JP4563065B2 - Dispersant for inorganic pigment - Google Patents

Description

  The present invention relates to an inorganic pigment dispersant suitably used when an inorganic pigment is dispersed in water or the like to obtain a slurry, and a pigment dispersion composition containing the dispersant.

  In dispersing an inorganic pigment in an aqueous medium to form a slurry, a polycarboxylate-based dispersant is used. For example, a salt of a copolymer of acrylic acid and maleic acid is known, but as the concentration of the slurry is increased, sufficient dispersion performance cannot be obtained.

Patent Document 1 reports an improvement in dispersion performance by a combination of two kinds of copolymers having different copolymerization molar ratios of acrylic acid and maleic acid. However, for example, when the inorganic pigment slurry is applied in a state where shear (shear) is applied like spray for application in water-based paint, etc., the slurry viscosity is greatly different (thixotropic property is different). It was pointed out that it would interfere with workability.
JP-A-8-188986

  An object of the present invention is to provide a dispersant for an inorganic pigment that can change the viscosity of the inorganic pigment slurry due to the influence of the share and can also reduce the viscosity value, and a pigment dispersion composition containing the dispersant.

The present invention provides an inorganic pigment dispersant containing the following components (A) and (B) in a ratio of (A) / (B) = 50/50 to 96/4 (weight ratio), and the inorganic Provided is a pigment dispersion composition containing a pigment dispersant.
(A) component:
An unsaturated monobasic acid having a constituent monomer unit ratio of unsaturated monobasic acid / unsaturated dibasic acid (molar ratio) = 91/9 to 74/26 and a weight average molecular weight (Mw) of 25,000 to 60,000 Salt (B) component of copolymer with unsaturated dibasic acid:
An unsaturated monobasic acid having a constituent monomer unit ratio of unsaturated monobasic acid / unsaturated dibasic acid (molar ratio) = 63/37 to 47/53 and a weight average molecular weight (Mw) of 25,000 to 60,000 Salts of copolymers with unsaturated dibasic acids

  The inorganic pigment dispersant of the present invention has a small change in the viscosity of the inorganic pigment slurry due to the influence of the shear, and can also have a low viscosity value.

  Examples of the unsaturated monobasic acid constituting the copolymer of each of the components (A) and (B) of the present invention include acrylic acid, methacrylic acid, crotonic acid and the like, but acrylic acid and methacrylic acid are preferred. Examples of the unsaturated dibasic acid include maleic anhydride, maleic acid, itaconic acid, fumaric acid and the like, and maleic anhydride, maleic acid and itaconic acid are preferred.

  The salt of the copolymer of each of the component (A) and the component (B) of the present invention is at least one selected from alkali metal salts, alkaline earth metal salts, quaternary ammonium salts, ammonium salts, and organic amine salts. preferable.

  Examples of the alkali metal constituting the salt include sodium, potassium, and lithium. Examples of the alkaline earth metal include magnesium, calcium, and barium. Examples of the quaternary ammonium include tetramethylammonium hydroxide and triethylmethylammonium hydroxide. Examples of the organic amine include diethanolamine, triethanolamine, ethylenediamine, diethylenetriamine, triethylamine, and tributylamine.

  Among these, preferred are alkali metal salts, and sodium salts and potassium salts are more preferable from the viewpoint of lowering the viscosity of a high-concentration slurry of pigment and stabilizing the low-viscosity slurry for a long period of time. Ammonium salts are preferred for use in applications where ash content remains, such as electronic materials.

  The degree of neutralization or alkali excess of the salt of the copolymer of each of the components (A) and (B) of the present invention is not particularly defined, but the decomposition resistance, color resistance and odor resistance of the powder component In view of the above, it is usually 50 to 120%, preferably 60 to 110%, more preferably 75 to 105%.

  The degree of neutralization or the excess of alkali means [A (equivalent of free base capable of constituting a salt + equivalent of acid group constituting a salt) / B (free acid group capable of constituting a salt). Equivalent + equivalent of acid group constituting the salt)] × 100 (%). When A / B is 1 or less, the degree of neutralization is expressed, and when A / B = 1, the degree of neutralization is 100%. A / B greater than 1 is expressed as alkali excess and shows a value greater than 100%.

  Moreover, the pH of the aqueous solution of the copolymer salt of each of the component (A) and the component (B) is preferably 5 to 9 from the viewpoint of the decomposition resistance of the powder component, and the resistance to coloring and odor. 5.5 to 8.5 is more preferable, and 6 to 8 is particularly preferable.

  In the component (A) of the present invention, the constituent monomer unit ratio is unsaturated monobasic acid / unsaturated dibasic acid (molar ratio) = 91/9 to 74/26, preferably 91/9 to 80/20. 87/13 to 80/20 are more preferable.

  In addition, the component (B) component of the present invention has a constituent monomer unit ratio of unsaturated monobasic acid / unsaturated dibasic acid (molar ratio) = 63/37 to 47/53, and 61/39 to 48/52. Is preferable, and 59/41 to 50/50 is more preferable.

  The weight average molecular weight (Mw) of each of the component (A) and the component (B) of the present invention is such that the high-concentration slurry of the pigment is reduced in viscosity, the low-viscosity slurry is dispersed and stabilized for a long time, and the viscosity of the slurry under high shear is reduced. From the viewpoint of keeping it small, it is 25000 to 60000, preferably 35000 to 50000, and more preferably 40000 to 50000.

  Here, the weight average molecular weight (Mw) is a value measured by the measuring method described in Examples.

  In addition, the number average molecular weight (Mn) of each of the component (A) and the component (B) of the present invention is such that the high-concentration slurry of the pigment has a low viscosity, the low-viscosity slurry is long-term dispersed and stabilized, and the viscosity of the slurry under high shear is high. Is preferably 20000 to 40000, more preferably 25000 to 38000, and particularly preferably 27000 to 35000. Further, the Mw / Mn of each of the component (A) and the component (B) is preferably 3 or less, more preferably 1.25 to 3, and particularly preferably 1.25 to 2.5.

  In the dispersant of the present invention, the change in the slurry viscosity due to the influence of the share becomes small, and from the viewpoint of excellent adaptability of the coating method (which can be applied by any spraying or brushing coating method), the component (A) and the component (B) Although a component is contained in the ratio of (A) / (B) = 50 / 50-96 / 4 (weight ratio), 55 / 45-85 / 15 are preferable and 60 / 40-80 / 20 are still more preferable.

The dispersant of the present invention has a low viscosity of a high-concentration slurry of pigment, stabilizes the low-viscosity slurry for a long period of time, and maintains a low viscosity of the slurry under high shear, in the presence of 80 mg / L of calcium ions. The clay dispersibility is preferably 15% or more and less than 50%, more preferably 20 to 45%. The clay dispersibility in the presence of 21 mg / L of magnesium ions is preferably 46% or more and less than 60%, and more preferably 46 to 59%. Calcium ion capturing ability is preferably less than 270mgCaCO ₃ / g or more 380mgCaCO ₃ / g, more preferably 290~379mgCaCO ₃ / g.

  The “clay dispersibility” and “calcium ion scavenging ability” as used in the present invention are measured by the measurement methods described in the examples, and are values used as indicators of the properties of the dispersant for inorganic pigments. is there.

  The total content of the component (A) and the component (B) in the dispersant of the present invention is preferably 90 to 100% by weight, more preferably 95 to 100% by weight, in the category where the viscosity of the high concentration slurry of the pigment can be reduced. preferable. The dispersant of the present invention may contain unreacted unsaturated monobasic acid, unsaturated dibasic acid and the like in addition to the components (A) and (B).

  Although the manufacturing method of (A) component and (B) component of this invention is not specifically limited, For example, it can manufacture by the method shown below.

  An unsaturated dibasic acid and ion-exchanged water are charged into a reaction vessel so that the concentration of the unsaturated dibasic acid is 37% by weight or more, heated to 75 ° C., and then an aqueous NaOH solution is added to the amount of the unsaturated dibasic acid charged to 2. Charge in double moles to make Na salt of unsaturated dibasic acid. Next, after heating to about 100 ° C., the unsaturated monobasic acid aqueous solution is heated at this temperature so that the unsaturated monobasic acid / unsaturated dibasic acid (molar ratio) falls within the above range. Are added dropwise over 3 to 5 hours so that hydrogen peroxide is 17 to 50 mol% with respect to the total number of moles of unsaturated monobasic acid and unsaturated dibasic acid charged, and a polymerization reaction is carried out. After completion of dropping, the mixture is aged at 100 ° C. for 1 to 10 hours. After completion of the reaction, the reaction solution is cooled to about 60 ° C., and an alkaline aqueous solution is added so that the pH is 8 to 9, thereby obtaining an Na salt of an unsaturated monobasic acid-unsaturated dibasic acid copolymer.

  Inorganic pigments of interest in the present invention are calcium carbonate, calcium phosphate, zinc phosphate, clay, bentonite, satin white, zinc white, bengara, ferrite, titanium oxide, alumina, magnesium oxide, talc, white carbon, cement, gypsum, Examples thereof include carbon black, titanate, and silicate, and calcium carbonate and titanate such as barium titanate are preferable.

  Specifically, the dispersant of the present invention is effective as a dispersant for light calcium carbonate production process, calcium carbonate wet grinding, paper coating paint, ferrite production process or electronic materials such as barium titanate. . It is also effective for ceramic pigments such as alumina.

  The dispersant of the present invention can be used effectively when obtaining a pigment dispersion composition for coated paper, electronic materials, ceramics, etc., and is particularly preferably used for coated paper. The pigment dispersion composition can be obtained by dispersing an inorganic pigment powder, powder ore or coarse particles in an aqueous medium using the dispersant of the present invention. Examples of the aqueous medium include water or a mixed solution of water and a water-soluble organic solvent such as ethyl alcohol or ethylene glycol, preferably water.

  The content of the pigment in the pigment dispersion composition is not particularly defined, but is preferably 50% by weight or more, more preferably 50 to 85% by weight, and more preferably 65 to 85% from the viewpoint of improving the drying efficiency and increasing the productivity. % Is particularly preferred. Further, the content of the dispersant of the present invention in the pigment dispersion composition is not particularly defined, but is usually preferably 0.01 to 10 parts by weight, more preferably 0.05 to 6 parts by weight with respect to 100 parts by weight of the inorganic pigment. 0.05 to 5 parts by weight is preferable.

  As a method for obtaining a pigment dispersion composition using the dispersant of the present invention, a usual slurrying method is used. For example, a method of adding a pigment to an aqueous solution in which a dispersant is dissolved and stirring and mixing, a method of adding water and a dispersant to the pigment, stirring and mixing, and the like can be mentioned. As a method of stirring and mixing, for example, a generally used stirring device such as a high-speed disper, a homomixer, or a ball mill can be used.

  In addition, when slurrying the pigment ore or coarse particles at the same time as pulverization, a method of adding water and a dispersant to the pigment ore or coarse particles and slurrying at the same time as the pulverization may be mentioned. A generally used wet pulverizer such as a bead mill can be used as a method of slurrying simultaneously with pulverization.

  In the present invention, there is a TI value (thixotropic index) as a method for examining the change in slurry viscosity due to the influence of shear. In this method, the slurry viscosity of the prepared slurry is measured with a B-type viscometer at a constant temperature. At that time, the rotor rotational speed of the viscometer is measured at 6 rpm and 60 rpm, respectively, and the following formula is calculated.

TI value = (viscosity when measured at 6 rpm) / (viscosity when measured at 60 rpm)
The viscosity at the time of measurement at 60 rpm is a state in which the shear is applied, and the smaller the TI value, the smaller the change in slurry viscosity due to the influence of the shear. The TI value is preferably 3 or less, more preferably 1 to 2.5.

  In the pigment dispersion composition of the present invention, the TI value is small, that is, the change in slurry viscosity is small. The reason why such a remarkably excellent effect is manifested is not clear, but from the viewpoint that the change in slurry viscosity is small without being affected by the share, the component (A) is probably the surface potential for inorganic pigments. It is considered that the component (B) contributes to the improvement of the attractive force due to the improvement of the electrostatic repulsion by the application of.

  In the following examples, the physical properties of the dispersant for inorganic pigment were measured by the following methods.

<Weight average molecular weight>
It measured by GPC (gel permeation chromatography) on the following conditions.
Column: TSK PWXL + G4000PWXL + G2500PWXL (both manufactured by Tosoh Corporation)
Column temperature: 40 ° C
Detector: RI or UV (210 nm)
Eluent: 0.2 mol / L phosphate buffer / acetonitrile (9/1)
Flow rate: 1.0 mL / min
Injection volume: 0.1 mL
Standard: Polyethylene glycol <Clay dispersibility>
The following procedure was followed. It should be noted that the method using calcium chloride dihydrate has the ability to disperse clay in the presence of 80 mg / L calcium ion, and the method using magnesium chloride hexahydrate has the ability to use 21 mg / L magnesium ion. Shows clay dispersibility.
1) Prepare a glycine buffer solution by adding ion exchange water to 60.56 g of glycine, 52.6 g of sodium chloride and 60 mL of 1N NaOH aqueous solution to make 600 g.
2) Add ion-exchanged water to 1000 g of calcium chloride dihydrate 0.3268 g or magnesium chloride hexahydrate 0.1937 g and 60 g of the prepared solution of 1) to prepare a dispersion.
3) Prepare 20 g of 0.1 wt% (solid content conversion) inorganic pigment dispersant aqueous solution.
4) Put 0.3g of JIS test powder 1,8 types (Kanto loam, fine particles: Japan Powder Industrial Technology Association) into the test tube, and add 2g of preparation liquid 27g and 3g of preparation liquid 3g. To do.
5) After sealing the test tube with parafilm, shake the test tube and check that there is no lump at the bottom of the test tube, then shake the test tube up and down 20 times.
6) Leave the test tube of 5) in a place not exposed to direct sunlight for 20 hours.
7) After 20 hours, collect 5 mL of the supernatant of the dispersion with a whole pipette into a 20 mL screw tube.
8) Measure the transmittance (T%) with a UV spectrometer (wavelength 380 nm, 1 cm cell).
The value obtained by subtracting the value of T% from 100 is defined as clay dispersibility (turbidity).

<Calcium ion scavenging ability>
1) Prepare a standard calcium ion solution.

0.01 mol / L calcium ion aqueous solution: a solution obtained by dissolving 1.4701 g of calcium chloride dihydrate in 1 kg of ion exchange water 0.001 mol / L calcium ion aqueous solution: ion exchange water to 100 g of the above 0.01 mol / L calcium ion aqueous solution Added to make 1 kg 0.0001 mol / L calcium ion aqueous solution: 100 g obtained by adding ion-exchanged water to 10 g of the above 0.001 mol / L calcium ion aqueous solution
2) Into a 100 mL beaker, add 10 mg of the inorganic pigment dispersant and 50 g of 0.001 mol / L calcium ion aqueous solution in terms of solid content.
3) Stir 50 g of each aqueous solution of 1) and the aqueous solution of 2) with a magnetic stirrer.
4) Add 4.8 wt% NaOH aqueous solution to each aqueous solution of 3) so that the pH is 9-11.
5) Add 1 mL of 4M-KCl aqueous solution to each aqueous solution of 4).
6) Using an Orion ion analyzer EA920, measure the amount of calcium ions with an Orion calcium ion electrode 93-20.
7) Measure the amount of calcium ions captured by the dispersant for inorganic pigment from the calibration curve, express the amount captured per gram of the solid content of the dispersant in mg in terms of calcium carbonate, and use that value as the calcium ion scavengeability. .

Production Example 1
A reaction vessel equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet tube, and dropping funnel was charged with 49.0 g of maleic anhydride and 54.3 g of ion-exchanged water, heated to 75 ° C., and then a 30 wt% NaOH aqueous solution. 133.3g was dripped and it was set as the maleic-acid sodium salt aqueous solution. Next, after heating to 100 ° C. under a nitrogen stream, while maintaining this temperature, 225.3 g of 80 wt% acrylic acid aqueous solution and 109.3 g of 35 wt% aqueous hydrogen peroxide solution were respectively added from another dropping funnel over 3 hours. The solution was added dropwise to carry out a polymerization reaction. After completion of the dropping, the mixture was aged at 100 ° C. for 7 hours to complete the polymerization reaction. After completion of the reaction, the reaction mixture was cooled and neutralized with a 30 wt% NaOH aqueous solution so as to have a pH of 6 to 8 while maintaining about 60 ° C. to obtain a sodium salt of an acrylic acid-maleic acid copolymer. This is called copolymer A1.

Production Example 2
Using monomers shown in Table 1, copolymers A2 to A13 were obtained in the same manner as in Production Example 1.

  Table 1 shows the monomer composition, weight average molecular weight (Mw), number average molecular weight (Mn), and Mw / Mn of the copolymers A1 to A13 obtained in Production Examples 1 and 2. The copolymers A1 to A8, A10, A11 and A13 are the component (A) of the present invention.

Production Example 3
A reaction vessel equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet tube, and dropping funnel was charged with 149.6 g of maleic anhydride and 261.8 g of ion-exchanged water, heated to 75 ° C., and then 30% by weight NaOH aqueous solution. 231.4g was dripped and it was set as the maleic acid Na salt aqueous solution. Next, after heating to 100 ° C. under a nitrogen stream, while maintaining this temperature, 172.1 g of 80 wt% aqueous acrylic acid solution and 30.3 g of 35 wt% aqueous hydrogen peroxide solution were respectively added from another dropping funnel over 3 hours. The solution was added dropwise to carry out a polymerization reaction. After completion of the dropwise addition, the mixture was aged at 100 ° C. for 7 hours to complete the polymerization reaction. After completion of the reaction, the reaction mixture was cooled and neutralized with a 30 wt% NaOH aqueous solution so as to have a pH of 6 to 8 while maintaining about 60 ° C. to obtain a sodium salt of an acrylic acid-maleic acid copolymer. This is called copolymer B1.

Production Example 4
Using monomers shown in Table 2, copolymers B2 to B13 were obtained in the same manner as in Production Example 3.

  Table 2 shows the monomer composition, weight average molecular weight (Mw), number average molecular weight (Mn), and Mw / Mn of the copolymers B1 to B13 obtained in Production Examples 3 to 4. The copolymers B1 to B9 and B13 are the component (B) of the present invention.

Example 1
Copolymers A1 to A13 and Copolymers B1 to B13 obtained in Production Examples were blended in the ratios shown in Table 3 to obtain dispersants 1 to 8 and comparative dispersants 1 to 6 of the present invention.

  Table 3 shows the clay dispersibility in the presence of calcium ions or magnesium ions and the calcium ion scavengeability of the obtained dispersant.

Example 2
Disposable beaker 300 mL, titanium oxide 148 g with an average particle size of 0.4 μm, and ion-exchanged water and dispersant 1-8 or comparative dispersant 1-6 (100 parts by weight of titanium oxide) so that the slurry concentration becomes 75% by weight. 1 part by weight) was added, and the mixture was stirred (2500 rpm × 2 minutes) with a homodisper manufactured by Tokushu Kika Kogyo Co., Ltd. to prepare a slurry (pigment dispersion composition). The obtained slurry was measured for B viscosity at 25 ° C. using a B-type viscometer manufactured by Tokyo Keiki Co., Ltd. at a rotor rotational speed of 6 rpm and 60 rpm after 1 minute. Further, the TI value was calculated from the obtained viscosity value. The results are shown in Table 4. In the examples, the values of the slurry viscosity when measured at a rotor rotational speed of 6 rpm and 60 rpm are both low, and the TI value is 3 or less, indicating that a good pigment dispersion composition is obtained.

Claims (5)

A dispersant for inorganic pigment containing the following component (A) and component (B) in a ratio of (A) / (B) = 50/50 to 96/4 (weight ratio), wherein component (A) And the number average molecular weight (Mn) of (B) component is 20000-40000, respectively, and the dispersing agent for inorganic pigments which is Mw / Mn <= 3 .
(A) component:
An unsaturated monobasic acid having a constituent monomer unit ratio of unsaturated monobasic acid / unsaturated dibasic acid (molar ratio) = 91/9 to 74/26 and a weight average molecular weight (Mw) of 25,000 to 60,000 Salt (B) component of copolymer with unsaturated dibasic acid:
An unsaturated monobasic acid having a constituent monomer unit ratio of unsaturated monobasic acid / unsaturated dibasic acid (molar ratio) = 63/37 to 47/53 and a weight average molecular weight (Mw) of 25,000 to 60,000 Salts of copolymers with unsaturated dibasic acids The clay dispersibility in the presence of 80 mg / L of calcium ions is 15% or more and less than 50%, the clay dispersibility in the presence of 21 mg / L of magnesium ions is 46% or more and less than 60%, and the calcium ion scavenging ability is 270 mgCaCO ₃ / g or more 380mgCaCO ₃ / inorganic pigment dispersant of claim 1 Symbol placement than a is g. The inorganic pigment dispersant according to claim 1 or 2, wherein the unsaturated monobasic acid is at least one selected from acrylic acid and methacrylic acid. The dispersant for inorganic pigments according to any one of claims 1 to 3, wherein the unsaturated dibasic acid is at least one selected from maleic anhydride, maleic acid and itaconic acid. The pigment dispersion composition containing the dispersing agent for inorganic pigments in any one of Claims 1-4 .