1. Use, in a paint formulation containing titanium dioxide particles, as an agent for improving the opacity of the film that is dry or in the process of drying, of a water-soluble copolymer consisting of: a) 4 to 25% by weight of acrylic acid and/or methacrylic acid monomers and/or any of their salts, b) 75 to 96% by weight of at least one monomer with the formula (I): R – X – R' (I) according to which: R represents a polymerizable unsaturated function, notably acrylate, methacrylate, methacrylurethane, vinyl or allyl, R' represents hydrogen or an alkyl group having from 1 to 4 carbon atoms, X represents a structure with n unit(s) of ethylene oxide EO and m unit(s) of propylene oxide PO, arranged randomly, m and n are 2 integers between 0 and 100, at least one of which is non-zero, and are such that m + n is greater than 17, said copolymer having a molecular mass between 200,000 and 50,000,000 g/mol.

2. Use according to claim 1, according to which said water-soluble copolymer has a molecular mass between 250,000 and 15,000,000 g/mol. 22

3. Use according to claim 1 or 2, according to which said copolymer consists in: a) 5 to 20% by weight of acrylic acid and/or methacrylic acid monomers and/or any of their salts, and b) 80 to 95% by weight of at least one monomer with the formula (I).

4. Use according to any of the preceding claims according to which said water-soluble copolymer consists in: A1) 4 to 15% by weight of acrylic acid monomers or any of its salts, A2) 1 to 5% by weight of methacrylic acid monomers or any of its salts, and b) 80 to 95% by weight of at least one monomer with the formula (I).

5. Use according to any of the preceding claims according to which said water-soluble copolymer is such that n and m are two non-zero integers and are such that n+m>50.

6. Water-based paint formulation including: - water, - titanium dioxide particles and - a water-soluble copolymer consisting essentially in: a) 4 to 25% by weight of acrylic acid and/or methacrylic acid monomers and/or any of their salts, b) 75 to 96% by weight of at least one monomer with the formula (I): R – X – R' (I) 23 according to which: R represents a polymerizable unsaturated function, notably acrylate, methacrylate, methacrylurethane, vinyl or allyl, R' represents hydrogen or an alkyl group having from 1 to 4 carbon atoms, X represents a structure with n unit(s) of ethylene oxide EO and m unit(s) of propylene oxide PO, arranged randomly, m and n are 2 integers between 0 and 100, at least one of which is non-zero, and are such that m + n is greater than 17, the said copolymer having a molecular mass between 200,000 and 50,000,000 g/mol.

7. Water-based paint formulation according to claim 6 according to which said formulation includes from 0.05 to 5% by weight of said copolymer.

8. Water-based paint formulation according to claim 6 or 7 according to which the said formulation includes from 4 to 40% by weight of titanium dioxide particles.

9. Formulation according to any of claims 6 to 8 according to which said formulation includes from 15 to 25% by weight of titanium dioxide particles.

10. Formulation according to any of claims 6 to 9 according to which said formulation includes at least one other pigment mineral filler selected from the group consisting of calcium carbonate, kaolin, and silicate.

FORM 2
THE PATENT ACT 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See Section 10, and rule 13)
1. TITLE OF INVENTION
USE OF NEW ADDITIVES IN A PAINT FORMULATION COMPRISING TITANIUM
DIOXIDE PARTICLES AS AGENTS IMPROVING THE OPACITY OF THE DRY OR
DRYING FILM
2. APPLICANT(S)
a) Name : COATEX
b) Nationality : FRENCH Company
c) Address : 35, RUE AMPÈRE,
Z.I. LYON-NORD,
F-69730 GENAY,
FRANCE
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention
and the manner in which it is to be performed : -
2
The present invention relates to the use of new additives as agents for improving the
opacity of the film that is dry or in the process of drying of a paint formulation
including titanium dioxide particles which enables a reduction in the amount of this
pigment in paints.
Mineral pigments such as TiO2 are products whose availability is becoming
increasingly limited. This leads to an increase in their price. It is therefore sought to
reduce their use in products containing them, including paints, without reducing the
optical qualities of the paints.
Several strategies are designed to promote the beneficial aspects of titanium dioxide
while minimizing the quantities needed. However, despite the use of dispersants in the
formulations, the phenomenon of particle flocculation, particularly during drying of
the paint film, reduces the opacifying effectiveness of the TiO2. With this in mind,
several techniques are available in the prior art for improving the spacing and
distribution of TiO2 pigment particles in paint.
In particular, some of these strategies lie in the substitution of part of the TiO2
particles by another pigment, particularly in paints referred to as high pigment volume
concentration paints. This additional pigment is then presented as a spacer/extender
particle, that is, as a particle that mechanically spaces the TiO2 pigment particles.
Such approaches are nevertheless unsatisfactory in that they lead, during the paint
drying phase, to an agglomeration of the titanium dioxide particles, thus not having
the anticipated effect on the optical qualities expected.
To resolve this technical problem, document WO 2006/023065 proposes the use of a
special pigment of the metal oxide type such as zinc oxide, which is presented as
having an affinity for the surface of TiO2 particles. Also, there is mention in this
document of the use of an oligomeric/polymeric dispersant intended to prevent
flocculation in the dry film.
3
As for application US 2004/0202601, it describes a method for spacing TiO2 particles
by using spacer particles consisting of an additional pigment, notably of the calcium
carbonate, silica, alumina type, and of a compound of the acrylic acid
homopolymer/copolymer type. This polymeric compound is presented as having a
role in the viscosity and dispersibility of the additional pigment in the composition.
These solutions are unsatisfactory in that they consist of a replacement of part of the
titanium dioxide by another pigment, which often leads to making a compromise in
the expected qualities of the finished products.
As regards documents EP 1 270 687 and EP 1 070 739, they describe the use of
polymer particles adsorbed on the surface of pigment particles. The polymers referred
to in these documents present a non-water-soluble structure, for example, of the
styrene type, on which are grafted the pendant acid functional groups of the
dihydrogen phosphate, phosphonate, sulfonic acid or multiacid type.
Thus, this strategy consists of encapsulating the particles of TiO2 in a special latex.
The technology resides in the mixture of a suspension of TiO2 and latex in such a way
as to coat the TiO2 particles with this latex. The resulting particles are then used as a
source of titanium dioxide in paint formulations. According to this approach, the
choice of latex depends on the nature of the TiO2 as well as the nature of the binder
used in the paint. Thus, the technology described must be adapted to each paint
formulation, which constitutes a major limitation in the use of such a technology.
An object of the present invention is to reduce the amount of TiO2 particles used in
paint formulations without reducing the expected optical qualities of the paint in the
process.
Another object of the present invention is to reduce the amount of TiO2 particles
without necessarily having to compensate for this decrease by the addition of another
pigment to the composition.
4
Another object of the present invention is to allow a reduction in the amount of TiO2
in paints without a profound change in paint formulations, for example, without
modifying the rheological properties.
Another object of the present invention is to allow a reduction in the amount of TiO2
in paint formulations by an approach that is easily implemented by the formulator.
Another object of the present invention is to maintain separation and prevent
flocculation between TiO2 particles during drying of the paint film.
Another object of the present invention is to reduce the amount of TiO2 in paints by
using a low-dose compound while maintaining the expected optical properties.
The inventors realized surprisingly that by using a family of water-soluble polymers,
all of these objectives were realized. The use of such polymers in fact allows an
increase in the effectiveness of titanium dioxide and thus reduces its use without
decreasing the performances of the paint and without substantially modifying the
rheological properties of the formulations. In particular, the interest in these molecules
is to produce this effect based on doses in the order of a few percent.
The present invention thus concerns the use in a paint formulation including titanium
dioxide particles as an agent for improving the opacity of the film that is dry or in the
process of drying, of a water-soluble comb type copolymer with a (meth)acrylic acid
skeleton and polyalkylene glycol branches.
By "titanium dioxide" or "titanium dioxide particles" is meant particles of the rutile or
anatase type, such as obtained by conventional industrial processes starting from ore,
for example, by a sulphate process or a chloride process. According to the invention,
the TiO2 particles are in the form of suspensions, dispersions in a liquid, or in the
powder form. When the TiO2 is in the powder form, the particles have a particle size
distribution characterized by a mean particle size between 100 and 500 nm, for
5
example, between 200 and 400 nm, for example, a mean size of 250 nm. Such
particles are available commercially.
By "polyalkylene glycol" is meant a polymer of an alkylene glycol derived from an
olefin oxide. The polyalkylene glycol according to the present invention is, for
example, polyethylene glycol, polypropylene glycol, polybutylene glycol or a
polyalkylene glycol containing a proportion of the oxyethylene group and/or a
proportion of the oxypropylene group and/or a proportion of the oxybutylene group.
For example, the polyalkylene glycol according to the present invention may include a
dominant proportion of the oxyethylene group in association with a secondary
proportion of the oxypropylene group.
Some specific examples of alkylene glycol polymers include: polyalkylene glycols
having an average molecular weight of 1,000, 4,000, 6,000, 10,000 and 20,000 g/mol
(in the case of the polyethylene glycols called PEG-1,000, PEG-4,000, PEG-6,000,
PEG 10,000, PEG 20,000), the polyethylene polypropylene glycols having an
ethylene oxide percentage between 20 and 80% by weight, and a propylene oxide
percentage between 20 and 80% by weight.
Specifically, according to one aspect of the present invention, the copolymer includes:
a) 4 to 25% by weight of acrylic acid and/or methacrylic acid monomers and/or any
of their salts,
b) 75 to 96% by weight of at least one monomer with the formula (I):
R – X – R'
(I)
according to which:
R represents a polymerizable unsaturated function, notably acrylate, methacrylate,
methacrylurethane, vinyl or allyl,
6
R' represents hydrogen or an alkyl group having from 1 to 4 carbon atoms,
X represents a structure with n unit(s) of ethylene oxide EO and m unit(s) of
propylene oxide PO, arranged randomly,
m and n are 2 integers between 0 and 100, at least one of which is non-zero, and are
such that m+n is greater than 17,
the said copolymer having a molecular mass between 200,000 and 50,000,000 g/mol.
Such copolymers are described in the technical sector of paper coating colors used in
the manufacture of paper and board coated with said paper coatings. Notably, in
patent application WO 2004/044022, such copolymers are described as agents for
improving the activation of optical brightness in the manufacture of paper coating
colors. As for patent EP 1 966 441, it describes these copolymers as water retention
agents and rheology modifier agents for paper coating colors.
Surprisingly, such copolymers indeed have a different rheological behaviour in paint
formulations according to the present invention, in the presence of titanium dioxide
particles.
Such copolymers are not described in the prior art as agents for improving the opacity
of film that is dry or in the process of drying in a paint formulation including titanium
dioxide particles.
Thus, the present invention is part of the sector of agents for improving optical
activity, in particular the opacity of products that are dry or in the process of drying,
resulting from aqueous formulations of titanium dioxide-based paints containing the
said agents.
7
By "agent for improving the opacity of the film that is dry or in the process of drying"
is meant an agent that, during or after drying, produces a product whose opacity is
improved. The product is, in the case in point, a film of paint that is in the process of
drying or a dry paint film, i.e., one resulting from the application of a specified
thickness of a water-based paint formulation. In the context of the present invention,
the term "improve" means increasing the value of the opacity for a paint formulation
with a given quantity of TiO2 and an agent according to the invention, compared to a
measured opacity value for the same paint formulation which includes the same given
quantity of TiO2, but not the agent according to the invention.
By "opacity" is meant the ability of a film of paint for a determined application
thickness to cover a black support and the same support in white in an equivalent
manner. In other words, the opacity is the ability of the dry film or film that is in the
process of drying to cover any color situated below. The opacity of a paint film is
determined by measuring the reflectance Rb of a coat of paint of a given thickness on a
black backing, and then the reflectance Rw of a coat of the same paint with the same
thickness on a white backing. The opacity is the percentage of the Rb/Rw ratio.
Reflectance is in this case the magnitude y of the xyz color space. For a given
application thickness, the person skilled in the art seeks to be as close as possible to an
opacity of 100%.
While improving the brightness or the whiteness of the paint film is not an object of
the present invention, the index of brightness is characterized in the examples of the
present application by measuring of the L* component in the Lab color space
(L*a*b*), using a spectrophotometer.
By "brightness" is meant the brightness index of the paint film as determined by
measurement of the L* component in the Lab (L*a*b*) color space using a
spectrophotometer. L* varies between 0 (black) and 100 (white).
8
During the paint drying step, after its application to its support, the pigment and binder
particles come closer together. The final evaporation of the aqueous phase requires
these particles to come close together, to adsorb and/or merge to form a continuous
film. During this final evaporation step, it is sought to prevent flocculation of the
titanium dioxide particles as much as possible. Failing this, some of the optical
qualities of these particles are lost. The present patent application is related to this
problem. More specifically, the present application is based on a particular behaviour
of the copolymer molecules of the present invention in paint formulations containing
titanium dioxide particles. Without wishing to be bound by a theory of any kind with
regard to the results obtained, the inventors are of the opinion that the copolymers
according to the invention exhibit properties of steric hindrance that result in a spacing
of the TiO2 particles in paint formulations, but also maintain the separation of TiO2
particles in the paint film during the drying step, thereby retaining the optical activity
of each particle individually, starting from the paint application step and after drying
of the film applied to its support.
The copolymers according to the invention are "spacing molecules" in paint
formulations containing particles of titanium dioxide which significantly reduce the
phenomenon of titanium dioxide particle flocculation during the paint drying step.
According to the invention, the copolymer used as an agent for improving the optical
activity of titanium dioxide particles has a weight-average molecular mass between
200,000 and 50,000,000 g/mol.
It is interesting to note that, within the framework of the present invention, despite a
high molecular weight, and in comparison to the polymers of the prior art, also of high
molecular weight used as thickeners, the copolymers according to the invention do not
induce a substantial change of viscosities in aqueous formulations that incorporate
them at the indicated concentrations. This is an advantage for the formulator.
9
According to one aspect of the present invention, the copolymer used as a titanium
dioxide particle optical activity-enhancing agent presents a weight-average molecular
mass between 250,000 and 15,000,000 g/mol, for example between 300,000 g/mol
and 6,000,000 g/mol as determined by Gel Permeation Chromatography (GPC).
According to one aspect of the present invention, the said water-soluble copolymer
consists of:
a) 5 to 20% by weight of acrylic acid and/or methacrylic acid monomers and/or any
of their salts, and
b) 80 to 95% by weight of at least one monomer with the formula (I) as described
above.
According to another aspect of the present invention, the said water-soluble
copolymer consists of:
A1) 4 to 15% by weight of acrylic acid monomers or any of its salts,
A2) 1 to 5% by weight of methacrylic acid monomers or any of its salts,
b) 80 to 95% by weight of at least one monomer with the formula (I).
According to still another aspect of the present invention, the said water-soluble
copolymer is such that n and m are two non-zero integers and are such that n+m > 50.
According to still another aspect of the present invention, the said water-soluble
copolymer is such that n and m are two non-zero integers and are such that n+m > 60.
10
According to one aspect of the present invention, the copolymer as defined above is
used as a titanium dioxide particle optical activity-enhancing agent in a paint
formulation with a pigment volume concentration (hereinafter PVC) between
15 and 70%.
The "pigment volume concentration" is defined by the following formula:
PVC (%) = 100 x Vf/ (Vf + Vb)
with Vf which represents the volume of mineral filler and
Vb which represents the volume of binder in the paint formulation.
According to another aspect of the present invention, the copolymer as defined
above is used as a titanium dioxide particle optical activity-enhancing agent in a
paint formulation with a pigment volume concentration (hereinafter PVC) between
15 and 50%.
The present invention also relates to paint formulations including titanium dioxide
particles and a copolymer according to the invention.
More specifically, the present invention also relates a water-based paint formulation
including:
- water,
- titanium dioxide particles, and
- a water-soluble copolymer comprised of:
a) 4 to 25% by weight of acrylic acid and/or methacrylic acid monomers and/or
any of their salts,
11
b) 75 to 96% by weight of at least one monomer with the formula (I):
R – X – R'
(I)
according to which:
R represents a polymerizable unsaturated function, notably acrylate, methacrylate,
methacrylurethane, vinyl or allyl,
R' represents hydrogen or an alkyl group having from 1 to 4 carbon atoms,
X represents a structure with n unit(s) of ethylene oxide EO and m unit(s) of
propylene oxide PO, arranged randomly,
m and n are 2 integers between 0 and 100, at least one of which is non-zero, and are
such that m+n is greater than 17,
the said copolymer having a molecular mass between 250,000 and 50,000,000 g/mol.
According to one aspect of the present invention, the water-based paint formulation
includes 0.05 to 5% by weight of said copolymer.
According to another aspect of the present invention, the water-based paint
formulation includes 0.1 to 2% by weight of said copolymer.
According to one aspect of the present invention, the water-based paint formulation
includes 4 to 40% by weight of titanium dioxide particles.
According to another aspect of the present invention, the water-based paint
formulation includes 15 to 25% by weight of titanium dioxide particles.
12
According to still another aspect of the present invention, the water-based paint
formulation includes at least one other pigment mineral filler selected from the group
consisting of calcium carbonate, kaolin and silicate.
According to still another aspect, the pigmented mineral fillers of the water-based
paint formulation of the present invention are:
- from 30 to 90% by weight of titanium dioxide particles and
- from 10 to 70% by weight of at least one other pigment mineral filler selected
from the group consisting of calcium carbonate, kaolin and silicate.
The said copolymer according to the invention is obtained by known methods of
conventional radical copolymerization in solution, in direct or inverse emulsion in
bulk, in suspension or precipitation in suitable solvents, in the presence of known
starters and transfer agents, or again, by processes of controlled radical polymerization
such as the method known as Reversible Addition Fragmentation Transfer (RAFT),
the method known as Atom Transfer Radical Polymerization (ATRP), the method
known as Nitroxide Mediated Polymerization (NMP), or again, the method so called
Cobaloxime Mediated Free Radical Polymerization.
The following examples allow a better understanding of the present invention, without
however limiting its scope.
EXAMPLES
In each of the following examples, the molecular mass of the copolymers according to
the invention is determined by Gel Permeation Chromatography (GPC) or
equivalently, Steric Exclusion chromatography (SEC).
13
Such a technique makes use of a WATERSTM liquid chromatograph equipped with
two detectors. One of these detectors combines the static dynamic scattering of light at
an angle of 90° to the viscometry measured by a MALVERNTM VISCOTEKTM
viscometer detector. The other of these detectors is a WATERSTM refractrometric
concentration detector.
This liquid chromatography apparatus is equipped with steric exclusion columns
properly chosen by the person skilled in the art in order to separate the different
molecular weights of the polymers studied. The elution liquid phase is an aqueous
phase containing 1% KNO3.
In detail, as a first step the polymerization solution is diluted to 0.9% dry in the GPC
eluent which is a 1% KNO3 solution. Then, it is filtered to 0.2 μm. 100 μL are then
injected into the chromatography apparatus (eluent: a 1% KNO3 solution).
The liquid chromatography apparatus contains an isocratic pump (WATERSTM 515),
the flow rate of which is adjusted to 0.8 ml/min. The chromatography apparatus also
includes an oven which itself includes the following system of columns in series: a 6
cm long, 40 mm inside diameter pre-column of the WATERSTM
ULTRAHYDROGEL GUARD COLUMN type, a 30 cm long, 7.8 mm inside
diameter linear column of the WATERSTM ULTRAHYDROGEL type, and two 30 cm
long, 7.8 mm inside diameter 120 ANGSTROM WATERSTM ULTRAHYDROGEL
type columns. As for the detection system, it consists on the one hand of a
WATERSTM 410 type Refractive Index (RI) Detector, and on the other hand, of a dual
viscometer and light scattering detector set an angle of 90°, of the MALVERNTM 270
DUAL DETECTOR type. The oven is brought to a temperature of 55°C, and the
refractometer is brought to a temperature of 45°C.
The chromatography apparatus is calibrated with a single PEO 19k standard of the
PolyCALTM MALVERNTM type.
14
The preparation of the copolymers is done according to the processes known by the
person skilled in the art. In particular, reference can be made to the different
documents cited in the application as technological background.
In addition, the paints are formulated according to methods known by the person
skilled in the art.
In the examples that follow, measurements of opacity and brightness (or whiteness)
are made as follows:
A 75 μm thick film is deposited on the surface of a black support, and on the same
type of support with a white surface. 24 hours elapses after application of the film to
the support at a temperature of approximately 25°C before taking measurements of the
reflectance Rb of the paint film on a black backing, and the reflectance Rw of the film
on a white backing.
The opacity is the percentage of the Rb/Rw ratio.
Also, the brightness index of the paint film is determined by measurement of the
L* component in the Lab (L*a*b*) color space using a spectrophotometer.
Also determined are the viscosities of said formulations at different shear rates:
- at a low shear rate, the Brookfield viscosity, which is measured using a Brookfield
RVT type viscometer in a non-agitated flask at a temperature of 25°C and at two
rotational speeds of 10 and 100 revolutions per minute with the appropriate
spindle. The reading is taken after 1 minute of rotation. Two Brookfield viscosity
measurements are thus obtained, designated μBK10 and μBK100 (mPa.s) respectively;
- at an average shear rate: the Stormer viscosity, designated μS (Krebs Units) ;
- at a high shear rate: the Cone Plan viscosity or ICI viscosity, designated μI (Poises,
1P = 100 mPa.s).
15
Example 1
This example illustrates the use of an agent according to the invention in a waterbased
paint formulation (including a vinyl acrylic type binder), the composition of
which is given in table 1 below.
Paint constituent Mass (g)
Water 314.0
Thickener (Natrosol® Plus 330) 5.0
Sodium carbonate 2.0
Ionic dispersant (KTTP) 2.0
Anti-foaming agent (FoamStar® A-38) 4.0
Biocide (Proxel® AQ) 1.5
Binder (UCAR® Latex 310) 395.0
Silicate pigment (Minex® 10) See table 2
TiO2 pigment (Kronos® 2310) See table 2
Total additives including the agent according to the present
invention See table 2
Table 1
The tests that follow illustrate the use of a polymer according to the invention as an
agent for improving the opacity of the film that is dry or in the process of drying, of an
aqueous paint formulation including titanium dioxide particles which enables a
reduction in the amount of this pigment in paints.
More specifically, the agent according to the invention here is a copolymer with an
acrylic acid skeleton (8% by weight) and a methacrylic acid skeleton (2.8% by
weight) and branched macromonomers with a structure of 48 EO units and 15 PO
units (89.2% by weight), with a molecular weight of 336,500 g/mol.
16
All the results have been summarized in table 2.
For each test, the opacity, brightness and BK μ10, BK μ100, ICI and Stormer
viscosities were determined according to the methods described above.
Test No. 1 2 3 4 5
TiO2 pigment
(Kronos®
2310)
Mass (g) 300 270 270 270 270
% 100 90 90 90 90
Silicate pigment
(Minex® 10) 145 145 145 175 145
Dispersant (Tamol® 731) 8.20 8.20 1.50 1.50 -
Dispersant
(Coadis® 123K) - - - - 1.50
Agent according to the
invention - - 6.90 6.90 6.90
Total additives 8.20 8.20 8.40 8.40 8.40
Opacity 96.59 95.77 96.53 96.62 96.24
Brightness L* 95.24 95.17 95.01 94.4 95.03
μS 84.1 80.8 79.4 77.6 79.9
μI 0.785 0.665 0.700 0.505 0.725
μBK10 4,640 4,180 3,620 3,380 3,740
μBK100 1,380 1,210 1,140 1,040 1,090
Table 2
It should be noted that the total amount of additive (dispersant plus agent according
to the invention) used is similar in all tests: 8.40 g for tests 3, 4 and 5 versus 8.20 g
for tests 1 and 2.
The TiO2 pigment here is in the form of a suspension of rutile titanium (approximately
76% dry extract by weight). The silicate pigment is in the powder form.
The agent according to the invention is in the form of a solution/emulsion in
water at 25%.
17
The PVC is approximately 25%.
Test 1 corresponds to a control. In test 2, the amount of TiO2 is reduced by 10%
compared to test 1. A decrease of close to one point is then detected in the measured
opacity. Thus, as expected, it is shown that a reduction of 10% in the amount of TiO2
pigment leads to a significant reduction in the measured opacity.
In test 3, the amount of TiO2 in the paint is reduced by 10%, but an agent according to
the invention is added (proportion: 0.6% by weight). Thus, it is demonstrated that
despite the decrease in the amount of TiO2 in the paint, the opacity of the paint
remains constant.
The agent according to the invention improves the spacing between the TiO2 particles
during the paint film drying step (measurement of the opacity of the dry paint film),
which allows a better optical activity of the titanium dioxide particles in order to
obtain a better opacity of the dry paint film, so that it is possible to decrease the
proportion of said TiO2 particles in the paint while maintaining the same opacity
level.
It is also interesting to note that the viscosity measured in tests 3 and 5, specifically at
a low or average shear gradient, are comparable to those of the control test.
In test 4, the amount of TiO2 in the paint is reduced by 10%, an agent according to the
invention is added (proportion 0.6% by weight, identical to test 2) and the loss of TiO2
pigment is compensated for by the addition of 30 g of an another pigment, i.e., a
silicate pigment.
The measured opacity is then of the same order of magnitude as the opacity measured
without compensation (test 3). Thus, the addition of an agent according to the
invention allows a reduction in the amount of TiO2 pigment particles without the need
18
to compensate for this reduction by the addition of another pigment to the
composition. This represents an advantage in terms of costs.
In test 5, a dispersant, namely Tamol® 731, is replaced by a dispersant with a different
polymeric composition, i.e. Coadis® 123K. It is shown that the resulting opacity is of
the same order of magnitude as that obtained for test 3 or test 4, so that the choice of
the dispersant's polymeric composition does not, in this case of these tests, have an
impact on the opacity value.
To be noted that the addition of an agent according to the invention has no significant
effect on the brightness (or whiteness) L* of the paint film.
Example 2
This example illustrates the use of an agent according to the invention in another
water-based paint formulation (including in particular an acrylic type binder), the
composition of which is given in table 3 below.
Paint constituent Mass (g)
Water 236.8
Biocide (Proxel® AQ) 1.5
Surfactant (Strodex® PK-0VOC) 2.0
Anti-foaming agent (Rhodoline® 643) 6.0
Neutralizing agent (AMP 95) 2.0
Binder (UCAR® Latex 631) 500.0
Coalescent agent (Texanol®) 12.5
Thickener (Coapur® XS 71) 1.0
Thickener (Rheotech® 2000) 7.0
Kaolin Pigment (Polygloss® 90) 35.0
TiO2 pigment (Ti-Pure® R-706) See table 4
Agent according to the invention See table 4
Table 3
19
In particular, the agent according to the invention here is a copolymer with an acrylic
acid skeleton (8% by weight) and a methacrylic acid skeleton (2.8% by weight) and
branched macromonomers with a structure (89.2% by weight), with a molecular
weight of 336,500 g/mol.
All the results have been summarized in table 4.
For each test, the opacity, brightness and BK μ10, BK μ100, ICI and Stormer
viscosities were determined according to the methods described above.
Test No. 6 7 8
TiO2 pigment (Ti-Pure® R-706)
Mass (g) 235 211.5 211.5
% 100 90 90
Dispersant (Rhodoline® 286N) 6.2 6.2 1.0
Agent according to the invention - - 27.0
Opacity 97.56 97.04 97.43
Brightness L* 96.06 95.79 95.60
Table 4
The TiO2 pigment here is in the form of a suspension of rutile titanium (approximately
76% dry extract by weight).
In test 2, the amount of TiO2 in the paint is reduced by 10%. In doing so, the measured
opacity is reduced. Thus, as expected, it is shown that a reduction of 10% in the
amount of TiO2 pigment leads to a reduction in the measured opacity.
In test 3, the amount of TiO2 in the paint is reduced by 10%, but an agent according to
the invention is added (proportion 3% by weight).
It is apparent that the measured opacity is similar to that obtained in the case of the
control test at 100% TiO2. The agent according to the invention therefore enables the
maintenance of the spacing between the TiO2 particles during the paint film drying
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step (measurement of the opacity of the dry paint film), which allows a better optical
activity of the titanium dioxide particles. It is shown here that it is possible to decrease
the amount of TiO2 in paints without losing opacity on the paint film.
To be noted that the addition of an agent according to the invention has no significant
effect on the brightness (or whiteness) L* of the paint film.
For all practical purposes, it is specified that the rheological properties of the various
formulations presented are comparable between the different tests and compatible
with the paint application.
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WE CLAIM :
1. Use, in a paint formulation containing titanium dioxide particles, as an agent
for improving the opacity of the film that is dry or in the process of drying, of a
water-soluble copolymer consisting of:
a) 4 to 25% by weight of acrylic acid and/or methacrylic acid monomers
and/or any of their salts,
b) 75 to 96% by weight of at least one monomer with the formula (I):
R – X – R'
(I)
according to which:
R represents a polymerizable unsaturated function, notably acrylate,
methacrylate, methacrylurethane, vinyl or allyl,
R' represents hydrogen or an alkyl group having from 1 to 4 carbon atoms,
X represents a structure with n unit(s) of ethylene oxide EO and m unit(s) of
propylene oxide PO, arranged randomly,
m and n are 2 integers between 0 and 100, at least one of which is non-zero,
and are such that m + n is greater than 17,
said copolymer having a molecular mass between 200,000 and 50,000,000
g/mol.
2. Use according to claim 1, according to which said water-soluble copolymer has
a molecular mass between 250,000 and 15,000,000 g/mol.
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3. Use according to claim 1 or 2, according to which said copolymer consists in:
a) 5 to 20% by weight of acrylic acid and/or methacrylic acid monomers
and/or any of their salts, and
b) 80 to 95% by weight of at least one monomer with the formula (I).
4. Use according to any of the preceding claims according to which said
water-soluble copolymer consists in:
A1) 4 to 15% by weight of acrylic acid monomers or any of its salts,
A2) 1 to 5% by weight of methacrylic acid monomers or any of its salts, and
b) 80 to 95% by weight of at least one monomer with the formula (I).
5. Use according to any of the preceding claims according to which said
water-soluble copolymer is such that n and m are two non-zero integers and are
such that n+m>50.
6. Water-based paint formulation including:
- water,
- titanium dioxide particles and
- a water-soluble copolymer consisting essentially in:
a) 4 to 25% by weight of acrylic acid and/or methacrylic acid monomers
and/or any of their salts,
b) 75 to 96% by weight of at least one monomer with the formula (I):
R – X – R'
(I)
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according to which:
R represents a polymerizable unsaturated function, notably acrylate,
methacrylate, methacrylurethane, vinyl or allyl,
R' represents hydrogen or an alkyl group having from 1 to 4 carbon atoms,
X represents a structure with n unit(s) of ethylene oxide EO and m unit(s) of
propylene oxide PO, arranged randomly,
m and n are 2 integers between 0 and 100, at least one of which is non-zero,
and are such that m + n is greater than 17,
the said copolymer having a molecular mass between 200,000 and 50,000,000
g/mol.
7. Water-based paint formulation according to claim 6 according to which said
formulation includes from 0.05 to 5% by weight of said copolymer.
8. Water-based paint formulation according to claim 6 or 7 according to which the
said formulation includes from 4 to 40% by weight of titanium dioxide
particles.
9. Formulation according to any of claims 6 to 8 according to which said
formulation includes from 15 to 25% by weight of titanium dioxide particles.
10. Formulation according to any of claims 6 to 9 according to which said
formulation includes at least one other pigment mineral filler selected from the
group consisting of calcium carbonate, kaolin, and silicate.