JP7651735B2 - Method for producing styrene polymer - Google Patents

Description

The present invention relates to a method for producing a styrene polymer using a reversible addition-fragmentation chain transfer agent.

In the field of advanced materials, including electronic materials and biomaterials, various studies have been conducted on narrowing the molecular weight distribution of styrene polymers in order to dramatically improve their performance. Styrene polymers with narrow molecular weight distributions are generally synthesized by living anionic polymerization or living radical polymerization.
As a polymerization method for a styrene polymer, for example, Patent Document 1 describes a method for producing isotactic polystyrene having an isotacticity of 30% or more, which comprises anionically polymerizing a styrene monomer in a hydrocarbon solvent at 0° C. or lower in the presence of a polymerization initiator selected from diphenylalkyllithium and at least one selected from lithium alkoxide and lithium hydroxide.
Furthermore, Patent Document 2 describes a method for preparing a polymer, which includes a step of polymerizing one or more ethylenically unsaturated monomers represented by a specific formula under the control of cyanomethyl-1H-pyrazole-1-carbodithioate as a reversible addition-fragmentation chain transfer agent (RAFT agent). As a more specific preparation method, a method for preparing a styrene polymer by heating a solution containing styrene, cyanomethyl-3,5-dimethyl-1H-pyrazole-1-carbodithioate, 1,1'-azobis(cyclohexanecarbonitrile) as a thermal initiator, and toluene at 100°C for 48 hours is described.
Furthermore, Patent Document 3 describes a liquid phase preparation method for a photoresist composition containing a low dispersibility polymer in a solution, and specifically describes, as one step thereof, a step of polymerizing a substituted styrene monomer in the presence of a thiocarbonylthio chain transfer agent and a peroxide initiator at 100° C. for 24 hours. Patent Document 4 describes a polymerization method for a vinyl-containing monomer using S,S'-bis(α,α'-disubstituted-α''-acetic acid)-trithiocarbonate, and specifically describes a method of polymerizing styrene in the presence of S,S'-bis(α,α'-dimethyl-α''-acetic acid)-trithiocarbonate at 140° C. for 30 minutes to 6 hours.

Japanese Patent Application Publication No. 11-080267 Special table 2017-535634 publication Patent No. 4825405 Patent No. 4914553

However, the production method described in Patent Document 1 requires ultra-dehydration conditions and low-temperature reaction. In addition, when a styrene monomer having a functional group such as an acetoxy group is used, the polymerization initiator reacts with the functional group of the monomer, the polymerization reaction does not proceed well, and the conversion rate of the monomer is low. In addition, the preparation method of a styrene polymer described in Patent Document 2 is improved by adopting a reversible addition-fragmentation chain transfer (hereinafter referred to as RAFT) polymerization method, which makes it unnecessary to perform a dehydration step and makes it difficult for side reactions to occur. However, even in this preparation method, the conversion rate of the monomer is low at about 52% after 48 hours of polymerization reaction, and even if the reaction is continued for a long time, the conversion rate cannot be improved, which is a major problem in production efficiency.
Furthermore, the conversion rate is also low and there is room for improvement in the polymerization process of the substituted styrene monomer described in Patent Document 3. Moreover, the method described in Patent Document 4 has a problem in that it is not possible to produce a styrene polymer applicable to the advanced materials field, for example, a styrene polymer having a high molecular weight (8,000 or more).

The objective of the present invention is to provide a method for producing styrene polymers that can safely produce styrene polymers at a high conversion rate while maintaining a narrow molecular weight distribution even when the polymerization time is short.

The present inventors have conducted extensive investigations into a method for producing a styrene polymer employing a RAFT polymerization method, and as a result have found that by selecting an azo polymerization initiator having a 10-hour half-life temperature of 90°C or higher as a polymerization initiator to be coexisted with a RAFT agent in a polymerization reaction system, and then carrying out a RAFT polymerization reaction of a monomer containing a styrene compound at a high temperature of 110°C or higher, it is possible to RAFT polymerize the monomer safely with a high conversion even in a short period of time, and to produce a styrene polymer having a narrow molecular weight distribution.
The present invention has been completed through further investigation based on these findings.

一般式［１］中、ｎ個のＲ^１は、それぞれ独立して、ヒドロキシ基、カルボキシ基、スルホン酸基、リン酸基、ホスホン酸基、ボロン酸基、シアノ基、ニトロ基、ハロゲノ基、炭素数１～２０のアルキル基、炭素数１～２０のアルコキシ基、炭素数２～２１のアルコキシアルコキシ基、炭素数２～２１のアルコキシカルボニル基、炭素数２～２１のアルキルカルボニルオキシ基、炭素数１～２０のアルキルスルホン酸基、置換基として炭素数６～１４のアリール基を有するホスフィノ基、置換基として炭素数１～２０のアルキル基を２つ有するアミノ基、置換基として炭素数１～２０のアルキル基もしくは炭素数１～２０のアルコキシ基を有するシリル基、置換基として炭素数１～２０のアルキル基もしくは炭素数６～１４のアリール基を３つ有するシリルエーテル基、炭素数６～１４のアリール基、炭素数６～１４のアリールオキシ基、炭素数７～２０のアリールアルキル基、炭素数１～１３のヘテロアリール基、炭素数１～１３のヘテロアリールオキシ基、炭素数２～１９のヘテロアリールアルキル基、炭素数１～１３のヘテロシクロアルキル基、又は炭素数１～１３のヘテロシクロアルキルオキシ基を表し、Ｒ^２は水素原子又は炭素数１～６のアルキル基を表し、ｎは０～５の整数を表す。
＜３＞スチレン化合物の含有量が単量体の総含有量に対して５０質量％以上である、＜１＞又は＜２＞に記載の製造方法。
＜４＞単量体がスチレン化合物のみを含む、＜１＞～＜３＞のいずれか１つに記載の製造方法。
＜５＞アゾ重合開始剤が、２，２’－アゾビス（ｎ－ブチル－２－メチルプロピオンアミド）又は２，２’－アゾビス（２，４，４－トリメチルペンタン）である、＜１＞～＜４＞のいずれか１つに記載の製造方法。
＜６＞アゾ重合開始剤と可逆的付加－開裂連鎖移動剤とのモル比［アゾ重合開始剤：可逆的付加－開裂連鎖移動剤］が１：１～１：１００である、＜１＞～＜５＞のいずれか１つに記載の製造方法。 That is, the above problems were solved by the following means.
<1> A method for producing a styrene polymer, comprising polymerizing a monomer containing a styrene compound at 110°C or higher in the presence of a reversible addition-fragmentation chain transfer agent and an azo polymerization initiator having a 10-hour half-life temperature of 90°C or higher.
<2> The method according to <1>, wherein the styrene compound is a compound represented by the following general formula [1]:

In the general formula [1], n R ^1s each independently represent a hydroxy group, a carboxy group, a sulfonic acid group, a phosphoric acid group, a phosphonic acid group, a boronic acid group, a cyano group, a nitro group, a halogeno group, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkoxyalkoxy group having 2 to 21 carbon atoms, an alkoxycarbonyl group having 2 to 21 carbon atoms, an alkylcarbonyloxy group having 2 to 21 carbon atoms, an alkylsulfonic acid group having 1 to 20 carbon atoms, a phosphino group having an aryl group having 6 to 14 carbon atoms as a substituent, an amino group having two alkyl groups having 1 to 20 carbon atoms as a substituent, a carbon atom as a substituent, a silyl group having an alkyl group having 1 to 20 carbon atoms or an alkoxy group having 1 to 20 carbon atoms, a silyl ether group having three alkyl groups having 1 to 20 carbon atoms or aryl groups having 6 to 14 carbon atoms as substituents, an aryl group having 6 to 14 carbon atoms, an aryloxy group having 6 to 14 carbon atoms, an arylalkyl group having 7 to 20 carbon atoms, a heteroaryl group having 1 to 13 carbon atoms, a heteroaryloxy group having 1 to 13 carbon atoms, a heteroarylalkyl group having 2 to 19 carbon atoms, a heterocycloalkyl group having 1 to 13 carbon atoms, or a heterocycloalkyloxy group having 1 to 13 carbon atoms; R ² represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and n represents an integer of 0 to 5.
<3> The method according to <1> or <2>, wherein the content of the styrene compound is 50 mass% or more based on the total content of the monomers.
<4> The method according to any one of <1> to <3>, wherein the monomer contains only a styrene compound.
<5> The method according to any one of <1> to <4>, wherein the azo polymerization initiator is 2,2'-azobis(n-butyl-2-methylpropionamide) or 2,2'-azobis(2,4,4-trimethylpentane).
<6> The method according to any one of <1> to <5>, wherein the molar ratio of the azo polymerization initiator to the reversible addition-fragmentation chain transfer agent [azo polymerization initiator:reversible addition-fragmentation chain transfer agent] is 1:1 to 1:100.

一般式［２］中、Ｒ^５及びＲ^６は、それぞれ独立して、置換基を有する又は無置換の炭素数１～２０のアルキル基を表し、この置換基は、ヒドロキシ基、カルボキシ基、シアノ基、ハロゲノ基、炭素数１～２０のアルコキシ基、炭素数２～２１のアルコキシカルボニル基、炭素数１～２０のアルキルチオ基、置換基として炭素数１～２０のアルキル基を有するアミノ基、炭素数６～１４のアリール基、炭素数６～１４のアリールオキシ基、アルコキシポリアルキレングリコールカルボニル基、又はＮ－スクシンイミジルオキシカルボニル基を表す。

一般式［３］中、Ｒ^７は、置換基を有する又は無置換の炭素数１～２０のアルキル基を表し、この置換基は、ヒドロキシ基、カルボキシ基、シアノ基、ハロゲノ基、炭素数１～２０のアルコキシ基、炭素数２～２１のアルコキシカルボニル基、炭素数１～２０のアルキルチオ基、置換基として炭素数１～２０のアルキル基を有するアミノ基、炭素数６～１４のアリール基、炭素数６～１４のアリールオキシ基、又はＮ－スクシンイミジルオキシカルボニル基を表し、Ａは、置換基として炭素数１～２０のアルキル基及び５～７員の環状構造からなる群から選ばれる基を有する、もしくは無置換のアミノ基、又は置換基として、ハロゲノ基、シアノ基、炭素数１～２０のアルキル基及び炭素数１～２０のアルコキシ基からなる群から選ばれる基を有する、もしくは無置換の５～７員の環状構造を表す。 <7> The method according to any one of <1> to <6>, wherein the reversible addition-fragmentation chain transfer agent is a compound represented by the following general formula [2] or [3]:

In the general formula [2], ^R5 and ^R6 each independently represent a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, and this substituent represents a hydroxy group, a carboxy group, a cyano group, a halogeno group, an alkoxy group having 1 to 20 carbon atoms, an alkoxycarbonyl group having 2 to 21 carbon atoms, an alkylthio group having 1 to 20 carbon atoms, an amino group having an alkyl group having 1 to 20 carbon atoms as a substituent, an aryl group having 6 to 14 carbon atoms, an aryloxy group having 6 to 14 carbon atoms, an alkoxypolyalkylene glycolcarbonyl group, or an N-succinimidyloxycarbonyl group.

