JP5094578B2 - Method for producing graft polymer - Google Patents

Description

  The present invention relates to a method for producing a graft polymer, a graft polymer obtained by the method, and an aqueous pigment dispersion containing the graft polymer.

Various production methods are known for the graft polymer, and its application is also diverse. Among them, application as a pigment dispersant has also been found.
A typical method for producing the graft polymer is a macromonomer method.
Patent Document 1 describes a method for producing a graft polymer using a macromonomer prepared by atom transfer radical polymerization (ATRP) which is one of living radical polymerization methods. However, in this production method, the presence of unreacted macromonomer and the molecular weight distribution of the graft polymer are wide, so it cannot be said that a graft polymer having a sufficiently controlled structure is synthesized.
In addition, the graft polymer synthesized by the conventional method produces a water-soluble low-molecular polymer, and when this is used as a pigment dispersant, the surface tension of water is reduced, and the pigment spreads out during application. There's a problem.

JP 2005-510595 A

  An object of the present invention is to provide a method for producing a graft polymer having a precisely controlled chemical structure, a graft polymer obtained by the method, and an aqueous pigment dispersion containing the graft polymer.

The present inventors have found that a graft polymer having a precisely controlled chemical structure can be efficiently obtained by a method having a specific process.
That is, the present invention provides the following [1] to [3].
[1] A method for producing a graft polymer having the following steps (1) to (3).
Step (1): Configuration derived from a functional group-containing monomer (B) capable of reacting with a structural unit derived from a protected carboxylic acid group-containing monomer (A) and a polymerization initiator having a radically transferable atom or atomic group Step of synthesizing a main chain composed of a polymer containing units by an atom transfer radical polymerization method Step (2): Polymerization having a radically transferable atom or atomic group in the main chain obtained in step (1) Step of introducing initiator Step (3): Step of synthesizing a graft polymer containing a structural unit derived from a hydrophobic monomer in the side chain of the main chain obtained in Step (2) by an atom transfer radical polymerization method [2 ] A graft polymer obtained by the method of [1] above.
[3] An aqueous pigment dispersion containing the graft polymer of [2].

According to the production method of the present invention, the main chain and the side chain are synthesized by atom transfer radical polymerization, and since no macromonomer is used, a uniform graft polymer having a sufficiently controlled structure is obtained. be able to.
The graft polymer of the present invention contains a structural unit derived from a carboxylic acid group-containing monomer protected by a main chain, has a narrow molecular weight distribution, and does not contain an unreacted macromonomer. For this reason, when the protective group of carboxylic acid is deprotected and then used as a dispersant for dispersing the pigment in water, the pigment can be sufficiently dispersed without substantially reducing the surface tension of water.

[Method for producing graft polymer]
The manufacturing method of the graft polymer of this invention has the following process (1)-(3), It is characterized by the above-mentioned.
Step (1): Configuration derived from a functional group-containing monomer (B) capable of reacting with a structural unit derived from a protected carboxylic acid group-containing monomer (A) and a polymerization initiator having a radically transferable atom or atomic group Step of synthesizing a main chain composed of a polymer containing units by an atom transfer radical polymerization method Step (2): Polymerization having a radically transferable atom or atomic group in the main chain obtained in step (1) Step of introducing initiator Step (3): Step of synthesizing a graft polymer containing a structural unit derived from a hydrophobic monomer in the side chain of the main chain obtained in step (2) by an atom transfer radical polymerization method

(Atom transfer radical polymerization method (ATRP method))
In this specification, the atom transfer radical polymerization method (ATRP method) is one of living radical polymerization methods and can be represented by the following reaction formula.

Here, P is a polymer or polymerization initiator, X is a halogen atom, A is a low-valent metal complex, and XA is a high-valent complex. First, A withdraws a halogen atom X from the organic halide PX, and XA and a growth radical P. are generated. A monomer is added to this P., and then X is extracted from XA and returns to PX again. By repeating this activated state and inactivated state, a polymer having a narrow molecular weight distribution is generated.
In atom transfer radical polymerization, a metal complex in which at least one transition metal selected from Groups 7 to 11 of the periodic table is a central metal is used as a catalyst, and an organic halide, a sulfonyl halide compound, or a halogen is used as a polymerization initiator. Use contained macroinitiator.

The organic halide or sulfonyl halide compound to be used is not particularly limited as long as it is a compound having at least one halogen serving as a polymerization starting point, but usually one halogen serving as a starting point (polymerization starting terminal) or A compound having two is used.
Specific examples of the polymerization initiator having one halogen as an initiation point include phenylmethyl chloride, phenylmethyl bromide, phenylmethyl iodide and the like; 1-phenylethyl chloride, 1-phenylethyl bromide, 1-phenylethyl iodide 1-phenylisopropyl chloride, 1-phenylisopropyl bromide, 1-phenylisopropyl iodide, etc .; methyl-2-chloropropionate, ethyl-2-chloropropionate, methyl-2-bromopropionate, ethyl -2-bromopropionate, methyl-2-iodopropionate, etc .; methyl-2-chloroisobutyrate, ethyl-2-chloroisobutyrate, methyl-2-bromoisobutyrate, ethyl-2-bromo Isobutyrate, methyl-2-iodine Isobutyrate, ethyl-2-iodoisobutyrate, etc .; α-chloroacetophenone, α-bromoacetophenone, α-chloroacetone, α-bromoacetone, etc .; α-chloroisopropylphenylketone, α-bromoisopropylphenylketone, etc .; p- Toluene sulfonyl chloride, p-toluene sulfonyl bromide, etc. are mentioned.

