e., (meth)acrylic acid alkoxyalkyl ester compounds) 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.

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, and a polyoxybutylene chain. When n is 2 or more, two or more ^R2 in the above formula (1) 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.

Specific examples of compounds 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.

For example, when a vinyl polymer with 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 a (meth)acrylic acid alkyl ester compound having an alkyl group with 2 to 18 carbon atoms, and even more preferably a (meth)acrylic acid alkyl ester compound having an alkyl group with 4 to 18 carbon atoms. In addition, 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 it can be made into a polymer with excellent mechanical strength and fluidity.

The amount of the (meth)acrylic acid alkyl ester compound used is, for example, 40% by mass or more, preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, and even more preferably 90% by mass or more, based on the total amount of monomers used in the polymerization.

As the monomer, 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 of these, or two or more of them.

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, p-n-butylstyrene, p-isobutylstyrene, p-t-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.

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.

Maleimide Compounds Specific examples of maleimide compounds include maleimide and N-substituted maleimide compounds. Examples of N-substituted maleimide compounds include N-alkyl-substituted maleimide compounds such as N-methylmaleimide, N-ethylmaleimide, N-n-propylmaleimide, N-isopropylmaleimide, N-n-butylmaleimide, N-isobutylmaleimide, N-tert-butylmaleimide, N-pentylmaleimide, N-hexylmaleimide, N-heptylmaleimide, N-octylmaleimide, N-laurylmaleimide, and N-stearylmaleimide; N-cyclopentylmaleimide, N-ethylmaleimide, N-n-propylmaleimide, N-isopropylmaleimide, N-n-butylmaleimide, N-isobutylmaleimide, N-tert-butylmaleimide, N-pentylmaleimide, N-hexylmaleimide, N-heptylmaleimide, N-octylmaleimide, N-laurylmaleimide, and N-stearylmaleimide; N-cycloalkyl-substituted maleimide compounds such as N-cycloalkylmaleimide and 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.

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.

Amide Group-Containing Vinyl Compounds Specific examples of amide group-containing vinyl compounds include (meth)acrylamide, (meth)acrylamide derivatives, and N-vinylamide monomers. Of these, specific examples of (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 N-vinylamide monomers include N-vinylacetamide, N-vinylformamide, and N-vinylisobutylamide.

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.

- Vinyl monomer having crosslinkable functional group 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. Of these, the crosslinkable functional group to be introduced into the vinyl polymer (P1) is preferably a crosslinkable silyl group. A vinyl polymer having a crosslinkable silyl group 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 the vinyl polymer (P1).

Specific examples of crosslinkable silyl groups include alkoxysilyl groups and halogenosilyl groups. Among these, alkoxysilyl groups are preferred because the reactivity is easy to control. Examples of such groups include trimethoxysilyl groups, methyldimethoxysilyl groups, dimethylmethoxysilyl groups, triethoxysilyl groups, methyldiethoxysilyl groups, and dimethylethoxysilyl groups.

Examples of vinyl monomers having a crosslinkable functional group include crosslinkable silyl group-containing vinyl compounds, unsaturated carboxylic acids, unsaturated acid anhydrides, hydroxyl 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.

Examples of crosslinkable silyl group-containing vinyl compounds include vinyl silanes such as vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethyldimethoxysilane, and vinyldimethylmethoxysilane; alkoxysilyl group-containing (meth)acrylic acid esters such as trimethoxysilylpropyl (meth)acrylate, triethoxysilylpropyl (meth)acrylate, methyldimethoxysilylpropyl (meth)acrylate, and dimethylmethoxysilylpropyl (meth)acrylate; alkoxysilyl group-containing vinyl ethers such as trimethoxysilylpropyl vinyl ether; and alkoxysilyl group-containing vinyl esters such as vinyl trimethoxysilylundecanoate.

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

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), compounds in which R ³ is a hydrogen atom are also vinyl-based monomers having a crosslinkable functional group.

Examples of epoxy group-containing vinyl compounds include glycidyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, and 3,4-epoxycyclohexylmethyl (meth)acrylate.

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. 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, from the viewpoint of ensuring the flexibility of the resulting vinyl polymer.

When a block copolymer having two or more polymer blocks is obtained as the vinyl polymer (P1) by this polymerization process, a polymer having a thiocarbonylthio group may be used as a raw material together with the monomer. For example, when a block copolymer having a polymer block (A) and a polymer block (B) is produced, a polymer (hereinafter also referred to as "polymer (a)") that constitutes polymer block (A) together with the monomer that constitutes polymer block (B) and has a thiocarbonylthio group 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-dibenzyl trithiocarbonate, 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.

