Radical polymerization control agent, composition for radical polymerization, and method for producing polymer

Abstract

The present invention provides a radical polymerization control agent comprising an organic compound (A) in which the difference between the electron energy of the highest occupied molecular orbital (HOMO) and the electron energy of the lowest unoccupied molecular orbital (LUMO) is 0.0770-0.130 Hartree. Such a radical polymerization control agent has a high molecular weight controllability and a high polymerization rate. Therefore, said radical polymerization control agent makes it possible to synthesize a polymer at a high polymerization rate with high productivity while precisely controlling the molecular arrangement.

Description

Radical polymerization controller, composition for radical polymerization, and method for producing polymer

[0001] The present invention relates to a radical polymerization controller used in a polymerization process for polymerizing a polymerizable monomer by controlled radical polymerization, and also to a composition for radical polymerization and a method for producing a polymer using such a radical polymerization controller.

[0002] Polyvinyl alcohol resin is a crystalline, water-soluble polymer material. Taking advantage of its excellent water solubility and film-forming properties (strength, oil resistance, film-forming ability, oxygen gas barrier properties, etc.), it is widely used in emulsifiers, suspending agents, surfactants, fiber processing agents, various binders, paper processing agents, adhesives, films, etc. Conventional polyvinyl alcohols with different degrees of saponification and polymerization have been used depending on the application. Various modified polyvinyl alcohols have also been proposed, in which special functions are imparted by introducing functional groups into polyvinyl alcohol.

[0003] Polyvinyl alcohol is industrially produced by saponifying polyvinyl acetate obtained by radical polymerization of vinyl acetate. In the radical polymerization of vinyl acetate, various side reactions such as chain transfer reactions and recombination termination reactions occur concomitantly, making it generally difficult to precisely control the molecular arrangement and terminal structure of the resulting polyvinyl acetate (and polyvinyl alcohol).

[0004] In recent years, advances in so-called living radical polymerization technology have led to the development of several methods for controlling the radical polymerization of vinyl acetate. For example, a method has been proposed for obtaining polyvinyl acetate with a precisely controlled structure by conducting the radical polymerization of vinyl acetate in the presence of a radical polymerization initiator and a specific control agent. In this polymerization reaction, the growing radical end of the polyvinyl acetate molecular chain covalently bonds with the control agent to form a dormant species, and the polymerization proceeds while an equilibrium is formed between the dormant species and the radical species generated by its dissociation. This type of polymerization reaction is called controlled radical polymerization.

[0005] However, it has been difficult to obtain high-molecular-weight polyvinyl acetate using conventional controlled radical polymerization methods. This is thought to be because the radicals generated at the terminals of head-to-head bonds (bonds between adjacent acetyl groups in vinyl acetate), which are generated with a certain probability during polymerization, are extremely thermally unstable, causing the equilibrium to shift significantly toward the dormant species, preventing further polymerization reaction progress. On the other hand, if the polymerization temperature is increased to promote thermal dissociation of the dormant species, the reaction proceeds, but controllability deteriorates. Therefore, it has been extremely difficult to obtain high-molecular-weight polyvinyl acetate while maintaining controllability.

[0006] To address these issues, a method has been proposed for synthesizing high-molecular-weight polyvinyl acetate with a controlled structure by controlled radical polymerization using an organic cobalt complex as a control agent. In this polymerization reaction, the growing radical end of the polyvinyl acetate molecular chain covalently bonds with the cobalt atom of the organic cobalt complex to form a dormant species, and polymerization proceeds while an equilibrium is formed between the dormant species and the radical species generated by its dissociation. For example, Non-Patent Document 1 reports the synthesis of polyvinyl acetate with a number-average molecular weight (Mn) of 99,000 and a molecular weight distribution (Mw / Mn) of 1.33 by polymerizing vinyl acetate in the presence of cobalt(II) acetylacetonate.

[0007] Patent Document 1 describes that polyvinyl alcohol obtained by controlled radical polymerization has a problem of being significantly colored, but that polyvinyl alcohol with reduced coloration can be obtained by contacting a polyvinyl acetate solution obtained by controlled radical polymerization using an organic cobalt complex as a control agent with an aqueous solution containing a water-soluble ligand, extracting and removing the cobalt complex, and then saponifying the resulting solution.

[0008] However, such polymerization methods using metal complexes have the drawback that it is not easy to completely remove the used complex from the resulting polymer. Many transition metals are highly toxic, and the toxicity of the transition metals remaining in molded articles using the resulting polymers can pose environmental problems, making it difficult to use molded articles containing transition metals in food packaging, biomedical materials, and the like. The toxicity of unnecessary complexes or complexes removed from the polymer after the reaction can also pose environmental problems. Furthermore, complex removal requires the use of a large amount of extraction liquid, which complicates the process and increases costs. Furthermore, metal complexes are typically expensive and require complex synthesis.

[0009] Living radical polymerization methods that do not require the use of metal complexes are also known. For example, methods using nitroxyl-, iodine-, or dithioester-based compounds are known. However, these methods have the disadvantage that a special protecting group must be introduced into the growing polymer chain, and this protecting group is very expensive. Another disadvantage is that the polymerization reaction must be carried out at high temperatures (e.g., 110°C or higher). Another disadvantage is that the polymerization control of vinyl esters is insufficient, making it difficult to obtain high-molecular-weight polymers. Another disadvantage is that the resulting polymer is prone to coloration.

[0010] Non-Patent Document 2 describes that 2,2'-(1,2-Phenylenebis(azanediyl))bis(cyclohepta-2,4,6-trien-1-one) (tralen) and tropone, which are organic compounds containing only C, H, O, and N atoms, can control the radical polymerization of vinyl acetate, N-vinylpyrrolidone, and acrylonitrile. However, in this method, the polymerization rate is low even when a radical generator is added in large excess relative to the control agent, and it is easily conceivable that adding more radical generator to increase the polymerization rate would result in a deterioration in molecular weight controllability due to side reactions, etc., and this poses industrial problems in terms of safety and cost.

[0011] WO2017 / 170974 publication

[0012] Highly Efficient Cobalt-Mediated Radical Polymerization of Vinyl Acetate, Angewandte Chemie International Edition, 2005, vol.44, p1101-1104Reversible-deactivation radical polymerization of vinyl acetate mediated by tralen, an organomediator, Polymer chemistry, 2021, vol. 12, p5159-5167

[0013] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an organic radical polymerization inhibitor that has high molecular weight controllability, a high polymerization rate, and excellent productivity. Another object of the present invention is to provide a radical polymerization composition and a method for producing a polymer using such a radical polymerization inhibitor.

[0014] As a result of extensive research, the present inventors have found that by using, as a radical polymerization inhibitor, an organic compound (A) which is not an organometallic salt and in which the difference in electronic energy between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) is from 0.0770 Hartree to 0.130 Hartree, it is possible to achieve both high molecular weight controllability and excellent productivity due to an improved polymerization rate, and have thus completed the present invention.

[0015] That is, the present invention includes the following inventions: [1] A radical polymerization inhibitor comprising an organic compound (A) having a difference in electronic energy between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of 0.0770 Hartree or more and 0.130 Hartree or less. [2] The radical polymerization inhibitor according to [1], wherein the organic compound (A) is represented by the following formula (I):

[0016] [In formula (I), R １ , R ２are each independently an aryl group, an alkyl group, a halogen atom, a cyano group, a hydroxyl group, an amino group, a nitro group, a thiol group, or a group represented by the following formula (II), and R １ and R ２ may be linked to each other to form a ring. ３ , R ４ are each independently a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an alkenyl group, an alkoxy group, an amino group, a nitro group, a cyano group, an acetyl group, or a hydroxyl group, and n is 1 or more and 5 or less.

[0017] [In formula (II), X represents a heteroatom, a hydroxyl group, an amino group, a nitro group, a thiol group, or an NR ６ group or a cyano group, and R ５ is a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an alkenyl group, an alkoxy group, an amino group, a nitro group, a cyano group, an acetyl group, or a hydroxyl group, and R ６ is an alkyl group having 1 to 5 carbon atoms, a double line consisting of a solid line and a dashed line represents a single bond or a double bond, and * represents a bond.] [3] R １ is an aryl group, and R ２ is a radical polymerization inhibitor according to [2], wherein R is a group represented by the above formula (II), a halogen atom, a cyano group, a hydroxyl group, an amino group, a nitro group, or a thiol group. ２ is represented by the above formula (II), and R ５ [5] The radical polymerization controller according to [3], wherein R is an aryl group or an alkenyl group. １ is an alkyl group, and R ２ is a radical polymerization inhibitor according to [2], wherein R is a group represented by the above formula (II), a halogen atom, a cyano group, a hydroxyl group, an amino group, a nitro group, or a thiol group. ２ is represented by the above formula (II), and R ５ [7] The radical polymerization controller according to any one of [2] to [6], wherein X is an oxygen atom. [8] R １ is an aryl group, and R ２is an aryl group, a cyano group, or is represented by the above formula (II), X is a halogen atom, and R ５ [9] The radical polymerization inhibitor according to [2], wherein R is a hydrogen atom. ３ and R ４is a hydrogen atom.

[10] A composition for radical polymerization comprising an organic compound (A) having a difference in electron energy between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of 0.0770 Hartree or more and 0.130 Hartree or less, and a radical generator (B), wherein the molar ratio (B / A) of the radical generator (B) to the organic compound (A) is 0.5 to 20.

[11] The composition for radical polymerization according to

[10] , further comprising a monomer (Y), wherein the molar ratio (Y / A) of the monomer (Y) to the organic compound (A) is 300 to 30,000.

