CA1220004A - Monoclinic lead chromate pigments - Google Patents
Monoclinic lead chromate pigmentsInfo
- Publication number
- CA1220004A CA1220004A CA000460694A CA460694A CA1220004A CA 1220004 A CA1220004 A CA 1220004A CA 000460694 A CA000460694 A CA 000460694A CA 460694 A CA460694 A CA 460694A CA 1220004 A CA1220004 A CA 1220004A
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- lead
- lead chromate
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- chromate pigments
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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
3-14541/TEN/1+2/+
Monoclinic lead chromate pigments Abstract Monoclinic lead chromate pigments containing lead chromate and lead sulfate in a weight ratio of 89.9:10.1 to 60:40, wherein the pigment particles have a median value of 0.35-0.45 µm and 50-75% by weight of all the particles have a Stokes diameter of 0.15-0.5µm.
The pigments obtained are distinguished on appli-cation by low particle size, uniform particle size dis-tribution, high tinctorial strength, great hiding power, good rheological properties and high saturation.
Monoclinic lead chromate pigments Abstract Monoclinic lead chromate pigments containing lead chromate and lead sulfate in a weight ratio of 89.9:10.1 to 60:40, wherein the pigment particles have a median value of 0.35-0.45 µm and 50-75% by weight of all the particles have a Stokes diameter of 0.15-0.5µm.
The pigments obtained are distinguished on appli-cation by low particle size, uniform particle size dis-tribution, high tinctorial strength, great hiding power, good rheological properties and high saturation.
Description
- 1 ~ J~ 7 1 ~
The invention relates ~o monoclinic lead chro-mate pigments wh;ch are dist;ng~ished by a part;cularly high fineness of the pigment particLes and a narrow par-ticle size distribution.
; Lead chromate pigments have been widely used for many years for colouring plastics materials and paints.
Preferred pigments consist of small particles of little difference in size. US Patent 2,212,917 describes lead chromate pigments which, although distinguished by small average part;cLe s;ze ~for example 0.45 ~ m)~ conta;n ;nd;-vidual particles which can be up to 3.5 ~m long. German Offenlegungsschrift 1,807~8~1 describes coated Lead chro-mate pigments where at least 50X of the pigment particles have a particle size of at most 1.4 ~m and 10X have a par-t;cle ~ize of less than 4.1 /um or more. Even these pig- -ments leave a great deal to be desired in terms of the fine~
ness of the particles and the uniformity of particLe size~
The present invention providss monoclinic lead ; chromate pigments containiny lead chromate and lead sul-fate ;n a weight ratio of 89~9:1001 to 60:40, wherein the pig-ment particles have a median value of 0~35-0.45~m and 50-75X
of all the particLes have a Stokes diame~er of 0.15-0.5 ~m.
In preferred monoclinic lead chromate pi~ments the pigment particles have a median value of 0.35~0.45 ~m and 55-70% of all the particles have a Stokes diameter of 0.15-0~5Jum.
In particularly preferred monoclinic lead chromate pigment~ the pigment particles have a median valu of 0.3 0~4 ~m and 65-70æ of all the particles have a Stokes di~meter of .
~, ~L2~
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 ;f desired of a sulfate, for example sodium or potas-sium sulfate or ammonium sulfate~ under conditions of high turbulencea The chromate solution is advantageously pro-duced by adding alkali to a bichromate solution before or during the reaction with the lead salt.
The high turbulence can be produced ~y various means~
for example by cont;nuously comb;ning the solut;ons to be mixed in a mixing nozzle. Mixing nozzle is to be under-stood as meaning a device where the solutions to be mixed are combined with one another within a relatively small space to which at least one of the solutions is supplied by means o~f a nozzle and preferably under elevated pres-sure. The mixing nozzle can be constructed for example in accordance with the principle of the water jet pump, the way one of the liquids is fed into the mixing nozzle corresponding to the way the water is fed into the water jet pump and the way the other liqu;d is fed into the mixing nozzle corresponding to the connection between the water jet pump and the flask to be evacuated and if des;red this latter way of supplying liquid may also be effected under elevated pressure The precipitat;on ;n the m;x;ng nozzle ;s advan tageously carried out by continuousLy combining~ prefer-ab(y at room temperature, the aqueous solution contain;ng the chromate and the sulfate at a flow rate of at least 4.9 m/sec ~ith the aqueous solution of the lead salt at a flow rate of at le~st 0.08 m/sec. The prec;pitation is 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 producing high turbulence at the po;nt where the solutions are combined is available in the .~
~2~ f form of commercially available high-performance stirrers, such as, for example, the Ultra-Turrax stirrer from Janke und Kunkel KG, Staufen, West Germany, the ~stral stirrer from Ystral GmbH, Ballrechten~Do~tingen, West Germany, the Poly-tron from ~inematica~ Kriens-Lucerne, Switzerland, the Silverson stirrer from S;lverson Mach Ltd~, Chesham~
United Kingdom, or the Chemcol~mixer from Chemiecolor AG
Kilchberg-Z~r;ch, Switzerland. Other types of high-per formance stirrers which can likewise be used include in~er al;a the Pendraul;k~st;rrer from Pendraul;k Masch;nen und Apparate GmbH~ Bad M~nder am Deister, West Germany, and cont;nuous mixers such as those supplied by Gronfa Process Technik BV/Rozendaal, Netherlands~ It is important here that the lead salt solution on the one hand and the chromate and suLfate solution on the other are added as close as possiblP
to the shaft of the rotor of the high~performance stirrer.
The two main components can be mixed in the zone of turbu-lence either by feeding them in together or by adding one to the other~ In the first case, the solutions are passed into the immed;ate vicinity of the shaft of the rotor by two separate lines, with a chromate solu-tion and if desired also a sulfate solution advan-tageously in one line and a lead salt solution in the other. In the second case, for exarnple, the chromate solution and if used the sulfate 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 high-performance stirrer through a tube.
The prec;pitated pigment is distinguished by an extremely low particle size~ It has been found that bet-ter crystal structures are obtained if the precipitation is followed by a maturing process~ for example in the form of allo~ing the precipitate to stand at room temperature or by heating.
The pigment obtainPd can be treated with texture-improv;ng agents, for example long cha;n aliphatic alcohols, esters, acids or their salts, amines, amides, waxes or ~ I Aaf~C 1~'~
resinous subs~an~es, such as abi~tic acid, hydrogenation products, esters or salts thereof, and also non;on;c, an;onic or cationic surface-active agents.
To improve the stability to heat, light and chemi~al attack it is adva~tageous to coat the pigmen~
part;cles with an ;norganic coating agent dur;ng the pre-c;p;tat;on or ;n the course of an aftertreatmer,t in accor-dance with known processes descr;bed, for example, in US Patents 3,370,971, 3,639~133 and 4,046,588.
