CA1065557A - Pigments containing lead chromate - Google Patents
Pigments containing lead chromateInfo
- Publication number
- CA1065557A CA1065557A CA243,316A CA243316A CA1065557A CA 1065557 A CA1065557 A CA 1065557A CA 243316 A CA243316 A CA 243316A CA 1065557 A CA1065557 A CA 1065557A
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- CA
- Canada
- Prior art keywords
- lead
- pigment
- chromate
- parts
- sulfate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C49/00—Ketones; Ketenes; Dimeric ketenes; Ketonic chelates
- C07C49/76—Ketones containing a keto group bound to a six-membered aromatic ring
- C07C49/84—Ketones containing a keto group bound to a six-membered aromatic ring containing ether groups, groups, groups, or groups
-
- 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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- 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
- C09C3/00—Treatment in general of inorganic materials, other than fibrous fillers, to enhance their pigmenting or filling properties
- C09C3/06—Treatment with inorganic compounds
- C09C3/063—Coating
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Pigments, Carbon Blacks, Or Wood Stains (AREA)
- Paints Or Removers (AREA)
- Inorganic Compounds Of Heavy Metals (AREA)
Abstract
METHOD FOR THE MANUFACTURE OF A LEAD
CHROMATE CONTAINING PIGMENT HAVING A
LOW ACID SOLUBLE LEAD CONTENT
ABSTRACT OF THE DISCLOSURE
A process for the production of lead chromate-containing pigments such as the light chrome yellows and the molybdate oranges and reds having a low content of acid soluble lead, good color and tinting properties and excellent resistance to industrial environments is described. The process comprises forming a lead chromate-containing precipitate in acidic aqueous medium containing chloride ions and an excess of lead ions in the absence of a pH buffering agent, coating the precipitate with a silicon and antimony compound, adjusting the pH of the medium to below 7 and recovering, the coated precipitate as a pigment.
CHROMATE CONTAINING PIGMENT HAVING A
LOW ACID SOLUBLE LEAD CONTENT
ABSTRACT OF THE DISCLOSURE
A process for the production of lead chromate-containing pigments such as the light chrome yellows and the molybdate oranges and reds having a low content of acid soluble lead, good color and tinting properties and excellent resistance to industrial environments is described. The process comprises forming a lead chromate-containing precipitate in acidic aqueous medium containing chloride ions and an excess of lead ions in the absence of a pH buffering agent, coating the precipitate with a silicon and antimony compound, adjusting the pH of the medium to below 7 and recovering, the coated precipitate as a pigment.
Description
10~5~
This invention relates to a process for the production of a lead sulfochromate or lead chromate-sulfate-molybdate pigment product containing at least 50% of lead chromate and having an acid soluble lead cOntent, ex-pressed as PbO, of less than 5% by weight of the pigment, said process com-prising forming a lead chromate-containing precipitate in an acid~c aqueous medium containing an excess of lead ions by contacting an aqueous solution containing chromate and sulfate ions or chromate, sulfate and molybdate ions with an aqueous solution con~aining lead ions in the presence of chloride ions and in the absence~dfa buffering agent, adding to the aqueous medium~a coating amount of a silicon compound and an antimony compound andL~precipitat-ing said compounds as a surface coating on said precipitate, adjusting the pH
of the aqueous medium to below 7 and recovering the resulting product from the aqueous medium.
The phrase ~a low content of acid soluble lead~ as used herein refers to the description and analytical method set forth in the "Home Office Test", as described in Statutory Rules ~ Orders 1926, No. 1621~.concerning ~ead~Paints~ as standardized in the Lead Paint (protection against poisoning) Act, 1926. See also British Standard 282~389~ 1963 Appendix J. and British Standard 3900, Part B 3, 1965.
Pigments containing pure lead chromate (PbCrO4) and having a low acid soluble lead content are known and are manufactured by adding an aqueous solution of lead ions to an aqueous solution of chromate ions in such a quantity that during the p~ecipitation an excess of chromate ions is maintain-ed. Pigments which are not exclusively lead chromate cannot be manufactured in the presence of excess chromate ions and it is an objective of this inven-tion to provide a method ~.r-manufacturing lead chromate-containing pigment : which do not contain pure PbCrO~ and have a low content of acid soluble lead.
