U.S. patent application number 14/017648 was filed with the patent office on 2014-01-02 for rheology modifiers for modifying the rheological behaviour of coating compositions.
This patent application is currently assigned to BASF SE. The applicant listed for this patent is BASF SE. Invention is credited to Laurent Brauge, Tamal Ghosh, Celine Hossenlopp, Tiina Luttikhedde, Malcolm Skinner.
Application Number | 20140004368 14/017648 |
Document ID | / |
Family ID | 37057297 |
Filed Date | 2014-01-02 |
United States Patent
Application |
20140004368 |
Kind Code |
A1 |
Ghosh; Tamal ; et
al. |
January 2, 2014 |
RHEOLOGY MODIFIERS FOR MODIFYING THE RHEOLOGICAL BEHAVIOUR OF
COATING COMPOSITIONS
Abstract
The present invention provides rheology modifiers, which are
water-soluble polymers having a weight average molecular weight
(Mw) of at least 1'000'000 g/mol and an intrinsic viscosity of at
least 2.5 dl/g, both as determined by size exclusion
chromatography, and wherein the water-soluble polymers are in the
form of solid particles. It also provides mixtures of rheology
modifiers comprising a first rheology modifier, which is a
water-soluble polymer having a weight average molecular weight (Mw)
of at least 1'000'000 g/mol and an intrinsic viscosity of at least
2.5 dl/g, both as determined by size exclusion chromatography, and
a second rheology modifier, which has a weight average molecular
weight of from 2'000 g/mol to 800'000 g/mol. It also provides
coating composition containing the rheology modifiers,
respectively, mixtures of rheology modifiers, a process for their
preparation, a process for coating a substrate using these coating
compositions and substrates coated with these coating
compositions.
Inventors: |
Ghosh; Tamal; (Hopewell
Junction, NY) ; Skinner; Malcolm; (Bradford, GB)
; Luttikhedde; Tiina; (Markelo, NL) ; Hossenlopp;
Celine; (Mulhouse, FR) ; Brauge; Laurent;
(Ribecourt-Dreslincourt, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BASF SE |
Ludwigshafen |
|
DE |
|
|
Assignee: |
BASF SE
Ludwigshafen
DE
|
Family ID: |
37057297 |
Appl. No.: |
14/017648 |
Filed: |
September 4, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11991758 |
Aug 11, 2009 |
8552132 |
|
|
PCT/EP2006/065951 |
Sep 4, 2006 |
|
|
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14017648 |
|
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Current U.S.
Class: |
428/522 ;
427/420; 524/521; 524/547; 524/555; 525/201; 525/218; 526/240;
526/303.1; 526/307.6 |
Current CPC
Class: |
C08F 220/06 20130101;
C08F 220/56 20130101; C09D 5/04 20130101; Y10T 428/31935 20150401;
C09D 133/26 20130101; C08F 120/56 20130101; C08L 33/26
20130101 |
Class at
Publication: |
428/522 ;
526/303.1; 526/240; 526/307.6; 524/555; 524/547; 525/201; 525/218;
524/521; 427/420 |
International
Class: |
C09D 133/26 20060101
C09D133/26; C08F 220/56 20060101 C08F220/56; C08L 33/26 20060101
C08L033/26; C08F 120/56 20060101 C08F120/56 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 14, 2005 |
EP |
05108440.8 |
Jul 25, 2006 |
EP |
06117808.3 |
Claims
1-4. (canceled)
5. A process for preparing a coating composition comprising the
steps of (i) providing a rheology modifier, wherein the rheology
modifier is a water-soluble polymer having a weight average
molecular weight (Mw) of at least 1,000,000 g/mol and an intrinsic
viscosity of at least 2.5 dl/g, both as determined by size
exclusion chromatography, and wherein the water-soluble polymer is
in the form of solid particles, (ii) optionally forming an aqueous
solution or inverse (water-in-oil) emulsion of the rheology
modifiers of claim 1, and (iii) mixing the rheology modifiers of
step (i) or the aqueous solution or inverse emulsion of the
rheology modifiers obtained in step (ii) with a binder, a pigment,
a carrier solvent and optional additives in order to form a coating
composition.
6. A coating composition obtainable by the process of claim 5.
7. A process for coating a substrate comprising the steps of (i)
providing a rheology modifier, wherein the rheology modifier is a
water-soluble polymer having a weight average molecular weight (Mw)
of at least 1,000,000 g/mol and an intrinsic viscosity of at least
2.5 dl/g, both as determined by size exclusion chromatography, and
wherein the water-soluble polymer is in the form of solid
particles, (ii) optionally forming an aqueous solution or inverse
(water-in-oil) emulsion of the rheology modifier, (iii) mixing the
rheology modifier of step (i) or the aqueous solution or inverse
emulsion of the rheology modifier obtained in step (ii) with a
binder, a pigment, a carrier solvent and optional additives in
order to form a coating composition, and (iv) applying the coating
composition obtained in step (iii) onto a substrate.
8. The process of claim 7 wherein the substrate is made from paper,
cardboard or polymer.
9. The process of claim 8, wherein the substrate is made from
paper.
10. The process of claim 7, wherein the coating composition is
applied by curtain coating onto the substrate.
11. A substrate coated by the process of claim 7.
12-13. (canceled)
14. A mixture of rheology modifiers comprising a first rheology
modifier, which is a water-soluble polymer having a weight average
molecular weight (Mw) of at least 1,000,000 g/mol and an intrinsic
viscosity of at least 2.5 dl/g, both as determined by size
exclusion chromatography, and a second rheology modifier, which has
a weight average molecular weight of from 2,000 g/mol to 800,000
g/mol, as determined by size exclusion chromatography.
15. The mixture of rheology modifiers of claim 14, wherein the
first rheology modifier is a polymer composed of monomer units
derived from (i) at least one monomer of formula I ##STR00005##
whereby R.sup.1 and R.sup.2 can be the same or different and are
hydrogen, C.sub.1-6-alkyl or C.sub.5-8-cycloalkyl, or R.sup.1 and
R.sup.2 can together with the nitrogen to which they are attached
form a heterocyclic 5- or 6-membered ring, whereby C.sub.1-6-alkyl
may be substituted with amino, hydroxyl, halogen, C.sub.1-4-alkoxy,
aryl or mono- or diC.sub.1-4-alkylamino, and R.sup.3 and R.sup.4
can be the same or different and are hydrogen, C.sub.1-6-alkyl,
C.sub.5-8-cycloalkyl, halogen, aryl or NHCOC.sub.1-4-alkyl, whereby
C.sub.1-6-alkyl may be substituted with amino, hydroxyl, halogen,
C.sub.1-4-alkoxy, aryl or mono- or diC.sub.1-4-alkylamino, and (ii)
optional other ethylenically unsaturated monomers.
16. The mixture of rheology modifiers of claim 15, wherein the
optional other ethylenically unsaturated monomers comprise at least
one monomer of formula II ##STR00006## whereby R.sup.5 and R.sup.6
can be the same or different and are hydrogen, C.sub.1-6-alkyl,
C.sub.5-8-cycloalkyl, halogen, aryl or NHCOC.sub.1-4-alkyl, whereby
C.sub.1-6-alkyl may be substituted with amino, hydroxyl, halogen,
C.sub.1-4-alkoxy, aryl or mono- or diC.sub.1-4-alkylamino, and M is
hydrogen, ammonium, mono-, di-, tri- or
tetraC.sub.1-4-alkylammonium, alkali metal or earth alkaline
metal.
17. The mixture of rheology modifiers of claim 14, wherein the
second theology modifier is prepared from a monomer mixture
comprising at least one acrylic monomer.
18. A process for preparing a coating composition which comprises
the steps of (i) providing the mixture of rheology modifiers of
claim 14 (ii) mixing the mixture of rheology modifiers of step (i)
with a binder, a pigment, a carrier solvent and optional additives
in order to form a coating composition.
19. A coating composition obtainable by the process of claim
18.
20. A process for coating a substrate comprising the steps of (i)
providing the mixture of rheology modifiers of claim 14, (ii)
mixing the mixture of rheology modifiers of step (i) with a binder,
a pigment, a carrier solvent and optional additives in order to
form a coating composition, and (iii) applying the coating
composition obtained in step (iii) onto the substrate.
21. The process of claim 20 wherein the substrate is made from
paper, cardboard or polymer.
22. The process of claim 21, wherein the substrate is made from
paper.
23. The process of claim 20, wherein the coating composition is
applied by blade coating onto the substrate.
