CA1220006A - Monoclinic greenish lead chromate pigments - Google Patents
Monoclinic greenish lead chromate pigmentsInfo
- Publication number
- CA1220006A CA1220006A CA000460696A CA460696A CA1220006A CA 1220006 A CA1220006 A CA 1220006A CA 000460696 A CA000460696 A CA 000460696A CA 460696 A CA460696 A CA 460696A CA 1220006 A CA1220006 A CA 1220006A
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- lead chromate
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
- C08K3/24—Acids; Salts thereof
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
- C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
- C09C1/14—Compounds of lead
- C09C1/20—Lead chromate
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Pigments, Carbon Blacks, Or Wood Stains (AREA)
- Paints Or Removers (AREA)
- Inorganic Compounds Of Heavy Metals (AREA)
Abstract
3-14542/TEN/1+2/+
Monoclinic greenish lead chromate pigments Abstract Monoclinic greenish lead chromate pigments con-taining lead chromate and lead sulfate in a weight ratio of 59.9:40.1 to 35:65, wherein the pigment particles have a median value of 0.3-0.4 µm and 63-78% by weight of all the particles have a Stokes diameter of 0.15-0.5µm.
The pigments obtained are distinguished on applio cation by low particle size, uniform particle size dis-tribution, high tinctorial strength, great hiding power, good rheological properties and high saturation. Note-worthy is the more greenish hue of these pigments and the lower soluble lead salts content compared with known pig-ments of the same hue.
Monoclinic greenish lead chromate pigments Abstract Monoclinic greenish lead chromate pigments con-taining lead chromate and lead sulfate in a weight ratio of 59.9:40.1 to 35:65, wherein the pigment particles have a median value of 0.3-0.4 µm and 63-78% by weight of all the particles have a Stokes diameter of 0.15-0.5µm.
The pigments obtained are distinguished on applio cation by low particle size, uniform particle size dis-tribution, high tinctorial strength, great hiding power, good rheological properties and high saturation. Note-worthy is the more greenish hue of these pigments and the lower soluble lead salts content compared with known pig-ments of the same hue.
Description
- 1 - 3-14542/TEN/1~2/~
The invention relates to monoclinic green;sh Lead chromate p;~ments which are d;st;n~uished by a particuo larly high f;neness of the pigment particles and a narrow particle size distribution7 Lead chromate pi~ments have been widely used for many years for coLouring plastics materi3ls and paints~
Preferred pigments consist of small particles of little difference in size. US Patent 2,~12,917 describes lead chromate pigments which~ although distinguished by small average part;cle size ~for example 0.45 ~ contain indi-vidual particles which can be up to 3.5 ~m long~ German Offenlegungsschrift 10807,891 describes coated lead chro-mate pigments where at least 50% of the pig~en~ particles have a particle size of at most 1.4 ~m and 10X have a par-ticle size of less than 4.1 ~m or more~ Even the~e pig-ments leave a great deal to be desired in terms of the fineness of the particles and the uniformity of particle size~
The present invention provides monoclinic ~reenish Lead chro~ate p;gments contain;ng lead chromate and lead sulfate in a weight ratio of 59.9 40.1 to 35:65, where1n the pigment particles have a median value of 0.3-004 ~m and 63-78Z of all the part7cles have a Stokes diameter of 0415-0.5 ~m.
In preferred monoclinic lead chromate pi~ments the pigment particles have a med;an value of 0.3-0~4 ~m and b5-, .. .
The invention relates to monoclinic green;sh Lead chromate p;~ments which are d;st;n~uished by a particuo larly high f;neness of the pigment particles and a narrow particle size distribution7 Lead chromate pi~ments have been widely used for many years for coLouring plastics materi3ls and paints~
Preferred pigments consist of small particles of little difference in size. US Patent 2,~12,917 describes lead chromate pigments which~ although distinguished by small average part;cle size ~for example 0.45 ~ contain indi-vidual particles which can be up to 3.5 ~m long~ German Offenlegungsschrift 10807,891 describes coated lead chro-mate pigments where at least 50% of the pig~en~ particles have a particle size of at most 1.4 ~m and 10X have a par-ticle size of less than 4.1 ~m or more~ Even the~e pig-ments leave a great deal to be desired in terms of the fineness of the particles and the uniformity of particle size~
The present invention provides monoclinic ~reenish Lead chro~ate p;gments contain;ng lead chromate and lead sulfate in a weight ratio of 59.9 40.1 to 35:65, where1n the pigment particles have a median value of 0.3-004 ~m and 63-78Z of all the part7cles have a Stokes diameter of 0415-0.5 ~m.
In preferred monoclinic lead chromate pi~ments the pigment particles have a med;an value of 0.3-0~4 ~m and b5-, .. .
- 2 -75% of all the particles have a Stokes diameter of 0~15-0.5 ~m.
The lead chromate pigments according to the inven-tion are obtained by mixing an aqueous solution of a lead salt~ for example lead acetate, in particular Lead nitrate, with an aqueous solution of a chromate in particular sodium or potassium chromate and if desired of a sulfate, for example sodium or potas-s;um sulfate or amrnon;um sulfate, under conditions of high turbulence~ The chromate solution is advantageously pro-duced by adding alkali to a bichromate solution be-fore or during the reaction with the lead salt.
The high turbulence can be produced by various means~
for example by continuously combining the solutions to be mixed in a mixing nozzle. Mixing nozzle is to be under-stood as mean;ng a device where the solutions to be mixed are combined with one another within a relatively small space to wh;ch at least one of the solutions is supplied by means of a nozzle and preferably under elevated pres-suren The mixin9 nozzle can be constructed for example in accordance w;th the pr;nc;ple of the water jet pump, the way one of the l;quids ;s fed ;nto the mixing nozzle corresponding to the way the water ;s -fed into the water jet pump and the way the other l;qu;d ;5 fed ;nto the mix;ng nozzle correspond;ng to the connection between the water ~et pump and the flask to be evacuated and iF
desired this latter way of supplying liquid may also be effected under elevated pressure~
The precipitation ;n the m;x;ng noz~le is advan-tageously carried out by continuously combining, prefer-ably at room temperature, the aqueous solution containing the chromate and the sulfate at a flow rate o-f at least .9 m/sec ~ith the agueous solution of the lead salt at a flow rate of at least 0.08 m/sec. The precip;tat;on ;s advantageously carried out in the presence of an excess of lead ions of 0.003- 0~06 mole per litre over the stoichio--metr;c amount, preferably at room temperature and at pH 3-5 Another way of produc;ng high turbulence at the po;nt where the solut;ons are co~b;ned ;s available ;n the form of commercially available high-performance stirrers~
such as, for example, the Ultra~Turrax~stirrer from Janke und Kunkel KG, Staufen, West Germany, the Ystral stirrer from Ystral GmbH, Ballrechten-Dottingen~ West Germany~ the Poly-tron from Kinematica, Kriens~Lucerne, Switzerland~ the Silverson stirrer from Silverson Mach Ltd., Chesham/
United Kingdom, or the Chemcol mixer from Chemiecolor AG
Kilchberg-Zurich, Switzerland. Other types of high-per-formance s~irrers which can likewise be used include inter alia the Pendraulik stirrer from Pendraulik Maschinen und Apparate GmbH, Bad Ml'nder am Deister~ West ~ermany~ and continuous mixers such as those supplied by Gronfa Process Technik BY/Rozendaal, Netherlands~ It is important here that the lead salt solution on the one hand and the chroma~e and sulfate solution on the other are added as close as possibLe to the shaft of the rotor of the high-performance stirrer.