The polymerization reaction is carried out in a polymerization solvent known in living radical polymerization. Various solvents can be used as the polymerization solvent, such as saturated hydrocarbon compounds, aromatic compounds, ester compounds, ketone compounds, ether compounds, nitrile compounds, water, etc.

Specific examples of polymerization solvents include saturated hydrocarbon compounds such as hexane, heptane, and cyclohexane; aromatic compounds such as benzene, toluene, xylene, and anisole; ester compounds such as methyl acetate, ethyl acetate, propyl acetate, butyl acetate, ethyl formate, and methyl propionate; ketone compounds such as acetone, methyl ethyl ketone, and cyclohexanone; ether compounds such as tetrahydrofuran; and nitrile compounds such as acetonitrile. Other polymerization solvents include dimethylformamide, dimethylsulfoxide, and water. 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.

In this production method, the polymerization is carried out by reusing the recovered solvent recovered after the reaction of the vinyl polymer (P1) having a thiocarbonylthio group with the amine compound. Details of the recovered solvent will be described later.

The amount of polymerization solvent used is preferably 5 to 200 parts by mass, and more preferably 10 to 100 parts by mass, per 100 parts by mass of the total amount of monomers used in the polymerization. Using 100 parts by mass or less of polymerization solvent is preferable because it can sufficiently suppress chain transfer to the polymerization solvent and achieve a high polymerization rate in a short period of time. Using 10 parts by mass or more of polymerization solvent is also preferable because it can efficiently remove polymerization heat and suppress an increase in reaction temperature.

In the polymerization, the reaction temperature and reaction time can be appropriately set according to the type of monomer and polymerization solvent used. The reaction temperature is, for example, 40°C or higher and 100°C or lower, preferably 45°C or higher and 90°C or lower, and more preferably 50°C or higher and 80°C or lower. A reaction temperature of 40°C or higher is preferable in that the polymerization reaction can proceed smoothly, and a reaction temperature of 100°C or lower is preferable in that side reactions can be suppressed and restrictions on the initiator and polymerization solvent that can be used are relaxed. The reaction time is, for example, 1 hour or higher and 48 hours or lower, and preferably 2 hours or higher and 24 hours or lower. By such polymerization, a polymer solution (S1) containing a vinyl polymer (P1) having a thiocarbonylthio group is obtained.

<Reaction process>
In this step, the polymer solution (S1) containing the vinyl polymer (P1) obtained by the polymerization step is used, and the thiocarbonylthio group of the vinyl polymer (P1) is reacted with an amine compound as a nucleophilic agent in the polymer solution (S1), thereby removing the thiocarbonylthio group of the vinyl polymer (P1) derived from the RAFT agent.

（式（２）中、Ｒは、ビニル系重合体の分子鎖を構成する単量体に含まれるアクリル酸エステル化合物からアクリロイルオキシ基を取り除いた残基を表す。） When the thiocarbonylthio group of the vinyl polymer (P1) is reacted with an amine compound, a thiol group is generated from the thiocarbonylthio group of the vinyl polymer (P1) by this reaction, and the generated thiol group reacts with the monomer remaining unreacted in the polymer solution (S1) (more specifically, Michael addition reaction). When an acrylic acid ester compound is used as a monomer in the above polymerization step, a vinyl polymer having a terminal structure represented by the following formula (2) can be obtained as the vinyl polymer (P2).

(In formula (2), R represents a residue obtained by removing an acryloyloxy group from an acrylic ester compound contained in a monomer constituting the molecular chain of a vinyl polymer.)

For example, in the above polymerization step, when S,S-dibenzyl trithiocarbonate is used as the RAFT agent and a triblock copolymer is obtained as the vinyl polymer (P1), the vinyl polymer (P2) can be obtained as a diblock copolymer. In addition, when S,S-dibenzyl trithiocarbonate is used as the RAFT agent and a pentablock copolymer is obtained as the vinyl polymer (P1), the vinyl polymer (P2) can be obtained as a triblock copolymer. In addition, when 1,4-bis(alkylsulfanylthiocarbonylsulfanylmethyl)benzene is used as the RAFT agent and a tetrablock copolymer is obtained as the vinyl polymer (P1), the vinyl polymer (P2) can be obtained as a tetrablock copolymer.

