Method For Producing Anisotropic Zinc Phosphate Particles And Zinc Metal Mixed Phosphate Particles And Use Thereof

Abstract

Anisotropic zinc phosphate particles and zinc metal mixed phosphate particles having an orthorhombic crystal structure and a platelet-shaped particle morphology are obtained from a composition comprising at least one phosphate compound; at least one zinc compound and at least one chelate complexing agent having at least two oxygen-containing groups and at least one solvent.

Claims

1. A method for producing anisotropic zinc phosphate particles or zinc metal mixed phosphate particles comprising the steps of: a) producing a composition comprising at least one phosphate compound; at least one zinc compound and at least one chelate complexing agent having at least two oxygen-containing groups and at least one solvent, b) forming anisotropic zinc phosphate particles or zinc metal mixed phosphate particles; and c) separating off the particles obtained.

2. The method as claimed in claim 1, characterized in that wherein step b) is effected at a temperature below 50° C.

3. The method as claimed claim 1, wherein the Zn content of an aqueous composition is above 0.5 wt % based on Zn.sup.2+.

4. The method as claimed in claim 1, wherein platelet-shaped particles are obtained.

5. The method as claimed in claim 1, wherein platelets having an orthorhombic crystal structure are obtained.

6. The method as claimed in claim 1, wherein the composition has a pH below 3.5.

7. The method as claimed in claim 1, wherein the at least one phosphorus compound is phosphoric acid and/or an alkali metal salt of phosphoric acid.

8. The method as claimed in claim 1, wherein the at least one zinc compound is a zinc salt.

9. The method as claimed in claim 1, wherein the at least one chelate complexing agent is an organic acid having a pKa value <6.

10. The method as claimed in claim 1, wherein the at least two oxygen-containing groups are carboxylic acid groups, carboxylic anhydride groups, ether groups, ester groups, keto groups or hydroxyl groups.

11. The method as claimed in claim 1, wherein the at least one chelate complexing agent is α-hydroxycarboxylic acids, citric acid, malic acid, tartaric acid, ascorbic acid, mandelic acid, glyoxalic acid, malonic acid, lactic acid, acetic acid, fumaric acid, maleic acid, gluconic acid, phthalic acid or adipic acid.

12. The method as claimed in claim 1, wherein the composition comprising at least one zinc compound further comprises at least one further metal compound.

13. The method as claimed in claim 12, wherein the at least one further metal compound comprises compounds of manganese, magnesium, calcium, strontium, iron, cerium, aluminum, nickel or cobalt.

14. The method as claimed in claim 1, wherein the molar ratio of the at least one chelate complexing agent (CS) and the at least one zinc compound and optionally the further metal compound is in the range from 0.1/1 to 2.0/1.

15. The method as claimed in claim 1, wherein the molar ratio of the at least one zinc compound based on Zn ions and the optionally present metal compound to the admixed amount of the at least one phosphate compound based on P (Zn/P) is in the range from 0.8 to 1.8.

16. A zinc phosphate or zinc metal mixed phosphate particle obtained by a method as claimed claim 1.

17. The method of using particles as claimed in claim 16 as corrosion control pigment or as additive for dental cements or coatings.

18. A composite material comprising a polymer and particles as claimed in claim 16.

Description

[0072] The figures show results and measurements regarding the exemplary embodiments. The ratios recited in the figure descriptions are all molar ratios. Specifically

[0073] FIG. 1 shows a): diffractogram of Comparative Example 3: Zn/P=1.5 without citric acid as chelate complexing agent (CS) CS/Zn 0/1, H.sub.3PO.sub.4 (85 wt %), centrifuged 4×, diffractogram b): Example 2: Zn/P=1.5 with citric acid as chelate complexing agent (CS) CS/Zn 1/1, H.sub.3PO.sub.4 (85 wt %), centrifuged 4× (XRD spectrum of hopeite Zn.sub.3(PO.sub.4).sub.2*4H.sub.2O);

[0074] FIG. 2 shows dependence on centrifugation conditions, diffractograms a) Example 2: Zn/P=1.5; CS/Zn 1/1, H.sub.3PO.sub.4 (85 wt %), centrifuged 1×, diffractogram; b) Example 2: Zn/P=1.5, CS/Zn 1/1, H.sub.3PO.sub.4 (85 wt %), centrifuged 2×, (XRD spectrum of hopeite Zn.sub.3(PO.sub.4).sub.2*4H.sub.2O);

[0075] FIG. 3 shows a) diffractogram of Example 2a: CS/Zn 1/1, H.sub.3PO.sub.4 (30 wt %), centrifuged 4×; particle size: large: 2-3 μm; small 0.2-0.4 μm (XRD spectrum of hopeite Zn.sub.3(PO.sub.4).sub.2*4H.sub.2O); b) comparative diffractogram for hopeite;

[0076] FIG. 4 shows diffractogram of Example 4: Zn/P=1, CS/Zn=0/1, centrifuged 4×;

[0077] FIG. 5 shows diffractogram of Example 5: Zn/P=1, CS/Zn=0.1/1, centrifuged 4×;