For th;s purpose, an ;norganic compound, for example an aluminium, sil;con, ant;mony, t;n, cerium, t;tan;um~ or zircon;um compound or comb;nat;ons thereof, ;s precip;tated on the p;gment. It has been found to be advantageous to use a cer;um-alumin;um-silicate layer wh;ch ;s formed on the pigmentO for example by add;ng an aqueous solution of cerium nitrate, of an alkali metal silicate and of aluminium sulfate to the aqueous pigment suspens;on.
The level of coating agent is advantageously
The invention relates ~o monoclinic lead chro-mate pigments wh;ch are dist;ng~ished by a part;cularly high fineness of the pigment particLes and a narrow par-ticle size distribution.
; Lead chromate pigments have been widely used for many years for colouring plastics materials and paints.
Preferred pigments consist of small particles of little difference in size. US Patent 2,212,917 describes lead chromate pigments which, although distinguished by small average part;cLe s;ze ~for example 0.45 ~ m)~ conta;n ;nd;-vidual particles which can be up to 3.5 ~m long. German Offenlegungsschrift 1,807~8~1 describes coated Lead chro-mate pigments where at least 50X of the pigment particles have a particle size of at most 1.4 ~m and 10X have a par-t;cle ~ize of less than 4.1 /um or more. Even these pig- -ments leave a great deal to be desired in terms of the fine~
ness of the particles and the uniformity of particLe size~
The present invention providss monoclinic lead ; chromate pigments containiny lead chromate and lead sul-fate ;n a weight ratio of 89~9:1001 to 60:40, wherein the pig-ment particles have a median value of 0~35-0.45~m and 50-75X
of all the particLes have a Stokes diame~er of 0.15-0.5 ~m.
In preferred monoclinic lead chromate pi~ments the pigment particles have a median value of 0.35~0.45 ~m and 55-70% of all the particles have a Stokes diameter of 0.15-0~5Jum.
In particularly preferred monoclinic lead chromate pigment~ the pigment particles have a median valu of 0.3 0~4 ~m and 65-70æ of all the particles have a Stokes di~meter of .
~, ~L2~
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 ;f desired of a sulfate, for example sodium or potas-sium sulfate or ammonium sulfate~ under conditions of high turbulencea The chromate solution is advantageously pro-duced by adding alkali to a bichromate solution before or during the reaction with the lead salt.
The high turbulence can be produced ~y various means~
for example by cont;nuously comb;ning the solut;ons to be mixed in a mixing nozzle. Mixing nozzle is to be under-stood as meaning a device where the solutions to be mixed are combined with one another within a relatively small space to which at least one of the solutions is supplied by means o~f a nozzle and preferably under elevated pres-sure. The mixing nozzle can be constructed for example in accordance with the principle of the water jet pump, the way one of the liquids is fed into the mixing nozzle corresponding to the way the water is fed into the water jet pump and the way the other liqu;d is fed into the mixing nozzle corresponding to the connection between the water jet pump and the flask to be evacuated and if des;red this latter way of supplying liquid may also be effected under elevated pressure The precipitat;on ;n the m;x;ng nozzle ;s advan tageously carried out by continuousLy combining~ prefer-ab(y at room temperature, the aqueous solution contain;ng the chromate and the sulfate at a flow rate of at least 4.9 m/sec ~ith the aqueous solution of the lead salt at a flow rate of at le~st 0.08 m/sec. The prec;pitation is 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 producing high turbulence at the po;nt where the solutions are combined is available in the .~
~2~ f form of commercially available high-performance stirrers, such as, for example, the Ultra-Turrax stirrer from Janke und Kunkel KG, Staufen, West Germany, the ~stral stirrer from Ystral GmbH, Ballrechten~Do~tingen, West Germany, the Poly-tron from ~inematica~ Kriens-Lucerne, Switzerland, the Silverson stirrer from S;lverson Mach Ltd~, Chesham~
United Kingdom, or the Chemcol~mixer from Chemiecolor AG
Kilchberg-Z~r;ch, Switzerland. Other types of high-per formance stirrers which can likewise be used include in~er al;a the Pendraul;k~st;rrer from Pendraul;k Masch;nen und Apparate GmbH~ Bad M~nder am Deister, West Germany, and cont;nuous mixers such as those supplied by Gronfa Process Technik BV/Rozendaal, Netherlands~ It is important here that the lead salt solution on the one hand and the chromate and suLfate solution on the other are added as close as possiblP
to the shaft of the rotor of the high~performance stirrer.
The two main components can be mixed in the zone of turbu-lence either by feeding them in together or by adding one to the other~ In the first case, the solutions are passed into the immed;ate vicinity of the shaft of the rotor by two separate lines, with a chromate solu-tion and if desired also a sulfate solution advan-tageously in one line and a lead salt solution in the other. In the second case, for exarnple, the chromate solution and if used the sulfate 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 high-performance stirrer through a tube.
The prec;pitated pigment is distinguished by an extremely low particle size~ It has been found that bet-ter crystal structures are obtained if the precipitation is followed by a maturing process~ for example in the form of allo~ing the precipitate to stand at room temperature or by heating.
The pigment obtainPd can be treated with texture-improv;ng agents, for example long cha;n aliphatic alcohols, esters, acids or their salts, amines, amides, waxes or ~ I Aaf~C 1~'~
resinous subs~an~es, such as abi~tic acid, hydrogenation products, esters or salts thereof, and also non;on;c, an;onic or cationic surface-active agents.
To improve the stability to heat, light and chemi~al attack it is adva~tageous to coat the pigmen~
part;cles with an ;norganic coating agent dur;ng the pre-c;p;tat;on or ;n the course of an aftertreatmer,t in accor-dance with known processes descr;bed, for example, in US Patents 3,370,971, 3,639~133 and 4,046,588.
For th;s purpose, an ;norganic compound, for example an aluminium, sil;con, ant;mony, t;n, cerium, t;tan;um~ or zircon;um compound or comb;nat;ons thereof, ;s precip;tated on the p;gment. It has been found to be advantageous to use a cer;um-alumin;um-silicate layer wh;ch ;s formed on the pigmentO for example by add;ng an aqueous solution of cerium nitrate, of an alkali metal silicate and of aluminium sulfate to the aqueous pigment suspens;on.
The level of coating agent is advantageously
2-~0, preferably 2-20 and in particular 3-10% based on the total weight of the pigment~
The pigment is ~orked up in conventional manner, for example by filtering it off, wash;ng the filter cake with water to remove soluble salts, drying and pulverising.
