CA1052059A - Treatment of pigment - Google Patents
Treatment of pigmentInfo
- Publication number
- CA1052059A CA1052059A CA255,700A CA255700A CA1052059A CA 1052059 A CA1052059 A CA 1052059A CA 255700 A CA255700 A CA 255700A CA 1052059 A CA1052059 A CA 1052059A
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- CA
- Canada
- Prior art keywords
- soluble compound
- process according
- amount
- aluminium
- pigment
- 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
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Classifications
-
- 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
- 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
- C09C1/36—Compounds of titanium
- C09C1/3607—Titanium dioxide
- C09C1/3653—Treatment with inorganic compounds
- C09C1/3661—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
- C01P2004/82—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases
- C01P2004/84—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases one phase coated with the other
-
- 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)
- Inorganic Compounds Of Heavy Metals (AREA)
Abstract
Abstract of the Disclosure "TREATMENT OF PIGMENT"
A process for the treatment of titanium dioxide pigment in which there is added to a slurry of the pigment a compound of silicon, of aluminium, of zirconium and of titanium, changing the pH of the slurry to 7.5 to 8.5 prior to adding a compound of silicon, an acidic compound of aluminium and an alkaline compound of aluminium thereby producing a coated pigment.
A process for the treatment of titanium dioxide pigment in which there is added to a slurry of the pigment a compound of silicon, of aluminium, of zirconium and of titanium, changing the pH of the slurry to 7.5 to 8.5 prior to adding a compound of silicon, an acidic compound of aluminium and an alkaline compound of aluminium thereby producing a coated pigment.
Description
105'~059 This invention relates to a process for the treatment of a pigment and particularly to the treatment of titanium dioxide pigment.
According to the present inventian a process for the treatment : 5 of titanium dioxide pigment comprises fonming an aqueous dispersion of pigmentary titanium dioxide containing a first water-soluble oompound of silicc~ in an amount of fram 1 to 2% by weight expressed as SiO2, adding to the dispersion a first ac;~;c water-solu~le compound of alu~inium in an amount of fram 1.5 to 2.5% by weight expressed as A1203, an acidic water-soluble compou~d of zircan_um ... . .
in an amount of frcm 0.5 to 1.5% by weight expressed as ZrO2 and an . acidic water-soluble compound of titani~m in an amDunt of fram 1.0 to 2.0~ by T:teight expressed as TiO2, changing the pTI of the d s~ersi~n : to a value in the range 7.5 to 8.5 and then adding to tbe dispersion a second water-soluble compound of silicon in an ambunt ~: from l to 2% by weight expressed as SiO2, a seca.nd acidic water-soluble . oompound of aluminium in an amount of from 1 to 2% by weight expressed : as A1203 and an aLkaiine water-soluble compound of aluminium in an .~ amcunt of fram 0 to 1.5% by weight expressed as A1203, all the .. 20 pero~ntages by weight being based on the weight of TiO2 in the pigmen~
. . and recovering the so treated pigment.
The present inventian provides a process for the treatment of titanium dioxide pigment in such a manner that there beoomes associated with the pigment a nut.~ber of hydrous metal oxides so that :. 25 the pigment when incorporated in a paint has a reduced photochemical : , .
'' ' ' '3~ ' ~ 2 .
105~059 activity. T~,e titanium dioxide pigment which is treated by the process of the present invention is preferably a "sulphate"
pigment, i.e. a calcined titaniu~ dioxide pigment which is prepared by a well known "sulphate" pro oess which involves the y 5 digestion of a titaniferous ore with cancentrated sulphuric acid ; to pr~duce a digestion c~ke which is th~n dissolved in water or dilute acid. The solutian of titanyl sulphate so obtained, after suitable purificatian treatnY~nt, is hydL~olysed in the presence of seed nuclei to precipitate a hydrous form of titanium dioxide . ;, . .
which is subsequently calcined at an el~vated temperature to develop * e pigme~tary properties of the titanium dioxide.
Preferably, the titanium dioxide pigment which is treated by -the prlcr~s of the present inventian is rutile titanium dioxide, i.e. the pigment contains at least 95~ of its TiO2 cantent in the rutile fonm as opposed to the anatase f~rm.
` . Preferably, the titanium dioxide pigment to De treated by the pro oess of the present invention contalns from 0.1 to 0.5% by weight A1203 based on the weight of TiO2. mhis alumina is farmed during the calcination process as a res~lt of the addition to the pigment, ` 20 prior to calcination, of an aluminium oo~pound such as aluminium . ~ . .
sulphate.
- Usually, prior to treatment by the prooess of the present .. ~ .
invention the pigmentary titanium dicxide calciner discharge is .
~ milled in a dry milling process such as by means of a ring or roller . ].
. 25 mill, or hammer mill. m e pigment so obtained is then formed into .'.i. ' ' .- . . .
... . . .
~ ' .
b. - . ., .... ~ ~ .
:
l~)S'~059 an aqueous dispersion throu~h use of a water-soluble oompourd of silioon as the dispersant. Preferably, the titanium dioxide pigment is mixed.with water in the presence of a water-soluble silicate, such as an alkali metal silicate, preferably sodium 5. . silicate, and then wet milled, preferably by means of a sand mill.
m e ~mount of ~he water-soluble compound of silicon ~dded as dispersant is from 0.5 to 1.5~ by weight expresed as SiO2 on the weight of TiO2. Usually during wet milling of the aqueous dispersion . of.pigmentary titanium dioxide no heat is s Q iled. Usually the : 10 concentration of the titan$um dioxide pigment in the dispersion at . - the conclusion of wet milling will be fram 6C0 to lOC0 grams per . litre, although this will depend on the particular process conditions . employed in a particular factory. Subse~uent to wet mi71iig it is desirable to reduce the concentration to the tit~nium dioxide pigm~nt .
ln the sl~y to a value of from 150 to 250 grams per litre. In :
addition the te~ r~ture of the dispersant prior to. carrying out - :
.
. the subsequent treat~ent stages is usually raised to a value of fram 40 to ~s&, preferably about 45C.
To the aqueous dispersian of pigmentary titanium dloxide . 20 containing the water-soluble cc~pcund of silioon there is then ; added a first acidic campound of aluminium in an amount of fram I.5 to 2.5% by weight.expressed as A1203 based on the weight of TiO2 in .~ the pigment. Preferably the amount of the water-solu~b compound of aluminium is fram 1.8 to 2.i% by weight, and the water-soluble cc~pound of aluminium is a~d d in the form of an aqueous solution.
105;~059 Any acidic water-soluble oompound of aluminium that is hydrolysable to fonm a hydrous oxide of aluminium may be employed in the ' prooess of the present invention, and typical'examples are alu~inium ', chloride, aluminium nitrate and aluminium sulphate. Aluminium S ' sulphate is a preferred source of aluminium.
' ~ An acidic water-soluble compound of titanium is also a~ded to the aqueous dispersion containing the water-soluble compcund of , , silica, and the amount of the compcund of titanium is frcm 1.0 to ~' - . 2.0% by weight expressed as TiO2 on the weight of TiO2 in the pigment. Preferably the am~unt of the compounl of titan~um is frcm ' ~ 1.2 to l.6% by weight expressed as TiO2. Usually the waber-soluble ~"' -compound of titanium is ~ d i,n the form of an aqueous solutian ,' ' and suitablP. acidic compounds of titanium are those which are . ,, ~ . . :
! hyd,rolysable to form a hydrous oxide of titanium, ex~mples of which are tltanium tetrachloride and titanyl sulphate. ' ~ ~ , , . r ,`' An acidic water-solu~le ccmpound of zirconium is also added to `' the aqueous dis,persion cantaining the watsr-soluble compound of '~ silicon, in an amou~t of from O.S to 1.5% by wæight expressed as ' ZrO2. Preferably the amount of the oompound of zirconium is from 0.8'to 1.2% by weight expressed as ZrO2. It is also preferred to '~ ', add the water-soluble compound of zirconium in the form of an aqUROUS
, ' solution. The water-soluble compound of zirc~nium which is suitable , ............ .
' ' is one which is hydrolysable to form a hydrous oxide of zirconium, ', and typical examples are ziroonium nitrate and zircanium suiphate. , ,~; 25 .