[0078] FIG. 6 shows diffractogram of Example 6: Zn/P=1, CS/Zn=0.8/1, centrifuged 1×;

[0079] FIG. 7 shows diffractogram of Example 6: Zn/P=1, CS/Zn=0.8/1, centrifuged 2×;

[0080] FIG. 8 shows diffractogram of Example 6: Zn/P=1, CS/Zn=0.8/1, centrifuged 4×;

[0081] FIG. 9 shows schematic depiction of invention method;

[0082] FIG. 10 shows scanning electron micrographs of obtained particles in Examples 3, 3a, 2 and 2a; influence without chelate complexing agent (shapeless particles) and with chelate complexing agent (platelet-shaped particles);

[0083] FIG. 11 shows scanning electron micrographs of obtained particles with the ratio Zn/P 1.5 and also CS/Zn 0.66/1 and 1/1 in various resolutions with differently concentrated phosphoric acid H.sub.3PO.sub.4 each time (top: 85 wt % Examples 1b and 2; bottom: 30 wt % Example 2a);

[0084] FIG. 12 shows scanning electron micrographs for various ratios of CS/Zn and Zn/P on changing the concentration of the phosphoric acid (Zn compound Zn acetate with citric acid as CS);

[0085] FIG. 13 shows scanning electron micrographs of obtained particles with CS/Zn 0/1 and CS/Zn 1/1 at Zn/P 1.5, H.sub.3PO.sub.4 (85 wt %) on dropwise addition of phosphate solution into the zinc acetate/CS solution (CS: citric acid);

[0086] FIG. 14 shows scanning electron micrographs of obtained particles with CS/Zn 0/1 and CS/Zn 1/1 at Zn/P 1.5, H.sub.3PO.sub.4 (85 wt %) on single addition of phosphate solution into the zinc acetate/CS solution (citric acid); compared with FIG. 13, particle shape unaffected by addition mode;

[0087] FIG. 15 shows scanning electron micrographs of obtained particles in Examples 4, 5 and 6 with Zn nitrate and Na.sub.2HPO.sub.4 as starting compounds; Zn/P 1, Na.sub.2HPO.sub.4 (10 wt %), centrifuged 4×, increasing CS/Zn ratio;

[0088] FIG. 16 shows scanning electron micrographs of Example 6: Zn/P 1, CS/Zn 0.8/1, Na.sub.2HPO.sub.4 (10 wt %), the particles were centrifuged differently often;

[0089] FIG. 17 shows scanning electron micrograph experiments to test the effect of various types of chelate complexing agents; Zn/P 1, CS/Zn 0.8/1, Na.sub.2HPO.sub.4 (10 wt %): morphology as a function of complexing agent type, malic acid corresponds to Example 17;

[0090] FIG. 18 shows scanning electron micrographs of Examples 7, 8 and 9; Zn/P 1, CS/Zn 0.5/1, Na.sub.2HPO.sub.4 (10 wt %), DEG/H.sub.2O 0.25 to 16.9 (in wt %), addition of phosphate solution into zinc nitrate/CS solution;

[0091] FIG. 19 shows scanning electron micrographs of compositions Zn/P 1.5 with CS/Zn 0.5/1, Na.sub.2HPO.sub.4 (1 wt %), in DEG/H.sub.2O 1/0, single addition of phosphate solution into zinc nitrate/CS solution;

[0092] FIG. 20 shows manganese phosphate particles from manganese acetate tetrahydrate and 85% H.sub.3PO.sub.4 (Mn/P=1.5) without chelate complexing agent (CS), CS/Mn=0/1, (Example 18: comparative example without chelate complexing agent);

[0093] FIG. 21 shows manganese phosphate particles from manganese acetate tetrahydrate and 85% H.sub.3PO.sub.4 (Mn/P=1.5) with citric acid as chelate complexing agent (CS), CS/Mn=1/1, (Example 20);

[0094] FIG. 22 shows optical micrographs of composites formed from epoxy resin matrix with 2 wt % of zinc phosphate particles from Example 2 (plan view) coated on glass, a) thermally curing epoxy resin-zinc phosphate composite (Example 21), b) UV-curing epoxy resin-zinc phosphate composite (Example 22);

[0095] FIG. 23 shows effect of particles from Example 2 on the corrosion behavior of a standard steel surface, corrosion current I.sub.corr from potential measurements and volume resistance from electrochemical impedance measurements, steel: ST1203, medium: 3.5% of NaCl in water, T=23° C., 0.75 wt % of invention particles from Example 2 dispersed in medium; the columns mean: 1st column no ZnPO.sub.4, 2nd column with ZnPO.sub.4, CS/Zn 0.1/1 (Example 5); 3rd column with ZnPO.sub.4 CS/Zn 0.8/1 (Example 6);

[0096] FIG. 24 shows schematic depiction of dimensions for platelet-shaped particle.

[0097] Table 1 shows the elemental analysis (CHNS) of Example 2 (Zn acetate and H.sub.3PO.sub.4 as starting compounds; Zn/P 1.5, CS/Zn 1/1, H.sub.3PO.sub.4 (85 wt %).

