CA1102505A - Transparent iron oxide pigment prepared by organic solvent washing - Google Patents
Transparent iron oxide pigment prepared by organic solvent washingInfo
- Publication number
- CA1102505A CA1102505A CA303,500A CA303500A CA1102505A CA 1102505 A CA1102505 A CA 1102505A CA 303500 A CA303500 A CA 303500A CA 1102505 A CA1102505 A CA 1102505A
- Authority
- CA
- Canada
- Prior art keywords
- iron oxide
- pigment
- solvent
- transparent iron
- water
- 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.)
- Expired
Links
Landscapes
- Pigments, Carbon Blacks, Or Wood Stains (AREA)
- Paints Or Removers (AREA)
Abstract
TRANSPARENT IRON OXIDE PIGMENT
PREPARED BY ORGANIC SOLVENT WASHING
Abstract of the Disclosure Transparent iron oxide pigments having improved dispersibility are produced by organic solvent washing prior to drying.
PREPARED BY ORGANIC SOLVENT WASHING
Abstract of the Disclosure Transparent iron oxide pigments having improved dispersibility are produced by organic solvent washing prior to drying.
Description
This invention relates to iron oxide pigments and is directed particularly to a process for the preparation of transparent iron oxide pigments having improved dispersibility.
Typically iron oxide pigments are produced by pre-cipitation from solutions of water soluble salts, oxidation to the ferric state followed by filtration washing and finally drying at certain temperature ranges. During the drying process pigments undergo crystalline aggregatiorand agglomeration.
This results in an aggregated and agglomerated pigment which is subsequently difficult to disperse in the organic binder solvent conventionally used in present-day paint systems due to the fact that the organic binder and solvent is unable to wet and separate the primary particles of the aggregate and the agglomerate. Furthermore, when heating these iron oxide pig-ments under normal conditions, the average particle size, because of aggregation and agglomeration, becomes greater than 0.1 microns which is the maximum particle size desirable for good transparency. In order for transparent pigments to be useful, the particle size needs to be smaller than the wave length of visible light which is about 0.1 microns. If aggregatlon and agglomeration occurs, a greate~_-- ~~-~~~
, . _, _ _ . .
......
, ~ .. . .
,. . " . -, .. . . ... .. .. .
... ., - . . . , :
: .~ ~ : . : - . . .
, :.. ~ . . .. - .
:. . :
, , ; , : - :: . -.. . . .
. ~, . - ., . .: . ~
s effort is required to disperse the pigment into particle sizes of less than 0.1 micron. Transparent pigments are presently in great demand. This is due to the fact that there is an increased'use of these pigments in paints such as in the automotive field wherein these pigments impart a glossy finish to the metallic paint. The transparency of the pigment enables the formulator to achieve a desired ; color to the top coat in addition to giving a metallic effect. The iron oxide has the further advantage of imparting durability and stability to the coating through ultraviolet absorbing characteristics, A typical manufacturing process for transparent iron oxide pigment is taught in U. S. Patent 2,558,302.
Other teachings in the prior art as taught in U. S. Patent 2,33$,760 and U. S. Patènt 2J384~579 employed a process of kneading the pigrnent cake containing water with large quantities of water-immiscible drying oils, alkyl resins, nitrocellulose lacquers or other vehicles to expel all the water. These processes require a great amount of energy in order to expel sufficient quantities of water from the pigment cake. In view of the prior art and the need for easily dispersible iron oxide pigment having high transparency, it is the object of this invention to provide a process for producing such a transparen~ iron oxide pigment, ,''~
.~:
: , , . ,, - .......... ..
~25~5 In accordance with this invention there is provided transparent iron oxide pigments having improved dispersibility and an improved process for their preparation.
In accordance with the invention, this improved process for the preparation of such transparent iron oxide pigment is of the type wherein an aqueous mixture of iron oxide particles is formed. More particularly, this improved process comprises:
(a) filtering said iron oxide particles from said mixture and forming an iron oxide filter cake, (b) washing said iron oxide filter cake with water, (c) further washing with a solvent miscible with water, immiscible and non-reactive with iron oxide, having a boiling point below about 200C, and having a surface tension of less than 60 dynes per centimeter, and , ~ .. .. _ . .