The two main components can be mixed in the zone of turbu-lence e;ther by feeding them ;n together or by adding one ~o the other. In the first case, the solutions are passed into the immediate vicinity of the shaft of the rotor by two separate lines, ~ith a chromate solu-tion and if desired also a sulfa~e solut;on advan-tageously ;n one line and a lead salt soLution ;n the other. In the second case, for example~ ~he chromate solution ` and if used the sulfa~e solution are put into the flask first and the lead salt solution is added as close as possible to the shaft of the rotor of the hi~h-performance stirrer through a tube.
The precipitated pigment is distinguished by an extremely low particle size. It has been found that bet-ter crystal structures are obta;ned if the precipitation is followed by a maturing process~ for example in the form of allowing the precipitate to stand at room temperature or by heat;ng.
The pigment obtained can be treated with texture-;mproving agents, for example long-chain aliphatic alcohols~
esters~ acids or their salts, amines, amides, waxes or ~ /Y~
,:, ~2~
res;nous substances, such as abiet;c acid, hydrogenation products, esters or salts thereof, and also nonionic, anion;c or cationic surface-active agents~
To improve the stab;l;ty to heat, l;ght and chemical attack it is advantageous to coat the pigment particles with an inorganic coating agent during the pre-cipitation or in the course of an aftertreatment in accor-dance w;th known processes described, for example, in US Patents 3,370,971, 3,639,133 and 4~046,588.
For th;s purpose, an inorgan;c compound, for example an alum;nium, silicon, antimony, tin, cerium, titanium~ or zircon;um compound or comb;nations thereof~
is precipitated on the p;gment. It has been found to be advantageous to use a serium-alumin;um-silicate layer which is formed on the p;gment, for example by adding an aqueous solution of cerium nitrate, of an alkali metal silicate and of aluminium sulfate to the aqueous pigment suspensionu The level of coating agent is advantageously 2-4Do preferably 2 20 and in particular 3-10% based on the total weight of the pigment.
The pigment is worked up in conventionaL manner, for example by filtering it off, washing the filter cake with water to remove solubLe salts, drying and pulverisingD
The median value D~ ~see DIN 530206 sheet 1, August 1972~ page 6) and the particle size distribution can be determined by known methods~ for ~xample by means of a disc centrifuge ~see The Par~icle Size Determination of Pigments with the Disc Centrifuge, K. Brugger, Powder Technology 13 ~1976), 215-221]. Med;an value and par ticle size distribution can be determined in a particu-larly simple manner us;ng the centrifugal particle size distribution analyser (model CAPA 500) put on the mar-ket by the firm of Horiba~ Kyoto, Japan~ which outputs Stokes diameters ~see DIN 53,206) and weight distribut;ons~
The determined values also hold for pigments containing up to 10~ of coating material.
The tinctorial stren9th was determined using a pro-~ram based on DIN 53,235 and an 8/d angle of measure-ment.
Electron micrographs of the pigments obtained clearly show the great advantages of these pigments~ Two characteristic main features stick out. The particles prepared are smaller and more uniform than those of tra-ditional products. The pigments obtained are dis-t;nguished on applicat;on by h;gher tinctorial strength, a more green;sh shade, great h;d;ng power, goud rheoLog;cal propert;es and h;gher saturation. Note~orthy is also the lower proport;on of lead salts soluble ;n dilute ac;ds, such as carbonate and sulfate salts, compared with known products of the same hue.
In the case of p;gments conta;n;ng more than 10%
of coa~ing material~ the median value and the particle size d;str;but;on can change so much ~hat they are no longer within the range def;ned above. Even such p;gments have said appl;cat;on advantages of h;gher t;nctor;al strength and saturation, a more greenish hue and greater h;ding po~er over conventionally obtained pigments, as described ;n~ for example, US Patent 4,046,588~ contain;ng the same proport;on of coat;ng material~
The pigments according to the invention can be used alone or m;xed with one another or w;th ather p;gments~
for example phthalocyanine blue,molybdate orange or ~erlin blue~ for pig~
ment;ng h;gh molecuLar weight organic material, for example cellulose ethers and esters~ acetylcellulose, n;trocellu~
lose, natural res;ns or synthet;c res;ns, such as polymer-isat;on or condensat;on resins, for example aminoplasts, in particular urea- and melam;ne-formaldehyde resins~
alkyd resins, phenoplasts, polycarbonates~ polyolefins~
such as polyethylene or polypropylene, as well as polysty-rene, polyvinyl chloride, polyacrylon;trile, polyacrylates~
rubber, case;n, s;l;cone and silicone res;ns.
Said h;gh molecular we;ght compounds can be not only in the form of amorphous mater;als or melts but also in the form of spinning solutions, lacquers or printing inks.
Depending on the inten~ed use, it has been found to be advantageous to use the new pigments as -toners or in the form of preparations.
In the following examples and preceding description the parts and percentages are by weight unless otherwise stated.
The median values and the particle size distribution were measured with the CAP~-500 analyser at 3000 rpm. The amount of pigment must be so adjusted, that the absorption of the beam is between 0.5 and lØ
The pigments were dispersed as follows: 15 mg of pig-ment are thoroughly wetted by means of lO0 mg of Teepol~ HB6 (34% strength solution of the sodium salt of a sul~ated primary alcohol havirlg an average molecular weight of 267, supplied by Shell) in a mortar. To the so obtained disperison is added in a 250 ml conical flask a total amount of lO0 ml of distilled water. Then the flask is put at room temperature for lO min on *
the bottom of an ultrasonic bath (Bransonic ~8 kHz from Bransonic B.V., Soest, Netherlands) filled with l litre of water.
In the following Examples reference is made to the attached drawings in which:
Figure i represents a suitable mixing nozzle, Figure 2 represents an electron micrograph (20,000x) of the pigment par-ticles of Example 2;
Figure 3 represents an electron micrograph (20,000x) of the pigment particles of Example 4; and Figure 4 represents an electron micrograph (20,000x) of the pigment particles of Example 6.
Example l: In a mixing nozzle (see Figure l), an .,.,~ ~
3L~2'~
- 6a -aqueous solution containing, per l,000 parts by volume, 31.25 parts of sodium bichromate (Na2Cr2O7 x 2H2O), 28.6 parts of anhydrous sodlum sulfate and 8.5 parts of 100% strength sodium hydroxide, is passed at room temperature through tube a at a flow rate of 4.9 m/sec and is contlnuously brought together a-t the same time with an aqueous solution containing, per 1,000 parts by volume, 146 parts of lead nitrate and 2 parts of sodi.um carbon-ate passing through tube b at a flow rate of 0.08 m/sec. After the precipitation a solution of 22.5 parts of sodium chloride in 120 parts of water is added in order to control the crystal size, and the pH is adjusted to 5.8 by adding an aqueous sodium carbonate solution. The precipitate is filtered off, is washed with water to remove soluble salts, and dried at a temperature of 80-90C. Ratio of the lead salts in the m:ixed ~ z~
-- 7 ~
crystal: S1% PbCrO4 49% PbS04 The values determined with the CAPA~500 analyser are:
median ~alue: 0.37 ~m;
Particle size distribution: 66% between 0~15 and 0.5 ~m.
The relative tinctorial strength compared to a pigment of identical composition obtained by a conven-tional process was found to be 109% using the me~hod of DIN 53,235.
