COMPOSITE CARBON BLACK PARTICLES

Abstract

Suggested is a composite particle comprising or consisting of a solid core partially or entirely coated with at least one inorganic compound, wherein (a) said solid core is a carbon black particle carrying functional groups on its surface, and (b) said at least one inorganic compound shows a particle size of from about 5 to about 100 nm, wherein said solid core particles show a diameter of primary particle size from about 5 to about 500 nm.

Claims

1. A composite particle comprising or consisting of a solid core partially or entirely coated with at least one inorganic compound, wherein (a) said solid core is a carbon black particle carrying functional groups on its surface, and (b) said at least one inorganic compound shows a particle size of from about 5 to about 100 nm, wherein said solid core particles show a diameter of primary particle size from about 5 to about 500 nm.

2. The composite particles of claim 1, wherein said carbon represents black furnace black, gas black, thermal black , lamp black , carbon fiber, carbon plates, activated carbon, vitreous carbon, charcoal, graphite and mixtures thereof.

3. The composite particles of claim 1, wherein said functional groups are selected from hydroxyl, carboxyl, anhydride, sulfate, sulfonate, phosphate, phosphonate, nitrate, carboxylate, acetate and mixtures thereof.

4. The composite particles of claim 1, wherein said carbon black includes self-dispersed pigments and/or polymer dispersed pigments.

5. The composite particle of claim 1, wherein said carbon black core particles show a diameter of primary particle size from about 5 to about 500 nm.

6. The composite particle of claim 1, wherein said inorganic compounds represent alkaline earth salts.

7. The composite particle of claim 1, wherein said inorganic compound is barium sulfate

8. The composite particle of claim 1, wherein said inorganic compound represents a mixture of an alkaline earth sulfate and a second inorganic salt selected from sulfates, carbonate, nitrates, carboxylates or oxides of metals of the second main group of the periodic system.

9. The composite particle of claim 1, wherein said inorganic compounds optionally after treatment with an organic surface modifying agent shows a surface charge of from about −30 to about +30 mV.

10. The composite particle of claim 1, wherein the amount of inorganic compounds is at least 50 wt.-percent—calculated on the composite particle.

11. A process for preparing the composite particles of claim 1, comprising or consisting of the following steps: (a) providing a first dispersion comprising carbon black particles carrying functional groups on its surface in a solvent; (b) providing a second dispersion comprising at least one inorganic compound in a solvent; (c) blending the first and the second dispersion to achieve a homogenous mixture; and optionally (d) removing the solvent from the mixture; and (e) collecting the composite particles.

12. The process of claim 10, wherein the solvent is water or a C.sub.1-C.sub.4 aliphatic alcohol or a mixture thereof.

13. The process of claim 11 wherein the mixture of step (d) is subjected to a drying operation.

14. A water-borne formulation comprising (a) a polyurethane or polyacrylic resin and (b) the composite carbon black particles of claim 1.

15. The use of the composite particles of claim 1 as black pigments.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0075] FIG. 1 is a schematic flowchart explaining the process of an encapsulated carbon black according to the present invention in water phase, and solvent conversion and a spraydrying process for the purpose of composite particles creation on the way of solvent borne phase or solid form.

[0076] FIG. 2 is a schematic chart explaining the process of an encapsulated carbon black according to the present invention in solvent phase, and final with solvent conversion and a spray-drying process for the purpose of composite particles creation on the way of another solvent borne phase or solid form.

[0077] FIG. 3a shows aggregate size distribution curves using DCP device for before and after encapsulation as dispersion form under different ratio of carbon black to BaSO.sub.4.

[0078] FIG. 3b shows aggregate size distribution curves using DCP device for before and after encapsulation as PWD form under ratio of carbon black to BaSO.sub.4of 0.5:1.

[0079] FIG. 4a shows a group TGA for comparative reference carbon black sample and different carbon black composites particles under different ratio of carbon black to BaSO.sub.4 by weight.

[0080] FIG. 4b shows TGA for comparative reference carbon black sample, one oven dried carbon black composites and one spray dried carbon black composite particles,

[0081] FIGS. 5 to 8 show typical Transmission Electron Micrograph (TEM) images of pure carbon black particles and pure BaSO.sub.4 particles (5, 6) and composite particles (7,8).

[0082] FIG. 9 particles distribution by volume diffusion using DLS device manufactured by Horiba LA960 for before and after encapsulation of BaSO.sub.4 particle from comparative reference carbon black VDP CB1 (0.5:1).

[0083] FIG. 10a,b show that the zeta potential is deionized water of the comparative reference carbon black VDP CB1 is −56.6 mV and that the zeta potential of encapsulated sample (0.5:1) in deionized water is −19.3 mV.

[0084] FIG. 11a,b show that paints evaluation results on coloristic, gloss and surface resistivity under different ratio by solid to solid of carbon black to resin by 10%, 15%,20%, 30% and 40% for comparative reference carbon black and the encapsulated samples with various size of BaSO.sub.4 under 2 ratios.

EXAMPLES

Example 1a

Preparation of a Mill Base From Solid Carbon Black in Water

[0085] A modified carbon black pigment as set out in Table 1 was used for preparing a 30% dispersion according to the following procedure: [0086] 1) 4,104 grams of de-ionized water and 95 grams of AMP95 were filled into a MoFa vessel and mixed under a stirring condition as described below. [0087] 2) The mixture was stirred for 2 minutes (jet mixer: 300 rpm; anchor stirrer; 30 rpm; Conti dispersing unit: 600 rpm). [0088] 3) The temperature was monitored and the speed of the Conti TDS increased to 2500-3000 rpm. [0089] 4) The powder funnel valve was carefully and 1,800 grams of the modified carbon added. After addition was completed the speed of the Conti TDS was raised to 4,000 rpm, and the mixture dispersed until a temperature of 45° C. was reached. [0090] 5) The speed of Conti TDS was reduced to 600 rpm and the dispersion cooled to about 30° C. [0091] 6) The quality of the dispersion was monitored by light microscope picture to decide, whether another dispersing step is necessary.

[0092] 7) Subsequently, the dispersion was moved to a Bühler PML 2 bead mill using 210 mL (means ˜80% of chamber volume) zircon oxide beads, size 0.3 mm. [0093] 8) The dispersion was treated at 100 kWh/t.

TABLE-US-00001 TABLE 1 Analytical properties of carbon black Properties carbon black sample OAN (cc/100 g) 130 Nitrogen surface area(m.sup.2/g) 98 STSA surface area(m.sup.2/g) 78 Tint (%) 105 pH 2.4 Volatile (%) 12 Ash content (%) 0.01 D.sub.mode (nm) 75

Example 1b

Preparation of a BaSO.SUB.4 .Colloid Dispersion in Water

[0094] Aqueous solutions of Barium Chloride and Sodium Sulfate were subjected to a high jet stream velocity (up to 300 m/s) via MJR® to form Barium Sulfate. The ratio of the reactants was monitored in the presence of a surface modifier. The particles thus obtained ranged from 10 to 60 nm. Sodium chloride was separated off by electrodialysis, followed by a concentration step. Dispersions of Barium Sulfate particles with different sizes were obtained.

Example 1c

Preparation of Encapsulated Particles in Water

[0095] The composite particles were obtained by blending the carbon black dispersion of Example 1a with barium sulfate dispersion according to Example 1b by using high speed homogenization (e.g. Ultra-Turrax), MJR® or other devices like high dissolver, vortex mixer and the like. Composite particles are obtained comprising weight ratios of carbon black versus the pure BaSO.sub.4 ranging from 0.1:1 to 10:1.

Example 1d

Drying the Dispersion Comprising Composite Particles

[0096] The composite particles were obtained by blending the carbon black dispersion of Example 1a with barium sulfate dispersion according to Example 1b by using high speed homogenization (e.g. Ultra-Turrax), MJR® or other devices like high dissolver, vortex mixer and the like. Composite particles are obtained comprising weight ratios of carbon black versus the pure BaSO.sub.4 ranging from 0.1:1 to 10:1.

The encapsulated carbon black dispersion Example 1c are subsequently spray dried (Büchi 190 Mini Spray Dryer, nozzle aperture 0.5 mm) .The dispersion is transported to the spraying nozzle by means of peristatic pump and drying takes place at an entry of entry temperature of 200° C. and an exit of temperature of 80° C. The powder was deposited via a cyclone.

Example 2a

Preparation of a Mill Base in Ethanol

[0097] An aqueous solution of Jeffamine was added to a 30% carbon black dispersion prepared from example 1a. The mixture was subjected twice to a centrifugation step to remove unreacted amine. Ethanol was added to re-disperse the particles.

Example 2b

Preparation of BaSO.SUB.4 .Colloid Dispersions in Ethanol

[0098] The dispersion prepared according to Example 1b was subjected to another centrifugation step in order to remove the majority of water. The residue was re-dispersed in ethanol and again subjected to centrifugation in order to eliminate the last portion of water. Finally, more ethanol was added to obtain a stable alcoholic dispersion.

Example 2c

Preparation of Encapsulated Particles in Ethanol

[0099] The composite particles were obtained by blending the carbon black dispersion of Example 2a with barium sulfate dispersion according to Example 2b by using high speed homogenization (e.g. Ultra-Turrax), MJR® or other devices like high dissolver, vortex mixer and the like. Composite particles are obtained comprising weight ratios of carbon black versus the pure BaSO.sub.4 ranging from 0.1:1 to 10:1.

Example 3

Water-Borne Polyurethane Coatings

[0100] This example discloses paint formulations using the composite particles according to Examples 1 and 2 with regard to blackness, bluish undertone, gloss and surface resistivity of cured paint film applied on the glass in contrast to the comparative reference carbon black at 2 different temperatures profiles.

[0101] Let-down various dispersions with encapsulated composite particles using high-disperser in polyurethane based compositions shown at the below table under different CB-to- binder solid concentrations with 10%, 15%, 20%, 30% and 40% CB concentration on binder solid. No intensive mixing or dispersion was required for the paint preparation. The respective coating composition was applied onto a glass plate (130×90×1 mm) and drawn down with a film drawing bar having a slot height of 200 μm, flashed off at room temperature (20° C.) for 15 min and then dried at 60° C. for 15 min.

[0102] Coloristic characteristics of the thus obtained films prepared were measured using a Pausch Q—Color 35 spectrophotometer (45°/0° spectrophotometer) and the BCSWIN software. The measurement is made through the glass after calibration with a white calibration tile and a black hollow body. The spectrometer averages over five individual measurements for each sample; gloss was determined using Gloss-Meter by manufactured by Byk Gardner and surface resistivity using Milli- and Teraohmmeter Fischer Elektronik—High ohmic measurement device with protective ring electrode FE25 at 23° C.

[0103] After measurements of paints the specimen were cured at 60° C., followed by additional curing of paints draw-down for 30 min at 230° C. Subsequently, the measurements on coloristic, gloss and surface resistivity were conducted according to the same aforementioned methods. The paint compositions are given in Table 2.

TABLE-US-00002 TABLE 2 Paints composition Components Amount [g] Alberdingk U9800 1137.0 Butyl glycol 195.0 Water deionized 150.0 BYK 024 9.0 Tego Wet 280 6.0 DMEA 3.0
The amount of carbon black that was added to the above paint formulation has been 10%, 15% 20%, 30% and 40% respectively-calculated on solid to Alberdingk U9800.

Percolation Curve

[0104] The carbon black of Comparative Example A and Example C1 were used to prepare mill bases, letdowns, and coatings according to the procedures described above and containing 10%, 15%, 20%, 30%, 40% carbon black by weight on a solid to solid of resin, and correlated to a weight ratio of total paint weight respectively by 2.3%, 3.3%, 4.1%, 5.2% and 6.2%. The surface resistivity of the coatings was measured as above and is illustrated in FIG. 11. FIG. 11 shows that, using the invented composite particle, at the same loading levels a higher resistivity before and after 230° C. baking can be achieved compared to the comparative reference sample VDP.

Example 4

Preparation of Solvent-Borne Coating Composition

[0105] The carbon black of Comparative Example A and Example 1d were used to prepare organic solvent-borne dispersions:

[0106] A Skandex dispersing beaker (180 mL, diameter 5.3 cm, height 12.5 cm) was charged with Degalan® VP 4157L and butyl acetate in a weight ratio of 60.3:22.5, and the carbon black of Comparative Example A and Example 1d were stirred in with a spatula. Subsequently, the products were dispersed using a Pendraulik LR 34 dissolver at 4,000 rpm for 30 min by means of a dispersing disc having a diameter of 40 mm. The ratio of the organic solvents to the solid pigment preparation was selected so as to give a concentration of 13.6 wt.-percent of pigment or pigment composite particles in the resulting solvent-borne dispersion.

[0107] Preparation of solvent-borne coating compositions: Solvent-based coating compositions were prepared from the thus obtained solvent-borne dispersions prepared according to the following formulation: (Table 3):

TABLE-US-00003 TABLE 3 Formulation of the solvent-borne coating compositions: Amount Component [g] Degalan ® VP 4157L 9.5 Dispersion from solid pigment preparation (Example 1-9) 5.3 2K diluent (89.9% butyl acetate, 10.0% butyl glycol 4.0 acetate, 0.1% Baysilone ® OL 17) Vestanat ® HB 2640 MX 1.2 Total 20 Pigment concentration (total) 2.2

[0108] The components were weight in the indicated amounts into an 80 mL beaker and homogenized vigorously with a spatula for 10 min to yield the corresponding solvent-borne coating composition.

[0109] Preparation of films from the coating compositions: The respective coating composition was applied onto a glass plate (130×90×1 mm) and drawn down with a film drawing bar having a slot height of 100 μm, wet, with uniform tension and pressure. Care was taken to ensure that there were no air bubbles in the stripe of the coating composition. The film drawing bar was placed over the stripe of the coating composition and drawn uniformly across the plate. A drawdown is produced which is approximately 10 cm long and 6 cm wide. After the drawdown procedure, the obtained wet coating film on the glass plate was flashed off at room temperature (20° C.) and then the coated glass plate dried at 80° C. for 30 min.

[0110] For determining the color characteristics of the particles a Pausch Q—Color 35 spectrophotometer (4570° spectrophotometer) and the BCSWIN software was used. The measurement was made through the glass after calibration with a white calibration tile and a black hollow body. The spectrometer averages over five individual measurements for each sample. The results are shown in Table 4:

TABLE-US-00004 TABLE 4 Color measurements is in accordance with the aforementioned procedure Comparative Inventive Color characterization Example A Example 1d Color through glass 237 253 Color direct 237 251 Blueish tone through glass −0.3 2.7 Blueish tone direct 0.5 3.1

[0111] The examples show that the particles according to the invention provide both a darker color and a more intensive blueish tone.