According to the present invention a lead chromate-containing precipitate is for~ed under acid conditions in the presence of chloride ions ' ~ - 2 -.~, ^\
O~;~;S57 or in the presence of chloride and aluminum ions but in the absence of a pH
buffering material by bringing together an aqueous solution of lead ions and an aqueous solution of chromate and sulfate ions under conditions to main-tain an excess of lead ions in the reaction 2a -SS~7 medium during the precipitation and thereafter coating the result-ing pigment particles with A silicon and antimony-containing coating~
The pigment materials of this invention belong to ~he group of lead chromates of the type PbCrO4.PbSo4 (lead sulfochro-mate), the light chrome yellows (Colour Index, 3rd. Ed. r 1~71, Pigment Yellow 34, Ref. No. 77603) and Pb('rO~.PbMoO~.PbSO4 mi~ed crystals, known as the molybdate oranges and reds (Colour Index ; 3rd Ed., 1971, Pigment Red 104, ~ef. No. 77605), as well as chrome ;; 10 greens, which are combinations of iron blues and chrome yellows and phthalocyanine chrome greens, which are combinations of phthalo-` :
cyanine blue and chrome yellow, in powder or presscake form.
The lead sulfochromate pigments of the invention are usually prepared by starting with a solution of a lead salt/ e.g.
lead nitrate, to which a solution of chromate ions and sulfate ions are added. It is also possible to use for the precipitation a dichromate ions-containing solution, in which case an alkali hydroxide is added to the solution, to convert the dichromate ion into the chromate ion. Preferably, a combined chromate and sulfate ions-containing solution is used. In the case of the molybdates ~; a coprecipitation method is employed wherein a solution of lead ons and a solution of chromate, molybdate and sulfate ions are simultaneously added to water containing a small, but sufficient, amount o~ lead ions to maintain an excess of lead during precipi-tation.
In the past it has always been deemed necessar~ in the preparation of nonexclusively lead chromate-containing pigments .,.'~,1 .
which meet the acid soluble lead requirement of the "E~ome Ofice Test" to carry out -the precipitation process in a reaction medium containing a pH buffering material, particularly sodium carbonate, to prevent the pH from falling too low and thus to minimize the solubility of the lead chromate-containing precipitate in the medium. Now, in accordance with the present invention, it has unexpectedly been found that not only can a lead chromate pigment having a low content of acid soluble lead be formed in the absence of a pH bufferin~ material, but that the resulting pigments possess tint strengths which are qualitatively equal to those of the pi~ments formed with a buffering mater:ial. Further, the lead chromate containing pigments produced in accordance with this in-vention do not exhibit the change in color tint which usually ~ occurs when the commercially available pigrnents which are not pure ; PbCrO4 and which have a low content of acid soluble lead are com-pounded in paints and drawn down. In fact, the color and tinting properties of the pigments of this invention are equal to those of the normal, higher lead version of the same pigment.
The maintenance of an excess of lead ion~ in the reac-; tion medium during the precipitation of nonpure lead chromate pigments or the maintenance of an excess of chromate ions during the precipitation of the pure lead chromate pigments is known to reduce the solubility of the lead chromate containing precipitate to as small a value as possible and to guarantee a regular crystal growth of the particles. It also is generally accepted that the precipitate should be coated with silicon and antimony compounds to assure the provision of lead chromate-containing pigments with a low content of acid soluble lead. Furthermore, it is conventional to maintain the amount of lead sulfate in the mixed crystal within certain limits to optimize the particle strength. Thus, during the formation of the lead chromate-sulfate-molybdate-pigments the maximum quantity of lead sulfate, calculated on the total content of lead chromate-sulfate-molybdate present in the mixed crystal, will preferably be 3%, and most preferably
This invention relates to a process for the production of a lead sulfochromate or lead chromate-sulfate-molybdate pigment product containing at least 50% of lead chromate and having an acid soluble lead cOntent, ex-pressed as PbO, of less than 5% by weight of the pigment, said process com-prising forming a lead chromate-containing precipitate in an acid~c aqueous medium containing an excess of lead ions by contacting an aqueous solution containing chromate and sulfate ions or chromate, sulfate and molybdate ions with an aqueous solution con~aining lead ions in the presence of chloride ions and in the absence~dfa buffering agent, adding to the aqueous medium~a coating amount of a silicon compound and an antimony compound andL~precipitat-ing said compounds as a surface coating on said precipitate, adjusting the pH
of the aqueous medium to below 7 and recovering the resulting product from the aqueous medium.