: , ' , ' . ' , ' .~, ' ~ ' .
~os~os9 Preferably the water-soluble compounds of aluminium, zirconium and titanium are added in the form of a mlxed solutian - of the sulphate of the rnetals. Such a soluti cQntains aluminium sulphate, titanyl sulphate and zirconium sulphate in sulphuric acid and will have a pH of between 0.7 t 1.2. m e ,: mixed solution, when use~d, is added to the dispersion over a period of say 15 to 45 niinutes, and after the additicn the dispersien . is agitated for a further p~riod oE frcm 5 to 15 rninubes to produce - . han~genity.
10 The pH of the aqueou dispersi~.n is then changed to a value to within the range 7.5 to 8.5 by the addition of an aLkali such - as an aqueous alkali rnetal hydroxide, for example, sodium hydroxide, ;. and the aqueous dispersion rnixed for a further period of from 2 to .:
~ . lO rNLnutes. -~-15~ To the.aqueous ~ispers~on of titar~.um dioxide after the ad~ustment of the pH to a value within the range 7.5 to 8.5 there . is then adde~ a seoond water-solub~e ccnFound of silicQn in an anount of from 1 to 2~ ~y wei$ht expressed as SiO2 on the weight of.TiO2 on the pigment~ Preferably the amount of the water-soluble . 20 ccmpcund of silioon is from 1.4 to 1.6% by wei~ht expressed as SiO2.
:~ The water-soluble compound of siIicon will usually be a similar cQmpcund to that added previously to the aqueous disparsion and preferably is an alkali metal silicate such as sodium silicate.
. . Typlcal~y the water-soluble compound of silicon is added to the aqueous dispersion over a pariod of fram 10 to 20 minutes, and after ' , . .
'' .
- . .
'- 1052~59 the addition has been oompleted the aqueous dispersion is mixed for a period of from 5 to 15 minutes.
A seoond acidic water-soluble oompound of aluminium is then added to the aqueous dispersion in an amount of from 1.0 to 2.0% by weiqht expressed as A1203 on the weight of TiO2 in the pigment, and preferably from 1.2 to 1.7% bi weight as A1203. Any acidic water-soluble cc~pound of aluminium may be employed which is hydrolysable to produce a hydL~ous oxide of aluminium, and typical aluminium salts which are useful are aluminium sulphate and aluminium nitrate, although it is preferred to add aluminium sulphate. m e : aluminium salt is preferably-added in the form of a solutian over a period of from 5 to 20 minutes, usually between 12 and 16 minutes and mixed after the oampletian of the addi~ion for a further S to .
~: lS minutes.
- 15 ~n alkaline reacting water-soluble oompound of aluminium is then added to the aqyeous dispersion of titanium dioxide in an .. ': ' ' '. ' amount of from O to 1.5 weight percent expressed as A1203 on the : weight of TiO2 in the pigment. Pref~rably the amount of the alkaline wat~r-soluble oompound of aluminium is from 0.7 to 1.2% by weight expressed as A1~03, and preferably the compound i8 added in the form of an aqueous solution.- Typical alkaline water-soluble ccmpc nd8 of alumina are the aLkali metal aluminates such as ~: sodium aluminate, and if desired the solution may also cantain an alkali metal hydroxide such as sodium hydroxide. Typically the 2S water soluble ccmpound of aluminium 1s added over a period of frcm , .
:-. ' .
105'~Q59 10 to 20 minutes, and after the addition has been completed the aqueous dispersion is mixed for a further period of from 20 to 60 minutes to achieve homogenity. After the addition of the reagents has been completed the aqueous dispersion is filtered 5 ' and the treated titanium dioxide pigment reoovered, washed and dried. If desired, the dried treated titanium dioxide pigment may be milled in a fluid energy mill optionally in the presence of an organic treating agent such as an amine, an alkanolamine or ... .
a polyol.
The pigments obtain,ed by the process of the present invention ~' are particularly usell for the manufacture of paints, particularly - oleoresinous paints and when so used have a reduced photochemical activity, i.e. reduced chaIking, improved gloss r~etention and reduced ' weight loss of the paint film.
' It is b'elieved that du~ing the process of the present inv!enti~n there becGmes associabed with the pigmentary particles of titanium . , .
. ' dioKide a hydrous oxide of silicon and hydrous oxide of aluminium .
- and of ziroonium. It is believed that the particles of pigmentary titanium dioxlde become coated with these hydrous oxides, but it m~y b'e'that there is also precipitated into association with the pigment one or re metal silicat'es. .
m e present invention is illustrated in the following Examples.
.
~ 25 :; ' ' ' - .
- lOS;~QS9 ;
Example 1 A 2156g sample of dry milled, alumina (0.13%) additioned, rutile TiO2 "sulphate" based pigment was suspanded in 2355 mls of distilled water. To the suspension were added 225 mls of sodium silicate solution (10.0~ SiO2 and 3.18% Na20) and 5140 mls of Gttawa sand. The slurry was sandmilled for 60 minutes in an 8" diameter pot with 4 x 5" diameter discs (separation 1.5") a~
1890 r.p.~. m e sand was separated from the pigment by passing the slurry sucoessively through a 100 mesh and then a 325 mesh sieve.
Sand-free slurry containing 8COg TiO2 was diluted to 200g 1 - with distilled water, stirred to ensure efficient mixing during j subsequent reagent additians, and heated to 45C. m e pH at thls ;~ stage was 10.4. 216 mls of a mixed acidic solution of aluminium su~phate, zirconium orthosulphate and titanyl sulphate ~7.4~ A1203, . . . .
3.7% Zr2 and 5.5% 1'iO2) were added at a rate of 10.8 mls par .
minute. m e slurry was mixed for 10 minutes and the pH at the end of this stage was 1.3.
~he slurry pH was changed, over 10 minutes, to pH 8.0 with
According to the present inventian a process for the treatment : 5 of titanium dioxide pigment comprises fonming an aqueous dispersion of pigmentary titanium dioxide containing a first water-soluble oompound of silicc~ in an amount of fram 1 to 2% by weight expressed as SiO2, adding to the dispersion a first ac;~;c water-solu~le compound of alu~inium in an amount of fram 1.5 to 2.5% by weight expressed as A1203, an acidic water-soluble compou~d of zircan_um ... . .
in an amount of frcm 0.5 to 1.5% by weight expressed as ZrO2 and an . acidic water-soluble compound of titani~m in an amDunt of fram 1.0 to 2.0~ by T:teight expressed as TiO2, changing the pTI of the d s~ersi~n : to a value in the range 7.5 to 8.5 and then adding to tbe dispersion a second water-soluble compound of silicon in an ambunt ~: from l to 2% by weight expressed as SiO2, a seca.nd acidic water-soluble . oompound of aluminium in an amount of from 1 to 2% by weight expressed : as A1203 and an aLkaiine water-soluble compound of aluminium in an .~ amcunt of fram 0 to 1.5% by weight expressed as A1203, all the .. 20 pero~ntages by weight being based on the weight of TiO2 in the pigmen~
. . and recovering the so treated pigment.
The present inventian provides a process for the treatment of titanium dioxide pigment in such a manner that there beoomes associated with the pigment a nut.~ber of hydrous metal oxides so that :. 25 the pigment when incorporated in a paint has a reduced photochemical : , .
'' ' ' '3~ ' ~ 2 .
105~059 activity. T~,e titanium dioxide pigment which is treated by the process of the present invention is preferably a "sulphate"
pigment, i.e. a calcined titaniu~ dioxide pigment which is prepared by a well known "sulphate" pro oess which involves the y 5 digestion of a titaniferous ore with cancentrated sulphuric acid ; to pr~duce a digestion c~ke which is th~n dissolved in water or dilute acid. The solutian of titanyl sulphate so obtained, after suitable purificatian treatnY~nt, is hydL~olysed in the presence of seed nuclei to precipitate a hydrous form of titanium dioxide . ;, . .
which is subsequently calcined at an el~vated temperature to develop * e pigme~tary properties of the titanium dioxide.
Preferably, the titanium dioxide pigment which is treated by -the prlcr~s of the present inventian is rutile titanium dioxide, i.e. the pigment contains at least 95~ of its TiO2 cantent in the rutile fonm as opposed to the anatase f~rm.