In the general formula [3], R ⁷ represents a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, and the substituent is a hydroxy group, a carboxy group, a cyano group, a halogeno group, an alkoxy group having 1 to 20 carbon atoms, an alkoxycarbonyl group having 2 to 21 carbon atoms, an alkylthio group having 1 to 20 carbon atoms, an amino group having an alkyl group having 1 to 20 carbon atoms as a substituent, an aryl group having 6 to 14 carbon atoms, an aryloxy group having 6 to 14 carbon atoms, or an N-succinimidyloxycarbonyl group; A represents an unsubstituted amino group having a group selected from the group consisting of an alkyl group having 1 to 20 carbon atoms and a 5- to 7-membered cyclic structure as a substituent, or an unsubstituted 5- to 7-membered cyclic structure having a group selected from the group consisting of a halogeno group, a cyano group, an alkyl group having 1 to 20 carbon atoms, and an alkoxy group having 1 to 20 carbon atoms as a substituent.

<8> The method according to any one of <1> to <7>, wherein the polymerization is carried out in the presence of a polymerization inhibitor.
<9> The method according to <8>, wherein the polymerization inhibitor is selected from the group consisting of 4-tert-butylcatechol, hydroquinone, hydroquinone monomethyl ether, benzoquinone, tert-butylhydroquinone, and dibutylhydroxytoluene.
<10> The production method according to <8> or <9>, wherein the amount of the polymerization inhibitor used is 10 to 3,000 ppm per 1 g of the monomer.
<11> The production method according to any one of <8> to <10>, wherein a step of removing the polymerization inhibitor from the reaction mixture after the polymerization is not performed.
<12> The method according to any one of <1> to <11>, wherein the polymerization is carried out in an organic solvent or under a solvent-free condition.

The process for producing a styrene polymer of the present invention is capable of producing a styrene polymer having a narrow molecular weight distribution safely at a high conversion rate even in a short period of time.
The above and other features and advantages of the present invention will become more apparent from the following description.

In the present invention, a numerical range expressed using "to" means a range including the numerical values written before and after "to" as the lower and upper limits. In the present invention, when multiple numerical ranges are set stepwise for the reaction conditions, the amounts of raw material compounds used, etc., the upper and lower limits forming the numerical range are not limited to the specific combinations written before and after "to" as specific numerical ranges, and the upper and lower limit numerical values forming each numerical range can be appropriately combined.
In the present invention, the expression of a compound (including a polymer) (for example, when it is referred to by adding "compound" to the end) is used to mean not only the compound itself, but also its salts and ions. It also means to include derivatives that are partially changed, such as by introducing a substituent, within the scope that does not impair the effects of the present invention.
In the present invention, the substituents, linking groups, etc. (hereinafter, abbreviated as "substituents, etc.") that are not specified as substituted or unsubstituted may have an appropriate substituent. Therefore, in the present invention, even if it is simply described as a YYY group, this YYY group includes an embodiment that has a substituent in addition to an embodiment that has no substituent. More specifically, an "alkyl group" that is not specified as substituted or unsubstituted includes an alkyl group that has no substituent (unsubstituted alkyl group) and an alkyl group that has a substituent (substituted alkyl group). This also applies to compounds that are not specified as substituted or unsubstituted. A preferred substituent is, for example, the substituent Z described below.
In the present invention, when there are multiple substituents etc. indicated by a specific symbol, or when multiple substituents etc. are specified at the same time, it means that the respective substituents etc. may be the same or different from each other. In addition, even if not specified otherwise, when multiple substituents etc. are adjacent, they may be linked to each other or condensed to form a ring.
In the present invention, the term "(meth)acrylic" refers to either or both of acrylic and methacrylic. The same applies to (meth)acrylate.
In the present invention, when the number of carbon atoms of a certain group is specified, this carbon number means the number of carbon atoms of the group itself unless otherwise specified in the present invention. In other words, when this group has a further substituent (excluding groups that can be interpreted as one group in the form of having a further substituent, such as branched alkyl groups), the carbon number means the number of carbon atoms counted without including the number of carbon atoms of the substituent.
In the present invention, the term "polymer" is meant to include not only homopolymers but also copolymers.

[Method of producing styrene polymer]
The method for producing a styrene polymer of the present invention (sometimes referred to as the production method of the present invention) is a method for RAFT polymerization of a monomer containing a styrene compound at a reaction temperature of 110°C or higher in the presence of a RAFT agent and an azo polymerization initiator having a 10-hour half-life temperature of 90°C or higher. In the production method of the present invention, the RAFT agent functions as a chain transfer agent or the like by utilizing radicals generated by thermal decomposition (cleavage) of the azo polymerization initiator, and the polymerization reaction of the monomer proceeds. The RAFT polymerization reaction occurring in the production method of the present invention is the same as a normal RAFT polymerization reaction using a RAFT agent. The mechanism of a normal RAFT polymerization reaction using a RAFT agent is described, for example, in Patent Document 2.

As described above, the process of the present invention makes it possible to safely produce a styrene polymer having a narrow molecular weight distribution at a high conversion even in a short period of time.
In the present invention, the conversion rate (also referred to as the reaction rate) indicates the conversion rate of the monomer, and indicates the percentage of the amount of the monomer that has reacted as the RAFT polymerization reaction proceeds relative to the amount of the monomer that has been supplied to the RAFT polymerization reaction: (amount reacted/amount supplied)×100 (%). Specific measurement and calculation methods will be described in the examples below.
The high conversion rate achieved by the production method of the present invention and the narrow molecular weight distribution of the resulting styrene polymer will be described in detail later.

First, the compounds used in the production method of the present invention will be described.
<Monomer>
The monomer used in the production method of the present invention contains a styrene compound. The monomer containing a styrene compound includes both a monomer containing only a styrene compound and a monomer containing a styrene compound and another polymerizable compound.

(Styrene compounds)
The styrene compound may be any compound having a vinylbenzene skeleton, and examples thereof include styrene, styrene having a substituent, etc. The substituent is not particularly limited as long as it does not impair the effects of the present invention, and can be appropriately selected, for example, from the substituent Z described below.
The monomer used in the production method of the present invention may contain one type or two or more types of styrene compounds.
As the styrene compound, a compound represented by the following general formula [1] is preferable.

In the general formula [1], n R ^1s each independently represent a hydroxy group, a carboxy group, a sulfonic acid group (-S(=O) ₂ (OH)), a phosphoric acid group (-OP(=O)(OH) ₂ ), a phosphonic acid group (-P(=O)(OH) ₂ ), a boronic acid group (-B(OH) ₂ ), a cyano group, a nitro group, a halogeno group, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkoxyalkoxy group having 2 to 21 carbon atoms, an alkoxycarbonyl group having 2 to 21 carbon atoms, an alkylcarbonyloxy group having 2 to 21 carbon atoms, an alkylsulfonic acid group having 1 to 20 carbon atoms, a phosphino group having an aryl group having 6 to 14 carbon atoms as a substituent, an amino group having two alkyl groups having 1 to 20 carbon atoms as a substituent, an alkyl group having 1 to 20 carbon atoms or an aryl group having 1 to 20 carbon atoms as a substituent. a silyl group having a alkoxy group, a silyl ether group having three alkyl groups having 1 to 20 carbon atoms or aryl groups having 6 to 14 carbon atoms as substituents, an aryl group having 6 to 14 carbon atoms, an aryloxy group having 6 to 14 carbon atoms, an arylalkyl group having 7 to 20 carbon atoms, a heteroaryl group having 1 to 13 carbon atoms, a heteroaryloxy group having 1 to 13 carbon atoms, a heteroarylalkyl group having 2 to 19 carbon atoms, a heterocycloalkyl group having 1 to 13 carbon atoms, or a heterocycloalkyloxy group having 1 to 13 carbon atoms.

The halogeno group includes a halogen atom, for example, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
The alkyl group having 1 to 20 carbon atoms may be any of a straight chain, a branched chain, and a cyclic chain. The number of carbon atoms in this alkyl group is preferably 1 to 12, more preferably 1 to 6, and further preferably 1 to 4. Specifically, the alkyl group having 1 to 20 carbon atoms is preferably methyl, isobutyl, or tert-butyl.
The alkoxy group having 1 to 20 carbon atoms may be any of linear, branched, or cyclic. The number of carbon atoms in this alkoxy group is preferably 1 to 12, more preferably 1 to 6, and even more preferably 1 to 4. Specifically, the alkoxy group having 1 to 20 carbon atoms is preferably methoxy or tert-butoxy.
The alkoxyalkoxy group having 2 to 21 carbon atoms means a group represented by -O-R ^A1 -O-R ^A2 , where R ^A1 represents an alkylene group and R ^A2 represents an alkyl group. The alkylene group that can be taken as R ^A1 includes an alkylene group having 1 to 20 carbon atoms, which may be any of a straight chain, branched chain, or cyclic chain, and is preferably a straight chain. The number of carbon atoms in this alkylene group R ^A1 is preferably 1 to 6, and more preferably 1 to 4. Specifically, the alkylene group R ^A1 is preferably ethylene. The alkyl group that can be taken as R ^A2 includes an alkyl group having 1 to 20 carbon atoms, which may be any of a straight chain, branched chain, or cyclic chain. The number of carbon atoms in this alkyl group R ^A2 is preferably 1 to 6, and more preferably 1 to 4. Specifically, the alkyl group R ^A2 is preferably ethyl. The number of carbon atoms in the alkoxyalkoxy group is the sum of the number of carbon atoms in the alkylene group R ^A1 and the alkyl group R ^A2 and is determined by the number of carbon atoms in each group, but is preferably, for example, 2 to 12, and more preferably 2 to 8. Specifically, the alkoxyalkoxy group having 2 to 21 carbon atoms is preferably 1-ethoxyethoxy.
The alkoxycarbonyl group having 2 to 21 carbon atoms means a group represented by -CO-O-R ^A3 , where R ^A3 is an alkyl group. The alkyl group which can be taken as R ^A3 is the same as the alkyl group having 1 to 20 carbon atoms which can be taken as R ¹ .
The alkylcarbonyloxy group having 2 to 21 carbon atoms means a group represented by -O-CO-R ^A4 , where R ^A4 represents an alkyl group. The alkyl group that can be taken as R ^A4 includes an alkyl group having 1 to 20 carbon atoms, which may be any of a straight chain, branched chain, and cyclic chain. The number of carbon atoms in this alkyl group R ^A4 is preferably 1 to 6, and more preferably 1 to 4. Specifically, the alkyl group R ^A4 is preferably methyl.