The phrase ~a low content of acid soluble lead~ as used herein refers to the description and analytical method set forth in the "Home Office Test", as described in Statutory Rules ~ Orders 1926, No. 1621~.concerning ~ead~Paints~ as standardized in the Lead Paint (protection against poisoning) Act, 1926. See also British Standard 282~389~ 1963 Appendix J. and British Standard 3900, Part B 3, 1965.
Pigments containing pure lead chromate (PbCrO4) and having a low acid soluble lead content are known and are manufactured by adding an aqueous solution of lead ions to an aqueous solution of chromate ions in such a quantity that during the p~ecipitation an excess of chromate ions is maintain-ed. Pigments which are not exclusively lead chromate cannot be manufactured in the presence of excess chromate ions and it is an objective of this inven-tion to provide a method ~.r-manufacturing lead chromate-containing pigment : which do not contain pure PbCrO~ and have a low content of acid soluble lead.
According to the present invention a lead chromate-containing precipitate is for~ed under acid conditions in the presence of chloride ions ' ~ - 2 -.~, ^\
O~;~;S57 or in the presence of chloride and aluminum ions but in the absence of a pH
buffering material by bringing together an aqueous solution of lead ions and an aqueous solution of chromate and sulfate ions under conditions to main-tain an excess of lead ions in the reaction 2a -SS~7 medium during the precipitation and thereafter coating the result-ing pigment particles with A silicon and antimony-containing coating~
The pigment materials of this invention belong to ~he group of lead chromates of the type PbCrO4.PbSo4 (lead sulfochro-mate), the light chrome yellows (Colour Index, 3rd. Ed. r 1~71, Pigment Yellow 34, Ref. No. 77603) and Pb('rO~.PbMoO~.PbSO4 mi~ed crystals, known as the molybdate oranges and reds (Colour Index ; 3rd Ed., 1971, Pigment Red 104, ~ef. No. 77605), as well as chrome ;; 10 greens, which are combinations of iron blues and chrome yellows and phthalocyanine chrome greens, which are combinations of phthalo-` :
cyanine blue and chrome yellow, in powder or presscake form.
The lead sulfochromate pigments of the invention are usually prepared by starting with a solution of a lead salt/ e.g.
lead nitrate, to which a solution of chromate ions and sulfate ions are added. It is also possible to use for the precipitation a dichromate ions-containing solution, in which case an alkali hydroxide is added to the solution, to convert the dichromate ion into the chromate ion. Preferably, a combined chromate and sulfate ions-containing solution is used. In the case of the molybdates ~; a coprecipitation method is employed wherein a solution of lead ons and a solution of chromate, molybdate and sulfate ions are simultaneously added to water containing a small, but sufficient, amount o~ lead ions to maintain an excess of lead during precipi-tation.
In the past it has always been deemed necessar~ in the preparation of nonexclusively lead chromate-containing pigments .,.'~,1 .
which meet the acid soluble lead requirement of the "E~ome Ofice Test" to carry out -the precipitation process in a reaction medium containing a pH buffering material, particularly sodium carbonate, to prevent the pH from falling too low and thus to minimize the solubility of the lead chromate-containing precipitate in the medium. Now, in accordance with the present invention, it has unexpectedly been found that not only can a lead chromate pigment having a low content of acid soluble lead be formed in the absence of a pH bufferin~ material, but that the resulting pigments possess tint strengths which are qualitatively equal to those of the pi~ments formed with a buffering mater:ial. Further, the lead chromate containing pigments produced in accordance with this in-vention do not exhibit the change in color tint which usually ~ occurs when the commercially available pigrnents which are not pure ; PbCrO4 and which have a low content of acid soluble lead are com-pounded in paints and drawn down. In fact, the color and tinting properties of the pigments of this invention are equal to those of the normal, higher lead version of the same pigment.
The maintenance of an excess of lead ion~ in the reac-; tion medium during the precipitation of nonpure lead chromate pigments or the maintenance of an excess of chromate ions during the precipitation of the pure lead chromate pigments is known to reduce the solubility of the lead chromate containing precipitate to as small a value as possible and to guarantee a regular crystal growth of the particles. It also is generally accepted that the precipitate should be coated with silicon and antimony compounds to assure the provision of lead chromate-containing pigments with a low content of acid soluble lead. Furthermore, it is conventional to maintain the amount of lead sulfate in the mixed crystal within certain limits to optimize the particle strength. Thus, during the formation of the lead chromate-sulfate-molybdate-pigments the maximum quantity of lead sulfate, calculated on the total content of lead chromate-sulfate-molybdate present in the mixed crystal, will preferably be 3%, and most preferably
2%, whereas during the formation of the lead sulfochromates the total content of lead sulfate, calculated on the total content of lead chromate-lead sulfate in the mixed crystal, will preferably be 32.5% and most preferably less than 25%.
The precipitation of nonexclusively lead chromate particles is conventionally carried out in the presence of chloride ions and optionally chloride and aluminum ions. Usually, as is -- ~O~;S5~
preferred herein, the preparation of lead sulfochromates is carried out in the presence of aluminum ions and chloride ions and the quantity of aluminum used will be 0.5-2%, preferably 1% calculated on the end product and express-ed as A1203. The quantity of the chloride present will usually be 200-800 mg., preferably 400 mg. NaCl/liter of mother liquor (after precipitation). The molybdates are usually precipitated in the presence of chloride ions only~
and1the quantity of chlo~ide will usually be 120-240 mg. NaCl/liter mother liquor (after precipitation), and preferably 120 mg.
The time and the temperature during precipitation are important tot~he crystal structure and "soluble lead content" of the pig~ent and will vary depending upon the composition of the particular pigment, but usually the time is at least about 30 minutes and the temperature is from about 20 to about 70 C. For the lead sulfochromates the time will preferably be 30-120 minutes at 35-70 C. whereas for the molybdates the time is usually from ~; 30 to about 60 minutes at 20 C.
Aftertreatments known to improve the light- and heat resistance and resistance to atmospheric influences of the lead chromate-containing precipitates are likewise effective with the products of this invention.
Thus, any of the well-known metals or combinations of metals such as, e.g.
aluminum, silicon, antimony, cerium, tin, titanium, zirconium, and the like, which can be precipitated on the lead chromate-containing particles, can be used. Aftertreatment with a silicon compound and an antimony compound provides lead chromate-containing pigments having superior resistance to light, weath~èr and industrial atmospheric influences.
The invention is illustrated by the following examples in which all parts are given as parts by weight. In the examples the procedure was carried out as a single production step for reasons of economy. The exact procedure, however, is not meant to exclude other steps such as, for example, washing salt-free~ e.g. by means of decantation before adding the aftertreat-~ _ 5 _ s~
ment materials to impro~e the heat and light-fastness, and like steps. In the examples the content o~ soluble lead in the pi.gment was - 5a -~sss~
determined according to the method as clescribed in Appendix J.
of British Standard 282,389 - 1963 and resistance to atmospheric influences was determined according to DIN 50018.
Example 1 To a reaction vessel containing a solution of 190 parts of lead nitrate in 2400 parts of water at 50C. was added with stirring over a period of 90 minutes a solutio.n of 61.7 parts of sodium dichromate (Na2Cr2O7.2H2O), 20.9 parts of sodium sulfate (Na2SO4.OH2O), 15.0 parts of sodium hydroxide, 11.0 parts of sodium chloride and 3.8 parts of sodium aluminate (NaAlO2) in 370 parts of water at 50C. Next a solution of 4.3 parts of sulfuric acid, 5.0 parts of sodium sulfate (Na2SO4.OH2O) and 6.7 parts of titanyl sulfate (containing 10 g. TiO2/100 cm3) were added over a period of 15 mlnutes, following which time the pH
of the reslllting slurry was adjusted to about 6. Next a solution of 23.2 parts of neutral waterglass in 120 parts of water was added, and then a solution of 6.6 parts of anhydrous antimony tri-:; fluoride in 120 parts of water was added, and the pH was adjusted to 6.5. The precipitate was then isolated by filtering, was washed free of soluble salts and was dried at 80-90C. The product was 196 9 parts of a lead sulfochromate pigment having an acid soluble lead content, expressed as PbO, of 1%. The resistance of the pigment to industrial atmospheres was good.