The median value Dz (see DIN 53,206 sheet 1, August 1972, page b) and the particle size distribution can be determined by known methods, for example by means of a disc centrifuge Csee The Particle Size Determination of P;gments with the Disc Centrifuge~ K. Brugger, Powder Technology 13 S1976), 215~221~u Median value and par-ticle s;ze d;stribution can be determined in a particu larly simple manner using 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 distributions~
The determined values also hold for p;gments containing up to 10X of coating material.
~ 5 --The tinctorial strength was determined using a pro-gram based on DIN 53,235 and an 8/d angle of measure~
ment.
Electron m;crographs of the p;gm2nts obtained clearly show the great advantages of these pigments~ Two characterist;c main features stick out. The particles prepared are smaller and more uniform than those of tra~
ditional products. The pigments obtained are dis-t;ngu;shed on application by higher tinctorial strength, a more greenish shade, great hid;ng power, good rheological properties and higher saturation~ Noteworthy is also the lower proport;on of lead sal~s soluble in dilute acids, such as carbonate and sulfate salts9 compared with known products of ~he same hue.
In the case of pigments containing more than 10X
of coating ma~erial, the median value and the particle size distribution can change so much that they are no longer within the r3nge defined above. Even such pigments have said applicat;on advantages of higher tinctoriaL strength and saturat;on, a more greenish hue and greater hiding power over conventionally obtained pigments, as described ;n, for example, US Patent 4,046,58~9 containing the same proportion of coating ma~erial.
The pigments according to the invention can be used alone or mixed uith one another or with other pigments~
~or e~ample phthalocyanine blue, molybdate orange or Berlin blue, for pig-ment;ng h;gh molecular weight organic material, for example celluLose ethers and esters~ acetylcellulose, ni~rocellu-lose, natural resins or synthetic resins~ such as polymer isation or condensation resins~ for example aminoplasts, in particular urea- and melamine-formaldehyde resins, alkyd resins, phenoplasts, polycarbonates, polyolefins~
such as polyethylene or polypropylene, as well as polysty-rene, polyvinyl chloride, polyacrylonitrile~ polyacrylates, rubber, case;n, silicone and silicone resins~
Said high molecular weight compounds can be not only in the form of amorphous materials or melts but also in the form oE spinning solutions, ]acquers or prin-ting inks.
Depending on the intended use, it has been found to be advantag-eous to use the new pigments as toners or in the form of prepar-ations.
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 CAPA-500 analyser at 3000 rpm. The amount of pigment must be so adjusted, that the absorption of the beam is between 0.5 and 1Ø
The pigments were dispersed as follows: 15 mg of pigment are thoroughly wetted by means of 100 mg of Teepo ~ HB5 (34~ strength solution of the sodium salt of a sulEated primary alcohol having an average molecular weight of 267, supplied by Shell) in a mortar. To the so obtained dispersion is added in a 250 ml conical flask a total amount of 100 ml of distilled water.
Then the flask is put at room temperature for 10 min on the bottom of an ultrasonic bath (Bransonic 48 kHz from Bransonic B.V., Soest, Netherlands~ filled with 1 litre of water.
In the following Examples reference is made to the attached drawings in which:
Figure 1 represents a suitable mixing nozzle;
Figure 2 represents an electron micrograph (20,000x) of the pigment particles 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.
~22~
- 6a -Example 1: In a mixiny nozzle (see Figure 1), an aqueous solution containing, per 1,000 parts by volume, 40.2 parts oE sodium bichromate x 2H2O, 19.35 parts of sodium sulfate and 11.25 parts of 100% sodium hydroxide, is passed at room temperature through tube a at a flow rate of 4.9 m/sec and is continuously brought together a-t the same time with an aqueous solution containing, per 1,000 parts by volume, l~L6 parts of lead nitrate and 2 parts of sodium carbonate 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 precipi-tate 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 mixed crystal: 66% PbCrO~
34% PbS04 The values determined with the CAPA-500 analyser are:
median value: 0.37~um;
Particle size distribution: o6% between 0.15 and 0~5 ~m.
The relative tinctorial strength compared to pigment of identical composition obtained by a conven-tional process was found to be 115X using the method of DIN 53,Z35.
Example 2: In a mixing nozzle (see Figure 1), an aqueous solu~ion containing~ per 1~000 parts by ~o-lume, 40.2 parts of sodium bichroma~e x 2H~0, 19~35 parts of sodium sulfate and 11.2S parts of 100%
sod;um hydrox;de, ;s passed a~ room temperature through tube a at a flow rate of 4.9 m/sec and ;s cont;nuously brought together at ~he same t;me w;th an aqueous solu-t;on conta;n;ng, per 1,000 parts by volume~ 146 parts of lead nitrate and 2 parts of sodium carbonate and passing through tube b at a flow rate of 0.08 m/sec. The supply of the soluticns is controlled in such a way that, during the precipitation, there is always present an ex-cess of lead ions of 0~003 mole per litre over the stoichiometric amount. The resultin~ pigment suspension leaves the nozzle via tube CA After the precipitation a solution of 22~5 parts of sodium chloride in 12D parts of water 1s added in order to control the crystal size~
and the suspensisn is brought to pH 5 by adding an aqueous sodium carbonate solution. To ~ature the crystal structure the precipitate is alLowed to settle for 8 hours~ The supernatant liquid above the precipi~a~e is decanted off~ and then~ ~o coat the pigment particles of the pigment suspens;on left behind, the follow;ng are added at room temperature w;th st;rring: a solution of 13 parts of sodium s;l;cate (Z8X of S;02~ in 120 parts of water, followed by a solution of 20 parts of alu-minium sulfate x 18H20 and 10 parts of 52%
n;tric acid in 300 parts of water, and then a solution o~
of 1.~ parts of cer;um hydrox;de ;n 3.7 parts 52% nitric acid. The end pH is adjusted to 4a5 by adding 12~5 parts of sod;um carbonate in 120 parts of water.
The pigment obtained is isolated in the custo mary manner by filtering, washed with water to remove soluble saLts~ and dried at 80-90C.
Rat;o of the lead salts in the mixed crystal: 66% PbCrO4 34% PbS04 The values determined with the CAPA-500 analyser are:
med;an value: 0~42 ~m particle size distr;bution 56X between 0.15 and 0.5 ~ m.
Proportion of the coating in the total wei~ht of the p;gment: 5.5%.
The rela~ive tinctorial strength in paints com-pared w;th a conventionally obtained pigment of the same composition was found to be 123% us;ng the method given in DIN 53,235.
Figure 2 sho~s an electron micrograph taken with Z0,000-fold enlargement of the pigment particles ultra~
sonically d;spersed in an alcohol~water mixture.
The hue in pa;nts as measured by DIN 53,235 is distinctly greenish.