[0098] Table 2 shows the elemental analysis (CHNS) of Example 6 (Zn nitrate and Na.sub.2HPO.sub.4 as starting compounds; Zn/P 1, CS/Zn 0.8/1, Na.sub.2HPO.sub.4 (10 wt %).

[0099] Table 3 shows dimensions and aspect ratios (AR) for invention zinc phosphate particles produced in the presence of different chelate complexing agents (CS). The dimensions of the particles were determined by scanning electron microscopy. The images were produced using the signal of the secondary electrons (acceleration voltage 10 kV, pressure 100 Pa). The micrographs shown depict a relief contrast. To determine the aspect ratios of individual particles, the length of the longer longitudinal axis (L) was divided in each case by the respective thickness (D) (FIG. 24). The average aspect ratios and the related standard deviations were determined from 20 aspect ratios of individual particles. The maximum aspect ratio reported is the largest aspect ratio found in the course of determining the aspect ratio of an individual particle.

[0100] The figures show some special advantages of the method according to the invention.

[0101] FIG. 9 depicts an embodiment of the method according to the invention. The first step is that of preparing a composition comprising at least one zinc compound and at least one chelate complexing agent (100). There is also shown a composition comprising at least one phosphate compound (105). In a subsequent step (110) composition (105) is added to composition (100). In the process, the first nuclei are formed for the particles of the invention. It may optionally be necessary for crystallization for the composition to be stirred and/or left to stand for 1 hour to 72 hours (120), preferably not less than 20 hours. Thereafter the particles are separated off, optionally isolated (130). This may be effected by sedimentation and/or centrifugation, which may also be carried out multiple times, for example from 1 time to 5 times. The particles obtained may also be dried.

[0102] The influence of the chelate complexing agent is distinctly apparent in FIG. 10. The platelets only form in the presence of the chelate complexing agent.

[0103] FIGS. 11, 12, 13 and 14 likewise show the influence of the chelate complexing agent.

[0104] FIG. 15 shows how the aspect ratio of the particles may be controlled. As the proportion of chelate complexing agent increases, the aspect ratio increases.

[0105] FIG. 17 shows that platelet-shaped particles are also obtainable with other chelate complexing agents.

[0106] It is also possible to obtain the particles from nonaqueous solutions, as is shown in FIG. 19.

[0107] Manganese (Examples 18 to 20) does not yield any platelet-shaped particles. Nor are any orthorhombic structures formed. The particles obtained are either round (FIG. 20) or acicular (FIG. 21).

[0108] XRD measurements were carried out using a D8-Advance (Bruker-AXS) powder diffractometer (40 kV; 30 mA; CuKα=1.54178 Å, divergence slit: 0.1°, detector: Lynxeye, detector slit 3 mm, measuring range: 2.8°-150° (2θ), step size: 0.02° (2θ), measuring time/step: 1 s).

[0109] FIG. 23 shows the improvement in corrosion control due to the particles of the invention.

WORKING EXAMPLES

Example 1

[0110] Zinc Phosphate Particles from Zinc Acetate Dihydrate and 85% H.sub.3PO.sub.4 (Zn/P=1.5) with Citric Acid as Chelate Complexing Agent (CS) CS/Zn=0.166/1

[0111] 3.29 g (15 mmol) of zinc acetate dihydrate were dissolved in 9.87 g of deionized water (25 wt %) and 0.480 g (2.5 mmol) of citric acid, dissolved in 1.44 g of deionized water (25 wt %), was added with stirring (about 500 rpm). The mixture was subsequently further stirred for 1 h. This was followed by 1.15 g of H.sub.3PO.sub.4 (85%) being continuously added dropwise at 23° C. with stirring (about 750 rpm) and the mixture obtained being further stirred at 600 rpm for 24 h. The zinc phosphate precipitate was centrifuged off, washed three times with deionized water, being recentrifuged (4000 rpm, 30 min at 18° C.) each time in between, and then vacuum dried at 30° C. for 24 h.

Example 1a

[0112] Zinc Phosphate Particles from Zinc Acetate Dihydrate and 85% H.sub.3PO.sub.4 (Zn/P=1.5) with Citric Acid as Chelate Complexing Agent (CS) CS/Zn=0.33/1

[0113] 3.29 g (15 mmol) of zinc acetate dihydrate were dissolved in 9.87 g of deionized water (25 wt %) and 0.95 g (4.95 mmol) of citric acid, dissolved in 2.85 g of deionized water (25 wt %), was added with stirring (about 500 rpm). The mixture was subsequently further stirred for 1 h. This was followed by 1.15 g of H.sub.3PO.sub.4 (85%) being continuously added dropwise at 23° C. with stirring (about 750 rpm). It was only after 24 h that the zinc phosphate precipitate formed, which was then stirred at 600 rpm for a further 24 h. The zinc phosphate precipitate was centrifuged off, washed three times with deionized water, being recentrifuged (4000 rpm, 30 min at 18° C.) each time in between, and then vacuum dried at 30° C. for 24 h.