.. . .- . . .. ~ .. . . - . . . ~ . ... - . -.. . . . . . . . ..... ... . ~ . ... . .. . . .
..... . . ... . . ~ .
. . . . . . . .
.. . .
.
.
- ~ . ...
~ . . .
(d) removing a substantial portion of said solvent from said iron oxide filter cake.
As mentioned supra, during the process of pre-paring transparent iron oxide pigments the removal of water results in an aggregation and agglomeration of the ~ -particles of pigment. Due to this aggregation and agglom-eration, the pigment is subsequently very difficult!to disperse in use It is known that pigment particles which are needle shaped such as in the transparent iron oxide pigments J particle to particle contact occu~s on the long .
axis Due to the great number of points of contact pigment dispersion in a given binder solvent system is most difficult It has been discovered that whçn the water which envelops the primary particles is replaced by a solvent of much lower surface tension, prior to drying, the resultant pigment does not aggregate and agglomerate to the same extent that it does upon drying from an aqueous slurry Apparently the replacement of water involves miscible displacement ~n the small capillaries The sol-vent requirements are chemical miscibility with water, immiscibility and non-reactivity with the iron oxide pig-ment, having a surface tension of less than 60 dynes per centimeter and a boiling point below about 200 Centigrade.
It has been found among the solvents that are useful are aliphatic alcohols containing 1 to 4 carbon atoms, glycol ethers, alkanolamines, ketonesJ dimethylsulfoxide, di- ~, me~hylform~mLde, meth~l pyrrolLdone, nitropropane, and :
s~ ::
dioxane. Among the alcohols which may be employed are methanol, ethanol, propyl, isopropyl, normal, secondary and tertiary butyl alcohols. Those glycol ethers which are contemplated are the mono- and dimethyl and ethyl ethers of ethylene glycol, diethylene glycol, propylene glycol, and dipropylene glycol. The solvents selected from the alkanolamines may be ethanolamine, diethanolamine, ;
isopropanolamine and diisopropanolamine. Among the ketones, solvents such as acetone, methylethylketone, and methyl-isobutylketone may be employed. Mixtures of any of the above may also be employed. It has also been found pos-sible to employ aromatic solvents in admixture with the above solvents Accordingly, solvents such as benzene, toluene and xylene may be employed in conjunction with the alcohols, ketones and the like, depending upon mutual com-patibility with one another and limited only by miscibility of the mixture with water. For example, it is possible to employ a mixture of 90% butanol and 10~ xylene in the practice of this invention.
The temperatures which may be employed for the washing step may range from 20 Centigrade to 100 Centi- , :
grade, depending upon the boiling point and the volatility of the sol~ent employed. The amounts which are employed for the washing will depend upon the amount of moisture ;~ which is present in the pigment slurry. It is contemplated ~ ." .
.
: ' t3125~ ~
that the normal range of solvent employed is from 1000 to 1500 milliliters for every lS0 to 300 grams of iron oxide filter cake. Upon sufficient washing, the iron pigment filter cake may be dried at temperatures ranging from 25 to 110 Centigrade.
In some instances the removal of the solvent may be hastened by drying the iron oxide filter cake under a vacuum of about 1 or
Typically iron oxide pigments are produced by pre-cipitation from solutions of water soluble salts, oxidation to the ferric state followed by filtration washing and finally drying at certain temperature ranges. During the drying process pigments undergo crystalline aggregatiorand agglomeration.
This results in an aggregated and agglomerated pigment which is subsequently difficult to disperse in the organic binder solvent conventionally used in present-day paint systems due to the fact that the organic binder and solvent is unable to wet and separate the primary particles of the aggregate and the agglomerate. Furthermore, when heating these iron oxide pig-ments under normal conditions, the average particle size, because of aggregation and agglomeration, becomes greater than 0.1 microns which is the maximum particle size desirable for good transparency. In order for transparent pigments to be useful, the particle size needs to be smaller than the wave length of visible light which is about 0.1 microns. If aggregatlon and agglomeration occurs, a greate~_-- ~~-~~~
, . _, _ _ . .