~ : Example 1 is repeated to produce a pigment conta;ning 73% of PbCrO4 and 27% of PbS0 affording a pigment having a relative ~inctorial strength of 14D% compared with a conventionally obta;ned pigment of the same hue.
median value: 0.41 ~m partic~e size distribution: 59% between 0.15 and 0~5 ~m.
~ : In a mix;ng nozzle (see Figure 1), an aqueous solution containing, per 1~000 parts by vo-lumeD 40.2 parts of sod;um b;chromate x 2H20, 19.35 parts of sodium sulfate and 11.25 parts of 100X
sodium hydroxide, is passed at room temperature through tube _ at a flow rate of 4.9 ~/sec and is continuously brought together at the same time with an aqueous solu-:, z~
tion containillg, per 1,000 parts by volumeO 157.6 partsof lead nitrate and 2 parts of sodium carbonate and passing through tube b at a flow rate of 0.08 m/sec.
The supply of the solutions is controlled in such a way that, during ~he precipitation, there is always present an excess of lead ions of 0~014 mole per litre over the stoichiometric amount.
After the precipitation a solution of 22.5 parts of sodium chloride in 1~0 parts of water is added in order to control the crystal size, and the suspension is brought to pH 5n~ by adding an aqueous sodium carbonate solutionn To mature the crystal structure the precipitate îs allowed to settle for 8 hours~
The supernatant l;quid above the precipitate is decanted off, and ~hen, to coat ~he pigment particles of the p;gment suspension left behind~ the folLowing are added at room temperature with stirring: a solution of 13 parts of sodium silicate ~8% of siO23 in 120 parts of water, followed by a solution of 20 parts of alumin;um sulfate x 18H20 and 10 parts of 52%
n;tr;c ac;d and 300 parts of water, and then a solution of 1L4 parts of cerium hydroxide in 3.7 parts of 52%
strength nitric acid~ The end p~ is adjusted to 4.5 by addin~ 12.5 parts of sod;um carbonate in 120 parts of water~ The pigment obtained is isolated in the customary manner by filtering, washed with ~ater to remove soluble salts, and dried at 80-9DC~
Ratio of the lead salts in the mixed crystal 64X PbCrO4 36X PbS04 Median value: 0.38 ~m Particle size distr;but;on: 65~4% between 0u15 and 0.5 ~m.
Proport;on of the coating in the total weight of the pigment: 5.4%.
The relative tinctorial strength is 110X com-pared with a conventionally produced pigment of the same composition.
The hue in paints as measured by DIN 53,235 is s;gnilf;cantly more greenish than that of known pigments of the same composition~
Figure 3 shows an electron micrograph of the pigment dispers;on ;n 20,000 fold enlargament.
Example 5: In a mixing nozzle (see F;gure 1) an aqueous soLution conta;n;ng per 1,000 parts by volume 40.2 parts of sodium bichromate tNa2Cr207 x 2H20)~
19~35 parts of anhydrous sodium sulfate and 11~25 parts of 100% sodium hydrox;de ;s passed at room tem pera~ure through tube a at a flow rate of 4.9 m/sec and is continuously brought together at the same time with an aqueous soLution containing per 1~000 parts by volume 14h par~s of lead nitrate in 2 par~s of sodium car-bonate and pass;ng through tube b at a flow rate of 0~08 mlsec. The supply of the soLutions is controlled in such a way that, during the precip;tation, there is al-ways present an excess of lead ions of 0.003 mole per litre over the stoichiometric amount. After the preci-pitat;on a solution o; 22.5 parts of sodium carbon chlo ride in 12Q parts of water is added in order to control the crystal size, ~nd the pH ;s then adjusted to 5.~
by adding an aqueous sod;um carbonate solution. To ma-ture the crystal structure the precipiate is allowed to settle for 8 hours.
To coat the pigmen~ particles the supernatant liquid above the precipitate is decanted oFf and 95 parts of sodium sil;cate (28X of SiO2~ in 200 parts of water are then added at room temperature with stir-ring to the suspension left behind~ This is followed~
likewise at room temperature w;th stirring, by a solu-t~on of 20 parts of aluminium sulfate x 18H20 and 35 parts of 52% HN03 in 300 parts o~f water and then by a solution of 1~4 parts of cerium hydroxide in ~Z~
The pigment is ~orked up in conventional manner, for example by filtering it off, wash;ng the filter cake with water to remove soluble salts, drying and pulverising.
The median value Dz (see DIN 53,206 sheet 1, August 1972, page b) and the particle size distribution can be determined by known methods, for example by means of a disc centrifuge Csee The Particle Size Determination of P;gments with the Disc Centrifuge~ K. Brugger, Powder Technology 13 S1976), 215~221~u Median value and par-ticle s;ze d;stribution can be determined in a particu larly simple manner using 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 distributions~
The determined values also hold for p;gments containing up to 10X of coating material.
~ 5 --The tinctorial strength was determined using a pro-gram based on DIN 53,235 and an 8/d angle of measure~
ment.
Electron m;crographs of the p;gm2nts obtained clearly show the great advantages of these pigments~ Two characterist;c main features stick out. The particles prepared are smaller and more uniform than those of tra~
ditional products. The pigments obtained are dis-t;ngu;shed on application by higher tinctorial strength, a more greenish shade, great hid;ng power, good rheological properties and higher saturation~ Noteworthy is also the lower proport;on of lead sal~s soluble in dilute acids, such as carbonate and sulfate salts9 compared with known products of ~he same hue.
In the case of pigments containing more than 10X
of coating ma~erial, the median value and the particle size distribution can change so much that they are no longer within the r3nge defined above. Even such pigments have said applicat;on advantages of higher tinctoriaL strength and saturat;on, a more greenish hue and greater hiding power over conventionally obtained pigments, as described ;n, for example, US Patent 4,046,58~9 containing the same proportion of coating ma~erial.
The pigments according to the invention can be used alone or mixed uith one another or with other pigments~
~or e~ample phthalocyanine blue, molybdate orange or Berlin blue, for pig-ment;ng h;gh molecular weight organic material, for example celluLose ethers and esters~ acetylcellulose, ni~rocellu-lose, natural resins or synthetic resins~ such as polymer isation or condensation resins~ for example aminoplasts, in particular urea- and melamine-formaldehyde resins, alkyd resins, phenoplasts, polycarbonates, polyolefins~
such as polyethylene or polypropylene, as well as polysty-rene, polyvinyl chloride, polyacrylonitrile~ polyacrylates, rubber, case;n, silicone and silicone resins~
Said high molecular weight compounds can be not only in the form of amorphous materials or melts but also in the form oE spinning solutions, ]acquers or prin-ting inks.
Depending on the intended use, it has been found to be advantag-eous to use the new pigments as toners or in the form of prepar-ations.