In this step, at least one amine compound selected from the group consisting of primary amines and secondary amines (hereinafter also referred to as "amine compound (A)") is used as the nucleophile. As the amine compound (A), known primary amines and/or secondary amines can be used, and examples thereof include primary amines such as methylamine, ethylamine, n-propylamine, n-butylamine, n-hexylamine, n-octylamine, and benzylamine; and secondary amines such as N-ethylmethylamine, N-methylpropylamine, and piperidine. The molecular weight of the amine compound (A) is preferably 150 or less, more preferably 110 or less, and even more preferably 60 or less, in terms of ease of removing unreacted nucleophile.

The amount of the amine compound (A) used is preferably 2 to 90 molar equivalents relative to the thiocarbonylthio group derived from the RAFT agent in the vinyl polymer (P1). From the viewpoint of reaction efficiency, the amount of the amine compound (A) used is preferably 2.5 molar equivalents or more relative to the thiocarbonylthio group derived from the RAFT agent, more preferably 3 molar equivalents or more, and even more preferably 3.5 molar equivalents or more. The amount of the amine compound (A) used is preferably 75 molar equivalents or less relative to the thiocarbonylthio group derived from the RAFT agent, more preferably 60 molar equivalents or less, and even more preferably 50 molar equivalents or less. By using the amine compound (A) in an amount of 75 molar equivalents or less, the influence of odor due to unreacted amine compound (A) can be reduced, and when polymerization is performed by reusing the recovered solvent, the molecular weight distribution of the obtained vinyl polymer can be suppressed from becoming broad.

As the reactor used in the reaction of the thiocarbonylthio group with the amine compound (A), known reactors such as a batch reactor and a tubular reactor can be used. Of these, a batch reactor is preferred because there is less risk of clogging, which is a problem in tubular reactors. The reaction temperature is preferably 10°C or higher, more preferably 15°C or higher, and even more preferably 25°C or higher, from the viewpoint of reaction efficiency. In addition, in order to prevent side reactions (e.g., nucleophilic reactions to the polymer main chain, etc.), the reaction temperature is preferably 80°C or lower, more preferably 60°C or lower, and even more preferably 50°C or lower. The reaction pressure is usually normal pressure, but may be increased or decreased as necessary. The reaction time is preferably 1 hour or more, more preferably 2 hours or more, and even more preferably 3 hours or more, from the viewpoint of reaction efficiency. In addition, in order to suppress side reactions such as nucleophilic reactions to the polymer main chain, it is preferably 48 hours or less, more preferably 36 hours or less, and even more preferably 24 hours or less.

According to this production method, since the RAFT method is used as the polymerization method, the synthesis of a block copolymer can be carried out relatively easily, and a block copolymer having a narrow molecular weight distribution can be obtained. When the vinyl polymer (P2) obtained by this production method is a block copolymer having two or more polymer blocks, the number of blocks, the block structure, etc. are not particularly limited.

<Solvent recovery and reuse>
The reaction between the thiocarbonylthio group of the vinyl polymer (P1) and the amine compound (A) in the above reaction step gives a polymer solution (S2) containing the vinyl polymer (P2). By subjecting the obtained polymer solution (S2) to a known solvent removal treatment, the vinyl polymer (P2) can be isolated and the solvent can be recovered. In this production method, the recovered solvent recovered after the reaction between the thiocarbonylthio group of the vinyl polymer (P1) and the amine compound (A) is reused, and in a new polymerization step to be carried out thereafter, polymerization is carried out using the recovered solvent as at least a part of the polymerization solvent.

The content of the amine compound (A) in the recovered solvent is preferably 0.025 mmol/g or less. When the content of the amine compound (A) in the recovered solvent is within the above range, the inhibition of polymer elongation due to the reaction of the thiocarbonylthio group derived from the RAFT agent in the elongated polymer with the amine compound (A) during polymerization or the reaction of the monomer with the amine compound (A) can be suppressed in the polymerization using the recovered solvent. This is preferable in that the molecular weight distribution of the vinyl polymer (P2) obtained by this production method can be sufficiently narrowed. From this viewpoint, the content of the amine compound (A) in the recovered solvent is more preferably 0.022 mmol/g or less, even more preferably 0.020 mmol/g or less, and even more preferably 0.018 mmol/g or less. In this specification, the content of the amine compound (A) in the solvent is a value measured by gas chromatography (GC). For details of the measurement method, follow the method described in the examples below.

The solvent obtained by separating the vinyl monomer (P2) from the polymer solution (S2) (hereinafter also referred to as the "separated solvent") may be reused as a recovered solvent in the subsequent polymerization reaction. The separated solvent may also be subjected to a treatment to reduce the content of the amine compound (A) (hereinafter also referred to as the "amine reduction treatment"), and then reused as a recovered solvent in the subsequent polymerization reaction. Of these, when the polymerization solvent is reused to perform polymerization, it is preferable to reuse the solvent after the amine reduction treatment on the separated solvent as the recovered solvent, since this can reduce the amount of the amine compound (A) in the reaction system as much as possible.