Example 1b

[0114] Zinc Phosphate Particles from Zinc Acetate Dihydrate and 85% H.sub.3PO.sub.4 (Zn/P=1.5) with Citric Acid as Chelate Complexing Agent (CS) CS/Zn=0.66/1

[0115] 3.29 g (15 mmol) of zinc acetate dihydrate were dissolved in 9.87 g of deionized water (25 wt %) and 1.90 g (9.9 mmol) of citric acid, dissolved in 5.71 g of deionized water (25 wt %), was added with stirring (about 500 rpm). The mixture was subsequently further stirred for 1 h. This was followed by 1.15 g of H.sub.3PO.sub.4 (85%) being continuously added dropwise at room temperature with stirring (about 750 rpm). It was only after 24 h that the zinc phosphate precipitate formed, which was then stirred at 600 rpm for a further 24 h. The zinc phosphate precipitate was centrifuged off, washed three times with deionized water, being recentrifuged (4000 rpm, 30 min at 18° C.) each time in between, and then vacuum dried at 30° C. for 24 h.

Example 2

[0116] Zinc Phosphate Particles from Zinc Acetate Dihydrate and 85% H.sub.3PO.sub.4 (Zn/P=1.5) with Citric Acid as Chelate Complexing Agent (CS), CS/Zn=1/1

[0117] 3.29 g (15 mmol) of zinc acetate dihydrate were dissolved in 9.87 g of deionized water (25 wt %) and 2.88 g (15 mmol) of citric acid, dissolved in 8.64 g of deionized water (25 wt %), was added with stirring (about 500 rpm). The mixture was subsequently further stirred for 1 h. This was followed by 1.15 g of H.sub.3PO.sub.4 (85%) being continuously added dropwise at 23° C. with stirring (about 750 rpm). It was only after 24 h that the zinc phosphate precipitate formed, which was then stirred at 600 rpm for a further 24 h. The zinc phosphate precipitate was centrifuged off, washed three times with deionized water, being recentrifuged (4000 rpm, 30 min at 18° C.) each time in between, and then vacuum dried at 30° C. for 24 h.

Example 2a

[0118] Zinc Phosphate Particles from Zinc Acetate Dihydrate and 30% H.sub.3PO.sub.4 (Zn/P=1.5) with Citric Acid as Chelate Complexing Agent (CS), CS/Zn=1/1

[0119] 3.29 g (15 mmol) of zinc acetate dihydrate were dissolved in 9.87 g of deionized water (25 wt %) and 2.88 g (15 mmol) of citric acid, dissolved in 8.64 g of deionized water (25 wt %), was added with stirring (about 500 rpm). The mixture was subsequently further stirred for 1 h. This was followed by 3.27 g of H.sub.3PO.sub.4 (30%) being continuously added dropwise at 23° C. with stirring (about 750 rpm). It was only after 24 h that the zinc phosphate precipitate formed, which was then stirred at 600 rpm for a further 24 h. The zinc phosphate precipitate was centrifuged off, washed three times with deionized water, being recentrifuged (4000 rpm, 30 min at 18° C.) each time in between, and then vacuum dried at 30° C. for 24 h.

Example 3 (Comparative Example without Chelate Complexing Agent)

[0120] Zinc Phosphate Particles from Zinc Acetate Dihydrate and 85% H.sub.3PO.sub.4 (Zn/P=1.5) without Chelate Complexing Agent (CS), CS/Zn=0/1

[0121] 3.29 g (15 mmol) of zinc acetate dihydrate were dissolved in 9.87 g of deionized water (25 wt %) and 1.15 g of H.sub.3PO.sub.4 (85%) were continuously added (23° C.) dropwise with stirring (about 750 rpm). The zinc phosphate precipitate formed and the mixture obtained was further stirred at 600 rpm for 24 h. The zinc phosphate precipitate was centrifuged off, washed three times with deionized water, being recentrifuged (4000 rpm, 30 min at 18° C.) each time in between, and then vacuum dried at 30° C. for 24 h.

Example 3a (Comparative Example without Chelate Complexing Agent)

[0122] Zinc Phosphate Particles from Zinc Acetate Dihydrate and 30% H.sub.3PO.sub.4 (Zn/P=1.5) without Chelate Complexing Agent (CS), CS/Zn=0/1

[0123] 3.29 g (15 mmol) of zinc acetate dihydrate were dissolved in 9.87 g of deionized water (25 wt %) and 3.27 g of H.sub.3PO.sub.4 (30%) were continuously added (room temperature) dropwise with stirring (about 750 rpm). The zinc phosphate precipitate formed and the mixture obtained was further stirred at 600 rpm for 24 h. The zinc phosphate precipitate was centrifuged off, washed three times with deionized water, being recentrifuged (4000 rpm, 30 min at 18° C.) each time in between, and then vacuum dried at 30° C. for 24 h.

Example 4 (Comparative Example without Chelate Complexing Agent)

[0124] Zinc Phosphate Particles from Zinc Nitrate Hexahydrate and Na.sub.2HPO.sub.4 (Zn/P=1) without Chelate Complexing Agent (CS), CS/Zn=0/1

[0125] 2.97 g of zinc nitrate hexahydrate (0.01 mol) were dissolved in 8.91 g of deionized water and stirred for 1 h. Concurrently 1.42 g of Na.sub.2HPO.sub.4 (0.01 mol) were dissolved in 12.8 g of deionized water and added dropwise into the zinc nitrate hexahydrate solution and further stirred for 24 h. The zinc phosphate precipitate was centrifuged off, washed three times with deionized water, being recentrifuged (4000 rpm, 30 min at 18° C.) each time in between, and then vacuum dried at 30° C. for 24 h.