~ In a mixing nozzle (see Figure 1)~
an aqueous solution containin3, per 1,000 parts by vo-Lume, 31~25 parts of sodium bichromate (Na2C~207 x 2H20)~
28.6 parts of anhydrous sodium sulfate and 8.5 parts of 10D% sodium hydroxide, i5 passed at room ~empera-ture through tube a at a flow rate of 4~9 m/sec and is continuously brought together at the same time wi~h an aqueous solution containing, per 1~000 parts by voLume, 146 parts of lead nitrate and 2 parts of sod;um carbonate and passing through tube b at a flow rate of O.U8 m/secu The supply of the solutions is controlled in such a way that, durin~ the precipitation, there is always present an excess of lead ions of 0~003 mole per litre over the sto;ch;ometr;c amount. The resulting pigment suspension leaves the nozzle via tube cu After the precipitation a solution of ?2O5 parts of sodium chloride in 120 parts of wa~er is added in order to control the crystal size, and the suspension is brought to pH 5 by adding an aqueous sodium carbonate solution.
To mature the crystal structure the precipitate is allowed to settle for 8 hours. The supernatant liquid above the prec;pitate ;s decanted off, and then, to coat the p;gment particles of the pigment suspension left behind, the following are added at room temperature with stirring: a solution of 13 parts of sodium silicate (28% of SiO2) in 120 parts of water, followed by a solution of 20 parts of aluminium sulfate x 18H20 and 10 parts of 52%
nitric acid in 300 parts of water~ and then a solution of 1.4 parts of cerium hydrox;de in 3~7 par~s of 52X nitric acid. The end pH is adiusted to 4~5 by adding 12nS parts of sodium carbonate in 120 parts of water.
The precipitate formed is filtered off, is washed with ~ater to remove soluble salts, and dried at 80~90C.
Composition of the mixed crystal: 51% PbCrO4 49X PbS04 The values determ;ned with the CAPA-500 analyser are:
median value: 0.39jum part;cle s;ze distr;but;on: 66% between 0.15 and 0~5 ~m.
Proport;on of the coating in the total weight of the p;gment: 5.5X.
The relat;ve t;nctorial strength in pa;nts com-pared with a conventionally obtained pigment of the same composition was found to be 118X us;ng the ~ethod given in DIN ~3,235.
Figure 2 shows an electron micrograph taken with 20,000-fold enlargement of the p;gment particles ultra-sonically dispersed in an alcohol-water mixture.
The hue of the pigment according to the invention in paints as measured by DIN 53,235 ;s as greenish as that of a rhombic lead chromate pigment.
~ e~ ExampLe 2 is repeated to produce a pigment containing 66% of PbCrO~ and 34X of PbS04, affording a pigment having the same hue as a comparative product. The relative t;nctoriaL strength ;s then 175~.
Median value: 0~39 ~m Particle s;ze distribution: 56% between 0.15 and 0~5 ~m Proportion of the coating in the total weight of the pigment: 5.5%
~ : In a mix;ng nozzle (see Figure 13, an aqueous solution containing~ per 1,000 parts by vo-lume~ 31.25 parts of sodium bichromate SNa2Cr207 x 2~70) 28.6 parts of sodium sulfate and 8~5 parts of 100X strength sodium hydroxide, is passed at room temperature through tube a at a flow rate of 4.9 mJsec and is continuously brought together at the same time with an aqueous solu-tion containing, per 1,000 parts by volume, 152.5 parts of lead nitrate and passing ~hrough ~ube b at a flow rate of 0.08 m/sec. The supply of the solutions is controlled in such a way that, during the precipitation, there is al~ays present an excess of lead ions of 0.0092 mole per litre over the stoichiometric amount.
After the precipitation a solution of 22.5 parts of sodium chloride in 120 par~s of water is added in order to control the crystal size, and the suspension is brought to pH 5~8 by add;ng an aqueous sodium ~arbonate solut;on.
To mature the crystal strueture the precipitate is allowed to settle for 8 hours~
The supernatant liquid above the pr~cipitate ;s decanted off, and then, to coat the pigment particles of the pigment suspens;on left behind, the follow;ng are added at room te~perature with st;rring: a solution of 13 parts of sodium silicate (28X of SiO~) in 120 parts of water~ followed by a solution of 20 parts of aluminium sulfate x 18H2n and 10 parts of 52%
nitric acid and 300 parts of water, and then a solution of 1.4 parts of cer;um hydroxide in 3.7 parts of 52X
nitric acid~ The end pH is adjusted to 4.5 by adding 12.5 parts of sodium carbonate in 120 parts of water. The pigment obtained is isolated in the customary manner by filtering, washed with water to remove solubLe salts~ and dr;ed at 80-90C.
Composition of the mixed crystaL: 50X PbCrO4 50X PbS04 Median value: 0-35 lum Particle size distribution: 66% between 0.15 and 0.5 ~m.
Proportion of the coating in the total weight of the pigment: 5.5X.
~'2~
~ 10 -The relative tinctorial strength is 108~ com-pared with a conventionally produced pigment of the same composition.
Figure 3 shows an electron micrograph of the pigmen~ d;spersion in 20,000-fold enlargement.
The hue in paints as measured by DIN 53~235 is significantly more greenish than that of known pigments of the same compositionn Example 5: In a mixing no2zle (see Figure 1) an aqueous solution containing per 1,000 parts by volume 31.25 parts of sodium bichromate (Na2Cr207 x 2HzO) 28.6 parts of anhydrous sodium sulfate and 8~5 par~s of 100% sodium hydroxide is passed at room tem-perature through tube a at a flow rate of 4.9 m/sec and is continuously brought together at the same time with an aqueous solu~ion containing per 1,000 parts by volume 146 parts of lead nitrate in 2 parts of sodium car-bonate and passing through ~ube b at a flow rate of 0.08 m/sec. The supply of the solutions is controlled in such a way thatO during the precipitation, there is al-ways present an excess of lead ;ons of O.û03 mole per litre over the stoichiometric amount. After ~he preci-pi~ation a solution of 22.5 parts of sodium carbon chlo-ride ;n 120 parts of water ;s added in order to control the crystal size, and the pH is then adjusted to 5.8 by add;ng an aqueous sod;um carbonate solu~ion. To ma-ture the crystal structure the precipiate is allowed to settle for 8 hours.
To coat the p;gment particles the supernatant liquid above the precipitate is decanted off and 95 parts of sodium s;l;cate tZ8% of SiO2) in 20U parts of water are then added at room temperature with stir-ring to the suspension left behind. This is followed~
l;ke~ise at room temperature with stirring, by a solu-tion of 20 parts of alum;nium sulfate x 18H20 and 35 parts of 52% HN03 ;n 300 parts of water and then by a solution of 1.~ parts of cerium hydroxide in ~2~
1 1 ~
The lead chromate pigments according to the inven-tion are obtained by mixing an aqueous solution of a lead salt~ for example lead acetate, in particular Lead nitrate, with an aqueous solution of a chromate in particular sodium or potassium chromate and if desired of a sulfate, for example sodium or potas-s;um sulfate or amrnon;um sulfate, under conditions of high turbulence~ The chromate solution is advantageously pro-duced by adding alkali to a bichromate solution be-fore or during the reaction with the lead salt.