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 CAPA-500 analyser at 3000 rpm. The amount of pigment must be so adjusted, that the absorption of the beam is between 0.5 and 1Ø
The pigments were dispersed as follows: 15 mg of pigment are thoroughly wetted by means of 100 mg of Teepo ~ HB5 (34~ strength solution of the sodium salt of a sulEated primary alcohol having an average molecular weight of 267, supplied by Shell) in a mortar. To the so obtained dispersion is added in a 250 ml conical flask a total amount of 100 ml of distilled water.
Then the flask is put at room temperature for 10 min on the bottom of an ultrasonic bath (Bransonic 48 kHz from Bransonic B.V., Soest, Netherlands~ filled with 1 litre of water.
In the following Examples reference is made to the attached drawings in which:
Figure 1 represents a suitable mixing nozzle;
Figure 2 represents an electron micrograph (20,000x) of the pigment particles 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.
~22~
- 6a -Example 1: In a mixiny nozzle (see Figure 1), an aqueous solution containing, per 1,000 parts by volume, 40.2 parts oE sodium bichromate x 2H2O, 19.35 parts of sodium sulfate and 11.25 parts of 100% sodium hydroxide, is passed at room temperature through tube a at a flow rate of 4.9 m/sec and is continuously brought together a-t the same time with an aqueous solution containing, per 1,000 parts by volume, l~L6 parts of lead nitrate and 2 parts of sodium carbonate 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 precipi-tate 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 mixed crystal: 66% PbCrO~
34% PbS04 The values determined with the CAPA-500 analyser are:
median value: 0.37~um;
Particle size distribution: o6% between 0.15 and 0~5 ~m.
The relative tinctorial strength compared to pigment of identical composition obtained by a conven-tional process was found to be 115X using the method of DIN 53,Z35.
Example 2: In a mixing nozzle (see Figure 1), an aqueous solu~ion containing~ per 1~000 parts by ~o-lume, 40.2 parts of sodium bichroma~e x 2H~0, 19~35 parts of sodium sulfate and 11.2S parts of 100%
sod;um hydrox;de, ;s passed a~ room temperature through tube a at a flow rate of 4.9 m/sec and ;s cont;nuously brought together at ~he same t;me w;th an aqueous solu-t;on conta;n;ng, per 1,000 parts by volume~ 146 parts of lead nitrate and 2 parts of sodium carbonate and passing through tube b at a flow rate of 0.08 m/sec. The supply of the soluticns is controlled in such a way that, during the precipitation, there is always present an ex-cess of lead ions of 0~003 mole per litre over the stoichiometric amount. The resultin~ pigment suspension leaves the nozzle via tube CA After the precipitation a solution of 22~5 parts of sodium chloride in 12D parts of water 1s added in order to control the crystal size~
and the suspensisn is brought to pH 5 by adding an aqueous sodium carbonate solution. To ~ature the crystal structure the precipitate is alLowed to settle for 8 hours~ The supernatant liquid above the precipi~a~e is decanted off~ and then~ ~o coat the pigment particles of the pigment suspens;on left behind, the follow;ng are added at room temperature w;th st;rring: a solution of 13 parts of sodium s;l;cate (Z8X of S;02~ in 120 parts of water, followed by a solution of 20 parts of alu-minium sulfate x 18H20 and 10 parts of 52%
n;tric acid in 300 parts of water, and then a solution o~
of 1.~ parts of cer;um hydrox;de ;n 3.7 parts 52% nitric acid. The end pH is adjusted to 4a5 by adding 12~5 parts of sod;um carbonate in 120 parts of water.
The pigment obtained is isolated in the custo mary manner by filtering, washed with water to remove soluble saLts~ and dried at 80-90C.
Rat;o of the lead salts in the mixed crystal: 66% PbCrO4 34% PbS04 The values determined with the CAPA-500 analyser are:
med;an value: 0~42 ~m particle size distr;bution 56X between 0.15 and 0.5 ~ m.
Proportion of the coating in the total wei~ht of the p;gment: 5.5%.
The rela~ive tinctorial strength in paints com-pared w;th a conventionally obtained pigment of the same composition was found to be 123% us;ng the method given in DIN 53,235.
Figure 2 sho~s an electron micrograph taken with Z0,000-fold enlargement of the pigment particles ultra~
sonically d;spersed in an alcohol~water mixture.
The hue in pa;nts as measured by DIN 53,235 is distinctly greenish.
~ : Example 1 is repeated to produce a pigment conta;ning 73% of PbCrO4 and 27% of PbS0 affording a pigment having a relative ~inctorial strength of 14D% compared with a conventionally obta;ned pigment of the same hue.
median value: 0.41 ~m partic~e size distribution: 59% between 0.15 and 0~5 ~m.
~ : In a mix;ng nozzle (see Figure 1), an aqueous solution containing, per 1~000 parts by vo-lumeD 40.2 parts of sod;um b;chromate x 2H20, 19.35 parts of sodium sulfate and 11.25 parts of 100X
sodium hydroxide, is passed at room temperature through tube _ at a flow rate of 4.9 ~/sec and is continuously brought together at the same time with an aqueous solu-:, z~
tion containillg, per 1,000 parts by volumeO 157.6 partsof lead nitrate and 2 parts of sodium carbonate and passing through tube b at a flow rate of 0.08 m/sec.
The supply of the solutions is controlled in such a way that, during ~he precipitation, there is always present an excess of lead ions of 0~014 mole per litre over the stoichiometric amount.
After the precipitation a solution of 22.5 parts of sodium chloride in 1~0 parts of water is added in order to control the crystal size, and the suspension is brought to pH 5n~ by adding an aqueous sodium carbonate solutionn To mature the crystal structure the precipitate îs allowed to settle for 8 hours~
The supernatant l;quid above the precipitate is decanted off, and ~hen, to coat ~he pigment particles of the p;gment suspension left behind~ the folLowing are added at room temperature with stirring: a solution of 13 parts of sodium silicate ~8% of siO23 in 120 parts of water, followed by a solution of 20 parts of alumin;um sulfate x 18H20 and 10 parts of 52%
n;tr;c ac;d and 300 parts of water, and then a solution of 1L4 parts of cerium hydroxide in 3.7 parts of 52%
strength nitric acid~ The end p~ is adjusted to 4.5 by addin~ 12.5 parts of sod;um carbonate in 120 parts of water~ The pigment obtained is isolated in the customary manner by filtering, washed with ~ater to remove soluble salts, and dried at 80-9DC~
Ratio of the lead salts in the mixed crystal 64X PbCrO4 36X PbS04 Median value: 0.38 ~m Particle size distr;but;on: 65~4% between 0u15 and 0.5 ~m.
Proport;on of the coating in the total weight of the pigment: 5.4%.