Example 5

[0126] Zinc Phosphate Particles from Zinc Nitrate Hexahydrate and Na.sub.2HPO.sub.4 (Zn/P=1) with Citric Acid as Chelate Complexing Agent (CS), CS/Zn=0.1/1

[0127] 2.97 g of zinc nitrate hexahydrate (0.01 mol) and 0.19 g of citric acid (0.001 mol) were dissolved in 9.48 g of deionized water and stirred for 1 h. Concurrently 1.42 g of Na.sub.2HPO.sub.4 (0.01 mol) were dissolved in 12.8 g of deionized water and added dropwise into the zinc nitrate hexahydrate solution. The zinc phosphate precipitate was centrifuged off, washed three times with deionized water, being recentrifuged (4000 rpm, 30 min at 18° C.) each time in between, and then vacuum dried at 30° C. for 24 h.

Example 6

[0128] Zinc Phosphate Particles from Zinc Nitrate Hexahydrate and Na.sub.2HPO.sub.4 (Zn/P=1) with Citric Acid as Chelate Complexing Agent (CS), CS/Zn=0.8/1

[0129] 2.97 g of zinc nitrate hexahydrate (0.01 mol) and 1.5 g (0.008 mol) of citric acid were dissolved in 13.5 g of deionized water and stirred for 1 h. Concurrently 1.42 g of Na.sub.2HPO.sub.4 (0.01 mol) were dissolved in 12.8 g of deionized water and added dropwise into the zinc nitrate hexahydrate solution. The zinc phosphate precipitate was centrifuged off, washed three times with deionized water, being recentrifuged (4000 rpm, 30 min at 18° C.) each time in between, and then vacuum dried at 30° C. for 24 h.

Example 7

[0130] Zinc Phosphate Particles from Zinc Nitrate Hexahydrate and Na.sub.2HPO.sub.4 (Zn/P=1) in DEG/1120=3.5 with Citric Acid as Chelate Complexing Agent (CS), CS/Zn=0.5/1

[0131] 2.97 g of zinc nitrate hexahydrate (0.01 mol) and 0.96 g (0.005 mol) of citric acid were dissolved in 10.6 ml of diethylene glycol and stirred for 1 h. Concurrently 1.42 g of Na.sub.2HPO.sub.4 (0.01 mol) were dissolved in a deionized water (12.8 g)/diethylene glycol (DEG, 33.5 g) mixture, stirred for 1 h and added all at once into the zinc nitrate hexahydrate solution. It is to this composition that the DEG/H.sub.2O weight ratio relates. The particle-containing mixture obtained was further stirred for 24 h. The zinc phosphate precipitate was centrifuged off, washed three times with deionized water, being recentrifuged (4000 rpm, 30 min at 18° C.) each time in between, and then vacuum dried at 30° C. for 24 h.

Example 8

[0132] Zinc Phosphate Particles from Zinc Nitrate Hexahydrate and Na.sub.2HPO.sub.4 (Zn/P=1) in DEG/1120=16.9 with Citric Acid as Chelate Complexing Agent (CS), CS/Zn=0.5/1

[0133] 2.97 g of zinc nitrate hexahydrate (0.01 mol) and 0.96 g (0.005 mol) of citric acid were dissolved in 10.6 ml of diethylene glycol and stirred for 1 h. Concurrently 1.42 g of Na.sub.2HPO.sub.4 (0.01 mol) were dissolved in a deionized water (3.25 g)/diethylene glycol (43 g) mixture, stirred for 1 h and added all at once into the zinc nitrate hexahydrate solution and further stirred for 24 h. The zinc phosphate precipitate was centrifuged off, washed three times with deionized water, being recentrifuged (4000 rpm, 30 min at 18° C.) each time in between, and then vacuum dried at 30° C. for 24 h.

Example 9

[0134] Zinc Phosphate Particles from Zinc Nitrate Hexahydrate and Na.sub.2HPO.sub.4 (Zn/P=1) in DEG/H.sub.2O=0.25 with Citric Acid as Chelate Complexing Agent (CS), CS/Zn=0.5/1

[0135] 2.97 g of zinc nitrate hexahydrate (0.01 mol) and 0.96 g (0.005 mol) of citric acid were dissolved in 10.6 ml of diethylene glycol and stirred for 1 h. Concurrently 1.42 g of Na.sub.2HPO.sub.4 (0.01 mol) were dissolved in deionized water (46.23 g), stirred for 1 h and added all at once into the zinc nitrate hexahydrate solution and further stirred for 24 h. The zinc phosphate precipitate was centrifuged off, washed three times with deionized water, being recentrifuged (4000 rpm, 30 min at 18° C.) each time in between, and then vacuum dried at 30° C. for 24 h.