The aryl group having 6 to 14 carbon atoms may be any group in which a ring-constituting atom of an aromatic hydrocarbon ring serves as a binding site, and includes groups consisting of an aromatic hydrocarbon ring, groups consisting of an aromatic hydrocarbon ring and other rings, etc. Examples of such other rings include aromatic heterocycles, non-aromatic rings (including unsaturated aliphatic hydrocarbon rings and unsaturated aliphatic heterocycles), saturated aliphatic hydrocarbon rings, saturated aliphatic heterocycles, etc. The aryl group may have a monocyclic structure or a polycyclic structure (such as a condensed ring structure, a bridged ring structure, or a spiro ring structure). The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6.
The aryl group in the aryloxy group having 6 to 14 carbon atoms is the same as the above-mentioned aryl group having 6 to 14 carbon atoms.
An arylalkyl group having 7 to 20 carbon atoms means an alkyl group having an aryl group as a substituent. The aryl group that can be taken here is the same as the aryl group having 6 to 14 carbon atoms. The alkyl group that can be taken here (the alkyl group before being substituted with the aryl group) may be any of a straight chain, branched chain, or cyclic chain, and is preferably a straight chain. The number of carbon atoms in this alkyl group is preferably 1 to 6, and more preferably 1 to 3. The number of carbon atoms in the arylalkyl group is the sum of the number of carbon atoms in the aryl group and the alkyl group, and is determined by the number of carbon atoms in each group, and is, for example, preferably 7 to 16, and more preferably 7 to 9.

The alkylsulfonic acid group having 1 to 20 carbon atoms means a group represented by -S(=O) ₂ ( ^ORS ), where ^Rs represents an alkyl group. The alkyl group which can be taken as ^Rs is the same as the alkyl group having 1 to 20 carbon atoms which can be taken as ^R1 .
A phosphino group having an aryl group having 6 to 14 carbon atoms as a substituent means a group represented by -P(H) _PX (R ^P ) _PY , where R ^P represents an aryl group. The aryl group which can be R ^P is the same as the above-mentioned aryl group having 6 to 14 carbon atoms. PX is 0 or 1, and PY is 1 or 2. However, the sum of PX and PY is 2.
An amino group having two alkyl groups having 1 to 20 carbon atoms as a substituent means an N,N-dialkylamino group, and the two alkyl groups of the amino group are the same as the above-mentioned alkyl groups having 1 to 20 carbon atoms which may be taken as R ^1. The two alkyl groups of the N,N-dialkylamino group may be the same or different.
The silyl group having an alkyl group having 1 to 20 carbon atoms or an alkoxy group having 1 to 20 carbon atoms as a substituent means a group represented by -Si(H) _SiX ( ^RSi ) _SiY , where ^RSi represents an alkyl group or an alkoxy group. The alkyl group and alkoxy group which can be taken as ^RSi are the same as the alkyl group having 1 to 20 carbon atoms and the alkoxy group having 1 to 20 carbon atoms which can be taken as ^R1, respectively. SiX is an integer of 0 to 2, and SiY is an integer of 1 to 3. However, the sum of SiX and SiY is 3. When the silyl group has two or more substituents, the two or more substituents may be the same or different.
The silyl ether group having three alkyl groups having 1 to 20 carbon atoms or three aryl groups having 6 to 14 carbon atoms as substituents means a group represented by -O-Si(R ^SiO ) ₃ , where R ^SiO represents an aryl group or an alkyl group. The alkyl group that can be taken as R ^SiO is the same as the alkyl group having 1 to 20 carbon atoms that can be taken as R ¹ , and the aryl group that can be taken as R ^SiO is the same as the aryl group having 6 to 14 carbon atoms that can be taken as R ^1. The three R ^SiO may be the same or different, and it is preferable that two or more R ^SiO are the same. Specifically, the group represented by -O-Si(R ^SiO ) ₃ is preferably trimethylsilyl ether, triisopropylsilyl ether, tert-butyldimethylsilyl ether, di-tert-butylisobutylsilyl ether, or tert-butyldiphenylsilyl ether.

The heteroaryl group having 1 to 13 carbon atoms may be a group in which the ring-constituting atom of an aromatic heterocycle is the bonding site, and includes a group consisting of an aromatic heterocycle, a group consisting of an aromatic heterocycle and another ring, and the like. The heteroatom contained in the ring structure of the aromatic heterocycle is not particularly limited, and examples thereof include a nitrogen atom, an oxygen atom, a sulfur atom, a silicon atom, and a phosphorus atom. One aromatic heterocycle has one or more heteroatoms in the ring, and usually has 1 to 4, preferably 1 to 2. The aromatic heterocycle is preferably a 5- to 7-membered ring. Examples of the other ring include an aromatic hydrocarbon ring, a non-aromatic ring (including an unsaturated aliphatic hydrocarbon ring and an unsaturated aliphatic heterocycle), a saturated aliphatic hydrocarbon ring, and a saturated aliphatic heterocycle. The heteroaryl group may be a monocyclic structure or a polycyclic structure (such as a condensed ring structure, a bridged ring structure, or a spiro ring structure). The number of carbon atoms in the heteroaryl group is preferably 1 to 9, and more preferably 3 to 6.
The heteroaryl group in the heteroaryloxy group having 1 to 13 carbon atoms is the same as the heteroaryl group having 1 to 13 carbon atoms described above.
A heteroarylalkyl group having 2 to 19 carbon atoms means an alkyl group having a heteroaryl group as a substituent. The heteroaryl group that can be taken here is the same as the heteroaryl group having 1 to 13 carbon atoms that can be taken as R ^1. The alkyl group that can be taken here (the alkyl group before being substituted with the heteroaryl group) is the same as the alkyl group in the arylalkyl group having 7 to 20 carbon atoms that can be taken as R ^1. The number of carbon atoms in the heteroarylalkyl group is the sum of the number of carbon atoms in the heteroaryl group and the alkyl group, and is determined by the number of carbon atoms in each group, and is, for example, preferably 3 to 15, and more preferably 4 to 9.

The heterocycloalkyl group having 1 to 13 carbon atoms may be a group in which the ring-constituting atom of a saturated aliphatic heterocycle is the binding site, and includes a group consisting of a saturated aliphatic heterocycle, a group consisting of a saturated aliphatic heterocycle and another ring, and the like. The heteroatom in the ring structure of the saturated aliphatic heterocycle is not particularly limited, and is the same as the heteroatom in the heteroaryl group having 1 to 13 carbon atoms. One saturated aliphatic heterocycle has one or more heteroatoms in the ring, usually 1 to 4, preferably 1 to 2. The saturated aliphatic heterocycle is preferably a 5- to 7-membered ring. Examples of the other ring include an aromatic hydrocarbon ring, an aromatic heterocycle, an unsaturated aliphatic hydrocarbon ring, an unsaturated aliphatic heterocycle, and a saturated aliphatic hydrocarbon ring. The heterocycloalkyl group may be a monocyclic structure or a polycyclic structure (such as a condensed ring structure, a bridged ring structure, or a spiro ring structure). The number of carbon atoms in the heterocycloalkyl group is preferably 1 to 9, and more preferably 3 to 6. Heterocycloalkyl groups include, for example, cyclic ether groups such as tetrahydrofuran, tetrahydropyran, and the like.
The heterocycloalkyl group in the heterocycloalkyloxy group having 1 to 13 carbon atoms is the same as the heterocycloalkyl group having 1 to 13 carbon atoms described above.

Each of the above-mentioned groups (excluding amino group) having a substituent that can be taken as R ¹ may have at least one substituent, and may have as many substituents as possible.
Furthermore, the carboxy group, sulfonic acid group, phosphoric acid group, phosphonic acid group, boronic acid group, etc. may form an inorganic salt or an organic salt.

Among the above groups, R ¹ is preferably an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkoxyalkoxy group having 2 to 21 carbon atoms, or an alkylcarbonyloxy group having 2 to 21 carbon atoms.

In the general formula [1], the position of the benzene ring at which R ¹ is substituted may be any one of the 2nd to 4th positions relative to the ring-constituting carbon atom (position 1) to which the vinyl group is bonded. In addition, even when two or more R ^1s are present, the combination of bonding positions is not particularly limited.

In general formula [1], n represents an integer from 0 to 5, preferably an integer from 0 to 3, and more preferably an integer from 0 to 2.

In the general formula [1], ^R2 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and preferably a hydrogen atom. The alkyl group having 1 to 6 carbon atoms that can be represented by ^R2 may be any of a straight chain, branched chain, and cyclic chain. The number of carbon atoms in this alkyl group is preferably 1 to 3, and more preferably 1.

Specific examples of the styrene compound include styrene (unsubstituted styrene); α-methylstyrene; hydroxy group-containing styrenes such as hydroxystyrene; carboxy group-containing styrenes such as 4-vinylbenzoic acid; sulfonic acid group-containing styrenes such as sodium styrenesulfonate; boronic acid group-containing styrenes such as 4-vinylphenylboronic acid; nitro group-containing styrenes such as 4-nitrostyrene; halogeno group-containing styrenes such as 3-chlorostyrene, 4-chlorostyrene, 3-bromostyrene, 4-bromostyrene, 4-fluorostyrene, and pentafluorostyrene; alkyl group-containing styrenes such as 2-vinyltoluene, 3-vinyltoluene, 4-vinyltoluene, 4-isobutylstyrene, 4-tert-butylstyrene, 4-isopropenyltoluene, 2,4-dimethylstyrene, and 2,4,6-trimethylstyrene; alkoxy groups such as 2-methoxystyrene, 3-methoxystyrene, 4-methoxystyrene, 2-tert-butoxystyrene, 3-tert-butoxystyrene, and 4-tert-butoxystyrene. alkylsulfonic acid group-containing styrenes such as ethyl styrenesulfonate; phosphino group-containing styrenes such as diphenylphosphinostyrene; amino group-containing styrenes such as N,N-dimethylaminostyrene; silyl group-containing styrenes such as trimethoxy(4-vinylphenyl)silane and trimethyl(4-vinylphenyl)silane; silyl ether group-containing styrenes such as trimethyl(4-vinylphenoxy)silane, triisopropyl(4-vinylphenoxy)silane, tert-butyldimethyl(4-vinylphenoxy)silane, di-tert-butylisobutyl(4-vinylphenoxy)silane, and tert-butyldiphenyl(4-vinylphenoxy)silane; heterocycloalkyloxy group-containing styrenes such as 2-(4-vinylphenoxy)tetrahydropyran, and the like.
Among these, (unsubstituted) styrene, alkyl group-containing styrene, alkoxy group-containing styrene, alkoxyalkoxy group-containing styrene, and alkylcarbonyloxy group-containing styrene are preferred, and specifically, styrene, 4-vinyltoluene, 4-isobutylstyrene, 4-tert-butylstyrene, 2,4-dimethylstyrene, 4-methoxystyrene, 4-tert-butoxystyrene, 4-(1-ethoxyethoxy)styrene, and 4-acetoxystyrene are preferred.

(Other polymerizable compounds)
The other polymerizable compound that the monomer may contain together with the styrene compound may be any compound that can be copolymerized with the styrene compound, and may generally be a polymerizable compound having an ethylenic unsaturated bond. Such a polymerizable compound is not particularly limited, and for example, a polymerizable compound that is generally used in a RAFT polymerization reaction may be used without any particular limitation.
Examples of such polymerizable compounds include (meth)acrylic compounds, vinyl carboxylate compounds, conjugated diene compounds, olefin compounds, vinyl halide compounds, and vinylidene halide compounds.

The (meth)acrylic compound includes an acrylic compound and a methacrylic compound, for example,
(Meth)acrylic acid;
Alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and dodecyl (meth)acrylate;
cycloalkyl (meth)acrylates such as 1-methylcyclopentyl (meth)acrylate, 1-ethylcyclopentyl (meth)acrylate, 1-isopropylcyclopentyl (meth)acrylate, 1-propylcyclopentyl (meth)acrylate, 1-methylcyclohexyl (meth)acrylate, 1-ethylcyclohexyl (meth)acrylate, 1-isopropylcyclohexyl (meth)acrylate, and 1-propylcyclohexyl (meth)acrylate;
(meth)acrylates having a cyclic ester group, such as γ-butyrolactone (meth)acrylate;
(meth)acrylates having a cyclic ether group, such as 3,4-epoxycyclohexyl (meth)acrylate, glycidyl (meth)acrylate, β-methylglycidyl acrylate, and oxetanyl (meth)acrylate;
(meth)acrylic acid esters having a hydroxy group, such as 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, and caprolactone-modified 2-hydroxyethyl (meth)acrylate;
ethylene glycol (meth)acrylates such as methoxydiethylene glycol (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, isooctyloxydiethylene glycol (meth)acrylate, phenoxytriethylene glycol (meth)acrylate, methoxytriethylene glycol (meth)acrylate, and methoxypolyethylene glycol (meth)acrylate;
etc. can be mentioned.

Examples of vinyl carboxylate compounds include vinyl carboxylate compounds having 3 to 10 carbon atoms, such as vinyl formate, vinyl acetate, vinyl propionate, and vinyl pivalate.

As the monomer used in the manufacturing method of the present invention, a styrene compound is used alone or a mixture of a styrene compound and other polymerizable compounds is used depending on the application, characteristics, etc. When a mixture of a styrene compound and other polymerizable compounds is used as a monomer, the content of the styrene compound in the total mass (total content) of the monomers can usually be appropriately set within the range of 50 mass% or more and less than 100 mass%.

<RAFT Agent>
As the RAFT agent, any RAFT agent that is usually used in RAFT polymerization reactions can be used without any particular limitation.
Examples of such RAFT agents include compounds containing a thiocarbonylthio (-C(=S)-S-) group. Specific examples include dithiobenzoate compounds, aromatic or aliphatic heterocyclic carbodithioate compounds, trithiocarbonate compounds, dithiocarbamate compounds, dithiocarbonate compounds, and xanthate compounds. In addition, compounds having a disulfide structure that are usually used as RAFT agent precursors can also be used. Examples of such compounds having a disulfide structure include bis(thiobenzoyl) disulfide, bis(dodecylsulfanylthiocarbonyl) disulfide, and N,N'-dimethyl-N,N'-di(4-pyridinyl)thiuram disulfide.

一般式［２］中、Ｒ^５及びＲ^６は、それぞれ独立して、置換基を有する又は無置換の炭素数１～２０のアルキル基を表し、この置換基は、ヒドロキシ基、カルボキシ基、シアノ基、ハロゲノ基、炭素数１～２０のアルコキシ基、炭素数２～２１のアルコキシカルボニル基、炭素数１～２０のアルキルチオ基、置換基として炭素数１～２０のアルキル基を有するアミノ基、炭素数６～１４のアリール基、炭素数６～１４のアリールオキシ基、アルコキシポリアルキレングリコールカルボニル基、又はＮ－スクシンイミジルオキシカルボニル基を表す。 The RAFT agent used in the production method of the present invention is preferably a compound represented by the following general formula [2] or [3] in terms of polymerization activity, control of molecular weight distribution, and stability of the compound over time.

In the general formula [2], ^R5 and ^R6 each independently represent a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, and this substituent represents a hydroxy group, a carboxy group, a cyano group, a halogeno group, an alkoxy group having 1 to 20 carbon atoms, an alkoxycarbonyl group having 2 to 21 carbon atoms, an alkylthio group having 1 to 20 carbon atoms, an amino group having an alkyl group having 1 to 20 carbon atoms as a substituent, an aryl group having 6 to 14 carbon atoms, an aryloxy group having 6 to 14 carbon atoms, an alkoxypolyalkylene glycolcarbonyl group, or an N-succinimidyloxycarbonyl group.

The alkyl group having 1 to 20 carbon atoms which can be represented by ^R5 and ^R6 is an unsubstituted or substituted alkyl group, and may be linear, branched or cyclic, preferably linear or branched. The alkyl groups which can be represented by ^R5 and ^R6 may be the same or different from each other.
The number of carbon atoms in the alkyl group which can be represented by ^R5 and ^R6 is appropriately determined within the range of 1 to 20, and is preferably 1 to 12.

Substituents that the alkyl groups represented by ^R5 and ^R6 may have will be described below.
The halogeno group includes a halogen atom, for example, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
The alkoxy group having 1 to 20 carbon atoms, the alkoxycarbonyl group having 2 to 21 carbon atoms, the aryl group having 6 to 14 carbon atoms, and the aryloxy group having 6 to 14 carbon atoms are the same as the corresponding groups which may be taken as R ¹ above.
The amino group having an alkyl group having 1 to 20 carbon atoms as a substituent may have one or two alkyl groups having 1 to 20 carbon atoms as a substituent, and examples of such an amino group include an N-alkylamino group and an N,N-dialkylamino group. The alkyl group of the amino group is the same as the alkyl group having 1 to 20 carbon atoms that can be taken as ^R1 .
The alkylthio group having 1 to 20 carbon atoms may be linear, branched or cyclic. The alkylthio group preferably has 1 to 6 carbon atoms, and more preferably has 1 to 4 carbon atoms.
The alkoxy polyalkylene glycol carbonyl group means a group represented by -CO-O-(R ^A5 -O)x-R ^A6 , where R ^A5 represents an alkylene group and R ^A6 represents an alkyl group. The alkylene group that can be taken as R ^A5 includes an alkylene group having 1 to 20 carbon atoms, which may be any of a straight chain, branched chain, or cyclic chain. The number of carbon atoms in this alkylene group R ^A5 is preferably 1 to 6, and more preferably 1 to 4. The x alkylene groups may be the same or different from each other. The alkyl group that can be taken as ^{R A6} includes an alkyl group having 1 to 20 carbon atoms, which may be any of a straight chain, branched chain, or cyclic chain. The number of carbon atoms in this alkylene group R ^A6 is preferably 1 to 6, and more preferably 1 to 4. The number of carbon atoms in the alkoxypolyalkylene glycol carbonyl group is the total number of carbon atoms in the carbonyl group, the x number of alkylene groups R ^A4 , and the alkyl group R ^A6 , and is determined by the number of carbon atoms in each group and x. x is an integer of 1 to 500, and preferably an integer of 30 to 250.

Among the above-mentioned substituents that the alkyl group that can be taken as R ⁵ and R ⁶ can have, a carboxy group, a cyano group, an alkoxycarbonyl group, an aryl group, an alkoxypolyalkylene glycol carbonyl group, and an N-succinimidyloxycarbonyl group are preferred, and a carboxy group, a cyano group, and an aryl group are more preferred. When the alkyl group that can be taken as R ⁵ and R ⁶ has a substituent, the number of the substituents is not particularly limited, and can be, for example, 1 to 4, and is preferably 1 or 2. When one alkyl group has two or more substituents, the combination of the substituents is not particularly limited and can be appropriately combined, and for example, the combination of the above-mentioned preferred substituents is preferred.

The substituents that the alkyl groups that can be taken as R ⁵ and R ⁶ may have may further have a substituent. Such substituents are not particularly limited, and include, for example, groups selected from the substituent Z described below. Specific examples include amide groups, alkoxycarbonyl groups, alkenyloxycarbonyl groups, etc., each of which has an alkyl group as a substituent or is unsubstituted. The alkyl group that the amide group has is the same as the alkyl group having 1 to 20 carbon atoms that can be taken as the above-mentioned R ^1. The alkoxycarbonyl group is the same as the alkoxycarbonyl group having 2 to 21 carbon atoms that can be taken as the above-mentioned R ^1. The further substituents that may be taken may have a substituent such as a hydroxy group or a methylcarbonyloxy group.

The compound represented by the above general formula [2] is a trithiocarbonate compound, and specific examples thereof are shown in the Examples and below, but the present invention is not limited thereto. In the following specific examples, C ₁₂ H ₂₅ represents a linear dodecyl group, and x is the same as x exemplified in the above alkoxypolyalkylene glycol carbonyl group.