The specific method of the amine reduction treatment is not particularly limited, but it is preferable to use a method of heating the separation solvent. The heating method is preferable because it can reduce the amount of the amine compound (A) in the separation solvent easily and in a short time. The separation solvent can be heated, for example, using a heating jacket or a heat exchanger provided on the outside of the treatment vessel. The content of the amine compound (A) in the separation solvent can be adjusted by adjusting the temperature and time during heating. The temperature during the heating treatment depends on the type of solvent, etc., but is, for example, 30 to 65°C, preferably 35 to 60°C. The heating treatment time is, for example, 12 to 120 hours, preferably 24 to 72 hours.

As a method for reducing the amine compound (A) by heating the separation solvent, a method for subjecting the separation solvent to simple distillation may be adopted. When simple distillation is used, the content of the amine compound (A) in the separation solvent can be adjusted by adjusting the distillation rate and the number of times the simple distillation is performed.

Here, the recovered solvent may contain, for example, alcohol generated by hydrolysis of unreacted monomers or alcohol generated by hydrolysis of ester bonds in the copolymer. In order to reduce the influence of the presence of alcohol in the reaction system, the content of alcohol in the recovered solvent is preferably 5,000 ppm or less. If the content of alcohol in the recovered solvent is within the above range, it is preferable in that the influence of the presence of alcohol, for example, the reduction in the dehydration effect of the dehydrating agent mixed in the reaction system, can be effectively suppressed. From this viewpoint, the content of alcohol compounds in the recovered solvent is more preferably 3,000 ppm or less, even more preferably 2,000 ppm or less, even more preferably 1,500 ppm or less, and even more preferably 1,000 ppm or less. In this specification, the content of alcohol in the solvent is a value measured by gas chromatography (GC). For details of the measurement method, follow the method described in the examples below.

In the polymerization step when the recovered solvent is reused, a solvent containing the recovered solvent (hereinafter also referred to as "solvent (S3)") may be used as at least a part of the polymerization solvent, and the proportion of the recovered solvent contained in the polymerization solvent is not particularly limited. In other words, when the recovered solvent is reused to carry out polymerization, the polymerization may be carried out using a part of the polymerization solvent used in the polymerization as the recovered solvent, or the polymerization may be carried out using all of the polymerization solvent as the recovered solvent. From the viewpoint of increasing the productivity of the vinyl polymer by reusing the polymerization solvent, the proportion of the recovered solvent contained in the solvent (S3) is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, and even more preferably 60% by mass or more.

The content of the amine compound (A) in the solvent (S3) is 0.025 mmol/g or less. If the amount of the amine compound (A) contained in the solvent (S3) exceeds 0.025 mmol/g, the polymer elongation is easily inhibited by the reaction between the thiocarbonylthio group in the elongated polymer and the amine compound (A) or the reaction between the monomer and the amine compound (A), and the molecular weight distribution of the vinyl polymer (P2) tends to become broad. From this viewpoint, the content of the amine compound (A) in the solvent (S3) is more preferably 0.022 mmol/g or less, even more preferably 0.020 mmol/g or less, even more preferably 0.018 mmol/g or less, even more preferably 0.016 mmol/g or less, and even more preferably 0.015 mmol/g or less.

The alcohol content in the solvent (S3) is preferably 5,000 ppm or less, more preferably 3,000 ppm or less, even more preferably 2,000 ppm or less, even more preferably 1,500 ppm or less, even more preferably 1,000 ppm or less, and even more preferably 800 ppm or less.

According to this production method, even when a block copolymer having two or more polymer blocks is produced using a recovered solvent, a polymer having a sufficiently narrow molecular weight distribution can be obtained. For example, in the polymerization step, a (A)-(B)-(A)-(B)-(A) pentablock consisting of polymer block (A)/polymer block (B)/polymer block (A)/polymer block (B)/polymer block (A) is produced as a vinyl polymer (P1) by a RAFT method using a bifunctional RAFT agent, and then in the reaction step, a (A)-(B)-(A) triblock consisting of polymer block (A)/polymer block (B)/polymer block (A) is produced as a vinyl polymer (P2) by reacting the pentablock as the vinyl polymer (P1) with an amine compound (A). The target product can be efficiently obtained by producing the vinyl polymer by a method including the following three steps (first to third polymerization steps).

