TITANIUM DIOXIDE PIGMENT SLURRIES TO IMPART HIGH GLOSS TO WATER-BASED PAINT SYSTEMS

BOUES DE DIOXYDEDE DE TITANE PIGMENTAIRE DONNANT BEAUCOUP DE BRILLANCE AUX PEINTURES A L'EAU

English Abstract

ABSTRACT
An aqueous slurry of from 60 to 80 percent titanium
dioxide is prepared from titanium dioxide of uniform and small
particle size. At least 80 percent by weight of pigment is
incorporated into an aqueous system containing suitable dis-
persant which slurry is then reduced to the final slurry con-
centration with water.

Claims

WHAT IS CLAIMED IS:
1. An aqueous slurry of titanium dioxide pigment
to provide a high-gloss finish to paint films derived from
acrylic water-based systems, said slurry containing from
60 to 80 percent titanium dioxide, from 0.2 to 1 percent
of a compound selected from the formula
<IMG>
where M is alkali metal,
R1 to R4 is H, -CH3 or C2H5,
X is -CN or -COOR5 where R5 is hydrogen or lower
alkyl of 1-4 carbon atoms,
Y is -COOH or -COONa, and
a and b are 10 to 100,
from 0.1 to 0.6 percent of 2-amino-2-methyl-1-propanol and
the remainder water.
2. An aqueous slurry of Claim 1 which contains
from 70 to 80 percent by weight of titanium dioxide.
3. An aqueous slurry of Claim 1 which contains
from 75 to 79 percent by weight titanium dioxide.
4. A process for producing high solids content
titanium dioxide aqueous slurry which comprises preparing
solution of 0.2 to 1 percent of a compound of the
formula
<IMG>
-12-

where M is sodium,
R1 to R4 is H,
X is -COOH,
Y is -COOH or -COONa, and
a and b are 10 to 100,
from 0.1 to 0.6 percent 2-amino-2-methyl-1-propanol in from
10 to 20 percent of water, the percentages being based upon
the weight of the titanium dioxide present, adding from 80
to 90 percent by weight of dry titanium dioxide, grinding
with a disc mill until the titanium dioxide is uniformly
dispersed and then adding sufficient water to reduce the
titanium dioxide content to from 60 to 80 percent by weight
of the finished slurry.
5. A process for producing high solids content
titanium dioxide aqueous slurry which comprises
(a) drying and grinding titanium dioxide pigment
prepared by the oxidation of titanium tetrachloride in a
confined vortex fluid energy mill;
(b) preparing a solution of 0.2 to 1 percent, based
on the weight of titanium dioxide, of a compound of the
formula
<IMG>
where M is alkali metal,
R1 to R4 is H, -CH3 or C2H5,
X is -CN or -COOR5 where R5 is H or alkyl of 1-4
carbon atoms,
Y is -COOH or -COONa, and
a and b are 10 to 100
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and 0.1 to 0.6 percent, based on the weight of titanium
dioxide, 2-amino-2-methyl-1-propanol in from 10 to 20 per-
cent by weight of the slurry of water;
(c) adding from 80 to 90 percent by weight of the
titanium dioxide of step (a) to form a slurry;
(d) grinding the slurry with a disc mill until the
titanium dioxide is uniformly dispersed and is of an average
particle size of less than about 0.6 micron with not more
than five mass percent of the particles having an average
particle size of greater than one micron;
(e) adding sufficient water to reduce the titanium
dioxide content to from 75 to 79 percent by weight of the
finished slurry; and
(f) mixing the slurry until smooth and uniform.
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Description

1087 7 75
BACRGROUND OF ~HE INVENT~ON
~ he present in~ention relates to the preparation
and composition of titanium dioxide in an aqueous slurry
suitable for incorporation in water-based acrylic paint
æystems to impart high-glo~s characteristics to the dried
paint film.
: In recent years substantial research has been
undertaken to develop titanium dioxide slurries that were
suitable for use in paper and water-based paint manufacture.
The economics and ease of use of such slurries has been a
cubstantial incentive for the development of titanium
dioxide slurries.
Hall and Looby dlsclose ln U. S. Patent 3J702,773
that a stabillzed tltanlum dloxide ~lurry o~ rrom 60 to 82
percent by welght Or tltanlum dlo~ide ror use ln paper manu-
racturlng could be prepared. Roberts and Rowland dlsclose
ln U. S. Patent 3,758,322 that a process ror produclng
slurries Or ~rom 60 to 80 percent t~tanlum dlo~lde content
can be prepared rrom a plgment slurry contalnlng 20 percent
sollds, Daubenspeck and Jett dlsclose ln U. S. Patent
3,847,640 that a pigment slurry containing 60 to 65 percent
titan~um dloxlde ls adapted to be used in latex ~la~ palnt
formulations.
This invention provides another step rorward ln
the development of titanlum dloxlde slurries. This lnventlon
provldes a slurry o~ very hlgh sollds content that can be
used to prepare high gloss water-based acrylic paint
formulations.
SUMMARY OF THE INVENTION
~his invention provides an aqueous slurry of
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1087'775
titanium dioxide which when dried from a water-based acrylic
coating composition forms a high-gloss film, said aqueous
ælurry contains from 60 to 80 percent titanium dioxide,
from 0.2 to 1 percent based upon the weight of titanium
dioxide of a compound of the formula
-Rl R,2 l IR3 R4
I. H- L X I ~ c c 1~ S03M
where M is alkali metal,
~1 to R4 is hydrogen, methyl or ethyl,
X is cyano or -COOR5,
where R5 is H, or lower alkyl of 1 to 4 carbon
atoms,
Y is -COOH or -COONa,
a and b are 10 to 100, and
rrom 0.1 to 0.6 percent based on the weight o~ titanium
dioxlde Or 2-amino-2-methyl-1-propanol.
Thls lnventlon also relates to a process for pro-
duclng a hlgh sollds content tltanlum dioxlde aqueous slurry
~hlch comprlses preparlng a solutlon of 0.2 to 1 percent o~
a compound of formula I and 0.1 to 0.6 percent of 2-amino-
2-methyl-1-propanol, based on the weight of the titanium
dioxide in about 10 to 25 percent of water, adding 75 to
90 percent by weight of titanium dioxide, grinding with a
disc mill until uniform and adding sufficient water to re-
' duce the titanium dioxide content to from 60 to ~0 percent
by weight of the finished slurry.
DESCRIPTION OF THE INVENTION
I This invention relates to a hish-solids, high-gloss
- 30 aqueous composition of titanium dioxide which is commonly
--3--

lo~ms
referred to in the art as a slurry. The slurrie~ of this
invention are high-æolids slurries, i.e., from 60 to 80,
and preferably ~rom 70 to 80, percent by weight titanium
dioxide. Most preferably, the solids content of the slurry
will be from about 75 to 79 percent titanium dioxide. me
compositions of this inventlon are also referred to as high-
glo~s slurries. The term "h~gloss 81urry" means that
when the ~lurry is incorporated into an acryllc palnt formu-
lation and dried into a thin film the film is of high glo88.
The high-glosæ slurries of this invention can be prepared
simply from a dry titanium dioxide which has not been sub-
~ected to special surface treatments prior to incorporation
into water. Outstanding gloss levels in acrylic water-based
paint systems have been achieved when a chloride process
titanium dloxide i8 æimultaneo w ly dr~ed and groud u~ing
a fluid energy mill o~ the conf~ned vortex tM e such as is
tau~ht in U, S. Patent 3,840,188,
The titanium dioxide emp~oyed in the preparation
of the ~lurry compositions of this invention will preferably
be of uniformly small particle size with at leaæt 95 mass
percent of the average particle size being one mlcron or
les~ and with an average particle æize of lesæ than about
o.6 microns.
The titanium dioxide will also be one which has no
hydrous oxide after-treatment as the presence of hydrous
oxide reduces the gloss of the fini~hed paint film. It is
under~tood, howe~er, that the presence of rutili~ing agents
such as co-oxidized aluminum and the like which are normally
pre~ent in titanium dioxide produced by oxidation of titanium

~o~ms
tetrachloride will not ob~iate the advantages of the slurries
of this in~ention.
To achieve the outstanding properties of glo88
the slurry i8 prepared by adding dry titanium dioxide to
about 13 to 20 percent by weight of water, preferably 13 to
15 percent by weight of water, ~hich contain~ about 0.2 to
1 percent, based on the weight of titanium dioxide, of a com-
pound of formula I and from 0.1 to o.6 percent, based on the
weight of tltanium dioxide, of 2-amino-2-met ffl l-l-propanol.
m e high-solids slurry is then ground until uni~orm using a
disc mill such as a Hockmeyer* disperser manufactured by
H, H. Hockmeyer, Inc. The grinding i8 continued until the
slurry beco~es uniform and then sufficient water i8 added to
reduce the solids content o~ the slurry to from about 60 to
80 percent by weight.
When preparing the slurries of this invention the
titanium dioxide content of the initial slurry shouad be at
least 80 percent by weight so that the disc mill can impart
sufficient shear into the sy~tem to assure reduction in
agglomerate size o~ the titanium dioxide within the limits
of this invention. Ideally the particle size will be aæ
i fine as possible with the average particle size of less than
; about o.6 micronæ with not more than 5 mass per cent of the
titanium d~oxide particles or agglomerates, as the case ma~
be, with a particle size greater than one micron. Therefore,
depending on the pigment base being employed the gFinding
time and pigment concentration will be adJu~ted to achieve
the desired particle ~ize uniPormity and distrlbution. It
has also been disco~ered that addition of about ~ive percent
water to the system after the grinding step resultæ ~n
* denotes trade mark
,~

10~7775
improved rheological propertiec of the slurry and handling
and use of the finished slurry is markedly enhanced.
It ha~ al~o been dlscovered that the use Or a sult-
able dlspersant system ~ nece~ary to achle~e a tltanlum
dloxlde slurry whlch lmparts outstandlng glos~ to a palnt
~llm derived rrom a water-~a~ed system. The dlsper~ant
~ystem comprl~ed Or 0.2 to 1 percent o~ a compound Or ~ormula
I and rrom 0.1 to 0.6 percent Or 2-amlno-2-methyl-1-propanol,
based on the welght o~ titanium dloxlde present, will when
comblned wlth the other processing conditlons descrlbed
herein produce a tltanlum d~o~ide slurry wlth an unexpectedly
high level Or gloss ln a drled palnt f~lm.
The rollowlng examples are lllustratlve Or the
inventlon. All parts and percentages are by welght unless
otherwlse noted.
Example 1
Titanium dloxlde produced by the oxidation o~
tltanlum tetrachlorlde and about 1.0 per cent aluminum oxide
in aqueous slurry of about 55-75 per cent by weight solids
ls ~ed to a ~luid energy mill as described ln the example Or
U. S. Patent 3,840,188 and dried and ~round using a steam to
pigment ratlo Or rrom 2.5 to 6 as described therein to ~ro-
duce dry tltanlum dioxide o~ uniform and small particle size.
~ ple 2
To 5,300 ml of water in a five-gallon container
is added 150 ml of a compound of formula I in which M is
Na, Rl to R4 are hydrogen and X and Y are carboxyl groups,
and 60 ml of 2-amino-2-methyl propanol. To the above solu-
tion is added 30,000 g of titanium dioxide pigment obtained
as described in Example 1. Then a Hockmeyer disperser
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` ~W77~5
fitted with a four-inch blade rotating at 4,000 rpm i8
employed to grind the pigment. After grinding for 20 min-
utes, 3,000 ml of water is added to reduce the solid~
concentration in the slurry to about 76.7 percent by weight.
m e particle size of the solids i8 determined u~ing a
Micrometrics* 5000 Analyzer which shows a mass percent of
particles finer than:
Mass % Size (~)**
84 o.6
0.47
16 0.325
3.5 >1
33 ~0.4
~* 8~ indicateæ that 84~ of the particles
are o.65~ or smaller.
The slurry prepared in Example 2 is compared with
a commerc~ally available high-gloss titanium dioxide for
gloss and hiding power as described below.
Air ~ry Emulsion Gloss An acrylic emulsion paint
20 i8 prepared containing a 22.8 pigment volume concentration.
me acrylic emulsion paint is drswn down to a film thickness
of .008 inch and is allowed to dry for a mini~um of three
days and the glo88 (60) of the paint f~lm is then determined.
Oven Dry Emulsion Gloæs An acrylic emulsion paint
is prepared containing a 25 pigment volume concentration.
The acrylic emulsion paint is drawn down to a film thickness
of .004 inch and i8 immediately placed ~nto a 110C. dra~t
~ree oven for thirty minutes and the gloss (60) of the
paint ~ilm is then determined.
Hiding Power The above acrylic emulsion paint prep-
arations are drawn down to a film thickness of .0025 inch on
* denotes trade mark

~o~ms
Morest 09 chart and drled ror 24 hours. Hldlng power o~ the
palnt prepared rrom the slurrles Or this lnventlon ls com-
pared ~lth that o~ the control. The relatl~e hldlng power
(H.P.) o~ the slurrles Or this lnventlon are calculated as
~ollows:
H p ~ SX o~ Test Sam~le X 100
SX o~ Control Sample
SX - Scatterlng power determined accordlng to the
method Or D. B. Judd, "Optlcal Speclrlcatlons Or Llght
Scatterlng Materials", Journal Or Research o~ the National
Bureau Or Standards, Vol. 19, 1937, p. 287.
Emulslon Gloss
Alr Dr~ Oven Dry H.P.
Slurry Or Example 2 62 75 102
Control 49 56 100
Example 3
2-Amino-2-methyl propanol l45 ml) and a com-
pound of formula I in which M is Na, Rl to R4 are hydrogen
and X and Y are carboxyl groups (114 ml) are added to
7,200 ml of water in a five-gallon container. To this mix-
ture is added 22,700 g of the titanium dioxide pigment pre-
pared in accordance with Example 1. The resultant slurry
is then ground with a Hockmeyer disperser fitted with a
four-inch ~lade for 20 minutes at 1,500 rpm. After this
grinding the solids content of the slurry is reduced with
2,500 ml of water to give a final slurry with a solids con-
centration of 68.2.
The emulslon gloss and hiding power o~ the slurry
Or Example 3 ls compared with that o~ a commerclal gloss
pigment wlth the followlng resultæ:

~08~7s
Emulsion Gloss
Air Dry H.P.
Slurry of Example 3 64 99
Control 56 100
Example 4
Sixty milliliters of 2-amino-2-methyl propanol
- and 240 ml of a compound of formula I in which M i8 Na,
Rl to R4 are hydrogen and X and Y are carboxyl groups are
added to 5,300 ml of water in a five-gallon container. To
the above mixture is added 30,000 g of a titanium dioxide
pigment obtalned as described ln Example 1. Then a
Hochmeyer disperser ~ltted with a rour-inch blade rotating
at 2,000 rpm ls employed to grlnd the pigment. Arter grlnd-
ing for 20 minutes 3,500 ml Or water is added to reduce the
solids concentration ln the slurry to about 77 percent by
weight.
The particle size Or the solids present in the
slurry is determined using a Micrometrics 5000 Analyzer which
shows a mass percent Or particles riner than:
Mass S Size (~)
84 0.51
.375
16 0.245
2.0 ~1
58 <0.4
The gloss and hlding power Or the slurry o~
Example 4 ls compared wlth that of a commerical ~loss pig-
ment as described above with the rollowing results:
Emulsion Gloss
Air Dry H.P.
Slurry Or Example 4 64 99
Control 49 100
_g_

~os777s
The rollowing examples are preQented to demon-
strate that the high-sollds grlnd rollowed by dllutlon to
a sollds concentratlon wlthln the range o~ 60 to 80 percent
solids wlll produce a slurry whlch provldes lmproved gloss
when compared to the same plgment which ls drled conven-
tionally and lncorporated dlrectly lnto the palnt system.
; Example 5
Fifty-four milliliters of 2-amino-2-methyl pro-
panol and 185 ml of a compound of formula I in which M is
Na, Rl to R4 are hydrogen and X and Y are carboxyl groups
a~e added to 2,930 ml of water. To the above mixture is
added 18,000 g titanium dioxide pigment upon which has been
precipitated 0.2 percent alumina. Then a Hochmeyer dis-
perser fitted with a four-inch blade rotating at 2,000 rpm
iæ employed to grind the pigment. After grinding for 20
minutes 1,800 ml of water is added to reduce the solids
content of the slurry to 79 percent by weight.
The partlcle slze Or the sollds is determined
using a Micrometrics 5000 Analyzer which shows a mass percent
o~ particles ~iner than:
Mass S Slze (~)
84 0.54
0.35
16 0.245
4,0 >1
<0.4
The air dried gloss and hidin~ power of the slurrv
~f Example 5 is compared with that of a commercial ~loss
pigment as described above with the following results:
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775
~ulgion alo8~
_ Alr Dry ~.P.
Slurr~ Or ExaD~le 5 67~71~ 101
Control 60/49~ 100
repeat Or glo~ test
~xa~ple 6
Fl~ty-~our millillters Or 2-amlno-2-methrl propanol
and 145 ml o~ a co~pound o~ ~or~ula I in ~hich M i~ Na, Rl to
R4 are hJdrogon and X and ~ are earbo~l groups aro added to
3,200 ~1 Or ~ater. To the abo~e ~ixturo i~ addea 18,000 g Or
t~tanium dtoxlde ~hich ha~ not been surrace troated. Then a -
Hoekme~er dlsparser ritted wlth a four-in¢h blade rot~tlng at
2,0Q0 rpm i~ emplored to ~rind the pigmRnt. A~ter grinding
~or 20 minutes 1,800 ml o~ water 18 added to reduce the
solid~ content to 78.5 percent b~ ~eight.
particle ~lze of the solld~ in the ~lurry
~eter~ined asln~ a Mlcro~etric~ 5000 Analyzer which ~ho~ a
ma~ pereent o~ partleles riner than:
~a~ % Size (p)
84 .43
0.31
16 0.225
2.0 >1
80.0 ~o.4
The glo88~ e~ulslon glosJ and hidl4g po~er o~ tho
~lurry o~ k~mple 6 1~ comparod ~ith a co~merc~al glo~- pig-
~ent as described aboY~ ~ith the rollo~ing result~:
~ulsion Glo~s
Alr J~ O~n nr~ ~P.
Slurr~ o~ Exa~pl- 6 66~73~ 73 97
Control 60/64~ 56 lO0
~ rey-at o~ glo~ tost