DE3315850A1 - Process for the preparation of yellow bismuth vanadate pigment - Google Patents

Abstract

The present invention relates to a process for the preparation of single-phase yellow bismuth vanadate pigments by reaction of a stoichiometric mixture of finely disperse bismuth(III) and vanadium(V) compounds and subsequent comminution to pigment size.

Description

Process for making yellow bismuth vanadate

Pigment The present invention relates to a method of manufacture of yellow phase-pure bismuth vanadate pigment and its use.

Bismuth vanadate (BiVO4) occurs naturally as the mineral pucherite yellow-brown color (Frenzel 1871) and crystallizes in an orthorhombic distorted scheelite structure (M.M. Quirashi, W.H. Barnes; Am.Min.

38, 1953, p. 489). Synthetic BiVO4 is isotype with zirconium (ZrSiO4) and changes irreversibly into a monoclinic distorted one above 400 to 5000C Scheelite structure (B-ferqusonite type) around (R.S. Roth, J.L. Waring; Am. Min. 48, 1963, P. 1348).

DE-AS 2 727 863 teaches the production of bright yellow monoclinic Bismuth vanadate pigment by precipitation from bismuth nitrate and an alkali vanadate solution. The precipitation is converted into monoclinic BiVO4 by tempering.

Correspondingly, according to DE-OS 2 727 864, a BiVO4 gel is produced by heating converted into monoclinic BiVO4 in aqueous suspension.

The synthesis of BiVO4 mixed phases is achieved by annealing the respective Mixed phase of corresponding amounts of the individual components at higher temperatures. For example, DE-AS 2 727 865 has the production of mixed phases with the composition BiV04 . x Al203. y SiO2 on the subject. The color quality is determined by an intermediate grinding the pigments improved. Without the addition of Al203 and SiO2, one obtains after annealing 8500C in air (without intermediate grinding and renewed calcination) a product of insufficient Quality.

According to DE-AS 2 933 778 BiVO4 / BiPO4 / AlPO4 mixed phases are made by annealing the corresponding amounts of the BiPO4, vanadium (V) and aluminum components obtained at temperatures between 700 and 11000C. Depending on the Al 203 and P205 content as well as depending on the annealing temperature, products with green-yellow to yellow-orange hues preserved.

Pure bismuth vanadate pigments with good color qualities can be used so only produce in a complex two-stage process (precipitation, calcination). With bismuth nitrate an expensive bi-raw material is also used, through him and the nitric acid used are these processes with a high accumulation of nitrates afflicted.

The mixed phases naturally only have a lower content of coloring component BiVO4, which is detrimental to its coloristic properties affects. The production of these mixed phases takes place at temperatures of more than 7000C and sometimes requires a second annealing after an intermediate grinding.

The object of the present invention is to provide a method to provide that does not have the disadvantages of the above-mentioned method and the Manufacture of pure bismuth vanadate pigments in a more economical way with a less effort for exhaust air and wastewater purification allowed.

Surprisingly, it has now been found that one is phase and color pure yellow bismuth vanadate pigments (BiVO4) are obtained when stoichiometric mixtures finely dispersed bismuth (III) and vanadium (V) compounds in the presence of mineralizing Reacts substances at temperatures from 350 to 7500C and the reaction products Crushed pigment size.

Stoichiometric in the context of this application is intended to mean that the actual Mixing ratios around + 5% by weight of the calculated stoichiometric ratios may differ.

The bismuth components are bismuth III oxide (Bi203), basic bismuth carbonate ((BiO) 2CO3) and / or bismuth oxide aquates (Bi2O 3.xH2O, e.g. BiOOH for x = 1 or Bi (OH) 3 for x = 3) suitable.

Ammonium metavanadate (NH4VO3), vanadium pentoxide can be used as sources of vanadium (V205) and / or alkali metavanadates ((Na, K) VO3) can be used.

The raw materials should have the highest possible degree of fineness and reactivity possess so that the pigment formation in short times and at low temperatures he follows.

As a result, the particle growth and the color properties that depend on it better controlled.

Suitable bismuth components are basic bismuth carbonate with BET surface areas from 5 to 25 m2 / g and bismuth oxide aquates of the general composition Bi2O3.xH3O (Values for x to 3) with BET surface areas of up to 25 m / g.

The bismuth oxide aquates obtained by oxidation are particularly preferred finely divided bismuth metal powder in aqueous suspension at temperatures of 60-900C, intensive stirring and gassing with air, oxygen and / or air / oxygen mixtures can be obtained.

Suitable bismuth metal powders are produced either by mechanical grinding of bismuth bars in ball or mortar mills or by atomizing a bismuth melt contained in water, the grain fraction being 4100 µm for the formation of bismuth oxide aquat is separated by sieving.

The preferred used vanadium pentoxide (V205) should have BET surfaces between 5 and 20 m / g (BET surface area determined by N2 adsorption according to DIN 661 131).

Suitable additives with a mineralizing effect for the purposes of this invention are NH4N03, HNO3, nitrates, peroxodisulfates and / or peroxides of alkali and / or Alkaline earth metals individually or in combination.

The mineralizing substances must only be used in quantities of 0.1 to 25% by weight, preferably 0.1 to 5% by weight, based on the solids content, are added.

It is surprising that even in small amounts these additives produce a Implementation of corresponding raw material mixtures into phase-pure, yellow BiVO4 to have.

The mixing of the individual components can be done in the dry (mixer, Mills) as well as in the moist state. In the case of wet mixing, there are aggregates such as kneaders, screws, stirred tanks, dissolvers and / or wet mills are suitable, with the solids content can be between 40 and 80% by weight.

Are the preferred bismuth oxide aquates (Bi203.xH2O with x to 3) as If raw material is used, the vanadium V component can be used after the conversion of the bismuth metal powder be mixed into a bismuth oxide quat in the same unit (dissolver, mixed sirens, Intensive stirrer and / or bead mills). It is then filtered and the mineralizer under pasted (e.g. screws, kneaders). Mixing in the mineralizing effects However, substances can also be made after the raw material mixture has been dried, for which purpose Usual mixers are suitable.

Spray dryers, Drying cabinets, Drum dryers and belt dryers can be used. The crushing to be homogeneous Powder mixtures (residual moisture up to approx. 5% by weight) can be used in pin mills, ball mills, Pendulum mills or crushers are made.

The production of granules or pellets from the moist raw material mixture is during the drying with screws, drum dryers or aggregates of the shape granulation possible (residual moisture up to 30% by weight).

The moist paste can also be used directly for annealing, the moisture content not exceeding 35% by weight for economic reasons should.

The annealing of the raw material mixture (powder, pellets or wet paste) can be used in directly or indirectly heated ovens with or without product movement in air take place.

Suitable annealing units are, for example, chamber, muffle, rotary drum, Rotary tube or rotary ring hearth furnaces.

The level of the annealing temperature is essentially dependent on the reactivity of the starting components on the amount of mineralizer additive and on the homogeneity determined by the raw material mix.

The raw material mixture can either be placed directly in the hot oven or are heated from room temperature to the respective annealing temperature, wherein the implementation can take between 1 and 12 hours. Preferably are but sufficient for 2 to 8 hours to obtain pure bismuth vanadate pigments.

It must be rated as surprising that according to the invention Process at relatively low temperatures of 350 to 6500C (preferably 400 to 6000C), mineralizer additives up to 5% by weight (KNO3 and / or K2S2O8 are preferred) and high quality pigments can be obtained only once annealing.

Products that are manufactured without additives that have a mineralizing effect, are of inferior color quality even at annealing temperatures of 7500C. They wise pale and partly dirty colors.

After annealing, the products were pre-shredded (depending on Product quantity in a mortar or in a mill) as well as a wet grinding in a pearl mill at 1500 rpm. The grinding time was varied between 10 and 120 minutes. After that it was filtered, washed salt-free and dried in air in a drying cabinet at 1050C and deagglomerates the product (mortar or grinder).