Example 10

[0136] Zinc Phosphate Particles from Zinc Nitrate Hexahydrate and Na.sub.2HPO.sub.4 (Zn/P=1.6) in DEG with citric acid as Chelate Complexing Agent (CS), CS/Zn=0.5/1

[0137] 4.56 g of zinc nitrate hexahydrate (0.016 mol) and 1.6 g (0.008 mol) of citric acid were dissolved in 17.6 ml of diethylene glycol and stirred for 1 h. Concurrently 1.42 g of Na.sub.2HPO.sub.4 (0.01 mol) were stirred into diethylene glycol (125.8 ml) for 1 h and added all at once into the zinc nitrate hexahydrate solution and further stirred for 24 h. The zinc phosphate precipitate was centrifuged off, washed three times with deionized water, being recentrifuged (4000 rpm, 30 min at 18° C.) each time in between, and then vacuum dried at 30° C. for 24 h.

Example 11

[0138] Zinc phosphate particles from zinc acetate dihydrate and 85% H.sub.3PO.sub.4 (Zn/P=1.5) with Malic Acid as Chelate Complexing Agent (CS), CS/Zn=1/1

[0139] 3.29 g (15 mmol) of zinc acetate dihydrate were dissolved in 9.87 g of deionized water (25 wt %) and 2.01 g (15 mmol) of malic acid, dissolved in 6.03 g of deionized water (25 wt %), was added with stirring (about 500 rpm). The mixture was subsequently further stirred for 1 h. This was followed by 1.15 g of H.sub.3PO.sub.4 (85%) being continuously added dropwise at 23° C. with stirring (about 750 rpm). It was only after about 2 min that the zinc phosphate precipitate formed, which was then stirred at 600 rpm for a further 24 h. The zinc phosphate precipitate was centrifuged off, washed three times with deionized water, being recentrifuged (4000 rpm, 30 min at 18° C.) each time in between, and then vacuum dried at 30° C. for 24 h.

Example 12

[0140] Zinc Phosphate Particles from Zinc Acetate Dihydrate and 85% H.sub.3PO.sub.4 (Zn/P=1.5) with Malic Acid as Chelate Complexing Agent (CS), CS/Zn=1.5/1

[0141] 3.29 g (15 mmol) of zinc acetate dihydrate were dissolved in 9.87 g of deionized water (25 wt %) and 3.01 g (22.5 mmol) of malic acid, dissolved in 9.06 g of deionized water (25 wt %), was added with stirring (about 500 rpm). The mixture was subsequently further stirred for 1 h. This was followed by 1.15 g of H.sub.3PO.sub.4 (85%) being continuously added dropwise at 23° C. with stirring (about 750 rpm). It was only after 10 min that the zinc phosphate precipitate formed, which was then stirred at 600 rpm for a further 24 h. The zinc phosphate precipitate was centrifuged off, washed three times with deionized water, being recentrifuged (4000 rpm, 30 min at 18° C.) each time in between, and then vacuum dried at 30° C. for 24 h.

Example 13

[0142] (Zinc Manganese) Phosphate Particles from Zinc Acetate Dihydrate and Manganese Acetate Tetrahydrate, 85% H.sub.3PO.sub.4 (Zn,Mn)/P=1.5) without Chelate Complexing Agent (CS), (Zn/Mn=2/1), (Zn.sub.2Mn).sub.3(PO.sub.4).sub.2

[0143] 2.19 g (10 mmol) of zinc acetate dihydrate were dissolved in 6.57 g of deionized water (25 wt %) and 1.23 g (5 mmol) of manganese acetate tetrahydrate, dissolved in 3.69 g of deionized water (25 wt %), were added with stirring (about 300 rpm). Then, 1.15 g of H.sub.3PO.sub.4 (85%) were continuously added dropwise at 23° C. with stirring (about 1000 rpm). The zinc manganese phosphate precipitate formed and the mixture obtained was further stirred at 600 rpm for 24 h. The zinc manganese phosphate precipitate was centrifuged off, washed three times with deionized water, being recentrifuged (4000 rpm, 30 min at 18° C.) each time in between, and then vacuum dried at 30° C. for 24 h.

Example 14

[0144] (Zinc Manganese) Phosphate Particles from Zinc Acetate Dihydrate and Manganese Acetate Tetrahydrate, 85% H.sub.3PO.sub.4 (Zn,Mn)/P=1.5) without Chelate Complexing Agent (CS) (Zn/Mn=1/2), (Zn.sub.2Mn).sub.3(PO.sub.4).sub.2

[0145] 1.097 g (5 mmol) of zinc acetate dihydrate were dissolved in 3.30 g of deionized water (25 wt %) and 2.45 g (10 mmol) of manganese acetate tetrahydrate, dissolved in 7.35 g of deionized water (25 wt %), were added with stirring (about 300 rpm). 1.15 g of H.sub.3PO.sub.4 (85%) were continuously added dropwise at 23° C. into this mixture with stirring (about 1000 rpm). The zinc manganese phosphate precipitate formed and the mixture obtained was further stirred at 600 rpm for 24 h. The zinc manganese phosphate precipitate was centrifuged off, washed three times with deionized water, being recentrifuged (4000 rpm, 30 min at 18° C.) each time in between, and then vacuum dried at 30° C. for 24 h.

