JP7749938B2 - Method for producing block copolymer - Google Patents

Description

The present invention relates to a method for producing a block copolymer.

Precise polymerization, also known as living polymerization, has attracted attention because it can produce polymers with narrow molecular weight distributions and easily produce terminally functionalized polymers and block copolymers. Among these, living radical polymerization is highly valuable due to its versatility and is widely used industrially. Known living radical polymerization methods include 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.

For 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.

JP 2016-023237 A

When industrially producing block copolymers by living radical polymerization, the polymers that make up one of the polymer blocks in the target block copolymer are sometimes produced in bulk, and this polymer (hereinafter also referred to as a "masterbatch") is used in portions.

For example, when producing a block copolymer having polymer block (A) and polymer block (B), a master batch containing the polymer constituting polymer block (A), a living radical polymerization inhibitor, and a polymerization initiator may first be charged into a reactor and polymerized to obtain a master batch containing the polymer constituting polymer block (A). Then, the divided master batch and polymerization initiator may be charged into a reactor along with the monomer constituting polymer block (B) and polymerized to produce multiple lots of block copolymer. This production method enables efficient industrial production of block copolymers and can improve productivity. In particular, if the polymerization liquid obtained from the first polymerization is used directly without purification in the next polymerization, the polymer purification process can be simplified, further improving productivity.

However, when a masterbatch is divided to produce multiple lots of block copolymers, the number-average molecular weight of the polymer contained in the masterbatch may change over time during storage of the masterbatch. In this case, differences in number-average molecular weight between lots may cause variations in the physical properties of the resulting block copolymer, raising concerns that this could cause practical problems in various applications.

The present invention was made in consideration of the above circumstances, and its purpose is to provide a method for producing a block copolymer that, when dividing a masterbatch to produce multiple lots of block copolymer, can produce a block copolymer with little variation in physical properties between lots.

The inventors believed that one of the factors that causes the number-average molecular weight of the polymer contained in the masterbatch to change during storage of the masterbatch is the significant influence of the polymerization initiator remaining in the masterbatch. Based on this finding, they conducted extensive research and discovered that the above-mentioned problem could be solved by conducting polymerization under specific conditions, thereby completing the present invention. Specifically, the present invention provides the following means.

[1] A method for producing a block copolymer having a polymer block (A) and a polymer block (B) by a living radical polymerization method, comprising: a first polymerization step in which a living radical polymerization inhibitor, a first polymerization initiator, and a first vinyl monomer are charged into a first reactor and polymerized to obtain a first polymerization liquid containing a polymer (PA) constituting the polymer block (A); and a second polymerization step in which, after the first polymerization step, a second polymerization initiator, a second vinyl monomer, and the second polymerization liquid are charged into a second reactor and polymerized to obtain the block copolymer; the second polymerization liquid is a polymerization liquid obtained by withdrawing a portion or all of the first polymerization liquid from the first reactor and using the withdrawn first polymerization liquid without purification; and the rate of change in number average molecular weight of the polymer (PA) contained in the second polymerization liquid after the withdrawal is 10% or less; and the 10-hour half-life temperature of the first polymerization initiator is 65°C or less.

[2] The method for producing a block copolymer according to [1] above, wherein the 10-hour half-life temperature of the first polymerization initiator is lower than the 10-hour half-life temperature of the second polymerization initiator.
[3] The method for producing a block copolymer according to [1] or [2] above, wherein the content of the first polymerization initiator in the first polymerization liquid is 1.0×10 ⁻² mmol/g or less.
[4] The method for producing a block copolymer according to any one of [1] to [3] above, wherein the polymer block (A) has a crosslinkable silyl group.

[5] The method for producing a block copolymer according to any one of [1] to [4] above, wherein the concentration of the polymer (PA) in the first polymerization liquid is 95% by mass or less.
[6] The method for producing a block copolymer according to any one of [1] to [5] above, wherein the proportion of the polymer block (A) in the block copolymer is 1 part by mass or more and 30 parts by mass or less per 100 parts by mass of the total amount of the polymer block (A) and the polymer block (B).
[7] The method for producing a block copolymer according to any one of [1] to [6] above, wherein the living radical polymerization inhibitor is an exchange chain transfer mechanism type inhibitor.

According to the production method of the present invention, when a masterbatch is divided to produce multiple lots of block copolymer, it is possible to obtain a block copolymer with little variation in physical properties between the lots. In particular, because the first polymerization liquid obtained in the first polymerization step is used in the second polymerization step without purification, the polymer purification step can be simplified. In other words, according to the production method of the present invention, it is possible to obtain a block copolymer with little variation in physical properties between the lots while simplifying the production process.

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

<<Method for producing block copolymer>>
The method for producing a block copolymer according to the present disclosure (hereinafter also referred to as the "present production method") is a method for producing a block copolymer having a polymer block (A) and a polymer block (B) by living radical polymerization. Specifically, the method includes a first polymerization step and a second polymerization step described below.
First polymerization step: A step of preparing a first polymerization liquid containing a polymer (PA) constituting a polymer block (A) by charging a living radical polymerization inhibitor, a first polymerization initiator, and a first vinyl-based monomer into a first reactor and polymerizing the resulting mixture. Second polymerization step: A step of preparing a block copolymer having a polymer block (A) and a polymer block (B) by charging a second polymerization initiator, a second vinyl-based monomer, and a second polymerization liquid into a second reactor and polymerizing the resulting mixture after the first polymerization step.

In this production method, a block copolymer having polymer block (A) and polymer block (B) is obtained in the second polymerization step by using part or all of the first polymerization liquid obtained in the first polymerization step without purification. Matters related to this disclosure are described in detail below.

<Living radical polymerization method>
In this production method, known polymerization methods can be used as the living radical polymerization method, and specific examples of the living radical polymerization method include a living radical polymerization method using an exchange chain transfer mechanism, a living radical polymerization method using a bond-dissociation mechanism, and a living radical polymerization method using an atom transfer mechanism.

Specific examples of these include living radical polymerization methods using an exchange chain transfer mechanism, such as reversible addition-fragmentation chain transfer polymerization (RAFT), iodine transfer polymerization, polymerization using organotellurium compounds (TERP), polymerization using organoantimony compounds (SBRP), and polymerization using organobismuth compounds (BIRP). Examples of living radical polymerization methods using a bond-dissociation mechanism include the nitroxy radical method (NMP). Examples of living radical polymerization methods using an atom transfer mechanism include atom transfer radical polymerization (ATRP). Of these, living radical polymerization methods using an exchange chain transfer mechanism are preferred because they can be applied to the widest range of vinyl monomers and offer excellent polymerization controllability, and the RAFT method is particularly preferred from the perspective of ease of implementation.