......
, ~ .. . .
,. . " . -, .. . . ... .. .. .
... ., - . . . , :
: .~ ~ : . : - . . .
, :.. ~ . . .. - .
:. . :
, , ; , : - :: . -.. . . .
. ~, . - ., . .: . ~
s effort is required to disperse the pigment into particle sizes of less than 0.1 micron. Transparent pigments are presently in great demand. This is due to the fact that there is an increased'use of these pigments in paints such as in the automotive field wherein these pigments impart a glossy finish to the metallic paint. The transparency of the pigment enables the formulator to achieve a desired ; color to the top coat in addition to giving a metallic effect. The iron oxide has the further advantage of imparting durability and stability to the coating through ultraviolet absorbing characteristics, A typical manufacturing process for transparent iron oxide pigment is taught in U. S. Patent 2,558,302.
Other teachings in the prior art as taught in U. S. Patent 2,33$,760 and U. S. Patènt 2J384~579 employed a process of kneading the pigrnent cake containing water with large quantities of water-immiscible drying oils, alkyl resins, nitrocellulose lacquers or other vehicles to expel all the water. These processes require a great amount of energy in order to expel sufficient quantities of water from the pigment cake. In view of the prior art and the need for easily dispersible iron oxide pigment having high transparency, it is the object of this invention to provide a process for producing such a transparen~ iron oxide pigment, ,''~
.~:
: , , . ,, - .......... ..
~25~5 In accordance with this invention there is provided transparent iron oxide pigments having improved dispersibility and an improved process for their preparation.
In accordance with the invention, this improved process for the preparation of such transparent iron oxide pigment is of the type wherein an aqueous mixture of iron oxide particles is formed. More particularly, this improved process comprises:
(a) filtering said iron oxide particles from said mixture and forming an iron oxide filter cake, (b) washing said iron oxide filter cake with water, (c) further washing with a solvent miscible with water, immiscible and non-reactive with iron oxide, having a boiling point below about 200C, and having a surface tension of less than 60 dynes per centimeter, and , ~ .. .. _ . .
.. . .- . . .. ~ .. . . - . . . ~ . ... - . -.. . . . . . . . ..... ... . ~ . ... . .. . . .
..... . . ... . . ~ .
. . . . . . . .
.. . .
.
.
- ~ . ...
~ . . .
(d) removing a substantial portion of said solvent from said iron oxide filter cake.
As mentioned supra, during the process of pre-paring transparent iron oxide pigments the removal of water results in an aggregation and agglomeration of the ~ -particles of pigment. Due to this aggregation and agglom-eration, the pigment is subsequently very difficult!to disperse in use It is known that pigment particles which are needle shaped such as in the transparent iron oxide pigments J particle to particle contact occu~s on the long .
axis Due to the great number of points of contact pigment dispersion in a given binder solvent system is most difficult It has been discovered that whçn the water which envelops the primary particles is replaced by a solvent of much lower surface tension, prior to drying, the resultant pigment does not aggregate and agglomerate to the same extent that it does upon drying from an aqueous slurry Apparently the replacement of water involves miscible displacement ~n the small capillaries The sol-vent requirements are chemical miscibility with water, immiscibility and non-reactivity with the iron oxide pig-ment, having a surface tension of less than 60 dynes per centimeter and a boiling point below about 200 Centigrade.