` . Preferably, the titanium dioxide pigment to De treated by the pro oess of the present invention contalns from 0.1 to 0.5% by weight A1203 based on the weight of TiO2. mhis alumina is farmed during the calcination process as a res~lt of the addition to the pigment, ` 20 prior to calcination, of an aluminium oo~pound such as aluminium . ~ . .
sulphate.
- Usually, prior to treatment by the prooess of the present .. ~ .
invention the pigmentary titanium dicxide calciner discharge is .
~ milled in a dry milling process such as by means of a ring or roller . ].
. 25 mill, or hammer mill. m e pigment so obtained is then formed into .'.i. ' ' .- . . .
... . . .
~ ' .
b. - . ., .... ~ ~ .
:
l~)S'~059 an aqueous dispersion throu~h use of a water-soluble oompourd of silioon as the dispersant. Preferably, the titanium dioxide pigment is mixed.with water in the presence of a water-soluble silicate, such as an alkali metal silicate, preferably sodium 5. . silicate, and then wet milled, preferably by means of a sand mill.
m e ~mount of ~he water-soluble compound of silicon ~dded as dispersant is from 0.5 to 1.5~ by weight expresed as SiO2 on the weight of TiO2. Usually during wet milling of the aqueous dispersion . of.pigmentary titanium dioxide no heat is s Q iled. Usually the : 10 concentration of the titan$um dioxide pigment in the dispersion at . - the conclusion of wet milling will be fram 6C0 to lOC0 grams per . litre, although this will depend on the particular process conditions . employed in a particular factory. Subse~uent to wet mi71iig it is desirable to reduce the concentration to the tit~nium dioxide pigm~nt .
ln the sl~y to a value of from 150 to 250 grams per litre. In :
addition the te~ r~ture of the dispersant prior to. carrying out - :
.
. the subsequent treat~ent stages is usually raised to a value of fram 40 to ~s&, preferably about 45C.
To the aqueous dispersian of pigmentary titanium dloxide . 20 containing the water-soluble cc~pcund of silioon there is then ; added a first acidic campound of aluminium in an amount of fram I.5 to 2.5% by weight.expressed as A1203 based on the weight of TiO2 in .~ the pigment. Preferably the amount of the water-solu~b compound of aluminium is fram 1.8 to 2.i% by weight, and the water-soluble cc~pound of aluminium is a~d d in the form of an aqueous solution.
105;~059 Any acidic water-soluble oompound of aluminium that is hydrolysable to fonm a hydrous oxide of aluminium may be employed in the ' prooess of the present invention, and typical'examples are alu~inium ', chloride, aluminium nitrate and aluminium sulphate. Aluminium S ' sulphate is a preferred source of aluminium.
' ~ An acidic water-soluble compound of titanium is also a~ded to the aqueous dispersion containing the water-soluble compcund of , , silica, and the amount of the compcund of titanium is frcm 1.0 to ~' - . 2.0% by weight expressed as TiO2 on the weight of TiO2 in the pigment. Preferably the am~unt of the compounl of titan~um is frcm ' ~ 1.2 to l.6% by weight expressed as TiO2. Usually the waber-soluble ~"' -compound of titanium is ~ d i,n the form of an aqueous solutian ,' ' and suitablP. acidic compounds of titanium are those which are . ,, ~ . . :
! hyd,rolysable to form a hydrous oxide of titanium, ex~mples of which are tltanium tetrachloride and titanyl sulphate. ' ~ ~ , , . r ,`' An acidic water-solu~le ccmpound of zirconium is also added to `' the aqueous dis,persion cantaining the watsr-soluble compound of '~ silicon, in an amou~t of from O.S to 1.5% by wæight expressed as ' ZrO2. Preferably the amount of the oompound of zirconium is from 0.8'to 1.2% by weight expressed as ZrO2. It is also preferred to '~ ', add the water-soluble compound of zirconium in the form of an aqUROUS
, ' solution. The water-soluble compound of zirc~nium which is suitable , ............ .
' ' is one which is hydrolysable to form a hydrous oxide of zirconium, ', and typical examples are ziroonium nitrate and zircanium suiphate. , ,~; 25 .
: , ' , ' . ' , ' .~, ' ~ ' .
~os~os9 Preferably the water-soluble compounds of aluminium, zirconium and titanium are added in the form of a mlxed solutian - of the sulphate of the rnetals. Such a soluti cQntains aluminium sulphate, titanyl sulphate and zirconium sulphate in sulphuric acid and will have a pH of between 0.7 t 1.2. m e ,: mixed solution, when use~d, is added to the dispersion over a period of say 15 to 45 niinutes, and after the additicn the dispersien . is agitated for a further p~riod oE frcm 5 to 15 rninubes to produce - . han~genity.
10 The pH of the aqueou dispersi~.n is then changed to a value to within the range 7.5 to 8.5 by the addition of an aLkali such - as an aqueous alkali rnetal hydroxide, for example, sodium hydroxide, ;. and the aqueous dispersion rnixed for a further period of from 2 to .:
~ . lO rNLnutes. -~-15~ To the.aqueous ~ispers~on of titar~.um dioxide after the ad~ustment of the pH to a value within the range 7.5 to 8.5 there . is then adde~ a seoond water-solub~e ccnFound of silicQn in an anount of from 1 to 2~ ~y wei$ht expressed as SiO2 on the weight of.TiO2 on the pigment~ Preferably the amount of the water-soluble . 20 ccmpcund of silioon is from 1.4 to 1.6% by wei~ht expressed as SiO2.
:~ The water-soluble compound of siIicon will usually be a similar cQmpcund to that added previously to the aqueous disparsion and preferably is an alkali metal silicate such as sodium silicate.
. . Typlcal~y the water-soluble compound of silicon is added to the aqueous dispersion over a pariod of fram 10 to 20 minutes, and after ' , . .
'' .
- . .
'- 1052~59 the addition has been oompleted the aqueous dispersion is mixed for a period of from 5 to 15 minutes.
A seoond acidic water-soluble oompound of aluminium is then added to the aqueous dispersion in an amount of from 1.0 to 2.0% by weiqht expressed as A1203 on the weight of TiO2 in the pigment, and preferably from 1.2 to 1.7% bi weight as A1203. Any acidic water-soluble cc~pound of aluminium may be employed which is hydrolysable to produce a hydL~ous oxide of aluminium, and typical aluminium salts which are useful are aluminium sulphate and aluminium nitrate, although it is preferred to add aluminium sulphate. m e : aluminium salt is preferably-added in the form of a solutian over a period of from 5 to 20 minutes, usually between 12 and 16 minutes and mixed after the oampletian of the addi~ion for a further S to .
~: lS minutes.
- 15 ~n alkaline reacting water-soluble oompound of aluminium is then added to the aqyeous dispersion of titanium dioxide in an .. ': ' ' '. ' amount of from O to 1.5 weight percent expressed as A1203 on the : weight of TiO2 in the pigment. Pref~rably the amount of the alkaline wat~r-soluble oompound of aluminium is from 0.7 to 1.2% by weight expressed as A1~03, and preferably the compound i8 added in the form of an aqueous solution.- Typical alkaline water-soluble ccmpc nd8 of alumina are the aLkali metal aluminates such as ~: sodium aluminate, and if desired the solution may also cantain an alkali metal hydroxide such as sodium hydroxide. Typically the 2S water soluble ccmpound of aluminium 1s added over a period of frcm , .
:-. ' .
105'~Q59 10 to 20 minutes, and after the addition has been completed the aqueous dispersion is mixed for a further period of from 20 to 60 minutes to achieve homogenity. After the addition of the reagents has been completed the aqueous dispersion is filtered 5 ' and the treated titanium dioxide pigment reoovered, washed and dried. If desired, the dried treated titanium dioxide pigment may be milled in a fluid energy mill optionally in the presence of an organic treating agent such as an amine, an alkanolamine or ... .
a polyol.
The pigments obtain,ed by the process of the present invention ~' are particularly usell for the manufacture of paints, particularly - oleoresinous paints and when so used have a reduced photochemical activity, i.e. reduced chaIking, improved gloss r~etention and reduced ' weight loss of the paint film.
' It is b'elieved that du~ing the process of the present inv!enti~n there becGmes associabed with the pigmentary particles of titanium . , .
. ' dioKide a hydrous oxide of silicon and hydrous oxide of aluminium .
- and of ziroonium. It is believed that the particles of pigmentary titanium dioxlde become coated with these hydrous oxides, but it m~y b'e'that there is also precipitated into association with the pigment one or re metal silicat'es. .
m e present invention is illustrated in the following Examples.
.
~ 25 :; ' ' ' - .
- lOS;~QS9 ;
Example 1 A 2156g sample of dry milled, alumina (0.13%) additioned, rutile TiO2 "sulphate" based pigment was suspanded in 2355 mls of distilled water. To the suspension were added 225 mls of sodium silicate solution (10.0~ SiO2 and 3.18% Na20) and 5140 mls of Gttawa sand. The slurry was sandmilled for 60 minutes in an 8" diameter pot with 4 x 5" diameter discs (separation 1.5") a~
1890 r.p.~. m e sand was separated from the pigment by passing the slurry sucoessively through a 100 mesh and then a 325 mesh sieve.
Sand-free slurry containing 8COg TiO2 was diluted to 200g 1 - with distilled water, stirred to ensure efficient mixing during j subsequent reagent additians, and heated to 45C. m e pH at thls ;~ stage was 10.4. 216 mls of a mixed acidic solution of aluminium su~phate, zirconium orthosulphate and titanyl sulphate ~7.4~ A1203, . . . .
3.7% Zr2 and 5.5% 1'iO2) were added at a rate of 10.8 mls par .
minute. m e slurry was mixed for 10 minutes and the pH at the end of this stage was 1.3.
~he slurry pH was changed, over 10 minutes, to pH 8.0 with
2.75M sodium hydrcxide and mixed for 5 minutes. 120 mls of sodium silicate solution (10.0% SiO2 and 3.18% Na20) were added at a rate - of 8 mls per minute and mixed fo~ 10 minutes. m e pH at the end of this stage was 8.8. 129 mls of aluminium sulphate solution -(9.3% A1203) were added at a rate of 8.6 mls per minute and the slurry mlxad for 10 minutes. The pH at the end of this stage was ,~ ' . , _g_ 105'~059 ;~
3.6. 114 I~S of caustic sodium alumlnate (8.2% A1203 and 19.4%
Na20) were added at a rate of 7.6 mls per minute and the slurry was mixed for a further 40 minutes. The pH at the end of this stage was 8Ø
The treated titanium diaxide pigment was separated from the 1 sluriy by filtration washed twice wlth distilled wat~r, reslurried j in distilled water, again filtered and washed twice then dried for 15 holrs at 105C. The dried pigment was fluid energy milled in a laboratory 6" air microniser.
The pigment so obtained was incorporated in a stoving paint based an a thermoplastic acrylic resin (P æaloid A21JParaloid B99/
Santicizer 16) with a pigment:binder ratio of 0.5:1. Coated stainless steel panels were prepared, stoved at 120& for 30 minutes, , tested in a Marr Weatherameter for v æious periods of time. The dNrabilit exp~essed as Gloss reading (G) and Chalk rating (C) were I taken. -i m e results are ccmpared with those of a control being similar paint cantaining a titanium dioxide pigment havin~ acceptable properties and having a a~ating of hydrous titania (1% by weight as TiO2), hydrous alumina (2.5~ A1203 by weight) and hydrous silica (1.5% SiO2) and prepared by a canventional method.
The pigment was also-incorporated in a sto~ring paint based on a therm~setting acrylic resin system with a pigment/binder ratio of 1.0:1Ø Coa~ed stainless steel panels were prepared, stoved at 120C for 30 minutes ~nd tested in a Marr Weatherometer. The ` 10$'~059 durability expressed as Gloss reading (G) and Chalk rating ~C) were determined. Similar paints containing a titanium dioxide , pigment having a ooating of hydrcus titania (1~ by weight as TiO2) and hydrous alumina (2.$% A1203 by weight) and hydrous , 5 ' silica (1.5~ SiO2) were prepared and tested as the conLrol.
'; The ~igment was also tested to determine thelr stoving gloss after baking at different temp#ratures in an `. alkyd/urea formaldehyde stoving system, and oc~pared with those `' obtained using a titanium dioxide pigmént coated with alumina ~:, 10 6% as A1203 and 1 to 2~ TiO2.
. ` me results of these tests are shown below : ' :
... . . . . . .
:~: . , TABLE 1 .
. Durabilit~ in ther~c~lastic acrylic resIn ` Af,ter Time (Hours) ''~ ' " 15 , - Tb~t I-nltl 1 25~ 500 7~0 _ 1250 ~ . ~ G 90 82 ,68 71 . 53- 55 ~.
. C, 10 9 9 9 9 9 ~ . . C~ltrol G 86 84 63 52 25 1 : ' ' ' ' . C 10 9 9 9 8 6 : ' `
. , - - ' .
.
. ~ - .
. ~ -:. ' :
. . .
1()5;~059 `
,, .
Durability in thermDset~ing acrylic resLns After Time ~Hours Example 1 Test ¦ Initia~ ~ 500 1 G lCO 95 85 73 60 44 Control G 95 95 77 50 32 16 .` ' TAe LE 3 . ~ . . . ~ _ .
Stoving gloss ¦
alple normai sghedule ¦ overbakl800h 1 77.0 33.0 Cb=tr~l 67.0 16.5 Example 2 A 2156 gram sample of dry milled rutile i'sulphate" titanium dioxide base pigment was susp~nded in 2330 mls of distilled water and 323 mls sodium silicate soluti~n (10.0~ SiO2 and 3.18% Na20) were added. 5140 mls of Ottawa sand was added to the slurry which was then milled for 60 minutes in an 8" diameter pot with 4 x 5"
discs ~separation 1.5") at 1890 r.p.m. me sand was separated from the pigment by passing the slurry successively ~h~ough a 100 mesh then a 325 mesh sieve. Sand-free slurry o~ntaining lOCO grams of . .
105'~059 pigment was taken, diluted to 200 gl 1 with distilled water, stirred to ensure efficient mixing during subsequent reagent additi~ns and heated to 45C. The pH at this stage was 9.6.
270 mls of a mixed acidic solution of aluminium sulphate, ziroonium orthosulphate and titanyl sulphate (7.4% A1203, 3.7~
Zr2 and 5.4% TiO2) were added at a rate of 13.5 mls per minute ; and mixed ~or 10 minutes. The pH at this stage was 1.2. The pH of the slurry was raised to 8.0 with 2.75M sodium hydroxide ovar 10 minutes. 150 mls sodiwm silicate solution ~10.0% SiO2 and 3.18% Na20) at a rate of 10 l~s per minute and the slurry mixed for 10 minutes. The pH at this stage was 8.6. 252 mls of aluminium sulphate (10.1% A1203) was added at a rate of 10 mls per minute. During this ~ddition the pH of the slurry fell to
Na20) were added at a rate of 7.6 mls per minute and the slurry was mixed for a further 40 minutes. The pH at the end of this stage was 8Ø
The treated titanium diaxide pigment was separated from the 1 sluriy by filtration washed twice wlth distilled wat~r, reslurried j in distilled water, again filtered and washed twice then dried for 15 holrs at 105C. The dried pigment was fluid energy milled in a laboratory 6" air microniser.
The pigment so obtained was incorporated in a stoving paint based an a thermoplastic acrylic resin (P æaloid A21JParaloid B99/
Santicizer 16) with a pigment:binder ratio of 0.5:1. Coated stainless steel panels were prepared, stoved at 120& for 30 minutes, , tested in a Marr Weatherameter for v æious periods of time. The dNrabilit exp~essed as Gloss reading (G) and Chalk rating (C) were I taken. -i m e results are ccmpared with those of a control being similar paint cantaining a titanium dioxide pigment havin~ acceptable properties and having a a~ating of hydrous titania (1% by weight as TiO2), hydrous alumina (2.5~ A1203 by weight) and hydrous silica (1.5% SiO2) and prepared by a canventional method.
The pigment was also-incorporated in a sto~ring paint based on a therm~setting acrylic resin system with a pigment/binder ratio of 1.0:1Ø Coa~ed stainless steel panels were prepared, stoved at 120C for 30 minutes ~nd tested in a Marr Weatherometer. The ` 10$'~059 durability expressed as Gloss reading (G) and Chalk rating ~C) were determined. Similar paints containing a titanium dioxide , pigment having a ooating of hydrcus titania (1~ by weight as TiO2) and hydrous alumina (2.$% A1203 by weight) and hydrous , 5 ' silica (1.5~ SiO2) were prepared and tested as the conLrol.
'; The ~igment was also tested to determine thelr stoving gloss after baking at different temp#ratures in an `. alkyd/urea formaldehyde stoving system, and oc~pared with those `' obtained using a titanium dioxide pigmént coated with alumina ~:, 10 6% as A1203 and 1 to 2~ TiO2.
. ` me results of these tests are shown below : ' :
... . . . . . .
:~: . , TABLE 1 .
. Durabilit~ in ther~c~lastic acrylic resIn ` Af,ter Time (Hours) ''~ ' " 15 , - Tb~t I-nltl 1 25~ 500 7~0 _ 1250 ~ . ~ G 90 82 ,68 71 . 53- 55 ~.
. C, 10 9 9 9 9 9 ~ . . C~ltrol G 86 84 63 52 25 1 : ' ' ' ' . C 10 9 9 9 8 6 : ' `
. , - - ' .
.
. ~ - .
. ~ -:. ' :
. . .
1()5;~059 `
,, .
Durability in thermDset~ing acrylic resLns After Time ~Hours Example 1 Test ¦ Initia~ ~ 500 1 G lCO 95 85 73 60 44 Control G 95 95 77 50 32 16 .` ' TAe LE 3 . ~ . . . ~ _ .
Stoving gloss ¦
alple normai sghedule ¦ overbakl800h 1 77.0 33.0 Cb=tr~l 67.0 16.5 Example 2 A 2156 gram sample of dry milled rutile i'sulphate" titanium dioxide base pigment was susp~nded in 2330 mls of distilled water and 323 mls sodium silicate soluti~n (10.0~ SiO2 and 3.18% Na20) were added. 5140 mls of Ottawa sand was added to the slurry which was then milled for 60 minutes in an 8" diameter pot with 4 x 5"
discs ~separation 1.5") at 1890 r.p.m. me sand was separated from the pigment by passing the slurry successively ~h~ough a 100 mesh then a 325 mesh sieve. Sand-free slurry o~ntaining lOCO grams of . .
105'~059 pigment was taken, diluted to 200 gl 1 with distilled water, stirred to ensure efficient mixing during subsequent reagent additi~ns and heated to 45C. The pH at this stage was 9.6.
270 mls of a mixed acidic solution of aluminium sulphate, ziroonium orthosulphate and titanyl sulphate (7.4% A1203, 3.7~
Zr2 and 5.4% TiO2) were added at a rate of 13.5 mls per minute ; and mixed ~or 10 minutes. The pH at this stage was 1.2. The pH of the slurry was raised to 8.0 with 2.75M sodium hydroxide ovar 10 minutes. 150 mls sodiwm silicate solution ~10.0% SiO2 and 3.18% Na20) at a rate of 10 l~s per minute and the slurry mixed for 10 minutes. The pH at this stage was 8.6. 252 mls of aluminium sulphate (10.1% A1203) was added at a rate of 10 mls per minute. During this ~ddition the pH of the slurry fell to
4.5 and was maintained in t~le ranse pH 4.0-4.5 by the simultdnecus but separate addition of 275M sodium hydroxide. At this stage the pH was 4.5. The slurry pH was raised to pH 8.0 with 2.75M
sodium hydroxide over 15 mir.~ites and maintained at pH 8.0 for 45 . minutes.
m e treated titanium dioxide was recovered by filtration. The filter cake wa~ washed twi oe with distilled water, reslurried in distilled water, refiltered and again washed twice. The filter cake was additioned with 0.4% (on weight of pigment) triethanolamine dried for 16 hours at 105C then fluid energy milled (twioe) in an 8'! steam microniser.
, ' 105'~059 Ex~,~le 3 A 2156 gram sample of dry ~illed rutile "sulphate" titanium dioxide base pigment was suspended in 2330 mls of distilled water and 108 mls of sodium silicate solutian (10.0% SiO2 and 3.18% Na20) were added. 5140 mls Ottawa sand were added to the slurxy whlch was then milled for 60 minutes in an 8" diameter pot with 4 x 5" discs (sep æation 1.5"-) at 1890 r.p.m. m e sand was separated from the pigment by passing the pigment successively through a 100 mesh ~len a 325 mesh sieve. Sand-free slurry ccntainln~ 1 kg of pigment was taken, diluted to 200 gl 1 with distilled water, stirred to ensure efficient mixing during ,subsequent reagent additions and heated,to 45& . The pH at this ~
stage was 8.9. - , 270 mls of a mixed acidic solutian of aluminium sulphate, -, zirconium orth~sulphate and titanyl sulphate (7.4% A1203, 3.7%
ZrO2, 5.4% TiO2) w~,e added at a rate of 13.5 mls per minute and mixed for 10 minutes. At this stage the pH was 1.2. The pH of the sl~rry was raised to 8.0 with 2.75~ sodium hydroxide over 10 minutes. 150 mls sodium silicate solution (10.0% SiO2 and 3.18%, Na20) were added at a rate of 10 ~ls per minute ar.d mixed for 10 minutes. me pH at this stage was 8.8. 152 mls of aluminium sulphate solution (10.1% A1203) were added at a rate of 10 mls per minute and mixed for O minutes. The pH at this stage was 3.5.
90 mls of caustic sodium aluminate solution (8.2% A1203 and 19.0 Na20) were a~ded at a rate of 9 mls per minute and mixed for 45 minutes. The pH at this stage was 8Ø
~ ' . ' ' ''' ".
105'~059 , The treated titanium dioxide was recovered by filtration.
! T,he filter cake was washed twice with distiiled water, reslurried in distilled water, refilbered and again washed twioe . The filter cake was additioned with 0.4% triethanolamine (on weight of pigment1, dried for 16 hours at 105& then fluid energy milled (twi oe~ in an 8" steam micronlser.
Example 4 A 2156 gram sample of dry milled rutile "sulphate" titanium dioxide base pigment was suspended in 2330 mls of distilled water and 323 mls of sodiu~ silicate solution (10.0% SiO2 and~3.18%
Na20) were added. 5140 mls Ottawa sand were added to the slurry -~ which was then milled~,for 60 minutes in an 8" diameter,pot with ~; 4 x 5" discs (separation 1.5") at 1890 r.p.m. The sand was separated from the pigment by passing the slurry suc oessi~ely through a 100 mesh and then a 325 mesh sieve. Sand-free slurry ocntaining 1 kg of titanium dioxide was diluted to 200 gl 1 with distilled wat~r~
stlrred to ensure efficient mixing,during subse~uent reagent addit1ons and heated to 45C. The pH at this stage was 9.2.
295 mls of a mixed acidic solution of aluminium sulphate, zirconium orthosulphate and titanyl sulphate (7.8% A1203, 1.9% ZrO2 ,~ , and 5.6~ TiO2) were added at a rate of 15 mls pex minute and mixed for 10 minutes. At the end of this stage the pH was 1.1. The slurry pH was adjusted to 8.0 with 2.75M sodium hydroxide over 15 minutes.
150 ~ls of sodium silicate solution ~10.0~ SiO2 and 3.18% Na20) were added at a rate of 10 mls per minute and mixed for 10 minutes. m e . .
.
, -15-, 105;~059 pH at this stdge was 8.3. 152 mls of aluminium sulphate solution tlO.1% A1203) were added at a rate of 10 mls per minut6~ then mi~ed for 5 minutes. The pH at this stage was 3.2. 93 mls of caustic sodium aluninate (8.2% A1203 and 19.0%
N~20) were added at a rate of 6.2 mls per minute then mixed for 45 minutes. me pH dt this stage was 8Ø
me treated t;tanium dioxide pigment was rec~vered by filtration. The filter cake ~as w~shea twice with distilled water, reslurried in distilïed water, refiltered and again -10 washed twioe. me pigment was a~diticned with triethanolamine (0.4% on weight of pigr~nt), dried for 16 hours at 105&, then fluid Pnergy milled ttwice) in an 8" steam microniser.
Exanple 5 - A 2156 gram sample of dly milled rutile TiO2 "sulphate"
based pign~nt ~Jas suspended in 2355 mlsi of <iistilled water. To the suspension were added 323 mls sodiun silicate solutian (1096 SiO2 and 3.18% Na O) and 5140 mls ~f Otta~a sand. The slurry was sand-milled for 60 ~in ~tes in an 8" dic~neter pot with 4 x 5"
di~aneter discs (separation 1.5") at 1890 r.p.m. me sc~d was separated i~rcm the pis[nent by passing the SiUrLy successively through a lCO mesh and then 325 mesh sieve.
The sand-free slurry was diluted to 4.54 litres at 220 g/l TiO2 with distilled water, stirred to ensure efficient mixing during subsequ~ reagent additicns, and heated to 45C. me pH
at this stage was 9.6.
'~', .
. ~ .
~os~os9 298 mls of an acidic solution of aluminium sulphate, ziroonium, orthosulphate and titanyl sulphate ~7.4% A1203, 3 7% Zr2 and 5.5~ TiO2) were added at a rate of 14.9 mls per minute. The slurry was mixed for 10 minutes and the pH
at this stage was 1.3.
The slurry pH was Ghanged, over 10 minutes, to pH 8.0 with - 2.75M sodium hydro~ide and mixed for 5 minutes. 150 mls of sodium - silicate solution (10% SiO2 and 3.18% ,~a20) were added at a rate of 15 mls per minute and mixed for 10 minubes. The.pH at this stage was 8.6.
- -54 mls of aluminium sulphate solution (9.3% A1203) were added - at a rate of 11 mls per minute and the slurry mixed for 10 mlnutes.
T.he pH at the end of this stage was 4.1.
85 mls of caustic sodiu~ al~ nate (8.2~ A1203 and 19.4~ Na20) were-added at a rate of 7 mls per minute and the slurry was mixed.
for a further 40 minutes.
e pH at the end-of thls stage was 8Ø m e treated titanium dioxide pigment was separated from the slurry by filtration, washed twioe w~th distilled water, reslurried in distilled water, again - ~ 20 filtered and washed twice then additioned with triethanolamine : (0.4% on TiO2), dried for 16 hours at 105C. The dried pigment ~tas . fluid energy milled in a laboratory 8" steam microniser.
: The pigment so obtained in Examples 2, 3, 4 and 5 was incorporated in a stoving palnt k~sed on a thermopla~stic acrylic resin sysbem with a pigment:binder ratio of 0.5:1. Coated stainless . ' ' ,' ' . .
lOS;~059 steel panels were prepared, stoved at 120C for 30 minutes and tested in a Marr Weatherometer to determine their durability expressed as Gloss reading (G) a~d Chalk rating (C).
e results are ,pared with thos~ of a cc~ntrc,l being
sodium hydroxide over 15 mir.~ites and maintained at pH 8.0 for 45 . minutes.
m e treated titanium dioxide was recovered by filtration. The filter cake wa~ washed twi oe with distilled water, reslurried in distilled water, refiltered and again washed twice. The filter cake was additioned with 0.4% (on weight of pigment) triethanolamine dried for 16 hours at 105C then fluid energy milled (twioe) in an 8'! steam microniser.
, ' 105'~059 Ex~,~le 3 A 2156 gram sample of dry ~illed rutile "sulphate" titanium dioxide base pigment was suspended in 2330 mls of distilled water and 108 mls of sodium silicate solutian (10.0% SiO2 and 3.18% Na20) were added. 5140 mls Ottawa sand were added to the slurxy whlch was then milled for 60 minutes in an 8" diameter pot with 4 x 5" discs (sep æation 1.5"-) at 1890 r.p.m. m e sand was separated from the pigment by passing the pigment successively through a 100 mesh ~len a 325 mesh sieve. Sand-free slurry ccntainln~ 1 kg of pigment was taken, diluted to 200 gl 1 with distilled water, stirred to ensure efficient mixing during ,subsequent reagent additions and heated,to 45& . The pH at this ~
stage was 8.9. - , 270 mls of a mixed acidic solutian of aluminium sulphate, -, zirconium orth~sulphate and titanyl sulphate (7.4% A1203, 3.7%
ZrO2, 5.4% TiO2) w~,e added at a rate of 13.5 mls per minute and mixed for 10 minutes. At this stage the pH was 1.2. The pH of the sl~rry was raised to 8.0 with 2.75~ sodium hydroxide over 10 minutes. 150 mls sodium silicate solution (10.0% SiO2 and 3.18%, Na20) were added at a rate of 10 ~ls per minute ar.d mixed for 10 minutes. me pH at this stage was 8.8. 152 mls of aluminium sulphate solution (10.1% A1203) were added at a rate of 10 mls per minute and mixed for O minutes. The pH at this stage was 3.5.
90 mls of caustic sodium aluminate solution (8.2% A1203 and 19.0 Na20) were a~ded at a rate of 9 mls per minute and mixed for 45 minutes. The pH at this stage was 8Ø
~ ' . ' ' ''' ".
105'~059 , The treated titanium dioxide was recovered by filtration.
! T,he filter cake was washed twice with distiiled water, reslurried in distilled water, refilbered and again washed twioe . The filter cake was additioned with 0.4% triethanolamine (on weight of pigment1, dried for 16 hours at 105& then fluid energy milled (twi oe~ in an 8" steam micronlser.
Example 4 A 2156 gram sample of dry milled rutile "sulphate" titanium dioxide base pigment was suspended in 2330 mls of distilled water and 323 mls of sodiu~ silicate solution (10.0% SiO2 and~3.18%
Na20) were added. 5140 mls Ottawa sand were added to the slurry -~ which was then milled~,for 60 minutes in an 8" diameter,pot with ~; 4 x 5" discs (separation 1.5") at 1890 r.p.m. The sand was separated from the pigment by passing the slurry suc oessi~ely through a 100 mesh and then a 325 mesh sieve. Sand-free slurry ocntaining 1 kg of titanium dioxide was diluted to 200 gl 1 with distilled wat~r~
stlrred to ensure efficient mixing,during subse~uent reagent addit1ons and heated to 45C. The pH at this stage was 9.2.
295 mls of a mixed acidic solution of aluminium sulphate, zirconium orthosulphate and titanyl sulphate (7.8% A1203, 1.9% ZrO2 ,~ , and 5.6~ TiO2) were added at a rate of 15 mls pex minute and mixed for 10 minutes. At the end of this stage the pH was 1.1. The slurry pH was adjusted to 8.0 with 2.75M sodium hydroxide over 15 minutes.
150 ~ls of sodium silicate solution ~10.0~ SiO2 and 3.18% Na20) were added at a rate of 10 mls per minute and mixed for 10 minutes. m e . .
.
, -15-, 105;~059 pH at this stdge was 8.3. 152 mls of aluminium sulphate solution tlO.1% A1203) were added at a rate of 10 mls per minut6~ then mi~ed for 5 minutes. The pH at this stage was 3.2. 93 mls of caustic sodium aluninate (8.2% A1203 and 19.0%
N~20) were added at a rate of 6.2 mls per minute then mixed for 45 minutes. me pH dt this stage was 8Ø
me treated t;tanium dioxide pigment was rec~vered by filtration. The filter cake ~as w~shea twice with distilled water, reslurried in distilïed water, refiltered and again -10 washed twioe. me pigment was a~diticned with triethanolamine (0.4% on weight of pigr~nt), dried for 16 hours at 105&, then fluid Pnergy milled ttwice) in an 8" steam microniser.
Exanple 5 - A 2156 gram sample of dly milled rutile TiO2 "sulphate"
based pign~nt ~Jas suspended in 2355 mlsi of <iistilled water. To the suspension were added 323 mls sodiun silicate solutian (1096 SiO2 and 3.18% Na O) and 5140 mls ~f Otta~a sand. The slurry was sand-milled for 60 ~in ~tes in an 8" dic~neter pot with 4 x 5"
di~aneter discs (separation 1.5") at 1890 r.p.m. me sc~d was separated i~rcm the pis[nent by passing the SiUrLy successively through a lCO mesh and then 325 mesh sieve.
The sand-free slurry was diluted to 4.54 litres at 220 g/l TiO2 with distilled water, stirred to ensure efficient mixing during subsequ~ reagent additicns, and heated to 45C. me pH
at this stage was 9.6.
'~', .
. ~ .
~os~os9 298 mls of an acidic solution of aluminium sulphate, ziroonium, orthosulphate and titanyl sulphate ~7.4% A1203, 3 7% Zr2 and 5.5~ TiO2) were added at a rate of 14.9 mls per minute. The slurry was mixed for 10 minutes and the pH
at this stage was 1.3.
The slurry pH was Ghanged, over 10 minutes, to pH 8.0 with - 2.75M sodium hydro~ide and mixed for 5 minutes. 150 mls of sodium - silicate solution (10% SiO2 and 3.18% ,~a20) were added at a rate of 15 mls per minute and mixed for 10 minubes. The.pH at this stage was 8.6.
- -54 mls of aluminium sulphate solution (9.3% A1203) were added - at a rate of 11 mls per minute and the slurry mixed for 10 mlnutes.
T.he pH at the end of this stage was 4.1.
85 mls of caustic sodiu~ al~ nate (8.2~ A1203 and 19.4~ Na20) were-added at a rate of 7 mls per minute and the slurry was mixed.
for a further 40 minutes.
e pH at the end-of thls stage was 8Ø m e treated titanium dioxide pigment was separated from the slurry by filtration, washed twioe w~th distilled water, reslurried in distilled water, again - ~ 20 filtered and washed twice then additioned with triethanolamine : (0.4% on TiO2), dried for 16 hours at 105C. The dried pigment ~tas . fluid energy milled in a laboratory 8" steam microniser.
: The pigment so obtained in Examples 2, 3, 4 and 5 was incorporated in a stoving palnt k~sed on a thermopla~stic acrylic resin sysbem with a pigment:binder ratio of 0.5:1. Coated stainless . ' ' ,' ' . .
lOS;~059 steel panels were prepared, stoved at 120C for 30 minutes and tested in a Marr Weatherometer to determine their durability expressed as Gloss reading (G) a~d Chalk rating (C).
e results are ,pared with thos~ of a cc~ntrc,l being
5. similar paint containing a pigment having acceptable properties and having a co~ating of hydrous titania ~1% by weight as Tio2)~hydrous alumina (2.5% A1203 by weight) and hydrous silica (1.5% SiO2).
~he pigment was also incorporated in a stoving paint based . on a ther~setting acrylic resin with a pigment:binder ratio of lC l.G:lØ Ccated stainless steel panels were prepared, stcved at - . 120C for -,0 minutes and tested in a Marr Weatherometer and ; durability méasured.
~ The results are compared to those of a contrcl being a similar .
. paint cont~inlng a pigment having acceptable prcperties and having : 15 a coating of hvdrous titania (1% by weight T102), hydrous alumina ~2.5~ A1203 by weight) and hydrc~,s silica (1.5% SiO2).
~ . The pigments-were also tested to determine their stoving gloss -~
:. . . .
and colour after baking at different temperat~,res in an alkyd/urea-formaldehyde stoving system and co~pared with those obtained using :~ 2C a titanium dioxide pigment coated with alumina (6% as A1203) and : 1 to 2% TiO2.
. The results are shown in the following Tables.
~, :
-.
- - , -18- .
~05A~059 Durability in thenmo~lastic acrYlic resin AIter TIme ~Ho~rs~
. _ _ Example TestInitial250 500 7501000 1250 : ~ . _ ~ 2 G 92 87 79 70 67 56 . 5 . C 10 10 10 10 9 9 . 3 G 91 81 70 61 59 49 ~ 4 G 90 81 58 52 47 33 ' .' . . ~ . ' C 10 , 10 10 10 . g . 9 - ~.
. . 5 G 92 83 72 67 62 50 ~ lo - c. lo 10 lo lo 9 .9 -~
'~ . Control G 86 84 45 - 34 . 9 2 :
: . C 10 10 10 9 . 6 5 , , . ,., _ _ __ ".
.
.
:` 15 TABLE 5 -,. Durability in therm~settinq acrylic resins ~ _- Aft2r Ti~ (Hours) :
. ~ Exa~ple Tés;t Initial 250 500 750 1290 . .
.,, . __ .
.l . 2 G 86 85 76 56 27 11 ~' 20 . C 10 10 10 9 9 9 I . 3 G 91 86 79 64 32 11 .,'1 . . , C 10 10 10 9 9 9 ;
;:~ 4 G - 80 85 63 39 19 9 C lo 10 10 9 8 8 . . 5 G 86 82 56 42 19 7 . CGntrol G 88 74 46 20 9 4 . . C 10 10 10 6 6 6 ' , _ , _. _ _ . '.''.
.
..
~05;~0S9 ThEIE 6 Stoving gloss Stoving colour Example nornal schedule overbake,s ~ule before W afber W
120 180exposure (1 hour) . 5 2 76.0 18.0 - .
: . 3 78.5 19.5+~ t~ +~ unr~t~bly I
4 74.0 17.0+~ bo +~ unrateably I -77.0 22.5+~ to +~ +~ to +~
.: Control 67.0 . l6.5 std*
.. . .
` * std - standard bo +~ = imprDved r~sults ': ' ' ' , , ' " ' .
' , - -:~ . , ' , .
.'' ' , ~ .
' . ' ' : ' . ' . . , : ' .
- ' ' ' .
: ~,, ' - ' , i,
~he pigment was also incorporated in a stoving paint based . on a ther~setting acrylic resin with a pigment:binder ratio of lC l.G:lØ Ccated stainless steel panels were prepared, stcved at - . 120C for -,0 minutes and tested in a Marr Weatherometer and ; durability méasured.
~ The results are compared to those of a contrcl being a similar .
. paint cont~inlng a pigment having acceptable prcperties and having : 15 a coating of hvdrous titania (1% by weight T102), hydrous alumina ~2.5~ A1203 by weight) and hydrc~,s silica (1.5% SiO2).
~ . The pigments-were also tested to determine their stoving gloss -~
:. . . .
and colour after baking at different temperat~,res in an alkyd/urea-formaldehyde stoving system and co~pared with those obtained using :~ 2C a titanium dioxide pigment coated with alumina (6% as A1203) and : 1 to 2% TiO2.
. The results are shown in the following Tables.
~, :
-.
- - , -18- .
~05A~059 Durability in thenmo~lastic acrYlic resin AIter TIme ~Ho~rs~
. _ _ Example TestInitial250 500 7501000 1250 : ~ . _ ~ 2 G 92 87 79 70 67 56 . 5 . C 10 10 10 10 9 9 . 3 G 91 81 70 61 59 49 ~ 4 G 90 81 58 52 47 33 ' .' . . ~ . ' C 10 , 10 10 10 . g . 9 - ~.
. . 5 G 92 83 72 67 62 50 ~ lo - c. lo 10 lo lo 9 .9 -~
'~ . Control G 86 84 45 - 34 . 9 2 :
: . C 10 10 10 9 . 6 5 , , . ,., _ _ __ ".
.
.
:` 15 TABLE 5 -,. Durability in therm~settinq acrylic resins ~ _- Aft2r Ti~ (Hours) :
. ~ Exa~ple Tés;t Initial 250 500 750 1290 . .
.,, . __ .
.l . 2 G 86 85 76 56 27 11 ~' 20 . C 10 10 10 9 9 9 I . 3 G 91 86 79 64 32 11 .,'1 . . , C 10 10 10 9 9 9 ;
;:~ 4 G - 80 85 63 39 19 9 C lo 10 10 9 8 8 . . 5 G 86 82 56 42 19 7 . CGntrol G 88 74 46 20 9 4 . . C 10 10 10 6 6 6 ' , _ , _. _ _ . '.''.
.
..
~05;~0S9 ThEIE 6 Stoving gloss Stoving colour Example nornal schedule overbake,s ~ule before W afber W
120 180exposure (1 hour) . 5 2 76.0 18.0 - .
: . 3 78.5 19.5+~ t~ +~ unr~t~bly I
4 74.0 17.0+~ bo +~ unrateably I -77.0 22.5+~ to +~ +~ to +~
.: Control 67.0 . l6.5 std*
.. . .
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' , - -:~ . , ' , .
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Claims (17)
1. A process for the treatment of titanium dioxide pigment comprising :
a. forming an aqueous dispersion of pigmentary titanium dioxide containing a first water-soluble compound of silicon in an amount of from 1 to 2% by weight expressed as SiO2, b. adding to the dispersion a first acidic water-soluble compound of aluminium in an amount of from 1.5 to 2.5% by weight expressed as Al2O3, an acidic water-soluble compound of zirconium in an amount of from 0.5 to 1.5% by weight expressed as ZrO2, and an acidic water-soluble compound of titanium in an amount of from 1.0 to 2.0% by weight expressed as TiO2, c. changing the pH of the dispersion to a value in the range 7.5 to 8.5, and then d. adding to the dispersion a second water-soluble compound of silicon in an amount of from 1 to 2% by weight expressed as SiO2, then a second acidic water-soluble compound of aluminum in an amount of from 1 to 2% by weight expressed as Al2O3, and then an alkaline water-soluble compound of aluminium in an amount of from 0 to 1.5% by weight expressed as Al2O3, all the percentages by weight being based on the weight of TiO2 in the pigment and recovering the so treated pigment.
a. forming an aqueous dispersion of pigmentary titanium dioxide containing a first water-soluble compound of silicon in an amount of from 1 to 2% by weight expressed as SiO2, b. adding to the dispersion a first acidic water-soluble compound of aluminium in an amount of from 1.5 to 2.5% by weight expressed as Al2O3, an acidic water-soluble compound of zirconium in an amount of from 0.5 to 1.5% by weight expressed as ZrO2, and an acidic water-soluble compound of titanium in an amount of from 1.0 to 2.0% by weight expressed as TiO2, c. changing the pH of the dispersion to a value in the range 7.5 to 8.5, and then d. adding to the dispersion a second water-soluble compound of silicon in an amount of from 1 to 2% by weight expressed as SiO2, then a second acidic water-soluble compound of aluminum in an amount of from 1 to 2% by weight expressed as Al2O3, and then an alkaline water-soluble compound of aluminium in an amount of from 0 to 1.5% by weight expressed as Al2O3, all the percentages by weight being based on the weight of TiO2 in the pigment and recovering the so treated pigment.
2. A process according to claim 1 in which the aqueous dispersion of pigmentary titanium dioxide is formed from calcined titanium dixoide.
3. A process according to claim 1 in which the titanium dioxide contains at least 95% of its TiO2 content in the rutile form.
4. A process according to claim 1 in which the said titanium dioxide pigment contains from 0.1 to 0.5% by weight Al2O3 based on the weight or TiO2.
5. A process according to claim 1 in which the aqueous dispersion of pigmentary titanium dioxide containing the water-soluble compound of silicon is wet milled.
6. A process according to claim 1 in which the amount of the first acidic water-soluble compound of aluminium is from 1.8 to 2.2% by weight expressed as Al2O3.
7. A process according to claim 1 in which the amount of the acidic water-soluble compound of zirconium is from 0.8 to 1.2% by weight expressed as ZrO2.
8. A process according to claim 1 in which the amount of the acidic water-soluble compound of titanium is from 1.2 to 1.6 by weight expressed as TiO2.
9. A process according to claim 1 in which the acidic water-soluble compounds of aluminium, titanium and zirconium are added to the aqueous dispersion in the farm of a mixed aqueous solution.
10. A process according to claim 9 in which the mixed aqueous solution contains aluminium sulphate, titanyl sulphate and zirconium sulphate and has a pH of from 0.7 to 1.2.
11. A process according to claim 1 in which the pH of the aqueous dispersion is changed to a value within the range 7.5 to 8.5 by the addition of an alkali.
12. A process according to claim 1 in which the amount of the second water-soluble compound of silicon is from 1.4 to 1.6% by weight expressed as SiO2.
13. A process according to claim 1 in which the amount of the second water-soluble compound of aluminium is from 1.2 to 1.7% by weight expressed as Al2O3.
14. A process according to claim 1 in which the alkaline water-soluble compound of aluminium is added to the aqueous dispersion in an amount of from 0.7 to 1.2% by weight expressed as Al2O3.
15. A process according to claim 1 in which the treated titanium dioxide recovered is milled in a fluid energy mill.
16. A process according to claim 15 in which the pigment is treated with an amine, alkanolamine or a polyol during milling.
17. A process as claimed in claim 1 wherein the amount of said alkaline water-soluble compound of aluminium added is 0 and the pH of said dispersion is maintained in the range 4.0-4.5 by the simultaneous but separate addition of alkali during the addition of said second acidic water-soluble compound of aluminium, the pH of said dispersion then being raised to pH 8.0 before recovery of the treated pigment.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB30034/75A GB1479988A (en) | 1975-07-17 | 1975-07-17 | Treatment of pigment |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1052059A true CA1052059A (en) | 1979-04-10 |
Family
ID=10301207
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA255,700A Expired CA1052059A (en) | 1975-07-17 | 1976-06-25 | Treatment of pigment |
Country Status (7)
| Country | Link |
|---|---|
| AU (1) | AU499445B2 (en) |
| CA (1) | CA1052059A (en) |
| DE (1) | DE2629954A1 (en) |
| ES (1) | ES449626A1 (en) |
| FR (1) | FR2318210A1 (en) |
| GB (1) | GB1479988A (en) |
| ZA (1) | ZA763340B (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA1151499A (en) * | 1979-03-06 | 1983-08-09 | Tioxide Group Limited | Aqueous dispersions |
| GB8712752D0 (en) * | 1987-05-30 | 1987-07-01 | Tioxide Group Plc | Particulate material |
| GB8829402D0 (en) * | 1988-12-16 | 1989-02-01 | Tioxide Group Plc | Dispersion |
| GB9121153D0 (en) * | 1991-10-04 | 1991-11-13 | Tioxide Chemicals Ltd | Method of preparing sunscreens |
| GB9121143D0 (en) * | 1991-10-04 | 1991-11-13 | Tioxide Chemicals Limited | Dispersions |
| DE102006059849A1 (en) * | 2006-12-15 | 2008-06-19 | Kronos International, Inc. | Process for the surface treatment of solid particles, in particular titanium dioxide pigment particles |
| EP2000502A1 (en) * | 2007-05-30 | 2008-12-10 | Sachtleben Chemie GmbH | Composite particles |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL300720A (en) * | 1962-11-20 | |||
| US3410708A (en) * | 1964-08-05 | 1968-11-12 | Du Pont | Porous silica coated titanium dioxide pigment |
| GB1073338A (en) * | 1965-07-21 | 1967-06-21 | British Titan Products | Mixed coating process |
| DE2223524A1 (en) * | 1972-05-13 | 1973-11-22 | Kronos Titan Gmbh | PROCESS FOR PRODUCING A TITANIUM DIOXIDE PIGMENT WITH INCREASED WEATHER RESISTANCE |
-
1975
- 1975-07-17 GB GB30034/75A patent/GB1479988A/en not_active Expired
-
1976
- 1976-06-04 ZA ZA763340A patent/ZA763340B/en unknown
- 1976-06-04 AU AU14637/76A patent/AU499445B2/en not_active Expired
- 1976-06-25 CA CA255,700A patent/CA1052059A/en not_active Expired
- 1976-07-02 DE DE19762629954 patent/DE2629954A1/en active Granted
- 1976-07-07 ES ES449626A patent/ES449626A1/en not_active Expired
- 1976-07-13 FR FR7621489A patent/FR2318210A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| FR2318210B1 (en) | 1980-06-06 |
| ZA763340B (en) | 1977-05-25 |
| FR2318210A1 (en) | 1977-02-11 |
| ES449626A1 (en) | 1977-07-01 |
| DE2629954A1 (en) | 1977-02-03 |
| AU499445B2 (en) | 1979-04-12 |
| GB1479988A (en) | 1977-07-13 |
| AU1463776A (en) | 1977-12-08 |
| DE2629954C2 (en) | 1989-01-19 |
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