JP7634832B2 - Vinyl polymer and method for producing same - Google Patents

Description

The present invention relates to a vinyl polymer and a method for producing the same.

Vinyl polymers obtained by polymerizing vinyl monomers are widely used in various applications including moldings and coatings. Various properties such as elastic modulus, mechanical strength, and durability are required for vinyl polymers, and the use of graft copolymers having different components in the main chain and side chains is effective in obtaining properties suitable for the application.
As a raw material for the graft copolymer, a vinyl polymer having a polymerizable terminal double bond is used. The vinyl polymer having a polymerizable terminal double bond is advantageous in that the larger the molecular weight, the more excellent the graft copolymer can be synthesized in terms of elastic modulus, mechanical strength, durability, etc., but there is a problem that the melt viscosity and solution viscosity increase, and the handling property decreases. Here, the introduction of branches into the polymer is effective as a method for decreasing the melt viscosity and solution viscosity. In other words, a vinyl polymer having a polymerizable terminal double bond, a high molecular weight, and a high branching degree is required as a raw material for the graft copolymer.
Vinyl polymers having polymerizable terminal double bonds can be synthesized by various methods. Examples of methods for synthesizing vinyl polymers having polymerizable terminal double bonds include a method of modifying a compound having a double bond at the end of a vinyl polymer, a method of decomposing a vinyl polymer at high temperature, and a method using chain transfer polymerization. Among these, the method using chain transfer polymerization is widely used industrially because the target product can be obtained in one step. Examples of methods using chain transfer polymerization include a method using an addition-fragmentation chain transfer agent (Non-Patent Document 1) and a method using catalytic chain transfer by cobalt (Patent Document 1).

Special Publication No. 2000-506189

Seiya Kobatake, Bunichiro Yamada, "Radical polymerization of a trimer of methyl acrylate as polymerizable α-substituted acrylate", Molecular Chemistry and Physics, September 1997, Vol. 198, No. 9, pp. 2825-2837

Although the presence of a branched structure has been suggested for the vinyl polymer obtained by the manufacturing method described in Patent Document 1 and Non-Patent Document 1, a high molecular weight has not been achieved. Thus, a vinyl polymer having a polymerizable terminal double bond, a high molecular weight, and a high degree of branching has not been achieved until now.

The objective of the present invention is to provide a vinyl polymer having a polymerizable terminal double bond, a high molecular weight, and a high degree of branching, and a method for producing the same.

式（１）中、Ｒ及びＲ^１～Ｒ^ｎは、それぞれ独立に、水素原子、アルキル基、シクロアルキル基、アリール基又は複素環基であり、Ｚは、ハロゲン原子又はラジカル重合開始剤由来の基であり、Ｘ^１～Ｘ^ｎは、それぞれ独立に、水素原子、メチル基又は式（２）で表される構造であり、ｎは、２～１０，０００の自然数である。

式（２）中、Ｒ及びＲ^１～Ｒ^ｎは、それぞれ独立に、水素原子、アルキル基、シクロアルキル基、アリール基又は複素環基であり、Ｚは、ハロゲン原子又はラジカル重合開始剤由来の基であり、Ｘ^１～Ｘ^ｎは、それぞれ独立に、水素原子、メチル基又は式（２）で表される構造である。Ｒ^ｎ及びＸ^ｎにおいて、ｎは、２～１０，０００の自然数である。
式（１）中のＲ及びＲ^１～Ｒ^ｎと式（２）中のＲ及びＲ^１～Ｒ^ｎとは互いに独立しており、式（１）中のＸ^１～Ｘ^ｎと式（２）中のＸ^１～Ｘ^ｎとは互いに独立している。
［２］ 前記Ｍｗが２万以上である、［１］に記載のビニル重合体。
［３］ 前記Ｍｗが５万以上である、［１］又は［２］に記載のビニル重合体。
［４］ 下記式（３）で表される連鎖移動剤（Ａ）と、ビニル単量体（Ｂ）と、重合開始剤（Ｃ）と、を含む重合性組成物を調製する工程（ｉ）と、
前記重合性組成物を重合する工程（ｉｉ）と、
を備える、［１］～［３］のいずれかに記載のビニル重合体の製造方法。