Example 15

[0146] (Zinc Manganese) Phosphate Particles from Zinc Acetate Dihydrate and Manganese Acetate Tetrahydrate, 85% H.sub.3PO.sub.4 (Zn,Mn)/P=1.5) with Citric Acid as Chelate Complexing Agent (CS) (Zn/Mn=2/1), CS/(Zn/Mn)=1/1, (Zn.sub.2Mn).sub.3(PO.sub.4).sub.2

[0147] 2.19 g (10 mmol) of zinc acetate dihydrate were dissolved in 6.57 g of deionized water (25 wt %) and 1.23 g (5 mmol) of manganese acetate tetrahydrate, dissolved in 3.69 g of deionized water (25 wt %), were added with stirring (about 300 rpm). This mixture of the two was admixed with 2.88 g (15 mmol) of citric acid monohydrate, dissolved in 8.64 g of water (25 wt %), with magnetic stirring (about 500 rpm). Stirring was subsequently continued for 1 h. This was followed by the continuous dropwise addition of 1.15 g of H.sub.3PO.sub.4 (85%) at 23° C. with stirring (about 750 rpm). It was only after about 20 h that the zinc manganese phosphate precipitate formed, which was then stirred at 600 rpm for a further 24 h. The zinc manganese phosphate precipitate was centrifuged off, washed three times with deionized water, being recentrifuged (4000 rpm, 30 min at 18° C.) each time in between, and then vacuum dried at 30° C. for 24 h.

Example 16

[0148] (Zinc Manganese) Phosphate Particles from Zinc Acetate Dihydrate and Manganese Acetate Tetrahydrate, 85% H.sub.3PO.sub.4 (Zn,Mn)/P=1.5) with Citric Acid as Chelate Complexing Agent (CS) (Zn/Mn=1/2), CS/(Zn/Mn)=1/1, (Zn.sub.2Mn).sub.3(PO.sub.4).sub.2

[0149] 1.097 g (5 mmol) of zinc acetate dihydrate were dissolved in 3.3 g of deionized water (25 wt %) and 2.45 g (10 mmol) of manganese acetate tetrahydrate, dissolved in 7.35 g of deionized water (25 wt %), were added with stirring (about 300 rpm). This mixture of the two was admixed with 2.88 g (15 mmol) of citric acid monohydrate, dissolved in 8.64 g of water (25 wt %), with magnetic stirring (about 500 rpm). Stirring was subsequently continued for 1 h. This was followed by the continuous dropwise addition of 1.15 g of H.sub.3PO.sub.4 (85%) at 23° C. with stirring (about 750 rpm). It was only after about 20 h that the zinc manganese phosphate precipitate formed, which was then stirred at 600 rpm for a further 24 h. The zinc manganese phosphate precipitate was centrifuged off, washed three times with deionized water, being recentrifuged (4000 rpm, 30 min at 18° C.) each time in between, and then vacuum dried at 30° C. for 24 h.

Example 17

[0150] Zinc Phosphate Particles from Zinc Nitrate Hexahydrate and Na.sub.2HPO.sub.4 (Zn/P=1) with Malic Acid as Chelate Complexing Agent (CS), CS/Zn=0.8/1

[0151] 2.97 g of zinc nitrate hexahydrate (0.01 mol) and 1.07 g (0.008 mol) of malic acid were dissolved in 12.1 g of deionized water and stirred for 1 h. Concurrently 1.42 g of Na.sub.2HPO.sub.4 (0.01 mol) are dissolved in 12.8 g of deionized water and added dropwise into the zinc nitrate hexahydrate solution with stirring (about 750 rpm) and further stirred at 600 rpm for 24 h. The zinc phosphate precipitate was centrifuged off, washed three times with deionized water, being recentrifuged (4000 rpm, 30 min at 18° C.) each time in between, and then vacuum dried at 30° C. for 24 h.

Example 18: (Comparative Example without Chelate Complexing Agent)

[0152] Manganese Phosphate Particles from Manganese Acetate Tetrahydrate and 85% H.sub.3PO.sub.4 (Mn/P=1.5) without Chelate Complexing Agent (CS), CS/Mn=0/1

[0153] 3.68 g (15 mmol) of manganese acetate tetrahydrate were dissolved in 9.87 g of deionized water (25 wt %) and 1.15 g of H.sub.3PO.sub.4 (85%) were continuously added dropwise (23° C.) with stirring (about 1000 rpm). The manganese phosphate precipitate formed. The mixture obtained was further stirred at 600 rpm for 24 h. The manganese phosphate precipitate was centrifuged off, washed three times with deionized water, being recentrifuged (4000 rpm, 30 min at 18° C.) each time in between, and then vacuum dried at 30° C. for 24 h.