[12] A method for producing a polymer, comprising a polymerization step of obtaining a polymer by performing controlled radical polymerization of a monomer (Y) in the presence of an organic compound (A) having a difference in electronic energy between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of 0.0770 Hartree or more and 0.130 Hartree or less, and a radical generator (B).

[13] The method according to

[12] , wherein the monomer (Y) comprises an olefin, a vinyl ester, acrylic acid, an acrylic acid ester, an acrylamide-based monomer, a styrene-based monomer, an N-vinylamide-based monomer, or a dicarboxylic acid-based monomer.

[14] The method for producing a polymer according to

[13] , wherein the monomer (Y) comprises a vinyl ester or an N-vinylamide-based monomer.

[15] The method for producing a polymer according to

[14] , comprising a polymerization step of obtaining a vinyl ester-based block copolymer by sequentially performing controlled radical polymerization of a vinyl ester and controlled radical polymerization of a vinyl ester and a monomer other than a vinyl ester in the presence of an organic compound (A) and a radical generator (B).

[16] A method for producing a polymer according to

[14] , comprising a polymerization step of sequentially carrying out controlled radical polymerization of a vinylamide monomer and controlled radical polymerization of an N-vinylamide monomer and a monomer other than an N-vinylamide monomer in the presence of an organic compound (A) and a radical generator (B) to obtain an N-vinylamide block copolymer.

[17] A method for producing a polymer according to

[14] , comprising a polymerization step of carrying out controlled radical polymerization of a vinyl ester in the presence of an organic compound (A) and a radical generator (B) to obtain a vinyl ester polymer, and a saponification step of saponifying the obtained vinyl ester polymer to obtain a vinyl alcohol polymer.

[18] The method for producing a polymer according to

[17] , wherein the polymerization step involves controlled radical polymerization of a vinyl ester and a monomer other than the vinyl ester.

[0018] The radical polymerization controller of the present invention not only has high molecular weight controllability but also a high polymerization rate. Therefore, the radical polymerization controller enables polymers to be synthesized at a high polymerization rate and with good productivity while precisely controlling the molecular arrangement. The radical polymerization composition of the present invention or the method for producing a polymer of the present invention also enables polymers to be synthesized at a high polymerization rate and with good productivity while precisely controlling the molecular arrangement.

[0019] 1 is a plot of number average molecular weight (Mn) versus vinyl acetate conversion in Example 1. FIG. 2 is a plot of vinyl acetate conversion versus reaction time in Example 1.

[0020] The radical polymerization inhibitor of the present invention comprises an organic compound (A) having a difference in the electronic energy between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of 0.0770 Hartree or more and 0.130 Hartree or less. Such a radical polymerization inhibitor has high molecular weight controllability and a high polymerization rate, and therefore can produce polymers having desired molecular weight distributions and molecular arrangements with good productivity.

[0021] In the present invention, the difference in electronic energy between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) in the organic compound (A) must be 0.0770 Hartree or more and 0.130 Hartree or less. The difference in electronic energy of 0.0770 Hartree or more increases the polymerization rate. From this perspective, the difference in electronic energy is preferably 0.0800 Hartree or more, more preferably 0.0820 Hartree or more, even more preferably 0.0900 Hartree or more, even more preferably 0.100 Hartree or more, particularly preferably 0.110 Hartree or more, and most preferably 0.115 Hartree or more. On the other hand, the difference in electronic energy of 0.130 Hartree or less increases molecular weight controllability. From this viewpoint, the difference in electron energy is preferably 0.128 Hartree or less, more preferably 0.125 Hartree or less, even more preferably 0.123 Hartree or less, even more preferably 0.120 Hartree or less, particularly preferably less than 0.0940 Hartree, and most preferably 0.0935 Hartree or less. From the viewpoint of a particularly excellent balance between molecular weight controllability and polymerization rate, the difference in electron energy is preferably 0.0770 Hartree or more and less than 0.0940 Hartree, more preferably 0.0820 Hartree or more and less than 0.0940 Hartree, and even more preferably 0.0820 Hartree or more and 0.0935 Hartree or less.

[0022] The organic compound (A) used in the present invention is not particularly limited as long as the difference in electron energy between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) is within the above-mentioned range. However, from the viewpoint of further increasing the molecular weight controllability and polymerization rate, it is preferably a compound represented by the following formula (I):

[0023] [In formula (I), R １ , R ２ are each independently an aryl group, an alkyl group, a halogen atom, a cyano group, a hydroxyl group, an amino group, a nitro group, a thiol group, or a group represented by the following formula (II), and R １ and R ２may be linked to each other to form a ring. ３ , R ４ are each independently a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an alkenyl group, an alkoxy group, an amino group, a nitro group, a cyano group, an acetyl group, or a hydroxyl group. n is 1 or more and 5 or less. A single bond shown with a wavy line indicates that the configuration of the double bond adjacent to it is E or Z.

[0024] [In formula (II), X represents a heteroatom, a hydroxyl group, an amino group, a nitro group, a thiol group, or an NR ６ group or a cyano group, and R ５ is a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an alkenyl group, an alkoxy group, an amino group, a nitro group, a cyano group, an acetyl group, or a hydroxyl group, and R ６ represents an alkyl group having 1 to 5 carbon atoms, a double line consisting of a solid line and a dashed line represents a single bond or a double bond, and * represents a bond.]

[0025] In formula (I), R １ and R ２ The number of carbon atoms in the aryl group used as is preferably 6 to 15. The number of carbon atoms is more preferably 13 or less, even more preferably 12 or less, and particularly preferably 10 or less. Examples of the aryl group include a phenyl group, a biphenyl group, a naphthyl group, an anthryl group, an indenyl group, a fluorenyl group, a phenanthryl group, an indacenyl group, a phenalenyl group, an azulenyl group, a pyridyl group, and a furyl group, with a phenyl group being preferred. The aryl group may have a substituent, as long as it does not impair the effects of the present invention. Examples of such a substituent include an alkyl group, an alkoxy group, an amino group (including a monoalkylamino group and a dialkylamino group), a carboxyl group, an ester group, a silyl group, a sulfanyl group, a cyano group, a nitro group, a sulfo group, a formyl group, an aryl group, a halogen atom, a hydroxyl group, an ether group, and an alkenyl group. Examples of the alkyl group include R １ and R ２ Examples of the alkoxy group include those described below. ５Examples of the halogen atom used as X include those described below. Examples of the halogen atom used as X include those described below. From the standpoint of being superior in terms of the environment and safety, it is preferable that the aryl group does not have a substituent.

[0026] R １ and R ２ The number of carbon atoms in the alkyl group used as the alkyl group is preferably 1 to 10. The number of carbon atoms is more preferably 8 or less, even more preferably 6 or less, even more preferably 4 or less, and particularly preferably 2 or less. The alkyl group may be a straight-chain or branched-chain alkyl group, or a cyclic cycloalkyl group. Examples thereof include straight-chain or branched-chain alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, n-hexyl, isohexyl, 2-ethylhexyl, n-heptyl, n-octyl, n-nonyl, and n-decyl; and cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptanyl, cyclooctanyl, cyclononanyl, and cyclodecanyl. Among these, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl groups are preferred, and methyl is more preferred. The alkyl group may have a substituent within a range that does not impair the effects of the present invention. Examples of such a substituent include R １ and R ２ Examples of the substituent of the aryl group used as the substituent include those mentioned above. Examples of the alkyl group having a halogen atom include a trifluoromethyl group and a trichloromethyl group. From the standpoint of being superior in terms of the environment and safety, it is preferable that the alkyl group does not have a substituent.

[0027] R １ and R ２ Examples of the halogen atom used as the halogen atom include a chlorine atom, a fluorine atom, a bromine atom, and an iodine atom.

[0028] In formula (II), X represents a heteroatom, a hydroxyl group, an amino group, a nitro group, a thiol group, or NR ６ The heteroatom used as X is an oxygen atom; a halogen atom such as a chlorine atom, a fluorine atom, a bromine atom, or an iodine atom; a sulfur atom, etc. Here, the double line consisting of a solid line and a dashed line between X and the carbon atom indicates a single bond or a double bond. For example, when X is an oxygen atom, a sulfur atom, or a ═NR ６ Group (R ６ is an alkyl group having 1 to 5 carbon atoms), the bond between X and the carbon atom is a double bond. When X is a halogen atom, a cyano group, a hydroxyl group, an amino group, a nitro group, or a thiol group, the bond between X and the carbon atom is a single bond. X is preferably an oxygen atom or a chlorine atom, and more preferably an oxygen atom. Examples of structural formulas in which X in formula (II) is a specific group are shown below.

[0029]

[0030] In formula (II), R ５ is a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an alkenyl group, an alkoxy group, an amino group (including a monoalkylamino group and a dialkylamino group), a nitro group, a cyano group, an acetyl group, or a hydroxyl group, and is preferably an alkyl group, an aryl group, an alkenyl group, an alkoxy group, or a hydroxyl group. In view of the excellent balance between molecular weight controllability and polymerization rate and industrial advantages, R ５ is preferably an alkyl group, an alkoxy group, or a hydroxyl group, and more preferably an alkoxy group or a hydroxyl group. From the viewpoint of further increasing the molecular weight controllability and the polymerization rate, R ５ is preferably an aryl group or an alkenyl group.

[0031] R ５ Examples of the halogen atom used as the halogen atom include those mentioned above as the halogen atom used as X.

[0032] R ５ The number of carbon atoms in the alkyl group used as R is preferably 1 to 10. The number of carbon atoms is more preferably 8 or less, even more preferably 6 or less, even more preferably 4 or less, and particularly preferably 2 or less. ５The alkyl group used as R １ and R ２ Examples of the alkyl group used as the alkyl group include those mentioned above.

[0033] R ５ The number of carbon atoms in the aryl group used as R is preferably 6 to 15. The number of carbon atoms is more preferably 13 or less, even more preferably 12 or less, and particularly preferably 10 or less. ５ The aryl group used as R １ and R ２ Examples of the aryl group used as the aryl group include those mentioned above.

[0034] R ５ The number of carbon atoms in the alkenyl group used as is preferably 2 to 10. The number of carbon atoms is more preferably 8 or less. On the other hand, the number of carbon atoms is more preferably 4 or more. The alkenyl group may be a linear or branched alkenyl group, or a cyclic cycloalkenyl group. Examples of the alkenyl group include linear or branched alkenyl groups such as vinyl group, allyl group, methylvinyl group, propenyl group, butenyl group, pentenyl group, and hexenyl group; and cycloalkyl groups such as cyclopropenyl group, cyclobutenyl group, cyclopentenyl group, and cyclohexenyl group. The alkenyl group may have a substituent, as long as it does not impair the effects of the present invention. Examples of such a substituent include R １ and R ２ Examples of the substituent of the alkyl group used as the alkyl group include those mentioned above, and among them, an aryl group is preferred. From the viewpoint of environmental friendliness and safety, it is preferred that the alkenyl group has no substituent.

[0035] R ５The number of carbon atoms in the alkoxy group used as is preferably 1 to 10. The number of carbon atoms is more preferably 8 or less, even more preferably 6 or less, even more preferably 4 or less, and particularly preferably 1. Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, a pentyloxy group, an isopentyloxy group, a neopentyloxy group, a hexyloxy group, a cyclohexyloxy group, a heptyloxy group, an octyloxy group, a nonyloxy group, and a decyloxy group. Among these, a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, a sec-butoxy group, and a tert-butoxy group are preferred, and a methoxy group is more preferred. The alkoxy group may have a substituent as long as it does not impair the effects of the present invention. Examples of such a substituent include R １ and R ２ Examples of the substituent of the alkyl group used as R include those mentioned above. Also, examples of the substituent include an alkenyl group, and specifically, R ５ Examples of the alkenyl group used as the alkoxy group include those mentioned above. From the standpoint of being superior in terms of the environment and safety, it is preferable that the alkoxy group does not have a substituent.

[0036] In formula (I), R １ , R ２ may be linked to each other to form a ring.

[0037] In formula (I), n is 1 or more and 5 or less. n is preferably 4 or less, more preferably 3 or less, and particularly preferably 2 or less.

[0038] In formula (I), R ３ , R ４ are each independently a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an alkenyl group, an alkoxy group, an amino group, a nitro group, a cyano group, an acetyl group or a hydroxyl group, and are preferably a hydrogen atom.

[0039] R ３ and R ４ Examples of the halogen atom used as the halogen atom include those mentioned above as the halogen atom used as X.

[0040] R ３ and R ４ The number of carbon atoms in the alkyl group used as R is preferably 1 to 10. The number of carbon atoms is more preferably 8 or less, even more preferably 6 or less, even more preferably 4 or less, and particularly preferably 2 or less. ３ and R ４ The alkyl group used as R １ and R ２ Examples of the compounds that can be used include those mentioned above.

[0041] R ３ and R ４ The number of carbon atoms in the aryl group used as R is preferably 6 to 15. The number of carbon atoms is more preferably 13 or less, even more preferably 12 or less, and particularly preferably 10 or less. ３ and R ４ The aryl group used as R １ and R ２ Examples of the compounds that can be used include those mentioned above.

[0042] R ３ and R ４ The alkenyl group used as R preferably has 2 to 10 carbon atoms. The number of carbon atoms is more preferably 8 or less. On the other hand, the number of carbon atoms is more preferably 4 or more. ３ and R ４ As the alkenyl group used as R ５ Examples of the alkenyl group used as the alkyl group include those mentioned above.

[0043] R ３ and R ４ The number of carbon atoms in the alkoxy group used as R is preferably 1 to 10. The number of carbon atoms is more preferably 8 or less, even more preferably 6 or less, even more preferably 4 or less, and particularly preferably 1. ３ and R ４ The alkoxy group used as R ５ Examples of the alkoxy group used as the alkoxy group include those mentioned above.

[0044] In formula (I), the single bond represented by a wavy line indicates that the configuration of the adjacent double bond is E or Z. The configuration of the double bond is not particularly limited, but it is preferable that the one represented by formula (I) is the one represented by the following formula (I'):

[0045] [In formula (I'), R １ , R ２ , R ３ , R ４ and n has the same meaning as in formula (I).

[0046] From the viewpoint of further increasing the molecular weight controllability and polymerization rate, R １ is an aryl group, and R ２ is preferably a group represented by the above formula (II), a halogen atom, a cyano group, a hydroxyl group, an amino group, a nitro group, or a thiol group. ２ is represented by the above formula (II), and R ５ It is more preferable that X is an aryl group or an alkenyl group. It is also more preferable that X is oxygen. １ is an aryl group, and R ２ is represented by the above formula (II), or a halogen atom, a cyano group, a hydroxyl group, an amino group, a nitro group, or a thiol group, examples of the organic compound (A) include trans,trans-dibenzylideneacetone, chalcone, methyl (2E,4E)-5-phenyl-2,4-pentadienoate, and 7-phenyl-2,4,6-heptatrienoic acid, with trans,trans-dibenzylideneacetone and chalcone being preferred.

[0047] In formula (I), R １ is an aryl group, and R ２ is an aryl group, a cyano group, or is represented by the above formula (II), X is a halogen atom, and R ５ is preferably a hydrogen atom. In this case, examples of the organic compound (A) include trans-stilbene, cinnamic nitrile, and cinnamyl chloride. It is more preferred that the halogen atom used as X is a chlorine atom.

[0048] In view of the excellent balance between molecular weight controllability and polymerization rate and industrial advantages, R １ is an alkyl group, and R ２ is preferably a group represented by the above formula (II), a halogen atom, a cyano group, a hydroxyl group, an amino group, a nitro group, or a thiol group. ２ is more preferably represented by the above formula (II), and is more preferably represented by the above formula (II), wherein X is oxygen, R ５ is an alkoxy group or a hydroxyl group. Specific examples of the organic compound (A) include sorbic acid, methyl sorbate, 2,4,6-octatrienoic acid, 2,4,6,8-decatetraenoic acid, and 2,4,6,8,10-dodecapentaenoic acid, with sorbic acid and methyl sorbate being preferred.

[0049] It is also preferred that the organic compound (A) excludes benzalacetone, β-ionone, coumarin, cinnamic acid, methyl cinnamate, and cinnamic alcohol.

[0050] The method for producing a polymer of the present invention includes a polymerization step of obtaining a polymer by performing controlled radical polymerization of a monomer (Y) in the presence of an organic compound (A) having a difference in electronic energy between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of from 0.0770 Hartree to 0.130 Hartree, and a radical generator (B).

[0051] As the organic compound (A) used in the production method, the organic compound (A) described above as a radical polymerization inhibitor is used.

[0052] The radical generator (B) used in the polymerization step may be appropriately selected from conventionally known azo radical generators, peroxide radical generators, redox radical generators, etc. Examples of azo radical generators include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), etc. Examples of peroxide radical generators include percarbonate compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and diethoxyethyl peroxydicarbonate; perester compounds such as t-butyl peroxyneodecanate, α-cumyl peroxyneodecanate, and t-butyl peroxyneodecanate; acetylcyclohexylsulfonyl peroxide; diisobutyryl peroxide; and 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate. Furthermore, the radical generators can be prepared by combining the above-mentioned radical generators with peroxides such as potassium persulfate, ammonium persulfate, and hydrogen peroxide. Redox radical generators include those obtained by combining the above-mentioned peroxides with reducing agents such as sodium hydrogen sulfite, sodium hydrogen carbonate, tartaric acid, L-ascorbic acid, and Rongalit.

[0053] In the polymerization step, controlled radical polymerization of the monomer (Y) may be carried out in the presence of an organic compound (A), a radical generator (B), and a co-catalyst. By carrying out controlled radical polymerization of the monomer (Y) using a co-catalyst together with the organic compound (A) and the radical generator (B), the polymerization rate is further improved. Examples of the co-catalyst include Lewis bases such as water, N,N-dimethylformamide, dimethyl sulfoxide, pyridine, and triethylamine, and Lewis acids such as aluminum trichloride, tetraisopropyl orthotitanate, boron trifluoride, boron trichloride, and boron trifluoride diethyl ether. From an environmental perspective, it is preferable that the organic compound (A) does not form a metal salt.

[0054] Examples of polymerization methods include well-known methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. Among these, bulk polymerization, which involves polymerization without a solvent, and solution polymerization, which involves polymerization in various organic solvents, are commonly used. Bulk polymerization, which does not use a solvent or a dispersion medium, is preferred from the viewpoint of suppressing the decrease in propagating radical ends due to chain transfer reactions to the solvent or dispersion medium. On the other hand, solution polymerization may be preferable from the viewpoint of adjusting the viscosity of the reaction solution and controlling the polymerization rate. Examples of organic solvents used as solvents during solution polymerization include esters such as methyl acetate and ethyl acetate; aromatic hydrocarbons such as benzene and toluene; lower alcohols such as methanol and ethanol; and carbonates such as dimethyl carbonate and diethyl carbonate. Of these, esters, aromatic hydrocarbons, and dimethyl carbonate are preferred to prevent chain transfer. Furthermore, when the monomer (Y) contains vinyl acetate, alkali treatment in methanol is often performed after polymerization. Therefore, methanol is also preferably used as a polymerization solvent in consideration of processability. The amount of solvent used can be determined taking into account the number-average molecular weight of the target polymer and the viscosity of the reaction solution. For example, the mass ratio [solvent / monomer (Y)] is selected from the range of 0.01 to 10.

[0055] In the controlled radical polymerization used in the present invention, radicals generated by decomposition of the radical generator (B) first combine with a small number of monomers (Y) to produce short-chain polymers. The resulting radicals at the growing ends of the polymers then combine with the organic compound (A), forming dormant species in which the organic compound (A) is covalently bonded to the polymer ends. For a certain period after the start of the reaction, short-chain polymers are produced and converted to dormant species, and polymerization does not substantially proceed. This period is called the induction period. After the organic compound (A) is consumed, the reaction enters a growth period in which polymerization proceeds, and the molecular weights of most molecular chains in the reaction system increase at the same rate in proportion to the polymerization time. The time required for the polymerization of the monomer (Y), including the induction period and growth period, is usually 0.5 to 30 hours.

[0056] As described above, in the controlled radical polymerization of the present invention, theoretically, one polymer chain is produced from one molecule of the added organic compound (A). Therefore, the amount of organic compound (A) added to the reaction solution is determined taking into consideration the target number average molecular weight and conversion rate. From the viewpoint of obtaining a high molecular weight polymer, the molar ratio (Y / A) of the organic compound (A) to the monomer (Y) in the polymerization step is preferably 300 or more, more preferably 1000 or more, even more preferably 2000 or more, even more preferably 4000 or more, and particularly preferably 6000 or more. On the other hand, from the viewpoint of improving the activity rate of the propagating radical terminal, the molar ratio (Y / A) is preferably 30,000 or less, more preferably 25,000 or less, and even more preferably 20,000 or less. When the organic compound (A) or the monomer (Y) is added in multiple portions, the molar ratio (Y / A) is calculated using the total amount of each portion.

[0057] In the polymerization step, the molar ratio (B / A) of the radical generator (B) to the organic compound (A) is 0.5 to 20. If the number of moles of radicals generated is not greater than the number of moles of the organic compound (A), the polymerization reaction proceeds solely by the mechanism of thermal dissociation of the organic compound (A) from the dormant species, resulting in extremely slow polymerization rates depending on the reaction temperature. Therefore, considering that the radical generator (B) generates two radicals, both the radical generator (B) and the organic compound (A) must be added to the reaction solution in the polymerization step so that the molar ratio (B / A) of the radical generator (B) to the organic compound (A) is 0.5 or greater. Generally, the amount of active radicals supplied from the radical generator depends on the efficiency (initiator efficiency) of the radical generator, so in reality, some radical generator is deactivated without being used to form dormant. Therefore, the molar ratio (B / A) of the radical generator (B) to the organic compound (A) is preferably 0.6 or greater, more preferably 0.8 or greater. On the other hand, if the number of moles of radicals generated is too much greater than the number of moles of organic compound (A), the proportion of uncontrolled radical polymerization increases, and polymerization controllability decreases. The molar ratio of (B) to (A) (B / A) is preferably 15 or less, more preferably 10 or less, and even more preferably 5 or less. When the organic compound (A) or the radical generator (B) is added in multiple portions, the molar ratio (B / A) is calculated using the total amount of each portion.

[0058] The monomer contained in the monomer (Y) used in the polymerization step is not particularly limited as long as it is radically polymerizable, and examples thereof include olefins such as ethylene, propylene, and isobutylene; halogenated olefins such as vinyl chloride, vinyl fluoride, vinylidene chloride, and vinylidene fluoride; vinyl esters such as vinyl formate, vinyl acetate, vinyl trifluoroacetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, and vinyl versatate; vinylidene cyanide; acrylic acid; methacrylic acid; acrylic acid esters such as methyl acrylate, ethyl acrylate, N-propyl acrylate, i-propyl acrylate, N-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, and octadecyl acrylate; methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, and 2-hydroxyethyl methacrylate; dimethylaminoethyl acrylate , dimethylaminoethyl methacrylate and quaternized products thereof; acrylamide-based monomers such as acrylamide, N-methylolacrylamide, N,N-dimethylacrylamide, acrylamido-2-methylpropanesulfonic acid and its sodium salt; methacrylamide-based monomers such as methacrylamide, N,N-dimethylmethacrylamide, trimethyl[3-(methacryloylamino)propyl]aminium chloride; styrene-based monomers such as styrene, α-methylstyrene, p-styrenesulfonic acid and its sodium salt and potassium salt; N N-vinylamide monomers such as vinylacetamide, N-vinylpyrrolidone, N-vinylcaprolactam, N-vinylmethylacetamide, N-vinylformamide, N-vinylcarbazole, N-vinylimidazole, N-vinylphthalimide, N-vinyl-2,3-naphthalimide, and N-vinylindole; allyl monomers such as allyl acetate, allyl chloride, 3,4-diacetoxy-1-butene, 2-methylene-1,3-propanediol, 2-methylene-1,3-propanediol diacetate, allyl alcohol, and dimethylallyl alcohol;Preferred are vinyl cyanide monomers such as acrylonitrile and methacrylonitrile; vinyl ether monomers such as alkyl (C1 to C18) vinyl ether, hydroxyalkyl vinyl ether, and alkoxyalkyl vinyl ether; and dicarboxylic acid monomers such as maleic acid, monomethyl maleate, dimethyl maleate, maleic anhydride, itaconic acid, monomethyl itaconate, dimethyl itaconate, and itaconic anhydride. Olefins, vinyl esters, acrylic acid, acrylic acid esters, acrylamide monomers, styrene monomers, N-vinylamide monomers, and dicarboxylic acid monomers are more preferred, vinyl esters or N-vinylamide monomers are even more preferred, vinyl esters or N-vinylpyrrolidone are particularly preferred, and vinyl esters are most preferred. Monomer (Y) may contain one of these monomers or two or more of them. It is preferred that monomer (Y) contains one of these monomers as the main component. Here, the main component means the monomer contained in the monomer (Y) with the largest content. The content of the main component monomer in the monomer (Y) is preferably 30 mol % or more, more preferably 50 mol % or more, even more preferably 70 mol % or more, and particularly preferably 80 mol % or more.

[0059] The vinyl ester is preferably vinyl acetate from an economical viewpoint, and the acrylic ester is preferably methyl acrylate from an economical viewpoint.

[0060] In the production method of the present invention, a homopolymer may be obtained by using one type of monomer as the monomer (Y), or a copolymer may be obtained by using two or more types of monomers. The copolymer may be either a random copolymer or a block copolymer. Furthermore, the polymer obtained by the production method of the present invention may be either a branched or linear polymer, but is preferably a linear polymer in order to take advantage of the high polymerization controllability provided by the organic compound (A).

[0061] The method for mixing the organic compound (A), the radical generator (B), the monomer (Y), and, if necessary, the co-catalyst is not particularly limited, as long as it is a method that can generate dormant species and control the increase in molecular weight of the polymer. Examples of such methods include: adding the organic compound (A), the radical generator (B), and, if necessary, the co-catalyst to the monomer (Y); mixing the organic compound (A), the radical generator (B), and, if necessary, the co-catalyst, and then mixing the resulting mixture with the monomer (Y); mixing the organic compound (A), the radical generator (B), the monomer (Y), and, if necessary, the co-catalyst all at once; and mixing the organic compound (A), the co-catalyst, and the monomer (Y), and then mixing the resulting mixture with the radical generator (B). Alternatively, the organic compound (A), the radical generator (B), the monomer (Y), and the co-catalyst may be mixed in portions. For example, there may be mentioned a method in which the organic compound (A), the radical generator (B), and, if necessary, the co-catalyst, and a portion of the monomer (Y) are mixed to generate dormant species in which the organic compound (A) is covalently bonded to a short-chain polymer terminal, and then the dormant species is mixed with the remainder of the monomer (Y) to increase the molecular weight. Note that the dormant species may be isolated as a macroinitiator and then mixed with the remainder of the monomer (Y) to increase the molecular weight.

[0062] The polymerization temperature is preferably, for example, 0 to 80°C. If the polymerization temperature is below 0°C, the polymerization rate may be insufficient, which may result in a decrease in productivity. From this point of view, the polymerization temperature is more preferably 10°C or higher, and even more preferably 20°C or higher. On the other hand, if the polymerization temperature exceeds 80°C, the controllability of the radical polymerization may decrease. From this point of view, the polymerization temperature is more preferably 70°C or lower, and even more preferably 65°C or lower.

[0063] From the viewpoint of further improving polymerization controllability, when the conversion rate of the monomer (Y) is 5.0% by mass, the ratio (Mn / theoretical Mn) of the number average molecular weight (Mn) (measured value) to the theoretical number average molecular weight (theoretical Mn) of the polymer is preferably 10.0 or less, more preferably 8.0 or less, even more preferably 6.0 or less, even more preferably 5.0 or less, particularly preferably 4.0 or less, and most preferably 3.0 or less. On the other hand, from the viewpoint of productivity, when the conversion rate of the monomer (Y) is 5.0% by mass, the ratio (Mn / theoretical Mn) of the polymer is preferably 0.5 or more, more preferably 0.8 or more. The conversion rate of the monomer (Y) at the end of polymerization is not particularly limited and may be adjusted depending on the amounts of the organic compound (A) and the monomer (Y) added, the target number average molecular weight, etc., but is typically 3 to 50% by mass. The conversion rate is preferably 10% by mass or more, more preferably 20% by mass or more. The number average molecular weight (Mn) (measured value) of the polymer when the conversion rate is 5.0% by mass is determined as follows. GPC (gel permeation chromatography) measurement of the polymer is performed multiple times from the start of polymerization to the end of polymerization to determine the number average molecular weight (Mn) at multiple conversion rates. The number average molecular weight (Mn) is then plotted against the conversion rate, and the number average molecular weight (Mn) of the polymer when the conversion rate is 5.0% by mass is determined from a straight line passing through the point closest to 5.0% by mass where the conversion rate is 1.0% by mass or more and less than 5.0% by mass, and the point closest to 5.0% by mass where the conversion rate is more than 5.0% and 15% by mass or less. However, if the number average molecular weight (Mn) of the polymer when the conversion rate is 5.0% by mass is measured directly, the measured value is used as the number average molecular weight (Mn) of the polymer when the conversion rate is 5.0% by mass. Specifically, the method described in the Examples below is adopted. The theoretical number average molecular weight (theoretical Mn) of the polymer is determined by the following formula: Theoretical Mn = molar ratio of monomer (Y) to organic compound (A) (Y / A) × average molecular weight of monomer (Y) [g / mol] × (conversion rate [mass%] / 100)

[0064] In order to take advantage of the high polymerization controllability of the production method of the present invention, it is preferable to produce a block copolymer in the polymerization step. Specifically, in the polymerization step, it is preferable to sequentially carry out controlled polymerization of a monomer (Ya) and a monomer (Yb) other than the monomer (Ya) in the presence of an organic compound (A), a radical generator (B), and, if necessary, the co-catalyst, thereby obtaining a block copolymer containing a polymer block (a) containing a monomer (Ya) unit and a polymer block (b) containing a monomer (Yb) unit. It is more preferable to sequentially carry out controlled polymerization of a monomer (Ya) and a monomer (Ya) and a monomer (Yb) in the presence of an organic compound (A), a radical generator (B), and, if necessary, the co-catalyst, thereby obtaining a block copolymer containing a polymer block (a) containing a monomer (Ya) unit and a polymer block (ab) containing a monomer (Ya) unit and a monomer (Yb) unit. The polymerization step will be described below.

[0065] In the polymerization step, first, the monomer (Ya), if necessary, another monomer (Yc) other than the monomer (Ya) and the monomer (Yb), the organic compound (A), the radical generator (B), and, if necessary, the co-catalyst are mixed by the method described above to initiate polymerization of the monomer (Ya). Then, after the number average molecular weight of the polymer block (a) containing the monomer (Ya) reaches a target value, the monomer (Yb) is polymerized to synthesize the polymer block (b) containing the monomer (Yb) unit. At this time, the remaining monomer (Ya) may be removed, and then the monomer (Yb) is added to the reaction solution to polymerize the monomer (Yb), thereby synthesizing the polymer block (b) containing the monomer (Yb) unit. Alternatively, the monomer (Yb) may be added to the reaction solution without removing the monomer (Ya), and the remaining monomer (Ya) may be copolymerized with the monomer (Yb) to synthesize a copolymer block (ab) containing a monomer (Ya) unit and a monomer (Yb) unit. When the monomer (Yb) is added, an additional monomer (Ya) or another monomer (Yc) may be added as necessary.

[0066] Alternatively, polymer block (ab) may be synthesized by first mixing monomer (Ya), monomer (Yb), if necessary, another monomer (Yc), organic compound (A), radical generator (B), and if necessary, the co-catalyst, and after monomer (Yb) is completely consumed or the remaining monomer (Yb) is removed, polymerizing monomer (Ya) to synthesize polymer block (a).

[0067] In this way, a diblock copolymer may be obtained by synthesizing the polymer block (a) and the polymer block (b) or the copolymer block (ab), or a ternary or higher multiblock copolymer may be obtained by repeatedly polymerizing the monomer (Ya), the monomer (Yb), or another monomer (Yc). From the viewpoint of cost, the block copolymer is preferably a diblock copolymer, a triblock copolymer, or a tetrablock copolymer, more preferably a diblock copolymer or a triblock copolymer, and even more preferably a diblock copolymer. The bonding form of each block is preferably linear.

[0068] In order to easily obtain the performance derived from each block, the ratio of the number average molecular weight (Mn) of each block to the number average molecular weight (Mn) of the block copolymer (Mn of block / Mn of block copolymer) is preferably 0.01 to 0.99. The ratio (Mn of block / Mn of block copolymer) is more preferably 0.05 or more, and even more preferably 0.1 or more. On the other hand, the ratio (Mn of block / Mn of block copolymer) is more preferably 0.95 or less, and even more preferably 0.9 or less.

[0069] The content of the monomer (Ya) unit in the polymer block (a) is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, and particularly preferably 90 mol% or more. The content of the monomer (Yb) unit in the polymer block (a) is preferably less than 10 mol%, more preferably less than 5 mol%, and even more preferably less than 1 mol%. The content of the monomer (Yb) unit in the polymer block (b) is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, and particularly preferably 90 mol% or more. The content of the monomer (Ya) unit in the polymer block (b) is preferably less than 10 mol%, more preferably less than 5 mol%, and even more preferably less than 1 mol%. The content of the monomer (Ya) unit in the polymer block (ab) is preferably 1 to 99 mol%, more preferably 5 to 99 mol%, and even more preferably 10 to 90 mol%. The content of the monomer (Yb) unit in the polymer block (ab) is preferably from 1 to 99 mol %, more preferably from 5 to 99 mol %, and even more preferably from 10 to 90 mol %.

[0070] The monomer (Ya), the monomer (Yb), and the other monomer (Yc) are not particularly limited, and the monomers described above as the monomer (Y) can be used in appropriate combination. Among these, it is preferable to use the vinyl ester or N-vinyl amide monomer as one of the monomers (Ya) and (Yb). The other monomer used together with the vinyl ester is not particularly limited as long as it is a monomer other than a vinyl ester, but is preferably the acrylic ester, the olefin, or the acrylic acid. The other monomer used together with the N-vinyl amide monomer is not particularly limited as long as it is a monomer other than a vinyl ester, but is preferably the acrylic ester, the olefin, or the acrylic acid.

[0071] Among these, it is particularly preferred to obtain a vinyl ester-based block copolymer containing a vinyl ester polymer block and a polymer block containing vinyl ester units and units derived from a monomer other than the vinyl ester by sequentially carrying out controlled radical polymerization of a vinyl ester and controlled radical polymerization of a vinyl ester and a monomer other than the vinyl ester in the presence of an organic compound (A), a radical generator (B), and, if necessary, the co-catalyst in the polymerization step.It is also particularly preferred to obtain an N-vinylamide-based monomer block copolymer containing an N-vinylamide polymer block and a polymer block containing units derived from an N-vinylamide-based monomer and a monomer other than the N-vinylamide-based monomer by sequentially carrying out controlled radical polymerization of an N-vinylamide-based monomer and a monomer other than the N-vinylamide-based monomer in the polymerization step in the presence of an organic compound (A), a radical generator (B), and, if necessary, the co-catalyst.

[0072] In the polymerization step, it is preferable to carry out a termination step in which a polymerization terminator is added to terminate the polymerization reaction when the number average molecular weight of the polymer or the conversion rate of the monomer (Y) reaches a target value. Examples of the polymerization terminator include 1,1-diphenylethylene; hydroxy aromatic compounds such as p-methoxyphenol, hydroquinone, cresol, t-butylcatechol, and p-nitrosophenol; quinone compounds such as benzoquinone and naphthoquinone; conjugated carboxylic acids such as muconic acid and sorbic acid; thioethers such as phenothiazine, distearyl thiodipropionate, and dilauryl thiodipropionate; aromatic amines such as p-phenylenediamine and N-nitrosodiphenylamine; nitroxides such as 2,2,6,6-tetramethylpiperidine 1-oxyl and 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl; and transition metal salts such as copper acetate, copper dithiocarbamate, and manganese acetate. Of these, 1,1-diphenylethylene, sorbic acid and benzoquinone are preferred, and 1,1-diphenylethylene is more preferred.

[0073] The number of moles of the polymerization terminator to be added is preferably 1 to 100 moles per mole of the added organic compound (A). If the number of moles of the polymerization terminator is too small, radicals at the polymer terminals may not be sufficiently captured, and the color tone of the resulting polymer may deteriorate. On the other hand, if the number of moles of the polymerization terminator is too large, the production cost may increase.

[0074] The temperature of the reaction solution in the termination step may be any temperature at which the polymerization terminator can react with the terminal radicals of the polymer, and is preferably 0 to 80° C. The time required for the termination step is usually 1 minute to 5 hours.

[0075] After the polymerization step, a removal step may be carried out to remove the organic compound (A) and the like contained in the obtained polymer, but it is preferable not to carry out such a removal step from the viewpoint of a good balance between environmental aspects, safety, and cost. Since the organic compound (A) is highly safe, the safety of the obtained polymer is high even without carrying out the removal step.

[0076] As described above, it is preferable that the monomer (Y) used in the polymerization step contains a vinyl ester. That is, in the polymerization step, it is preferable to obtain a vinyl ester polymer by controlled radical polymerization of a vinyl ester in the presence of an organic compound (A), a radical generator (B), and, if necessary, the cocatalyst. In this case, a vinyl ester homopolymer may be obtained by using only a vinyl ester as a monomer. Alternatively, it is possible to obtain a random copolymer containing vinyl ester units and units derived from a monomer other than a vinyl ester, or a vinyl ester block copolymer containing a polymer block (a) containing vinyl ester units and a polymer block (b) containing units derived from a monomer other than a vinyl ester, by using a vinyl ester and a monomer other than a vinyl ester as monomers. The vinyl ester polymer thus obtained is suitable for various applications.

[0077] It is also preferable to carry out a saponification step in which the vinyl ester polymer is saponified to convert vinyl ester units into vinyl alcohol units, thereby obtaining a vinyl alcohol polymer.

[0078] In the saponification step, for example, the vinyl ester polymer can be saponified in a state where it is dissolved in alcohol to obtain a vinyl alcohol polymer. When the vinyl ester polymer contains acrylic ester units, the acrylic ester units can be converted to acrylic acid units by adjusting the saponification conditions. In addition, the acrylic ester units or acrylic acid units may form a lactone ring with adjacent vinyl alcohol units.

[0079] Examples of the alcohol used in the saponification reaction include lower alcohols such as methanol and ethanol, with methanol being particularly preferred. The alcohol may be a hydrous alcohol or a dehydrated alcohol. The alcohol used in the saponification reaction may contain a solvent such as acetone, an ester such as methyl acetate or ethyl acetate, or toluene. Examples of catalysts used in the saponification reaction include alkali metal hydroxides such as potassium hydroxide and sodium hydroxide; alkali catalysts such as sodium methylate; and acid catalysts such as mineral acids. The temperature of the saponification reaction is preferably in the range of 20 to 80°C. If a gel-like product precipitates as the saponification reaction proceeds, the product can be pulverized at this point, washed, and dried to obtain a vinyl alcohol polymer.

[0080] The degree of saponification of the vinyl alcohol polymer may be adjusted depending on the application and is not particularly limited, but is usually 50 to 99.99 mol %. In the present invention, the degree of saponification refers to the ratio (mol %) of the total number of moles of vinyl alcohol units (including units derived from vinyl alcohol monomers forming lactone rings) to the total number of moles of vinyl ester units and vinyl alcohol units (including units derived from vinyl alcohol monomers forming lactone rings) in the vinyl alcohol polymer. The degree of saponification of the vinyl alcohol polymer １ It can be determined by H-NMR measurement.

[0081] The total amount of vinyl ester units and vinyl alcohol units in the vinyl alcohol polymer is preferably 50 mol % or more, more preferably 70 mol % or more, and even more preferably 80 mol % or more.

[0082] When the vinyl ester block copolymer containing a polymer block (a) containing vinyl ester units and a polymer block (b) containing units derived from a monomer other than vinyl ester is saponified, a vinyl alcohol block copolymer containing a polymer block (a') containing vinyl alcohol units and a polymer block (b') containing units derived from a monomer other than vinyl ester is obtained. Furthermore, when the vinyl ester block copolymer containing a polymer block (a) containing vinyl ester units and a copolymer block (ab) containing vinyl ester units and units derived from a monomer other than vinyl ester is saponified, a vinyl alcohol block copolymer containing a vinyl alcohol polymer block (a') and a copolymer block (ab') containing vinyl alcohol units and units derived from a monomer other than vinyl ester is obtained.

[0083] The number-average molecular weight (Mn) of the polymer obtained by the production method of the present invention is not particularly limited, but is preferably 1,000 or more. According to the production method of the present invention, it is possible to synthesize a high-molecular-weight polymer while precisely controlling the molecular arrangement, terminal structure, etc. Therefore, this production method is suitably used for producing a polymer with a high number-average molecular weight (Mn). The number-average molecular weight (Mn) of the polymer is more preferably 2,000 or more, even more preferably 4,000 or more, even more preferably 10,000 or more, particularly preferably 20,000 or more, and most preferably 40,000 or more. On the other hand, from the viewpoint of ease of handling, the number-average molecular weight (Mn) of the polymer is preferably 1,000,000 or less, more preferably 500,000 or less, and even more preferably 300,000 or less. The number-average molecular weight (Mn) and molecular weight distribution (Mw / Mn) are values ​​measured by GPC using polymethyl methacrylate as a standard substance. The column may be appropriately selected taking into consideration the solubility of the polymer in the solvent, etc., and a tetrahydrofuran-based column, an HFIP-based column, etc. are preferably used. Specific measurement methods are as described in the Examples.

[0084] The molecular weight distribution (Mw / Mn) of the polymer obtained by the production method of the present invention is not particularly limited, but is preferably 1.00 to 3.5. Polymerization by controlled radical polymerization can produce a polymer with a narrow molecular weight distribution. The molecular weight distribution (Mw / Mn) is more preferably 3.4 or less, even more preferably 3.3 or less, and particularly preferably 3.2 or less.

[0085] In the production method of the present invention, the use of organic compound (A) allows for high-level control of radical polymerization, thereby enabling the production of high-molecular-weight polymers while precisely controlling the molecular arrangement, terminal structure, and the like. Furthermore, when organic compound (A) is used, the polymerization rate is high, resulting in excellent polymer productivity. Therefore, the production method of the present invention not only produces high-performance polymers but also offers cost advantages. Taking advantage of their properties, the resulting polymers are suitable for use in hygiene, daily necessities, construction and civil engineering, industrial, agricultural, medical, and food applications.

[0086] The radical polymerization composition of the present invention comprises an organic compound (A) having a difference in the electronic energy between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of 0.0770 Hartree or more and 0.130 Hartree or less, and a radical generator (B), wherein the molar ratio (B / A) of the radical generator (B) to the organic compound (A) is 0.5 to 20. By using this composition, radical polymerization of a monomer (Y) can be carried out at a high polymerization rate while precisely controlling the molecular arrangement, terminal structure, etc. Furthermore, this radical polymerization composition is highly safe. Therefore, it can be suitably used in the radical polymerization of various monomers, including the above-mentioned polymer production method. It is preferable that the radical polymerization composition further comprises a monomer (Y). In this case, the molar ratio (Y / A) of the monomer (Y) to the organic compound (A) is preferably 300 to 30,000. It is also preferable that the radical polymerization composition further comprises a co-catalyst. The organic compound (A) used in the composition for radical polymerization may be any of those mentioned above as those used as a polymerization inhibitor, and the radical generator (B), monomer (Y) and co-catalyst may be any of those mentioned above as those used in the method for producing a polymer.

[0087] The present invention will be explained in more detail below using examples.

[0088] [Organic Compound (A)] trans,trans-Dibenzylideneacetone trans-Stilbene Cinnamic nitrile Cinnamyl chloride Chalcone Methyl sorbate Sorbic acid Methyl (2E,4E)-5-phenyl-2,4-pentadienoate Tropone Cinnamic alcohol 4-Phenyl-2-butanone

[0089] [Radical generator (B)] ・[2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile)] (V-70) [Monomer (Y)] ・Vinyl acetate (VAc) ・N-vinylpyrrolidone (VP) ・Methyl acrylate (MA) ・2-ethylhexyl acrylate (EHA) [Polymerization inhibitor] ・1,1-diphenylethylene (1,1-DPEt)

[0090] [Number Average Molecular Weight (Mn)] The number average molecular weight (Mn) and molecular weight distribution (Mw / Mn) of the polymer were measured using a gel permeation chromatography (GPC) under any of the following conditions: <Condition 1> Apparatus: GPC manufactured by Shimadzu Corporation Column: Tetrahydrofuran-based column "KF-806M" manufactured by Showa Denko K.K. Standard sample: Polymethyl methacrylate Solvent and mobile phase: Tetrahydrofuran (THF) Flow rate: 1.0 mL / min Temperature: 40°C Sample solution concentration: 0.2% by mass (filtered through a filter with an opening diameter of 0.45 μm) Injection volume: 100 μL Detector: RI <Condition 2> Apparatus: GPC manufactured by Tosoh Corporation Column: Tetrahydrofuran-based column "KF-806M" manufactured by Showa Denko K.K. Standard sample: Polymethyl methacrylate Solvent and mobile phase: N,N-dimethylformamide (DMF) with 10 mM lithium bromide (LiBr) Flow rate: 1.0 mL / min Temperature: 40°C Sample solution concentration: 0.2% by mass (filtered through a filter with an opening diameter of 0.45 μm) Injection volume: 100 μL Detector: RI

[0091] [Theoretical Number Average Molecular Weight (Theoretical Mn)] The theoretical number average molecular weight (theoretical Mn) at a given conversion rate was calculated by the following formula: Theoretical Mn = Molar ratio of monomer (Y) to organic compound (A) (Y / A) × Average molecular weight of monomer (Y) [g / mol] × (Conversion rate [%] / 100)

[0092] [Polymerization controllability] When the conversion rate of the monomer (Y) was 5.0% by mass, the ratio (Mn / theoretical Mn) of the number average molecular weight (Mn) (measured) to the theoretical number average molecular weight (theoretical Mn) of the polymer was 5.0 or less, and when Mn increased with increasing conversion rate, the polymer was judged to have excellent controllability. The number average molecular weight (Mn) (measured) of the polymer when the conversion rate was 5.0% by mass was determined as follows. GPC (gel permeation chromatography) measurement of the polymer in the reaction solution was performed multiple times from the start of polymerization to the end of polymerization, and the number average molecular weight (Mn) at multiple conversion rates was determined. Figure 1 is a graph plotting the number average molecular weight (Mn) against the conversion rate in Example 1. 1, the number average molecular weight (Mn) (horizontal axis, linear scale) was plotted against the conversion (horizontal axis, linear scale), and the number average molecular weight (Mn) of the polymer when the conversion was 5.0% by mass was determined from a straight line passing through the point closest to 5.0% by mass where the conversion was 1.0% by mass or more and less than 5.0% by mass, and the point closest to 5.0% by mass where the conversion was more than 5.0% and 15% by mass or less. When the number average molecular weight (Mn) of the polymer when the conversion was 5.0% by mass was measured directly, the measured value was used as the number average molecular weight (Mn) of the polymer when the conversion was 5.0% by mass.

[0093] [Polymerization Rate] The average polymerization rate (K) (mass% / h) was calculated from the following formula, where I (mass%) is the conversion rate achieved at the time of polymerization termination, and J (h) is the reaction time from the start of polymerization to termination. When (K) is 1.0 mass% / h or more, it was determined that the polymerization rate was high and productivity was excellent. Figure 2 is a graph plotting I (%) against J (h) in Example 1. However, the point of 25 mass% or less was used as the conversion rate achieved at the time of polymerization termination. (K) (% / h) = I (mass%) / J (h)

[0094] [HOMO-LUMO Energy Gap] A conformational search was performed using molecular mechanics method MMFF94S using molecular force field calculation software CONFLEX Version 8 manufactured by Conflex Corporation, and then a structure optimization calculation was performed using quantum chemistry calculation software Gaussian Version 16 manufactured by Gaussian Corporation with unrestricted open-shell density functional theory PBE and basis function 6-31G(d). The electron energy of the highest occupied molecular orbital (HOMO) in the most stable structure was determined as E ＨＯＭＯ [Hartree], the electron energy of the lowest unoccupied molecular orbital (LUMO) is E ＬＵＭＯ When [Hartree] is used, the difference (energy gap) ΔE between the electronic energy of the highest occupied molecular orbital (HOMO) and the electronic energy of the lowest unoccupied molecular orbital (LUMO) is calculated by the following formula: ＨＯＭＯ－ＬＵＭＯ [Hartree] was calculated. ＨＯＭＯ－ＬＵＭＯ = E ＬＵＭＯ -E ＨＯＭＯ

[0095] [Content (U) of Methyl Acrylate Monomer Units in Vinyl Acetate-Based Block Copolymer] The content (U) (mol %) of methyl acrylate monomer units in a vinyl acetate-based block copolymer was determined by the following method. １ H-NMR measurement was carried out. The methine proton (-CH ２ CH (OCOCH ３ The integral value (4.8 ppm) of the peak derived from the methyl acrylate monomer unit (-CH ２ CH (COOCH ３ The integrated value (3.6 ppm) of the peak derived from VAc-T was defined as S, and the content (U) (mol %) of acrylic acid ester monomer units in the vinyl acetate block copolymer was calculated using the following formula. The content (U) and the number average molecular weight (Mn) of each polymer block were used to determine the content of MA units in the copolymer block containing VAc units and MA units: (U) (mol %) = (S / 3) / (S / 3 + T) × 100

[0096] [Content (Z) of 2-ethylhexyl acrylate units in N-vinylamide copolymer] The content (Z) (mol %) of hydrophobic monomer units in the N-vinylamide copolymer was determined by the following method. １ H-NMR measurement was carried out. The methyl proton (-CH ２ CH (COOCH ２ CH (CH ２ C*H ３ ) C ３ H ６ C*H ３ ) and the integral value (0.9 ppm) of the peak derived from the methylene proton (—CH ) adjacent to the nitrogen atom in the heterocycle of the VP monomer unit. ２ CH(-NC*H ２ CH ２ CH ２ The content (Z) (mol %) of EHA units in the N-vinylamide copolymer was calculated using the following formula, where X was the integral value (3.2 ppm) of the peak derived from (CO-)- (methylene proton to the right of the *). The content (Z) of EHA units in the copolymer block containing VP units and EHA units was calculated using the content (Z) and the number average molecular weight (Mn) of each polymer block. (Z) (mol %) = (Y / 6) / ((X / 2) + (Y / 6)) × 100

[0097] Example 1 Polymerization Step To a reactor equipped with a stirrer, a reflux condenser, and a radical generator addition port, 1,000 parts by mass of VAc as the monomer (Y), 0.34 parts by mass of trans,trans-dibenzylideneacetone as the organic compound (A), and 0.45 parts by mass of V-70 as the radical generator (B) were added and dissolved, followed by introduction of nitrogen and inert gas replacement. The reactor was heated and stirred so that the internal temperature reached 45°C. Sampling was performed as appropriate, and the progress of polymerization was confirmed from the solids concentration. When the VAc conversion rate reached 0.6% by mass, the number average molecular weight (Mn) was 19,230, the theoretical number average molecular weight (theoretical Mn) was 4,400, and the ratio (Mn / theoretical Mn) was 4.4. When the VAc conversion rate was 1.2% by mass, the number average molecular weight (Mn) was 26,200, the theoretical number average molecular weight (theoretical Mn) was 8,200, and the ratio (Mn / theoretical Mn) was 3.2. When the VAc conversion rate was 4.0% by mass, the number average molecular weight (Mn) was 56,900, the theoretical number average molecular weight (theoretical Mn) was 27,300, and the ratio (Mn / theoretical Mn) was 2.1. When the VAc conversion rate was 10.4% by mass, the number average molecular weight (Mn) was 141,400, the theoretical number average molecular weight (theoretical Mn) was 71,900, and the ratio (Mn / theoretical Mn) was 2.0. 7.8 hours after the start of heating, when the VAc conversion rate reached 16.0% by mass, 2.6 parts by mass of 1,1-DPEt was added as a polymerization terminator. The number average molecular weight (Mn) at this time was 168,900, the theoretical number average molecular weight (theoretical Mn) was 110,200, the ratio (Mn / theoretical Mn) was 1.5, and the molecular weight distribution (Mw / Mn) was 2.77. Unreacted VAc was distilled off from the solution under reduced pressure to recover polyvinyl acetate, which was then dried in a vacuum dryer at 40°C for 24 hours to obtain polyvinyl acetate. Details of the above polymerization process are shown in Table 1. Figure 1 is a graph plotting the number average molecular weight (Mn) against the VAc conversion. The ratio (Mn / theoretical Mn) of the number average molecular weight (Mn) (measured) to the theoretical number average molecular weight (theoretical Mn) of the polymer at a VAc conversion of 5.0% by mass was found to be 2.0, as determined from Figure 1. Figure 2 is a graph plotting the VAc conversion against the reaction time. The average polymerization rate until a VAc conversion of 16.0% by mass was reached was 2.0% by mass / h. E of organic compound (A) ＨＯＭＯ is -0.1883Hartree, EＬＵＭＯ is -0.1072 Hartree, and ΔE ＨＯＭＯ－ＬＵＭＯ The polymerization reaction was carried out in the same manner as in Example 1, except that 0.26 parts by mass of trans-stilbene was added as the organic compound (A), to obtain polyvinyl acetate. Details are shown in Table 1.

[0098] [Example 3] <Polymerization step> A polymerization reaction was carried out in the same manner as in Example 1, except that 0.19 parts by mass of cinnamic nitrile was added as the organic compound (A), to obtain polyvinyl acetate. Details are shown in Table 1.

[0099] [Example 4] <Polymerization step> A polymerization reaction was carried out in the same manner as in Example 1, except that 0.22 parts by mass of cinnamyl chloride was added as the organic compound (A), to obtain polyvinyl acetate. Details are shown in Table 1.

[0100] [Example 5] <Polymerization Step> A polymerization reaction was carried out in the same manner as in Example 1, except that 0.30 parts by mass of chalcone was added as the organic compound (A), to obtain polyvinyl acetate. Details are shown in Table 1.

[0101] [Example 6] <Polymerization Step> A polymerization reaction was carried out in the same manner as in Example 1, except that 0.18 parts by mass of methyl sorbate was added as the organic compound (A), to obtain polyvinyl acetate. Details are shown in Table 2.

[0102] [Example 7] <Polymerization step> A polymerization reaction was carried out in the same manner as in Example 1, except that 0.16 parts by mass of sorbic acid was added as the organic compound (A), to obtain polyvinyl acetate. Details are shown in Table 2.

[0103] <Saponification Step> Next, the concentration of the methanol solution was adjusted to 4,900 parts by weight of methanol per 100 parts by weight of polyvinyl acetate obtained in the polymerization step in the same reactor as above, and the water bath was heated and stirred until the internal temperature reached 40°C. 88 parts by weight of a methanol solution of sodium hydroxide (concentration 10.6% by weight, 9.3 parts by weight of sodium hydroxide) was added. The thus-prepared methanol solution containing polyvinyl acetate at a concentration of 2% by weight was subjected to a saponification reaction at 65°C for 1 hour. After dewatering, phenolphthalein solution was added to the washing liquid (methanol), and the mixture was washed with methanol until no alkaline reaction was observed, thereby removing the sodium hydroxide and sodium acetate. The solid obtained by centrifugal dehydration was dried in a vacuum dryer at 40°C for 24 hours to obtain white polyvinyl alcohol. The degree of saponification was 99.8%.

[0104] Comparative Example 1 Polymerization Step A polymerization reaction was carried out in the same manner as in Example 1, except that 0.15 parts by mass of tropone was added instead of the organic compound (A), to obtain polyvinyl acetate. Details are shown in Table 2.

[0105] [Comparative Example 2] <Polymerization Step> A polymerization reaction was carried out in the same manner as in Example 1, except that 0.22 parts by mass of cinnamic alcohol was added instead of the organic compound (A), and the reactor was heated and stirred so that the internal temperature reached 60°C, to obtain polyvinyl acetate. Details are shown in Table 2.

[0106] Comparative Example 3 Polymerization Step A polymerization reaction was carried out in the same manner as in Example 1, except that 0.22 parts by mass of 4-phenyl-2-butanone was added instead of the organic compound (A), and the contents were heated and stirred so that the internal temperature of the reactor reached 60° C. Details are shown in Table 2, to obtain polyvinyl acetate.

[0107] Example 8 Polymerization Step A polymerization reaction was carried out in the same manner as in Example 1, except that 0.16 parts by mass of sorbic acid was added as the organic compound (A), 1,000 parts by mass of VP as the monomer (Y), and 0.35 parts by mass of V-70 as the radical generator (B) were added, and the resulting solution was added dropwise to hexane to remove unreacted VP by reprecipitation, thereby recovering polyvinylpyrrolidone, which was then dried in a vacuum dryer at 40°C for 24 hours to obtain polyvinylpyrrolidone. Details are shown in Table 3.

[0108] Example 9 Polymerization Step To a reactor equipped with a stirrer, a reflux condenser, and a radical generator addition port, 1,000 parts by mass of VAc as the monomer (Y), 0.16 parts by mass of sorbic acid as the organic compound (A), and 0.45 parts by mass of V-70 as the radical generator (B) were added and dissolved, followed by introduction of nitrogen and inert gas replacement. The reactor was heated and stirred to an internal temperature of 45°C. Sampling was performed as appropriate, and the progress of polymerization was confirmed from the solids concentration. When the VAc conversion rate reached 7.2% by mass, 15.0 parts by mass of MA were added. The number average molecular weight (Mn) of the polymer at a conversion rate of 7.2% by mass was 83,000. The calculated molar ratio (Y / A) was 8120 / 1. Heating and stirring was then continued, and the progress of polymerization was confirmed from the solids concentration. The sampled polymer was subjected to GPC measurement and １ H-NMR measurement was performed, and when the total conversion of VAc and MA reached 20.6% by mass, 2.6 parts by mass of 1,1-DPEt was added as a polymerization terminator. The number average molecular weight (Mn) at this time was 141,000. Unreacted VAc was distilled off from the solution under reduced pressure to recover a vinyl acetate block copolymer, which was then dried in a vacuum dryer at 40°C for 24 hours to obtain a vinyl acetate block copolymer. Details of the above polymerization process are shown in Table 1. The content of MA units in the resulting vinyl acetate block copolymer was 8.5 mol%, and the content of MA units in the copolymer block containing VAc units and MA units was 13.1 mol%.

[0109] <Saponification Step> Next, a saponification reaction was carried out in the same manner as in Example 7 to obtain a white vinyl alcohol-based block copolymer. The details are shown in Table 3.

[0110] Example 10 Polymerization Step To a reactor equipped with a stirrer, a reflux condenser, and a radical generator addition port, 1000 parts by mass of VP as the monomer (Y), 0.16 parts by mass of sorbic acid as the organic compound (A), and 0.35 parts by mass of V-70 as the radical generator (B) were added and dissolved, followed by introduction of nitrogen and inert gas replacement. The reactor was heated and stirred to an internal temperature of 45°C. Sampling was performed as appropriate, and the progress of polymerization was confirmed from the solids concentration. When the VP conversion rate reached 12.7% by mass, 14.5 parts by mass of EHA were added. The number average molecular weight (Mn) of the polymer at a conversion rate of 12.7% by mass was 110.800. The calculated molar ratio (Y / A) was 8070 / 1. Heating and stirring was then performed, and the progress of polymerization was confirmed from the solids concentration. The sampled polymer was subjected to GPC measurement and １ H-NMR measurement was performed, and when the total conversion of VP and EHA reached 22.0% by mass, 2.0 parts by mass of 1,1-DPEt was added as a polymerization terminator. The number average molecular weight (Mn) at this time was 121,100. The solution was added dropwise to hexane to remove unreacted VP by reprecipitation, and the N-vinylamide copolymer was recovered and dried in a vacuum dryer at 40°C for 24 hours to obtain an N-vinylamide copolymer. Details of the above polymerization process are shown in Table 1. The content of EHA units in the resulting N-vinylamide copolymer was 4.3 mol%, and the content of EHA units in the copolymer block containing VP units and EHA units was 16.9 mol%. Details are shown in Table 3.

[0111] [Example 11] <Polymerization Step> A polymerization reaction was carried out in the same manner as in Example 1, except that 0.27 parts by mass of methyl (2E,4E)-5-phenyl-2,4-pentadienoate was added as the organic compound (A), to obtain polyvinyl acetate. Details are shown in Table 3.

[0112]

[0113]

[0114]

[0115] In Examples 1 to 11, ΔE ＨＯＭＯ－ＬＵＭＯwas 0.0770 Hartree or more and 0.130 Hartree or less, the ratio (Mn / theoretical Mn) at the initial stage of polymerization was 5.0 or less, Mn increased with an increase in conversion, and the average polymerization rate was 1.0% / h or more, confirming that polymerization proceeded in a controlled manner at a polymerization rate with excellent productivity.

[0116] In Comparative Example 1, ΔE ＨＯＭＯ－ＬＵＭＯ Since the average polymerization rate was less than 1.0% / h because it was smaller than 0.0770, it was confirmed that the polymerization rate was low and productivity was poor.

[0117] In Comparative Examples 2 and 3, ΔE ＨＯＭＯ－ＬＵＭＯ is larger than 0.130, the value of Mn / theoretical Mn at a conversion rate of 5.0% exceeds 5.0, which confirms poor polymerization controllability.

Claims

1. A radical polymerization inhibitor comprising an organic compound (A) in which the difference in electronic energy between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) is 0.0770 Hartree or more and 0.130 Hartree or less.

2. The radical polymerization inhibitor according to claim 1, wherein the organic compound (A) is represented by the following formula (I): [In formula (I), R １ , R ２ are each independently an aryl group, an alkyl group, a halogen atom, a cyano group, a hydroxyl group, an amino group, a nitro group, a thiol group, or a group represented by the following formula (II), and R １ and R ２ may be linked to each other to form a ring. ３ , R ４ are each independently a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an alkenyl group, an alkoxy group, an amino group, a nitro group, a cyano group, an acetyl group, or a hydroxyl group, and n is 1 or more and 5 or less. [In formula (II), X represents a heteroatom, a hydroxyl group, an amino group, a nitro group, a thiol group, or an NR ６ or a cyano group, and R ５ is a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an alkenyl group, an alkoxy group, an amino group, a nitro group, a cyano group, an acetyl group, or a hydroxyl group, and R ６ represents an alkyl group having 1 to 5 carbon atoms, a double line consisting of a solid line and a dashed line represents a single bond or a double bond, and * represents a bond.] 3. R １ is an aryl group, and R ２ The radical polymerization inhibitor according to claim 2, wherein is a group represented by the above formula (II), a halogen atom, a cyano group, a hydroxyl group, an amino group, a nitro group, or a thiol group.

4. R ２ is represented by the above formula (II), and R ５ The radical polymerization inhibitor according to claim 3 , wherein is an aryl group or an alkenyl group.

5. R １ is an alkyl group, and R ２ The radical polymerization inhibitor according to claim 2, wherein is a group represented by the above formula (II), a halogen atom, a cyano group, a hydroxyl group, an amino group, a nitro group, or a thiol group.

6. R ２ is represented by the above formula (II), and R ５ The radical polymerization inhibitor according to claim 5 , wherein is an alkoxy group or a hydroxyl group.

7. The radical polymerization inhibitor according to claim 2, wherein X is an oxygen atom.

8. R １ is an aryl group, and R ２ is an aryl group, a cyano group, or is represented by the above formula (II), X is a halogen atom, and R ５ The radical polymerization inhibitor according to claim 2, wherein is a hydrogen atom.

9. R ３ and R ４ The radical polymerization inhibitor according to claim 2, wherein is a hydrogen atom.

10. A composition for radical polymerization, comprising an organic compound (A) having a difference in electronic energy between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of 0.0770 Hartree or more and 0.130 Hartree or less, and a radical generator (B), wherein the molar ratio (B / A) of the radical generator (B) to the organic compound (A) is 0.5 to 20.

11. The composition for radical polymerization according to claim 10, further comprising a monomer (Y), wherein the molar ratio (Y / A) of the monomer (Y) to the organic compound (A) is 300 to 30,000.

12. A method for producing a polymer, comprising a polymerization step of obtaining a polymer by performing controlled radical polymerization of a monomer (Y) in the presence of an organic compound (A) and a radical generator (B), the difference in electronic energy between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) being 0.0770 Hartree or more and 0.130 Hartree or less.

13. The method of claim 12, wherein the monomer (Y) comprises an olefin, a vinyl ester, an acrylic acid, an acrylic acid ester, an acrylamide-based monomer, a styrene-based monomer, an N-vinylamide-based monomer, or a dicarboxylic acid-based monomer.

14. The method for producing a polymer according to claim 13, wherein the monomer (Y) comprises a vinyl ester or N-vinyl amide monomer.

15. A method for producing a polymer according to claim 14, comprising a polymerization step of sequentially carrying out controlled radical polymerization of a vinyl ester and controlled radical polymerization of a vinyl ester and a monomer other than a vinyl ester in the presence of an organic compound (A) and a radical generator (B) to obtain a vinyl ester-based block copolymer.

16. A method for producing a polymer according to claim 14, comprising a polymerization step of sequentially carrying out controlled radical polymerization of a vinylamide monomer and controlled radical polymerization of an N-vinylamide monomer and a monomer other than an N-vinylamide monomer in the presence of an organic compound (A) and a radical generator (B) to obtain an N-vinylamide block copolymer.

17. A method for producing a polymer according to claim 14, comprising a polymerization step of obtaining a vinyl ester polymer by controlled radical polymerization of a vinyl ester in the presence of an organic compound (A) and a radical generator (B), and a saponification step of obtaining a vinyl alcohol polymer by saponifying the obtained vinyl ester polymer.

18. The method for producing a polymer according to claim 17, wherein the polymerization step involves controlled radical polymerization of a vinyl ester and a monomer other than a vinyl ester.

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