The phase purity test was carried out radiographically, after which all products are available as monoclinic BiVO4. The chemical composition was analytically determined and delivered Bi2O3 contents of 71.5 + 0.5% by weight (theory 71.92%) and V2O5 proportions of 27.9 + 0.6% by weight (theory 28.08%).

The bismuth vanadates produced by the process according to the invention have BET surface areas between 4 and 20 m2 / g (BET surface areas determined using the N2 adsorption method according to DIN 661 131) and are ideal for coloring paints and plastics and emulsion paints.

The invention is explained below with the aid of examples.

Comparative Example A (Precipitation Process) Corresponding to Example 1 of DE-A 2 727 863 15.16 g of Na3VO4 were dissolved in 250 ml of 1N NaOH hot and within of 2 minutes while stirring in a solution of 40 g Bi (NO3) 3 x 5 H20 in 250 ml 1 n HNO3 given. The mixture was stirred vigorously at RT, the pH to 3.5 readjusted and the yellow-orange precipitate was stirred for another 30 minutes. To Filtration and washing were followed by annealing of the moist filter cake for 2 hours at 4000C in air in a porcelain pan. Then the calcinate was in a Crushed mortar. The monoclinic BiVO4 obtained is colored canary yellow-2 and has a BET surface area of 5.7 m2 / g.

Example 1 6 l of water were placed in a 10 l glass nozzle, 543.35 g of bismuth metal powder (~ 40 µm, 99.99%) added and with a Kotthoff mixer siren suspended at 2800 rpm for 4 hours. He was gassed with pure oxygen and with one Worked at a temperature of approx. 700C.

After the bismuth powder has been converted into a Bi2O3 aquat (yellowish-white Suspension), 239.32 g of V205 (89.8%) were added, followed by more Stirred for 4 hours at 2800 rpm while gassing with oxygen.

It was filtered, dried at 1050C in a drying cabinet and the Mixture divided in a pin mill. 150 g each of this raw material mixture were like follows in a rotary kiln (indirect heating) annealed in air: a. 2 h at 400, 600 and 7500C b. 4 and 8 hours at 705 ° C. This is followed by dry pre-comminution of the annealed products and wet grinding at 1500 rpm in an agitator ball mill (30 min). Afterward was filtered, washed and dried at 1050C in a drying cabinet.

A characterization of the products is shown in Table 1.

Table 1: Characterization of Examples 1a, b Example of annealing conditions for flour in shade specific Agitator ball surface mill according to BET [m-2 / g] 1a 2 h, 400 ° C in a rotary kiln, yellow-olive - without mineralizer 2 h, 600 ° C in the rotary kiln green-yellow - without mineralizer 1b 4 h, 750 ° C. in a rotary tube # 30 min dark yellow 7.0 without mineralizer 8 h, 750 ° C. in a rotary kiln, dark yellow 6.6. without mineralizer Example 2 401.8 g of basic bismuth carbonate (80.5% Bi2O3), 142.1 g of vanadium pentoxide (98.8%) and 25.2 g of KNO3 (5% by weight, based on BiVO4) were added with 400 ml of water mixed intensively (? N 59% solids content) and the paste into pellets about 5 mm in diameter with approx.

10% residual moisture processed. These pellets were kept at 4000C for 2 hours Annealed in air with product agitation, pre-crushed dry in a mill and A quarter of the annealed product each for 10, 20, 30 and 60 minutes wet in an agitator ball mill ground at 1500 rpm and worked up as previously described.