It has been found among the solvents that are useful are aliphatic alcohols containing 1 to 4 carbon atoms, glycol ethers, alkanolamines, ketonesJ dimethylsulfoxide, di- ~, me~hylform~mLde, meth~l pyrrolLdone, nitropropane, and :
s~ ::
dioxane. Among the alcohols which may be employed are methanol, ethanol, propyl, isopropyl, normal, secondary and tertiary butyl alcohols. Those glycol ethers which are contemplated are the mono- and dimethyl and ethyl ethers of ethylene glycol, diethylene glycol, propylene glycol, and dipropylene glycol. The solvents selected from the alkanolamines may be ethanolamine, diethanolamine, ;
isopropanolamine and diisopropanolamine. Among the ketones, solvents such as acetone, methylethylketone, and methyl-isobutylketone may be employed. Mixtures of any of the above may also be employed. It has also been found pos-sible to employ aromatic solvents in admixture with the above solvents Accordingly, solvents such as benzene, toluene and xylene may be employed in conjunction with the alcohols, ketones and the like, depending upon mutual com-patibility with one another and limited only by miscibility of the mixture with water. For example, it is possible to employ a mixture of 90% butanol and 10~ xylene in the practice of this invention.
The temperatures which may be employed for the washing step may range from 20 Centigrade to 100 Centi- , :
grade, depending upon the boiling point and the volatility of the sol~ent employed. The amounts which are employed for the washing will depend upon the amount of moisture ;~ which is present in the pigment slurry. It is contemplated ~ ." .
.
: ' t3125~ ~
that the normal range of solvent employed is from 1000 to 1500 milliliters for every lS0 to 300 grams of iron oxide filter cake. Upon sufficient washing, the iron pigment filter cake may be dried at temperatures ranging from 25 to 110 Centigrade.
In some instances the removal of the solvent may be hastened by drying the iron oxide filter cake under a vacuum of about 1 or
2 millimeters of mercury.
The yellow pigment obtained by this process can be converted to easily dispersible transparent red iron oxide pigment by calcination at temperatures rangi~g from 150C to 400C.
The invention and its advantages will be better understood with reference to the following description taken in connection with the accompanying drawing which illustrates a typical curve obtalned for Brightness values versus dispersion times employing a Red Devil paint shaker. As can be seen, this drawing illustrates that solvent washing results in pigment having greater dispersibility compared to pigment prepared by prior art procedures as indicated by higher Brightness values.
In order to teat the iron oxide pigment, obtained in accordance with the invention a dispersion procedure is employed wherein one and a half grams of the dried pigment are added to a four-ounce bottle containing 100 grams of 2 mm glass beads and 4.5 grams of a Dispersion Vehicle which consists of 80 weight percent acrylic resin, 4 weight percent normal butanol and 16 weight percent xylene. The bottle is stoppered and placed on a paint shaker for various lengths of time, upon which the bottle is cooled and 24 grams of Let-down Vehicle consisting of about ; 45 weight percent acrylic resin, 20 percent melamine resin, 7 percent butanol and 28 percent xylene. The mixture is then re-shaken, the glass beads filtered out, and the filtrate then tested for Brightness ~Y values.
::
_7_ ~ . ~.. . ,.,. ,, ' "
, .. . ~ -,' ,, -The dispersibility of the pigment is conveniently determined ~y tristimulus measurements of the Y values and is the difference between the Y values of the specularly reflected light and the diffusely reflected light, This difference is expressed as the Brightness ~Y value. These values are deter~ined employing such suitable measuring e~uipment as the Carey Model 14 Spectrophotometer equipped with an integrating sphere and a 45 light source. The Brightness,~Y values are an indication of the ability of the pigment to reflect the incident lights with a minimum of scattering caused by aggregation and agglomeration of the particles. The higher the4 Y value obtained, the finer the particle size distribution. Higher~ Y values indicate that most of the light is reflected and very little is diffused, Lower~ Y values indicate less reflected light and more light is scattered due to the larger particle size distribution, The procedure employed for determining the Brightness ~Y is to form a spot of dispersed pigment of about 20 millimeters in diameter onto an alumin~lm backed .card or a clear mylar or glass sheet. The control pigment prepared in a similar manner without solvent washing is spotted next to it. A wire wound film applicator is used to draw down the two pools of pigment to the bottom of the card, following which the draw down is dried and cured.
, -8- ~
.