24. A substrate coated by the process of claim 20.
25-26. (canceled)
27. A method for reducing white pitch in the production of coated
paper comprising the step of coating the paper with a coating
composition comprising the mixture of rheology modifiers of claim
14.
28. The process of claim 5, wherein the water-soluble polymer is
composed of monomer units derived from (i) at least one monomer of
formula I ##STR00007## whereby R.sup.1 and R.sup.2 can be the same
or different and are hydrogen, C.sub.1-6-alkyl or
C.sub.5-8-cycloalkyl, or R.sup.1 and R.sup.2 can together with the
nitrogen to which they are attached form a heterocyclic 5- or
6-membered ring, whereby C.sub.1-6-alkyl may be substituted with
amino, hydroxyl, halogen, C.sub.1-4-alkoxy, aryl or mono- or
diC.sub.1-4-alkylamino, and R.sup.3 and R.sup.4 can be the same or
different and are hydrogen, C.sub.1-6-alkyl, C.sub.5-8-cycloalkyl,
halogen, aryl or NHCOC.sub.1-4-alkyl, whereby C.sub.1-6-alkyl may
be substituted with amino, hydroxyl, halogen, C.sub.1-4-alkoxy,
aryl or mono- or diC.sub.1-4-alkylamino, and (ii) optional other
ethylenically unsaturated monomers.
29. The process of claim 28, wherein the optional other
ethylenically unsaturated monomers comprise at least one monomer of
formula II ##STR00008## whereby R.sup.5 and R.sup.6 can be the same
or different and are hydrogen, C.sub.1-6-alkyl,
C.sub.5-8-cycloalkyl, halogen, aryl or NHCOC.sub.1-4-alkyl, whereby
C.sub.1-6-alkyl may be substituted with amino, hydroxyl, halogen,
C.sub.1-4-alkoxy, aryl or mono- or diC.sub.1-4-alkylamino, and M is
hydrogen, ammonium, mono-, di-, tri- or
tetraC.sub.1-4-alkylammonium, alkali metal or earth alkaline
metal.
30. The process of claim 7, wherein the water-soluble polymer is
composed of monomer units derived from (i) at least one monomer of
formula I ##STR00009## whereby R.sup.1 and R.sup.2 can be the same
or different and are hydrogen, C.sub.1-6-alkyl or
C.sub.5-8-cycloalkyl, or R.sup.1 and R.sup.2 can together with the
nitrogen to which they are attached form a heterocyclic 5- or
6-membered ring, whereby C.sub.1-6-alkyl may be substituted with
amino, hydroxyl, halogen, C.sub.1-4-alkoxy, aryl or mono- or
diC.sub.1-4-alkylamino, and R.sup.3 and R.sup.4 can be the same or
different and are hydrogen, C.sub.1-6-alkyl, C.sub.5-8-cycloalkyl,
halogen, aryl or NHCOC.sub.1-4-alkyl, whereby C.sub.1-6-alkyl may
be substituted with amino, hydroxyl, halogen, C.sub.1-4-alkoxy,
aryl or mono- or diC.sub.1-4-alkylamino, and (ii) optional other
ethylenically unsaturated monomers.
31. The process of claim 28, wherein the optional other
ethylenically unsaturated monomers comprise at least one monomer of
formula II ##STR00010## whereby R.sup.5 and R.sup.6 can be the same
or different and are hydrogen, C.sub.1-6-alkyl,
C.sub.5-8-cycloalkyl, halogen, aryl or NHCOC.sub.1-4-alkyl, whereby
C.sub.1-6-alkyl may be substituted with amino, hydroxyl, halogen,
C.sub.1-4-alkoxy, aryl or mono- or diC.sub.1-4-alkylamino, and M is
hydrogen, ammonium, mono-, di-, tri- or
tetraC.sub.1-4-alkylammonium, alkali metal or earth alkaline metal.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a .sctn.371 National Stage Application
of PCT International Application No. PCT/EP2006/065951, filed Sep.
4, 2006, and claims priority under 35 U.S.C. .sctn.119 and/or
.sctn.365 of European Application No. 05108440.8 filed Sep. 14,
2005 and European Application No. 06117808.3 filed Jul. 25,
2006.
BACKGROUND
[0002] The present invention refers to rheology modifiers and to
mixtures of rheology modifiers for modifying the rheological
behaviour of coating compositions, to coating compositions
containing these rheology modifiers and to substrates coated with
these coating compositions. It also refers to processes for the
preparation of the rheology modifiers and the coating compositions
and to processes for coating the substrates.
[0003] Coating compositions for coating a substrate usually include
a rheology modifier in order to adapt the rheological behaviour of
the coating color (synonymous to coating composition) to the
coating device and coating conditions. Traditional coating
techniques such as blade coating and roll coating require coating
compositions of relatively high "low shear viscosity" (synonymous
to Brookfield viscosity) and low "apparent high shear viscosity".
Curtain coating, a relatively recent coating technique, involves
adding the coating composition as a falling thin curtain onto the
substrate. This method requires coating compositions of relatively
low "low shear viscosity", but high "apparent extensional
viscosity" (synonymous to high strechability), as the coating
composition curtain should not break especially when the substrate
moves at high speed.
[0004] Rheology modifiers are usually polymers. Whereas many
rheology modifiers, which in a coating composition exhibit high
"low shear viscosity" and low "apparent high shear viscosity", and
thus are suitable for traditional coating techniques, are known,
rheology modifiers, which as aqueous solution exhibit high
"apparent extensional viscosity" and are thus suitable for curtain
coating, are rare.
[0005] One rheology modifier, that is commercially available and is
capable of providing aqueous solutions of high "apparent
extensional viscosities", is STEROCOLL.RTM. BL (BASF,
acrylamide/acrylic acid copolymers having a Mw of about
10,000,000). The disadvantage of this rheology modifier is that it
is only obtainable as an inverse (water-in-oil) emulsion. Inverse
emulsions are unstable as the phases can easily separate and prone
to freezing, which can cause the formation of undissolved gel
particles. Therefore, inverse emulsions require additional
equipment such as mixing or heating devices when stored,
transported or added into the coating composition and thus are
difficult to handle. In addition, inverse emulsions generate oil
waste, and thus for environmental reasons demand a special clean-up
after use.
[0006] It is a first object of the present invention to provide a
rheology modifier for coating compositions, which is capable of
providing aqueous solutions of high "apparent extensional
viscosities", and which is easy to handle and does not cause
environmental problems.
[0007] This object is solved by the rheology modifiers discussed
herein, the processes for preparing the rheology modifiers, the
coating composition obtainable by the process for preparing
reheology modifiers, and a substrate coated by by the process for
preparing the rheology modifiers.
[0008] In some coating processes for preparing coated paper, which
include blade coating operations, coating compositions of a higher
than usual low "apparent high shear viscosity" are required.
Coating compositions having a high amount of polyvinyl alcohol as
co-binder are known to fulfill this requirement. However, when
waste paper coated with these compositions is recycled, a paper
stock containing sticky material of light colour, so-called "white
pitch", is obtained resulting in "white pitch" throughout the paper
machine and in low-quality paper. As a consequence, the machine has
to be stopped and cleaned, and in order to avoid further formation
of "white pitch" an increased demand of chemicals, for example
fixatives, in the wet end is needed.
[0009] In some cases, the formation of "white pitch" is related to
the presence of polyvinyl alcohol in the paper stock as discussed
in Teirfolk, J.-E, Hossenlopp, C., Castaing, J.-C., "Interactions
between latex, calcium ions and polyvinyl alcohol",
PTS-Streicherei-Symposium, 2001.
[0010] Therefore, it is a second object of the present invention to
provide a rheology modifier for coating compositions, which is
capable of forming coating compositions of higher than usual low
"apparent high shear viscosity" without requiring the presence of
high amounts of polyvinyl alcohol as co-binder.
[0011] This object is solved by the mixture of rheology modifiers
described herein, the process for preparing a coating composition
discussed herein, and a substrate coated by the process for
preparing a coating composition, as discussed herein.
[0012] The rheology modifiers of the first aspect of present
invention are water-soluble polymers having a weight average
molecular weight (Mw) of at least 1,000,000 g/mol and an intrinsic
viscosity of at least 2.5 dl/g, both as determined by size
exclusion chromatography, and the rheology modifiers are in the
form of solid particles.