The high turbulence can be produced by various means~
for example by continuously combining the solutions to be mixed in a mixing nozzle. Mixing nozzle is to be under-stood as mean;ng a device where the solutions to be mixed are combined with one another within a relatively small space to wh;ch at least one of the solutions is supplied by means of a nozzle and preferably under elevated pres-suren The mixin9 nozzle can be constructed for example in accordance w;th the pr;nc;ple of the water jet pump, the way one of the l;quids ;s fed ;nto the mixing nozzle corresponding to the way the water ;s -fed into the water jet pump and the way the other l;qu;d ;5 fed ;nto the mix;ng nozzle correspond;ng to the connection between the water ~et pump and the flask to be evacuated and iF
desired this latter way of supplying liquid may also be effected under elevated pressure~
The precipitation ;n the m;x;ng noz~le is advan-tageously carried out by continuously combining, prefer-ably at room temperature, the aqueous solution containing the chromate and the sulfate at a flow rate o-f at least .9 m/sec ~ith the agueous solution of the lead salt at a flow rate of at least 0.08 m/sec. The precip;tat;on ;s advantageously carried out in the presence of an excess of lead ions of 0.003- 0~06 mole per litre over the stoichio--metr;c amount, preferably at room temperature and at pH 3-5 Another way of produc;ng high turbulence at the po;nt where the solut;ons are co~b;ned ;s available ;n the form of commercially available high-performance stirrers~
such as, for example, the Ultra~Turrax~stirrer from Janke und Kunkel KG, Staufen, West Germany, the Ystral stirrer from Ystral GmbH, Ballrechten-Dottingen~ West Germany~ the Poly-tron from Kinematica, Kriens~Lucerne, Switzerland~ the Silverson stirrer from Silverson Mach Ltd., Chesham/
United Kingdom, or the Chemcol mixer from Chemiecolor AG
Kilchberg-Zurich, Switzerland. Other types of high-per-formance s~irrers which can likewise be used include inter alia the Pendraulik stirrer from Pendraulik Maschinen und Apparate GmbH, Bad Ml'nder am Deister~ West ~ermany~ and continuous mixers such as those supplied by Gronfa Process Technik BY/Rozendaal, Netherlands~ It is important here that the lead salt solution on the one hand and the chroma~e and sulfate solution on the other are added as close as possibLe to the shaft of the rotor of the high-performance stirrer.
The two main components can be mixed in the zone of turbu-lence e;ther by feeding them ;n together or by adding one ~o the other. In the first case, the solutions are passed into the immediate vicinity of the shaft of the rotor by two separate lines, ~ith a chromate solu-tion and if desired also a sulfa~e solut;on advan-tageously ;n one line and a lead salt soLution ;n the other. In the second case, for example~ ~he chromate solution ` and if used the sulfa~e solution are put into the flask first and the lead salt solution is added as close as possible to the shaft of the rotor of the hi~h-performance stirrer through a tube.
The precipitated pigment is distinguished by an extremely low particle size. It has been found that bet-ter crystal structures are obta;ned if the precipitation is followed by a maturing process~ for example in the form of allowing the precipitate to stand at room temperature or by heat;ng.
The pigment obtained can be treated with texture-;mproving agents, for example long-chain aliphatic alcohols~
esters~ acids or their salts, amines, amides, waxes or ~ /Y~
,:, ~2~
res;nous substances, such as abiet;c acid, hydrogenation products, esters or salts thereof, and also nonionic, anion;c or cationic surface-active agents~
To improve the stab;l;ty to heat, l;ght and chemical attack it is advantageous to coat the pigment particles with an inorganic coating agent during the pre-cipitation or in the course of an aftertreatment in accor-dance w;th known processes described, for example, in US Patents 3,370,971, 3,639,133 and 4~046,588.
For th;s purpose, an inorgan;c compound, for example an alum;nium, silicon, antimony, tin, cerium, titanium~ or zircon;um compound or comb;nations thereof~
is precipitated on the p;gment. It has been found to be advantageous to use a serium-alumin;um-silicate layer which is formed on the p;gment, for example by adding an aqueous solution of cerium nitrate, of an alkali metal silicate and of aluminium sulfate to the aqueous pigment suspensionu The level of coating agent is advantageously 2-4Do preferably 2 20 and in particular 3-10% based on the total weight of the pigment.
The pigment is worked up in conventionaL manner, for example by filtering it off, washing the filter cake with water to remove solubLe salts, drying and pulverisingD
The median value D~ ~see DIN 530206 sheet 1, August 1972~ page 6) and the particle size distribution can be determined by known methods~ for ~xample by means of a disc centrifuge ~see The Par~icle Size Determination of Pigments with the Disc Centrifuge, K. Brugger, Powder Technology 13 ~1976), 215-221]. Med;an value and par ticle size distribution can be determined in a particu-larly simple manner us;ng the centrifugal particle size distribution analyser (model CAPA 500) put on the mar-ket by the firm of Horiba~ Kyoto, Japan~ which outputs Stokes diameters ~see DIN 53,206) and weight distribut;ons~
The determined values also hold for pigments containing up to 10~ of coating material.
The tinctorial stren9th was determined using a pro-~ram based on DIN 53,235 and an 8/d angle of measure-ment.
Electron micrographs of the pigments obtained clearly show the great advantages of these pigments~ Two characteristic main features stick out. The particles prepared are smaller and more uniform than those of tra-ditional products. The pigments obtained are dis-t;nguished on applicat;on by h;gher tinctorial strength, a more green;sh shade, great h;d;ng power, goud rheoLog;cal propert;es and h;gher saturation. Note~orthy is also the lower proport;on of lead salts soluble ;n dilute ac;ds, such as carbonate and sulfate salts, compared with known products of the same hue.
In the case of p;gments conta;n;ng more than 10%
of coa~ing material~ the median value and the particle size d;str;but;on can change so much ~hat they are no longer within the range def;ned above. Even such p;gments have said appl;cat;on advantages of h;gher t;nctor;al strength and saturation, a more greenish hue and greater h;ding po~er over conventionally obtained pigments, as described ;n~ for example, US Patent 4,046,588~ contain;ng the same proport;on of coat;ng material~
The pigments according to the invention can be used alone or m;xed with one another or w;th ather p;gments~
for example phthalocyanine blue,molybdate orange or ~erlin blue~ for pig~
ment;ng h;gh molecuLar weight organic material, for example cellulose ethers and esters~ acetylcellulose, n;trocellu~
lose, natural res;ns or synthet;c res;ns, such as polymer-isat;on or condensat;on resins, for example aminoplasts, in particular urea- and melam;ne-formaldehyde resins~
alkyd resins, phenoplasts, polycarbonates~ polyolefins~
such as polyethylene or polypropylene, as well as polysty-rene, polyvinyl chloride, polyacrylon;trile, polyacrylates~
rubber, case;n, s;l;cone and silicone res;ns.
Said h;gh molecular we;ght compounds can be not only in the form of amorphous mater;als or melts but also in the form of spinning solutions, lacquers or printing inks.
Depending on the inten~ed use, it has been found to be advantageous to use the new pigments as -toners or in the form of preparations.
In the following examples and preceding description the parts and percentages are by weight unless otherwise stated.
The median values and the particle size distribution were measured with the CAP~-500 analyser at 3000 rpm. The amount of pigment must be so adjusted, that the absorption of the beam is between 0.5 and lØ
The pigments were dispersed as follows: 15 mg of pig-ment are thoroughly wetted by means of lO0 mg of Teepol~ HB6 (34% strength solution of the sodium salt of a sul~ated primary alcohol havirlg an average molecular weight of 267, supplied by Shell) in a mortar. To the so obtained disperison is added in a 250 ml conical flask a total amount of lO0 ml of distilled water. Then the flask is put at room temperature for lO min on *
the bottom of an ultrasonic bath (Bransonic ~8 kHz from Bransonic B.V., Soest, Netherlands) filled with l litre of water.
In the following Examples reference is made to the attached drawings in which:
Figure i represents a suitable mixing nozzle, Figure 2 represents an electron micrograph (20,000x) of the pigment par-ticles of Example 2;
Figure 3 represents an electron micrograph (20,000x) of the pigment particles of Example 4; and Figure 4 represents an electron micrograph (20,000x) of the pigment particles of Example 6.
Example l: In a mixing nozzle (see Figure l), an .,.,~ ~
3L~2'~
- 6a -aqueous solution containing, per l,000 parts by volume, 31.25 parts of sodium bichromate (Na2Cr2O7 x 2H2O), 28.6 parts of anhydrous sodlum sulfate and 8.5 parts of 100% strength sodium hydroxide, is passed at room temperature through tube a at a flow rate of 4.9 m/sec and is contlnuously brought together a-t the same time with an aqueous solution containing, per 1,000 parts by volume, 146 parts of lead nitrate and 2 parts of sodi.um carbon-ate passing through tube b at a flow rate of 0.08 m/sec. After the precipitation a solution of 22.5 parts of sodium chloride in 120 parts of water is added in order to control the crystal size, and the pH is adjusted to 5.8 by adding an aqueous sodium carbonate solution. The precipitate is filtered off, is washed with water to remove soluble salts, and dried at a temperature of 80-90C. Ratio of the lead salts in the m:ixed ~ z~
-- 7 ~
crystal: S1% PbCrO4 49% PbS04 The values determined with the CAPA~500 analyser are:
median ~alue: 0.37 ~m;
Particle size distribution: 66% between 0~15 and 0.5 ~m.
The relative tinctorial strength compared to a pigment of identical composition obtained by a conven-tional process was found to be 109% using the me~hod of DIN 53,235.
~ In a mixing nozzle (see Figure 1)~
an aqueous solution containin3, per 1,000 parts by vo-Lume, 31~25 parts of sodium bichromate (Na2C~207 x 2H20)~
28.6 parts of anhydrous sodium sulfate and 8.5 parts of 10D% sodium hydroxide, i5 passed at room ~empera-ture through tube a at a flow rate of 4~9 m/sec and is continuously brought together at the same time wi~h an aqueous solution containing, per 1~000 parts by voLume, 146 parts of lead nitrate and 2 parts of sod;um carbonate and passing through tube b at a flow rate of O.U8 m/secu The supply of the solutions is controlled in such a way that, durin~ the precipitation, there is always present an excess of lead ions of 0~003 mole per litre over the sto;ch;ometr;c amount. The resulting pigment suspension leaves the nozzle via tube cu After the precipitation a solution of ?2O5 parts of sodium chloride in 120 parts of wa~er is added in order to control the crystal size, and the suspension is brought to pH 5 by adding an aqueous sodium carbonate solution.
To mature the crystal structure the precipitate is allowed to settle for 8 hours. The supernatant liquid above the prec;pitate ;s decanted off, and then, to coat the p;gment particles of the pigment suspension left behind, the following are added at room temperature with stirring: a solution of 13 parts of sodium silicate (28% of SiO2) in 120 parts of water, followed by a solution of 20 parts of aluminium sulfate x 18H20 and 10 parts of 52%
nitric acid in 300 parts of water~ and then a solution of 1.4 parts of cerium hydrox;de in 3~7 par~s of 52X nitric acid. The end pH is adiusted to 4~5 by adding 12nS parts of sodium carbonate in 120 parts of water.
The precipitate formed is filtered off, is washed with ~ater to remove soluble salts, and dried at 80~90C.
Composition of the mixed crystal: 51% PbCrO4 49X PbS04 The values determ;ned with the CAPA-500 analyser are:
median value: 0.39jum part;cle s;ze distr;but;on: 66% between 0.15 and 0~5 ~m.
Proport;on of the coating in the total weight of the p;gment: 5.5X.
The relat;ve t;nctorial strength in pa;nts com-pared with a conventionally obtained pigment of the same composition was found to be 118X us;ng the ~ethod given in DIN ~3,235.
Figure 2 shows an electron micrograph taken with 20,000-fold enlargement of the p;gment particles ultra-sonically dispersed in an alcohol-water mixture.
The hue of the pigment according to the invention in paints as measured by DIN 53,235 ;s as greenish as that of a rhombic lead chromate pigment.
~ e~ ExampLe 2 is repeated to produce a pigment containing 66% of PbCrO~ and 34X of PbS04, affording a pigment having the same hue as a comparative product. The relative t;nctoriaL strength ;s then 175~.
Median value: 0~39 ~m Particle s;ze distribution: 56% between 0.15 and 0~5 ~m Proportion of the coating in the total weight of the pigment: 5.5%
~ : In a mix;ng nozzle (see Figure 13, an aqueous solution containing~ per 1,000 parts by vo-lume~ 31.25 parts of sodium bichromate SNa2Cr207 x 2~70) 28.6 parts of sodium sulfate and 8~5 parts of 100X strength sodium hydroxide, is passed at room temperature through tube a at a flow rate of 4.9 mJsec and is continuously brought together at the same time with an aqueous solu-tion containing, per 1,000 parts by volume, 152.5 parts of lead nitrate and passing ~hrough ~ube b at a flow rate of 0.08 m/sec. The supply of the solutions is controlled in such a way that, during the precipitation, there is al~ays present an excess of lead ions of 0.0092 mole per litre over the stoichiometric amount.
After the precipitation a solution of 22.5 parts of sodium chloride in 120 par~s of water is added in order to control the crystal size, and the suspension is brought to pH 5~8 by add;ng an aqueous sodium ~arbonate solut;on.
To mature the crystal strueture the precipitate is allowed to settle for 8 hours~
The supernatant liquid above the pr~cipitate ;s decanted off, and then, to coat the pigment particles of the pigment suspens;on left behind, the follow;ng are added at room te~perature with st;rring: a solution of 13 parts of sodium silicate (28X of SiO~) in 120 parts of water~ followed by a solution of 20 parts of aluminium sulfate x 18H2n and 10 parts of 52%
nitric acid and 300 parts of water, and then a solution of 1.4 parts of cer;um hydroxide in 3.7 parts of 52X
nitric acid~ The end pH is adjusted to 4.5 by adding 12.5 parts of sodium carbonate in 120 parts of water. The pigment obtained is isolated in the customary manner by filtering, washed with water to remove solubLe salts~ and dr;ed at 80-90C.
Composition of the mixed crystaL: 50X PbCrO4 50X PbS04 Median value: 0-35 lum Particle size distribution: 66% between 0.15 and 0.5 ~m.
Proportion of the coating in the total weight of the pigment: 5.5X.
~'2~
~ 10 -The relative tinctorial strength is 108~ com-pared with a conventionally produced pigment of the same composition.
Figure 3 shows an electron micrograph of the pigmen~ d;spersion in 20,000-fold enlargement.
The hue in paints as measured by DIN 53~235 is significantly more greenish than that of known pigments of the same compositionn Example 5: In a mixing no2zle (see Figure 1) an aqueous solution containing per 1,000 parts by volume 31.25 parts of sodium bichromate (Na2Cr207 x 2HzO) 28.6 parts of anhydrous sodium sulfate and 8~5 par~s of 100% sodium hydroxide is passed at room tem-perature through tube a at a flow rate of 4.9 m/sec and is continuously brought together at the same time with an aqueous solu~ion containing per 1,000 parts by volume 146 parts of lead nitrate in 2 parts of sodium car-bonate and passing through ~ube b at a flow rate of 0.08 m/sec. The supply of the solutions is controlled in such a way thatO during the precipitation, there is al-ways present an excess of lead ;ons of O.û03 mole per litre over the stoichiometric amount. After ~he preci-pi~ation a solution of 22.5 parts of sodium carbon chlo-ride ;n 120 parts of water ;s added in order to control the crystal size, and the pH is then adjusted to 5.8 by add;ng an aqueous sod;um carbonate solu~ion. To ma-ture the crystal structure the precipiate is allowed to settle for 8 hours.
To coat the p;gment particles the supernatant liquid above the precipitate is decanted off and 95 parts of sodium s;l;cate tZ8% of SiO2) in 20U parts of water are then added at room temperature with stir-ring to the suspension left behind. This is followed~
l;ke~ise at room temperature with stirring, by a solu-tion of 20 parts of alum;nium sulfate x 18H20 and 35 parts of 52% HN03 ;n 300 parts of water and then by a solution of 1.~ parts of cerium hydroxide in ~2~
1 1 ~
3.7 parts of 52% HN03~
The end pH ;s adjusted to 4.5 by adding 12~5 parts of sodium carbonate in 120 parts of water, and the result;ng prec;pitate is f;ltered off, washed with water to remove soluble salts, and dried at 80-90C.
Composit;on of the m;xed crystal: 50% PbCrO~
SO~. PbS04 Proport;on of the coat;ng ;n the total we;ght of the pi~ment- 18X.
The relative tinctorial strength is 113X com-pared with a convent;onally produced pigment of the same compos;tion.
~ e~ 000 ml of an aqueous solut;on con~
ta;ning 40.2 9 of sod;um b;chromate (Na2Cr207 x 2~20)~ of 28~6 9 of anhydrous sod;um sulfate and 8.5 g of 100~
sodium hydroxide and 1,000 mL of an aqueous solution containing 146 g of lead nitrate and 2 9 of sodium carbonate are continuously and simultaneously brought together at room temperature in separate tubes and in the immed;ate v;cinity of the shaft of the rotor of a high-performance st;rrer (d;ameter of the rotor 4 cm, circumferential speed of the rotor ~ m/sec) ;n a 5 litre reaction vessel in the course of 2 minu~es. The supply of the solut;on ;s controlled ;n such a way ~ha~, dur;ng the precipitation, there is always presen~ an excess of lead ions of 0.003 mole per litre over the stoichiometric amount.
After the prec;pitation a solution of 22.5 9 of sodium chloride in 120 ml of water is added in order to con~rol the crystal si e, and the pH is adjusted to 5.~ by adding aqueous sod;um carbonate solution. To mature ~he crystal structure the precip;tate is allowed to settle for 8 hours.
To coat the p;gment particles the supernatant liquid above the precipitate is decanted off and the following are added at room temperature with stirring to the suspens;on left behind: a solution of 13 9 of so-dium silicate (28% of Siû2) in 120 ml of water, fol-~12f~
lowed by a solut;on of 20 9 of aluminium sulfate x 18H20 and 10 9 of 52% n-itric acid in 300 ml of water, and then a solution of 1.4 9 of cer;um hy-droxide in 3O7 g of 52% nitric acid. The end pH is adjusted to 4.5 by add;ng 12.5 g of sodium carbo-nate ;n 120 ml of water~
The pigment obtained is isolated in conventional manner by f;ltration, washed with water to remove soluble salts~ and dr;ed at 80-90C.
Ratio of the lead salts ;n the mixed crystalsD 51% PbCrO4 4gX PbS0~
Proportion of the coating in the total ~eight of the p;gment: 5.5%.
Med;an Ya lue: 0.36 ~ m Partîcle s;ze d;str;but;on: 69% between 0.15 and 0~5 ~m The relative tinctorial strength is 115% com~
pared w;th a conventionally produced pigment of the same compos1t1on n The hue ;n pa;nts as measured by DIN 53,235 is significantly more green;sh than that of known products of the same composition.
Figure 4 shows an electron micrograph of the pigments in 20,000-fold enlargement.
Example 7O 1,000 ml of an aqueous solution contain;ng 139 g of lead nitrate and 1.7 g of sodium carbonate are ;ntroduced into an empty 5 litre reaction vessel equipped with a h;gh-perfor~ance stirrer (diame ter of the rotor: 4 cm; circumferential speed of ~he rotor: 4 m/sec). 1,00~ ml of an aqueous solution con~
taining 40~2 g of sodium bichromate x 2H20~ Z7~1 g of anhydrous sodium sulfate and 10 g of 100%
sodium hydroxide are then added at room temperature in the ;m~ed;ate vic;nity of the shaft of the rotor of the high-performance stirrer by means of a glass tube in the course of 2 minutes. After the precipitation lead ;ons are present in an excess of 0~005 mole per litre. In ~ 13 ~
order to control the crystal size a solution of 25 g of sodium chLor;de in 120 ml of water ;s added~ The pH
is then adjusted to 5.B by adding aqueous sodium carbo-nate solution~ To mature the crystal structure the pre-cipitate is allowed to settle for 8 hours.
To coat the pigment particles the supernatant liquid above the prec;pitate ;s decanted off and a solu-tion of 35.7 9 of aluminium sulfate x 18H20 and 30 g of titanium oxychlor;de in 200 ml of water is added at room temperature wi~h stirr;ng ~o the suspension left behind. 2a6 9 of cerium hydroxide in 7.8 y of 52X HN03 are then added. The end pH is then ad-justed to 5O0 by adding 20 9 of sodium carbonate in 200 ml of waterO The precipitate is filtered off~
washed with water to remove soluble salts, and dried at a temperature of 80-90C~
Ratio of the lead salts in the pigment~ 55% PbCr~4 45X PbS04 Proportion of the coat;ng in the total ~eight of the pigment: 9%~
The relative tinctorial strength is 119% com-pared with a conventionaLly produced pigment.
The values determined with the CAPA-500 analyser are:
Median value On37 ~m Particle size distr;bution: 66% between 0~15 and 0~5 ~mO
The hue in paints as measured by DIN 53,Z35 is distinctly greenish.
~ le 8: 1,000 ml of an aqueous soLution con-taining Z73 g of lead nitra~e and ~.5 9 of sodium carbo-nate are introduced into an empty 5 Litre reaction ves~
sel equipped w;th a high-performance stirrer (diameter of the rotor 4 cm, circumferential speed of the rotor
The end pH ;s adjusted to 4.5 by adding 12~5 parts of sodium carbonate in 120 parts of water, and the result;ng prec;pitate is f;ltered off, washed with water to remove soluble salts, and dried at 80-90C.
Composit;on of the m;xed crystal: 50% PbCrO~
SO~. PbS04 Proport;on of the coat;ng ;n the total we;ght of the pi~ment- 18X.
The relative tinctorial strength is 113X com-pared with a convent;onally produced pigment of the same compos;tion.