~2S~5 Brightness ~Y measurements are then made using a spectro-photometer. The curve indicated in the drawing is plot of Brightness QY values versus various dispersion times on a Red Devil paint shaker. It is seen that the solvent washed pigment has a higher Brightness ~Y value compared to the control pigment. This indicates that the solvent washed pigment has a higher dispersibility and smaller particle size. The following examples are illustrative of the present invention and are not intended in any way as a limitation upon the scope thereof. Parts and percents are by weight unless otherwise indicated, These examples show that sol~ent washing of iron oxide pigments results in smaller particle sizes, increased dispersibility and higher transparency of the resulting iron oxide pigment.
Example 1 Into a 12000 ml reaction flask was added 161.4 grams of FeS04, 7H20 crystals and 6000 mls of water. To this solution was added ~00 mls of an aqueous solution containing 16,7 weight percent sodium carbonate. By means of an air lance placed into the flask, air was bubbled through the solution forming a slurry of ferric hydroxide until a test with potassium permanganate showed that oxidation to the ferric state was complete. The slurry was then heated at 90C for one hour. The slurry was filtered through Whatman No, 4 filter paper employing a B~chner funnel. The pigment residue was then washed with .
5i~5 8000 mls of water and was dried in a vacuum oven at 105C
for 24 hours. The resulting dry yellow pigment was ground in a mortar with a pestle and sieved through a 200 mesh screen, This was used as the control pigment, Solvent Washing Procedure Into a B~chner funnel was added 150 grams of yellow ferric hydroxide pigment slurry containing a~out 60% water prepared as described above prior to filtration.
This slurry was filtered through Whatman No, 4 filter paper, The residue of pigment was then washed with about 8000 mls of water, This was fo~lowed by 1200 mls of dimethylform-amide (DMF) at the rate of about 100 mls/minute, The DMF
water mixture was then recycled through the pigment until the moisture content of the pigment was reduced to less than 2~ as determined by a Karl Fischer titration, The pigment was then dried in a vacuum oven at 105C for 24 hours, The resulting yellow dry pigment was ground in a mortar with a pestle and sieved through a 200 mesh screen, Dispersion Procedure Into a four-ounce bottle was added 100 grams of 2 mm glass beads and 4,5 grams of a dispersion vehicle con-sisting of 80 weight percent acrylic resin, 4 weight per-cent n-butanol and 16 weight percent xylene and 1,5 grams of the dry DMF washed pigment, The bottle was stoppered with a cap and placed on a Red Devil paint shaker for 15 minutes, ~fter coollng the bottle, 24 grams o~ Let-down -10- , ~
.
. - , .
S~5 Vehicle consisting of 45.2 weigh~ percent acrylic resin, 19.4 weight percent melamine resin, 7.0 weight percent n-butanol and 28.4 weight percent xylene was added to the bottle and reshaken for ~ minutes. The glass beads were filtered out and the filtrate was retained for Brightness testing.
Brightness Test A portion of the above filtrate forming a spot of about 20 mm was poured onto an aluminum backed card. A
control pigment was spotted next to it A "60 micron"
spiral was used to "draw-down" the two pools of pigment to the bottom of the card. The "draw-down" was allowed to air dry for 10 minutes, then oven dried for 30 minutes at 120C. The Brightness ~ Y was then measured employing a -Carey spectrophotome~er with an integrating sphere and a 45 light source. Additional samples were prepared on the Red Devil shaker for various lengths of time with~Y
results as indicated below in Table I.
Table I
Shaker TLme, Minutes Example DMF washed, ~Y 42 50 60 7 Control, ~Y ~2 40 50 60 These data indicate tha~ solven~ washing inhibits ~ aggregation and agglomeration of the particles since the : ' : -.
:
__ !
i~l25~5 Y values are higher for the solvent washed pigment com-pared to the control pigment, Similar differences were - observed for a red pigment produced by calcining the yellow -:
pigment at 280C for 20 minutes prior to the dispersion procedure.
Examples 2-5 The solvent washing procedure of Example 1 was followed except that as indicated various solvents were employed and the pigment was dried at 70C for 24 hours.
The Brightness aY values are tabulated in Table II below, Table II
Brightness ~Y values Shaker time, minutes Example Solvent -I5 30 o 120 2 Ethanol 37 45 55 65
The yellow pigment obtained by this process can be converted to easily dispersible transparent red iron oxide pigment by calcination at temperatures rangi~g from 150C to 400C.