Specific examples of the polymerization initiator having two halogens as starting points include α, α′-dichloroxylene, α, α′-dibromoxylene, α, α′-diiodylene and the like; bis (1-chloroethyl) Benzene, bis (1-bromoethyl) benzene, etc .; bis (1-chloro-1-methylethyl) benzene, bis (1-bromo-1-ethyl) benzene, etc .; dimethyl 2,5-dichloroadipate, 2,5- Dimethyl dibromoadipate, dimethyl 2,5-diiododipinate, diethyl 2,5-dichloroadipate, diethyl 2,5-dibromoadipate, diethyl 2,5-diiododipinate, 2,6-dichloro-1 , 7-heptanedioic acid dimethyl, 2,6-dibromo-1,7-heptanedioic acid dimethyl, 2,6-diiodo-1,7-heptanedioic acid dimethyl, 2,6-di 1,2-loro-1,7-heptanedioic acid diethyl, 2,6-dibromo-1,7-heptanedioic acid diethyl, 2,6-diiodo-1,7-heptanedioic acid diethyl, etc .; 2,6-dichloro-2, Dimethyl 6-dimethyl-1,7-heptanedioate, dimethyl 2,6-dibromo-2,6-dimethyl-1,7-heptanoate, etc .; 3,5-dichloro-2,6-heptanedione, 3,5 -Dibromo-2,6-heptanedione and the like; 3,5-dichloro-3,5-dimethyl-2,6-heptanedione, 3,5-dibromo-3,5-dimethyl-2,6-heptanedione and the like; Ethylene glycol bis (2-bromoacetic acid) ester, etc .; ethylene glycol bis (2-bromopropionic acid) ester, ethylene glycol bis (2-chloropropionic acid) ester, etc .; (2-bromoisobutyrate) esters, ethylene glycol bis (2-chloroisobutyric acid) esters; alpha, alpha-dichloro-acetophenone, alpha, alpha-dibromo acetophenone, and the like.
These polymerization initiators can be used alone or in combination of two or more.

On the other hand, the halogen-containing macroinitiator is a polymer having at least one halogen terminal that serves as a polymerization initiation point (polymerization initiation terminal). The halogen-containing macroinitiator is usually obtained by a living radical polymerization method using a redox catalyst system by an atom transfer type radical polymerization method or a reverse atom transfer type radical polymerization method.
When the atom transfer type radical polymerization method is used, the radical polymerizable monomer is subjected to living radical polymerization using a halogen-containing radical polymerization initiator as a polymerization initiator and a low-valent metal complex as a catalyst at the start of polymerization. On the other hand, when the reverse atom transfer type radical polymerization method is used, the radical polymerizable monomer is subjected to living radical polymerization using a radical polymerization initiator as a polymerization initiator and a halogen-containing high-valent metal complex as a catalyst at the start of polymerization.

In any of the above polymerization methods, the polymerization initiator is not particularly limited as long as it is a compound having at least one halogen as an initiation point, but is usually a compound having one or two halogens as an initiation point. It is. Theoretically, the number of starting points of the polymerization initiator used for the polymerization of the macroinitiator is the number of starting points per molecule of the macroinitiator that is obtained as it is, but the bimolecular termination reaction, disproportionation reaction, The starting point may be slightly reduced by side reactions such as elimination of halogen. Therefore, macroinitiators having different molecular weight distributions and different numbers of starting points per molecule can be obtained depending on the polymerization conditions and the like.
As a method for producing the macroinitiator, a living radical polymerization method by an atom transfer type radical polymerization method is preferable. The monomer used for the polymerization of the halogen-containing macroinitiator is not particularly limited as long as it is a radical polymerizable monomer, and may be the same as or different from the monomer used for the polymerization in the present invention.

(Process (1))
Step (1) includes a structural unit derived from a protected carboxylic acid group-containing monomer (A) (hereinafter also referred to as “component (A)”), and a polymerization initiator having radically transferable atoms or atomic groups. This is a step of synthesizing a main chain composed of a polymer containing a structural unit derived from a functional group-containing monomer (B) (hereinafter also referred to as “component (B)”) by an atom transfer radical polymerization method.
When introducing a carboxylic acid group into a polymer, it is generally performed by copolymerizing a monomer having a carboxylic acid such as acrylic acid or methacrylic acid. However, in the case of having a free carboxylic acid group, the metal complex which is a polymerization catalyst for the ATRP method described later is deactivated, so that the polymerization cannot be controlled. In the present invention, by performing ATRP using a monomer in which a carboxylic acid group is protected with a detachable group, the polymerization can be controlled because the polymerization proceeds in a living manner, and a polymer having a narrow molecular weight distribution is obtained. Can do.

<(A) component>
Examples of the component (A) used in step (1) include t-butyl (meth) acrylate, n-butyl (meth) acrylate, trimethylsilyl (meth) acrylate, 2-tetrahydropyranyl (meth) acrylate, and the like. From the viewpoint that the deprotection reaction proceeds under mild conditions, 2-tetrahydropyranyl (meth) acrylate is preferred. That is, the protected carboxylic acid group is preferably a 2-tetrahydropyranyloxycarbonyl group.
Moreover, content of the structural unit derived from the component (A) in the main chain obtained in the step (1) is preferably 5 to 50% by mass, more preferably 10 to 45% from the viewpoint of water dispersibility of the pigment. It is 10 mass%, More preferably, it is 10-40 mass%, Most preferably, it is 15-30 mass%.

<(B) component>
Examples of the component (B) used in the step (1) include a monomer having an amino group, a monomer having an epoxy group, a monomer having a hydroxy group, etc., and a monomer having a hydroxy group from the viewpoint of reactivity and polymerization rate. Is preferred.
Examples of the monomer having an amino group include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, 2-vinylpyridine, 4-vinylpyridine and the like.
Examples of the monomer having an epoxy group include glycidyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate glycidyl ether, 3,4-epoxycyclohexylmethyl (meth) acrylate, and the like.

Examples of the monomer having a hydroxy group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-chloro-2-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl ( (Meth) acrylate, diethylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, N-hydroxyethyl acrylamide, etc. are mentioned, and 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate are preferred. -Hydroxyethyl (meth) acrylate is more preferred.
Of the main chain obtained in step (1), the content of the structural unit derived from component (B) is preferably 0.1 to 30% by mass, more preferably 0, from the viewpoint of the adsorptivity of the polymer to the pigment. 0.5 to 20% by mass, more preferably 0.1 to 15% by mass.

<(C) component>
In the step (1), other monomers copolymerizable with these can be used as the component (C) together with the components (A) and (B). Examples of other copolymerizable monomers include methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, and benzyl (meth) acrylate. , 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate, (iso) decyl (meth) acrylate, (iso) dodecyl (meth) acrylate, (iso) stearyl (meth) acrylate (meta) ) Acrylic acid esters; styrene monomers such as styrene, vinyltoluene, 2-methylstyrene and the like.

Furthermore, the monomer represented by following formula (1) is mentioned as (C) component.
^{_{CH 2 = C (R 1)}} COO (R 2 O) p R 3 (1)
Wherein R ¹ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R ² is a divalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero atom, and R ³ is a hetero atom. (The monovalent hydrocarbon group having 1 to 30 carbon atoms which may be present, p is 1 to 30, preferably 2 to 20.)
Specific examples of the monomer represented by the formula (1) include methoxypolyethylene glycol (meth) acrylate, methoxypolytetramethylene glycol (meth) acrylate, ethoxypolyethylene glycol (meth) acrylate, octoxypolyethylene glycol (meth) acrylate, Polyethylene glycol-2-ethylhexyl (meth) acrylate, (iso) propoxypolyethylene glycol (meth) acrylate, butoxypolyethylene glycol (meth) acrylate, methoxypolypropylene glycol (meth) acrylate, methoxy (ethylene glycol / propylene glycol copolymer) (1 -30: Indicates the value of p in formula (1), hereinafter the same, including ethylene glycol: 1-29) (meth) acrylate and the like. It is. In these, octoxy polyethylene glycol (1-30, especially 2-20) (meth) acrylate and polyethyleneglycol (1-30, especially 2-20) -2-ethylhexyl (meth) acrylate are preferable.
In the main chain obtained in the step (1), the content of the structural unit derived from the component (C) is preferably 20 to 95% by mass, more preferably 30 to 85% by mass, from the viewpoint of the viscosity of the pigment aqueous dispersion. %, More preferably 40 to 75% by mass.
In the present invention, the components (A) to (C) can be used alone or in combination of two or more.

<Polymerization initiator>
A preferable polymerization initiator used in the step (1) is an organic halide or a sulfonyl halide compound, and examples thereof include those exemplified above.
Among them, phenylmethyl chloride, phenylmethyl bromide, 1-phenylethyl chloride, 1-phenylethyl bromide; 2-chloropropionitrile; 2-chloropropionic acid, 2-bromopropionic acid, 2-chloroisobutanoic acid, 2 -Alkyl esters such as bromoisobutanoic acid; α, α'-dichloroxylene, α, α'-dibromoxylene, p-halomethylstyrene; 2,5-dibromoadipic acid dialkyl ester, 2,6-dibromo-1,7 -Heptanedioic acid dialkyl esters are preferred. Particularly preferably, 1-phenylethyl chloride, 1-phenylethyl bromide, methyl-2-chloropropionate, ethyl-2-chloropropionate, methyl-2-bromopropionate, ethyl-2-bromo Propionate, methyl-2-chloroisobutyrate, ethyl-2-chloroisobutyrate, methyl-2-bromoisobutyrate, ethyl-2-bromoisobutyrate (EBiB).
Although the usage-amount of a polymerization initiator is not specifically limited, From a viewpoint of controlling superposition | polymerization, it is 0.05-20 mol normally with respect to 100 mol of monomers, Preferably it is 0.1-10 mol, More preferably, it is 0.5-10 mol. .

<Low-valent metal>
In the atom transfer radical polymerization method in the step (1), the low-valent metal of the metal complex that can be used includes Cu ⁺ , Ni ⁰ , Ni ⁺ , Ni ²⁺ , Pd ⁰ , Pd ⁺ , Pt ⁰ , Pt ⁺ , Pt ²⁺ , Rh ⁺ , Rh ²⁺ , Rh ³⁺ , Co ⁺ , Co ²⁺ , Ir ⁰ , Ir ⁺ , Ir ²⁺ , Ir ³⁺ , Fe ²⁺ , Ru ²⁺ , Ru ³⁺ , Ru ⁴⁺ , Ru ⁵⁺ , Os ²⁺ , Os ³⁺ , Re ²⁺ , Re ³⁺ , Re ⁴⁺ , Re ⁶⁺ , Mn ²⁺ and Mn ³⁺ . Among ^{these, Cu +, Ru 2+, Fe} 2+, Ni 2+ is preferable, Cu ⁺ is more preferable.
Examples of the monovalent copper compound include cuprous chloride, cuprous bromide, cuprous iodide, cuprous cyanide, etc. Examples of the divalent nickel compound include nickel dichloride, nickel dibromide, two Examples of divalent iron compounds such as nickel iodide include iron dichloride, iron dibromide, and iron diiodide. Examples of divalent ruthenium compounds include ruthenium dichloride, ruthenium dibromide, and ruthenium diiodide. Is mentioned.
From the viewpoint of obtaining a polymer having a narrow molecular weight distribution, the amount of the valence metal used is preferably 0.01 to 100 mol, more preferably 0.1 to 50 mol, and still more preferably 0.1 to 0.1 mol with respect to 1 mol of the polymerization initiator. 10 mol.

An organic ligand is used for the metal complex of the metal. Organic ligands are used to allow solubilization in polymerization solvents and reversible changes of redox conjugated complexes. Examples of the coordination atom to the metal include a nitrogen atom, an oxygen atom, a phosphorus atom, and a sulfur atom, and a nitrogen atom or a phosphorus atom is preferable.
Specific examples of organic ligands include 2,2′-bipyridyl and derivatives thereof, 1,10-phenanthroline and derivatives thereof, tetramethylethylenediamine, pentamethyldiethylenetriamine, tris (dimethylaminoethyl) amine, triphenylphosphine, and tributyl. A phosphine etc. are mentioned.
In step (1), a high valence complex may be added to the low valence complex for polymerization control.

<Polymerization solvent>
The radical polymerization in step (1) can be performed without solvent or in various solvents.
Examples of the necessary polymerization solvent include ethers such as diethyl ether, tetrahydrofuran, diphenyl ether, anisole and dimethoxybenzene, amides such as N, N-dimethylformamide and N, N-dimethylacetamide, acetonitrile, propionitrile and benzoate. Nitriles such as nitrile, carbonyl compounds such as acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, ethylene carbonate, propylene carbonate, methanol, ethanol, propanol, isopropanol, n-butyl alcohol, t-butyl alcohol, isoamyl alcohol Alcohols such as benzene, toluene and other aromatic hydrocarbons, chlorobenzene, methylene chloride, chloroform, chlorobenzene and other halogens Hydrocarbons. These can be used alone or in admixture of two or more.
Although the usage-amount of a polymerization solvent is not specifically limited, Preferably it is 1-2000 mass parts with respect to 100 mass parts of monomer preparation amounts, More preferably, it is 10-1000 mass parts.

<Manufacture of polymer>
The polymerization temperature in the step (1) is usually -50 to 200 ° C, preferably 0 to 150 ° C. After the polymerization, the remaining monomer and / or solvent can be distilled off, reprecipitation in an appropriate solvent, filtration or centrifugation of the precipitated polymer, washing and drying of the polymer can be performed by known methods.
Examples of the solvent used for reprecipitation include water; C5-C8 alkanes such as pentane, hexane, and heptane; C5-C8 cycloalkanes such as cyclohexane; C1-C6 alcohols such as methanol, ethanol, and isopropanol. Among these, water, hexane, methanol or a mixture thereof is preferable.
The transition metal compound can be removed from the polymerization solution by passing through a column or pad of alumina, silica or clay. In addition, a method in which a metal adsorbent is dispersed in a polymerization solution for treatment can also be employed. If necessary, the metal component may remain in the polymer.
The obtained polymer can be analyzed by size exclusion chromatography, NMR spectrum or the like by a known method.

(Process (2))
Step (2) is a step of introducing a polymerization initiator having a radically transferable atom or atomic group (hereinafter also referred to as “component (D)”) into the main chain obtained in step (1). .
In the present invention, without using a macromonomer, a compound having a site that becomes a polymerization initiation point of atom transfer radical polymerization after main chain synthesis is uniformly introduced into the main chain, and an atom transfer radical polymerization method is started from the polymerization start point. It is important to synthesize the side chain in order to obtain a well-controlled graft polymer having a uniform composition and a narrow molecular weight distribution.

<(D) component>
(D) component has a site | part used as the polymerization starting point of atom transfer radical polymerization, and has a functional group which can react with the functional group derived from (B) component. The functional group capable of reacting with the functional group derived from the component (B) is a carboxy group if the functional group derived from the component (B) is a hydroxy group or an epoxy group, and the functional group derived from the component (B) is an epoxy group. For example, if the functional group derived from an amino group or component (B) is an amino group, an epoxy group may be mentioned, but a carboxy group is preferred from the viewpoint of reactivity.

The component (D) having a carboxy group includes an acid halide obtained by halogenating a carboxy group, but an acid halide is preferable from the viewpoint of reactivity.
Examples of the component (D) having a carboxy group include 2-chloropropionic acid, 2-bromopropionic acid, 2-iodopropionic acid, 2-chlorobutanoic acid, 2-bromobutanoic acid, 2-iodobutanoic acid, and 2-chloroisobutanoic acid. 2-bromoisobutanoic acid, 2-iodoisobutanoic acid, and their acid halides.
It does not specifically limit as (D) component which has an amino group, The compound represented by following General formula (2) is mentioned.

(In the formula, X is a chlorine, bromine or iodine atom, R is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms or an aralkyl group having 7 to 20 carbon atoms, and n is 1 to 20) Indicates an integer.)
In General Formula (2), the alkyl group having 1 to 20 carbon atoms in R may be linear, branched or cyclic, and is preferably an alkyl group having 1 to 10 carbon atoms. Examples of the alkyl group include methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, various pentyl groups, various hexyl groups, various octyl groups, and various decyl groups. Group, cyclopentyl group, cyclohexyl group and the like.
The aryl group having 6 to 20 carbon atoms may have a substituent such as a lower alkyl group on the ring, and is preferably an aryl group having 6 to 15 carbon atoms. Examples of the aryl group include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and a methylnaphthyl group.
The aralkyl group having 7 to 20 carbon atoms may have a substituent such as a lower alkyl group on the ring, and is preferably an aralkyl group having 7 to 15 carbon atoms. Examples of the aralkyl group include a benzyl group, a methylbenzyl group, a phenethyl group, a methylphenethyl group, a naphthylmethyl group, and a methylnaphthylmethyl group.

  It does not specifically limit as (D) component which has the said epoxy group, The compound represented by following General formula (3) is mentioned.

(In the formula, X, R and n are the same as above.)
(D) As usage-amount of a component, it is 0.01-1000 mol normally with respect to 1 mol of reactive functional groups derived from (B) component, Preferably it is 0.01-100 mol, More preferably, it is 0.01-10 mol. .

<Reaction solvent>
The reaction solvent used in the step (2) is not particularly limited. For example, ethers such as diethyl ether, tetrahydrofuran, diphenyl ether, anisole and dimethoxybenzene, amides such as N, N-dimethylformamide and N, N-dimethylacetamide, nitriles such as acetonitrile, propionitrile and benzonitrile, acetone Carbonyl compounds such as methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, ethylene carbonate, propylene carbonate, alcohols such as methanol, ethanol, propanol, isopropanol, n-butyl alcohol, t-butyl alcohol, isoamyl alcohol, benzene, Aromatic hydrocarbons such as toluene, and halogenated hydrocarbons such as chlorobenzene, methylene chloride, chloroform and chlorobenzene. These may be used alone or in combination of two or more.
Although the usage-amount of a reaction solvent is not specifically limited, Preferably it is 0-1000 mass parts with respect to 100 mass parts of polymer preparation amounts, More preferably, it is 50-500 mass parts.

<Production of polymerization initiator-introduced polymer>
The reaction temperature of the functional group derived from the component (B) and the functional group capable of reacting with the functional group derived from the component (B) in the component (D) is not particularly limited, but is usually −50 to 200 ° C., preferably − 20-150 ° C. At that time, if necessary, an appropriate catalyst may be used. After the reaction, it is purified, washed and dried by a known method described in paragraph [0025], and the obtained polymer can be analyzed by a known method.

(Process (3))
Step (3) of the present invention is a step of synthesizing a graft polymer containing a structural unit derived from a hydrophobic monomer in the side chain of the main chain obtained in step (2) by an atom transfer radical polymerization method.
In the present invention, the side chain is synthesized by the atom transfer radical polymerization method using the atom transfer radical polymerization initiation group introduced into the main chain in the step (2) as a polymerization initiation point. By synthesizing not only the main chain but also the side chain by atom transfer radical polymerization, a graft polymer having a uniform composition and a narrow molecular weight distribution can be obtained.
In this step (3), since the polymerization terminal of the main chain has a living property, a hydrophobic polymer chain is also introduced into the main chain terminal.

<Hydrophobic monomer>
Although the hydrophobic monomer used for this invention is not specifically limited, From the viewpoint of the adsorptive ability with respect to a pigment, the hydrophobic monomer whose solubility in 20 degreeC with respect to 100g of water is less than 2g is preferable.
Examples of such hydrophobic monomers include styrene monomers such as styrene, vinyl toluene, and 2-methylstyrene; methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, and butyl (meth) ) Acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate, (iso) decyl (meth) acrylate, (iso) dodecyl (meth) Examples thereof include (meth) acrylic acid esters such as acrylate and (iso) stearyl (meth) acrylate, and fluorine-based monomers such as trifluoroethyl methacrylate. These can be used alone or in admixture of two or more. In these, a styrene-type monomer is preferable and a styrene is more preferable from a viewpoint of making a graft polymer fully contain a pigment.
In the graft polymer, the proportion of the structural unit derived from the hydrophobic monomer is preferably 10 to 60% by mass, more preferably 10 to 50% by mass, and still more preferably from the viewpoint of sufficiently including the pigment in the graft polymer. It is 20-50 mass%.

<Production of graft polymer>
The types and preferred amounts of the low-valent metal, high-valent metal, organic ligand and polymerization solvent that can be used in the step (3) are the same as those in the step (1).
The polymerization temperature in the step (3) is preferably -50 to 200 ° C, more preferably 0 to 150 ° C. After the polymerization, the polymer is purified, washed and dried by a known method described in paragraph [0025], and the obtained polymer can be analyzed by a known method.
The transition metal compound can be removed from the polymerization solution by passing it through a column or pad filled with alumina, silica or clay. In addition, a method in which a metal adsorbent is dispersed in a polymerization solution for treatment can also be employed. If necessary, the metal component may remain in the polymer.

(Process (d))
In the present invention, if necessary, a step of removing a protecting group for the carboxylic acid group in the graft polymer obtained in the step (3) can be performed as the step (d).
The solvent used in the step (d) is not particularly limited, and examples thereof include water, diethyl ether, tetrahydrofuran, diphenyl ether, anisole, dimethoxybenzene and other ethers, N, N-dimethylformamide, N, N-dimethylacetamide and the like. Amides, acetonitrile, propionitrile, nitriles such as benzonitrile, acetone, methyl ethyl ketone, methyl isobutyl ketone, carbonyl compounds such as ethyl acetate, butyl acetate, ethylene carbonate, propylene carbonate, methanol, ethanol, propanol, isopropanol, n -Alcohols such as butyl alcohol, t-butyl alcohol and isoamyl alcohol, aromatic hydrocarbons such as benzene and toluene, chlorobenzene, methylene chloride, chloroform Arm, and chlorobenzene and halogenated hydrocarbons. These solvents can be used alone or in combination of two or more.

Although the reaction temperature at the time of deprotection reaction is not specifically limited, -50-200 degreeC is preferable from a viewpoint of suppressing decomposition | disassembly of a graft polymer, More preferably, it is 0-150 degreeC. At that time, if necessary, an appropriate catalyst may be used. After the reaction, it is purified, washed and dried by a known method described in paragraph [0025], and the obtained polymer can be analyzed by a known method.
In the graft polymer obtained by the step (d), the proportion of the structural unit derived from the carboxylic acid-containing monomer is preferably 3 to 30% by mass, more preferably 5 to 20% by mass, from the viewpoint of dispersing the pigment in water. .

[Graft polymer]
The graft polymer of the present invention is characterized in that a side chain is synthesized from a polymerization initiation point introduced into a main chain after main chain synthesis without using a macromonomer. Furthermore, by synthesizing not only the main chain but also the side chain by the atom transfer radical polymerization method, a graft polymer having a uniform composition and a narrow molecular weight distribution can be obtained.
The number average molecular weight of the graft polymer of the present invention is preferably 3000 to 50000, more preferably 4000 to 40000, and still more preferably 5000 to 30000 from the viewpoint of the viscosity when the graft polymer is dispersed.
The molecular weight distribution index (weight average molecular weight / number average molecular weight) of the graft polymer of the present invention is preferably 2.0 or less, more preferably 1.8 or less, and particularly preferably 1.5 or less.

  The weight average molecular weight, number average molecular weight, and molecular weight distribution index (weight average molecular weight / number average molecular weight) of the graft polymer of the present invention are 60 mmol / L as a solvent using “HLC-8220GPC” manufactured by Tosoh Corporation. Chromatography method using dimethylformaldehyde containing phosphoric acid and 50 mmol / L lithium bromide (column: TSK-GEL α-M × 2, flow rate: 1 mL / min, temperature: 40 ° C., detection: RI, sample concentration : 0.2 mg / mL) using polystyrene as a standard substance.

In the graft polymer of the present invention, the ratio of the side chain consisting of a structural unit derived from a hydrophobic monomer is:
From the viewpoint of sufficiently encapsulating the pigment in the graft polymer, it is preferably 10 to 60% by mass, more preferably 10 to 50% by mass, and still more preferably 20 to 50% by mass.
When the graft polymer of the present invention has a protected carboxylic acid group, the proportion of the structural unit derived from the protected carboxylic acid group-containing monomer (A) is preferably 5 from the viewpoint of water dispersibility of the pigment. -50 mass%, More preferably, it is 10-45 mass%, More preferably, it is 10-40 mass%, Most preferably, it is 15-30 mass%.

[Water-based pigment dispersion]
The aqueous pigment dispersion of the present invention contains the graft polymer of the present invention.
(Pigment)
Examples of the pigment used in the aqueous pigment dispersion of the present invention include inorganic pigments and organic pigments. If necessary, extender pigments can be used in combination.
Examples of the inorganic pigment include carbon black, metal oxide, metal sulfide, and metal chloride. Examples of organic pigments include azo pigments, diazo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, dioxazine pigments, perylene pigments, perinone pigments, thioindigo pigments, anthoraquinone pigments, and quinophthalone pigments.
Among inorganic pigments, carbon black is particularly preferable as the black water-based ink. Examples of carbon black include furnace black, thermal lamp black, acetylene black, and channel black.
Specific examples of preferred organic pigments include C.I. I. Pigment Yellow 13, 17, 74, 83, 97, 109, 110, 120, 128, 139, 151, 154, 155, 174, 180; I. Pigment Red 48, 57: 1,122,146,176,184,185,188,202; I. Pigment violet 19, 23; C.I. I. Pigment Blue 15, 15: 1, 15: 2, 15: 3, 15: 4, 16, 60; I. Pigment green 7, 36, and the like.
Examples of extender pigments include silica, calcium carbonate, and talc.

In the aqueous pigment dispersion of the present invention, the content of the pigment is preferably 1 to 30% by mass and more preferably 3 to 20% by mass from the viewpoint of improving dispersion stability and the like.
The amount ratio of the graft polymer to the pigment is preferably 20 to 1,000 parts by weight, more preferably 50 to 900 parts by weight with respect to 100 parts by weight of the solid content of the graft polymer, from the viewpoint of improving dispersion stability and the like. Preferably, 100-800 mass parts is further more preferable.

(Preparation of aqueous pigment dispersion)
The aqueous pigment dispersion of the present invention is preferably prepared by a method having the following steps (i) and (ii).
Step (i): A step of dispersing a mixture containing the graft polymer of the present invention, an organic solvent, a neutralizing agent, a pigment, water and the like.
Step (ii) is a step of removing the organic solvent from the dispersion obtained in the step (i).

<Process (i)>
(Ii) Step (i) is a step of dispersing the mixture containing the graft polymer of the present invention, an organic solvent, a neutralizing agent, a pigment, water and the like.
In step (i), first, the graft polymer of the present invention is dissolved in an organic solvent, and then a pigment, a neutralizing agent, water, and if necessary, a surfactant and the like are added to the organic solvent and mixed, An oil-in-water dispersion is obtained. In the mixture, the pigment content is preferably 5 to 50% by mass, and the organic solvent content is preferably 10 to 70% by mass. The content of the graft polymer of the present invention is preferably 2 to 40% by mass, and the water content is preferably 10 to 70% by mass. Although there is no particular limitation on the degree of neutralization, it is usually preferable that the finally obtained aqueous pigment dispersion has a neutral liquidity, for example, a pH of 4.5 to 10. The pH can also be determined from the degree of neutralization desired for the graft polymer of the present invention. The graft polymer of the present invention may be previously neutralized with a neutralizing agent.

Preferred examples of the organic solvent include alcohol solvents, ketone solvents, ether solvents, and the like, and those having a solubility in water of 20% by mass or less at 20 ° C. are preferable, and more preferably 10% by mass or more.
Examples of the alcohol solvent include n-butanol, tertiary butanol, isobutanol, diacetone alcohol and the like. Examples of ketone solvents include methyl ethyl ketone, diethyl ketone, and methyl isobutyl ketone. Examples of ether solvents include dibutyl ether and dioxane. Of these solvents, methyl ethyl ketone and methyl isobutyl ketone are preferred. The said solvent may be used individually by 1 type, and 2 or more types may be mixed and used for it.
As the neutralizing agent, an acid or a base can be used according to the type of the salt-forming group in the graft polymer of the present invention, and hydrochloric acid, acetic acid, propionic acid, phosphoric acid, sulfuric acid, lactic acid, succinic acid, glycolic acid Acids such as gluconic acid and glyceric acid, bases such as lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, and triethanolamine can be used.

The method for dispersing the mixture in step (i) is not particularly limited, and the average particle size of the polymer particles can be atomized until the desired particle size is obtained only by the main dispersion. It is preferable to control the average particle size of the water-insoluble polymer particles to a desired particle size by applying a shear stress to perform this dispersion.
When preliminarily dispersing the mixture, a commonly used mixing and stirring device such as an anchor blade can be used. Among the mixing and stirring apparatuses, high-speed stirring and mixing apparatuses such as Ultra Disper [Asada Tekko Co., Ltd., trade name], Ebara Milder [Ebara Manufacturing Co., Ltd., trade name], TK Homomixer [Primix Co., Ltd., trade name] are preferable. .
As means for applying the shear stress of this dispersion, for example, a kneader such as a roll mill, a bead mill, a kneader, an extruder, a high-pressure homogenizer (Izumi Food Machinery Co., Ltd., trade name), a minilab 8.3H type (Rannie Co., trade name) Examples thereof include chamber type high-pressure homogenizers such as homo-valve type high-pressure homogenizers, microfluidizers (trade name), and nanomizers (trade name). Among these, a high-pressure homogenizer is preferable from the viewpoint of reducing the particle size of the pigment contained in the mixture.

<Step (ii)>
Step (ii) is a step of removing the organic solvent from the dispersion obtained in step (i).
In step (ii), an aqueous dispersion of graft polymer particles containing a pigment is obtained by distilling off the organic solvent from the dispersion obtained in step (i) to form an aqueous system. The organic solvent contained in the aqueous dispersion can be removed by a general method such as distillation under reduced pressure. The organic solvent in the aqueous dispersion of the obtained graft polymer particles is substantially removed, and the amount of the organic solvent is 0.1% by mass or less, preferably 0.01% by mass or less.
The aqueous dispersion of the graft polymer particles containing the pigment is obtained by dispersing the solid content of the graft polymer containing the pigment in water as a main solvent.
Here, there is no restriction | limiting in particular in the form of the graft polymer particle containing a pigment, The particle | grains should just be formed with the graft polymer at least. For example, a particle form in which the pigment is encapsulated in the graft polymer, a particle form in which the pigment is uniformly dispersed in the graft polymer, and a particle form in which the pigment is exposed on the particle surface of the graft polymer are included.