~ e~ 000 ml of an aqueous solut;on con~
ta;ning 40.2 9 of sod;um b;chromate (Na2Cr207 x 2~20)~ of 28~6 9 of anhydrous sod;um sulfate and 8.5 g of 100~
sodium hydroxide and 1,000 mL of an aqueous solution containing 146 g of lead nitrate and 2 9 of sodium carbonate are continuously and simultaneously brought together at room temperature in separate tubes and in the immed;ate v;cinity of the shaft of the rotor of a high-performance st;rrer (d;ameter of the rotor 4 cm, circumferential speed of the rotor ~ m/sec) ;n a 5 litre reaction vessel in the course of 2 minu~es. The supply of the solut;on ;s controlled ;n such a way ~ha~, dur;ng the precipitation, there is always presen~ an excess of lead ions of 0.003 mole per litre over the stoichiometric amount.
After the prec;pitation a solution of 22.5 9 of sodium chloride in 120 ml of water is added in order to con~rol the crystal si e, and the pH is adjusted to 5.~ by adding aqueous sod;um carbonate solution. To mature ~he crystal structure the precip;tate is allowed to settle for 8 hours.
To coat the p;gment particles the supernatant liquid above the precipitate is decanted off and the following are added at room temperature with stirring to the suspens;on left behind: a solution of 13 9 of so-dium silicate (28% of Siû2) in 120 ml of water, fol-~12f~
lowed by a solut;on of 20 9 of aluminium sulfate x 18H20 and 10 9 of 52% n-itric acid in 300 ml of water, and then a solution of 1.4 9 of cer;um hy-droxide in 3O7 g of 52% nitric acid. The end pH is adjusted to 4.5 by add;ng 12.5 g of sodium carbo-nate ;n 120 ml of water~
The pigment obtained is isolated in conventional manner by f;ltration, washed with water to remove soluble salts~ and dr;ed at 80-90C.
Ratio of the lead salts ;n the mixed crystalsD 51% PbCrO4 4gX PbS0~
Proportion of the coating in the total ~eight of the p;gment: 5.5%.
Med;an Ya lue: 0.36 ~ m Partîcle s;ze d;str;but;on: 69% between 0.15 and 0~5 ~m The relative tinctorial strength is 115% com~
pared w;th a conventionally produced pigment of the same compos1t1on n The hue ;n pa;nts as measured by DIN 53,235 is significantly more green;sh than that of known products of the same composition.
Figure 4 shows an electron micrograph of the pigments in 20,000-fold enlargement.
Example 7O 1,000 ml of an aqueous solution contain;ng 139 g of lead nitrate and 1.7 g of sodium carbonate are ;ntroduced into an empty 5 litre reaction vessel equipped with a h;gh-perfor~ance stirrer (diame ter of the rotor: 4 cm; circumferential speed of ~he rotor: 4 m/sec). 1,00~ ml of an aqueous solution con~
taining 40~2 g of sodium bichromate x 2H20~ Z7~1 g of anhydrous sodium sulfate and 10 g of 100%
sodium hydroxide are then added at room temperature in the ;m~ed;ate vic;nity of the shaft of the rotor of the high-performance stirrer by means of a glass tube in the course of 2 minutes. After the precipitation lead ;ons are present in an excess of 0~005 mole per litre. In ~ 13 ~
order to control the crystal size a solution of 25 g of sodium chLor;de in 120 ml of water ;s added~ The pH
is then adjusted to 5.B by adding aqueous sodium carbo-nate solution~ To mature the crystal structure the pre-cipitate is allowed to settle for 8 hours.
To coat the pigment particles the supernatant liquid above the prec;pitate ;s decanted off and a solu-tion of 35.7 9 of aluminium sulfate x 18H20 and 30 g of titanium oxychlor;de in 200 ml of water is added at room temperature wi~h stirr;ng ~o the suspension left behind. 2a6 9 of cerium hydroxide in 7.8 y of 52X HN03 are then added. The end pH is then ad-justed to 5O0 by adding 20 9 of sodium carbonate in 200 ml of waterO The precipitate is filtered off~
washed with water to remove soluble salts, and dried at a temperature of 80-90C~
Ratio of the lead salts in the pigment~ 55% PbCr~4 45X PbS04 Proportion of the coat;ng in the total ~eight of the pigment: 9%~
The relative tinctorial strength is 119% com-pared with a conventionaLly produced pigment.
The values determined with the CAPA-500 analyser are:
Median value On37 ~m Particle size distr;bution: 66% between 0~15 and 0~5 ~mO
The hue in paints as measured by DIN 53,Z35 is distinctly greenish.
~ le 8: 1,000 ml of an aqueous soLution con-taining Z73 g of lead nitra~e and ~.5 9 of sodium carbo-nate are introduced into an empty 5 Litre reaction ves~
sel equipped w;th a high-performance stirrer (diameter of the rotor 4 cm, circumferential speed of the rotor
4 mtsec)~ 1,000 ml of an aqueous solution containing 67.4 9 of sodium bichromate x 2HzO, 51.1 9 of anhy-drous sodium sulfate and 18~3 9 of 100% sodium hydroxide are then added in the immed;ate vicinity of the shaft of the rotor of the high-performance stirrer by means of a glass tube in the course of 2 minutes.
After the precipitation the lead ion excess is 0.008 mole of Pb2~ per litre.
To coat the pigment particles the precipiate is then heated to 65C and a solution of ~ g of anhydrous sod;um sulfate in 120 ml of water is added. The pH is then adjusted to 2.5 with about 13 g of 52X
H~3 A solution of 32~5 g of sodium silicate t28% of SiO2) and 10 9 of sodium carbonate in 120 ml of water is then addedD followed by a solution of 10 g of anti-mono trioxide, 10 g of sodium fluoride and 27 g of 5ZX
strength HN03 in 120 ml of water. The end pH is ad-justed to 6.50 by adding about 8 9 of 100% so-dium hydroxide in 120 ml of water. The precipitate is fiLtered off, is washed w;th water to remove soluble salts~ and dried at a temperature of 90C.
Ratio of the lead salts: 57% PbCrO4 43% PbS0~
The values determined w;th the CAPA-500 analyser are:
Median value 0.40 ~m Particle size distribution: 64~ between 0~15 and 0.5 ~m.
The relative t;nctorial strength compared with a conventionally produced pigment of the same composi-tion was determined as 110% using the method ~-iven in DIN 53,235.
The proportion of the coat;ng ;n the total weight of the pigment is 7.4X.
The hue in paints ;s measured by DIN 53,235 is dist;nctly greeni 5 h~
~ : 0.6 part of the coated pigment obtained as in Example 1 ;s mixed with 76 parts of polyvinyl chlor-ide, 33 parts of dioctyl phthalate, 2 parts of dibutyltin dilaurate and 2 parts of titanium dioxide~ and the mixture is processed at 160C ;n a roll mill into a thin fil~
in the course of 15 minutesO The greenish yellow colour-ation thus produced is intense and fast to migration and light.
Example 10: 0.05 part of the coated pig~ent ob-tained as in Example 1 is mixed dry with 100 parts of poly-styrene. The mixture is kneaded at ~emperatures of betwPen 180 and 220C until it is homogeneously colouredO The coloured material is allowed to cool down and is ground in a mill do~n to a particle size of about 2-4 mm. The granulate thus obtained is processed at temperatures be tween 220 and 300C in an injection moulding machine ;nto mouldings~ The result ;s green;sh yellow materials of good light fastness and thermal stability~
~ : 60 parts of a 60X solution of a non-dry;ng aLkyd resin in xylene ~suppLied by the f;r~ of Reichold-Albert-5hemie, West Germany, under the tradena~e of Beckosol~ 27-320~ 36 parts of a 50X
strength solution of a melamine-formaldehyde resin in an alcohol-aromatics mixture (supplied by the firm of Reichold-Albert-Chemie under the tradename of Super-Beckami ~ 13-501), 2 parts of xyLene and 2 parts of methylcellosolve are mixed, and 100 parts of th;s m;xture are stirred by means of a st;rrer to give a homogeneous lacquer solution.
95 parts of the transparent lacquer thus obtained and 5 parts of the coated pigment as per Example 1 are ball milled for 72 hours. The coloured lacquer is then applied to sheet metal by a convent;onal spray;ng method and is baked thereon at 120C for 30 minutes. The result is a coating of good light fastnessO
After the precipitation the lead ion excess is 0.008 mole of Pb2~ per litre.
To coat the pigment particles the precipiate is then heated to 65C and a solution of ~ g of anhydrous sod;um sulfate in 120 ml of water is added. The pH is then adjusted to 2.5 with about 13 g of 52X
H~3 A solution of 32~5 g of sodium silicate t28% of SiO2) and 10 9 of sodium carbonate in 120 ml of water is then addedD followed by a solution of 10 g of anti-mono trioxide, 10 g of sodium fluoride and 27 g of 5ZX
strength HN03 in 120 ml of water. The end pH is ad-justed to 6.50 by adding about 8 9 of 100% so-dium hydroxide in 120 ml of water. The precipitate is fiLtered off, is washed w;th water to remove soluble salts~ and dried at a temperature of 90C.
Ratio of the lead salts: 57% PbCrO4 43% PbS0~
The values determined w;th the CAPA-500 analyser are:
Median value 0.40 ~m Particle size distribution: 64~ between 0~15 and 0.5 ~m.
The relative t;nctorial strength compared with a conventionally produced pigment of the same composi-tion was determined as 110% using the method ~-iven in DIN 53,235.
The proportion of the coat;ng ;n the total weight of the pigment is 7.4X.
The hue in paints ;s measured by DIN 53,235 is dist;nctly greeni 5 h~
~ : 0.6 part of the coated pigment obtained as in Example 1 ;s mixed with 76 parts of polyvinyl chlor-ide, 33 parts of dioctyl phthalate, 2 parts of dibutyltin dilaurate and 2 parts of titanium dioxide~ and the mixture is processed at 160C ;n a roll mill into a thin fil~
in the course of 15 minutesO The greenish yellow colour-ation thus produced is intense and fast to migration and light.
Example 10: 0.05 part of the coated pig~ent ob-tained as in Example 1 is mixed dry with 100 parts of poly-styrene. The mixture is kneaded at ~emperatures of betwPen 180 and 220C until it is homogeneously colouredO The coloured material is allowed to cool down and is ground in a mill do~n to a particle size of about 2-4 mm. The granulate thus obtained is processed at temperatures be tween 220 and 300C in an injection moulding machine ;nto mouldings~ The result ;s green;sh yellow materials of good light fastness and thermal stability~
~ : 60 parts of a 60X solution of a non-dry;ng aLkyd resin in xylene ~suppLied by the f;r~ of Reichold-Albert-5hemie, West Germany, under the tradena~e of Beckosol~ 27-320~ 36 parts of a 50X
strength solution of a melamine-formaldehyde resin in an alcohol-aromatics mixture (supplied by the firm of Reichold-Albert-Chemie under the tradename of Super-Beckami ~ 13-501), 2 parts of xyLene and 2 parts of methylcellosolve are mixed, and 100 parts of th;s m;xture are stirred by means of a st;rrer to give a homogeneous lacquer solution.
95 parts of the transparent lacquer thus obtained and 5 parts of the coated pigment as per Example 1 are ball milled for 72 hours. The coloured lacquer is then applied to sheet metal by a convent;onal spray;ng method and is baked thereon at 120C for 30 minutes. The result is a coating of good light fastnessO
Claims (12)
1. Monoclinic greenish lead chromate pigments con-taining lead chromate and lead sulfate in a weight ratio of 59.9:40.1 to 35:65, wherein the pigment particles have a median value of 0.3-0.4 µm and 63-78% by weight of all the particles have a Stokes diameter of 0.15-0.5 µm.
2. Lead chromate pigments according to claim 1, wherein the pigment particles have a median value of 0.3-0.4 µm and 65-72% by weight of all the particles have a Stokes diameter of 0.15-U.5 µm.
3. Lead chromate pigments according to claim 1, which additionally contain texture-improving and/or surface-active organic agents.
4. Lead chromate pigments obtainable by producing during the precipitation or in the course of an aftertreat-ment a coating of an inorganic coating agent on the lead chromate pigments according to claim 1.
5. Lead chromate pigments according to claim 4, which contain 2-40% of an inorganic coating agent.
6. Lead chromate pigments according to claim 4, which contain 2-20% of an inorganic coatins agent.
7. Lead chromate pigments according to claim 4, which contain 3-10% of an inorganic coating agent.
8. Process for preparing monoclinic lead chromate pigments according to claim 1, which comprises mixing an aqueous solution of a lead salt with an aqueous solution of a chromate and a sulfate under conditions of high turbulence.
9. Process according to claim 8, wherein the turbu-lence is created by high flow rates or mechanical stirring.
10. Process according to claim 8, wherein an excess of 0.003-0.06 mole of lead ions per litre over the stoichio-metric amount is present during the precipitation.
11. Process according to claim 8, wherein the pigments obtained are coated with an inorganic protective coating.
12. High molecular weight organic material which con tains a lead chromate pigment according to claim 1.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CH4419/83-6 | 1983-08-12 | ||
| CH441983 | 1983-08-12 | ||
| CH144/84-2 | 1984-01-12 | ||
| CH14484 | 1984-01-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1220006A true CA1220006A (en) | 1987-04-07 |
Family
ID=25683653
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000460696A Expired CA1220006A (en) | 1983-08-12 | 1984-08-10 | Monoclinic greenish lead chromate pigments |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0138753B1 (en) |
| BR (1) | BR8404027A (en) |
| CA (1) | CA1220006A (en) |
| DE (1) | DE3461293D1 (en) |
| ES (1) | ES8506336A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3579524D1 (en) * | 1984-07-25 | 1990-10-11 | Ciba Geigy Ag | ORTHORHOMBIC GREEN TURNED LEAD ROMATE PIGMENTS. |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1186203A (en) * | 1967-04-25 | 1970-04-02 | Chemokomplex Vegyipari Gep Es | Production of Inorganic Pigments. |
| FR1591327A (en) * | 1967-11-08 | 1970-04-27 |
-
1984
- 1984-08-06 DE DE8484810390T patent/DE3461293D1/en not_active Expired
- 1984-08-06 EP EP19840810390 patent/EP0138753B1/en not_active Expired
- 1984-08-10 CA CA000460696A patent/CA1220006A/en not_active Expired
- 1984-08-10 BR BR8404027A patent/BR8404027A/en unknown
- 1984-08-11 ES ES535106A patent/ES8506336A1/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| BR8404027A (en) | 1985-07-16 |
| ES535106A0 (en) | 1985-07-16 |
| ES8506336A1 (en) | 1985-07-16 |
| DE3461293D1 (en) | 1987-01-02 |
| EP0138753B1 (en) | 1986-11-12 |
| EP0138753A1 (en) | 1985-04-24 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |