Note: Descriptions are shown in the official language in which they were submitted.
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
,
.
:-. ' .
-7-
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
:; ' ' '
-8-
- .
- 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--
` 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 : ' `
. , - - ' .
.
. ~ - .
. ~ -
:. '
:
--11--
. . .
1()5;~059 `
,, .
TABLE 2
Durability in thermDset~ing acrylic resLns
After Time ~Hours
Example 1 Test ¦ Initia~ ~ 500
1 G lCO 95 85 73 60 44
C 10 9 9 9 9 9
Control G 95 95 77 50 32 16
C 10 9 9 9 8 7
.` '
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
-12-
. .
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.
,
-13-
'
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
~ ' . ' ' ''' ".
-14- -
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.
'~', .
--16--
. ~ .
~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
. ' ' ,' ' . .
-17-
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
TABLE 4
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
C 10 10 10 10 9 9
~ 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
C 10 10 10 9 8 7
. CGntrol G 88 74 46 20 9 4
. . C 10 10 10 6 6 6
' , _ , _. _ _ . '.''.
.
-19- -
..
~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
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