一般式［３］中、Ｒ^７は、置換基を有する又は無置換の炭素数１～２０のアルキル基を表し、この置換基は、ヒドロキシ基、カルボキシ基、シアノ基、ハロゲノ基、炭素数１～２０のアルコキシ基、炭素数２～２１のアルコキシカルボニル基、炭素数１～２０のアルキルチオ基、置換基として炭素数１～２０のアルキル基を有するアミノ基、炭素数６～１４のアリール基、炭素数６～１４のアリールオキシ基、又はＮ－スクシンイミジルオキシカルボニル基を表し、Ａは、置換基として炭素数１～２０のアルキル基及び５～７員の環状構造からなる群から選ばれる基を有する、もしくは無置換のアミノ基、又は置換基として、ハロゲノ基、シアノ基、炭素数１～２０のアルキル基及び炭素数１～２０のアルコキシ基からなる群から選ばれる基を有する、もしくは無置換の５～７員の環状構造を表す。

In the general formula [3], R ⁷ represents a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, and the substituent is a hydroxy group, a carboxy group, a cyano group, a halogeno group, an alkoxy group having 1 to 20 carbon atoms, an alkoxycarbonyl group having 2 to 21 carbon atoms, an alkylthio group having 1 to 20 carbon atoms, an amino group having an alkyl group having 1 to 20 carbon atoms as a substituent, an aryl group having 6 to 14 carbon atoms, an aryloxy group having 6 to 14 carbon atoms, or an N-succinimidyloxycarbonyl group; A represents an unsubstituted amino group having a group selected from the group consisting of an alkyl group having 1 to 20 carbon atoms and a 5- to 7-membered cyclic structure as a substituent, or an unsubstituted 5- to 7-membered cyclic structure having a group selected from the group consisting of a halogeno group, a cyano group, an alkyl group having 1 to 20 carbon atoms, and an alkoxy group having 1 to 20 carbon atoms as a substituent.

The alkyl group having 1 to 20 carbon atoms which can be represented by ^R7 is an unsubstituted or substituted alkyl group, and may be straight-chain, branched-chain or cyclic, preferably straight-chain or branched-chain.
The number of carbon atoms in the alkyl group which can be represented by R ⁷ is appropriately determined within the range of 1 to 20, and is preferably 1 to 12, more preferably 1 to 6, and even more preferably 1 to 4.

The substituents which the alkyl group which can be taken as ^R7 can have are the same as the corresponding groups among the substituents which the alkyl group which can be taken as the above-mentioned ^R5 and ^R6 can have.
Among the above-mentioned substituents that the alkyl group that can be taken as R ⁷ can have, a carboxy group, a cyano group, an alkoxycarbonyl group, an aryl group, and an N-succinimidyloxycarbonyl group are preferred, and a cyano group, an alkoxycarbonyl group, and an aryl group are more preferred. When the alkyl group that can be taken as R ⁷ has a substituent, the number of the substituents is not particularly limited, and can be, for example, 1 to 4, and is preferably 1 or 2. When one alkyl group has two or more substituents, the combination of the substituents is not particularly limited and can be appropriately combined, and for example, the combination of the above-mentioned preferred substituents is preferred.
The alkyl group which can be ^R7 may be an unsubstituted alkyl group, but is preferably a substituted alkyl group.

The substituent that the alkyl group that can be R ⁷ can have may further have a substituent. Such a substituent is not particularly limited, and examples thereof include groups selected from the substituent Z described below.

In the above general formula [3], the amino group that can be taken as A is an unsubstituted amino group, or a substituted amino group having an alkyl group having 1 to 20 carbon atoms or a 5- to 7-membered cyclic structure as a substituent.
The alkyl group as a substituent that the amino group that can be represented by A can have is the same as the alkyl group having 1 to 20 carbon atoms that can be represented by ^R1 above. The 5- to 7-membered cyclic structure as a substituent that the amino group that can be represented by A can have is the same as the 5- to 7-membered cyclic structure that can be represented by A described below. The substituted amino group may have at least one substituent, but preferably has two. The two substituents may both be alkyl groups or cyclic structures, or one may be an alkyl group and the other a cyclic structure.

The 5- to 7-membered cyclic structure (ring group) which can be represented by A is an unsubstituted cyclic structure or a cyclic structure having, as a substituent, a halogeno group, a cyano group, an alkyl group having 1 to 20 carbon atoms, or an alkoxy group having 1 to 20 carbon atoms.
The cyclic structure is not particularly limited as long as it has a 5- to 7-membered cyclic structure, and may be an aromatic cyclic group or a non-aromatic cyclic group. This cyclic structure is preferably a 5- or 6-membered cyclic structure, and is usually a monocyclic structure. The cyclic structure may be a hydrocarbon cyclic group or a heterocyclic group. When the cyclic structure is a heterocyclic group, the heteroatom contained in the cyclic structure of the heterocyclic group is not particularly limited, and examples thereof include a nitrogen atom, an oxygen atom, a sulfur atom, a silicon atom, and a phosphorus atom. A heterocycle has one or more heteroatoms in the ring, and usually has 1 to 3 heteroatoms.
Examples of the cyclic structure include aromatic ring groups such as an aromatic hydrocarbon ring group or an aromatic heterocyclic group, and non-aromatic ring groups such as a saturated aliphatic hydrocarbon ring group, a saturated aliphatic heterocyclic group, an unsaturated aliphatic hydrocarbon ring group, or an unsaturated aliphatic heterocyclic group.
The aromatic hydrocarbon ring group and aromatic heterocyclic group are not particularly limited, and are preferably the same as the aryl group having 6 to 14 carbon atoms or the heteroaryl group having 6 to 14 carbon atoms that can be taken as ^R1 . The aromatic hydrocarbon ring group is preferably a benzene ring group. The aromatic heterocyclic group is preferably a nitrogen-containing heterocycle containing a nitrogen atom as a ring-constituting atom, and more preferably a pyrrole ring group, a pyrazole ring group, or a pyridine ring group.
The saturated aliphatic hydrocarbon ring group is not particularly limited, and examples thereof include the cycloalkyl groups described below for the substituent Z. Examples of the unsaturated aliphatic hydrocarbon ring group include ring groups obtained by removing one or two hydrogen atoms from each of two adjacent ring carbon atoms of a saturated aliphatic hydrocarbon ring group to convert the ring carbon atoms into a double bond or triple bond.
The saturated aliphatic heterocyclic group is not particularly limited, and examples thereof include aliphatic heterocyclic groups among the heterocyclic groups in the substituent Z described below. Examples of the unsaturated aliphatic heterocyclic group include ring groups obtained by removing one hydrogen atom each from two adjacent ring carbon atoms of a saturated aliphatic heterocyclic group to convert them into double bonds.
The cyclic structure is preferably an aromatic hydrocarbon ring group or an aromatic heterocyclic group, and more preferably a benzene ring group, a pyrrole ring group, a pyrazole ring group or a pyridine ring group.

Each of the substituents which the cyclic structure may have is preferably the same as each of the corresponding groups which may be taken as R ¹ above.
Among the above, the substituents possessed by the cyclic structure are preferably a cyano group, a halogeno group, an alkyl group having 1 to 20 carbon atoms, and an alkoxy group having 1 to 20 carbon atoms. When the cyclic structure has a substituent, the number of the substituents is not particularly limited, and for example, it can be 1 to 4 for a 5-membered cyclic structure, and 1 to 5 for a 6-membered cyclic structure, and both are preferably 1 to 3. When one of the cyclic structures has two or more substituents, the combination of the substituents is not particularly limited and can be appropriately combined, and for example, a combination of the above-mentioned preferred substituents is preferable.

In the compound represented by the above general formula [3], the combination of A and ^R7 is not particularly limited and can be appropriately combined. For example, the combination of the above preferred ones is preferable.

Compounds represented by the above general formula [3] include dithiocarbonate compounds, dithiocarbamate compounds, etc., specific examples of which include methyl-2-phenyl-2-(phenylcarbonothioylthio)acetate, as well as the compounds shown in the examples and below, but the present invention is not limited to these.

- Substituent Z -
Alkyl groups (preferably alkyl groups having 1 to 20 carbon atoms, for example, methyl, ethyl, isopropyl, tert-butyl, pentyl, heptyl, 1-ethylpentyl, benzyl, 2-ethoxyethyl, 1-carboxymethyl, etc.), alkenyl groups (preferably alkenyl groups having 2 to 20 carbon atoms, for example, vinyl, allyl, oleyl, etc.), alkynyl groups (preferably alkynyl groups having 2 to 20 carbon atoms, for example, ethynyl, butadiynyl, phenylethynyl, etc.), cycloalkyl groups (preferably cycloalkyl groups having 3 to 20 carbon atoms, for example, cyclopropyl, cyclopentyl, cyclohexyl, 4-methylcyclohexyl, etc.), In the specification, the term "alkyl group" generally includes cycloalkyl groups, but this will be described separately here.), aryl groups (preferably aryl groups having 6 to 26 carbon atoms, for example, phenyl, 1-naphthyl, 4-methoxyphenyl, 2-chlorophenyl, 3-methylphenyl, etc.), heterocyclic groups (preferably heterocyclic groups having 2 to 20 carbon atoms, more preferably a 5- or 6-membered heterocyclic group having at least one oxygen atom, sulfur atom, or nitrogen atom as a ring-constituting atom. Heterocyclic groups include aromatic heterocyclic groups and aliphatic heterocyclic groups. For example, a tetrahydropyran ring group, a tetrahydrofuran ring group, 2-pyridyl, 4-pyridyl, lysyl, 2-imidazolyl, 2-benzimidazolyl, 2-thiazolyl, 2-oxazolyl, pyrrolidone group, etc.), alkoxy group (preferably an alkoxy group having 1 to 20 carbon atoms, for example, methoxy, ethoxy, isopropyloxy, benzyloxy, etc.), aryloxy group (preferably an aryloxy group having 6 to 26 carbon atoms, for example, phenoxy, 1-naphthyloxy, 3-methylphenoxy, 4-methoxyphenoxy, etc.), heterocyclic oxy group (a group in which the above heterocyclic group is bonded to an -O- group), alkoxycarbonyl group (preferably an alkoxycarbonyl group having 2 to 20 carbon atoms, for example, ethoxycarbonyl, 2-ethylhexyloxy, xyloxycarbonyl, dodecyloxycarbonyl, etc.), aryloxycarbonyl groups (preferably aryloxycarbonyl groups having 6 to 26 carbon atoms, for example, phenoxycarbonyl, 1-naphthyloxycarbonyl, 3-methylphenoxycarbonyl, 4-methoxyphenoxycarbonyl, etc.), heterocyclic oxycarbonyl groups (groups in which the above heterocyclic groups are bonded to an -O-CO- group), substituted amino groups (preferably alkylamino groups having 1 to 20 carbon atoms, arylamino groups having 6 to 26 carbon atoms, for example, N,N-dimethylamino, N,N-diethylamino, N-ethylamino, anilino, etc.), sulfamoyl groups (-SO ₂ NH ₂ ), substituted sulfamoyl groups (preferably sulfamoyl groups having 1 to 20 carbon atoms, for example, N,N-dimethylsulfamoyl, N-phenylsulfamoyl, etc.), acyl groups (including alkylcarbonyl groups, alkenylcarbonyl groups, alkynylcarbonyl groups, arylcarbonyl groups, and heterocyclic carbonyl groups, preferably acyl groups having 1 to 20 carbon atoms, for example, acetyl, propionyl, butyryl, octanoyl, hexadecanoyl, acryloyl, methacryloyl, crotonoyl, benzoyl, naphthoyl, and nicotinoyl), acyloxy groups (alkylcarbonyloxy groups, alkenylcarbonyloxy groups, alkynylcarbonyloxy groups, heterocyclic carbonyloxy groups, etc. group, preferably an acyloxy group having 1 to 20 carbon atoms, for example, acetyloxy, propionyloxy, butyryloxy, octanoyloxy, hexadecanoyloxy, acryloyloxy, methacryloyloxy, crotonoyloxy, nicotinoyloxy, etc.), an aryloyloxy group (preferably an aryloyloxy group having 7 to 23 carbon atoms, for example, benzoyloxy, naphthoyloxy, etc.), a carbamoyl group (preferably a carbamoyl group having 1 to 20 carbon atoms, for example, N,N-dimethylcarbamoyl, N-phenylcarbamoyl, etc.), an acylamino group (preferably an acylamino group having 1 to 20 carbon atoms, for example, acetylamino, benzoylamino, etc.), an alkyl group, Examples of suitable arylthio groups include alkylthio groups (preferably alkylthio groups having 1 to 20 carbon atoms, such as methylthio, ethylthio, isopropylthio, and benzylthio), arylthio groups (preferably arylthio groups having 6 to 26 carbon atoms, such as phenylthio, 1-naphthylthio, 3-methylphenylthio, and 4-methoxyphenylthio), heterocyclic thio groups (groups in which the above-mentioned heterocyclic groups are bonded to an -S- group), alkylsulfonyl groups (preferably alkylsulfonyl groups having 1 to 20 carbon atoms, such as methylsulfonyl and ethylsulfonyl), arylsulfonyl groups (preferably arylsulfonyl groups having 6 to 22 carbon atoms, such as benzenesulfonyl), and alkylsilyl groups (preferably arylsulfonyl groups having 1 to 20 carbon atoms). alkylsilyl groups, for example, monomethylsilyl, dimethylsilyl, trimethylsilyl, triethylsilyl, etc.), arylsilyl groups (preferably arylsilyl groups having 6 to 42 carbon atoms, for example, triphenylsilyl, etc.), alkoxysilyl groups (preferably alkoxysilyl groups having 1 to 20 carbon atoms, for example, monomethoxysilyl, dimethoxysilyl, trimethoxysilyl, triethoxysilyl, etc.), aryloxysilyl groups (preferably aryloxysilyl groups having 6 to 42 carbon atoms, for example, triphenyloxysilyl, etc.), phosphite groups (-OPH(=O)(-OH)), substituted phosphite groups (preferably phosphite groups having 1 to 20 carbon atoms, for example, -OP(=O)(-OH)(R ^P )), phosphoryl group (-OPH ₂ (=O)), substituted phosphoryl group (preferably a phosphate group having 1 to 20 carbon atoms, for example, -OP(=O)(R ^P ) ₂ ), phosphonyl group (preferably a phosphonyl group having 1 to 20 carbon atoms, for example, -P(=O)(R ^P ) ₂ ), phosphinyl group (-P(=O)H ₂ ), substituted phosphinyl group (preferably a phosphinyl group having 1 to 20 carbon atoms, for example, -P(=O)(R ^P ) ₂ ), phosphonic acid group (-P(=O)(OH) ₂ ), substituted phosphonic acid group (preferably a phosphonic acid group having 1 to 20 carbon atoms, for example, -P(=O)(OR ^P ) ₂ ), sulfo group (sulfonic acid group), carboxy group, hydroxy group, sulfanyl group, cyano group, halogen atom (for example, fluorine atom, chlorine atom, bromine atom, iodine atom, etc.). R 1 ^P is a substituent (preferably a group selected from the substituent Z).
Each of the groups given as the substituent Z may be further substituted with the above-mentioned substituent Z.

The RAFT agent may be appropriately synthesized according to a known method, or a commercially available product may be used. Examples of the synthesis method include the methods described in Patent Documents 2 and 4 above, and the methods described in the literature cited in the examples described below.

In the production method of the present invention, the RAFT agent may be used alone or in combination of two or more kinds.
The amount of the RAFT agent used is not particularly limited and can be appropriately set depending on the target molecular weight of the styrene polymer, etc. As an example, the amount of the RAFT agent used can be set based on the following formula.
Target molecular weight of styrene polymer = {amount of monomer including styrene compound used (mol) / amount of RAFT agent used (mol)} x molecular weight of monomer including styrene compound + molecular weight of RAFT agent

<Azo Polymerization Initiator>
Azo polymerization initiators are considered to be less likely to cause hydrogen abstraction from monomers, etc., and can carry out polymerization reactions safely compared to peroxide polymerization initiators, contributing to control of molecular weight distribution in the production method of the present invention. In the production method of the present invention, among azo polymerization initiators, an azo polymerization initiator having a 10-hour half-life temperature of 90°C or higher is selected and used in combination with a RAFT agent to carry out a polymerization reaction at 110°C or higher. This makes it possible to safely proceed with the polymerization reaction of monomers at a high conversion rate even in a short time, and to produce a styrene polymer with a narrow molecular weight distribution.
The 10-hour half-life temperature is measured, for example, according to the method described in paragraph 0031 of the specification of Japanese Patent No. 6657883.

Examples of azo polymerization initiators having a 10-hour half-life temperature of 90° C. or higher include 2,2′-azobis(n-butyl-2-methylpropionamide) (10-hour half-life temperature: 110° C.), 2,2′-azobis(2,4,4-trimethylpentane) (10-hour half-life temperature: 110° C.), and the like.
The azo polymerization initiator may be appropriately synthesized, or a commercially available product may be used, such as an azo polymerization initiator manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.

In the production method of the present invention, the azo polymerization initiator may be used alone or in combination of two or more kinds.
The amount of the azo polymerization initiator used is not particularly limited, and can be appropriately set depending on the target molecular weight of the styrene polymer, etc. The molar ratio of the amount of the azo polymerization initiator used to the amount of the RAFT agent used [azo polymerization initiator:RAFT agent] is also not particularly limited, and as an example, from the viewpoint of reducing the degree of dispersion, it is preferably 1:1 to 1:100, and more preferably 1:2 to 1:75.

<Polymerization inhibitor>
The production method of the present invention can also be carried out in the presence of a polymerization inhibitor in addition to the RAFT agent and the azo polymerization initiator. Examples of the polymerization inhibitor include hydroquinone compounds and benzoquinone compounds, and specific examples thereof include hydroquinone compounds such as 4-tert-butylcatechol, hydroquinone, hydroquinone monomethyl ether, tert-butylhydroquinone, and dibutylhydroxytoluene, and benzoquinone compounds such as benzoquinone.
In the production method of the present invention, the polymerization inhibitor may be used alone or in combination of two or more kinds.
The amount of the polymerization inhibitor used is not particularly limited, and may be, for example, 10 to 3000 ppm, more preferably 10 to 1000 ppm, and even more preferably 20 to 200 ppm, per gram of monomer.

<Organic solvent>
The production method of the present invention can be carried out under solvent-free conditions or in an organic solvent, as described below.
The organic solvent may be any that is generally used in this field without any particular limitation. Examples include propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, ethyl lactate, toluene, xylene, anisole, butanol, methyl isobutyl ketone, butyl acetate, cyclohexanone, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, and dimethylsulfoxide. Among these, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, and ethyl lactate are preferred.
In the production method of the present invention, the organic solvent may be used alone or in combination of two or more kinds.
The amount of the organic solvent used cannot be uniquely determined because the viscosity of the solution varies depending on the type and amount of the monomer, etc. dissolved in the organic solvent. As an example, the amount of the organic solvent used can be such that the solid content of the monomer, RAFT agent, azo polymerization initiator, etc. becomes 10 to 80 mass %, and preferably becomes 25 to 70 mass %.

<Other ingredients>
In the production method of the present invention, in addition to the monomer, the RAFT agent, and the azo polymerization initiator, other components may be contained. The other components are not particularly limited, and include components that are usually used in the production of polymers, and components that are used depending on the application of the styrene polymer, and specifically, sensitizers and the like. The amount of the other components used is not particularly limited, and is appropriately set, and can be, for example, 0 to 5 parts by mass in the above solid content.
In the production method of the present invention, it is preferable not to use a peroxide polymerization initiator as a polymerization initiator, in that deterioration of the properties of the styrene polymer caused by hydrogen abstraction, etc. can be suppressed and safety can be ensured. In the present invention, not using a peroxide polymerization initiator includes an embodiment in which the amount of the peroxide polymerization initiator used is 0 mass %, as well as an embodiment in which the peroxide polymerization initiator is used to the extent that the effects of the present invention are not impaired, for example, less than 1 mass % of the solid content.