[0013] Preferably, the polymers have a weight average molecular
weight (Mw) of at least 2,000,000 g/mol and an intrinsic viscosity
of at least 3.5 dl/g, both as determined by size exclusion
chromatography. More preferably, the polymers have a weight average
molecular weight (Mw) of at least 2,500,000 g/mol and an intrinsic
viscosity of at least 4.5 dl/g, both as determined by size
exclusion chromatography.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 shows "low shear viscosities" of aqueous solutions of
the rheology modifiers of the first aspect of the present invention
and of comparative rheology modifiers at 30 g/l, 60 g/L and 90 g/L
of theology modifier.
[0015] FIGS. 2 and 3 show "apparent extensional viscosities" of
aqueous solutions of the rheology modifiers of the first aspect of
the present invention and of comparative rheology modifiers at 30
g/L rheology modifier.
[0016] FIG. 4 shows the "apparent high shear viscosities" at
different shear rates of coating compositions, suitable for
processes of preparing coated paper, which involve blade coating
operations and require coating composition of higher than usual low
"apparent high shear viscosity", containing a mixture of rheology
modifiers of the second aspect of the present invention.
[0017] FIG. 5 shows the "water retention properties" at different
solid contents of coating compositions, suitable for processes for
preparing coated paper, which involve blade coating operations and
require coating composition of higher than usual low "apparent high
shear viscosity, containing a mixture of rheology modifiers of the
second aspect of the present invention.
DETAILED DESCRIPTION
[0018] Preferably, the solid particles are beads. Preferably, the
beads have a diameter in the range of 1 to 1000 .mu.m, more
preferably, of 100 to 400 .mu.m.
[0019] Water-soluble means that at least 1 g of polymer dissolves
in 100 g water to form a viscous solution.
[0020] Preferably, the polymers are composed of monomer units
derived from
(i) at least one monomer of formula I
##STR00001## [0021] whereby [0022] R.sup.1 and R.sup.2 can be the
same or different and are hydrogen, C.sub.1-6-alkyl or
C.sub.5-8-cycloalkyl, or R.sup.1 and R.sup.2 can together with the
nitrogen to which they are attached form a heterocyclic 5- or
6-membered ring, whereby C.sub.1-6-alkyl may be substituted with
amino, hydroxyl, halogen, C.sub.1-4-alkoxy, aryl or mono- or
diC.sub.1-4-alkylamino, and [0023] R.sup.3 and R.sup.4 can be the
same or different and are hydrogen, C.sub.1-6-alkyl,
C.sub.5-8-cycloalkyl, halogen, aryl or NHCOC.sub.1-4-alkyl, whereby
C.sub.1-6-alkyl may be substituted with amino, hydroxyl, halogen,
C.sub.1-4-alkoxy, aryl or mono- or diC.sub.1-4-alkylamino, and (ii)
optional other ethylenically unsaturated monomers.
[0024] Examples of C.sub.1-6-alkyl are methyl, ethyl, propyl,
isopropyl, butyl, sec-butyl, tert-butyl, isobutyl, pentyl and
hexyl. Examples of C.sub.5-8-cycloalkyl are cyclopentyl, cyclohexyl
and cycloheptyl. Examples of 5- or 7-membered heterocyclic rings
are morpholino, pyrrolidino and piperidino. Examples of aryl are
phenyl and substituted phenyl such as tolyl. Examples of halogen
are bromine and chlorine. Examples of C.sub.1-4-alkoxy are methoxy,
ethoxy, propoxy, isopropoxy, butoxy, sec-butoxy, tert-butoxy and
isobutoxy. Examples of mono- or diC.sub.1-4-alkylamino are
N-methylamino, N,N-ethylmethylamino, N,N-diethylamino,
N,N-dipropylamino, N-isopropylamino and N,N-dibutylamino.
[0025] Examples of monomers of formula (I) are (meth)acrylamide,
N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide,
N-isopropyl(meth)acrylamide.
[0026] Preferably, R.sup.1 and R.sup.2 can be the same or different
and are hydrogen or C.sub.1-4-alkyl, whereby C.sub.1-4-alkyl may be
substituted with amino or mono- or diC.sub.1-4-alkylamino, and
[0027] R.sup.3 and R.sup.4 can be the same or different and are
hydrogen, C.sub.1-4-alkyl or NHCOC.sub.1-4-alkyl, whereby
C.sub.1-4-alkyl may be substituted with amino or mono- or
diC.sub.1-4-alkylamino.
[0028] Examples of C.sub.1-4-alkyl are methyl, ethyl, propyl,
isopropyl, butyl, sec-butyl, tert-butyl, and isobutyl.
[0029] More preferably, R.sup.1 and R.sup.2 can be the same or
different and are hydrogen or C.sub.1-4-alkyl, and R.sup.3 and
R.sup.4 can be the same or different and are hydrogen or
C.sub.1-4-alkyl.
[0030] Even more preferably, R.sup.1 and R.sup.2 are hydrogen, and
R.sup.3 and R.sup.4 are the same or different and are hydrogen or
C.sub.1-4-alkyl.
[0031] Most preferably, R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are
hydrogen.
[0032] Any suitable other ethylenically unsaturated monomer can be
used. Examples of other ethylenically unsaturated monomers are
acrylic monomers, styrene monomers, vinyl monomers, maleic monomers
and allyl monomers.
[0033] Examples of acrylic monomers are (meth)acrylic acid or salts
thereof, (meth)acrylamide, (meth)acrylonitrile, C.sub.1-6-alkyl
(meth)acrylates such as ethyl (meth)acrylate, butyl(meth)acrylate
or hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate,
di(C.sub.1-4-alkylamino)-C.sub.1-4-alkyl (meth)acrylates such as
dimethylaminoethyl acrylate or diethylaminoethyl acrylate, amides
formed from di(C.sub.1-4-alkylamino)C.sub.1-6-alkylamines and
(meth)acrylic acid and C.sub.1-4-alkyl halide adducts thereof.
[0034] Examples of styrene monomers are styrene, 4-methylstyrene
and 4-vinylbiphenyl. Examples of vinyl monomers are vinyl alcohol,
vinyl chloride, vinylidene chloride, vinyl isobutyl ether and vinyl
acetate. Examples of olefin monomers are ethylene, propylene,
butadiene and isoprene and chlorinated or fluorinated derivatives
thereof such as tetrafluoroethylene. Examples of maleic monomers
are maleic acid, maleic anhydride and maleimide. An example of an
allyl monomer is diallyldimethylammonium chloride.
[0035] Preferably, the optional other ethylenically unsaturated
monomers comprise at least one monomer of formula II
##STR00002##
whereby
[0036] R.sup.5 and R.sup.6 can be the same or different and are
hydrogen, C.sub.1-6-alkyl, C.sub.5-8-cycloalkyl, halogen, aryl or
NHCOC.sub.1-4-alkyl, whereby C.sub.1-4-alkyl may be substituted
with amino, hydroxyl, halogen, C.sub.1-4-alkoxy, aryl or mono- or
diC.sub.1-4-alkylamino, and
[0037] M is hydrogen, ammonium, mono-, di-, tri- or
tetraC.sub.1-4-alkylammonium, alkali metal or earth alkaline
metal.
[0038] Examples of mono-, di-, tri- or tetraC.sub.1-4-alkylammonium
are N-ethylammonium, N,N-diethyl-ammonium and
N,N,N-tributylammonium. Examples of alkali metals are sodium,
potassium and lithium. Examples of earth alkaline metals are
magnesium and calcium.
[0039] Examples of monomers of formula (II) are (meth)acrylic acid,
ammonium (meth)acrylate, sodium (meth)acrylate.
[0040] Preferably, R.sup.5 and R.sup.6 can be the same or different
and are hydrogen, C.sub.1-4-alkyl or NHCOC.sub.1-4-alkyl, and M is
hydrogen, ammonium, mono-, di-, tri- or
tetraC.sub.1-4-alkylammonium, alkali metal or earth alkaline
metal.
[0041] More preferably, R.sup.5 and R.sup.6 are the same or
different and are hydrogen or C.sub.1-4-alkyl, and M is hydrogen,
ammonium, or alkali metal. Most preferably, R.sup.5 and R.sup.6 are
hydrogen, and M is hydrogen, ammonium, or alkali metal.
[0042] Preferably, the polymers are obtainable by polymerisation of
at least one monomer of formula (I) and at least one monomer of
formula (II).
[0043] Preferably the molar ratio of monomers of formula
(I)/monomers of formula (II) is from 90:1 to 1:90, more preferably
it is from 10:1 to 1:10, even more preferably, it is from 5:1 to
1:5, and most preferably it is from 1:1 to 1:5.
[0044] Also part of the first aspect of the invention is a process
for preparing the rheology modifiers of the present invention,
which comprises the steps of [0045] (i) preparing an aqueous
solution of the monomer of formula (I) and optional other
ethylenically unsaturated monomers, [0046] (ii) mixing the monomer
solution with a water-immiscible solvent, [0047] (iii) polymerizing
the monomers in the presence of an initiator, [0048] (iv) removing
water by distillation to form solid polymer particles, and [0049]
(v) separating the solid polymer particles from the reaction
mixture.
[0050] It is possible to start the distillation of water already
during step (iii).
[0051] Examples of water-immiscible solvent are mineral oils or
hydrocarbon liquids such as EXXSOL.TM. D40 FLUID (EXXONMOBIL.RTM.,
light hydrotreated petroleum distillates), or ISOPAR.TM. G
(EXXONMOBIL.RTM., isoparaffinic hydrocarbons), hydrophobic
carboxylic acid esters such as dibutyl phthalate or dioctyl
phthalate, fatty acid triglycerides such as soyabean oil or
sunflower oil, and silicone oils.
[0052] Preferably, the water-immiscible solvent is a mineral oil or
hydrocarbon liquid.
[0053] The initiator can be a peroxide, a persulfate, an azo
compound, a redox couple or mixtures thereof.
[0054] Examples of peroxides are hydrogen peroxide, potassium
peroxide, tert-butyl peroxide, tert-butyl hydroperoxide, cumane
hydroperoxide and benzoyl peroxide. Examples of persulfates are
ammonium, sodium or potassium persulfate. Examples of azo compounds
are 2,2-azobisisobutyronitrile, 4,4'-azobis(4-cyanovaleric acid)
and 2,2'-azobis(N,N'-dimethyl-eneisobutyramidine)dihydrochloride,
1,1'-azobis(cyclohexanecarbonitrile) and
2,2'-azobis(2-amidinopropane)dihydrochloride. Redox couples consist
of an oxidizing agent and a reducing agent. The oxidizing agent can
be one of the above listed peroxides, persulfates, sulfates or azo
compounds, or an alkali metal chlorate or bromate. Examples of
reducing agents are ascorbic acid, glucose or ammonium or alkali
metal hydrogen sulfite, sulfite, thiosulfate or sulfide, or ferrous
ammonium sulfate.
[0055] Preferably, the initiator is a mixture of a redox couple and
one or more Initiators selected from the group consisting of
peroxides, persulfates and azo compounds.
[0056] More preferably, the initiator is a mixture of a redox
couple, wherein the oxidizing agent is selected from the group
consisting of peroxides and alkali metal bromates, and the reducing
agent is selected from the group consisting of ammonium or alkali
metal hydrogen sulfite, sulfite, thiosulfate or sulfide, or ferrous
ammonium sulfate, with one or more azo compound initiators.
[0057] Even more preferably, the initiator is a mixture of a redox
couple, wherein the oxidizing agent is a peroxide and the reducing
agent is an alkali metal hydrogen sulfite or sulfite, with one or
more azo compound initiators.
[0058] Most preferably, the initiator is a mixture of a redox
couple, wherein the oxidizing agent is tert-butylhydroperoxide and
the reducing agent is sodium sulfite, and
2,2'-azobis(2-amidinopropane)dihydrochloride as azo compound
initiator.
[0059] Preferably, the polymerization is performed in the presence
of a chain transfer agent.
[0060] Examples of chain transfer agents are sodium hypophosphite,
mercapto ethanol, thioglycolic acid, formic acid and malic acid. A
preferred chain transfer agent is sodium hypophosphite.
[0061] Preferably, the polymerization is performed in the presence
of a polymeric stabilizer and/or a sequesterant agent.
[0062] Examples of polymeric stabilizer are C.sub.1-20-alkyl
(metha)acrylate (meth)acrylic acid copolymers. Examples of
C.sub.1-20-alkyl are methyl, ethyl, propyl, butyl, pentyl, hexyl,
heptyl, octyl, nonyl, decyl, undecyl, dodecyl, myristyl and
stearyl. A preferred polymeric stabilizer is stearyl
methacrylate:methacrylic acid copolymer.
[0063] Examples of sequesterant agents are
ethylenediaminetetraacetic acid and diethylene-triaminepentaacetic
acid, penta sodium salt.
[0064] Preferably, the ratio of water-immiscible solvent/water is
between 10:1 and 1:10, more preferably, it is between 5:1 and 1:5,
most preferably, it is between 4:1 and 1:1.
[0065] Preferably, the concentration of monomer or monomers in the
aqueous phase is between 0.1 and 20 mol/L, more preferably, it is
between 1 and 15 mol/L, most preferably, it is between 7 and 12
mol/L.
[0066] Preferably, the molar ratio of initiator or
initiators/monomer or monomers is between 0.0001% and 1%, more
preferably, it is between 0.001% and 0.1%, most preferably, it is
between 0.01% and 0.05%.
[0067] Preferably, the molar ratio of chain transfer agent/monomer
or monomers is between 0.001% and 10%, more preferably, it is
between 0.01% and 1%, most preferably it is between 0.2% and
0.6%.
[0068] Preferably, the pH of the aqueous phase is 3 to 10, more
preferably, 4 to 8, most preferably, 5 to 7.
[0069] Also part of the first aspect of the invention is a process
for preparing a coating composition which comprises the steps of
[0070] (i) providing the rheology modifiers of the first aspect of
the present invention, [0071] (ii) optionally forming an aqueous
solution or inverse (water-in-oil) emulsion of the theology
modifiers of the first aspect of the present invention, and [0072]
(iii) mixing the rheology modifiers of step (i) or the aqueous
solution or inverse emulsion of the rheology modifiers obtained in
step (ii) with a binder, a pigment, a carrier solvent and optional
additives in order to form a coating composition.
[0073] Preferably, the rheology modifiers of step (i) is mixed with
a binder, a pigment, a carrier solvent and optional additives in
order to form a coating composition.
[0074] Any suitable binder or binder mixtures can be used. Examples
of binders are styrene-butadiene (SB) copolymer, styrene-acrylate
(SA) copolymer, styrene-butadiene-acrylonitrile copolymer,
styrene-acrylate-acrylonitrile copolymer,
styrene-butadiene-acrylate-acrylonitrile copolymer, styrene-maleic
anhydride copolymer, styrene-acrylate-maleic anhydride copolymer,
polysaccharides, proteins, polyvinyl pyrrolidone, polyvinyl
alcohol, polyvinyl acetate, natural polymers such as starch,
cellulose or protein and cellulose derivatives such as
carboxymethylcellulose (CMC).
[0075] Preferred binders are styrene-butadiene (SB) copolymer,
styrene-acrylate (SA) copolymer and polyvinyl alcohol and mixtures
thereof.
[0076] Any suitable pigment or pigment mixture can be used.
Examples of pigments are clay (or kaolin), calcined clay (or
kaolin), ground calcium carbonate (GCC), precipitated calcium
carbonate (PCC), titanium dioxide, satin white, zinc oxide, barium
sulfate, gypsum, silica, alumina trihydrate, talc, mica and
diatomaceous earth.
[0077] An example of a carrier solvent is water. The binder and/or
the pigment can be employed as aqueous solutions or dispersions,
e.g. the binder may be employed as latex, so that the addition of
further water may not be necessary.
[0078] Examples of optional additives are optical brighteners,
surfactants, dispersants, blocides, defoamers, lubricants,
crosslinkers (also called insolubilisers), additional rheology
modifiers, water retention agents and dyes.
[0079] An example of an optical brightener is
diaminostilbenedisulfonic acid as sold for example under the
tradename CIBA.RTM. TINOPAL.RTM. UP (CIBA.RTM.,
diaminostilbenedisulfonic acid). An example of a surfactant is
sodium dialkysulphosuccinate as sold for example under the
tradename AEROSOL.RTM. OT (CYTEC.RTM., sodium
dialkylsulphosuccinate), or alkoxylated fatty acids as sold for
example under the tradename INVADINE.RTM. PF (CIBA.RTM.,
alkoxylated fatty acids). Examples of dispersants are sodium salts
of acrylic polymers, as sold for example under the tradename
DISPEX.RTM. N40 (CIBA.RTM., sodium salt of an acrylic polymer in
water). An example of a biocide is glutaraldehyde as sold for
example under the tradename PRIOR.TM. 850 (glutaraldehyde).
Examples of defoamers are polyether derivatives of aliphatic
alcohols as sold for example under the tradename AFRANIL.degree. F.
(polyether derivatives of aliphatic alcohols). An example of a
lubricant is calcium stearate as sold for example under the
tradename CIBA.RTM. RAISACOAT.RTM. CAS50 (calcium stearate). An
example of a crosslinker is ammonium zirconium carbonate as sold
for example under the tradename CIBA.RTM. RAISACOAT.RTM. AZ20
(ammonium zirconium carbonate). Examples of additional rheology
modifiers are xanthan gum, methycellulose, hydroxypropyl
methylcellulose, or acrylic polymers such as sold for example under
the tradename CIBA.RTM. RHEOVIS.RTM. CTE 407 (acrylic polymers). An
example of a water retention agent is sodium alginate. Examples of
dyes are organic pigment dyes, respectively anionic direct dyes as
sold for example under the tradenames CIBA.RTM. IRGALITE.RTM.
(anionic direct dyes) and CIBA.RTM. PERGASOL.RTM. (anionic direct
dyes).
[0080] Preferably the pH of the coating composition is in the range
of 6.5 to 10.5, more preferably 7 to 10, most preferably 7.5 to
9.5.
[0081] The amount of solids in the coating composition can be 10 to
90%, preferably 20 to 80%, more preferably 30 to 70%, most
preferably 50 to 70%, by weight based on the weight of the
composition.
[0082] The amount of pigment can be from 1 to 90%, preferably from
20 to 80%, more preferably 30 to 70%, most preferably from 40 to
60% by weight based on the weight of the composition.
[0083] The amount of rheology modifier of the present invention can
be from 0.001 to 5, preferably from 0.01 to 3, more preferably from
0.05 to 1 dry weight parts per 100 dry weight parts pigment.
[0084] The amount of binder can be from 1 to 60, preferably from 3
to 30, more preferably from 10 to 20 dry weight parts per 100 dry
weight parts pigment.
[0085] The amount of optional other components can be from 0 to 10,
preferably from 0.5 to 4 dry weight parts per 100 dry weight parts
pigment.
[0086] Also part of the first aspect of the invention is a coating
composition obtainable by above process.
[0087] Another part of the first aspect of the present invention is
a process for coating a substrate comprising the steps of [0088]
(i) providing the rheology modifiers of the first aspect of the
present invention, [0089] (ii) optionally forming an aqueous
solution or inverse (water-in-oil) emulsion of the rheology
modifiers of the present invention, [0090] (iii) mixing the
rheology modifiers of step (i) or the aqueous solution or inverse
emulsion of the rheology modifiers obtained in step (ii) with a
binder, a pigment, a carrier solvent and optional additives in
order to form a coating composition, and [0091] (iv) applying the
coating composition obtained in step (ii) onto the substrate.
[0092] The substrate can be a sheet or any other three dimensional
object and it can have an even or uneven surface. The substrate can
be made from paper, cardboard, metal, wood, textiles, glass,
ceramics and/or polymers. Examples of polymers are polyethylene
terephthalate, low density-polyethylene, polypropylene, biaxially
orientated polypropylene, polyether sulfone, polyvinyl chloride
polyester and polystyrene. Preferably, the substrate is made from
paper, cardboard or polymer. More preferably, the substrate is
paper.
[0093] The coating composition can be applied by any suitable
method such as blade, roll, spray or curtain coating. Preferably
the coating composition is applied by curtain coating coating onto
the substrate.
[0094] Another part of the first aspect of the invention are
substrates coated by the above process.
[0095] Also part of the first aspect of the present invention is
the use of the rheology modifiers of the first aspect of the
present invention for coating operations, especially for curtain
coating operations.
[0096] Aqueous solutions of the rheology modifiers of the first
aspect of the present invention show a high "apparent extensional
viscosity" and a low "low shear viscosity" (synonymous to
Brookfield viscosity) when the concentration of the rheology
modifier is low and a low "apparent extensional viscosity" and a
high "low shear viscosity" (synonymous to Brookfield viscosity)
when the concentration of the rheology modifier is high. So,
depending on the concentration, these rheology modifiers can be
used for all kind of coating methods, such as blade, roll or
curtain coating.
[0097] The rheology modifiers of the first aspect of the present
invention have the advantages that they are solid polymer particles
and thus very stable, easy to handle and do not require a special
clean-up after use in order to avoid environmental problems. In
addition, they can be either used as solid particles or readily
dissolved in water just before use.
[0098] The mixtures of rheology modifiers of the second aspect of
the present invention comprise a first theology modifier, which is
a water-soluble polymer having a weight average molecular weight
(Mw) of at least 1,000,000 g/mol and an intrinsic viscosity of at
least 2.5 dl/g, both as determined by size exclusion
chromatography, and a second rheology modifier, which has a weight
average molecular weight of from 2,000 g/mol to 800,000 g/mol, as
determined by size exclusion chromatography.
[0099] Preferably, the first rheology modifier is a polymer having
a weight average molecular weight (Mw) of from 1,000,000 g/mol to
2,500,000 g/mol and an intrinsic viscosity of from 2.5 to 5.0 dl/g,
both as determined by size exclusion chromatography. More
preferably, the first rheology modifier is a polymer having a
weight average molecular weight (Mw) of from 1,000,000 g/mol to
1,500,000 g/mol, and an intrinsic viscosity of from 2.5 to 4.5
dVlg, both as determined by size exclusion chromatography.
[0100] Preferably, the first rheology modifier is a polymer
composed of monomer units derived from [0101] (i) at least one
monomer of formula I
[0101] ##STR00003## [0102] whereby [0103] R.sup.1 and R.sup.2 can
be the same or different and are hydrogen, C.sub.1-6-alkyl or
C.sub.5-8-cycloalkyl, [0104] or R.sup.1 and R.sup.2 can together
with the nitrogen to which they are attached form a heterocyclic 5-
or 6-membered ring, whereby C.sub.1-6-alkyl may be substituted with
amino, hydroxyl, halogen, C.sub.1-4-alkoxy, aryl or mono- or
diC.sub.1-4-alkylamino, and [0105] R.sup.3 and R.sup.4 can be the
same or different and are hydrogen, C.sub.1-6-alkyl,
C.sub.5-8-cycloalkyl, halogen, aryl or NHCOC.sub.1-4-alkyl, whereby
C.sub.1-4-alkyl may be substituted with amino, hydroxyl, halogen,
C.sub.1-4-alkoxy, aryl or mono- or diC.sub.1-4-alkylamino, and
[0106] (ii) optional other ethylenically unsaturated monomers.
[0107] Examples of C.sub.1-4-alkyl are methyl, ethyl, propyl,
isopropyl, butyl, sec-butyl, tert-butyl, and isobutyl. Examples of
C.sub.1-6-alkyl are methyl, ethyl, propyl, isopropyl, butyl,
sec-butyl, tert-butyl, isobutyl, pentyl and hexyl. Examples of
C.sub.5-8-cycloalkyl are cyclopentyl, cyclohexyl and cycloheptyl.
Examples of 5- or 7-membered heterocyclic rings are morpholino,
pyrrolidino and piperidino. Examples of aryl are phenyl and
substituted phenyl such as tolyl. Examples of halogen are bromine
and chlorine. Examples of C.sub.1-4-alkoxy are methoxy, ethoxy,
propoxy, Isopropoxy, butoxy, sec-butoxy, tert-butoxy and isobutoxy.
Examples of mono- or diC.sub.1-4-alkylamino are N-methylamino,
N,N-ethylmethylamino, N,N-diethylamino, N,N-dipropylamino,
N-isopropylamino and N,N-dibutylamino.
[0108] Examples of monomers of formula (I) are (meth)acrylamide,
N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide,
N-isopropyl(meth)acrylamide.
[0109] Preferably, R.sup.1 and R.sup.2 can be the same or different
and are hydrogen or C.sub.1-4-alkyl, whereby C.sub.1-4-alkyl may be
substituted with amino or mono- or diC.sub.1-4-alkylamino, and
[0110] R.sup.3 and R.sup.4 can be the same or different and are
hydrogen, C.sub.1-4-alkyl or NHCOC.sub.1-4-alkyl, whereby
C.sub.1-4-alkyl may be substituted with amino or mono- or
diC.sub.1-4-alkylamino.
[0111] More preferably, R.sup.1 and R.sup.2 can be the same or
different and are hydrogen or C.sub.1-4-alkyl, and R.sup.3 and
R.sup.4 can be the same or different and are hydrogen or
C.sub.1-4-alkyl.
[0112] Even more preferably, R.sup.1 and R.sup.2 are hydrogen, and
R.sup.3 and R.sup.4 are the same or different and are hydrogen or
C.sub.1-4-alkyl.
[0113] Most preferably, R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are
hydrogen.
[0114] Any suitable other ethylenically unsaturated monomer can be
used. Examples of other ethylenically unsaturated monomers are
acrylic monomers, styrene monomers, vinyl monomers, maleic monomers
and allyl monomers.
[0115] Examples of acrylic monomers are (meth)acrylic acid or salts
thereof, (meth)acrylamide, (meth)acrylonitrile, C.sub.1-6-alkyl
(meth)acrylates such as ethyl (meth)acrylate, butyl (meth)acrylate
or hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate,
di(C.sub.1-4-alkylamino)-C.sub.1-6-alkyl (meth)acrylates such as
dimethylaminoethyl acrylate or diethylaminoethyl acrylate, amides
formed from di(C.sub.1-4-alkylamino)C.sub.1-6-alkylamines and
(meth)acrylic acid and C.sub.1-4-alkyl halide adducts thereof.
[0116] Examples of styrene monomers are styrene, 4-methylstyrene
and 4-vinylbiphenyl. Examples of vinyl monomers are vinyl alcohol,
vinyl chloride, vinylidene chloride, vinyl isobutyl ether and vinyl
acetate. Examples of olefin monomers are ethylene, propylene,
butadiene and isoprene and chlorinated or fluorinated derivatives
thereof such as tetrafluoroethylene. Examples of maleic monomers
are maleic acid, maleic anhydride and maleimide. An example of an
allyl monomer is diallyldimethylammonium chloride.
[0117] Preferably, the optional other ethylenically unsaturated
monomers comprise at least one monomer of formula II
##STR00004##
whereby
[0118] R.sup.5 and R.sup.6 can be the same or different and are
hydrogen, C.sub.1-6-alkyl, C.sub.5-8-cycloalkyl, halogen, aryl or
NHCOC.sub.1-4-alkyl, whereby C.sub.1-6-alkyl may be substituted
with amino, hydroxyl, halogen, C.sub.1-4-alkoxy, aryl or mono- or
diC.sub.1-4-alkylamino, and
[0119] M is hydrogen, ammonium, mono-, di-, tri- or
tetraC.sub.1-4-alkylammonium, alkali metal or earth alkaline
metal.
[0120] Examples of mono-, di-, tri- or tetraC.sub.1-4-alkylammonium
are N-ethylammonium, N,N-diethyl-ammonium and
N,N,N-tributylammonium. Examples of alkali metals are sodium,
potassium and lithium. Examples of earth alkaline metals are
magnesium and calcium.
[0121] Examples of monomers of formula (II) are (meth)acrylic acid,
ammonium (meth)acrylate, sodium (meth)acrylate.
[0122] Preferably, R.sup.5 and R.sup.6 can be the same or different
and are hydrogen, C.sub.1-4-alkyl or NHCOC.sub.1-4-alkyl, and M is
hydrogen, ammonium, mono-, di-, tri- or
tetraC.sub.1-4-alkylammonium, alkali metal or earth alkaline
metal.
[0123] More preferably, R.sup.5 and R.sup.6 are the same or
different and are hydrogen or C.sub.1-4-alkyl, and M is hydrogen,
ammonium, or alkali metal. Most preferably, R.sup.5 and R.sup.6 are
hydrogen, and M is hydrogen, ammonium, or alkali metal.
[0124] Preferably, the polymers are obtainable by polymerisation of
at least one monomer of formula (I) and at least one monomer of
formula (II).
[0125] Preferably the molar ratio of monomers of formula
(I)/monomers of formula (II) is from 90:1 to 1:90, more preferably
it is from 10:1 to 1:10, even more preferably, it is from 5:1 to
1:5, and most preferably it is from 1:1 to 1:5.
[0126] Preferably, the second rheology modifier has a weight
average molecular weight of from 2,000 g/mol to 500,000 g/mol, more
preferably, from 10,000 to 250,000 g/mol, most preferably from
50,000 to 150,000 g/mol.
[0127] The second rheology modifier is preferably prepared from a
monomer mixture comprising at least one acrylic monomer. In
particular, it is formed from a monomer mixture comprising an
acidic acrylic monomer and a monomer having a hydrophobic side
chain. Examples of acidic acrylic monomers are acrylic acid and
methacrylic acid. Examples of monomers having a hydrophobic side
chain are steareth 10 mole ethoxylate allyl ether and steareth 25
mole ethoxylate methacrylate. Preferably, the monomer mixture
comprises from 10 to 90%, more preferably from 20 to 80%, most
preferably from 30 to 70% by weight of the acidic acrylic monomer
based on the weight of all monomers. Preferably, the monomer
mixture comprises from 0.01 to 40%, more preferably from 0.01 to
30%, most preferably from 0.01 to 20% by weight of the monomer
having at least one hydrophobic side chain based on the weight of
all monomers. A particular preferred second rheology modifier is
prepared from ethyl acrylate/methacrylic acid/steareth 10 mole
ethoxylate allyl ether in a weight ratio of 50/40/10.
[0128] Also part of the second aspect of the invention is a process
for preparing a coating composition which comprises the steps of
[0129] (i) providing the mixture of rheology modifiers of the
second aspect of the present invention, [0130] (ii) mixing the
mixture of rheology modifiers of step (I) with a binder, a pigment,
a carrier solvent and optional additives in order to form a coating
composition.
[0131] The examples of binders, pigments, carrier solvents and
optional additives given for the first aspect of the invention
apply also here.
[0132] Preferably the pH of the coating composition is in the range
of 6.5 to 10.5, more preferably 7 to 10, most preferably 7.5 to
9.5.
[0133] The amount of solids in the coating composition can be 20 to
95%, preferably 30 to 90%, more preferably 40 to 85%, most
preferably 60 to 80%, by weight based on the weight of the
composition.
[0134] The amount of pigment can be from 1 to 90%, preferably from
can be 20 to 95%, preferably 30 to 90%, more preferably 40 to 85%,
most preferably 60 to 80%, by weight based on the weight of the
composition.
[0135] The amount of the first rheology modifier of the mixture of
rheology modifiers of the second aspect of the invention can be
from 0.001 to 5, preferably from 0.01 to 3, more preferably from
0.03 to 0.5 dry weight parts per 100 dry weight parts pigment.
[0136] The amount of the second rheology modifier of the mixture of
rheology modifiers of the second aspect of the invention can be
from 0.001 to 5, preferably from 0.01 to 3, more preferably from
0.03 to 0.5 dry weight parts per 100 dry weight parts pigment.
[0137] The amount of binder can be from 1 to 60, preferably from 3
to 30, more preferably from 5 to 15 dry weight parts per 100 dry
weight parts pigment.
[0138] The amount of optional other components can be from 0 to 10,
preferably from 0.5 to 4 dry weight parts per 100 dry weight parts
pigment.
[0139] Also part of the second aspect of the invention is a coating
composition obtainable by above process.
[0140] Another part of the second aspect of the present invention
is a process for coating a substrate comprising the steps of [0141]
(i) providing the mixture of rheology modifiers of the second
aspect of the present invention, [0142] (ii) mixing the mixture of
rheology modifiers of step (i) with a binder, a pigment, a carrier
solvent and optional additives in order to form a coating
composition, and [0143] (iii) applying the coating composition
obtained in step (ii) onto the substrate.
[0144] The examples for a substrate given for the first aspect of
the invention apply accordingly to the second aspect of the
invention.
[0145] Another part of the second aspect of the invention are
substrates coated by the above process.
[0146] Also part of the second aspect of the present invention is
the use of the rheology modifiers of the present invention for
coating operations, especially for blade coating operations.
[0147] Another part of the second aspect of the present invention
is a method for reducing white pitch in the production of coated
paper comprising the step of coating the paper with a coating
composition comprising the mixture of rheology modifiers of the
second aspect of the present invention.
[0148] An advantage of the mixture of rheology modifiers of the
second aspect of the present invention is that in processes for
preparing paper, which involve blade coating operations and require
coating compositions of higher than usual low "apparent high shear
viscosity" only a reduced amount of polyvinyl alcohol is required
to achieve the desired coating composition of higher than usual low
"apparent high shear viscosity". Thus, when recycling paper coated
with these composition, the formation of "white pitch" caused by
the presence of polyvinyl alcohol in the wet end is reduced.
EXAMPLES
Example 1
Preparation of a Rheology Modifier of the First Aspect of the
Invention
[0149] A 25% by weight solution of stearyl methacrylate:methacrylic
acid copolymer in (3.6 g) EXXSOL.TM. D40 FLUID (EXXONMOBIL.RTM.,
light hydrotreated petroleum distillates) is dissolved in
EXXSOL.TM. D40 FLUID (EXXONMOBIL.RTM., light hydrotreated petroleum
distillates), a hydrocarbon solvent, (300 g) and the obtained
solution is sparged with nitrogen for 30 minutes. A monomer
solution is prepared by dissolving acrylamide (81 g, 1.14 mol) and
a 1% by weight aqueous solution of ethylenediaminetetraacetic acid
(5.4 g) in water (93.6 g) and adjusting the pH to 6.0. A 10% by
weight aqueous solution of sodium hypophosphite (0.9 mL), a 2% by
weight solution of 2,2'-azobis(2-amidinopropane)dihydrochloride
(1.8 mL) and a 1% aqueous solution of sodium sulfite (1.8 mL) are
added to the monomer solution. The thus obtained solution is added
to the sparged hydrocarbon solvent and a nitrogen atmosphere is
maintained. The stirrer speed is adjusted to give droplets of
approximately 250 .mu.m. A 1% by weight aqueous solution of
tert-butyl hydroperoxide (0.9 mL) is added to the mixture to start
the polymerization. The polymerization is allowed to exotherm.
After polymerization, water is removed by distillation. After
cooling the polymer beads are separated by filtration and dried to
remove residual solvent at 40.degree. C. The obtained polymer beads
(100% of the monomer units derived from acrylamide) have an average
diameter of 250 .mu.m.
Comparative Example 1
Preparation of a Comparative Rheology Modifier
[0150] Polymer beads are prepared as described in example 1, except
that the amount of the 10% by weight aqueous solution of sodium
hypophosphite is 1.8 mL. The obtained polymer beads (100% of the
monomer units derived from acrylamide) have an average diameter of
250 .mu.m.
Comparative Example 2
Preparation of a Comparative Rheology Modifier
[0151] Polymer beads are prepared as described in example 1, except
that the amount of the 10% by weight aqueous solution of sodium
hypophosphite is 3.6 mL. The obtained polymer beads (100% of the
monomer units derived from acrylamide) have an average diameter of
250 .mu.m.
Example 2
Preparation of a Rheology Modifier of the First Aspect of the
Invention
[0152] Polymer beads are prepared as described in example 1, except
that the monomer solution is prepared by dissolving acrylamide
(56.7 g, 0.8 mol), acrylic acid (18.6 g, 0.26 mol), sodium
hydroxide (10.3 g) and a 1% by weight aqueous solution of
ethylenediaminetetraacetic acid (5.4 g) in water (93.6 g) and
adjusting the pH to 6.0. The obtained polymer beads (75% of the
monomer units are derived from acrylamide and 25% from sodium
acrylate) have an average diameter of 250 .mu.m.
Example 3
Preparation of a Rheology Modifier of the First Aspect of the
Invention
[0153] Polymer beads are prepared as described in example 2, except
that the amount of the 10% by weight aqueous solution of sodium
hypophosphite is 1.8 mL. The obtained polymer beads (75% of the
monomer units are derived from acrylamide and 25% from acrylic
acid) have an average diameter of 250 .mu.m.
Comparative Example 3
Preparation of a Comparative Rheology Modifier
[0154] Polymer beads are prepared as described in example 2, except
that the amount of the 10% by weight aqueous solution of sodium
hypophosphite is 3.6 mL. The obtained polymer beads (75% of the
monomer units are derived from acrylamide and 25% from acrylic
acid) have an average diameter of 250 .mu.m.
Example 4
Preparation of a Rheology Modifier of the First Aspect of the
Invention
[0155] Polymer beads are prepared as described in example 1, except
that the monomer solution is prepared by dissolving acrylamide
(14.4 g, 0.2 mol), acrylic acid (44.1 g, 0.61 mol), sodium
hydroxide (24.5 g) and a 1% by weight aqueous solution of
ethylenediaminetetraacetic acid (5.4 g) in water (91.6 g) and
adjusting the pH to 6.0. The obtained polymer beads (25% of the
monomer units are derived from acrylamide and 75% from sodium
acrylate) have an average diameter of 250 .mu.m.
Example 5
Preparation of a Rheology Modifier of the First Aspect of the
Invention
[0156] Polymer beads are prepared as described in example 4, except
that the amount of the 10% by weight aqueous solution of sodium
hypophosphite is 1.8 mL. The obtained polymer beads (25% of the
monomer units are derived from acrylamide and 75% from acrylic
acid) have an average diameter of 250 .mu.m.
Example 6
Preparation of a Rheology Modifier of the First Aspect of the
Invention
[0157] Polymer beads are prepared as described in example 4, except
that the amount of the 10% by weight aqueous solution of sodium
hypophosphite is 3.6 mL. The obtained polymer beads (25% of the
monomer units are derived from acrylamide and 75% from acrylic
acid) have an average diameter of 250 .mu.m.
Determination of the Number Average Molecular Weight (Mn). The
Weight Average Molecular Weight (Mw) and the Intrinsic Viscosity
(IV) of the Rheology Modifiers of Examples 1 to 6, and Comparative
Examples 1 to 3
[0158] The number average molecular weight (Mn), the weight average
molecular weight (Mw) and the intrinsic viscosity (IV) are
determined by size exclusion chromatography (detector: VISCOTEC.TM.
TDA (three detector array) (refractive index-, viscometer- and RALS
(90.degree.)/LALS (7.degree.) light scattering detector); column:
2.times.VISCOGEL.RTM. GMPWXL (size exclusion column)+precolumn;
pump: VISCOTEC.RTM. VE 20002 GPC (eluent/sample module); eluent:
0.2 M sodium nitrate, 0.8 mL/min; temperature: 35.degree. C.
(columns+detectors); calibration: narrow polyethylene oxide
standard).
TABLE-US-00001 TABLE 1 Polydispersity IV Rheology modifier Mn
[g/mol] Mw [g/mol] (Mw/Mn) [dl/g] Rheology modifiers wherein 100%
of the monomer units derived from acrylamide example 1 823,000
1,290,000 1.57 3.11 comp. example 1 365,000 813,000 2.22 2.45 comp.
example 2 226,000 596,000 2.64 1.71 Rheology modifiers wherein 75%
of the monomer units are derived from acrylamide and 25% from
sodium acrylate example 2 1,417,000 2,002,000 1.41 3.90 example 3
680,000 1,113,000 1.63 3.20 comp. example 3 324,000 657,000 2.03
2.49 Rheology modifiers wherein 25% of the monomer units are
derived from acrylamide and 75% from sodium acrylate example 4
1,741,000 2,551,000 1.47 5.78 example 5 1,689,000 2,134,000 1.26
4.38 example 6 873,000 1,238,000 1.42 4.16
Determination of the "Low Shear Viscosity" of Aqueous Solutions of
the Rheology Modifiers of Examples 1 to 6, and Comparative Examples
1 to 3
[0159] The "low shear viscosity" of aqueous solutions of polymer
beads at 30 g, 60 g and 90 g, respectively, beads per litre water
is measured using a BROOKFIELD.RTM. viscometer (100 rpm and
25.degree. C.).
[0160] The results are shown in FIG. 1.
[0161] One can see that the rheology modifiers of examples 1 to 6
show "low shear viscosities", which are comparable to the "low
shear viscosities" of the rheology modifiers obtained in
comparative examples 1 to 3.
Determination of the "Apparent Extensional Viscosity" of Aqueous
Solutions of the Rheology Modifiers of Examples 1 to 6, and
Comparative Examples 1 to 3
[0162] The "normalized diameter" of aqueous solutions of the
polymer beads at 30 g beads per litre water is measured using a
CaBER.TM. 1 instrument (extensional rheometer), which is an
extensional rheometer sold by Thermo Haake (plates diameter 6 mm;
start height 2.5 mm; end height 7.85 mm; hencky strain 1.14). The
normalized diameter is the filament diameter (as a function of
time)/initial filament diameter. The break-up time, i.e. the time
at which the normalized diameter is 0, is related to the apparent
extensional viscosity. The higher the break-up time, the higher is
the "apparent extensional viscosity".
[0163] The results are shown in FIGS. 2 and 3.
[0164] One can see that the rheology modifiers of examples 1 to 6
show "apparent extensional viscosities", which are considerable
higher than the "apparent extensional viscosities" of the rheology
modifiers obtained in comparative examples 1 to 3. Among the
rheology modifiers of examples 1 to 6, the rheology modifiers of
examples 2, 4 and 5 yield the highest "apparent extensional
viscosities". The highest "apparent extensional viscosity" is
obtained with the rheology modifier of example 4.
Example 7
Preparation of Coating Compositions, Suitable for Curtain Coating
Operations, Containing the Rheology Modifiers of Examples 1 to
6
[0165] The rheology modifiers obtained in examples 1 to 6 are
dissolved in water at 30 g beads per litre of water, and varying
amounts (0.5 to 0.2 dry weight parts of polymer beads) of these
solutions are added to a mixture of 100 dry weight parts ground
calcium carbonate, and 17.5 dry weight parts of CIBA.RTM.
LATEXIA.RTM. 301 (styrene butadiene latex) in water to give a
coating composition having a solid content of 60% by weight based
on the weight of the composition. The pH is adjusted to 9.0.
Comparative Example 4
Preparation of a Coating Composition, Suitable for Curtain Coating
Operations, Containing STEROCOLL.RTM. BL (Acrylamide/Acrylic Acid
Copolymers Having a Mw of about 10,000,000) as Rheology
Modifier
[0166] 0.1 dry weight parts STEROCOLL.RTM. BL (acrylamide/acrylic
acid copolymers having a Mw of about 10,000,000), an inverse
(water-in-oil) emulsion of a rheology modifier, is added to a
mixture of 100 dry weight parts ground calcium carbonate, and 17.5
dry weight parts DL 936, a styrene butadlene latex, in water to
give a coating composition having a solid content of 60% by weight
based on the weight of the composition. The pH is adjusted to
9.0.
Comparative Example 5
Preparation of a Coating Composition Suitable for Curtain Coating
Operations, Containing STEROCOLL.degree. BL (Acrylamide/Acrylic
Acid Copolymers Having a Mw of about 10,000,000) as Rheology
Modifier
[0167] 0.1 dry weight parts STEROCOLL.RTM. BL (acrylamide/acrylic
acid copolymers having a Mw of about 10,000,000), an inverse
(water-in-oil) emulsion of a rheology modifier, is added to a
mixture of 100 dry weight parts ground calcium carbonate, and 17.5
dry weight parts of CIBA.RTM. LATEXIA.RTM. 301 (styrene butadiene
latex) in water to give a coating composition having a solid
content of 60% by weight based on the weight of the composition.
The pH is adjusted to 9.0.
Determination of "Low Shear Viscosity" of the Coating Compositions
of Example 7 and Comparative Examples 4 and 5
[0168] The low shear viscosities of the coating compositions are
measured using a Brookfield viscometer (100 rpm and 25.degree.
C.).
TABLE-US-00002 TABLE 2 Low Shear Viscosity [mPa .times. s] Amount
Rheology modifier [dry weight parts/ Coating Rheology 100 dry
weight parts calcium carbonate] composition modifier 0.04 0.06 0.08
0.1 0.2 example 7 example 1 76 86 128 example 2 102 128 250 example
3 98 118 212 example 4 134 184 188 example 5 132 156 188 example 6
124 138 160 comp. example 4 STEROCOLL .RTM. BL 152 comp. example 5
STEROCOLL .RTM. BL 164
[0169] One can see that "low shear viscosities" comparable to those
of the coating compositions containing STEROCOLL.RTM. BL
(acrylamide/acrylic acid copolymers having a Mw of about
10,000,000) (comparative examples 4 and 5) can be achieved with the
coating compositions of example 7 containing the rheology modifiers
of examples 1 to 6. The rheology modifiers of examples 4, 5 or 6
even yield coating compositions of comparable "low shear
viscosities" at lower dosages compared to STEROCOLL.RTM. BL
(acrylamide/acrylic acid copolymers having a Mw of about
10,000,000).
Determination of Water Retention Properties of the Coating
Compositions of Example 7 and Comparative Examples 4 and 5 Using
Paper as Substrate
[0170] Water retention properties (g released water/m.sup.2 base
paper) of the coating compositions are measured following test
method TAPPI T 701 pm-01 using an AA GWR water retention meter by
determining the amount of continuous phase removed through a
membrane filter (non-hydroscopic polycarbonate filter with 5 .mu.m
mean pore size) from the coating into base paper (chromatography
paper with basis weight 413 g/m.sup.2) within 2 minutes und under
hydrostatic pressure of 2 bars.
[0171] The measurement is performed on those coating compositions
of example 7 having comparable "low shear viscosities" to the
coating composition of comparative example 5,
TABLE-US-00003 TABLE 3 Amount Rheology modifier [dry weight parts/
Water Coating Rheology 100 dry weight loss composition. modifier
parts calcium carbonate] [g/m.sup.2] example 7 example 1 0.2 203
example 2 0.08 224 example 3 0.08 231 example 4 0.06 200 example 5
0.06 207 example 6 0.08 207 Comp. STEROCOLL .RTM. BL 0.1 191
example 5
[0172] The lower the "water loss" value, the higher is the water
retention. One can see that the water retention properties of the
coating compositions of example 7 containing the rheology modifiers
of examples 1 to 6, are comparable to those of the coating
composition containing STEROCOLL.RTM. BL (acrylamide/acrylic acid
copolymers having a Mw of about 10,000,000) (comparative example
5). Among the rheology modifiers of examples 1 to 6, the rheology
modifier of example 4 yields the best water retention
properties.
[0173] It was not possible to measure the apparent extensional
viscosities of the coating compositions due to irreproducible
results.
Example 8
Preparation of a Second Rheology Modifier of the Mixture of
Rheology Modifiers of the Second Aspect of the Invention
[0174] An aqueous emulsion polymer composed of ethyl
acrylate/methacrylic acid/steareth 10 mole ethoxylate allyl ether
in a weight ratio of 50/40/10 is prepared in analogy to example 1
of WO 04/076743.
Examples 9 to 12
Preparation of Coating Compositions, Suitable for Blade Coating
Operations, Containing a Mixture of the Rheology Modifiers of
Example 1 or 2 and the Rheology Modifier of Example 8 as Second
Rheology Modifier
[0175] Following coating compositions having a pH of 9.0 and
various solid contents (68.0 to 69.6% by weight) are prepared.
TABLE-US-00004 TABLE 5 Amount of Ingredients [dry weight parts]
Example No Ingredients 9 10 11 12 Calcium carbonate 100 100 100 100
Polyvinyl alcohol 4/98 0.6 0.6 0.6 0.6 CIBA .RTM. LATEXIA .RTM. 204
7.5 7.5 7.5 7.5 CIBA .RTM. RAISACOAT .RTM. CAS50 0.5 0.5 0.5 0.5
CIBA .RTM. TINOPAL .RTM. ABPZ liq 0.5 0.5 0.5 0.5 Rheology modifier
example 1 0.1 0.08 Rheology modifier example 2 0.08 0.06 Rheology
modifier example 8 0.06 0.08 0.05 0.06 CIBA .RTM. LATEXIA .RTM. 204
is a styrene acrylate latex, CIBA .RTM. RAISACOAT .RTM. CAS50 is a
calcium stearate dispersion, CIBA .RTM. TINOPAL .RTM. ABPZ liq is
diaminostilbenetetrasulfonic acid.
Determination of "Apparent High Shear Viscosities of the Coating
Compositions of Examples 9 to 12
[0176] The "apparent high shear viscosities" of the coating
compositions having a solid content of 68.5% by weight are measured
using an ACAV A4 viscometer.
[0177] The "apparent high shear viscosities" are shown in FIG.
4.
[0178] The coating compositions of examples 9 to 11 containing the
rheology modifiers of examples 1 or 2 and the rheology modifier of
example 7 as second rheology modifier and only 0.6 dry weight parts
of polyvinyl alcohol, yield higher than usual "apparent high shear
viscosities". A particular higher than usual "apparent high shear
viscosity" is obtained with the coating composition of example 9
containing 0.1 dry weight parts of the rheology modifier of example
1 and 0.06 dry weight parts of the rheology modifier of example 8
as additional rheology modifier, followed by the coating
composition of example 10.
Determination of the Water Retention Properties of Coating
Compositions of Examples 9 to 12
[0179] The water retention properties are determined as described
for the coating compositions of example 7 and comparative examples
4 and 5.
[0180] The water retention properties are shown in FIG. 5.
* * * * *