Comparative Example A (A silica and antimony treatea pigment with a high soluble lead content) ..... .. . _ . .. . _ , ........... ,. _ __ .
To a reaction vessel containing 214.8 parts of lead nitrate dissolved in 2400 parts of water were added 4.5 parts of anhydrous sodium carbonate dissolved in 45 parts of water and the temperature of the mixture was brought to 50C. A solution of
The precipitation of nonexclusively lead chromate particles is conventionally carried out in the presence of chloride ions and optionally chloride and aluminum ions. Usually, as is -- ~O~;S5~
preferred herein, the preparation of lead sulfochromates is carried out in the presence of aluminum ions and chloride ions and the quantity of aluminum used will be 0.5-2%, preferably 1% calculated on the end product and express-ed as A1203. The quantity of the chloride present will usually be 200-800 mg., preferably 400 mg. NaCl/liter of mother liquor (after precipitation). The molybdates are usually precipitated in the presence of chloride ions only~
and1the quantity of chlo~ide will usually be 120-240 mg. NaCl/liter mother liquor (after precipitation), and preferably 120 mg.
The time and the temperature during precipitation are important tot~he crystal structure and "soluble lead content" of the pig~ent and will vary depending upon the composition of the particular pigment, but usually the time is at least about 30 minutes and the temperature is from about 20 to about 70 C. For the lead sulfochromates the time will preferably be 30-120 minutes at 35-70 C. whereas for the molybdates the time is usually from ~; 30 to about 60 minutes at 20 C.
Aftertreatments known to improve the light- and heat resistance and resistance to atmospheric influences of the lead chromate-containing precipitates are likewise effective with the products of this invention.
Thus, any of the well-known metals or combinations of metals such as, e.g.
aluminum, silicon, antimony, cerium, tin, titanium, zirconium, and the like, which can be precipitated on the lead chromate-containing particles, can be used. Aftertreatment with a silicon compound and an antimony compound provides lead chromate-containing pigments having superior resistance to light, weath~èr and industrial atmospheric influences.
The invention is illustrated by the following examples in which all parts are given as parts by weight. In the examples the procedure was carried out as a single production step for reasons of economy. The exact procedure, however, is not meant to exclude other steps such as, for example, washing salt-free~ e.g. by means of decantation before adding the aftertreat-~ _ 5 _ s~
ment materials to impro~e the heat and light-fastness, and like steps. In the examples the content o~ soluble lead in the pi.gment was - 5a -~sss~
determined according to the method as clescribed in Appendix J.
of British Standard 282,389 - 1963 and resistance to atmospheric influences was determined according to DIN 50018.
Example 1 To a reaction vessel containing a solution of 190 parts of lead nitrate in 2400 parts of water at 50C. was added with stirring over a period of 90 minutes a solutio.n of 61.7 parts of sodium dichromate (Na2Cr2O7.2H2O), 20.9 parts of sodium sulfate (Na2SO4.OH2O), 15.0 parts of sodium hydroxide, 11.0 parts of sodium chloride and 3.8 parts of sodium aluminate (NaAlO2) in 370 parts of water at 50C. Next a solution of 4.3 parts of sulfuric acid, 5.0 parts of sodium sulfate (Na2SO4.OH2O) and 6.7 parts of titanyl sulfate (containing 10 g. TiO2/100 cm3) were added over a period of 15 mlnutes, following which time the pH
of the reslllting slurry was adjusted to about 6. Next a solution of 23.2 parts of neutral waterglass in 120 parts of water was added, and then a solution of 6.6 parts of anhydrous antimony tri-:; fluoride in 120 parts of water was added, and the pH was adjusted to 6.5. The precipitate was then isolated by filtering, was washed free of soluble salts and was dried at 80-90C. The product was 196 9 parts of a lead sulfochromate pigment having an acid soluble lead content, expressed as PbO, of 1%. The resistance of the pigment to industrial atmospheres was good.
Comparative Example A (A silica and antimony treatea pigment with a high soluble lead content) ..... .. . _ . .. . _ , ........... ,. _ __ .
To a reaction vessel containing 214.8 parts of lead nitrate dissolved in 2400 parts of water were added 4.5 parts of anhydrous sodium carbonate dissolved in 45 parts of water and the temperature of the mixture was brought to 50C. A solution of
3~ 370 parts of water, 67.6 parts of sodium dichromate (Na2Cr2O7.2H2O), 14.8 parts of sodium sulfate (Na2SO4 OH2O) and 18.4 parts of sodium hydroxide was added at 50C. to form a precipita-te. To the resulting precipitate was added over 15 minutes a solution of
4.3 parts of sulfuric acid (66Be), 5.0 parts of sodium sulfate ~6S~7 (Na2SO4OOH2O) and 6.7 parts of titanyl sulEate (containing 10 g.
of TiO2/100 cm3) followed by a solution of 23.2 parts of neutral waterglass and 4.2 parts of sodium hydrox.ide in 120 parts of water over the next 15 minu~es. ~inally a solution of 6.6 parts of anhydrous antimony trifluoride in 120 parts of water was added and the pH was adjusted to about 6.5. The product was 197.6 parts of a lead sulfochromate-containing pigment which had a soluble lead content, expressed as PbO, of 9%, which value lies above the Great Britain statutory prescribed requirement of less than S%. The fastness of the pigment of this example to industrial atmospheres was limited.
Comparative Example ~ ~A noncoated pigment, having a high soluble lead content)~ `
. _, _ ... . . _ _ . .. ... _ . .... .
To a reaction vessel containing 190 parts of lead : nitrate dissolved in 2400 parts of water at 50C. was added over 90 minutes with s-tirring a solution of 61.7 parts of sodium ; dichromate (Na2Cr2O7.2~I2O), 20.9 parts of sodium sulfate ~Na2SO4.OH2O), 15.0 parts of sodium hydroxide, 11.0 parts of sodium chloride and 3.8 parts of sodium aluminate (NaAlO2) in 370 parts of water at 50C. Following formation of the precipi-tate a solution of 4.3 parts of sulfuric acid and 5.0 parts of sodium sulfate were added over 15 minutes and the precipitate was filtered, washed and dried (80-90C.). The product was a lead sulfochromate pigment (165.1 parts) having an acid soluble lead content, expressed as PbO, of about 5%, which amount does not meet the Great Britain statutory prescribed re~uirement of less than 5%.
To a reaction vessel containing 2900 parts of water and 6.25 parts of sodium chloride were added 77 parts of a lead nitrate solution containing about 215 g. Pb/l. To the vessel were simultaneously added with stirring an acidified solution of 180.6 parts of lead nitrate in 1125 parts of water and a solution of 71.7 parts of sodium ~ichromate (Na2Cr2O7.2H2O), 19.2 parts of sodium molybdate ~Na2MoO~.2H2O), 1.8 parts o~ sodium sulfate (Na2SO~.OH2O) and 22 parts sodium hydroxide in 1125 parts of water.
Next a solution of 45.5 parts of neutral waterglass in 65 parts of water followed by a solution of 23.3 parts of aluminum sulfate tNa2(SO4)3~18H2O) in 160 parts of water and a solution of 17.6 parts of anhydrous antimony fluoride in 120 parts of water were added to the resultlng slurry and the pH was adjusted to about 6.5. The product was then isolated by filtering, washing and drying at 80-90C. The product of this example was 219 parts of a molybdate red pigment having an acid soluble lead content, ex-press~ as PbO, of 2%. The resistance of the pigment to industrial atmospheres was excellent.
Comparative Example C (Molybdate red with a high soluble lead content) .. . . _ . _ . _ _ . . . ......
To a reaction vessel containing 2900 parts of water and 6.25 parts of sodium chloride at 20C. were added 77 parts of lead nitrate solution (containing about 215 g. Pb/l.) To this mixture were simultaneously added a solution of 193.5 parts of lead nitrate and 11.25 parts of nitric acid (55%) in 1125 parts of water and a solution of 71.3 parts of sodium dichromate (Na2Cr2O7.2H2O), 16.8 parts of sodium molybdate (Na2MoO4.2H2O), 4.7~ parts of sodium sulfate (Na2SO4.OH2O) and 19.1 parts of sodium hydroxide in 1125 parts of water. Following formation of the precipitate a solution of 45.5 parts of neutral waterglass in 65 parts of water was added, followed by a solution of 23.3 parts of aluminum sulfate (A12(SO4)3.18H2O) in 160 parts of water : and then a solution of 17.6 parts of anhydrous antimony trifluoride in 120 parts of water. The pH was adjusted to 6.5 and the precipi-tate was filtered~ washed and dried (80-90C.). The product was 232 parts of a molybdate red pigment having an acid soluble lead content, expressed as PbO, of about 6%.
of TiO2/100 cm3) followed by a solution of 23.2 parts of neutral waterglass and 4.2 parts of sodium hydrox.ide in 120 parts of water over the next 15 minu~es. ~inally a solution of 6.6 parts of anhydrous antimony trifluoride in 120 parts of water was added and the pH was adjusted to about 6.5. The product was 197.6 parts of a lead sulfochromate-containing pigment which had a soluble lead content, expressed as PbO, of 9%, which value lies above the Great Britain statutory prescribed requirement of less than S%. The fastness of the pigment of this example to industrial atmospheres was limited.
Comparative Example ~ ~A noncoated pigment, having a high soluble lead content)~ `
. _, _ ... . . _ _ . .. ... _ . .... .
To a reaction vessel containing 190 parts of lead : nitrate dissolved in 2400 parts of water at 50C. was added over 90 minutes with s-tirring a solution of 61.7 parts of sodium ; dichromate (Na2Cr2O7.2~I2O), 20.9 parts of sodium sulfate ~Na2SO4.OH2O), 15.0 parts of sodium hydroxide, 11.0 parts of sodium chloride and 3.8 parts of sodium aluminate (NaAlO2) in 370 parts of water at 50C. Following formation of the precipi-tate a solution of 4.3 parts of sulfuric acid and 5.0 parts of sodium sulfate were added over 15 minutes and the precipitate was filtered, washed and dried (80-90C.). The product was a lead sulfochromate pigment (165.1 parts) having an acid soluble lead content, expressed as PbO, of about 5%, which amount does not meet the Great Britain statutory prescribed re~uirement of less than 5%.
To a reaction vessel containing 2900 parts of water and 6.25 parts of sodium chloride were added 77 parts of a lead nitrate solution containing about 215 g. Pb/l. To the vessel were simultaneously added with stirring an acidified solution of 180.6 parts of lead nitrate in 1125 parts of water and a solution of 71.7 parts of sodium ~ichromate (Na2Cr2O7.2H2O), 19.2 parts of sodium molybdate ~Na2MoO~.2H2O), 1.8 parts o~ sodium sulfate (Na2SO~.OH2O) and 22 parts sodium hydroxide in 1125 parts of water.
Next a solution of 45.5 parts of neutral waterglass in 65 parts of water followed by a solution of 23.3 parts of aluminum sulfate tNa2(SO4)3~18H2O) in 160 parts of water and a solution of 17.6 parts of anhydrous antimony fluoride in 120 parts of water were added to the resultlng slurry and the pH was adjusted to about 6.5. The product was then isolated by filtering, washing and drying at 80-90C. The product of this example was 219 parts of a molybdate red pigment having an acid soluble lead content, ex-press~ as PbO, of 2%. The resistance of the pigment to industrial atmospheres was excellent.
Comparative Example C (Molybdate red with a high soluble lead content) .. . . _ . _ . _ _ . . . ......
To a reaction vessel containing 2900 parts of water and 6.25 parts of sodium chloride at 20C. were added 77 parts of lead nitrate solution (containing about 215 g. Pb/l.) To this mixture were simultaneously added a solution of 193.5 parts of lead nitrate and 11.25 parts of nitric acid (55%) in 1125 parts of water and a solution of 71.3 parts of sodium dichromate (Na2Cr2O7.2H2O), 16.8 parts of sodium molybdate (Na2MoO4.2H2O), 4.7~ parts of sodium sulfate (Na2SO4.OH2O) and 19.1 parts of sodium hydroxide in 1125 parts of water. Following formation of the precipitate a solution of 45.5 parts of neutral waterglass in 65 parts of water was added, followed by a solution of 23.3 parts of aluminum sulfate (A12(SO4)3.18H2O) in 160 parts of water : and then a solution of 17.6 parts of anhydrous antimony trifluoride in 120 parts of water. The pH was adjusted to 6.5 and the precipi-tate was filtered~ washed and dried (80-90C.). The product was 232 parts of a molybdate red pigment having an acid soluble lead content, expressed as PbO, of about 6%.
Claims (7)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for the production of a lead sulfochromate or lead chro-mate-sulfate-molybdate pigment product containing at least 50% of lead chro-mate and having an acid soluble lead content, expressed as PbO, of less than 5% by weight of the pigment, said process comprising forming a lead chromate-containing precipitate in an acidic aqueous medium containing an excess of lead ions by contacting an aqueous solution containing chromate and sulfate ions or chromate, sulfate and molybdate ions with an aqueous solution con-taining lead ions in the presence of chloride ions and in the absence of a buffering agent, adding to the aqueous medium a coating amount of a silicon compound and an antimony compound and precipitating said compounds as a surface coating on said precipitate, adjusting the pH of the aqueous medium to below 7 and recovering the resulting product from the aqueous medium.
2. The process of claim 1 wherein the contacting is carried out at 20-70°C. over a time period of at least 30 minutes.
3. The process of claim 1 wherein the lead chromate pigment is a lead sulfochromate pigment and the precipitation is carried out in the presence of chloride and aluminum ions at 35-70°C. for a time period of at least 30 minutes.
4 The process of claim 3 wherein the lead sulfochromate pigment con-tains less than 32.5% of lead sulfate.
5. The process of claim 1 wherein the lead chromate pigment is a lead chromate-sulfate-molybdate pigment.
6. The process of claim 5 wherein the lead chromate-sulfate-molybdate pigment contain less than 3% of lead sulfate.
7. A lead sulfochromate or lead chromate-sulfate-molybdate pigment product containing at least 50% of lead chromate and having an acid soluble lead content, expressed as PbO, of less than 5% by weight of the pigment, produced according to the process of claims 1, 3 or 5.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL7500365A NL166274C (en) | 1975-01-13 | 1975-01-13 | PROCESS FOR PREPARING AT LEAST 50% BY WEIGHT OF LEAD CHROME SIZE CONTAINING LEAD CHROME SULPHATE PIGMENT |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1065557A true CA1065557A (en) | 1979-11-06 |
Family
ID=19822975
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA243,316A Expired CA1065557A (en) | 1975-01-13 | 1976-01-12 | Pigments containing lead chromate |
Country Status (6)
| Country | Link |
|---|---|
| BE (1) | BE837380A (en) |
| CA (1) | CA1065557A (en) |
| DE (1) | DE2600365A1 (en) |
| FR (1) | FR2297234A1 (en) |
| GB (1) | GB1535351A (en) |
| NL (1) | NL166274C (en) |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3772047A (en) * | 1972-04-05 | 1973-11-13 | Hercules Inc | Preparation of red shade molybdate orange pigments |
-
1975
- 1975-01-13 NL NL7500365A patent/NL166274C/en not_active IP Right Cessation
-
1976
- 1976-01-07 BE BE7000757A patent/BE837380A/en not_active IP Right Cessation
- 1976-01-07 DE DE19762600365 patent/DE2600365A1/en active Granted
- 1976-01-12 GB GB100076A patent/GB1535351A/en not_active Expired
- 1976-01-12 CA CA243,316A patent/CA1065557A/en not_active Expired
- 1976-01-13 FR FR7600670A patent/FR2297234A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| BE837380A (en) | 1976-07-07 |
| FR2297234B3 (en) | 1979-06-22 |
| DE2600365A1 (en) | 1976-07-15 |
| DE2600365C2 (en) | 1987-12-03 |
| GB1535351A (en) | 1978-12-13 |
| FR2297234A1 (en) | 1976-08-06 |
| NL166274C (en) | 1981-07-15 |
| NL7500365A (en) | 1976-07-15 |
| NL166274B (en) | 1981-02-16 |
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