The invention and its advantages will be better understood with reference to the following description taken in connection with the accompanying drawing which illustrates a typical curve obtalned for Brightness values versus dispersion times employing a Red Devil paint shaker. As can be seen, this drawing illustrates that solvent washing results in pigment having greater dispersibility compared to pigment prepared by prior art procedures as indicated by higher Brightness values.
In order to teat the iron oxide pigment, obtained in accordance with the invention a dispersion procedure is employed wherein one and a half grams of the dried pigment are added to a four-ounce bottle containing 100 grams of 2 mm glass beads and 4.5 grams of a Dispersion Vehicle which consists of 80 weight percent acrylic resin, 4 weight percent normal butanol and 16 weight percent xylene. The bottle is stoppered and placed on a paint shaker for various lengths of time, upon which the bottle is cooled and 24 grams of Let-down Vehicle consisting of about ; 45 weight percent acrylic resin, 20 percent melamine resin, 7 percent butanol and 28 percent xylene. The mixture is then re-shaken, the glass beads filtered out, and the filtrate then tested for Brightness ~Y values.
::
_7_ ~ . ~.. . ,.,. ,, ' "
, .. . ~ -,' ,, -The dispersibility of the pigment is conveniently determined ~y tristimulus measurements of the Y values and is the difference between the Y values of the specularly reflected light and the diffusely reflected light, This difference is expressed as the Brightness ~Y value. These values are deter~ined employing such suitable measuring e~uipment as the Carey Model 14 Spectrophotometer equipped with an integrating sphere and a 45 light source. The Brightness,~Y values are an indication of the ability of the pigment to reflect the incident lights with a minimum of scattering caused by aggregation and agglomeration of the particles. The higher the4 Y value obtained, the finer the particle size distribution. Higher~ Y values indicate that most of the light is reflected and very little is diffused, Lower~ Y values indicate less reflected light and more light is scattered due to the larger particle size distribution, The procedure employed for determining the Brightness ~Y is to form a spot of dispersed pigment of about 20 millimeters in diameter onto an alumin~lm backed .card or a clear mylar or glass sheet. The control pigment prepared in a similar manner without solvent washing is spotted next to it. A wire wound film applicator is used to draw down the two pools of pigment to the bottom of the card, following which the draw down is dried and cured.
, -8- ~
.
~2S~5 Brightness ~Y measurements are then made using a spectro-photometer. The curve indicated in the drawing is plot of Brightness QY values versus various dispersion times on a Red Devil paint shaker. It is seen that the solvent washed pigment has a higher Brightness ~Y value compared to the control pigment. This indicates that the solvent washed pigment has a higher dispersibility and smaller particle size. The following examples are illustrative of the present invention and are not intended in any way as a limitation upon the scope thereof. Parts and percents are by weight unless otherwise indicated, These examples show that sol~ent washing of iron oxide pigments results in smaller particle sizes, increased dispersibility and higher transparency of the resulting iron oxide pigment.
Example 1 Into a 12000 ml reaction flask was added 161.4 grams of FeS04, 7H20 crystals and 6000 mls of water. To this solution was added ~00 mls of an aqueous solution containing 16,7 weight percent sodium carbonate. By means of an air lance placed into the flask, air was bubbled through the solution forming a slurry of ferric hydroxide until a test with potassium permanganate showed that oxidation to the ferric state was complete. The slurry was then heated at 90C for one hour. The slurry was filtered through Whatman No, 4 filter paper employing a B~chner funnel. The pigment residue was then washed with .
5i~5 8000 mls of water and was dried in a vacuum oven at 105C
for 24 hours. The resulting dry yellow pigment was ground in a mortar with a pestle and sieved through a 200 mesh screen, This was used as the control pigment, Solvent Washing Procedure Into a B~chner funnel was added 150 grams of yellow ferric hydroxide pigment slurry containing a~out 60% water prepared as described above prior to filtration.
This slurry was filtered through Whatman No, 4 filter paper, The residue of pigment was then washed with about 8000 mls of water, This was fo~lowed by 1200 mls of dimethylform-amide (DMF) at the rate of about 100 mls/minute, The DMF
water mixture was then recycled through the pigment until the moisture content of the pigment was reduced to less than 2~ as determined by a Karl Fischer titration, The pigment was then dried in a vacuum oven at 105C for 24 hours, The resulting yellow dry pigment was ground in a mortar with a pestle and sieved through a 200 mesh screen, Dispersion Procedure Into a four-ounce bottle was added 100 grams of 2 mm glass beads and 4,5 grams of a dispersion vehicle con-sisting of 80 weight percent acrylic resin, 4 weight per-cent n-butanol and 16 weight percent xylene and 1,5 grams of the dry DMF washed pigment, The bottle was stoppered with a cap and placed on a Red Devil paint shaker for 15 minutes, ~fter coollng the bottle, 24 grams o~ Let-down -10- , ~
.
. - , .
S~5 Vehicle consisting of 45.2 weigh~ percent acrylic resin, 19.4 weight percent melamine resin, 7.0 weight percent n-butanol and 28.4 weight percent xylene was added to the bottle and reshaken for ~ minutes. The glass beads were filtered out and the filtrate was retained for Brightness testing.
Brightness Test A portion of the above filtrate forming a spot of about 20 mm was poured onto an aluminum backed card. A
control pigment was spotted next to it A "60 micron"
spiral was used to "draw-down" the two pools of pigment to the bottom of the card. The "draw-down" was allowed to air dry for 10 minutes, then oven dried for 30 minutes at 120C. The Brightness ~ Y was then measured employing a -Carey spectrophotome~er with an integrating sphere and a 45 light source. Additional samples were prepared on the Red Devil shaker for various lengths of time with~Y
results as indicated below in Table I.
Table I
Shaker TLme, Minutes Example DMF washed, ~Y 42 50 60 7 Control, ~Y ~2 40 50 60 These data indicate tha~ solven~ washing inhibits ~ aggregation and agglomeration of the particles since the : ' : -.
:
__ !
i~l25~5 Y values are higher for the solvent washed pigment com-pared to the control pigment, Similar differences were - observed for a red pigment produced by calcining the yellow -:
pigment at 280C for 20 minutes prior to the dispersion procedure.
Examples 2-5 The solvent washing procedure of Example 1 was followed except that as indicated various solvents were employed and the pigment was dried at 70C for 24 hours.
The Brightness aY values are tabulated in Table II below, Table II
Brightness ~Y values Shaker time, minutes Example Solvent -I5 30 o 120 2 Ethanol 37 45 55 65
3 Dimethyl-sulfoxide 45 55 65 75
4 90% Butanol ~' 10% ~ylene 35. 45 55 65 Acetone 35 47 53 65 Control 32 40 50 60 These data indicate that various solvents may be employed for washing the pigment resulting in improved dis-persibility of the pigment.
.
, .
.
, .
Claims (7)
1. In a process for the preparation of transparent iron oxide pigments by forming an aqueous mixture of iron oxide particles, the improvement which comprises:
(a) filtering said iron oxide particles from said mixture and forming a filter cake, (b) washing said filter cake with water, (c) further washing with a solvent miscible with water, immiscible with and non-reactive with the iron oxide, having a boiling point below about 200°C, and having a surface tension of less than 60 dynes/cm, and (d) removing a substantial portion of said solvent from said filter cake to obtain transparent iron oxide pigments.
(a) filtering said iron oxide particles from said mixture and forming a filter cake, (b) washing said filter cake with water, (c) further washing with a solvent miscible with water, immiscible with and non-reactive with the iron oxide, having a boiling point below about 200°C, and having a surface tension of less than 60 dynes/cm, and (d) removing a substantial portion of said solvent from said filter cake to obtain transparent iron oxide pigments.
2. The process of claim 1 further comprising:
(e) heating the pigments obtained in step (d) at temperature range of from 150°C to 400°C.
(e) heating the pigments obtained in step (d) at temperature range of from 150°C to 400°C.
3. The process of claim 1 or 2, wherein the solvent is selected from the group consisting of aliphatic alcohols, glycol ethers, alkanolamines, ketones, and mixtures thereof.
4. The process of claim 1 or 2, wherein the solvent is selected from the group consisting of dimethyl sulfoxide, ethanol, dimethylformamide, acetone and a mixture of 90 weight percent butanol and 10 weight percent xylene.
5. The process of claim 1 or 2, wherein the solvent is dimethylsulfoxide.
6. The process of claim 1 or 2, wherein the solvent is dimethylformamide.
7. A transparent iron oxide pigment as produced by the process of claim 1 or 2.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US80235677A | 1977-06-02 | 1977-06-02 | |
| US802,356 | 1977-06-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1102505A true CA1102505A (en) | 1981-06-09 |
Family
ID=25183487
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA303,500A Expired CA1102505A (en) | 1977-06-02 | 1978-05-16 | Transparent iron oxide pigment prepared by organic solvent washing |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1102505A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4911760A (en) * | 1987-05-15 | 1990-03-27 | Bayer Aktiengesellschaft | Color pure iron oxide pigments, a process for their preparation |
| US6660793B1 (en) | 2000-06-15 | 2003-12-09 | E. I. Du Pont De Nemours And Company | Aqueous coating compositions having improved transparency |
-
1978
- 1978-05-16 CA CA303,500A patent/CA1102505A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4911760A (en) * | 1987-05-15 | 1990-03-27 | Bayer Aktiengesellschaft | Color pure iron oxide pigments, a process for their preparation |
| US6660793B1 (en) | 2000-06-15 | 2003-12-09 | E. I. Du Pont De Nemours And Company | Aqueous coating compositions having improved transparency |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4810305A (en) | Hydrophobic pigments and fillers for incorporation in synthetic resins | |
| CN109923062B (en) | Zirconium nitride powder and method for producing same | |
| KR102123698B1 (en) | Metal azo pigments and pigment preparations produced therefrom | |
| DE4337643C1 (en) | A process for the preparation of water-dispersible alumina bohemian structural grades and use thereof | |
| JP2002201380A (en) | Precipitated silicic acid doped with aluminum, method for producing the same, use of the same, and coating preparation containing the same | |
| US4391893A (en) | Magnetic developers and process for their preparation | |
| JP2000512327A (en) | Modified carbon product and amphiphilic ion-containing composition | |
| EP3252117A1 (en) | Near-infrared ray absorbing microparticle dispersion solution and production method thereof | |
| GB1565057A (en) | Pigmented microporous silica microspheres | |
| EP1506262B1 (en) | Goniochromatic bright pigments | |
| CN101263204B (en) | Colored composite micro-particle and method for producing colored composite micro-particle, rendering material and color filter and ink for inkjet | |
| WO1991004293A9 (en) | Colored metallic pigments | |
| CA1090957A (en) | Dust-free metal chromate pigment composition and process of preparation | |
| CA1102505A (en) | Transparent iron oxide pigment prepared by organic solvent washing | |
| DE102012221880A1 (en) | Toner with improved dielectric loss | |
| EP0927700A1 (en) | Method of producing anhydrous zinc antimonate | |
| EP1672038B1 (en) | Black iron oxide pigments with high tinting strength, resistivity towards reduction and oxidation for colouring polymers and building materials | |
| KR100459620B1 (en) | Bismuth Vanadate Pigments | |
| JP2005298316A (en) | Titanium oxide particle and production method thereof | |
| EP0997500B1 (en) | Fine red iron oxide pigment, and paint or resin composition using the same | |
| JP3907073B2 (en) | Colorant and ink and toner containing the same | |
| JP4399886B2 (en) | Strontium iron oxide particle powder for non-magnetic black pigment and method for producing the same | |
| JPH06279023A (en) | New colored inorganic pigment based on rare earth element and method for synthetic production thereof | |
| US7115164B2 (en) | Preparation of yellow pigments | |
| CA1102506A (en) | Transparent iron oxide pigment prepared by freeze drying |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |