dispersant

Abstract

The present invention provides a dispersant which is a copolymer of (a) a polyalkylene glycol mono(meth)acrylate and (b) a monomer capable of polymerizing with the aforementioned polyalkylene glycol mono(meth)acrylate, the aforementioned (a) polyalkylene glycol mono(meth)acrylate being represented by formula (1): CH2=CR-COO-(AO) n -H represents, and w b calculated from a chromatogram determined by gel permeation chromatography f The ratio w b / w f satisfies the relationship of formula (2): 0.25 ≤ w b / w f ≤ 0.90 (the symbols in formulas (1) and (2) are defined as described in the description), and the molar ratio of the aforementioned polyalkylene glycol mono(meth)acrylate to the aforementioned monomer in the aforementioned copolymer is 30:70 to 90:10.

Description

Technical Field

[0001] This invention relates to dispersants, and more particularly to dispersants for pigments (hereinafter sometimes referred to as "pigment dispersants"). Background Technology

[0002] In recent years, from the perspectives of small-batch printing, cost reduction, and miniaturization of printing presses, plate-free digital printing methods are rapidly gaining popularity. As one of the digital printing methods, inkjet printing has advantages such as easy full-color printing and the ability to obtain high-resolution images at a lower cost, and therefore, it is widely used in both industrial and consumer applications.

[0003] Inkjet printing uses inks from various branches, including oil-based, solvent-based, active energy radiation curing, and water-based inks. These inks are mainly divided into dye inks and pigment inks. Due to their superior weather resistance and water resistance compared to dye inks, research on pigment inks has been ongoing in recent years.

[0004] Pigment inks achieve high tinting strength and vivid hues by finely dispersing solid pigments. However, pigments lacking dispersion stability will re-agglomerate even after fine dispersion, leading to a decrease in hue and an increase in viscosity. Therefore, to stabilize the dispersion, methods such as coating the pigment surface with polyalkylene glycol mono(meth)acrylate are used.

[0005] For example, Patent Document 1 describes an inkjet recording ink containing water and pigments whose surfaces are coated with a UV-curable resin. As polymerizable compounds used to form the aforementioned UV-curable resin, Patent Document 1 describes polypropylene glycol monomethacrylates and methoxy polyethylene glycol monomethacrylates.

[0006] Furthermore, Patent Document 2 describes a pigment dispersant belonging to an ABC triblock copolymer, wherein the ABC triblock copolymer comprises polymer chains A, B, and C having structural units derived from methacrylates that do not have acidic functional groups (i.e., "acid groups" as described in Patent Document 2). As the aforementioned methacrylates without acidic functional groups, Patent Document 2 describes hydroxyl-containing methacrylates such as polyethylene glycol methacrylate and polypropylene glycol methacrylate.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2005-220239

[0010] Patent Document 2: Japanese Patent Application Publication No. 2019-210389 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] In recent years, the demand for water-based inks has been increasing from the perspective of environmental burden, and the use of mixed solvents of alcohol and water is becoming more common. However, for conventional compositions containing copolymers of polyalkylene glycol mono(meth)acrylate and other monomers (especially water-based inks), if the ratio of water and / or alcohol in the composition changes, the viscosity difference caused by the difference in shear rate (e.g., the difference between the viscosity measured at a shear rate of 10 (1 / s) and the viscosity measured at a shear rate of 100 (1 / s)) of the aforementioned compositions sometimes becomes larger.

[0013] Inkjet printing inks use various pigments, and the ratio of water and / or alcohol is determined based on the pigments used. Determining the water and / or alcohol ratio can sometimes be complex if the viscosity difference is large due to variations in shear rate. Therefore, it is desirable to develop dispersants that can reduce viscosity differences caused by variations in shear rate even when the water and / or alcohol ratio changes.

[0014] The present invention was made in view of this situation, and its object is to provide a dispersant that can reduce the viscosity difference of the aforementioned composition caused by the difference in shear rate when the proportion of water and / or alcohol in the composition containing the dispersant changes.

[0015] Methods for solving problems

[0016] In order to achieve the above-mentioned objective, the inventors conducted in-depth research and found that a composition containing a copolymer of polyalkylene glycol mono(meth)acrylate with a specific molecular weight distribution and other monomers as a dispersant can reduce the viscosity difference caused by the difference in shear rate when the proportion of water and / or alcohol in the composition changes, thereby completing the present invention.

[0017] The present invention, which achieves the above objectives, is shown below.

[0018] [1] The dispersant is a copolymer of (a) polyalkylene glycol mono(meth)acrylate and (b) a monomer capable of polymerizing the aforementioned polyalkylene glycol mono(meth)acrylate (excluding polyalkylene glycol mono(meth)acrylate), wherein (a) polyalkylene glycol mono(meth)acrylate is represented by formula (1), and w is calculated from the chromatogram determined by gel permeation chromatography. b with w f The ratio w b / w f Satisfying the relationship in equation (2),

[0019] CH2=CR-COO-(AO) n -H (1)

[0020] In formula (1), R represents a hydrogen atom or a methyl group; AO represents at least one alkylene group with 2 to 4 carbon atoms. When there are two or more AO groups, (AO) n The addition form can be either block or random; and n represents the average number of moles of oxoalkylene addition, which is a number from 5 to 100.

[0021] 0.25≤w b / w f ≤0.90 (2)

[0022] In equation (2), the retention time at the maximum peak height (h) in the aforementioned chromatogram is set as t. h 1 / 10 of the maximum peak height (h) 1 / 10 Let the two retention times at point ) be t. f and t b (where t) f <t b When w f Indicates t h With t f The difference (t) h -t f ), and w b Indicates t b With t h The difference (t) b -t h ). )

[0023] The molar ratio of the aforementioned polyalkylene glycol mono(meth)acrylate to the aforementioned monomer in the aforementioned copolymer (the aforementioned polyalkylene glycol mono(meth)acrylate: the aforementioned monomer) is 30:70 to 90:10.

[0024] Invention Effects

[0025] The viscosity difference caused by the difference in shear rate is small even if the ratio of water and / or alcohol in the composition containing the dispersant of the present invention (i.e., the copolymer of the aforementioned polyalkylene glycol mono(meth)acrylate and the aforementioned monomer) changes. Attached Figure Description

[0026] Figure 1 It is a model of the chromatogram obtained by gel permeation chromatography of polyalkylene glycol mono(meth)acrylate. Detailed Implementation

[0027] The present invention will now be described in detail. It should be noted that the numerical range specified by the symbol “~” in this specification includes the values ​​at both ends (upper and lower limits) of “~”. For example, “2~4” means 2 or more and 4 or less.

[0028] The dispersant of the present invention is a copolymer of (a) polyalkylene glycol mono(meth)acrylate (hereinafter sometimes referred to as "component (a)") and (b) a monomer capable of polymerizing the aforementioned polyalkylene glycol mono(meth)acrylate (excluding polyalkylene glycol mono(meth)acrylate) (hereinafter sometimes referred to as "component (b)"), wherein (a) polyalkylene glycol mono(meth)acrylate is represented by formula (1), and w is calculated from the chromatogram obtained by gel permeation chromatography. b with w f The ratio w b / w f The relationship satisfies equation (2).

[0029] CH2=CR-COO-(AO) n -H (1)

[0030] In formula (1), R represents a hydrogen atom or a methyl group; AO represents at least one alkylene group with 2 to 4 carbon atoms. When there are two or more AO groups, (AO) n The addition form can be either block or random; and n represents the average number of moles of oxoalkylene addition, which is a number from 5 to 100.

[0031] 0.25≤w b / w f ≤0.90 (2)

[0032] In equation (2), the retention time at the maximum peak height (h) in the aforementioned chromatogram is set as t. h 1 / 10 of the maximum peak height (h) 1 / 10 Let the two retention times at point ) be t. f and t b (where t) f <t b When w f Indicates t h With t f The difference (t) h -t f ), and w b Indicates t b With t h The difference (t) b -t h ). )

[0033] In this specification, "polyalkylene glycol mono(meth)acrylate" means "polyalkylene glycol monoacrylate or polyalkylene glycol monomethacrylate". Here, polyalkylene glycol mono(meth)acrylate may be used alone or in combination with two or more. Furthermore, both component (a) and component (b) may be used alone or in combination with two or more.

[0034] AO represents at least one oxoalkylene group having 2 to 4 carbon atoms. That is, AO is selected from at least one of oxoethylene, oxopropylene, and oxobutylene. AO is preferably oxopropylene or a combination of oxoethylene and oxopropylene, more preferably oxopropylene. n is the average number of moles of oxoalkylene added. Therefore, n can be a decimal. n is preferably 5 to 60, more preferably 5 to 50, and even more preferably 5 to 40.

[0035] The w of component (a) was calculated from the chromatogram (vertical axis: refractive index intensity, horizontal axis: retention time) obtained by gel permeation chromatography (GPC) performed using a differential refractometer. b with w f The ratio w b / w f Satisfying the relationship in equation (2) is one of the features of this invention (see reference). Figure 1 ).

[0036] 0.25≤w b / w f ≤0.90 (2)

[0037] In equation (2), the retention time at the maximum peak height (h) in the aforementioned chromatogram is set as t. h 1 / 10 of the maximum peak height (h) 1 / 10 Let the two retention times at point ) be t. f and t b (where t) f <t b When w f Indicates t h With t f The difference (t) h -t f ), and w b Indicates t b With t h The difference (t) b -t h ). )

[0038] If w b / w fIf the value is less than 0.25, the molecular weight distribution of component (a) becomes more heavily biased towards the high molecular weight side, the concentration of polymerizable functional groups decreases, and the polymerizability of component (a) may decrease. From the perspective of polymerizability, w b / w f Preferably, it is 0.30 or higher, and more preferably 0.35 or higher.

[0039] On the other hand, if w b / w f If the viscosity is greater than 0.90, the viscosity difference caused by the difference in shear rate increases when the ratio of water and / or alcohol in the composition containing the dispersant of the present invention changes. To reduce the viscosity difference caused by the difference in shear rate, w b / w f Preferably, it is 0.85 or less, more preferably 0.80 or less, and even more preferably 0.60 or less.

[0040] Used to calculate w b / w f The chromatograms (vertical axis: refractive index intensity, horizontal axis: retention time) were obtained as follows: An HLC-8320GPC (registered trademark) was used as the gel permeation chromatography (GPC) system, with a SHODEX KF-G guard column and three consecutive Shodex KF804L columns. The column temperature was set to 40°C, and tetrahydrofuran was flowed at a flow rate of 1 mL / min as the developing solvent. 0.1 mL of a 0.1 wt% tetrahydrofuran solution of polyalkylene glycol mono(meth)acrylate was injected, and the results were obtained using the EcoSEC GPC calculation program.

[0041] Component (a) can be produced by adding at least one selected from ethylene oxide, propylene oxide, and butene oxide (preferably propylene oxide) to a starting material (e.g., 2-hydroxypropyl (meth)acrylate) in the presence of a complex metal cyanide catalyst (hereinafter sometimes simply referred to as "DMC catalyst"). Specifically, the starting material and DMC catalyst are added to a reaction vessel, and at least one selected from ethylene oxide and propylene oxide (hereinafter collectively referred to as "olefin oxides with 2 to 4 carbon atoms") is added continuously or intermittently under stirring in an inactive gas atmosphere, and polymerization is carried out. olefin oxides with 2 to 4 carbon atoms can be added under pressure or at atmospheric pressure.

[0042] The average supply rate of olefins with 2 to 4 carbon atoms is not limited, and it is desirable to vary it according to the amount of olefins with 2 to 4 carbon atoms fed. When the rate (supply per unit time) for a period of 5% to 20% of the total supply of olefins with 2 to 4 carbon atoms is defined as V1, the rate for a period of more than 20% to 50% of the total supply of olefins with 2 to 4 carbon atoms is defined as V2, and the rate for a period of more than 50% to 100% of the total supply of olefins with 2 to 4 carbon atoms is defined as V3, in one method for manufacturing component (a), it is preferable to control the average supply rate of olefins with 2 to 4 carbon atoms in a manner where V1 / V2 = 1.1 to 2.0 and V2 / V3 = 1.1 to 1.5. In another method for manufacturing component (a), it is preferable to control the average supply rate of olefin oxides with 2 to 4 carbon atoms in a manner where V1 / V2 = 0.4 to 0.9 and V2 / V3 = 0.5 to 0.95.

[0043] Furthermore, the reaction temperature for adding 2-4 carbon olefins to the starting material is preferably 50°C to 120°C, more preferably 70°C to 90°C. If the reaction temperature is below 50°C, the reaction rate is very low; if it is above 120°C, polymerization of polymerizable groups in the starting material and coloring problems occur.

[0044] There are no particular limitations on the trace amounts of water contained in the starting materials and the olefins with 2 to 4 carbon atoms, but the water content in the starting materials is expected to be less than 0.5% by weight, and the water content in the olefins with 2 to 4 carbon atoms is expected to be less than 0.01% by weight.

[0045] The amount of DMC catalyst is not particularly limited, but is preferably 0.0001 to 0.1 parts by weight, more preferably 0.001 to 0.05 parts by weight, relative to 100 parts by weight of the generated olefin oxide derivative (i.e., component (a)). The DMC catalyst can be added to the reaction system all at once initially, or it can be added in batches sequentially. After the polymerization reaction is complete, the DMC catalyst is removed. Catalyst removal can be carried out by known methods such as filtration, centrifugation, or treatment based on a synthetic adsorbent.

[0046] In the manufacture of polyalkylene glycol mono(meth)acrylate, known catalysts can be used as DMC catalysts. For example, the catalyst shown in formula (3) can be used as a DMC catalyst.

[0047] M a [M' x (CN) y ] b (H2O) c ·(L) d(3)

[0048] (In equation (3), M and M' represent metal atoms; L represents organic ligands; and a, b, c, d, x, and y represent positive integers.)

[0049] Examples of metal atoms (metal cations) M include Zn(II), Fe(II), Fe(III), Co(II), Ni(II), Al(III), Sr(II), Mn(II), Cr(III), Cu(II), Sn(II), Pb(II), Mo(IV), Mo(VI), W(IV), and W(VI). Among these, Zn(II) is preferred.

[0050] Examples of metal atoms (metal cations) M' include Fe(II), Fe(III), Co(II), Co(III), Cr(II), Cr(III), Mn(II), Mn(III), Ni(II), V(IV), V(V), etc. Among these, Fe(II), Fe(III), Co(II), and Co(III) are preferred.

[0051] As the organic ligand L, alcohols, ethers, ketones, esters, etc., can be used, with alcohols being more preferred. Preferred organic ligands are water-soluble ligands; specific examples include tert-butanol, n-butanol, isobutanol, N,N-dimethylacetamide, ethylene glycol dimethyl ether (glycol dimethyl ether), and diethylene glycol dimethyl ether (diethylene glycol dimethyl ether). A particularly preferred DMC catalyst is Zn(II)3[Co(III)(CN)6]2(H2O)4(tert-butanol)2, which is coordinated with tert-butanol.

[0052] In reactions in which 2- to 4-carbon olefins are added to starting materials, other additives can be used. For example, hydroquinone (HQ), hydroquinone monomethyl ether (MQ), 2,6-di-tert-butylhydroxytoluene (BHT), di-tert-butylhydroxyanisole (BHA), α-tocopherol, β-tocopherol, γ-tocopherol, etc., can be added to the reaction system as polymerization inhibitors. MQ and / or BHT are preferred as polymerization inhibitors, and BHT is more preferred. The amount of polymerization inhibitor added is preferably 0.001 to 0.3 parts by weight relative to 100 parts by weight of the starting material (e.g., 2-hydroxypropyl methacrylate) and the 2- to 4-carbon olefins. If this amount is less than 0.001 parts by weight, the polymerization inhibitor may not function sufficiently, and gelation may occur during the addition of the 2- to 4-carbon olefins. On the other hand, if this amount is more than 0.3 parts by weight, the purity of the resulting polyalkylene glycol mono(meth)acrylate may sometimes be low.

[0053] Component (b) is a monomer capable of polymerizing with component (a) (excluding polyalkylene glycol mono(meth)acrylate). Examples of components (b) include styrene, vinyl acetate, acrylate, methacrylate, maleate, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, isobutylene, diisobutylene, vinylcyclohexane, and other compounds having olefinic unsaturated bonds; vinyl sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, maleic acid, and other compounds having acidic functional groups and olefinic unsaturated bonds; and salt forms of maleate salts and other compounds having acidic functional groups and olefinic unsaturated bonds. To reduce the viscosity difference in compositions containing the dispersant of the present invention due to differences in shear rate, component (b) is preferably a compound having acidic functional groups and olefinic unsaturated bonds, more preferably acrylic acid or methacrylic acid, and even more preferably acrylic acid.

[0054] One feature of this invention is that the molar ratio (component (a):component (b)) of component (a):component (b) in the copolymer is 30:70 to 90:10. Here, "molar ratio of component (a) to component (b) in the copolymer" refers to the molar ratio of structural units derived from component (a) (i.e., the aforementioned polyalkylene glycol mono(meth)acrylate) to structural units derived from component (b) (i.e., the aforementioned monomer), which can be adjusted using the mixing ratio (molar ratio) of component (a) and component (b) during copolymer manufacturing. When the proportion of water and / or alcohol in the composition containing the dispersant of this invention changes outside the aforementioned molar ratio range of 30:70 to 90:10, the viscosity difference of the aforementioned composition due to differences in shear rate increases. The aforementioned molar ratio is preferably 40:60 to 87:13, more preferably 40:60 to 85:15, and even more preferably 40:60 to 80:20.

[0055] The dispersant, i.e., copolymer, of the present invention can be manufactured by known polymerization methods such as solution polymerization using a solvent or bulk polymerization without a solvent, and the polymerization method is not particularly limited. Hereinafter, the polymerization method of the dispersant, i.e. copolymer, of the present invention will be described sequentially, but the present invention is not limited to the following polymerization methods.

[0056] When polymerization is carried out in the presence of a solvent, examples of solvents include water; alcohols such as methanol, ethanol, and isopropanol; ketones such as acetone and methyl ethyl ketone; cyclic ethers such as tetrahydrofuran and dioxane; aliphatic hydrocarbons such as n-hexane, 2-ethylhexane, and methylcyclohexane; and aromatic hydrocarbons such as toluene and xylene. Methanol, ethanol, and isopropanol are suitable solvents. When using a solvent, its amount is preferably 100 to 250 parts by weight, more preferably 100 to 200 parts by weight, relative to the total of 100 parts by weight of components (a) and (b). The solvent used in polymerization can be removed after polymerization by distillation or other operations, or it can be used as part of a composition containing the copolymer. It should be noted that solution polymerization can be carried out in a batch or continuous manner.

[0057] In manufacturing the dispersant, i.e., copolymer, of the present invention, a polymerization initiator is preferably used. Examples of polymerization initiators include peroxide-based initiators such as benzoyl peroxide; azo-based initiators such as 2,2'-azobis(2,4-dimethylpentanonitrile); and persulfate-based initiators such as ammonium persulfate and sodium persulfate. Furthermore, the polymerization temperature is preferably 50–130°C, more preferably 60–90°C, and the polymerization time is preferably 2–10 hours, more preferably 3–5 hours.

[0058] To reduce the water solubility of the resulting copolymer (i.e., the dispersant of the present invention) and the viscosity difference in the composition containing the aforementioned copolymer due to differences in shear rate, an azo initiator is preferably used in the polymerization of the aforementioned copolymer, and 2,2'-azobis(2,4-dimethylpentanonitrile) is particularly preferred. When using an azo initiator, its amount relative to 100 moles of the total of components (a) and (b) is preferably 1 to 10 moles, more preferably 5 to 9 moles.

[0059] Additionally, one or more chain transfer agents may be used as needed. Examples of chain transfer agents include dodecyl mercaptan and α-methylstyrene dimer. When using a chain transfer agent, its amount is preferably 1 to 20 moles relative to a total of 100 moles of components (a) and (b).

[0060] From the viewpoint of suppressing viscosity differences caused by variations in shear rates, the weight-average molecular weight of the dispersant (i.e., the aforementioned copolymer) of the present invention is preferably 5,000 to 50,000, more preferably 10,000 to 30,000, and even more preferably 13,000 to 30,000. The aforementioned weight-average molecular weight is a value obtained by gel permeation chromatography under the conditions described above.

[0061] The dispersant of the present invention can be used to disperse pigments and the like in a dispersion medium. The dispersant of the present invention is preferably a pigment dispersant.

[0062] Example

[0063] (Synthesis of complex metal cyanide (DMC) catalysts)

[0064] A 15 mL aqueous solution containing 60.84 g of potassium hexacyanocobaltate (K3Co(CN)) was added dropwise over 15 minutes at 40 °C with stirring. This was then added to a 2.0 mL aqueous solution containing 2.1 g of zinc chloride. After the addition was complete, 16 mL of water and 16 g of tert-butanol were added, and the mixture was heated to 70 °C and stirred for 1 hour. After cooling to room temperature, the mixture was filtered (first filtration) to obtain a solid. 14 mL of water and 8.0 g of tert-butanol were added to this solid, and after stirring for 30 minutes, the mixture was filtered (second filtration) to obtain another solid.

[0065] Add 18.6 g of tert-butanol and 1.2 g of methanol to the obtained solid. After stirring for 30 minutes, perform the filtration operation (third time). Dry the obtained solid at 40 °C under reduced pressure for 3 hours to obtain 0.7 g of DMC catalyst (Zn(II)3[Co(III)(CN)6]2(H2O)4(tert-butanol)2).

[0066] (Synthesis of polyalkylene glycol mono(meth)acrylate)

[0067] (Synthesis of component (a1))

[0068] 500 g of 2-hydroxypropyl methacrylate (0.02 wt% water), 0.3 g of DMC catalyst obtained in the same manner as in Synthesis Example 1, and 0.6 g of 2,6-di-tert-butylhydroxytoluene (BHT) were added to a 5-liter (4,890 mL) stainless steel pressure-resistant reactor equipped with a thermometer, pressure gauge, safety valve, nitrogen inlet pipe, stirrer, vacuum exhaust pipe, cooling coil, and steam jacket. After nitrogen purging, the temperature was raised to 70 °C, and 403 g of propylene oxide (methyl ethylene oxide, 0.005 wt% water) was added dropwise through the nitrogen inlet pipe while stirring under conditions below 0.3 MPa. The pressure and temperature changes in the reactor over time were observed. Five hours after the addition of 403 g of propylene oxide, the pressure in the reactor decreased sharply. Subsequently, while maintaining the reaction vessel at 70°C, 1132 g of propylene oxide was slowly added dropwise through a nitrogen inlet tube under pressure below 0.5 MPa. It should be noted that the average feed rates were V1 162 g / h, V2 267 g / h, and V3 289 g / h (V1 / V2 = 0.61, V2 / V3 = 0.92). After the addition was complete, the reaction was allowed to proceed at 70°C for 0.5 hours. The reaction mixture was then removed from the reaction chamber and filtered to remove solids, yielding the liquid component (a1). The obtained component (a1) was determined by gel permeation chromatography using the aforementioned HLC-8320GPC (registered trademark).

[0069] (Synthesis of components (a2) and (a3))

[0070] As shown in Table 1 below, the starting materials, the type of olefin oxide, and the molar number of additions were changed. Otherwise, components (a2) and (a3) ​​were synthesized using the same method as that used for component (a1). The resulting components (a2) and (a3) ​​were then determined by gel permeation chromatography in the same manner as described above.

[0071] (Synthesis of component (a4))

[0072] 500 g of 2-hydroxypropyl methacrylate, 17.6 g of boron trifluoride diethyl ether complex, and 0.6 g of hydroquinone monomethyl ether (MQ) were added to a 5-liter (4,890 mL) stainless steel pressure-resistant reaction apparatus equipped with a thermometer, pressure gauge, safety valve, nitrogen inlet tube, stirrer, vacuum exhaust tube, cooling coil, and vapor jacket. After nitrogen purging, the temperature was raised to 60 °C, and 1578 g of propylene oxide (methyl ethylene oxide) was added dropwise through the nitrogen inlet tube while stirring, under pressure below 0.3 MPa. After the addition was complete, the reaction was allowed to proceed at 60 °C for 0.5 hours. After the addition of water and hexane, neutralization was performed using an aqueous sodium hydroxide solution. After removing the aqueous layer, hexane and water were removed by distillation under reduced pressure. The concentrate was filtered to remove solids, yielding a liquid component (a4). Component (a4) was then analyzed by gel permeation chromatography in the same manner as described above.

[0073] The starting materials used to synthesize components (a1) to (a4), R, AO and n in formula (1) of components (a1) to (a4), and w of components (a1) to (a4) are used. b / w f The molecular weights are shown in Table 1. It should be noted that the molecular weights of components (a1) to (a4) are calculated based on the hydroxyl values ​​of components (a1) to (a4) as determined according to JIS K-1557-1.

[0074] [Table 1]

[0075]

[0076] E0: Ethyloxyethylene, PO: Propyleneoxyethylene

[0077] (Synthesis of copolymers)

[0078] (Synthesis of copolymer 1)

[0079] 95 g (0.16 mol) of component (a1), 5.0 g (0.07 mol) of acrylic acid (b), and 150 g of isopropanol as solvent were added to a 0.3 L flask equipped with a stirrer, thermometer, and nitrogen inlet tube. Under a nitrogen atmosphere, 3.5 g (0.01 mol) of 2,2'-azobis(2,4-dimethylpentanonitrile) (“V-65” manufactured by Fujifilm and Koh Genuine Chemicals Co., Ltd.) was added as a polymerization initiator, and polymerization was carried out at 70 ± 5 °C for 3 hours to obtain copolymer 1 (Example 1).

[0080] (Synthesis of copolymers 2-6)

[0081] As shown in Table 2, the types of components (a) and (b), as well as the mixing ratio (molar ratio) of components (a) and (b), were changed. Otherwise, copolymers 2 to 5 (Examples 2 to 5) and copolymer 6 (Comparative Example 1) were obtained using the same method as the synthesis of copolymer 1.

[0082] The weight-average molecular weight of the obtained copolymers was determined by the above gel permeation chromatography. The results are shown in Table 2.

[0083] [Table 2]

[0084] The types of components (a) and (b), the mixing ratio (molar ratio) of components (a) and (b), and the weight-average molecular weight of the copolymer.

[0085]

[0086] (Preparation of solutions (compositions) containing copolymers)

[0087] Copolymer 1 is mixed with the solvents shown in Table 3 in the amounts shown in Table 3 to prepare solutions 1-4 containing copolymer 1. Similarly, solutions 1-4 containing any one of copolymers 2-6 are prepared.

[0088] [Table 3]

[0089] copolymer Isopropanol diethylene glycol Ion-exchanged water Solution 1 25 75 - - Solution 2 25 56.3 - 18.8 Solution 3 25 37.5 - 37.5 Solution 4 25 37.5 18.7 188

[0090] Units for each component: parts by weight

[0091] (Evaluation of solutions containing copolymers)

[0092] The viscosity of solutions 1 to 4 obtained by the above procedure was measured at a shear rate of 10 (1 / s) (hereinafter referred to as "Vis(10)") and at a shear rate of 100 (1 / s) (hereinafter referred to as "Vis(100)"). Using an Anton Paar viscoelasticity measuring apparatus MCR302 and a measuring probe (cone plate, CP25-2) (Anton Paar), at a solution temperature of 20°C, the shear rate was varied from 0.1 (1 / s) to 100 (1 / s), and Vis(10) and Vis(100) were measured.

[0093] Calculate the “Vis(10)-Vis(100)” (hereinafter sometimes referred to as “viscosity difference”) of solutions 1–4, and evaluate them according to the following criteria. The results are shown in Table 4 below.

[0094] (Benchmark)

[0095] 〇: Viscosity difference within ±1 mPa·s

[0096] ×: Viscosity difference exceeds ±1 mPa·s

[0097] [Table 4]

[0098]

[0099] As shown in Table 4, the viscosity difference of solutions 1 to 4 containing copolymers 1 to 5 (Examples 1 to 5) is small compared to solutions 1 to 4 containing copolymer 6 (Comparative Example 1).

[0100] (Evaluation of the dispersion properties of copolymers 1-5)

[0101] The dispersion properties of copolymers 1-5 (Examples 1-5) satisfying the conditions of the present invention were evaluated as follows. Specifically, 1 g of any one of copolymers 1-5, 3 g of isopropanol, and 0.1 g of copper phthalocyanine organic pigment (manufactured by Toyokara Co., Ltd., product name: NO.700-10FG CYBLUE) were added to a 9 mL sample vial, and the mixture was ultrasonically treated for 1 hour to prepare a pigment dispersion. For reference, 4 g of isopropanol and 0.1 g of the aforementioned pigment were added to a 9 mL sample vial, and the mixture was ultrasonically treated for 1 hour to prepare a dispersion without added copolymers. After ultrasonic treatment, the resulting dispersions were allowed to stand for 4 hours, and the presence or absence of sedimentation of the aforementioned pigment in the dispersions was visually confirmed. The results are shown in Table 5 below.

[0102] [Table 5]

[0103] Did the pigment settle? copolymer 1 none copolymer 2 none copolymer 3 none copolymer 4 none copolymer 5 none No additions have

[0104] As shown in Table 5, no precipitation of the aforementioned pigments was observed visually after standing for 4 hours in the dispersion containing copolymers 1 to 5, confirming that copolymers 1 to 5 are dispersants with good dispersing properties.

[0105] Industrial utilization

[0106] The dispersant of the present invention is useful for dispersing pigments and the like into a dispersion medium.

[0107] This application is based on Japanese Patent Application No. 2021-67606, the entire contents of which are included in this application specification.

[0108] Explanation of reference numerals in the attached figures

[0109] h Maximum peak height

[0110] h 1 / 10 1 / 10 of the maximum peak height

[0111] t h Retention time at maximum peak height (h)

[0112] t f 1 / 10 of the maximum peak height (h) 1 / 10 The retention time at t (where t) f <t b )

[0113] t b 1 / 10 of the maximum peak height (h) 1 / 10 The retention time at t (where t) f <t b )

[0114] w f t h With t f The difference (t) h -t f )

[0115] w b t b With t h The difference (t) b -t h )

Claims

1. A dispersant, which is a copolymer of (a) a polyalkylene glycol mono(meth)acrylate and (b) a monomer capable of polymerizing the aforementioned polyalkylene glycol mono(meth)acrylate, wherein (a) the polyalkylene glycol mono(meth)acrylate is represented by formula (1), and w is calculated from a chromatogram obtained by gel permeation chromatography. b with w f The ratio w b / w f The monomers that satisfy the relationship of equation (2), wherein (b) can polymerize with the aforementioned polyalkylene glycol mono(meth)acrylate, do not include polyalkylene glycol mono(meth)acrylate. CH2=CR-COO-(AO) n -H (1) In formula (1), R represents a hydrogen atom or a methyl group; AO represents at least one alkylene group with 2 to 4 carbon atoms. When there are two or more AO groups, (AO) n The addition form is either block or random; and n represents the average number of moles of oxoalkylene addition, which is a number from 5 to 100. 0.25≤w b / In f ≤0.90 (2) In equation (2), the retention time at the maximum peak height (h) in the chromatogram is set as t. h 1 / 10 of the maximum peak height (h) 1 / 10 Let the two retention times at point ) be t. f and t b And t f <t b At that time, w f Indicates t h With t f The difference (t) h -t f ), and w b Indicates t b With t h The difference (t) b -t h ), The molar ratio of the polyalkylene glycol mono(meth)acrylate to the monomer in the copolymer is 30:70 to 90:10.

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