<Method of producing styrene polymer>
Next, the production method of the present invention will be specifically described.
(Polymerization reaction process)
In the production method of the present invention, a monomer containing a styrene compound is polymerized at 110° C. or higher in the presence of a RAFT agent and an azo polymerization initiator having a 10-hour half-life temperature of 90° C. or higher.
In this polymerization reaction, the amounts of the monomer, the RAFT agent and the azo polymerization initiator used are as described above. This polymerization reaction can be carried out in the organic solvent or under solvent-free conditions. In the present invention, the solvent-free conditions refer to conditions in which no solvent is actively used in the polymerization reaction, and do not mean that the reaction is free of solvents that are inevitably mixed in. Specifically, the solvent-free conditions include an embodiment in which the amount of solvent used is less than 1% by mass, in addition to an embodiment in which the amount of solvent used is 0% by mass.
This polymerization reaction may be carried out without stirring or with stirring using a general reaction apparatus.
The polymerization reaction may be a batch reaction (lump-sum charging, dropwise addition of monomer and initiator) or a flow reaction (continuous reaction). From the viewpoint of safety, dropwise polymerization is preferred.

The reaction temperature (polymerization temperature) may be 110° C. or higher, preferably 112° C. or higher, and more preferably 115° C. or higher. The upper limit temperature is not particularly limited as long as it is equal to or lower than the boiling point of the monomer used at normal pressure (1 atm), and can be appropriately set in consideration of the decrease in conversion rate due to volatilization of the monomer, safety, etc. As an example of the upper limit temperature, it can be, for example, less than 160° C., and preferably less than 140° C.
The reaction time cannot be uniquely determined due to changes in the reaction scale, reaction temperature, etc., but can be, for example, 10 to 24 hours. Since the production method of the present invention shows a high conversion rate even in a short time, the reaction time can be set short, for example, to 5 to 12 hours.

The environment in which the polymerization reaction is carried out is not particularly limited, and is usually preferably in an inert gas environment. In addition, when carrying out the polymerization reaction, it is preferable to degas (deoxygenate) the raw material mixture. By these operations, the polymerization reaction can proceed more quickly and uniformly, and a narrower molecular weight distribution can be achieved. The method for degassing the raw material mixture is not particularly limited and any known method can be applied, for example, a method of bubbling an inert gas into the raw material mixture in a reaction vessel. When carrying out the polymerization reaction in an inert gas environment, any method that can replace the polymerization reaction environment (usually in a reaction vessel) with an inert gas can be applied without any particular limitation. For example, a method of filling an inert gas into a reaction vessel and a method of circulating an inert gas into a reaction vessel can be used. Examples of the inert gas used include various gases that are usually used, such as nitrogen gas and argon gas.

As described above, the monomers can be polymerized (RAFT) to synthesize (produce) a styrene polymer.

(Other processes)
In the production method of the present invention, after the polymerization reaction is completed, the styrene polymer is isolated and recovered. At that time, a step of purifying the styrene polymer may be carried out. As the purification method, a conventional method may be applied, for example, a precipitation method, a membrane separation method, etc.
In the production method of the present invention, a step of removing the cleavage residue of the RAFT agent bonded to the terminal of the obtained styrene polymer by a conventional method may be carried out.
In the production method of the present invention, when a polymerization inhibitor is used, a step of removing the polymerization inhibitor or its decomposition products from the reaction mixture after the polymerization reaction may be carried out, but this step is not necessary since it is costly and there is a concern of the generation of unexpected polymers, etc. The step of removing the polymerization inhibitor, etc. is not particularly limited, and examples thereof include ordinary methods such as distillation and celite filtration.

In general, when the reaction temperature is increased in a method for polymerizing a monomer, the molecular weight distribution of the resulting polymer tends to broaden. However, the production method of the present invention having the above-mentioned polymerization reaction step can suppress the broadening of the molecular weight distribution even when the reaction temperature is increased, and can safely produce a styrene polymer having a narrow molecular weight distribution at a high conversion rate even in a short time.
Although the conversion rate cannot be determined univocally due to changes in the type and amount of monomer, solid content, reaction time, etc., as one example, it is 65% or more after a 5-hour polymerization reaction, which is higher than the conversion rates of conventional polymerization methods, such as the method of Patent Document 2 (52% after 48 hours). In the production method of the present invention, the conversion rate tends to improve as the solid concentration and reaction temperature are increased, and also tends to increase as the reaction time is extended.

<Styrene polymer>
As described above, the styrene polymer can be obtained by the manufacturing method of the present invention. In the present invention, the styrene polymer may have a component (styrene component) derived from a styrene compound in its main chain, and includes a styrene homopolymer having a styrene component in its main chain, and a copolymer of styrene and another polymerizable compound having a styrene component and a component (polymerizable compound component) derived from the other polymerizable compound in its main chain. However, the content of the styrene component in the copolymer is 50% by mass or more based on the total components of the copolymer, and the content of the styrene component can be appropriately set within a range of 50% by mass or more and less than 100% by mass depending on the characteristics, applications, etc.
The styrene polymer can have a linear or branched (graft structure, multi-branched structure) molecular structure by selecting other polymerizable compounds, for example, by using a polyfunctional polymerizable compound.
The styrene polymer usually has a cleavable residue of a RAFT agent bonded to its end, but this is not limited thereto.

The number average molecular weight (Mn) of the styrene polymer obtained by the production method of the present invention is not particularly limited, but is, for example, preferably 1,000 to 50,000, more preferably 3,000 to 50,000, further preferably 5,000 to 40,000, and particularly preferably 7,000 to 20,000.
The molecular weight distribution (mass average molecular weight Mw/number average molecular weight Mn) of the styrene polymer is in a narrow range, and can be, for example, 1.30 or less, preferably 1.25 or less, and can be narrowed to 1.20 or less. In particular, even if the number average molecular weight Mn of the styrene polymer is 7,000 or more, the molecular weight distribution remains narrow in the above range, and a high molecular weight and low dispersity can be realized. The method for measuring each molecular weight will be described in the examples below.

The styrene polymer obtained by the manufacturing method of the present invention can be used for various applications, such as optical applications, patterning materials (e.g., resist applications), life science applications, dispersion materials, adhesives, elastomer materials, porous materials, drug delivery applications, and surface modifiers. In particular, the styrene polymer has a narrow molecular weight distribution within the above range, and is therefore suitable for use in resist applications.

The present invention will be described in more detail below with reference to examples, but the present invention should not be construed as being limited thereto. In the following examples, "parts" and "%" representing compositions are based on mass unless otherwise specified.

Example 1
9.75 g (93.6 mmol) of styrene, 5.9 g of propylene glycol monomethyl ether acetate (PGMEA), and 0.193 g (0.663 mmol) of S,S'-dibenzyl trithiocarbonate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were dissolved in a 50 mL separable flask equipped with a stirrer, a cooling tube, a thermometer, and a nitrogen inlet tube. 4.14 g (0.133 mmol as a polymerization initiator) of 1 mass % PGMEA solution of 2,2'-azobis(n-butyl-2-methylpropionamide) (VAm-110 (trade name), manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was further added to the obtained solution to prepare a PGMEA solution with a solid content of 50 mass %, and nitrogen bubbling was performed for 30 minutes. A polymerization reaction was performed at 120 ° C. for 5 hours under a nitrogen atmosphere to produce polystyrene as a styrene polymer. The conversion rate of styrene in this polymerization reaction, as well as the weight average molecular weight (Mw), number average molecular weight (Mn) and molecular weight distribution (Mw/Mn) of the styrene polymer were measured and calculated by the following methods. The results are shown in Table 1.

(Measurement and calculation of conversion rate)
In the present invention, the conversion rate of the styrene compound and other monomers is measured by high performance liquid chromatography (HPLC) and is calculated from the values measured under the following conditions, assuming that the monomer peak area intensity of the pre-polymerization solution is 0% conversion rate.
Equipment: Prominence (manufactured by Shimadzu Corporation)
Column: Wakopak Ultra C18-5 4.6 x 150 mm (FUJIFILM Wako Pure Chemical Industries, Ltd.)
Detection wavelength: 254 nm
Column temperature: 30°C
Mobile phase: Acetonitrile / distilled water / phosphoric acid = (Solution A) 100 / 900 / 1 volume part and (Solution B) 900 / 100 / 1 volume part Gradient solution flow rate: 1.0 mL / min

(Measurement of molecular weight)
In the present invention, the mass average molecular weight (Mw) or number average molecular weight (Mn) of a styrene polymer refers to a mass average molecular weight or number average molecular weight obtained by gel permeation chromatography (GPC) in terms of standard polystyrene, and is a value measured by the following method and conditions.
Apparatus: SHODEX (registered trademark) GPC-101 (manufactured by Showa Denko K.K.)
Detector: Differential refractometer (RI detector)
Precolumn: KF-G (Showa Denko K.K.)
Column: The following three columns are connected in order (all manufactured by Showa Denko K.K.)
KF-803, KF-804, KF-805
Column temperature: 40°C
Mobile phase: THF
Flow rate: 1.0mL/min

<Examples 2 to 11>
Each polystyrene was produced by carrying out a polymerization reaction in the same manner as in the production method of Example 1, except that the RAFT agent and the azo polymerization initiator were changed to those shown in Table 1. The conversion rate in each example, and further the weight average molecular weight (Mw), number average molecular weight (Mn) and molecular weight distribution (Mw/Mn) of the styrene polymer were calculated or measured in the same manner as in Example 1. The results are shown in Table 1 or Table 2.

Example 12
A polymerization reaction was carried out in the same manner as in the production method of Example 1, except that 9.75 g (60.1 mmol) of 4-acetoxystyrene was used instead of styrene, and 0.270 g (0.668 mmol) of 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) was used instead of S,S-dibenzyltrithiocarbonic acid, to produce poly(4-acetoxystyrene) as a styrene polymer. The conversion rate in this polymerization reaction, and further the weight average molecular weight (Mw), number average molecular weight (Mn) and molecular weight distribution (Mw/Mn) of poly(4-acetoxystyrene) were calculated or measured in the same manner as in Example 1. The results are shown in Table 2.

Example 13
A polymerization reaction was carried out in the same manner as in the production method of Example 12, except that 9.75 g (55.3 mmol) of 4-tert-butoxystyrene was used instead of 4-acetoxystyrene, to produce poly(4-tert-butoxystyrene) as a styrene polymer. The conversion rate in this polymerization reaction, as well as the weight average molecular weight (Mw), number average molecular weight (Mn) and molecular weight distribution (Mw/Mn) of poly(4-tert-butoxystyrene) were calculated or measured in the same manner as in Example 1. The results are shown in Table 2.