<First polymerization step>
The first polymerization step is a step of producing a first polymerization liquid containing a polymer (PA) constituting the polymer block (A) by polymerizing one or more vinyl monomers (first vinyl monomers) that serve as structural units of the polymer block (A). The first vinyl monomer is not particularly limited, and various vinyl monomers can be used.

(First vinyl monomer)
Specific examples of the vinyl monomer (i.e., the first vinyl monomer) used in the first polymerization step include (meth)acrylic acid alkyl ester compounds, aliphatic cyclic ester compounds of (meth)acrylic acid, aromatic ester compounds of (meth)acrylic acid, and compounds represented by the following formula (1):
_CH2 = ^CR1 -C(=O)O-( ^R2O ) _n - ^R3 ...(1)
(In formula (1), ^R1 represents a hydrogen atom or a methyl group, ^R2 represents a linear or branched alkylene group having 2 to 6 carbon atoms, ^R3 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.)
Examples of the vinyl monomer include compounds represented by the formula (I), styrene-based compounds, maleimide compounds, amide group-containing vinyl compounds, and vinyl-based monomers having a crosslinkable functional group.

Specific examples of (meth)acrylic acid alkyl ester compounds 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.

Specific examples of 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.

Specific examples of 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.

Examples of compounds in which n is 1 in the above formula (1) include (meth)acrylic acid alkoxyalkyl ester compounds and (meth)acrylic acid hydroxyalkyl ester compounds.

(Meth)acrylic acid alkoxyalkyl ester compounds have an oxyalkylene structure (e.g., an oxyethylene chain, an oxypropylene chain, an oxybutylene chain, etc.). Specific examples of (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.

Specific examples of (meth)acrylic acid hydroxyalkyl ester compounds include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (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 (for example, a polyoxyethylene chain, a polyoxypropylene chain, a polyoxybutylene chain, etc.). When n is 2 or more, two or more ^R2s in the above formula (1) may be the same or different. Therefore, a 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 greater 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.

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.

Specific examples of maleimide compounds include maleimide and N-substituted maleimide compounds. 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-cycloalkyl-substituted maleimide compounds such as N-cyclohexylmaleimide and N-cycloalkyl-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; 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.

Specific examples of amide group-containing vinyl compounds include (meth)acrylamide, (meth)acrylamide derivatives, and N-vinylamide monomers. 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.

For vinyl monomers having crosslinkable functional groups, examples of the crosslinkable functional groups include crosslinkable silyl groups, silanol groups, carboxyl groups, hydroxy groups, epoxy groups, oxazoline groups, isocyanate groups, and polymerizable unsaturated groups. Examples of the crosslinkable silyl groups include alkoxysilyl groups and halogenosilyl groups. Of these, alkoxysilyl groups are preferred because of their ease of control over reactivity. Examples include trimethoxysilyl groups, methyldimethoxysilyl groups, dimethylmethoxysilyl groups, triethoxysilyl groups, methyldiethoxysilyl groups, and dimethylethoxysilyl groups.

Specific 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.

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. Crosslinkable silyl group-containing vinyl compounds form crosslinked structures by dehydration condensation between crosslinkable silyl groups, making them advantageous in that they allow efficient polymerization reactions when producing polymers and subsequent crosslinking reactions.

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.). Unsaturated acid anhydrides include maleic anhydride, itaconic anhydride, citraconic anhydride, etc.

Examples of hydroxy group-containing vinyl compounds include the above-mentioned (meth)acrylic acid hydroxyalkyl ester compounds, (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; and maleimide compounds such as N-(4-hydroxyphenyl)maleimide.

Examples of epoxy group-containing vinyl compounds include glycidyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, and 3,4-epoxycyclohexylmethyl (meth)acrylate. The vinyl monomer constituting the polymer (PA) may be one or more of the above.

The vinyl monomer constituting the polymer (PA) preferably includes a (meth)acrylic monomer, because this allows for relatively easy production of vinyl polymers by living radical polymerization and provides a high degree of freedom in monomer selection. When producing the polymer (PA), the amount of the (meth)acrylic monomer used is preferably 60% by mass or more, 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 all monomers used in producing the polymer (PA).

In view of the effectiveness of reducing the variation in physical properties between lots when using this production method, the polymer (PA) preferably has structural units derived from a vinyl monomer having a crosslinkable functional group, and more preferably has structural units derived from a vinyl compound containing a crosslinkable silyl group. When the polymer (PA) has a crosslinkable silyl group, silane crosslinking tends to progress over time between the end of the first polymerization step and the start of the second polymerization step, tending to broaden the molecular weight distribution of the target block copolymer. In this regard, by using this production method, the progression of silane crosslinking (e.g., silane crosslinking triggered by the heat of polymerization of unreacted vinyl monomer contained in the first polymerization liquid) between the end of the first polymerization step and the start of the second polymerization step can be suppressed. This makes it possible to obtain a block copolymer with minimal variation in physical properties between lots, even when using a polymer block (A) having a crosslinkable silyl group.

Specifically, in producing the polymer (PA), the amount of vinyl monomer having a crosslinkable functional group used 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, from the viewpoint of fully obtaining the effects of introducing the crosslinkable functional group (e.g., improved mechanical strength, etc.). The upper limit of the amount of 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 obtaining a block copolymer with little variation in physical properties between lots using this production method.

(Living radical polymerization inhibitor)
The living radical polymerization inhibitor used in this step is preferably an exchange chain transfer mechanism inhibitor, in that it can be applied to a wide range of vinyl monomers and has excellent controllability of polymerization. Examples of exchange chain transfer mechanism inhibitors include inhibitors for the RAFT method (hereinafter also referred to as "RAFT agent"), inhibitors for iodine transfer polymerization, inhibitors for the TERP method, inhibitors for the SBRP method, and inhibitors for the BIRP method. Of these, RAFT agents are particularly preferably used from the viewpoint of ease of implementation.

Various known RAFT agents can be used, including dithioester compounds, xanthate compounds, trithiocarbonate compounds, and dithiocarbamate compounds. Among these, trithiocarbonate compounds are preferred due to their excellent polymerization control of (meth)acrylic monomers (especially (meth)acrylic acid ester compounds). Specific examples of trithiocarbonate compounds include S,S-dibenzyltrithiocarbonate, bis[4-(2,3-dihydroxypropoxycarbonyl)benzyl]trithiocarbonate, bis[4-(2-hydroxyethoxycarbonyl)benzyl]trithiocarbonate, 1,4-bis(n-dodecylsulfanylthiocarbonylsulfanylmethyl)benzene, and 2-{[(2-carboxyethyl)sulfanylthiocarbonyl]sulfanyl}propanoic acid.