Table 2 Characterization of the end products, grinding in shade-specific2 surface Agitator ball according to BET / m "/ q / mill 10 min. Golden yellow 4.3 20" 11 5.0 30 "" 5.8 60 "canary yellow 8.1 Example 3 Basic bismuth carbonate, vanadium pentoxide and potassium peroxodisulphate / sodium peroxide as a mineralizer were mixed as follows and annealed in a rotary kiln: a) 120.5 g (BiO) 2CO3 (89.5% Bi2O3), 42.6 g V205 (98.8%), 1.53 g K2S208 (98%) and 0.1 g Nu 202 (# 1 wt. t mineralizer, based on BiVO4) were in one Mixing vessel with 200 ml of water mixed intensively (approx. 45% solids content), the homogeneous paste dried at 1050C and processed into pellets with about 15% residual moisture. The pellets were annealed at 425 ° C. in air with product agitation (2 h). The calcine was pre-crushed in a mortar and wet for 10 minutes in an agitator ball mill ground at 1500 rpm. The further work-up was carried out as previously described.

b) According to example a), 2.5% by weight of mineralizer (3.8 g K2S208 and 0.1 g Na2O2) mixed in and the pellets (approx. 15% residual moisture) for 2 hours annealed at 4250C with product agitation. Grinding and work-up were carried out analogously for example 3a).

Table 3 shows the characterization of the products.

Table 3: Characterization of example 3 Example annealing conditions / Grinding in spec. Surface color mineralizer agitator according to BET [m-2 / g] ball mill 3 a) 2 h, 425 ° C 30 min 6.8 golden yellow (1% by weight K2S2O8 / Na2O2) rotary tube 3 b) 2 h, 425 ° C 30 min 7.0 golden yellow (2.5% by weight K2S2O8 / Na2O2) rotary kiln example 4,543.35 a bismuth metal powder (<40 ßm, 99.99% ig) were according to example 1 and processed with 239.32 g of V205 (98.8%) to a homogeneous paste. After drying the paste at 1050C, 150 g of this raw material mixture were added intensively mixed with 2.5, 5, 10 and 25% by weight of KNO3 (based on BiVO4) and how follows annealed in air in the rotary kiln: a. 150 g with 3.76 g KNO3 (99.5%) 8 h at 4000C (Mixture placed directly in a hot oven) b. 150 g with 7.51 g KNO3 (99.5%) 8 h at 4000C (mixture placed directly in a hot oven) c. 150 g with 15.02 g KNO3 (99.5 %) 8 h at 400 "C (mixture placed directly in a hot oven) d. 150 g with 37.56 g KNO3 (99.5%) 8 h at 4000C (mixture placed directly in a hot oven) e. 150 g Pickled with 7.51 g KNO3 (99.5%) from room temperature to 4000C and 2 h at annealed at this temperature.

The grinding and work-up were carried out according to Example 1; the Characterization of the products is recorded in Table 4.

Example 5 A raw material mixture as described in Example 1 was used produced, each 125 g of this mixture with 5 resp.

25% by weight KNO3 (based on BiVO4) intensively and in a muffle furnace Annealed in air in crucibles without product movement: a. 125 g each with 6.26 g KNO3 (99.5 % ig) 1 h at temperatures of 400, 500 and 600 "C (placed directly in a hot oven) b. 125 g each with 31.30 g KNO3 (99.5%) for 1 h at temperatures of 400, 500 and 6000C (placed directly in a hot oven) The usual grinding and work-up followed. Table 4 shows the characterization of the products.

Example 6 217.36 g of metallic bismuth powder (C 40 Klm, 99.99%) were according to Example 1 at 80 ° C with 2.5 1 of water in a 5-liter glass nozzle converted into a bismuth-III-oxygen compound (4 h), 95.73 g V205 (98.8%) added and stirred vigorously for a further 4 h.

After filtration, drying at 105 "C and pulverization, each 150 g of this raw material mixture mixed with 1 and 2.5% by weight of K2S2O8 (based on BiVO4) and annealed in air in a rotary kiln as follows: a. 150 g with 1.50 g K2S2O8 4 h at 6000C (put directly into the hot oven) b. 150 g with 3.74 g K2S2O8 at 6000C (put directly in the hot oven).

It was ground and worked up as before; the characterization the end products are given in Table 5.

Example 7 155.26 g of metallic bismuth powder (<40 wm, 99.99 %) were mixed with 2.5 l of water at 750C in a 5 l glass nozzle within 4 h converted into a Bi2O3 aquat, 68.38 g V205 (98.8%) added and intensively for another 4 h touched. After filtering and drying the paste, 200 g of this mixture were added 10.2 g KNO3 (5% by weight, based on BiVO4) mixed and 8 h at 4000C in a rotary kiln annealed in air.

The annealed product was pre-comminuted dry and one third of each batch was ground wet for 15, 60 and 120 minutes in a stirred ball mill at 1500 rpm. The usual work-up followed. The characterization of the products is shown in Table 5. Table 4: Characterization of Examples 4 and 5 Example of annealing conditions grinding in shade spec. surface and mineralizer agitator ball mill according to BET [m-2 / g] 4 a 8 h, 400 ° C in the rotary kiln with 2.5 wt% KNO3 4 to 8 h, 400 ° C in the rotary kiln with 5 wt% KNO3 4 c 8 h, 400 ° C in a rotary tube with 30 min # canary yellow # 7.2 # 0.4 10 wt% KNO3 4 d 8 h, 400 ° C in the rotary kiln with 25 wt% KNO3 4 e 2 h, 400 ° C in the rotary kiln, from RT heated up, with 5 wt .-% KNO3 5 a 1 h, 400 ° C annealing without 1 h, 500 ° C rotary movement with 1 h, 600 ° C 5% by weight KNO3 30 min canary yellow 5 b 1 h, 400 ° C. annealing without # 7.3 # 0.5 1 h, 500 ° C rotary movement with 1 h, 600 ° C 25% by weight KNO3 canary yellow Table 5: Characterization of Examples 6a, b and 7 Example of annealing conditions grinding in shade spec. surface and mineralizer agitator ball according to BET [m-2 / g] mill 6 a 4 h, 400 ° C in the rotary kiln with 1% by weight K2S2O8 30 min canary yellow 6.7 b 4 h, 600 ° C in the rotary kiln with 2.5 wt% K2S2O8 7 8 h, 400 ° C in the rotary kiln with 15 min canary yellow 5.6 5 wt% KNO3 60 min 12.8 120 min 18.5

Claims (10)

Claims 1. A process for the production of phase-pure yellow Bismuth vanadate pigment through conversion of stoichiometric mixture finely dispersed Bismuth (III) and vanadium (V) compounds and subsequent comminution to pigment size, characterized in that the reaction has a mineralizing effect with the addition Substances takes place. 2. The method according to claim 1, characterized in that the Busmut (III) connections Bismuth trioxide, basic bismuth carbonate and / or bismuth oxide aquate (Bi203.xH2O, with x to 3). 3. The method according to claim 2, characterized in that the bismuth oxide aquate by oxidation of finely divided bismuth metal powder with a grain size of preferably less than 40 µm in aqueous suspension at temperatures between 20 and 1000C can be obtained. 4. The method according to claims 1 to 3, characterized in that that the vanadium components ammonium metavanadate, vanadium pentoxide and / or alkali metavanadate are. 5. The method according to any one of claims 1 to 4, characterized in, that the mineralizing substances NH4NO3, HN03, nitrates, peroxodisulphates and / or peroxides of alkali and / or alkaline earth metals. 6. The method according to claims 1 to 5, characterized in, that the mineralizing substances, based on the solids content, in quantities from 0.1 to 25% by weight, preferably from 0.1 to 5% by weight, can be added. 7. The method according to claims 1 to 6, characterized in that that the reaction at temperatures between 350 and 7500C, preferably between 400 and 6000C. 8. The method according to any one of claims 1 to 7, characterized in that that the conversion to pure bismuth vanadate pigments in just one annealing step he follows. 9. The method according to any one of claims 1 to 8, characterized in, that the reaction of the mixture between 0.5 and 12 hours, preferably between 2 and 8 hours. 10. Use of the prepared according to any one of claims 1 to 9 yellow bismuth vanadate pigments for coloring paints, plastics and emulsion paints.