That is, first, in the first polymerization step, the polymer block (A) is obtained using the monomers constituting the polymer block (A). Then, in the second polymerization step, the monomers constituting the polymer block (B) are 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, the monomers constituting the polymer block (A) are 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 producing the vinyl polymer (P1) by such a three-step process, the polymerization can be carried out using the recovered solvent as at least a part of the polymerization solvent in any of the first to third polymerization steps. At this time, the polymerization may be carried out using the recovered solvent in any one or two steps of the first to third polymerization steps, or the polymerization may be carried out using the recovered solvent in all steps.

<Molecular weight characteristics of polymers produced using recovered solvent>
When a vinyl polymer (P2) is obtained by polymerization using the recovered solvent as at least a part of the polymerization solvent according to the present production method, the polystyrene-equivalent number average molecular weight (Mn) of the obtained vinyl polymer (P2) measured by gel permeation chromatography (GPC) is, for example, in the range of 2,000 to 300,000. The Mn of the vinyl polymer (P2) may be 3,000 to 200,000, 4,000 to 150,000, or 5,000 to 100,000.

In addition, according to this production method, even when polymerization is performed using the recovered solvent, a polymer having a sufficiently narrow molecular weight distribution (Mw/Mn) can be obtained as the vinyl polymer (P2). Specifically, when polymerization is performed using the recovered solvent as at least a part of the polymerization solvent to obtain the vinyl polymer (P2) according to this production method, the molecular weight distribution (Mw/Mn) of the obtained vinyl polymer (P2), which is expressed by the ratio of the weight average molecular weight (Mw) and the number average molecular weight (Mn) in terms of polystyrene measured by GPC, is, for example, 2.0 or less, may be 1.9 or less, may be 1.8 or less, or may be 1.7 or less. According to this production method, even when polymerization is performed by reusing the recovered solvent, a vinyl polymer having a molecular weight distribution (Mw/Mn) of less than 2.0, preferably 1.9 or less, can be obtained.

The vinyl polymers obtained by this manufacturing method can be used in a wide range of applications. Specifically, they can be used in a variety of applications, such as sealants, adhesives, pressure sensitive adhesives, paints, dispersants, industrial rubber, binders, coating agents, and surfactants. Other application areas include civil engineering and construction materials, packaging materials, automobile parts, home appliance and office automation equipment parts, medical equipment parts, electric wires, and miscellaneous goods.

The present disclosure will be specifically explained 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. Details of the analysis methods for the polymers obtained in the synthesis examples, production examples, examples, and comparative examples are as follows.

<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°C
Detector: RI
Flow rate: 600μL/min

<Measurement of the Content of Amine Compounds and Alcohol in Recovered Solvent>
The obtained polymer was subjected to gas chromatography (GC) measurement under the conditions described below to obtain the n-propylamine content and the methanol content in the recovered solvent.
Measurement conditions: Equipment: Shimadzu GC-1700
Column: InterCap for Amines 0.32 mm ID x 30 m
Inlet temperature: 180℃
Detector temperature: 250°C
Column temperature: 50°C (5 min) → 10°C/min → 260°C (5 min)
Detector: FID
Solvent: Tetrahydrofuran

1. Synthesis Example (Synthesis Example 1: Production of Polymer a)
In a 250 mL flask equipped with a stirrer, a thermometer, and a condenser, S,S-dibenzyl trithiocarbonate (hereinafter also referred to as "DBTTC") (7.1 g) as a RAFT agent, 2,2'-azobis(2-methylbutyronitrile) (hereinafter also referred to as "ABN-E") (0.47 g), n-butyl acrylate (hereinafter also referred to as "nBA") (62 g), ethyl acrylate (hereinafter also referred to as "EA") (4.2 g), tetradecyl acrylate (hereinafter also referred to as "TDA") (17 g), methyldimethoxysilylpropyl methacrylate (17 g), and trimethyl orthoacetate (hereinafter also referred to as "MOA") (5.2 g) as a dehydrating agent were charged, thoroughly degassed by nitrogen bubbling, and polymerization was initiated in a thermostatic bath at 60 ° C. After 7 hours, the reaction was stopped by cooling to room temperature (25 ° C.). The molecular weight of the obtained polymer a was Mn 4,200, Mw 6,800, and Mw/Mn 1.62 as measured by GPC (gel permeation chromatography) (converted into polystyrene).

2. Production Examples (Production Example 1: Production of triblock copolymer b-1)
A 2 L flask equipped with a stirrer, a thermometer, and a condenser was charged with the polymer a (62 g) obtained in Synthesis Example 1, nBA (706 g), EA (47 g), TDA (188 g), ABN-E (0.64 g), ethyl acetate (197 g) as a polymerization solvent, and MOA (49 g) as a dehydrating agent, and the mixture was thoroughly degassed by nitrogen bubbling, and polymerization was initiated in a thermostatic bath at 60° C. After 7 hours, the mixture was cooled to room temperature to terminate the reaction, and a solution containing triblock copolymer b'-1 was obtained.
Methyldimethoxysilylpropyl methacrylate (9.3 g), ABN-E (0.76 g), and MOA (1.5 g) were charged into the solution containing the triblock copolymer b'-1, and the solution was thoroughly degassed by nitrogen bubbling, and polymerization was initiated in a thermostatic bath at 60°C. Copolymerization of unreacted monomers (nBA, EA, and TDA) during the production of the triblock copolymer b'-1 and newly added methyldimethoxysilylpropyl methacrylate proceeded. After 7 hours, the solution was cooled to room temperature to stop the reaction, and a solution containing a pentablock copolymer c-1 was obtained.
The pentablock copolymer c-1 is a pentablock copolymer having a block structure of (A)-(B)-(A)-(B)-(A), which includes a polymer block (A) consisting of nBA, EA, TDA, and methyldimethoxysilylpropyl methacrylate, and a polymer block (B) consisting of nBA, EA, and TDA. From the reaction rate, the composition ratio (mass ratio) of the polymer block (A) to the acrylic polymer block (B) was (A)/(B)/(A)/(B)/(A)=2.4/43.7/7.8/43.7/2.4 (wt%), which was summed up as (A)/(B)≈13/87 (wt%).
Thereafter, the solution containing the pentablock copolymer c-1 was thoroughly degassed by bubbling with nitrogen, and then n-propylamine (3.1 g) was charged, 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 b-1 was obtained. This solution was vacuum dried, and the triblock copolymer b-1 and the distillate c were recovered. The obtained triblock copolymer b-1 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 triblock copolymer having a block structure of (A)-(B)-(A). From the ¹ 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-1 disappeared in the triblock copolymer b-1, and peaks (3.3 ppm, 2.9 ppm) derived from a Michael adduct with the residual acrylate compound (terminal molecular structure represented by the above formula (2)) appeared. From this result, it can be said that the obtained triblock copolymer is a Michael adduct of a thiol formed by decomposing the trithiocarbonate group of the pentablock copolymer c-1 with n-propylamine and the residual acrylate compound contained in the block copolymer c-1. The molecular weight of the triblock copolymer b-1 was Mn 40,100, Mw 54,900, and Mw/Mn 1.37.

3. Examples and Comparative Examples (Example 1: Production of triblock copolymer b-2)
(1) Simple distillation of distillate The distillate c (100 g) obtained in Production Example 1 was charged into a flask equipped with a stirrer, a thermometer, and a condenser, and stored at an internal temperature of 50° C. for 52 hours. Thereafter, a simple distillation apparatus was attached, and simple distillation was performed at a constant external temperature of 90° C. When the distillation rate reached 32%, the distillation was stopped by cooling to room temperature. The residue remaining in the flask was analyzed by gas chromatography, and the n-propylamine concentration was 0.0016 mmol/g and the methanol concentration was 800 ppm. The residue remaining in the flask was used as the recovered solvent d-1 in the production of the following triblock copolymer b-2.

(2) Production of triblock copolymer using recovered solvent A 250 mL flask equipped with a stirrer, thermometer, and condenser was charged with polymer a (6.2 g), nBA (70 g), EA (4.7 g), TDA (19 g), ABN-E (0.06 g), and ethyl acetate (7.5 g) and recovered solvent d-1 (18 g) obtained in Synthesis Example 1, and the mixture was thoroughly degassed by nitrogen bubbling, and polymerization was started in a thermostatic bath at 60 ° C. After 7 hours, the reaction was stopped by cooling to room temperature to obtain a solution containing triblock copolymer b'-2. The n-propylamine concentration in the polymerization solvent (a mixture of 7.5 g of ethyl acetate and 18 g of recovered solvent d-1) was 0.0011 mmol / g, and the methanol concentration was 565 ppm.
Next, methyldimethoxysilylpropyl methacrylate (0.93 g), ABN-E (0.076 g), and MOA (0.15 g) were charged into the solution containing the triblock copolymer b'-2, and the solution was thoroughly degassed by nitrogen bubbling, and polymerization was initiated in a thermostatic bath at 60°C. Copolymerization of unreacted monomers (nBA, EA, and TDA) during the production of the triblock copolymer b'-2 and newly added methyldimethoxysilylpropyl methacrylate proceeded. After 7 hours, the solution was cooled to room temperature to stop the reaction, and a solution containing the pentablock copolymer c-2 was obtained.
Thereafter, the solution containing the pentablock copolymer c-2 was thoroughly degassed by nitrogen bubbling, and then n-propylamine (0.31 g) was charged, and the decomposition reaction of the trithiocarbonate group was started 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 b-2 was obtained. This solution was vacuum dried, and the triblock copolymer b-2 was recovered. The obtained triblock copolymer b-2 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 triblock copolymer having a block structure of (A)-(B)-(A). The molecular weight of the triblock copolymer b-2 was Mn 41,000, Mw 55,600, and Mw/Mn 1.36.

(Example 2: Production of triblock copolymer b-3)
(1) Heating of distillate The distillate c (100 g) obtained in Production Example 1 was charged into a flask equipped with a stirrer, a thermometer, and a condenser, and stored at an internal temperature of 50° C. for 4 days. The solvent remaining in the flask was analyzed by gas chromatography, and the n-propylamine concentration was 0.014 mmol/g and the methanol concentration was 4,900 ppm. The solvent remaining in the flask was used as recovered solvent d-2 in the production of triblock copolymer b-3.

(2) Production of triblock copolymer using recovered solvent In a 250 mL flask equipped with a stirrer, a thermometer, and a condenser, polymer a (6.2 g) obtained in Synthesis Example 1, nBA (70 g), EA (4.7 g), TDA (19 g), ABN-E (0.06 g), MOA (0.3 g) as a dehydrating agent, and recovered solvent d-2 (25 g) as a solvent were charged, and the mixture was thoroughly degassed by nitrogen bubbling, and polymerization was initiated in a thermostatic bath at 60 ° C. After 7 hours, the mixture was cooled to room temperature to stop the reaction, and a solution containing triblock copolymer b'-3 was obtained.
Methyldimethoxysilylpropyl methacrylate (0.93 g), ABN-E (0.076 g), and MOA (0.15 g) as a dehydrating agent were charged into the solution containing the triblock copolymer b'-3, and the solution was thoroughly degassed by nitrogen bubbling, and polymerization was initiated in a thermostatic bath at 60°C. Copolymerization of unreacted monomers (nBA, EA, and TDA) during the production of the triblock copolymer b'-3 and newly added methyldimethoxysilylpropyl methacrylate proceeded. After 7 hours, the solution was cooled to room temperature to stop the reaction, and a solution containing a pentablock copolymer c-3 was obtained.
Thereafter, the solution containing the pentablock copolymer c-3 was thoroughly degassed by bubbling with nitrogen, and then n-propylamine (0.31 g) was charged, and the decomposition reaction of the trithiocarbonate group was started 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 b-3 was obtained. This solution was vacuum dried, and the triblock copolymer b-3 was recovered. The obtained triblock copolymer b-3 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 triblock copolymer having a block structure of (A)-(B)-(A). The molecular weight of the obtained triblock copolymer b-3 was Mn 41,600, Mw 67,500, and Mw/Mn 1.62.

(Comparative Example 1: Production of triblock copolymer b-4)
(1) Heating of distillate The distillate c (100 g) obtained in Production Example 1 was placed in a flask equipped with a stirrer, a thermometer, and a condenser, and stored at 50° C. for 52 hours. Analysis by gas chromatography revealed that the n-propylamine concentration was 0.027 mmol/g and the methanol concentration was 5,400 ppm. The solvent remaining in the flask was used as recovered solvent d-3 for the production of a triblock copolymer.