The relative tinctorial strength is 110X com-pared with a conventionally produced pigment of the same composition.
The hue in paints as measured by DIN 53,235 is s;gnilf;cantly more greenish than that of known pigments of the same composition~
Figure 3 shows an electron micrograph of the pigment dispers;on ;n 20,000 fold enlargament.
Example 5: In a mixing nozzle (see F;gure 1) an aqueous soLution conta;n;ng per 1,000 parts by volume 40.2 parts of sodium bichromate tNa2Cr207 x 2H20)~
19~35 parts of anhydrous sodium sulfate and 11~25 parts of 100% sodium hydrox;de ;s passed at room tem pera~ure through tube a at a flow rate of 4.9 m/sec and is continuously brought together at the same time with an aqueous soLution containing per 1~000 parts by volume 14h par~s of lead nitrate in 2 par~s of sodium car-bonate and pass;ng through tube b at a flow rate of 0~08 mlsec. The supply of the soLutions is controlled in such a way that, during the precip;tation, there is al-ways present an excess of lead ions of 0.003 mole per litre over the stoichiometric amount. After the preci-pitat;on a solution o; 22.5 parts of sodium carbon chlo ride in 12Q parts of water is added in order to control the crystal size, ~nd the pH ;s then adjusted to 5.~
by adding an aqueous sod;um carbonate solution. To ma-ture the crystal structure the precipiate is allowed to settle for 8 hours.
To coat the pigmen~ particles the supernatant liquid above the precipitate is decanted oFf and 95 parts of sodium sil;cate (28X of SiO2~ in 200 parts of water are then added at room temperature with stir-ring to the suspension left behind~ This is followed~
likewise at room temperature w;th stirring, by a solu-t~on of 20 parts of aluminium sulfate x 18H20 and 35 parts of 52% HN03 in 300 parts o~f water and then by a solution of 1~4 parts of cerium hydroxide in ~Z~
3.7 parts of 52% strength HN03.
The end pH is adjusted to 4.S by add;ng 12.S
parts of sodium carbonate in 120 parts of water, and the result;ng precip;tate is filtered off, washed w;th water to remove soluble salts, and dr;ed at 80-90C.
Ratio of the lead salts in the m;xed crystal: 68X PbCrO4 32% PbS0~
Proport;on of the coat;ng in the total we;ght of the pigment: 19X.
The relative tinctorial strength is 14~% com-pared with a conventionaLly produced pigment of the same composition.
~ 1,000 ml of an aqueous solution con-ta;ning 40.2 9 of sodium bichromate x 2H20, 19.35 9 of ssdium sulfate and 11025 9 of 100X sodium hy-droxide and 1,000 mL of an aqueous solution containing 146 9 of lead n;trate and 2 9 of sodium carbonate are con~lnuously and simultaneously brought together at room temperature in separate tubes and in the immediate vici-nity of the shaft of the rotor of a high-performance stirrer (diameter of the rotor 4 cm, circumferential speed of the rotor 4 m/sec~ ;n a 5 l;tre reaction vessel in the course of 2 minutes~ The supply of the solution is controlled ;n such a way that, dur;ng the precipitat;on, there is always present an excess of lead ions of o~nO3 mole per litre over the stoichiometric amountO After the prec;p;tation a solution of 22.5 g of sodium chloride in 120 ml of water is added in order to control the crystal size~ and the pH is adjusted to 5.8 by adding aqueous sod;um carbonate solution. To mature the crystal structure the precipitate is allowed to settle for 8 hours.
To coat the pigment particles the supernatant l;qu;d above the precipitate is decanted off and the followin~ are added at room temperature with stirring to the suspension left behind~ a solution of 13 9 of so-dium silicate (28% of SiO2) in 120 ml of water, fol-~2~
lowed by a solution of 20 9 of aluminium sulfate x18H20 and 10 9 of 52% nitric acid in 300 ml of water~ and then a solution of 1.4 9 of cerium hy~
droxide in 3.7 g of 52% nitric acid~ The end pH ;s adjusted ~o 4.5 by adding 12.5 g of sod;um carbo~
nate in 120 ml of waterr The pigment obtained is isolated in conYentional manner by filtrat;on, is washed w;th water to remove soluble salts, and is dried at 80-90C.
Ratio of the lead salts in the mixed crystals: 66~ PbCrO4 34% PbS0 Median value: 0.37 ~m Particle size distribution: 66% between Oa15 and Do5 ~m Proport;on of the coating in the total weight of the pi3ment~ 501%.
The relative tinctorial strength is 147X com~
pared with a conventionally produced pigment of the same composit;on.
Figure 4 shows an electron Inicrograph of ~he pigments in 20~000-fold enlargement.
The hue in paints as measured by DIN 53,235 is significantly more greenish than in the case of known pigments having the same lead chromate content~
~ : 1,000 ml of an aqueous solution containing 139 ~ of lead n;trate and 1~7 g of sodium carbonate are introduced into an empty 5 litre reaction vessel equipped with a high performance stirrer (diame-ter of the rotor: 4 cm; circumferential speed of the rotor: 4 m/sec). 1,000 ml of an aqueous solution con-ta;n;ng 63.6 g of sodium bichromate x 2H20, 3.4 9 of anhydrous sodium sulfa'ce and 17.1 9 of 10D%
sodium hydroxide are then added at room temperature in the immed;ate vicinity of the shaft of the rotor of the h;gh-performance stirrer by means of a glass tube in the course of 2 minutes. After the precipitation lead ions are present in an excess of O.Oû9 mole per litre~ In order to control ~he crystal si~e a solut;on of Z5 g of sodium chloride in 120 ml of water is added. The pH
is then adjusted to 5.8 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 precipitate is decanted off and a solu-t;on of 35.7 g of aluminium sulfate x 18H20 and 30 g of titanium oxychloride in 200 ml of water ;s added at room temperature with stirring ~co the suspension left beh;nd. 2.6 9 of cer;um hydroxide in 7.8 g of 52%
strength HN03 are then added. The end pH is then ad-justed to 5.0 by adding ~0 9 of ~od;um carbonate in 2UO ml of water. The precipitate is filtered o~f~
washed with water to remove soluble salts~ and dried at a temperature of 80-90C.
Ratio of the lead salts in the mixed crystals: B5~ PbCrO4 15% PbS04 Proportion of the coating in the total weight of the pigment: 9X.
The relative tinctorial strength is 134X com pared with a conventionally produced p;gment.
The values determined with the CAPA-500 analyser are:
Median value 0.33 ~m Particle size distribution: 58% between 0.15 and 0.5 ~m.
