COLOURING AND FILLER PASTES USING INORGANIC PARTICLES WITH COATED SURFACE AS A SPACER

Abstract

A liquid or pasty pigment and/or filler preparation comprising: 1 to 70% by weight of at least one pigment dispersed in the preparation and/or at least one filler dispersed in the preparation (component (A)), 1 to 25% by weight of at least one inorganic, particulate component dispersed in the preparation, as component (B), 0 to 10% by weight of at least one surface-active wetting agent, which preferably also has dispersing properties, and as the remainder water and/or at least one solvent, the particles of component (B) being nanoscale or microscale and being inorganically or organically surface-modified, the surface modifier used being selected such that component (B) has a cationic, anionic, amphoteric or non-ionic surface, and component (B) further has a zeta potential which is opposite to the charge of the particles of component (A) or, in the case of uncharged particles of component (A), has a zeta potential in the range of −60 to +40 mV so as to effect adhesion of the particles (B) to the pigment and/or filler surface. The liquid pigment and/or filler preparations are excellently suited for the production of a wide variety of varnishes and paints for various applications, but also for the colouration of plastics, for example.

Claims

1. A liquid or pasty pigment and/or filler preparation comprising 1 to 70% by weight of at least one pigment dispersed in the preparation and/or at least one filler dispersed in the preparation, as component (A), 1 to 25% by weight of at least one inorganic particulate component dispersed in the preparation, as component (B), 0 to 10% by weight of at least one surface-active wetting agent, preferably also having dispersing properties, and water and/or at least one solvent, wherein the particles of component (B) are nanoscale or microscale and are inorganically or organically surface-modified, the surface modifier used being selected such that component (B) has a cationic, anionic, amphoteric or non-ionic surface, and component (B) further has a zeta potential opposite to the charge of the particles of component (A) or, in the case of uncharged particles of component (A), has a zeta potential in the range of −60 to +40 mV so as to cause adhesion of the particles (B) to the pigment and/or filler surface.

2. The pigment and/or filler preparation according to claim 1, wherein the inorganic core of the particles of component (B) is selected from the group consisting of barium sulphate, calcium carbonate, titanium dioxide, silicon dioxide and any mixtures thereof.

3. The pigment and/or filler preparation according to claim 1, wherein the particles of the dispersed component (B) have a particle size distribution with a d50 value in the range of 10 to 500 nm.

4. The pigment and/or filler preparation according to claim 3, wherein the particles of the dispersed component (B) have a particle size distribution with a d50 value in the range of 20 to 300 nm.

5. The pigment and/or filler preparation according to claim 3, wherein the particles of the dispersed component (B) have a particle size distribution with a d50 value in the range of 25 to 200 nm.

6. The pigment and/or filler preparation according to claim 1, wherein the particles of component (B) are surface-modified with at least one organic compound.

7. The pigment and/or filler preparation according to claim 6, wherein the organic compound for surface modification is selected from the group consisting of anionic, cationic, non-ionic, amphoteric or multifunctional molecules or polymers.

8. The pigment and/or filler preparation according to claim 7, wherein the organic compound for surface modification is a comb polymer-based surface modifier.

9. The pigment and/or filler preparation according to claim 8, wherein the comb polymer comprises or has a polyacrylate main chain and PEG side chains.

10. The pigment and/or filler preparation according to claim 9, wherein the comb polymer comprises or has the PED side chains, and the PEG side chains have a number average molecular weight Mn in the range of 500 to 6,000 g/mol.

11. The pigment and/or filler preparation according to claim 1, wherein the mass fraction of the surface modifier, based on the inorganic core of component (B) is 0.1 to 50%.

12. The pigment and/or filler preparation according to claim 1, wherein the mass fraction of the surface modifier, based on the inorganic core of component (B) is 0.2 to 10%.

13. The pigment and/or filler preparation according to claim 11, wherein the inorganic core is or comprises barium sulphate.

14. The pigment and/or filler preparation according to claim 1, wherein, if the component (A) has a positive surface charge, the zeta potential of the component (B) is in the range of −60 mV to −3 mV, and wherein, if the component (A) has a negative surface charge, the zeta potential of the component (B) is in the range of +1 mV to +40 mV.

15. The pigment and/or filler preparation according to claim 1, wherein if a non-polar pigment or filler is used, an additional wetting agent is used.

16. The pigment and/or filler preparation according to claim 15, wherein the wetting agent is an amphiphilic molecular or polymeric wetting agent and/or is an anionic or cationic wetting agent with pigment-wetting properties.

17. The pigment and/or filler preparation according to claim 1, wherein the preparation further comprises at least one dispersing agent.

18. The pigment and/or filler preparation according to claim 17, wherein the dispersing agent or more dispersing agents are comprised in an amount of 1 to 10% by weight.

19. The pigment and/or filler preparation according to claim 17 , wherein the dispersing agent is selected from the group consisting of polyvinyl copolymers, polyvinyl copolymers with pigment affine groups, ethoxylated alcohols, dimethylethanolamine and any mixtures thereof.

20. The pigment and/or filler preparation according to claim 1 , wherein the preparation further comprises at least one surfactant, the one or more surfactants being present in an amount of 0.1 to 2% by weight.

21. A process for preparing a pigment and/or filler preparation according to claim 1, which process comprises the following steps: a. presenting a dispersion of the surface-modified particles (component B) in the mill base, b. homogenizing the pigment and/or filler by dispersing.

22. A paint or varnish comprising the liquid or pasty pigment or filler preparation according to claim 1.

23. The paint or varnish according to claim 22, wherein the liquid or pasty pigment or filler preparation is comprised in a proportion in the range of 1-30% by weight, based on the total composition (in the case of pigment preparations), or 1-70% by weight, based on the total composition (in the case of filler preparations).

24. The paint according to claim 22, selected from the group consisting of emulsion paints, architectural decorative paints, coat of paints and printing inks.

25. The varnish according to claim 22, wherein the varnish is an automotive varnish or a varnish for coil coating.

26. A method for stabilizing a liquid or pasty pigment and/or filler preparation by avoiding or reducing the agglomeration of the pigment and/or filler particles, the method comprising dispersing the pigment and/or filler particles as component (A) in a nanoscale or microscale inorganic particulate as component (B), wherein the component (B) has a cationic, anionic, amphoteric or non-ionic surface, and the component (B) in the pigment and/or filler preparation further has a zeta potential which is opposite to the charge of the pigment and/or filler particles of component (A).

27. The method according to claim 26, wherein in the case that the pigment and/or filler particles have a positive surface charge, the zeta potential of the component (B) is in the range of −60 mV to −3 mV, and wherein in the case that the pigment and/or filler particles have a negative surface charge, the zeta potential of the component (B) is in the range of +1 mV to +10 mV.

28. The method according to claim 26, wherein the inorganic particulate component (B) is inorganically or organically surface-modified.

29. The method according to claim 28, wherein the surface modifier is or comprises an organic compound as specified in claim 6.

30. The pigment and/or filler preparation according to claim 2, wherein the core of the particles of component (B) comprises barium sulphate or the core is a barium sulphate particle.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0168] FIG. 1: FIG. 1 shows the principles of electrostatic (FIG. 1A), steric (FIG. 1B) and electrosteric (FIG. 1C) stabilization.

[0169] FIG. 2: FIG. 2 shows a structure of component (B), in this case barium sulphate, and a pigment component (A). In FIG. 2A the structure for a pigment with positive surface charge is shown, in FIG. 2B for a pigment with negative surface charge. FIG. 2C is an enlarged view of FIG. 2A, and FIG. 2D is an enlarged view of FIG. 2B.

[0170] FIG. 3: FIG. 3 compares the normalized size distribution of barium sulphate dispersions. A dispersion produced according to the MJR technology used in the invention (left curve) is characterized by a smaller particle size and a narrower size distribution. Conventionally ground and dispersed barium sulphate (right curve) consists of larger particles and is characterized by a broader size distribution.

[0171] FIG. 4: FIG. 4 shows the combination of a negatively charged particle (here barium sulphate) with an amphiphilic wetting agent for pigment stabilization.

[0172] FIG. 5: FIG. 5 is a schematic illustration of an MJR process according to the invention for producing the particulate component (B).

EXAMPLES

Example 1: Preparation of a Surface-Modified Barium Sulphate Dispersion

[0173] A process for producing a low-viscosity aqueous, surface-modified barium sulphate dispersion for a pigment and/or filler preparation according to the invention at room temperature comprises the following steps:

[0174] a) Providing a barium salt solution (halide, nitrate or carboxylate).

[0175] b) Providing an alkali sulphate solution.

[0176] c) Providing at least one comb polymer with a specific charge of −10 C/g to −500 C/g at pH 8.

[0177] d) Mixing the barium salt solution from step a) with the comb polymer from step c) in an amount of preferably 0.5 to 20%, preferably 1 to 10% and most preferably 3 to 8% relative to the solid product.

[0178] e) Precipitating barium sulphate by mixing liquid streams from steps b) and d) in flow through a micro-reactor, preferably a microjet reactor, where the product is discharged by a carrier gas flow.

[0179] At the flow/collision point of the microreactor, in which the product is discharged by a carrier gas stream (nitrogen flow: 1,000 cm.sup.3/min), the alkali sulphate solution (for example sodium sulphate solution) and the barium salt solution (for example barium chloride solution) react with each other in the form of stirred aqueous solutions in a molar ratio of 1.0:1.05. The barium chloride solution has a density of 1.043 g/ml and comprises 3% of a polycarboxylate ether, for example Melpers 2454, based on the theoretical yield of barium sulphate. The comb polymer Melpers 2454 inter alia beneficially effects the stabilisation of the obtained BaSO4 particles with regard to growth and agglomeration. The white dispersion thus obtained can be purified by ultrafiltration until an electrical conductivity of 1,000 μS/cm is achieved and is a low-viscosity aqueous barium sulphate dispersion which can be concentrated to up to 50% by ultrafiltration.

Example 2: Preparation of a Surface-Modified Barium Sulphate Dispersion Based on Ba(OH).SUB.2.×8 H.SUB.2.O

[0180] Another process for producing a surface-modified barium sulphate dispersion for a pigment and/or filler preparation according to the invention at room temperature is based on the reaction Ba(OH).sub.2+H.sub.2SO.sub.4.fwdarw.BaSO.sub.4+2 H.sub.2O and comprises the following steps:

[0181] a) Providing a solution of 157 g Melpers 0045 dissolved in 843 g of deionized water.

[0182] b) Suspending 1577 g Ba(OH).sub.2×8 H.sub.2O in the solution of step a) under stirring.

[0183] c) Providing a 5 M sulfuric acid solution.

[0184] d) Precipitating barium sulphate by mixing liquid streams from steps b) and c) in flow through a micro-reactor, preferably a microjet reactor.

[0185] e) Discharging the thus obtained barium sulphate dispersion

[0186] The suspension of step b) is continuously pumped through the upper entrance (opening 3) of a reaction chamber. In the middle of the reaction chamber, the diluted 5M sulfuric acid solution is added continuously via two ruby nozzles with a diameter of 100 μm into the Ba(OH).sub.2 stream to form BaSO.sub.4 and water. During addition the molar ratio of Ba(OH).sub.2 to H.sub.2SO.sub.4 is kept at 1:0.95. The resulting colloidal dispersion has a barium sulphate content of 34.97% (m/m) (the theoretically obtainable value is 36%) and a particle size of 170 nm (DLS, z-Average).

[0187] The advantages in comparison to a BaC12-based route are: [0188] no sodium chloride formation within the precipitation process; [0189] high initial solid contents up to 35%; [0190] no subsequent X-flow filtration; [0191] no waste water production; [0192] no waste water post-treatment; and v no water disposure.

Example 3: Preparation of a Pigment Preparation According to the Invention

[0193] All components of the preparation except for the pigment (Printex U) are presented in the ground stock (Table 1). Afterwards, the pigment is added to the ground stock over a period of 5 min via a rotor-stator system (Miccra D-13, 14,000 rpm) and dispersed. Post-homogenization for a further 5 min at 14,000 rpm provides a flowable pigment formulation (outlet cup 32 s, nozzle 3 mm, DIN EN ISO 2431). The resulting dispersion has a negative zeta potential (−25 mV) and a d50 value of 1.1 μm (d10=0.63 μm, d90=1.67 μm).

[0194] The composition of the preparation is as follows: [0195] 13.20% by mass nanoscale BaSO4 according to example 1 or example 2 [0196] 59.85% by mass water [0197] 0.20% by mass Ebotec MT15SF [0198] 0.30% by mass Dimethylethanolamine 50% [0199] 4.75% by mass Zetasperse® 3700 [0200] 21.30% by mass Printex U [0201] 0.40% by mass Surfynol 104 E

[0202] The dispersing agents Zetasperse 3700 and dimethylethanolamine can be added to the dispersing medium at the same time as the pigment Printex U, or they can be mixed with it in advance.

[0203] Due to the advantageous properties of the nanoscale barium sulphate, the necessary proportion of dispersing agents can be significantly reduced or dispensed with altogether.

Example 4: Zeta Potentials

[0204] The zeta potentials of a dispersion of particulate, surface-coated barium sulphate were determined in an aqueous medium in the presence of various agents. The surface coated barium sulphate particles were modified with 1% of the respective agent and the zeta potentials were determined by electrophoretic light scattering according to ISO 13099-2: 2012.

[0205] The zeta potential was measured using a Zetasizer Nano ZS90 from Malvern Instruments Ltd., Herrenberg. By applying an alternating electric field and the resulting movement of charged particles in dispersion, the speed of movement of the particles in the electric field is measured by interferrometric laser technology. This in turn allows the calculation of the electrophoretic mobility and the resulting zeta potential by the implemented software Zetasizer Ver. 7.11. Standard zeta cuvettes were used for the measurement. In all cases the measurement was temperature controlled at 25° C.

[0206] Sample preparation: To measure the zeta potential, 0.82 g of a 24.31% by weight aqueous surface coated barium sulphate dispersion with a conductivity <1 mS were added to 40 g of a 1% by weight agent solution (based on active content) and mixed for 30 secs. 1 mL of the sample is transferred bubble-free into a standard zeta cuvette, transferred to the measuring instrument and measured quickly after reaching thermal equilibrium.

[0207] The results are summarized in Table 1:

TABLE-US-00001 Zeta Potential of the Surface coated BaSO.sub.4 dispersion Modifying Agent [mV] Efka FA 4671 −59.9 Disperbyk 2010 −37.3 Dispers 757W −20.4 Metolat 514 −18.7 Zetasperse 3600 −17.9 Dispex Ultra PX 4525 −13.9 Edaplan 494 −12.6 Disperbyk 2060 −12.0 Zetasperse 3700 −11.9 Dispex Ultra PX 4275 −11.8 Disperbyk 180 −10.8 Dispex CX 4320 −10.6 Edaplan 490 −10.5 Edaplan 516 −7.61 Tego Dispers 755W −4.57 Disperbyk 191 −3.3 Dispex Ultra FA 4420 −3 Tego Dispers 760W −2.56 Disperbyk 184 1.05 Byk LP N 22669 2.58 Efka WE 3110 3.96 Carbowet GA 211 4.4 Carbowet 221 4.72 Dispex Ultra FA 4480 5.77 Disperbyk 192 6.37 Dispersogen PCE 8.05 Disperbyk 182 10.1 Dispex Ultra PX 4575 14.9 Dispex Ultra FA 4425 17.4