<Example 14>
In the production method of Example 13, 4.87 g (27.6 mmol) of 4-tert-butoxystyrene was used instead of 9.75 g, and 4.87 g (38.0 mmol) of n-butyl acrylate was used, and the reaction temperature was set to 110° C., except that a polymerization reaction was carried out in the same manner as in the production method of Example 13 to produce poly(4-tert-butoxystyrene/n-butyl acrylate) as a styrene polymer. The conversion rate in this polymerization reaction, and further the weight average molecular weight (Mw), number average molecular weight (Mn) and molecular weight distribution (Mw/Mn) of poly(4-tert-butoxystyrene/n-butyl acrylate) were calculated or measured in the same manner as in Example 1. The results are shown in Table 2.

Example 15
A polymerization reaction was carried out in the same manner as in the production method of Example 13, except that 8.28 g (0.266 mmol as a polymerization initiator) of a 1% by mass solution of 2,2'-azobis(n-butyl-2-methylpropionamide) in PGMEA was used instead of 4.14 g in the production method of Example 13, to produce poly(4-tert-butoxystyrene) as a styrene polymer. The conversion rate in this polymerization reaction, as well as the weight average molecular weight (Mw), number average molecular weight (Mn) and molecular weight distribution (Mw/Mn) of poly(4-tert-butoxystyrene) were calculated or measured in the same manner as in Example 1. The results are shown in Table 2.

<Comparative Example 1>
A polymerization reaction was carried out in the same manner as in the production method of Example 3 to produce a styrene polymer, except that 2.19 g (0.133 mmol) of a 1 mass % PGMEA solution of 2,2'-azobis(isobutyronitrile) (AIBN, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used instead of the 1 mass % PGMEA solution of 2,2'-azobis(n-butyl-2-methylpropionamide) in the production method of Example 3. The conversion rate in this polymerization reaction, and further the weight average molecular weight (Mw), number average molecular weight (Mn) and molecular weight distribution (Mw/Mn) of the styrene polymer were calculated or measured in the same manner as in Example 1. The results are shown in Table 2.

<Comparative Example 2>
A polymerization reaction was carried out in the same manner as in the production method of Example 1 to produce a styrene polymer, except that no azo polymerization initiator was used in the production method of Example 1. The conversion rate in this polymerization reaction, and further the weight average molecular weight (Mw), number average molecular weight (Mn) and molecular weight distribution (Mw/Mn) of the styrene polymer were calculated or measured in the same manner as in Example 3. The results are shown in Table 2.

<Comparative Example 3>
A polymerization reaction was carried out in the same manner as in the production method of Example 1 to produce a styrene polymer, except that 0.270 g (0.668 mmol) of 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) was used instead of S,S-dibenzyltrithiocarbonic acid and the reaction temperature was changed to 90° C. The conversion rate in this polymerization reaction, and further the weight average molecular weight (Mw), number average molecular weight (Mn) and molecular weight distribution (Mw/Mn) of the styrene polymer were calculated or measured in the same manner as in Example 1. The results are shown in Table 2.

<Comparative Example 4>
A polymerization reaction was carried out in the same manner as in the production method of Example 1 to produce a styrene polymer, except that 3.25 g (0.133 mmol) of a 1 mass % PGMEA solution of 1,1'-azobis(cyclohexane-1-carbonitrile) (V-40, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used instead of the 1 mass % PGMEA solution of 2,2'-azobis(n-butyl-2-methylpropionamide) in the production method of Example 3. The conversion rate in this polymerization reaction, and further the weight average molecular weight (Mw), number average molecular weight (Mn) and molecular weight distribution (Mw/Mn) of the styrene polymer were calculated or measured in the same manner as in Example 3. The results are shown in Table 2.

In Tables 1 and 2, PGMEA represents propylene glycol monomethyl ether acetate, nBA represents n-butyl acrylate, and the names in the RAFT agent and azo polymerization initiator columns represent the respective compounds described below.
The RAFT agents used in the examples and comparative examples are shown below. RAFT-007 was synthesized based on the method described in Macromolecules (2005), 38(23), 9518-9525, and RAFT-008 was synthesized based on the method described in Journal of Polymer Science, Part A: Polymer Chemistry (2013), 51(5), 1066-1078.

The azo polymerization initiators used in the examples and comparative examples are shown below.

The results shown in Tables 1 and 2 reveal the following.
In Comparative Example 1 and Comparative Example 4, in which azoisobutyronitrile (AIBN) or 1,1'-azobis(cyclohexane-1-carbonitrile) (V-40), which have a low 10-hour half-life temperature of 65°C or 88°C, was used as the azo polymerization initiator, the conversion rate was 47% or 61%, even when the reaction temperature was increased to 120°C, and the conversion rate was not sufficient. In Comparative Example 2, in which no azo polymerization initiator was used, the conversion rate decreased to 37%. On the other hand, in Comparative Example 3, in which an azo polymerization initiator with a 10-hour half-life temperature of 110°C was used in combination with a RAFT agent but the reaction temperature was set to 90°C, the conversion rate significantly decreased to 16%.
In contrast, in Examples 1 to 15, in which an azo polymerization initiator having a 10-hour half-life temperature of 110°C was used in combination with a RAFT agent to carry out a polymerization reaction at 120°C, a styrene polymer could be safely produced at a high conversion rate exceeding 65% in a short period of time, such as 5 hours, while maintaining a narrow molecular weight distribution of less than 1.30. Moreover, the resulting styrene polymers all had number-average molecular weights and mass-average molecular weights of 7,000 or more. Thus, the production method of the present invention can safely produce a styrene polymer having a narrow molecular weight distribution at a high conversion rate even in a short period of time.

Although the present invention has been described in conjunction with its embodiments, we do not intend to limit our invention to any of the details of the description unless specifically stated otherwise, and believe that the appended claims should be interpreted broadly without departing from the spirit and scope of the invention as set forth in the appended claims.

This application claims priority to Patent Application No. 2022-012761, filed in Japan on January 31, 2022, the contents of which are incorporated herein by reference as part of the present specification.

Claims (12)

A method for producing a styrene polymer, in which a monomer containing a styrene compound is polymerized at 110°C or higher in the presence of a reversible addition-fragmentation chain transfer agent and an azo polymerization initiator having a 10-hour half-life temperature of 90°C or higher. The method according to claim 1, wherein the styrene compound is a compound represented by the following general formula [1]:

In the general formula [1], n R ^1s each independently represent a hydroxy group, a carboxy group, a sulfonic acid group, a phosphoric acid group, a phosphonic acid group, a boronic acid group, a cyano group, a nitro group, a halogeno group, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkoxyalkoxy group having 2 to 21 carbon atoms, an alkoxycarbonyl group having 2 to 21 carbon atoms, an alkylcarbonyloxy group having 2 to 21 carbon atoms, an alkylsulfonic acid group having 1 to 20 carbon atoms, a phosphino group having an aryl group having 6 to 14 carbon atoms as a substituent, an amino group having two alkyl groups having 1 to 20 carbon atoms as a substituent, a carbon atom as a substituent, a silyl group having an alkyl group having 1 to 20 carbon atoms or an alkoxy group having 1 to 20 carbon atoms, a silyl ether group having three alkyl groups having 1 to 20 carbon atoms or aryl groups having 6 to 14 carbon atoms as substituents, an aryl group having 6 to 14 carbon atoms, an aryloxy group having 6 to 14 carbon atoms, an arylalkyl group having 7 to 20 carbon atoms, a heteroaryl group having 1 to 13 carbon atoms, a heteroaryloxy group having 1 to 13 carbon atoms, a heteroarylalkyl group having 2 to 19 carbon atoms, a heterocycloalkyl group having 1 to 13 carbon atoms, or a heterocycloalkyloxy group having 1 to 13 carbon atoms; R ² represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and n represents an integer of 0 to 5. The method of claim 1, wherein the content of the styrene compound is 50% by mass or more based on the total content of the monomers. The method of claim 1, wherein the monomer comprises only a styrene compound. The manufacturing method described in claim 1, wherein the azo polymerization initiator is 2,2'-azobis(n-butyl-2-methylpropionamide) or 2,2'-azobis(2,4,4-trimethylpentane). The method of claim 1, wherein the molar ratio of the azo polymerization initiator to the reversible addition-fragmentation chain transfer agent [azo polymerization initiator: reversible addition-fragmentation chain transfer agent] is 1:1 to 1:100. The method according to claim 1, wherein the reversible addition-fragmentation chain transfer agent is a compound represented by the following general formula [2] or [3]:

In the general formula [2], ^R5 and ^R6 each independently represent a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, and the substituent is a hydroxy group, a carboxy group, a cyano group, a halogeno group, an alkoxy group having 1 to 20 carbon atoms, an alkoxycarbonyl group having 2 to 21 carbon atoms, an alkylthio group having 1 to 20 carbon atoms, an amino group having an alkyl group having 1 to 20 carbon atoms as a substituent, an aryl group having 6 to 14 carbon atoms, an aryloxy group having 6 to 14 carbon atoms, an alkoxypolyalkylene glycolcarbonyl group, or an N-succinimidyloxycarbonyl group.

In the general formula [3], R ⁷ represents a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, and the substituent is a hydroxy group, a carboxy group, a cyano group, a halogeno group, an alkoxy group having 1 to 20 carbon atoms, an alkoxycarbonyl group having 2 to 21 carbon atoms, an alkylthio group having 1 to 20 carbon atoms, an amino group having an alkyl group having 1 to 20 carbon atoms as a substituent, an aryl group having 6 to 14 carbon atoms, an aryloxy group having 6 to 14 carbon atoms, or an N-succinimidyloxycarbonyl group; A represents an unsubstituted amino group having a group selected from the group consisting of an alkyl group having 1 to 20 carbon atoms and a 5- to 7-membered cyclic structure as a substituent, or an unsubstituted 5- to 7-membered cyclic structure having a group selected from the group consisting of a halogeno group, a cyano group, an alkyl group having 1 to 20 carbon atoms, and an alkoxy group having 1 to 20 carbon atoms as a substituent. The method of claim 1, wherein the polymerization is carried out in the presence of a polymerization inhibitor. The manufacturing method described in claim 8, wherein the polymerization inhibitor is selected from the group consisting of 4-tert-butylcatechol, hydroquinone, hydroquinone monomethyl ether, benzoquinone, tert-butylhydroquinone and dibutylhydroxytoluene. The manufacturing method described in claim 8, wherein the amount of the polymerization inhibitor used is 10 to 3000 ppm per 1 g of the monomer. The method of claim 8, wherein a step of removing the polymerization inhibitor from the reaction mixture after the polymerization is not performed. The process according to claim 1 , wherein the polymerization is carried out in an organic solvent or under solvent-free conditions.