(2) Production of triblock copolymer using recovered solvent In a 250 mL flask equipped with a stirrer, a thermometer, and a condenser, polymer a (6.2 g) obtained in Synthesis Example 1, nBA (70 g), EA (4.7 g), TDA (19 g), ABN-E (0.06 g), MOA (0.3 g) as a dehydrating agent, and recovered solvent d-3 (25 g) as a solvent were charged, and the mixture was thoroughly degassed by nitrogen bubbling, and polymerization was initiated in a thermostatic bath at 60 ° C. After 7 hours, the mixture was cooled to room temperature to stop the reaction, and a solution containing triblock copolymer b'-4 was obtained.
Methyldimethoxysilylpropyl methacrylate (0.93 g), ABN-E (0.076 g), and MOA (0.15 g) as a dehydrating agent were charged into the solution containing the triblock copolymer b'-4, and the solution was thoroughly degassed by nitrogen bubbling, and polymerization was initiated in a thermostatic bath at 60°C. Copolymerization of unreacted monomers (nBA, EA, and TDA) during the production of the triblock copolymer b'-4 and newly added methyldimethoxysilylpropyl methacrylate proceeded. After 7 hours, the solution was cooled to room temperature to stop the reaction, and a solution containing a pentablock copolymer c-4 was obtained.
Thereafter, the solution containing the pentablock copolymer c-4 was thoroughly degassed by bubbling with nitrogen, and then n-propylamine (0.31 g) was charged, and the decomposition reaction of the trithiocarbonate group was started 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 b-4 was obtained. This solution was vacuum dried, and the triblock copolymer b-4 was recovered. The obtained triblock copolymer b-4 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 triblock copolymer having a block structure of (A)-(B)-(A). The molecular weight of the triblock copolymer b-4 was Mn 42,500, Mw 88,900, and Mw/Mn 2.09.

4. Results In the production of triblock copolymers by the RAFT method in Examples 1 and 2, solvents with sufficiently low n-propylamine concentrations of 0.0011 mmol/g and 0.014 mmol/g were used as polymerization solvents in the polymerization step in which the recovered solvent was reused, whereby triblock copolymers with sufficiently narrow molecular weight distributions of 1.36 and 1.62, respectively, could be obtained.

On the other hand, in Comparative Example 1, a recovered solvent with an n-propylamine concentration of 0.027 mmol/g was used as the polymerization solvent, and the resulting triblock copolymer b-4 had a broader molecular weight distribution of 2.09 than the triblock copolymer b-1 obtained in Production Example 1. In addition, the results of measuring the molecular weight distribution by GPC showed that the triblock copolymer b-4 obtained in Comparative Example 1 contained two types of polymers: a polymer with a lower molecular weight than the triblock copolymer b-1 obtained in Production Example 1, and a polymer with a higher molecular weight than the triblock copolymer b-1.

In Comparative Example 1, a polymer with a lower molecular weight than the triblock copolymer b-1 obtained in Production Example 1 was obtained. This is believed to be because the primary amine (n-propylamine) in the recovered solvent reacted with the trithiocarbonate group in the polymer a, and polymer elongation did not occur sufficiently in some polymer chains. On the other hand, the trithiocarbonate group that remained without reacting with the primary amine in the recovered solvent reacted with the monomer, which caused the polymer chain to elongate. In Comparative Example 1, the ratio of the monomer to the RAFT agent was higher than the designed ratio, and this is believed to have resulted in a polymer with a higher molecular weight than the triblock copolymer b-1. Therefore, it is believed that the molecular weight distribution was broadened due to the combination of a low molecular weight polymer and a high molecular weight polymer.

Claims (7)

a polymerization step of polymerizing a monomer in a polymerization solvent by a reversible addition-fragmentation chain transfer living radical polymerization method to obtain a polymer solution (S1) containing a vinyl polymer (P1) having a thiocarbonylthio group;
a reaction step of reacting, in the polymer solution (S1), a thiocarbonylthio group contained in the vinyl polymer (P1) with at least one amine compound selected from the group consisting of primary amines and secondary amines to obtain a polymer solution (S2) containing a vinyl polymer (P2);
Including,
In the polymerization step, polymerization is carried out using, as the polymerization solvent, a solvent (S3) containing a recovered solvent recovered from the polymer solution (S2) after the reaction of the vinyl polymer (P1) with the amine compound,
The method for producing a vinyl polymer, wherein the content of the amine compound in the solvent (S3) is 0.025 mmol/g or less. The method for producing a vinyl polymer according to claim 1, wherein the vinyl polymer (P2) has a crosslinkable silyl group. The method for producing a vinyl polymer according to claim 1 or 2, wherein the alcohol content in the solvent (S3) is 5,000 ppm or less. The method for producing a vinyl polymer according to any one of claims 1 to 3, wherein the recovered solvent is obtained by heating the solvent remaining after separating the vinyl polymer (P2) from the polymer solution (S2). The method for producing a vinyl polymer according to claim 4, wherein the recovered solvent is a residue obtained by simple distillation of the solvent remaining after separating the vinyl polymer (P2) from the polymer solution (S2). The method for producing a vinyl polymer according to any one of claims 1 to 5, wherein the molecular weight distribution (Mw/Mn) of the vinyl polymer (P2) is 1.9 or less. The method for producing a vinyl polymer according to any one of claims 1 to 6, wherein the vinyl polymer (P1) is a block copolymer having two or more polymer blocks.