式（３）中、Ｒ’は、水素原子、ハロゲン原子、－ＯＣ（Ｏ）Ｒ”、－ＣＯＮＨ_２、－ＣＮ、－ＣＯＯＲ”又はアリール基であり、Ｙは、－ＳＲ”、ハロゲン原子、－ＳＯ_２Ｒ”、－Ｐ（Ｏ）（ＯＲ”）_２、－ＳｎＲ”_３、－ＳｉＲ”_３又は－ＯＯＲ”である。Ｒ’及びＹにおいて、Ｒ”は、アルキル基、シクロアルキル基、アリール基又は複素環基である。
［５］ 前記工程（ｉｉ）における前記ビニル単量体（Ｂ）の転化率が８５％以上である、［４］に記載のビニル重合体の製造方法。
［６］ 前記重合性組成物において、前記連鎖移動剤（Ａ）の含有量が前記ビニル単量体（Ｂ）の１００ｍｏｌに対して０．１～２０ｍｏｌである、［４］又は［５］に記載のビニル重合体の製造方法。 The present invention has the following configuration.
[1] A vinyl polymer having a structure represented by the following formulas (1) and (2):
In the following formulas (1) and (2), when the ratio of the number of moles of hydrogen atoms to the total number of moles of hydrogen atoms and methyl groups contained in X ¹ to X ⁿ is x, x is 85 mol % or more,
The vinyl polymer has an M/M ratio of 1.5 or more, where M is the absolute weight average molecular weight measured by a light scattering detector and M is the relative weight average molecular weight measured by a differential refractometer using a size exclusion chromatograph as a standard with respect to linear standard poly(methyl methacrylate).

In formula (1), R and R ¹ to R ⁿ each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, or a heterocyclic group; Z represents a halogen atom or a group derived from a radical polymerization initiator; X ¹ to X ⁿ each independently represent a hydrogen atom, a methyl group, or a structure represented by formula (2), and n is a natural number from 2 to 10,000.

In formula (2), R and R ¹ to R ⁿ each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, or a heterocyclic group, Z represents a halogen atom or a group derived from a radical polymerization initiator, and X ¹ to X ⁿ each independently represent a hydrogen atom, a methyl group, or a structure represented by formula (2). In ^{R n} and X ⁿ , n represents a natural number from 2 to 10,000.
R and R ¹ to R ⁿ in formula (1) and R and R ¹ to R ⁿ in formula (2) are independent of each other, and X ¹ to X ⁿ in formula (1) and X ¹ to X ⁿ in formula (2) are independent of each other.
[2] The vinyl polymer according to [1], wherein the Mw is 20,000 or more.
[3] The vinyl polymer according to [1] or [2], wherein the Mw is 50,000 or more.
[4] A step (i) of preparing a polymerizable composition comprising a chain transfer agent (A) represented by the following formula (3), a vinyl monomer (B), and a polymerization initiator (C);
(ii) polymerizing the polymerizable composition;
The method for producing a vinyl polymer according to any one of [1] to [3],

In formula (3), R' is a hydrogen atom, a halogen atom, -OC(O)R", -CONH ₂ , -CN, -COOR" or an aryl group, and Y is -SR", a halogen atom, -SO ₂ R", -P(O)(OR") ₂ , -SnR" ₃ , -SiR" ₃ or -OOR". In R' and Y, R" is an alkyl group, a cycloalkyl group, an aryl group or a heterocyclic group.
[5] The method for producing a vinyl polymer according to [4], wherein the conversion rate of the vinyl monomer (B) in the step (ii) is 85% or more.
[6] The method for producing a vinyl polymer according to [4] or [5], wherein the content of the chain transfer agent (A) in the polymerizable composition is 0.1 to 20 mol per 100 mol of the vinyl monomer (B).

The present invention provides a vinyl polymer having a polymerizable terminal double bond, a high molecular weight, and a high degree of branching, and a method for producing the same.

In the present invention, the numerical range represented by "~" means a numerical range including the numerical values before and after "~" as the lower and upper limits, respectively. In addition, "(meth)acrylic" means acrylic or methacrylic, "(meth)acrylate" means acrylate or methacrylate, and "(meth)acrylo" means acrylo or methacrylo.

[Vinyl polymer]
The vinyl polymer of the present invention has structures represented by the following formulas (1) and (2).

The meanings of the symbols in formula (1) are as follows:
R and R ¹ to R ⁿ are each independently a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, or a heterocyclic group.
Z is a halogen atom or a group derived from a radical polymerization initiator.
X ¹ to X ⁿ each independently represent a hydrogen atom, a methyl group, or a structure represented by formula (2), and at least one of X ¹ to X ⁿ represents a structure represented by formula (2).
In R ⁿ and X ⁿ , n is a natural number from 2 to 10,000.

The meanings of the symbols in formula (2) are as follows:
R and R ¹ to R ⁿ are each independently a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, or a heterocyclic group, Z is a halogen atom or a group derived from a radical polymerization initiator, and X ¹ to X ⁿ are each independently a hydrogen atom, a methyl group, or a structure represented by formula (2). In R ⁿ and X ⁿ , n is a natural number from 2 to 10,000.

R and R ¹ to R ⁿ in formula (1) and R ¹ to R ⁿ in formula (2) are independent of each other, and X ¹ to X ⁿ in formula (1) and X ¹ to X ⁿ in formula (2) are independent of each other.

Since at least one of X ¹ to X ⁿ in formula (1) is a structure represented by formula (2), the vinyl polymer of the present invention has a branched structure.

The vinyl polymer of the present invention has the structures represented by formulas (1) and (2) from the fact that the vinyl polymer of the present invention has peaks with chemical shift values of 5.5 to 5.6 ppm and 6.1 to 6.2 ppm in ¹ H-NMR measurement, and has a peak with a chemical shift value of 38 to 41 ppm in ¹³ C-NMR measurement.
Here, the peaks having chemical shift values of 5.5 to 5.6 ppm and 6.1 to 6.2 ppm in ¹ H-NMR measurement mean that the vinyl polymer of the present invention has a terminal double bond represented by formula (1), and the peaks having chemical shift values of 38 to 41 ppm in ¹³ C-NMR measurement mean that the vinyl polymer of the present invention has a branched structure represented by formula (2).

In the vinyl polymer of the present invention, a terminal double bond is introduced as shown in formula (1). This terminal double bond is polymerizable, and is useful because it allows the easy synthesis of a graft copolymer by copolymerizing it with a vinyl monomer.

The vinyl polymer of the present invention has structural units derived from (meth)acrylic acid or a (meth)acrylate compound, as represented by the formulas (1) and (2).
Examples of the methacrylate compounds include alkyl (meth)acrylates having 1 to 30 carbon atoms, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, glycidyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, ethoxyethoxyethyl (meth)acrylate, polyethylene glycol (meth)acrylate and its alkyl ethers, benzyl (meth)acrylate, phenyl (meth)acrylate, 3-(triethoxysilyl)propyl (meth)acrylate, and 2-(dimethylamino)ethyl (meth)acrylate and its quaternary alkyl ammonium salts.

The vinyl polymer of the present invention may contain small amounts of other structural units within the range that does not impair the effects of the present invention.
The other structural units are not particularly limited as long as they are structural units derived from monomers capable of radical polymerization.
Examples of the radically polymerizable monomer include styrene-based monomers such as α-methylstyrene, vinyltoluene, and styrene; vinyl ether-based monomers such as methyl vinyl ether, ethyl vinyl ether, and isobutyl vinyl ether; fumaric acid, monoalkyl esters and dialkyl esters of fumaric acid, maleic acid, monoalkyl esters and dialkyl esters of maleic acid, itaconic acid, monoalkyl esters and dialkyl esters of itaconic acid, (meth)acrylonitrile, (meth)acrylamide, butadiene, isoprene, vinyl chloride, vinylidene chloride, vinyl acetate, vinyl ketone, vinylpyridine, and vinylcarbazole.
These radically polymerizable monomers may be used alone or in combination of two or more.

In the vinyl polymer of the present invention, when the ratio of the number of moles of hydrogen atoms to the total number of moles of hydrogen atoms and methyl groups contained in X ¹ to X ⁿ in formulas (1) and (2) is x, x is 85 mol % or more, preferably 90 mol % or more, and more preferably 95 mol % or more.
When x is 85 mol % or more, the vinyl polymer of the present invention has a high degree of branching. Here, x is a value calculated from the charge ratio of acrylic acid and acrylate compound in the vinyl monomer (B) as a raw material.

When the absolute weight average molecular weight of the vinyl polymer of the present invention measured by a light scattering detector is Mwabs and the relative weight average molecular weight based on a linear standard polymethyl methacrylate measured by a differential refractometer using a size exclusion chromatograph is Mw, Mwabs/Mw is 1.5 or more, preferably 2.0 or more. The Mwabs/Mw is an index of the branching degree of the vinyl polymer, and when the vinyl polymer does not have a branched structure, the Mwabs/Mw is 1.0, and when the vinyl polymer has many branched structures, the Mwabs/Mw is greater than 1.0. The higher the branching degree of the vinyl polymer, the greater the Mwabs/Mw.
When the Mwabs/Mw is 1.5 or more, the degree of branching is high, and the melt viscosity and solution viscosity of the vinyl polymer of the present invention are reduced, resulting in excellent handleability.

In the vinyl polymer of the present invention, the Mwabs was determined by the following method.
First, the vinyl polymer is measured using gel permeation chromatography (GPCmax manufactured by Viscotek) and a light scattering detector (TDA302 manufactured by Viscotek) under the following conditions: Then, the absolute molecular weight and intrinsic viscosity at each elution position are calculated using analysis software (OmniSEC) to obtain Mwabs.
Column: One TSKgel guardcolumn HXL-H (6.0 x 40 mm, manufactured by Tosoh Corporation), two TSKgel Multipore HXL (7.8 x 300 mm, manufactured by Tosoh Corporation), and one TSKgel G3000 HXL (7.8 x 300 mm, manufactured by Tosoh Corporation) were connected in series.
Eluent: tetrahydrofuran.
Column and detector temperature: 40°C.
Flow rate: 1.0 mL/min.
Instrument calibration standards: polystyrene (Viscotek, molecular weight 105,000).

In the vinyl polymer of the present invention, the Mw was determined by the following method.
First, size exclusion chromatography (HLC-8220 manufactured by Tosoh Corporation) is used to measure under the following conditions. Then, Mw is calculated using a calibration curve prepared using polymethyl methacrylate manufactured by Polymer Laboratories (four types: Mp (peak molecular weight) = 141,500, 55,600, 11,100, and 1,590).
Column: TSK GUARD COLUMN SUPER H-H (4.6 x 35 mm, manufactured by Tosoh Corporation) and two TSK-GEL SUPER HM-H (6.0 x 150 mm, manufactured by Tosoh Corporation) connected in series.
Eluent: tetrahydrofuran.
Measurement temperature: 40°C.
Flow rate: 0.6 mL/min.

The Mw of the vinyl polymer of the present invention is not particularly limited, but is preferably 20,000 or more, more preferably 50,000 or more, even more preferably 100,000 or more, even more preferably 300,000 or more, and even more preferably 500,000 or more. By using such a vinyl polymer as a raw material, it is possible to obtain molded articles and coating films with excellent elastic modulus and mechanical strength.

[Method of producing vinyl polymer]
The vinyl polymer of the present invention can be produced by a production method including the steps (i) and (ii) described below.

Step (i): A step of preparing a polymerizable composition containing a chain transfer agent (A) represented by the following formula (3), a vinyl monomer (B), and a polymerization initiator (C).

The meanings of the symbols in formula (3) are as follows:
R' is a hydrogen atom, a halogen atom, -OC(O)R'', -CONH ₂ , -CN, -COOR'', or an aryl group.
Y is -SR", a halogen atom, -SO ₂ R", -P(O)(OR") ₂ , -SnR" ₃ , -SiR" ₃ or -OOR".
In R' and Y, R'' is an alkyl group, a cycloalkyl group, an aryl group, or a heterocyclic group.

Step (ii): A step of polymerizing the polymerizable composition.
Each step will be described in detail below.

<Step (i)>
In the step (i), a polymerizable composition is prepared containing the chain transfer agent (A) represented by the formula (3), the vinyl monomer (B), and the polymerization initiator (C). The polymerizable composition may contain a solvent and other additives as necessary.
Each component will be described in detail below.

(Chain Transfer Agent (A))
The chain transfer agent (A) is a compound represented by the above formula (3).
In the formula (3), R' is a hydrogen atom, a halogen atom, -OC(O)R", -CONH ₂ , -CN, -COOR", or an aryl group.

Examples of halogen atoms in R' include fluorine, chlorine, bromine and iodine atoms. The halogen atom is preferably a chlorine or bromine atom. When R' is a halogen atom, an appropriate chain transfer constant is obtained in step (ii).

The aryl group in R′ is, for example, an aryl group having a carbon number of 6 to 18. Examples of the aryl group having a carbon number of 6 to 18 include a phenyl group, a benzyl group, and a naphthyl group.
The aryl group may have a substituent.
Examples of the substituent include an alkyl group, an aryl group, a carboxy group, an alkoxycarbonyl group, a carbamoyl group, a cyano group, a hydroxy group, an amino group, an amide group, a halogen atom, an allyl group, an epoxy group, an alkoxy group, and a group exhibiting hydrophilicity or ionicity.
Examples of the group exhibiting hydrophilicity or ionicity include alkali salts of a carboxy group, alkali salts of a sulfoxy group, poly(alkylene oxide) groups such as a polyethylene oxide group and a polypropylene oxide group, and cationic substituents such as a quaternary ammonium base.
In addition, in the formula (3), Y is -SR", a halogen atom, -SO ₂ R", -P(O)(OR") ₂ , -SnR" ₃ , -SiR" ₃ or -OOR".

In the formula (3), Y is -SR", a halogen atom, -SO ₂ R", -P(O)(OR") ₂ , -SnR" ₃ , -SiR" ₃ or -OOR".

Examples of halogen atoms in Y include fluorine, chlorine, bromine and iodine atoms. The halogen atom is preferably a chlorine or bromine atom. When Y is a halogen atom, an appropriate chain transfer constant is obtained in step (ii).

In R' and Y, R'' is an alkyl group, a cycloalkyl group, an aryl group, or a heterocyclic group.
Examples of the alkyl group for R" include branched or linear alkyl groups having 1 to 20 carbon atoms. Specific examples of the branched or linear alkyl group having 1 to 20 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, a t-butyl group, an i-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, and an icosyl group.

Examples of the cycloalkyl group in R" include cycloalkyl groups having 3 to 20 carbon atoms. Specific examples of the cycloalkyl group having 3 to 20 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, and adamantyl groups.

The aryl group in R" can be, for example, an aryl group having 6 to 18 carbon atoms. Specific examples of the aryl group having 6 to 18 carbon atoms include a phenyl group, a benzyl group, and a naphthyl group.

The heterocyclic group in R" may be, for example, a heterocyclic group having 5 to 18 carbon atoms and containing an oxygen atom, a nitrogen atom, or a sulfur atom as a heteroatom. Specific examples of the heterocyclic group include a γ-lactone group, an ε-caprolactone group, and a morpholine group.

The alkyl group, cycloalkyl group, aryl group and heterocyclic group in R″ may have a substituent.
Examples of the substituent include an alkyl group, an aryl group, a carboxy group, an alkoxycarbonyl group, a carbamoyl group, a cyano group, a hydroxy group, an amino group, an amide group, a halogen atom, an allyl group, an epoxy group, an alkoxy group, and a group exhibiting hydrophilicity or ionicity.
Examples of the group exhibiting hydrophilicity or ionicity include alkali salts of a carboxy group, alkali salts of a sulfoxy group, poly(alkylene oxide) groups such as a polyethylene oxide group and a polypropylene oxide group, and cationic substituents such as a quaternary ammonium base.

R" is preferably an alkyl group or a cycloalkyl group, more preferably an alkyl group.

(Vinyl Monomer (B))
The vinyl monomer (B) is not particularly limited as long as it is a monomer having a vinyl group, but (meth)acrylic acid or the above-mentioned (meth)acrylate compounds are preferred.
In addition to (meth)acrylic acid and the above-mentioned (meth)acrylate compound, the vinyl polymer of the present invention may contain a small amount of a radically polymerizable monomer within a range that does not impair the effects of the present invention.
Examples of the radically polymerizable monomer include styrene-based monomers such as α-methylstyrene, vinyltoluene, and styrene; vinyl ether-based monomers such as methyl vinyl ether, ethyl vinyl ether, and isobutyl vinyl ether; fumaric acid, monoalkyl esters and dialkyl esters of fumaric acid, maleic acid, monoalkyl esters and dialkyl esters of maleic acid, itaconic acid, monoalkyl esters and dialkyl esters of itaconic acid, (meth)acrylonitrile, (meth)acrylamide, butadiene, isoprene, vinyl chloride, vinylidene chloride, vinyl acetate, vinyl ketone, vinylpyridine, and vinylcarbazole.
These radically polymerizable monomers may be used alone or in combination of two or more.

It is preferable to use the vinyl monomer (B) so that the ratio (mol%) of the total number of moles of acrylic acid and acrylate-based compounds to the total number of moles of vinyl monomer (B) is 85 mol% or more. This results in a vinyl polymer in which x is 85 mol% or more. The ratio (mol%) of the total number of moles of acrylic acid and acrylate-based compounds to the total number of moles of vinyl monomer (B) is more preferably 90 mol% or more, and even more preferably 95 mol% or more.

(Polymerization initiator (C))
The polymerization initiator (C) is not particularly limited, and any conventionally known compound can be used, but a radical polymerization initiator is preferred.
Examples of the radical polymerization initiator include an azo-based radical polymerization initiator and a peroxide-based radical polymerization initiator.

Specific examples of the azo radical polymerization initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile) and 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile).
Specific examples of the peroxide-based radical polymerization initiator include 2,4-dichlorobenzoyl peroxide, t-butyl peroxypivalate, o-methylbenzoyl peroxide, bis-3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, t-butylperoxy-2-ethylhexanoate, cyclohexanone peroxide, benzoyl peroxide, methyl ethyl ketone peroxide, dicumyl peroxide, lauroyl peroxide, diisopropylbenzene hydroperoxide, t-butyl hydroperoxide, and di-t-butyl peroxide.
The radical polymerization initiators may be used alone or in combination of two or more.

(solvent)
The solvent is not particularly limited, and examples thereof include alcohol-based solvents (methanol, ethanol, etc.), aromatic hydrocarbon-based solvents (toluene, ethylbenzene, xylene, anisole, etc.), ketone-based solvents (acetone, methyl isobutyl ketone, methyl ethyl ketone, etc.), and ester-based solvents (butyl acetate, etc.). The solvents may be used alone or in combination of two or more.

(Composition of Polymerizable Composition)
The content of the chain transfer agent (A) in the polymerizable composition is not particularly limited, but is preferably 0.001 to 50 mol per 100 mol of the vinyl monomer (B).
When the content of the chain transfer agent (A) is 0.001 mol or more per 100 mol of the vinyl monomer (B), a branched structure can be appropriately introduced into the resulting vinyl polymer.
When the content of the chain transfer agent (A) is 50 mol or less per 100 mol of the vinyl monomer (B), the properties of the vinyl polymer, such as elastic modulus, mechanical strength and durability, can be sufficiently obtained.
The lower limit of the content of the chain transfer agent (A) is preferably 0.001 mol or more, more preferably 0.01 mol or more, and even more preferably 0.1 mol or more, per 100 mol of the vinyl monomer (B).
The upper limit of the content of the chain transfer agent (A) is preferably 50 mol or less, more preferably 30 mol or less, and further preferably 20 mol or less, per 100 mol of the vinyl monomer (B).
The content of the chain transfer agent (A) is preferably from 0.001 to 50 mol %, more preferably from 0.01 to 30 mol %, and even more preferably from 0.1 to 20 mol %, based on 100 mol of the vinyl monomer (B).

The content of the polymerization initiator (C) in the polymerizable composition is not particularly limited, but is preferably 0.0001 to 20 mol per 100 mol of the vinyl monomer (B).
When the content of the polymerization initiator (C) is within the range of 0.0001 to 20 mol per 100 mol of the vinyl monomer (B), an appropriate polymerization rate can be obtained in the step (ii) described below.
The lower limit of the content of the polymerization initiator (C) is preferably 0.0001 mol or more, more preferably 0.01 mol or more, even more preferably 0.05 mol or more, still more preferably 0.10 mol or more, and even more preferably 0.15 mol or more, relative to 100 mol of the vinyl monomer (B).
The upper limit of the content of the polymerization initiator (C) is preferably 20 mol or less, more preferably 5 mol or less, and further preferably 2 mol or less, per 100 mol of the vinyl monomer (B).
The content of the polymerization initiator (C) is preferably 0.0001 to 20 mol, more preferably 0.01 to 20 mol, even more preferably 0.05 to 20 mol, still more preferably 0.10 to 5 mol, and even more preferably 0.15 to 2 mol, relative to 100 mol of the vinyl monomer (B).

The content of the solvent in the polymerizable composition is not particularly limited, but is preferably 0 to 500 parts by mass per 100 parts by mass of the vinyl monomer (B).
When the content of the solvent is 0 to 500 parts by mass relative to 100 parts by mass of the vinyl monomer (B), an appropriate polymerization rate can be obtained in the step (ii) described below, and the solution viscosity after the production of the vinyl polymer is reduced, resulting in excellent handleability.
The lower limit of the content of the solvent is preferably 0 parts by mass or more, and more preferably 100 parts by mass or more, based on 100 parts by mass of the vinyl monomer (B).
The upper limit of the content of the solvent is preferably 500 parts by mass or less, and more preferably 300 parts by mass or less, per 100 parts by mass of the vinyl monomer (B).

(Other additives)
Examples of other additives include pigments, ultraviolet absorbers, release agents, antifoaming agents, plasticizers, viscosity modifiers, etc. Known compounds can be used as these additives.

<Step (ii)>
In step (ii), the polymerizable composition prepared in step (i) is polymerized.
In step (ii), the radical generated from the polymerization initiator (C) is added to the vinyl monomer (B) to give a propagating radical. When the propagating radical is added to the chain transfer agent (A), a polymer having a structure represented by formula (1) is generated by an addition-fragmentation chain transfer mechanism. Here, when X ¹ in formula (1) is a hydrogen atom, the terminal double bond exhibits copolymerizability with the vinyl monomer (B). Therefore, in the later stage of step (ii), the generated polymer having a structure represented by formula (1) becomes a polymer introduced as a graft chain in the form of formula (2). This results in the vinyl polymer according to the present invention.

The polymerization method for the polymerizable composition is not particularly limited, and for example, a conventionally known polymerization method such as bulk polymerization, solution polymerization, suspension polymerization, or emulsion polymerization can be used.
The polymerization reaction may be carried out in the presence of air, but is preferably carried out in an inert gas atmosphere such as nitrogen or argon from the viewpoint of the efficiency of radical polymerization. Known techniques can be used to carry out the polymerization reaction in an inert gas atmosphere, and examples of such techniques include a technique of blowing an inert gas into the polymerizable composition and a technique of repeatedly freezing, degassing, and melting.
The polymerization temperature is not particularly limited, but is preferably from 0 to 150°C, more preferably from 20 to 120°C, from the viewpoint of polymerization rate.
The polymerization time is not particularly limited, but is preferably 0.5 to 48 hours, and more preferably 4 to 48 hours.

The conversion rate of the vinyl monomer (B) in the step (ii) is preferably 85% or more, more preferably 90% or more, from the viewpoint of improving the molecular weight and the degree of branching of the resulting vinyl polymer.
Here, the conversion rate (%) of the vinyl monomer (B) can be determined from the measured value of ¹ H-NMR measurement using a nuclear magnetic resonance apparatus (Avance, 300 MHz, manufactured by Bruker) and CDCl ₃ as a measurement solvent. Specifically, the conversion rate (%) of the vinyl monomer (B) can be calculated as the ratio of the amount of the produced vinyl polymer to the sum of the amount of the remaining vinyl monomer (B) and the amount of the produced vinyl polymer, using the integrated value of the peak derived from the remaining vinyl monomer (B) and the integrated value of the peak derived from the produced vinyl polymer.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the examples described below, and various modifications are possible without departing from the gist of the present invention.

[Raw materials]
The abbreviations for the raw materials used in the examples and comparative examples are shown below.
Chain transfer agent (A)
MBMA: 2-(bromomethyl)methyl acrylate (Tokyo Chemical Industry Co., Ltd.)
Vinyl monomer (B)
nBA: n-butyl acrylate (Tokyo Chemical Industry Co., Ltd.)
Polymerization initiator (C)
AIBN: 2,2'-azobis(isobutyronitrile) (Tokyo Chemical Industry Co., Ltd.)

[Measurement and evaluation methods]
<Absolute weight average molecular weight (Mwabs)>
The Mwabs of the vinyl polymer was determined as follows.
First, the vinyl polymer was measured under the following conditions using gel permeation chromatography (GPCmax manufactured by Viscotek) and a light scattering detector (TDA302 manufactured by Viscotek). Then, the absolute molecular weight and intrinsic viscosity at each elution position were calculated using the software (OmniSEC) attached to the device, and Mwabs was obtained.
Column: One TSKgel guardcolumn HXL-H (6.0 x 40 mm, manufactured by Tosoh Corporation), two TSKgel Multipore HXL (7.8 x 300 mm, manufactured by Tosoh Corporation), and one TSKgel G3000 HXL (7.8 x 300 mm, manufactured by Tosoh Corporation) were connected in series.
Eluent: tetrahydrofuran.
Column and detector temperature: 40°C.
Flow rate: 1.0 mL/min.
Sample concentration: 2 mg/mL (polymer dissolved in tetrahydrofuran).
Injection volume: 150 μL.
Instrument calibration standards: polystyrene (Viscotek, molecular weight 105,000).

<Relative weight average molecular weight (Mw)>
The Mw of the vinyl polymer was determined as follows.
First, size exclusion chromatography (HLC-8220 manufactured by Tosoh Corporation) was used to measure under the following conditions. Then, Mw was calculated using a calibration curve prepared using polymethyl methacrylate (4 types: Mp (peak molecular weight) = 141,500, 55,600, 11,100, and 1,590) manufactured by Polymer Laboratories.
Column: TSK GUARD COLUMN SUPER H-H (4.6 x 35 mm, manufactured by Tosoh Corporation) and two TSK-GEL SUPER HM-H (6.0 x 150 mm, manufactured by Tosoh Corporation) connected in series.
Eluent: tetrahydrofuran.
Measurement temperature: 40°C.
Flow rate: 0.6 mL/min.

<Monomer Conversion Rate>
The conversion rate (%) of each vinyl monomer was determined from the measured value of ^1H -NMR measurement using a nuclear magnetic resonance apparatus (Bruker, Avance, 300 MHz) and _CDCl3 as the measurement solvent. Specifically, the conversion rate was calculated as the ratio of the amount of the produced vinyl polymer to the sum of the amount of the remaining vinyl monomer and the amount of the produced vinyl polymer, using the integrated value of the peak derived from the remaining vinyl monomer and the integrated value of the peak derived from the produced vinyl polymer.

<Degree of branching>
The value of Mwabs/Mw calculated from the values of Mwabs and Mw obtained as described above was used as an index of the branching degree of the vinyl polymer. A larger Mwabs/Mw indicates a higher branching degree.
Furthermore, the exponent term a obtained by the following method was also used as an index of the branching degree of the vinyl polymer. First, the absolute molecular weight and intrinsic viscosity at each elution position were calculated by the above-mentioned method, and the slope of their logarithmic plot (Mark-Houwink-Sakurada plot) was obtained as the exponent term a, which is an index of branching. The smaller the exponent term a, the higher the branching degree.

[Example 1]
A polymerizable composition was prepared using MBMA as a chain transfer agent (A), nBA as a vinyl monomer (B), AIBN as a polymerization initiator (C), and anisole as a solvent. The polymerizable composition was prepared so that nBA was 4.5 mol/L (100 mol parts), MBMA was 0.45 mol/L (10 mol parts), and AIBN was 9 mmol/L (0.2 mol parts).
The resulting polymerizable composition was then placed in a Pyrex (registered trademark) ampoule, and the ampoule was frozen, degassed, and melted three times to remove dissolved oxygen, and then sealed by heat. The sealed ampoule was then kept at 60° C. for 21 hours, and then cooled with dry ice/methanol to terminate the polymerization. The sealed ampoule was opened, and the remaining vinyl monomer (B) was distilled off under reduced pressure to purify the mixture, thereby obtaining a vinyl polymer. The conversion rate of the vinyl monomer (B) and the evaluation results of the obtained vinyl polymer are shown in Table 1.

[Examples 2 to 5, Comparative Examples 1 to 3]
Polymerizable compositions were prepared in the same manner as in Example 1, except that the amounts of the chain transfer agent (A), the vinyl monomer (B) and the polymerization initiator (C) used were changed as shown in Table 1.
Next, a vinyl polymer was obtained in the same manner as in Example 1, except that the polymerization time was changed as shown in Table 1. The conversion rate of the vinyl monomer (B) and the evaluation results of the obtained vinyl polymer are shown in Table 1.

As shown in Table 1, in Examples 1 to 5, vinyl polymers having the specified structure and physical properties were obtained. When applied to molded bodies or coatings, these vinyl polymers are industrially useful because they combine excellent elastic modulus and mechanical strength due to their high molecular weight with excellent handleability such as low melt viscosity and solution viscosity due to their high branching degree. On the other hand, in Comparative Examples 1 to 3, Mw or Mwabs/Mw do not meet the regulations, and are therefore not industrially preferable.

When applied to molded articles or coatings, the vinyl polymer of the present invention has excellent elastic modulus and mechanical strength due to its high molecular weight, and low melt viscosity and solution viscosity due to its high branching degree, so it is easy to handle and is industrially useful.

Claims (6)

A vinyl polymer having a structure represented by the following formulas (1) and (2):
In the following formulas (1) and (2), when the ratio of the number of moles of hydrogen atoms to the total number of moles of hydrogen atoms and methyl groups contained in X ¹ to X ⁿ is x, x is 85 mol % or more,
The vinyl polymer has an M/M ratio of 1.5 or more, where M is the absolute weight average molecular weight measured by a light scattering detector and M is the relative weight average molecular weight measured by a differential refractometer using a size exclusion chromatograph as a standard with respect to linear standard poly(methyl methacrylate).

In formula (1), R and R ¹ to R ⁿ are each independently a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, or a heterocyclic group, Z is a halogen atom or a group derived from a radical polymerization initiator, and X ¹ to X ⁿ are each independently a hydrogen atom, a methyl group, or a structure represented by formula (2), at least one of X ¹ to X ⁿ being a structure represented by formula (2), and n is a natural number from 2 to 10,000.

In formula (2), R and R ¹ to R ⁿ each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, or a heterocyclic group, Z represents a halogen atom or a group derived from a radical polymerization initiator, and X ¹ to X ⁿ each independently represent a hydrogen atom, a methyl group, or a structure represented by formula (2). In ^{R n} and X ⁿ , n represents a natural number from 2 to 10,000.
R and R ¹ to R ⁿ in formula (1) and R ¹ to R ⁿ in formula (2) are independent of each other, and X ¹ to X ⁿ in formula (1) and X ¹ to X ⁿ in formula (2) are independent of each other. The vinyl polymer according to claim 1, wherein the Mw is 20,000 or more. The vinyl polymer according to claim 1 or 2, wherein the Mw is 50,000 or more. A step (i) of preparing a polymerizable composition comprising a chain transfer agent (A) represented by the following formula (3), a vinyl monomer (B), and a polymerization initiator (C);
(ii) polymerizing the polymerizable composition;
The method for producing a vinyl polymer according to any one of claims 1 to 3, comprising:

In formula (3), R' is a hydrogen atom, a halogen atom, -OC(O)R", -CONH ₂ , -CN, -COOR" or an aryl group, and Y is -SR", a halogen atom, -SO ₂ R", -P(O)(OR") ₂ , -SnR" ₃ , -SiR" ₃ or -OOR". In R' and Y, R" is an alkyl group, a cycloalkyl group, an aryl group or a heterocyclic group. The method for producing a vinyl polymer according to claim 4, wherein the conversion rate of the vinyl monomer (B) in step (ii) is 85% or more. The method for producing a vinyl polymer according to claim 4 or 5, wherein the content of the chain transfer agent (A) in the polymerizable composition is 0.1 to 20 mol per 100 mol of the vinyl monomer (B).