The amount of living radical polymerization inhibitor used during polymerization can be adjusted appropriately depending on the type of monomer and living radical polymerization inhibitor used, etc.

(First polymerization initiator)
As the first polymerization initiator, a radical polymerization initiator having a 10-hour half-life temperature of 65°C or lower is used. In this step, by using a radical polymerization initiator having a 10-hour half-life temperature of 65°C or lower, polymerization can be carried out at a reaction temperature that sufficiently suppresses side reactions, while maintaining a relatively short reaction time (e.g., 5 to 8 hours), and the concentration of the radical polymerization initiator in the first polymerization liquid, which is the polymerization liquid obtained by the first polymerization step, can be sufficiently reduced. This prevents changes in the number-average molecular weight of the polymer (PA) contained in the first polymerization liquid when the first polymerization liquid (i.e., masterbatch) is stored until the subsequent second polymerization step is performed, even if the storage period is extended. This prevents variations in the physical properties between lots of the block copolymer obtained by this production method.

From the perspective of sufficiently reducing the concentration of the radical polymerization initiator in the polymerization liquid obtained in the first polymerization step (i.e., the first polymerization liquid) while suppressing side reactions by keeping the reaction temperature during polymerization as low as possible, the 10-hour half-life temperature of the first polymerization initiator is preferably 60°C or lower, and more preferably 55°C or lower.

The first polymerization initiator can be a known radical polymerization initiator such as an azo compound, organic peroxide, or persulfate. Among these, an azo compound is preferred because it is easy to handle safely and is less likely to cause side reactions during radical polymerization.

Specific examples of the first polymerization initiator include 2,2'-azobis(2,4-dimethylvaleronitrile) (10-hour half-life temperature: 51°C), 2,2'-azobis(isobutyronitrile) (10-hour half-life temperature: 65°C), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (10-hour half-life temperature: 30°C), and 1,1'-azobis(1-acetoxy-1-phenylethane) (10-hour half-life temperature: 61°C). Only one type of first polymerization initiator may be used, or two or more types may be used in combination.

From the viewpoint of obtaining a polymer with a narrower molecular weight distribution and minimizing the amount of first polymerization initiator remaining in the first polymerization liquid, the amount of the first polymerization initiator used is preferably 0.5 mol or less, and more preferably 0.4 mol or less, per mol of living radical polymerization control agent. Furthermore, from the viewpoint of stably carrying out the polymerization reaction, the amount of the first polymerization initiator used is preferably 0.01 mol or more, and more preferably 0.03 mol or more, per mol of living radical polymerization control agent. The amount of the first polymerization initiator used per mol of living radical polymerization control agent is preferably 0.01 to 0.5 mol, and more preferably 0.03 to 0.4 mol.

The polymerization reaction may be carried out in the presence of a chain transfer agent (e.g., an alkylthiol compound having 2 to 20 carbon atoms) if necessary. Also, a dehydrating agent (e.g., trimethyl orthoacetate, triethyl orthoacetate, etc.) may be added to the reaction system if necessary.

The polymerization in the first polymerization step may be carried out using any of a batch process, semi-batch process, dry continuous polymerization process, continuous stirred tank process (CSTR), etc. Furthermore, various polymerization methods such as solution polymerization, emulsion polymerization, and suspension polymerization may be used.

The polymerization reaction is preferably carried out in a polymerization solvent known in living radical polymerization in the presence of a living radical polymerization inhibitor and a radical polymerization initiator. By carrying out living radical polymerization in a solvent, a polymerization liquid (i.e., a first polymerization liquid) containing the polymer (PA) can be easily obtained.

The polymerization solvent used can be, for example, an organic solvent capable of dissolving the monomer. Examples of organic solvents include aromatic compounds such as benzene, toluene, xylene, and anisole; ester compounds such as methyl acetate, propyl acetate, and butyl acetate; and ketone compounds such as acetone, methyl ethyl ketone, and cyclohexanone. One polymerization solvent may be used alone, or two or more may be used in combination. When using a hydrophilic monomer, alcohol, water, or the like can be used as the polymerization solvent.

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 reaction. Using an amount of polymerization solvent of 200 parts by mass or less is preferred because it allows for a high polymerization rate to be achieved in a short period of time.

The reaction temperature during polymerization is not particularly limited, but from the viewpoints of suppressing side reactions during polymerization to obtain a block copolymer with a narrow molecular weight distribution, obtaining a block copolymer with minimal lot-to-lot variation in physical properties, and easing restrictions on the polymerization initiators and solvents that can be used, it is preferably 100°C or less, more preferably 90°C or less, and even more preferably 80°C or less. Furthermore, from the viewpoint of smoothly progressing the polymerization reaction, the reaction temperature is preferably 40°C or more, more preferably 45°C or more, and even more preferably 50°C or more. The reaction time in the polymerization reaction can be set appropriately depending on the monomers used, etc., but is preferably 1 hour to 48 hours, more preferably 2 hours to 24 hours, and even more preferably 2 hours to 12 hours.

The polystyrene-equivalent number average molecular weight (Mn) of the polymer (PA) obtained in the first polymerization step, measured by gel permeation chromatography (GPC), is not particularly limited, but is, for example, in the range of 1,000 to 300,000. From the viewpoint of obtaining a block copolymer with excellent coatability, handleability, etc., the Mn of the polymer (PA) is preferably 1,000 to 100,000, and more preferably 1,200 to 100,000.

The molecular weight distribution (Mw/Mn) of the polymer (PA), expressed as the ratio of the weight average molecular weight (Mw) to Mn, is preferably 3.0 or less, more preferably 2.5 or less, and even more preferably 2.0 or less, from the viewpoint of obtaining a block copolymer with little variation in physical properties between lots. There is no particular restriction on the lower limit of Mw/Mn of the polymer (PA), but from the viewpoint of ease of production, it is, for example, 1.01 or more.

The polymerization in the first polymerization step produces a first polymerization liquid containing polymer (PA). The concentration of polymer (PA) in the first polymerization liquid (i.e., the concentration of polymer block (A)) can be adjusted by changing the ratio of the amount of monomer used to the amount of polymerization solvent used. From the viewpoint of increasing the production efficiency of the block copolymer, the concentration of polymer (PA) in the first polymerization liquid is preferably 1% by mass or more, more preferably 2% by mass or more. Furthermore, when polymer (PA) has crosslinkable functional groups, the higher the concentration of polymer (PA), the more likely the crosslinking reaction will progress over time during storage of the first polymerization liquid. Therefore, the concentration of polymer (PA) in the first polymerization liquid is preferably 95% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less.

In the first polymerization step, by using as the first polymerization initiator a radical polymerization initiator having a 10-hour half-life temperature of 65°C or less, the amount of the first polymerization initiator remaining in the first polymerization liquid obtained by the polymerization reaction can be sufficiently reduced. Specifically, the content of the first polymerization initiator in the first polymerization liquid is preferably 1.0 × 10 ^-2 mmol/g or less, more preferably 5.0 × 10 ^-3 mmol/g or less, and even more preferably 3.0 × 10 ^-3 mmol/g or less. When the content of the first polymerization initiator in the first polymerization liquid is within the above range, it is possible to suppress changes in the number average molecular weight of the polymer (PA) over time during storage of the polymerization liquid (i.e., masterbatch) containing the polymer (PA), and it is possible to sufficiently suppress variations in the molecular weight and block ratio between lots of the block copolymer.

The content of the first polymerization initiator in the first polymerization liquid is, in other words, the concentration [I] of the first polymerization initiator, which is a value calculated according to the following formula (i) using the initial concentration [I] ₀ of the first polymerization initiator, the decomposition rate constant k _d of the first polymerization initiator, and the time t.
[I]=[I] ₀ exp(-k _d t)...(i)

<Second polymerization step>
The second polymerization step is a step of producing a block copolymer having polymer block (A) and polymer block (B) by polymerizing one or more vinyl monomers (i.e., second vinyl monomers) that serve as structural units of polymer block (B). In the second polymerization step, after the first polymerization step, a second polymerization initiator, a second vinyl monomer, and a second polymerization liquid are charged into a second reactor and polymerized, thereby obtaining a block copolymer having polymer block (A) and polymer block (B).

(Second Polymerization Liquid)
The second polymerization liquid is a polymerization liquid obtained by extracting a portion or all of the first polymerization liquid from the first reactor. The first polymerization liquid extracted from the first reactor is used as the second polymerization liquid in the second polymerization step without purification. The second polymerization liquid contains the polymer (PA) obtained in the first polymerization step, i.e., the polymer that will constitute the polymer block (A) of the block copolymer. This production method is particularly useful when the first polymerization liquid is produced as a masterbatch and the masterbatch is divided to produce multiple lots of block copolymers. Furthermore, this production method is advantageous in that the first polymerization liquid is used as the second polymerization liquid without purification for the next polymerization, thereby simplifying the block copolymer production process and increasing productivity.

The polymer (PA) contained in the second polymerization liquid has a number average molecular weight change rate (hereinafter also referred to as "Mn change rate") of 10% or less after the first polymerization liquid is withdrawn from the first reactor. When the Mn change rate is 10% or less, even if there is a long period of time between the production of the first polymerization liquid and the start of the second polymerization step, variations in molecular weight and block ratio between batches of the block copolymer can be sufficiently suppressed, and a block copolymer with uniform properties can be obtained. From this perspective, the Mn change rate is preferably 8% or less, more preferably 5% or less, even more preferably 3% or less, and even more preferably 2% or less.

The Mn change rate is a value calculated by the following mathematical formula (ii) using the polystyrene-equivalent number average molecular weight Mn1 of the polymer (PA) measured by GPC immediately after the first polymerization liquid is withdrawn from the first reactor, and the polystyrene-equivalent number average molecular weight Mn2 measured by GPC immediately before the first polymerization liquid is charged into the second reactor.
Mn change rate (%) = [(Mn2 - Mn1) / Mn1] × 100 (ii)

The period from when a portion or all of the first polymerization liquid is withdrawn from the first reactor until the second polymerization liquid is charged into the second reactor in the second polymerization step (hereinafter also referred to as the "storage period") is not particularly limited. The storage period is appropriately determined depending on various factors, such as the management status of the polymer block (A) and the required amount of block copolymer, and can be, for example, from several hours to several months. The storage temperature of the polymerization liquid can also be appropriately selected depending on various conditions, such as the ambient temperature and storage location. The storage temperature of the polymerization liquid is, for example, from -10°C to 50°C.

(Second vinyl monomer)
The second vinyl monomer is not particularly limited, and various vinyl monomers can be used. Specific examples of the second vinyl monomer include (meth)acrylic acid alkyl ester compounds, (meth)acrylic acid aliphatic cyclic ester compounds, (meth)acrylic acid aromatic ester compounds, compounds represented by the above formula (1), styrene compounds, maleimide compounds, amide group-containing vinyl compounds, and vinyl monomers having a crosslinkable functional group. Specific examples of these include the same compounds as those exemplified as the first vinyl monomer. As the second vinyl monomer, one type may be used alone, or two or more types may be used in combination.

The vinyl monomer constituting polymer block (B) preferably includes a (meth)acrylic monomer, because vinyl polymers can be produced relatively easily by living radical polymerization and because there is a high degree of freedom in the selection of monomers. When producing polymer block (B), the amount of (meth)acrylic monomer used is preferably 60% by mass or more, 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 all monomers used in the production of polymer block (B).

(Second Polymerization Initiator)
As the second polymerization initiator, known radical polymerization initiators such as azo compounds, organic peroxides, and persulfates can be used. Among these, azo compounds are preferred because they are safe and easy to handle and are 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). The second polymerization initiator may be the same as or different from the first polymerization initiator. The second polymerization initiator may be used alone or in combination of two or more kinds.

In this production method, it is preferable to select the first polymerization initiator and the second polymerization initiator so that the 10-hour half-life temperature of the first polymerization initiator used in the first polymerization step is lower than the 10-hour half-life temperature of the second polymerization initiator used in the second polymerization step. That is, the second polymerization initiator is preferably a radical polymerization initiator having a 10-hour half-life temperature higher than 65°C. Using a radical polymerization initiator having a 10-hour half-life temperature higher than 65°C as the second polymerization initiator is advantageous in that it can stabilize the polymerization reaction. However, from the perspective of suppressing side reactions during the polymerization reaction, the 10-hour half-life temperature of the second polymerization initiator is preferably 100°C or lower, and more preferably 90°C or lower.

Specific preferred examples of the second polymerization initiator include dimethyl-2,2'-azobis(2-methylpropionate) (10-hour half-life temperature: 66°C), 2,2'-azobis(2-methylbutyronitrile) (67°C), 1,1'-azobis(cyclohexane-1-carbonitrile) (88°C), dimethyl 1,1'-azobis(1-cyclohexanecarboxylate) (73°C), and 2,2'-azobis(isobutyronitrile) (65°C).

From the viewpoint of obtaining a polymer block (B) with a narrower molecular weight distribution, the amount of the second polymerization initiator used is preferably 0.5 mol or less, and more preferably 0.4 mol or less, per mol of the living radical polymerization inhibitor used in the first polymerization step. From the viewpoint of carrying out a stable polymerization reaction, the amount of the second polymerization initiator used is preferably 0.01 mol or more, and more preferably 0.05 mol or more, per mol of the living radical polymerization inhibitor used in the first polymerization step.

As with the first polymerization step, the polymerization reaction in the second polymerization step may be carried out using any of a batch process, semi-batch process, dry continuous polymerization process, continuous stirred tank process, etc. Furthermore, various polymerization methods such as solution polymerization, emulsion polymerization, and suspension polymerization can be used. The polymerization reaction is preferably carried out in a solvent. Examples of the polymerization solvent include the same solvents as those exemplified as polymerization solvents that can be used in the first polymerization step. 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 the monomers and second polymerization liquid used in the reaction.

The reaction temperature of the second polymerization step may be the same as or different from the reaction temperature of the first polymerization step. The reaction temperature of the second polymerization step is not particularly limited, but from the viewpoint of smoothly progressing the polymerization reaction, it is preferably 40°C or higher, more preferably 45°C or higher, and even more preferably 50°C or higher. Furthermore, from the viewpoints of suppressing side reactions during polymerization to obtain a block copolymer with a narrow molecular weight distribution and easing restrictions on the initiators and solvents that can be used, it is preferably 100°C or lower, more preferably 90°C or lower, and even more preferably 80°C or lower. The reaction time in the polymerization reaction is preferably 1 hour to 48 hours, more preferably 2 hours to 24 hours, and even more preferably 2 hours to 12 hours.

A block copolymer having polymer block (A) and polymer block (B) can be obtained by the polymerization reaction in the second polymerization step. The polystyrene-equivalent number average molecular weight (Mn) of the resulting block copolymer, measured by gel permeation chromatography (GPC), is not particularly limited, but is, for example, in the range of 10,000 to 500,000. Since this allows the production of a block copolymer with excellent coatability, handleability, etc., the Mn of the block copolymer is preferably 10,000 to 300,000, and more preferably 12,000 to 150,000.

The molecular weight distribution (Mw/Mn) of the block copolymer is preferably 3.0 or less, more preferably 2.5 or less, and even more preferably 2.0 or less. There is no particular lower limit for the Mw/Mn of the block copolymer, but from the perspective of ease of production, it is, for example, 1.01 or more.

In the resulting block copolymer, the content of polymer block (A) is preferably 1 part by mass or more and 30 parts by mass or less, relative to 100 parts by mass of the total amount of polymer block (A) and polymer block (B). Here, when the proportion of polymer block (A) in the block copolymer is small, it is advantageous to produce multiple lots of block copolymer by dividing a pre-produced master batch in order to suppress a decrease in reactivity due to a low monomer concentration in the polymerization solvent and to reduce costs. From this perspective, this production method is more preferably applied to obtain a block copolymer in which the proportion of polymer block (A) in the block copolymer is 2 parts by mass or more and 25 parts by mass or less, relative to 100 parts by mass of the total amount of polymer block (A) and polymer block (B), and even more preferably applied to obtain a block copolymer in which the proportion of polymer block (A) in the block copolymer is 3 parts by mass or more and 20 parts by mass or less.

The number of blocks and block arrangement in the block copolymer obtained by this production method are not particularly limited. For example, by using a monofunctional RAFT agent as the living radical polymerization inhibitor in the first polymerization step, an (A)-(B) diblock copolymer consisting of polymer block (A)/polymer block (B) can be obtained. Furthermore, by using a bifunctional RAFT agent (e.g., S,S-dibenzyltrithiocarbonate, 1,4-bis(n-dodecylsulfanylthiocarbonylsulfanylmethyl)benzene, etc.) as the living radical inhibitor in the first polymerization step, an (A)-(B)-(A) triblock copolymer consisting of polymer block (A)/polymer block (B)/polymer block (A) can be obtained.

In addition to the first and second polymerization steps, this production method may further include a step of polymerizing a vinyl monomer in the presence of the polymerization liquid obtained in the second polymerization step. In this case, higher-order block copolymers (e.g., tetrablock copolymers, pentablock copolymers, etc.) can be obtained. For example, when producing an (A)-(B)-(A)-(B)-(A) pentablock copolymer consisting of polymer block (A)/polymer block (B)/polymer block (A)/polymer block (B)/polymer block (A) by living radical polymerization using a bifunctional RAFT agent, the target product can be efficiently obtained by producing the block copolymer using a method including the following three-stage polymerization steps.

That is, in the first polymerization step, polymer block (A) is obtained using the monomers that constitute polymer block (A). Subsequently, in the second polymerization step, the monomers that constitute polymer block (B) are polymerized in the presence of polymer block (A) to obtain an (A)-(B)-(A) triblock copolymer consisting of polymer block (A)/polymer block (B)/polymer block (A). Furthermore, in the third polymerization step, the monomers that constitute polymer block (A) are polymerized in the presence of the (A)-(B)-(A) triblock copolymer to obtain an (A)-(B)-(A)-(B)-(A) pentablock copolymer consisting of polymer block (A)/polymer block (B)/polymer block (A)/polymer block (B)/polymer block (A). Furthermore, block copolymers with higher orders than pentablock copolymers can also be obtained by a similar method.

When a polymer solution containing a block copolymer is obtained by the above polymerization, the block copolymer can be isolated by subjecting the polymer solution to a known solvent removal treatment.

Furthermore, when the block copolymer obtained by the above-described polymerization step has a thiocarbonylthio group derived from a RAFT agent, the block copolymer may be reacted with a nucleophilic agent. By this reaction, a thiol group is generated from the thiocarbonylthio group possessed by the block copolymer, and the generated thiol group reacts with the remaining monomer (Michael addition reaction), thereby removing the thiocarbonylthio group, as shown in the following formula (2):

(In formula (2), R represents a residue obtained by removing an acryloyloxy group from an acrylic acid ester compound contained in a monomer that constitutes the molecular chain of the polymer.)
It is possible to obtain a block copolymer having a terminal structure represented by the following formula:

Nucleophiles include ammonia, primary and/or secondary amine compounds, alkali metal alkoxides, hydroxides, and thiols. Of these, primary and/or secondary amine compounds are preferred as nucleophiles in terms of reactivity.

The molar equivalent of the nucleophile relative to the thiocarbonylthio group is preferably 2 to 90 molar equivalents. From the standpoint of reaction efficiency, the amount of nucleophile used relative to the thiocarbonylthio group is preferably 2.5 molar equivalents or more, more preferably 3 molar equivalents or more, and even more preferably 3.5 molar equivalents or more. Furthermore, from the standpoint of reducing the odor caused by unreacted nucleophile, the amount of nucleophile used relative to the thiocarbonylthio group is preferably 75 molar equivalents or less, more preferably 60 molar equivalents or less, and even more preferably 50 molar equivalents or less. The molecular weight of the nucleophile is preferably 150 or less, more preferably 110 or less, and even more preferably 60 or less, from the standpoint of ease of removal of unreacted nucleophile.

Known reactors, such as batch reactors and tubular reactors, can be used in the reaction between the thiocarbonylthio group and the nucleophile. Among these, batch reactors are preferred because they reduce the risk of clogging, a problem that occurs with tubular reactors. From the standpoint of reaction efficiency, the reaction temperature is preferably 10°C or higher, more preferably 15°C or higher, and even more preferably 25°C or higher. Furthermore, to prevent side reactions (e.g., nucleophilic reactions to the polymer main chain), 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 atmospheric pressure, but may be increased or decreased as necessary. From the standpoint of reaction efficiency, the reaction time is preferably 1 hour or longer, more preferably 2 hours or longer, and even more preferably 3 hours or longer. Furthermore, to prevent side reactions (e.g., nucleophilic reactions to the polymer main chain), the reaction time is preferably 48 hours or shorter, more preferably 36 hours or shorter, and even more preferably 24 hours or shorter. If a polymer solution is obtained through the above reaction, the polymer can be isolated by subjecting the polymer solution to a known solvent removal process.

The block copolymers obtained by this production method can be used in a wide range of applications. Specific examples include dispersants, industrial rubber, binders, adhesives, paints, coating agents, and surfactants. Furthermore, there are no particular limitations on the fields of application, and examples include automobile parts, home appliance and office equipment parts, medical equipment parts, packaging materials, civil engineering and construction materials, electrical wires, and miscellaneous goods.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following, "parts" and "%" mean "parts by mass" and "% by mass", respectively, unless otherwise specified.
The analytical methods for the polymers obtained in the Production Examples, Examples and Comparative Examples are described below.

<Measurement of molecular weight of polymer>
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 SuperMultipore HZ-M x 4; Solvent: Tetrahydrofuran; Temperature: 40°C
Detector: RI
Flow rate: 600μL/min

<Measurement of Monomer Reaction Rate>
The obtained polymerization solution was subjected to gas chromatography (GC) measurement under the conditions described below, and the reaction rate (%) of the monomer was calculated from the obtained concentration (mass%) of the monomer.
Measurement conditions Column: Capillary column Agilent CP-Wax52CB (60 m x 0.32 mm ID, df = 0.5 μm) and Agilent DB-1 (30 m x 0.32 mm ID, df = 1.0 μm)
Solvent: tetrahydrofuran Column temperature: 50°C (5 min), 7°C/min, 230°C (5 min)

<Calculation of Content of First Polymerization Initiator in Polymerization Solution>
The content of the first polymerization initiator in the polymerization liquid was calculated from the following formula (i).
[I]=[I] ₀ exp(-k _d t)...(i)
[I]: concentration of the first polymerization initiator [I] ₀ : initial concentration of the first polymerization initiator k _d : decomposition rate constant of the first polymerization initiator t: time

1. Production Example <Production of First Polymerization Solution>
(Production Example 1: Production of Polymerization Solution s-1)
Into a 1 L flask equipped with a stirrer and a thermometer, 28 g of 2-{[(2-carboxyethyl)sulfanylthiocarbonyl]sulfanyl}propanoic acid (hereinafter also referred to as "BM1429") as a living radical polymerization inhibitor, 0.7 g of 2,2'-azobis(2,4-dimethylvaleronitrile) (hereinafter also referred to as "V-65"; 10-hour half-life temperature: 51°C) as a first polymerization initiator, and 0.7 g of n-butyl acrylate (hereinafter also referred to as " nBA). 139 g), ethyl acrylate (hereinafter also referred to as "EA") (9 g), tetradecyl acrylate (hereinafter also referred to as "TDA") (37 g), methyl dimethoxysilylpropyl methacrylate (38 g), ethyl acetate (199 g), and trimethyl orthoacetate (hereinafter also referred to as "MOA") (50 g) were charged, thoroughly degassed by nitrogen bubbling, and the temperature was raised to 58°C to initiate polymerization (first polymerization). After 2 hours, the temperature was raised to 70°C over 1 hour, and the reaction was continued at 70°C for a further 4 hours. Thereafter, the reaction was stopped by cooling to room temperature, and a polymerization solution s-1 containing polymer a-1 was obtained. The concentration of polymer a-1 in polymerization solution s-1 was 50% by mass.

(Production Examples 2 and 3: Production of Polymerization Solutions s-2 and s-3)
The same operations as in Production Example 1 were performed except that the raw materials were charged as shown in Table 1, the reaction temperature was kept at 55°C for 2 hours, then elevated to 60°C over 1 hour, and the reaction was continued at 60°C for a further 4 hours, thereby obtaining a polymerization liquid s-2 containing a polymer a-2 and a polymerization liquid s-3 containing a polymer a-3.

(Production Examples 4 and 5: Production of Polymerization Solutions s-4 and s-5)
The same operations as in Production Example 1 were carried out except that the raw materials used were as shown in Table 1, to obtain a polymerization liquid s-4 containing polymer a-4 and a polymerization liquid s-5 containing polymer a-5.

(Production Examples 6 and 7: Production of Polymerization Solutions s-6 and s-7)
The same operation as in Production Example 1 was performed except that the raw materials were charged as shown in Table 1, the reaction temperature was 60°C, and the reaction was carried out for 7 hours, to obtain a polymerization liquid s-6 containing a polymer a-6 and a polymerization liquid s-7 containing a polymer a-7, respectively.

In Table 1, the abbreviations other than those described in Production Example 1 represent the following compounds.
DBTTC: S,S-dibenzyltrithiocarbonate; HEA: 2-hydroxyethyl acrylate; ABN-E: 2,2'-azobis(2-methylbutyronitrile) (10-hour half-life temperature: 67°C)

<Production of Second Polymerization Liquid>
(Production Example 8: Production of Polymerization Solution sf-1 by Long-Term Storage of Polymerization Solution s-1)
The polymerization solution s-1 obtained in Production Example 1 was placed in a sealed container without purification and stored at 40°C for 2 months to obtain a polymerization solution sf-1 containing polymer af-1. The reaction rates of the monomers constituting polymer a-1 before storage were BA 91%, EA 93%, TDA 92%, and methyldimethoxysilylpropyl methacrylate 100%. The molecular weight of polymer a-1 before storage was measured by GPC (polystyrene equivalent) to be Mn 2,300, Mw 3,400, and Mw/Mn 1.47. The amount of the first polymerization initiator remaining in the polymerization solution s-1 (hereinafter also referred to as "residual initiator amount") was calculated to be 1.4 × 10 ^-4 mmol/g. Meanwhile, the molecular weight of polymer af-1 after storage was measured by GPC (polystyrene equivalent) to be Mn 2,300, Mw 3,400, and Mw/Mn 1.48. The rate of change in number average molecular weight (Mn change rate) before and after storage was 0.0%.

(Production Examples 9 to 14: Production of Polymerization Liquids sf-2 to sf-7 by Long-Term Storage of Polymerization Liquids s-2 to s-7)
Polymerization liquids sf-2 to sf-7 containing polymers af-2 to af-7, respectively, were obtained by the same procedure as in Production Example 8, except that the polymerization liquids were used as shown in Table 2. The reaction rate of the monomers constituting each polymer and the molecular weight of the polymer were measured before storage, and the results are shown in Table 2. The amount of remaining initiator in each polymerization liquid (i.e., first polymerization liquid) before storage was calculated, and the results are shown in Table 2. Furthermore, the molecular weight of the polymer contained in each polymerization liquid (i.e., second polymerization liquid) after storage was measured, and the results are shown in Table 2. The rate of change in the number average molecular weight of the polymer before and after storage was calculated, and the results are shown in Table 2.

<Production of Block Copolymer>
In Examples 1 to 6 and Comparative Examples 1 and 2, block copolymers were produced according to the following production recipes 1 to 6. Details of each production recipe are shown below.

(Manufacturing recipe 1)
A 1-L flask equipped with a stirrer and a thermometer was charged with 49 g of the polymerization solution (first polymerization solution or second polymerization solution), 281 g of nBA, 19 g of EA, 75 g of TDA, 0.3 g of 2,2'-azobis(2-methylbutyronitrile) (hereinafter also referred to as "ABN-E"; 10-hour half-life temperature: 67°C) as a second polymerization initiator, 60 g of ethyl acetate, and 15 g of MOA. The mixture was thoroughly degassed by bubbling nitrogen, and the temperature was raised to 60°C to initiate polymerization (second polymerization). After 7 hours, the mixture was cooled to room temperature to terminate the reaction, yielding a solution containing a block copolymer. The resulting solution was dried under vacuum to yield a block copolymer.

(Manufacturing recipes 2 and 3)
A block copolymer was obtained in the same manner as in Production Recipe 1, except that the raw materials used were as shown in Table 3.

(Manufacturing recipe 4)
A 1 L flask equipped with a stirrer and a thermometer was charged with the polymerization solution (46 g), nBA (280 g), EA (19 g), TDA (75 g), ABN-E (0.3 g) as a second polymerization initiator, ethyl acetate (60 g), and MOA (15 g). The mixture was thoroughly degassed by nitrogen bubbling and heated to 60 ° C to initiate polymerization (second polymerization). After 7 hours, the mixture was cooled to room temperature to terminate the reaction. Further, methyldimethoxysilylpropyl methacrylate (3.7 g), ABN-E (0.3 g), and MOA (0.6 g) were added, and the mixture was thoroughly degassed by nitrogen bubbling and heated to 60 ° C to initiate polymerization (third polymerization). After 7 hours, the mixture was cooled to room temperature to terminate the reaction, yielding a solution containing a block copolymer.

(Manufacturing recipes 5-6)
The same procedure as in Production Recipe 4 was carried out except that the raw materials used were as shown in Table 3, to obtain a solution containing a block copolymer.

2. Examples and Comparative Examples (Example 1)
Diblock copolymers b-1 and bf-1 were produced using polymerization solutions s-1 and sf-1, respectively, in Production Formulation 1. The resulting diblock copolymers b-1 and bf-1 each had a polymer block (A) composed of nBA, EA, TDA, and methyldimethoxysilylpropyl methacrylate, and a polymer block (B) composed of nBA, EA, and TDA, and were diblock copolymers having an (A)-(B) block structure. The molecular weights of diblock copolymer b-1 were Mn 36,700, Mw 49,200, and Mw/Mn 1.34 as determined by GPC measurement (polystyrene equivalent). Furthermore, the compositional ratio (mass ratio) of polymer block (A) to polymer block (B) was (A)/(B) = 5/95 based on the polymerization rate. Similarly, the molecular weights of diblock copolymer bf-1 were Mn 36,800, Mw 49,700, and Mw/Mn 1.35. The composition ratio of polymer block (A) to polymer block (B) was (A)/(B) = 5/95. The rate of change in number average molecular weight (Mn change rate) from diblock copolymer b-1 to diblock copolymer bf-1 was 0.3%.

(Examples 2 and 3 and Comparative Example 1)
Diblock copolymers b-2, b-3, b-7, bf-2, bf-3, and bf-7 were obtained by the same procedure as in Example 1, except that the production formulations and polymerization solutions for the block copolymers were used as shown in Table 4. The molecular weights of the diblock copolymers were measured and are shown in Table 4. The composition ratio (mass ratio) of polymer block (A) to polymer block (B) of each diblock copolymer was calculated from the polymerization rate and is shown in Table 4. Furthermore, the Mn change rate was calculated and is shown in Table 4.

Example 4
Triblock copolymers b-4 and bf-4 were obtained by the same procedure as in Example 1, except that the block copolymer production formulations and polymerization solutions were used as shown in Table 4. The obtained triblock copolymers b-4 and bf-4 were triblock copolymers having a polymer block (A) composed of nBA, EA, TDA, and methyldimethoxysilylpropyl methacrylate, and a polymer block (B) composed of nBA, EA, and TDA, and having an (A)-(B)-(A) block structure. The molecular weight of each triblock copolymer was measured and is shown in Table 4. In addition, the composition ratio (mass ratio) of polymer block (A) to polymer block (B) of each triblock copolymer was calculated from the polymerization rate and is shown in Table 4. Furthermore, the Mn change rate was calculated and is shown in Table 4.

Example 5
Pentablock copolymers b-5 and bf-5 were produced by carrying out a second polymerization using polymerization solutions s-4 and sf-4, respectively, in Production Formula 4, followed by a third polymerization. The resulting pentablock copolymers b-5 and bf-5 were pentablock copolymers 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 having a block structure of (A)-(B)-(A)-(B)-(A). The molecular weights of each pentablock copolymer were measured and are listed in Table 4. In addition, the compositional ratio (mass ratio) of polymer block (A) to polymer block (B) of each pentablock copolymer was calculated from the polymerization rate and is listed in Table 4. Furthermore, the Mn change rate was calculated and is listed in Table 4.

(Example 6 and Comparative Example 2)
Pentablock copolymers b-6, b-8, bf-6, and bf-8 were obtained by the same procedure as in Example 5, except that the block copolymer production formulation and polymerization solution were used as shown in Table 4. The molecular weight of each pentablock copolymer was measured and is shown in Table 4. In addition, the composition ratio (mass ratio) of polymer block (A) to polymer block (B) of each pentablock copolymer was calculated from the polymerization rate and is shown in Table 4. Furthermore, the Mn change rate was calculated and is shown in Table 4.

<Production of Block Copolymers by Aminolysis>
In Examples 7 and 8 and Comparative Example 3, triblock copolymers were produced using the pentablock copolymer by the following amine decomposition procedure. The details of the amine decomposition procedure are shown below.

(Amine decomposition formulation)
500 g of a solution containing a pentablock copolymer (solvent: ethyl acetate) was thoroughly degassed by bubbling nitrogen into a 1 L flask equipped with a stirrer and a thermometer, and then n-propylamine (1.6 g, 5 molar equivalents relative to the trithiocarbonate groups of the pentablock copolymer) was charged, and the decomposition reaction of the trithiocarbonate groups was initiated in a thermostatic bath at 40°C. After 5 hours, the reaction was stopped by cooling to room temperature, yielding a solution containing a triblock copolymer. The resulting solution was vacuum dried to yield a triblock copolymer.

Example 7
Triblock copolymers c-5 and cf-5 were produced using pentablock copolymers b-5 and bf-5, respectively, via the aminolysis method. The resulting triblock copolymers c-5 and cf-5 were triblock copolymers having a polymer block (A) consisting of nBA, EA, TDA, and methyldimethoxysilylpropyl methacrylate, and a polymer block (B) consisting of nBA, EA, and TDA, with an (A)-(B)-(A) block structure. ^1H -NMR measurements confirmed that the peak (4.8 ppm) of hydrogen bonded to the carbon adjacent to the trithiocarbonate group observed in pentablock copolymers b-5 and bf-5 disappeared in triblock copolymers c-5 and cf-5, and peaks (3.3 ppm, 2.9 ppm) derived from the molecular structure resulting from the Michael addition with the remaining acrylate compound (terminal molecular structure represented by formula (2) above) appeared. From these results, it can be said that the obtained triblock copolymer is a Michael adduct of thiol groups formed by decomposition of the trithiocarbonate groups of pentablock copolymers b-5 and bf-5 with n-propylamine and the residual acrylate compounds contained in pentablock copolymers b-5 and bf-5. The molecular weight of triblock copolymer c-5 was Mn 44,600, Mw 59,600, and Mw/Mn 1.34. The molecular weight of triblock copolymer cf-5 was Mn 44,400, Mw 59,900, and Mw/Mn 1.35. The rate of change in number average molecular weight (Mn rate of change) from block copolymer c-5 to diblock copolymer cf-5 was -0.4%.

(Example 8 and Comparative Example 3)
Triblock copolymers c-6, c-8, cf-6, and cf-8 were obtained by the same procedure as in Example 7, except that the pentablock copolymers shown in Table 5 were used. The molecular weights of the respective triblock copolymers were measured and shown in Table 5. The Mn change rates were also calculated and shown in Table 5.

3. Evaluation Results As is clear from the results of Examples 1 to 8, according to this production method, a block copolymer was produced using a polymerization liquid containing the polymer (PA) constituting the polymer block (A) without storage, and a block copolymer was produced using the polymerization liquid as is after storage for a certain period of time (in this example, 40°C, 2 months) without purification, with a small change in number average molecular weight and small lot-to-lot variation in physical properties.

In contrast, in Comparative Examples 1 to 3, there was a large change in number average molecular weight between the block copolymer produced using the polymerization liquid before storage and the block copolymer produced using the polymerization liquid that had been stored for a certain period of time without purification, resulting in large variations in physical properties between lots and poor practicality.

Claims (6)

A method for producing a block copolymer having a polymer block (A) and a polymer block (B) by a living radical polymerization method, comprising the steps of:
a first polymerization step of feeding a living radical polymerization controller, a first polymerization initiator, and a first vinyl monomer into a first reactor and polymerizing them to obtain a first polymerization liquid containing a polymer (PA) constituting the polymer block (A);
a second polymerization step of, after the first polymerization step, charging a second polymerization initiator, a second vinyl monomer, and a second polymerization liquid into a second reactor and polymerizing them to obtain the block copolymer;
Including,
the polymer block (A) has a crosslinkable silyl group,
the second polymerization liquid is a polymerization liquid obtained by withdrawing a part or all of the first polymerization liquid from the first reactor and using the withdrawn first polymerization liquid without purifying it, and a rate of change in number average molecular weight of the polymer (PA) contained in the second polymerization liquid after the withdrawal is 10% or less,
The method for producing a block copolymer, wherein the first polymerization initiator has a 10-hour half-life temperature of 65°C or lower. The method for producing a block copolymer according to claim 1, wherein the 10-hour half-life temperature of the first polymerization initiator is lower than the 10-hour half-life temperature of the second polymerization initiator. 3. The method for producing a block copolymer according to claim 1, wherein the content of the first polymerization initiator in the first polymerization liquid is 1.0×10 ⁻² mmol/g or less. The method for producing a block copolymer according to any one of claims 1 to 3 , wherein the concentration of the polymer (PA) in the first polymerization liquid is 95 mass % or less. 5. The method for producing a block copolymer according to claim 1 , wherein a proportion of the polymer block (A) in the block copolymer is 1 part by mass or more and 30 parts by mass or less per 100 parts by mass of the total amount of the polymer block (A) and the polymer block ( B ). The method for producing a block copolymer according to any one of claims 1 to 5 , wherein the living radical polymerization inhibitor is an exchange chain transfer mechanism type inhibitor.