The hue in paints as measured by DIN 53,235 is distinctly ~reen;sh~
Example 8: 1,000 ml of an aqueous solution con-taining 273 g of lead nitrate and 2.5 9 of sodium carbo nate are introduced in'co an empty 5 litre reaction ves-sel equipped with a high-performance stirrer (d;ameter of the rotor 4 cm, circumferential speed of the rotor
The end pH is adjusted to 4.S by add;ng 12.S
parts of sodium carbonate in 120 parts of water, and the result;ng precip;tate is filtered off, washed w;th water to remove soluble salts, and dr;ed at 80-90C.
Ratio of the lead salts in the m;xed crystal: 68X PbCrO4 32% PbS0~
Proport;on of the coat;ng in the total we;ght of the pigment: 19X.
The relative tinctorial strength is 14~% com-pared with a conventionaLly produced pigment of the same composition.
~ 1,000 ml of an aqueous solution con-ta;ning 40.2 9 of sodium bichromate x 2H20, 19.35 9 of ssdium sulfate and 11025 9 of 100X sodium hy-droxide and 1,000 mL of an aqueous solution containing 146 9 of lead n;trate and 2 9 of sodium carbonate are con~lnuously and simultaneously brought together at room temperature in separate tubes and in the immediate vici-nity of the shaft of the rotor of a high-performance stirrer (diameter of the rotor 4 cm, circumferential speed of the rotor 4 m/sec~ ;n a 5 l;tre reaction vessel in the course of 2 minutes~ The supply of the solution is controlled ;n such a way that, dur;ng the precipitat;on, there is always present an excess of lead ions of o~nO3 mole per litre over the stoichiometric amountO After the prec;p;tation a solution of 22.5 g of sodium chloride in 120 ml of water is added in order to control the crystal size~ and the pH is adjusted to 5.8 by adding aqueous sod;um carbonate solution. To mature the crystal structure the precipitate is allowed to settle for 8 hours.
To coat the pigment particles the supernatant l;qu;d above the precipitate is decanted off and the followin~ are added at room temperature with stirring to the suspension left behind~ a solution of 13 9 of so-dium silicate (28% of SiO2) in 120 ml of water, fol-~2~
lowed by a solution of 20 9 of aluminium sulfate x18H20 and 10 9 of 52% nitric acid in 300 ml of water~ and then a solution of 1.4 9 of cerium hy~
droxide in 3.7 g of 52% nitric acid~ The end pH ;s adjusted ~o 4.5 by adding 12.5 g of sod;um carbo~
nate in 120 ml of waterr The pigment obtained is isolated in conYentional manner by filtrat;on, is washed w;th water to remove soluble salts, and is dried at 80-90C.
Ratio of the lead salts in the mixed crystals: 66~ PbCrO4 34% PbS0 Median value: 0.37 ~m Particle size distribution: 66% between Oa15 and Do5 ~m Proport;on of the coating in the total weight of the pi3ment~ 501%.
The relative tinctorial strength is 147X com~
pared with a conventionally produced pigment of the same composit;on.
Figure 4 shows an electron Inicrograph of ~he pigments in 20~000-fold enlargement.
The hue in paints as measured by DIN 53,235 is significantly more greenish than in the case of known pigments having the same lead chromate content~
~ : 1,000 ml of an aqueous solution containing 139 ~ of lead n;trate and 1~7 g of sodium carbonate are introduced into an empty 5 litre reaction vessel equipped with a high performance stirrer (diame-ter of the rotor: 4 cm; circumferential speed of the rotor: 4 m/sec). 1,000 ml of an aqueous solution con-ta;n;ng 63.6 g of sodium bichromate x 2H20, 3.4 9 of anhydrous sodium sulfa'ce and 17.1 9 of 10D%
sodium hydroxide are then added at room temperature in the immed;ate vicinity of the shaft of the rotor of the h;gh-performance stirrer by means of a glass tube in the course of 2 minutes. After the precipitation lead ions are present in an excess of O.Oû9 mole per litre~ In order to control ~he crystal si~e a solut;on of Z5 g of sodium chloride in 120 ml of water is added. The pH
is then adjusted to 5.8 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 precipitate is decanted off and a solu-t;on of 35.7 g of aluminium sulfate x 18H20 and 30 g of titanium oxychloride in 200 ml of water ;s added at room temperature with stirring ~co the suspension left beh;nd. 2.6 9 of cer;um hydroxide in 7.8 g of 52%
strength HN03 are then added. The end pH is then ad-justed to 5.0 by adding ~0 9 of ~od;um carbonate in 2UO ml of water. The precipitate is filtered o~f~
washed with water to remove soluble salts~ and dried at a temperature of 80-90C.
Ratio of the lead salts in the mixed crystals: B5~ PbCrO4 15% PbS04 Proportion of the coating in the total weight of the pigment: 9X.
The relative tinctorial strength is 134X com pared with a conventionally produced p;gment.
The values determined with the CAPA-500 analyser are:
Median value 0.33 ~m Particle size distribution: 58% between 0.15 and 0.5 ~m.
The hue in paints as measured by DIN 53,235 is distinctly ~reen;sh~
Example 8: 1,000 ml of an aqueous solution con-taining 273 g of lead nitrate and 2.5 9 of sodium carbo nate are introduced in'co an empty 5 litre reaction ves-sel equipped with a high-performance stirrer (d;ameter of the rotor 4 cm, circumferential speed of the rotor
4 mlsec). 1,000 ml of an aqueous soLution containing 96.5 9 of sodium bichromate x 2H20, 20~2 9 of anhy-drous sodium sulfate and 26.2 9 of 1DOX sodium~
- 14 _ hydroxide are then added in the ;mmediate v;cinity 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 S g of anhydrous sodium sulfate in 120 ml of water is added. ~he pH is then adjusted to 2.5 with about 13 9 of 52%
HN03. A solution o~ 32.5 g of sodium silicate (28X of SiO2) and 10 9 of sod;um carbonate in 120 ml of water is then added~ followed by a solution of 10 g of an~i-mono ~rioxide, 10 9 of sodium fluoride and 27 9 of 52X
strength HN03 in 120 ml of water. The end pH is ad-justed to b.5 by adding about 8 ~ o~ 100X strength so~
dium hydroxide in 120 ml of water. The precipitate is filtered off, washed with water to remove soLuble salts~ and dried at a temperature of 90Ea Rat;o of the lead salts ;n the mixed crystals~ 83% PbCrO~
17% PbS04 The values determined w;th the CAPA-500 analyser are:
Med;an value 0.39 ~m Part;cle s;ze d;stribution: 66% between 0.15 and 0.5 ~m.
The relative tinctoriaL strength compared with a convent;onally produced p;gment of the same composi-tion was determined as 137~ using the method given in DIN 53,235.
The proportion of the coating in the total wei~ht of the pig~ent is 7.4%, The hue in paints is measured by DIN 53,235 is distinctly green;sh.