Example 19

[0154] Manganese Phosphate Particles from Manganese Acetate Tetrahydrate and 85% H.sub.3PO.sub.4 (Mn/P=1.5) with Citric Acid as Chelate Complexing Agent (CS), CS/Mn=0.166/1

[0155] 3.68 g (15 mmol) of manganese acetate dihydrate were dissolved in 9.87 g of deionized water (25% wt %) and 0.480 g (2.5 mmol) of citric acid monohydrate, dissolved in 1.44 g of deionized water (25 wt %), was added with stirring (about 500 rpm). Stirring was then continued for 1 h. After 1 h, 1.15 g of H.sub.3PO.sub.4 (85%) were continuously added dropwise at 23° C. with stirring (about 1000 rpm). The manganese phosphate precipitate formed. The mixture obtained was further stirred at 600 rpm for 24 h. The manganese phosphate precipitate was centrifuged off, washed three times with deionized water, being recentrifuged (4000 rpm, 30 min at 18° C.) each time in between, and then vacuum dried at 30° C. for 24 h.

Example 20

[0156] Manganese Phosphate Particles from Manganese Acetate Tetrahydrate and 85% H.sub.3PO.sub.4 (Mn/P=1.5) with Citric Acid as Chelate Complexing Agent (CS), CS/Mn=1/1

[0157] 3.68 g (15 mmol) of manganese acetate tetrahydrate were dissolved in 11.04 g of deionized water (25% wt %) and 2.88 g (15 mmol) of citric acid monohydrate, dissolved in 8.64 g of deionized water (25 wt %), was added with stirring (about 500 rpm). Stirring was then continued for 30 min. After 1 h, 1.15 g of H.sub.3PO.sub.4 (85%) were continuously added dropwise at 23° C. with stirring (about 1000 rpm). It was only after about 8 h that the manganese phosphate precipitate formed, which was then stirred at 600 rpm for a further 24 h. The manganese phosphate precipitate was centrifuged off, washed three times with deionized water, being recentrifuged (4000 rpm, 30 min at 18° C.) each time in between, and then vacuum dried at 30° C. for 24 h.

Example 21

[0158] Producing a Composite Material from Zinc Phosphate Particles and a Thermally Curing Epoxy Resin

[0159] 3.6 g of bisphenol A epoxy resin (Beckopox EP307, Cytec) were dissolved in 9.6 g of butyl acetate and admixed with 1.69 g of phenolic resin solution (Phenodur PR722/53BG/B, Cytec). Then, 0.1 g of zinc phosphate particles from Example 2 was added with stirring. The mixture obtained was further stirred for 2 h, dipcoated onto microscope slides made of glass and thermally cured at 200° C. for 30 min. A translucent coating formed.

Example 22

[0160] Producing a Composite Material from Zinc Phosphate Particles and a UV-Curing Epoxy Resin

[0161] 2.47 g of cycloaliphatic epoxy resin (Araldit-CY-179, Huntsman) and 2.47 g of bisphenol A epoxy resin (Beckopox EP128, Cytec) were mixed with 1.30 g of trimethylolpropane oxetane as reactive diluent. Then, 0.1 g of zinc phosphate particles from Example 2 was added with stirring. The mixture obtained was further stirred for 2 h, admixed with 0.13 g of UV-6974 (Cyracure Photoinitiator, Dow), dipcoated onto microscope slides made of glass and then UV-cured (UV curing stand from Beltron, 2 lamps, ½ power, 2 m/min). A translucent coating formed.

TABLE-US-00001 TABLE 1 Probe C/% H/% N/% 1x centrifuged ≦0.3 2.13 — 2x centrifuged ≦0.2 1.72 — 4x centrifuged ≦0.3 1.70 —

TABLE-US-00002 TABLE 2 Probe C/% H/% N/% 1x centrifuged ≦0.8 1.81 ≦0.4 2x centrifuged ≦0.2 1.77 ≦0.1 4x centrifuged ≦0.2 1.73 ≦0.1

TABLE-US-00003 TABLE 3 L: average length distribution of long longitudinal axis of platelets: D: average thickness distribution of platelets, AV = average aspect ratio from 20 determinations of aspect ratios of individual particles from scanning electron microscopy, AV.sub.max = maximum aspect ratio from individual particle determination. CS L/μm D/μm AV AV.sub.max maleic acid 11.81 ± 4.07 1.46 ± 0.50 8.39 ± 2.07 9.98 malic acid 11.36 ± 4.77 0.76 ± 0.24 16.32 ± 7.67  28.29 citric acid 14.18 ± 5.09 0.91 ± 0.32 17.80 ± 10.58 34.33 ascorbic acid  9.09 ± 4.17 1.36 ± 0.32 6.77 ± 2.73 9.97

REFERENCES CITED

[0162] Yuan et al. Applied Mechanics and Materials, 2012, 236-237, 105-108. [0163] McCurdy et al. Materials Research Bulletin 2008, 43, 1836-1841. [0164] Lubkowski et al. Rev. Adv. Mater. Sci. 2007, 14, 46-48, [0165] DE2842150 [0166] DE3046697 A1 [0167] U.S. Pat. No. 4,153,479 [0168] EP 0896641 B1 [0169] DE 6970161 T2 [0170] U.S. Pat. No. 5,137,567 [0171] U.S. Pat. No. 5,030,285 [0172] DE1815112