The aqueous dispersion of the graft polymer particles containing the pigment can be prepared, for example, by dissolving the graft polymer in an organic solvent, adding the pigment to the resulting solution, pre-kneading, then adding the neutralizing agent and water and kneading. It can also be obtained by producing an oil-in-water dispersion and distilling off the organic solvent from the resulting kneaded product.
As the organic solvent, an alcohol solvent, a ketone solvent and an ether solvent are preferable, and specific examples thereof include those exemplified in the step (i). Of these solvents, isopropanol, acetone and methyl ethyl ketone are preferred.
Further, if necessary, an organic solvent may be used in combination with a high boiling hydrophilic organic solvent. Examples of the high boiling hydrophilic organic solvent include phenoxyethanol, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether and the like.
A base can be used as a neutralizing agent. Examples of the base include tertiary amines such as trimethylamine and triethylamine, ammonia, sodium hydroxide, potassium hydroxide and the like. The degree of neutralization is not particularly limited, but from the viewpoint of the storage stability of the pigment dispersion, it is usually preferable that the aqueous dispersion obtained has a neutral liquidity, for example, a pH of 4.5 to 9.
Moreover, as water used for preparation of the water-system pigment dispersion of this invention, although generally used water can be used, ion-exchange water and distilled water are preferable from a viewpoint of the amount of impurities.

Example 1
(1) Synthesis of random copolymer In a 500 mL eggplant flask with a three-way cock, a stirrer chip, 2.7 g of benzyl methacrylate (BnMA) as a monomer, 0.43 g of 2-hydroxyethyl methacrylate (HEMA), polyethylene glycol (EO = 4) 2-ethylhexyl methacrylate (PEGMA) 3.3 g, 2-tetrahydropyranyl methacrylate (M-THP) 3.6 g, and ethyl-2-bromoisobutyrate (EBiB) 0.094 g as a polymerization initiator were charged for 15 minutes. Argon bubbling was performed.
Next, under an argon atmosphere, 0.024 g of cuprous chloride and 0.0065 g of cupric chloride as catalysts and 4,4′-dinonyl-2,2′-bipyridyl (dNbipy) 0 as a ligand in a sample bottle are used. .24 g and 10 g of anisole as a polymerization solvent were weighed and stirred with a stirrer chip. The anisole solution in which the copper complex was dissolved was added to the eggplant flask, and polymerization was performed at 60 ° C. for 2 hours while stirring with a stirrer chip.
As a result, the polymerization rate measured by ¹ H-NMR was 57%, and the polymerization rates of BnMA, HEMA, and M-THP as measured by gas chromatography were 50%, 62%, and 59%, respectively. After completion of the polymerization, reprecipitation with hexane and vacuum drying were performed to obtain 5 g of a random copolymer. ^{From the 1} H-NMR measurement, it was confirmed that the composition of the obtained polymer was almost as charged. As a result of measurement by gel permeation chromatography calibrated with a polystyrene standard sample, the number average molecular weight was 8000 and the molecular weight distribution index was 1.24.

(2) Synthesis of polymer introduced with polymerization initiator 1.5 g of the random copolymer obtained in (1) above, 0.054 g of triethylamine (TEA), and 4 g of dehydrated tetrahydrofuran (THF) were added to an eggplant flask, and a rubber stopper was used. Capped. While the eggplant flask was ice-cooled, 0.125 g of 2-bromoisobutyric acid bromide (2-Br-BiB) was added dropwise with a syringe. While stirring with a stirrer chip, the reaction was carried out with ice cooling for 3 hours and at room temperature for 10 hours. After completion of the reaction, the produced salt was removed by filtration. The reaction solution was passed through an activated alumina column, reprecipitated with hexane, and then vacuum dried. From the ¹ H-NMR measurement (400 MHz, CDCl ₃ ) of the obtained polymer, it was confirmed that HEMA-derived OH groups in the polymer were almost 100% reacted with 2-Br-BiB.

(3) Production of graft polymer A 500 mL eggplant flask equipped with a three-way cock was charged with 4.7 g of styrene (St) as a stirrer chip and monomer, and 1.0 g of the polymer obtained in (2) above as a polymerization initiator. Argon bubbling was performed for a minute. Next, under an argon atmosphere, 0.033 g of copper bromide as a catalyst, 0.19 g of dNbipy as a ligand, and anisole as a polymerization solvent were weighed in a sample bottle and stirred with a stirrer chip. The anisole solution in which the copper complex was dissolved was added to the eggplant flask, and polymerization was performed at 90 ° C. for 4 hours while stirring with a stirrer chip. ^The polymerization rate measured by ¹ H-NMR was 15%. After completion of the polymerization, reprecipitation with hexane and vacuum drying to obtain a graft polymer (side chain ratio: 38 mass%, protected carboxylic acid group-containing monomer (A) -derived structural unit ratio: 24 mass%). Obtained. As a result of measurement by gel permeation chromatography calibrated with a polystyrene standard sample, the number average molecular weight was 13,200, and the molecular weight distribution index was 1.35.

Example 2
5 g of the graft polymer obtained in Example 1 and 5 g of THF were added to the eggplant flask to dissolve the polymer, and then acetic acid and water were added and sealed with a ball stopper. While stirring with a stirrer chip, the mixture was heated to 45 ° C. and reacted for 3 hours. After completion of the reaction, reprecipitation was performed with hexane. ^{By 1} H-NMR measurement, it was confirmed that the deprotection reaction of the tetrahydropyranyl (THP) group, which is a protecting group of almost 100% carboxylic acid group, proceeded. After completion of the reaction, reprecipitation was performed with hexane. It was dissolved in chloroform and separated with a 2% by mass aqueous ethylenediaminetetraacetic acid (EDTA) solution to remove the copper complex. The chloroform layer was collected, dehydrated by adding sodium sulfate and dried to obtain 3 g of a graft polymer. The number average molecular weight was 13,000 and the molecular weight distribution index was 1.35.

Comparative Example 1
42 g of benzyl methacrylate (BnMA), 35 g of polypropylene glycol monomethacrylate, 8 g of methacrylic acid, styrene macromonomer (trade name: “AS-60”, number average molecular weight 6000, polymerizable functional group: methacryloyloxy group) 15 g, methyl ethyl ketone 40 g, 2-mercaptoethanol 0.5 g, 2,2′-azobis (2,4-dimethylvaleronitrile) (manufactured by Wako Pure Chemical Industries, Ltd., trade name “V-65”) 1 g solution was prepared. Of these, 10% by mass was placed in a reaction vessel equipped with a stirrer, a reflux condenser, a dropping funnel, a thermometer, and a nitrogen inlet tube, and the nitrogen gas was sufficiently replaced. On the other hand, the remaining 90% by mass was put into a dropping funnel and polymerization was carried out while dropping at 75 ° C. with stirring. After about 2 hours at 75 ° C. from the end of the dropwise addition, 0.9 g of “V-65” dissolved in 40 g of methyl ethyl ketone was added, followed by aging at 80 ° C. for 1 hour to drive off unreacted monomers to obtain a polymer solution. Thereafter, 60 g of a dry polymer was obtained according to a conventional method. The obtained graft polymer had a weight average molecular weight of 100,000 and a molecular weight distribution index of 4.0.

Example 3
A predetermined amount of 90 g of methyl ethyl ketone and a neutralizing agent (5 mol / L aqueous sodium hydroxide solution) was added to 77 g of a solution prepared by adjusting the graft polymer obtained in Example 2 to 50% by mass with methyl ethyl ketone to neutralize methacrylic acid (medium (Concentration 75%), ion-exchanged water 370 g, and C.I. I. 90 g of Pigment Yellow 74 was added, mixed with a disper, and further treated with a disperser (Microfluidizer M-140K, 150 MPa) for 20 passes (20 times).
After adding 100 g of ion-exchanged water to the obtained aqueous dispersion and stirring, methyl ethyl ketone was removed at 60 ° C. under reduced pressure, and a part of water was further removed, and then a 5 μm filter (acetylcellulose membrane, outer diameter). : 2.5 cm, manufactured by Fuji Film Co., Ltd.) and filtered with a 25 mL needleless syringe (manufactured by Terumo Co., Ltd.) to remove coarse particles to obtain an aqueous dispersion. 30 g of the obtained water dispersion 10 g of glycerin, 7 g of triethylene glycol monobutyl ether, 1.0 g of “Surfinol 465” (manufactured by Nissin Chemical Industry Co., Ltd.), 0.09 g of Ploxel XL2 (S) (manufactured by Avicia Co., Ltd.) Then, 51.91 g of ion-exchanged water was added to obtain an aqueous pigment dispersion.

Comparative Example 2
An aqueous pigment dispersion was obtained in the same manner as in Example 3, except that the graft polymer obtained in Comparative Example 1 was used instead of the graft polymer obtained in Example 2.

<Evaluation of water-based pigment dispersion>
The surface tension of the aqueous pigment dispersions obtained in Example 3 and Comparative Example 2 was evaluated at 25 ° C. based on the following method.
Using a surface tension meter (trade name “CBVP-2”, manufactured by Kyowa Interface Science Co., Ltd.), a cylindrical polyethylene container (diameter: 3.6 cm × depth: 1.2 cm) containing 5 g of an aqueous pigment dispersion. ) (Wilhelmi method).
As a result of measurement of the surface tension, the surface tension of the aqueous pigment dispersion of Example 3 was 70.1 mN / m, the surface tension of Comparative Example 2 was 61.2 mN / m, and the polymer obtained in Example 3 was When used, the pigment can be dispersed in water without substantially reducing the surface tension of water.

Claims (11)

The manufacturing method of the graft polymer which has the following process (1)-(3).
Step (1): Configuration derived from a functional group-containing monomer (B) capable of reacting with a structural unit derived from a protected carboxylic acid group-containing monomer (A) and a polymerization initiator having a radically transferable atom or atomic group Step of synthesizing a main chain composed of a polymer containing units by an atom transfer radical polymerization method Step (2): Polymerization having a radically transferable atom or atomic group in the main chain obtained in step (1) Step of introducing initiator Step (3): Step of synthesizing a graft polymer containing a structural unit derived from a hydrophobic monomer in the side chain of the main chain obtained in step (2) by an atom transfer radical polymerization method Furthermore, the manufacturing method of the graft polymer of Claim 1 which has the following process (d).
Step (d): A step of removing a protecting group in the graft polymer obtained in Step (3).   The manufacturing method of the graft polymer of Claim 1 or 2 whose number average molecular weights of a graft polymer are 3000-50000.   The manufacturing method of the graft polymer in any one of Claims 1-3 whose hydrophobic monomer is a styrene-type monomer in a process (3).   The manufacturing method of the graft polymer of Claim 4 whose ratio of the structural unit derived from a styrene-type monomer is 10-60 mass% in all the graft polymers.   The method for producing a graft polymer according to any one of claims 1 to 5, wherein in the step (1), the functional group of the functional group-containing monomer (B) is a hydroxy group, an amino group, or an epoxy group.   In step (1), the protected carboxylic acid group-containing monomer (A) is t-butyl (meth) acrylate, n-butyl (meth) acrylate, trimethylsilyl (meth) acrylate, or 2-tetrahydropyranyl (meth). The manufacturing method of the graft polymer in any one of Claims 1-6 which is an acrylate.   The method for producing a graft polymer according to any one of claims 1 to 7, wherein in the step (2), the polymerization initiator is an acid halide.   A graft polymer obtained by the method according to claim 1.   The graft polymer according to claim 9, wherein the molecular weight distribution index (weight average molecular weight / number average molecular weight) is 2.0 or less.   An aqueous pigment dispersion containing the graft polymer according to claim 9 or 10.