Exam~e 9: 0.6 part of the coated pigment obtained as in Example 2 ;s m;xed w;th 76 parts of polyv;nyl chlor ide~ 33 parts of dioctyl phthalate, 2 parts of dibu~yltin dilaurate and 2 parts of titanium dioxide, and the mixture ;s processed at 160C ;n a roll mill ;nto a thin f1lm in the course of 15 m;nutes. The greenish yellow colour-ation thus produced is intense and fast to migration and light.
xample 10: û.05 part of the coated pigment ob-tained as in Example 2 is mixed dry with 100 parts of poly-styreneO The mixture is kneaded at temperatures of between 180 and 220C un~il ;t is homogeneously coloured. The coloured material is allowed to cool down and is ground in a mill down 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 into mouldings. The result is reddish yello~ materials of good light fastness and thermaL stability.
Example 11: 60 parts of a 60% solution of a non drying alkyd resin in xylene ~supplied by the firm of Reichold-Albert-Chemie, West Germany, under the tradename of Ee~-koso ~ 27-320)o 36 parts of a 50%
solution of a melamine-formaldehyde res;n in an alcohol-aromatics mixture tsupplied by the firm of Re;chold~
Albert-Chemie under the tradename of Super-8eckami ~ 13-501)0 2 parts of xylene and 2 parts of methylcellosolve are mixed, and 100 parts of this mixture are stirred by means of a stirrer to give a homogeneous lacquer solution.
9S parts of the transparent lacquer thus obtained and S
parts of the coated pigment as per Example 2 are ball-milled for 72 hours~ The coloured lacquer is then applied to sheet metal by a convent;onal spraying method and is baked thereon at 120~C for 30 minutes. The result i5 a yello~ coating of good light fastness.
- 14 _ hydroxide are then added in the ;mmediate v;cinity 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 S g of anhydrous sodium sulfate in 120 ml of water is added. ~he pH is then adjusted to 2.5 with about 13 9 of 52%
HN03. A solution o~ 32.5 g of sodium silicate (28X of SiO2) and 10 9 of sod;um carbonate in 120 ml of water is then added~ followed by a solution of 10 g of an~i-mono ~rioxide, 10 9 of sodium fluoride and 27 9 of 52X
strength HN03 in 120 ml of water. The end pH is ad-justed to b.5 by adding about 8 ~ o~ 100X strength so~
dium hydroxide in 120 ml of water. The precipitate is filtered off, washed with water to remove soLuble salts~ and dried at a temperature of 90Ea Rat;o of the lead salts ;n the mixed crystals~ 83% PbCrO~
17% PbS04 The values determined w;th the CAPA-500 analyser are:
Med;an value 0.39 ~m Part;cle s;ze d;stribution: 66% between 0.15 and 0.5 ~m.
The relative tinctoriaL strength compared with a convent;onally produced p;gment of the same composi-tion was determined as 137~ using the method given in DIN 53,235.
The proportion of the coating in the total wei~ht of the pig~ent is 7.4%, The hue in paints is measured by DIN 53,235 is distinctly green;sh.
Exam~e 9: 0.6 part of the coated pigment obtained as in Example 2 ;s m;xed w;th 76 parts of polyv;nyl chlor ide~ 33 parts of dioctyl phthalate, 2 parts of dibu~yltin dilaurate and 2 parts of titanium dioxide, and the mixture ;s processed at 160C ;n a roll mill ;nto a thin f1lm in the course of 15 m;nutes. The greenish yellow colour-ation thus produced is intense and fast to migration and light.
xample 10: û.05 part of the coated pigment ob-tained as in Example 2 is mixed dry with 100 parts of poly-styreneO The mixture is kneaded at temperatures of between 180 and 220C un~il ;t is homogeneously coloured. The coloured material is allowed to cool down and is ground in a mill down 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 into mouldings. The result is reddish yello~ materials of good light fastness and thermaL stability.
Example 11: 60 parts of a 60% solution of a non drying alkyd resin in xylene ~supplied by the firm of Reichold-Albert-Chemie, West Germany, under the tradename of Ee~-koso ~ 27-320)o 36 parts of a 50%
solution of a melamine-formaldehyde res;n in an alcohol-aromatics mixture tsupplied by the firm of Re;chold~
Albert-Chemie under the tradename of Super-8eckami ~ 13-501)0 2 parts of xylene and 2 parts of methylcellosolve are mixed, and 100 parts of this mixture are stirred by means of a stirrer to give a homogeneous lacquer solution.
9S parts of the transparent lacquer thus obtained and S
parts of the coated pigment as per Example 2 are ball-milled for 72 hours~ The coloured lacquer is then applied to sheet metal by a convent;onal spraying method and is baked thereon at 120~C for 30 minutes. The result i5 a yello~ coating of good light fastness.
Claims (12)
1. Monoclinic lead chromate pigments containing lead chromate and lead sulfate in a weight ratio of 89.9:10.1 to 60:40, wherein the pigment particles have a median value of 0.35-0.45µum and 50-75% 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 0.35-0.45 µm and 55-70% by weight of all the particles have a Stokes diameter of 0.15-0.5 µm.
3. Monoclinic 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 coating 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 |
|---|---|---|---|
| CH441883 | 1983-08-12 | ||
| CH4418/83-4 | 1983-08-12 | ||
| CH14184 | 1984-01-12 | ||
| CH141/84-7 | 1984-01-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1220004A true CA1220004A (en) | 1987-04-07 |
Family
ID=25683642
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000460694A Expired CA1220004A (en) | 1983-08-12 | 1984-08-10 | Monoclinic lead chromate pigments |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0138752B1 (en) |
| BR (1) | BR8404029A (en) |
| CA (1) | CA1220004A (en) |
| DE (1) | DE3461292D1 (en) |
| ES (1) | ES535108A0 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| IT1229075B (en) * | 1985-04-05 | 1991-07-17 | Fidia Farmaceutici | Topical compsn. contg. hyaluronic acid deriv. as vehicle |
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 DE8484810389T patent/DE3461292D1/en not_active Expired
- 1984-08-06 EP EP19840810389 patent/EP0138752B1/en not_active Expired
- 1984-08-10 BR BR8404029A patent/BR8404029A/en unknown
- 1984-08-10 CA CA000460694A patent/CA1220004A/en not_active Expired
- 1984-08-11 ES ES535108A patent/ES535108A0/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| ES8600647A1 (en) | 1985-10-16 |
| ES535108A0 (en) | 1985-10-16 |
| EP0138752A1 (en) | 1985-04-24 |
| DE3461292D1 (en) | 1987-01-02 |
| EP0138752B1 (en) | 1986-11-12 |
| BR8404029A (en) | 1985-07-16 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |