U.S. patent application number 10/553075 was filed with the patent office on 2006-08-31 for method for the treatment of paper surfaces.
Invention is credited to Hubertus Kroner, Harm Wiese.
Application Number | 20060191653 10/553075 |
Document ID | / |
Family ID | 33154309 |
Filed Date | 2006-08-31 |
United States Patent
Application |
20060191653 |
Kind Code |
A1 |
Wiese; Harm ; et
al. |
August 31, 2006 |
Method for the treatment of paper surfaces
Abstract
A method for the treatment of paper surfaces is described.
Inventors: |
Wiese; Harm; (Heidelberg,
DE) ; Kroner; Hubertus; (Neustadt, DE) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Family ID: |
33154309 |
Appl. No.: |
10/553075 |
Filed: |
April 14, 2004 |
PCT Filed: |
April 14, 2004 |
PCT NO: |
PCT/EP04/03956 |
371 Date: |
October 12, 2005 |
Current U.S.
Class: |
162/135 ;
162/164.1; 162/168.1; 162/181.1; 162/181.2; 162/181.8 |
Current CPC
Class: |
D21H 19/56 20130101;
B23Q 39/026 20130101; B25J 15/0052 20130101; D21H 19/42 20130101;
B41M 5/5218 20130101; B41M 5/5254 20130101; D21H 21/52 20130101;
B41M 5/52 20130101 |
Class at
Publication: |
162/135 ;
162/164.1; 162/181.1; 162/168.1; 162/181.2; 162/181.8 |
International
Class: |
D21H 19/42 20060101
D21H019/42; D21H 21/52 20060101 D21H021/52 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 17, 2003 |
DE |
203-06-257.4 |
Claims
1. A process for the treatment of paper surfaces, wherein the
surface of the paper is coated with particles (composite particles)
which are composed of polymer and finely divided inorganic solid,
the weight average particle size of the finely divided inorganic
solid being .ltoreq.100 nm.
2. The process as claimed in claim 1, wherein the composite
particles are applied in the form of an aqueous composite particle
dispersion to the paper.
3. The process as claimed in claim 2, wherein the aqueous composite
particle dispersion was prepared by a process in which at least one
ethylenically unsaturated monomer is dispersed in an aqueous medium
and polymerized by means of at least one free radical
polymerization initiator in the presence of at least one dispersed,
finely divided inorganic solid and at least one dispersant by the
aqueous free radical emulsion polymerization method, a) a stable
aqueous dispersion of the at least one inorganic solid being used,
which dispersion, with an initial solids concentration of
.gtoreq.1% by weight, based on the aqueous dispersion of the at
least one inorganic solid, still contains more than 90% by weight
of the originally dispersed solid in dispersed form one hour after
its preparation and whose dispersed solid particles have a weight
average diameter of .ltoreq.100 nm, b) the disperse solid particles
of the at least one inorganic solid having an electrophoretic
mobility which differs from zero in an aqueous standard potassium
chloride solution at a pH which corresponds to the pH of the
aqueous dispersing medium before the beginning of the addition of
the dispersants, c) at least one anionic, cationic and nonionic
dispersant being added to the aqueous solid particle dispersion
before the beginning of the addition of the at least one
ethylenically unsaturated monomer, d) thereafter from 0.01 to 30%
by weight of the total amount of the at least one monomer being
added to the aqueous solid particle dispersion and being
polymerized to a conversion of at least 90% and e) the remaining
amount of the at least one monomer then being added continuously
under polymerization conditions at the rate at which it is
consumed.
4. A process for the treatment of paper surfaces, wherein the
surface of the paper is treated with an aqueous dispersion which is
obtained by mixing an aqueous polymer dispersion with at least one
dispersed, finely divided inorganic solid which has a weight
average particle diameter of .ltoreq.100 nm.
5. The process as claimed in claim 1, wherein the amount of
composite particles or of a mixture of dispersion polymer and
finely divided inorganic solid is from 0.1 to 100 g/m.sup.2 of
paper.
6. The process as claimed in claim 1, wherein the polymer can be
formed into a film.
7. The process as claimed in claim 1, wherein the paper used is a
base paper.
8. The process as claimed in claim 1, wherein the paper used is a
coated or sized paper.
9. The process as claimed in claim 1, wherein the finely divided
inorganic solid is at least one selected from the group consisting
of silica, alumina, hydrated aluminum oxide, calcium carbonate,
magnesium carbonate, calcium orthophosphate, magnesium
orthophosphate, iron(II) oxide, iron(III) oxide, iron(II/III)
oxide, tin oxide, cerium dioxide, yttrium(III) oxide, titanium
dioxide, hydroxyapatite, zinc oxide and zinc sulfide.
10. The process as claimed in claim 1, wherein the treated paper is
subjected to pressures and/or temperatures such that the polymer
forms a film.
11. A paper obtained by the process as claimed in claim 1.
12. A method of printing paper in the offset, flexographic and
gravure printing process comprising utilizing the paper as claimed
in claim 11.
13. A printed paper obtained by the method as claimed in claim
12.
14. A method of coating paper comprising utilizing an aqueous
dispersion of particles which are composed of polymer and finely
divided inorganic solid, the weight average particle size of the
finely divided inorganic solid being .ltoreq.100 nm.
15. A method of coating paper comprising utilizing an aqueous
dispersion which is obtained by mixing an aqueous polymer
dispersion with at least one dispersed, finely divided inorganic
solid which has a weight average particle diameter of .ltoreq.100
nm for the coating of paper.
16. The process as claimed in claim 4, wherein the amount of
composite particles or of a mixture of dispersion polymer and
finely divided inorganic solid is from 0.1 to 100 g/m.sup.2 of
paper.
17. The process as claimed in claim 4, wherein the polymer can be
formed into a film.
18. The process as claimed in claim 4, wherein the paper used is a
base paper.
19. The process as claimed in claim 4, wherein the paper used is a
coated or sized paper.
20. The process as claimed in claim 4, wherein the finely divided
inorganic solid is at least one selected from the group consisting
of silica, alumina, hydrated aluminum oxide, calcium carbonate,
magnesium carbonate, calcium orthophosphate, magnesium
orthophosphate, iron(II) oxide, iron(III) oxide, iron(II/III)
oxide, tin oxide, cerium dioxide, yttrium(III) oxide, titanium
dioxide, hydroxyapatite, zinc oxide and zinc sulfide.
21. The process as claimed in claim 4, wherein the treated paper is
subjected to pressures and/or temperatures such that the polymer
forms a film.
22. A paper obtained by a process as claimed in claim 4.
23. A method of printing paper in the offset, flexographic and
gravure printing process comprising utilizing the paper as claimed
in claim 22.
24. A printed paper obtained by the method as claimed in claim 23.
Description
[0001] The present invention relates to a process for the treatment
of paper surfaces, wherein the surface of the paper is coated with
particles (composite particles) which are composed of polymer and
finely divided inorganic solid, the weight average particle size of
the finely divided inorganic solid being .ltoreq.100 nm.
[0002] The present invention also relates to a process for the
treatment of paper surfaces, wherein the surface of the paper is
treated with an aqueous dispersion which is obtainable by mixing an
aqueous polymer dispersion with at least one dispersed, finely
divided inorganic solid which has a weight average particle
diameter of .ltoreq.100 nm.
[0003] Papers have a wide range of uses. Depending on their
intended use, the papers must be capable of being readily written
on or printed on (for example writing paper, newsprint, paper for
journals, catalogs, books, etc.), must be absorbable (for example
tissues, napkins, kitchen crepe paper and papers in the hygiene
sector) or must be very strong, as, for example, in the case of
banknote paper, Bible paper, kraft paper, capacitor paper or
photographic paper.
[0004] Particularly in the case of the papers which can be written
on and printed on and in the case of the very strong papers, the
paper surfaces are frequently subjected to additional treatment
steps for achieving the required properties. In particular, the
paper surfaces are coated with paper coating slips or treated with
paper sizes.
[0005] Paper coating slips substantially comprise a polymeric
binder, one or more pigments and various further assistants.
Through coating with paper coating slips, base papers acquire a
strong, smooth white surface having improved printability.
[0006] The binders used in the paper coating slips are usually
acrylate or styrene/butadiene copolymers. Corresponding paper
coating slips are described, for example, in WO 97/00776, EP-A
1101425 or EP-A 1132521.
[0007] The paper sizes are as a rule nonpigmented binders, for
example starches, proteins, rosin sizes and aqueous polymer
dispersions and in particular starch-containing aqueous polymer
dispersions, which are described, for example, in EP-A 307816, EP-A
735065, DE-A 3627494 and DE-A 10039388. As a result of the sizing,
in particular the fiber structure is consolidated and hence the
water resistance and the writability and printability are improved.
Furthermore, the pigment and fillers are better fixed.
[0008] It is an object of the present invention to provide a novel
process for the surface modification of paper.
[0009] We have found that this object is achieved by the processes
defined at the outset.
[0010] In the context of this document, paper is to be understood
as meaning a material which, according to DIN 6730 (August 1985),
is sheet-like and substantially comprises fibers of predominantly
vegetable origin and which is formed by draining a fiber suspension
containing various assistants on a wire, the fiber felt thus
obtained then being compacted and dried. Assistants used are, for
example, fillers, dyes, pigments, binders, optical brighteners,
retention aids, wetting agents, antifoams, preservatives, slime
control agents, plasticizers, antiblocking agents, antistatic
agents, water repellents, etc. known to a person skilled in the
art. Depending on the basis weight achieved for the sheet-like
material obtained, the term base paper (basis weight.ltoreq.225
g/m.sup.2) or raw board (basis weight>225 g/m.sup.2) is also
used. Another customary term is cardboard, which, with a basis
weight of from about 150 to 600 g/m.sup.2, comprises both base
paper grades and raw board grades. For reasons of simplicity, the
term base paper below includes base paper, raw board and
cardboard.
[0011] Frequently, the base paper is also treated by coating or is
converted into the ready-to-use form. Coating of paper is
understood as meaning the one-sided or two-sided coating of the
paper with an aqueous coating slip substantially comprising
pigments and binders. Depending on the type of coating slip, the
coat thickness to be achieved or the paper grade to be produced,
various coating methods are used for this purpose, for example the
roll coating, knife coating, air brush or cast coating methods
known to a person skilled in the art, which are followed in each
case by a drying step. The papers thus treated are referred to as
coated papers.
[0012] A further process for the treatment of papers comprises the
treatment of the paper surfaces with sizes. The papers thus treated
are referred to as sized papers.
[0013] The essential feature is that the novel processes are
suitable both for base papers and for coated and sized papers.
[0014] In one embodiment, the composite particles are applied in
the form of an aqueous composite particle dispersion to the paper
surface (process 1).
[0015] Aqueous dispersions of composite particles are generally
known. They are fluid systems which contain, as disperse phase
present in disperse distribution and in aqueous dispersing medium,
particles composed of a plurality of polymer balls consisting of
entangled polymer chains, i.e. the polymer matrix, and finely
divided inorganic solid. The diameter of the composite particles is
frequently from 30 to 5000 nm.
[0016] Composite particles and processes for their preparation in
the form of aqueous composite particle dispersions are known to a
person skilled in the art and are disclosed, for example, in U.S.
Pat. No. 3,544,500, U.S. Pat. No. 4,421,660, U.S. Pat. No.
4,608,401, U.S. Pat. No. 4,981,882, EP-A 104 498, EP-A 505 230,
EP-A 572 128, GB-A 2 227 739, WO 0118081, WO 0129106 and in Long et
al., Tianjin Daxue Xuebao 4 (1991),10 to 14, Bourgeat-Lami et al.,
Die Angewandte Makromolekulare Chemie 242 (1996), 105 to 122,
Paulke et al., Synthesis Studies of Paramagnetic Polystyrene Latex
Particles in Scientific and Clinical Applications of Magnetic
Carriers, pages 69 to 76, Plenum Press, New York, 1997, Armes et
al., Advanced Materials 11 No. 5 (1999), 408 to 410.
[0017] For example, aqueous composite particle dispersions which
were prepared according to the procedure disclosed in WO 03000760
are also suitable according to the invention. This process
comprises dispersing at least one ethylenically unsaturated monomer
in an aqueous medium and polymerizing by means of at least one free
radical polymerization initiator in the presence of at least one
dispersed, finely divided inorganic solid and at least one anionic,
cationic and nonionic dispersant by the aqueous free radical
emulsion polymerization method, [0018] a) a stable aqueous
dispersion of the at least one inorganic solid being used, which
dispersion, with an initial solids concentration of .gtoreq.1% by
weight, based on the aqueous dispersion of the at least one
inorganic solid, still contains more than 90% by weight of the
originally dispersed solid in dispersed form one hour after its
preparation and whose dispersed solid particles have a diameter of
.ltoreq.100 nm, [0019] b) the disperse solid particles of the at
least one inorganic solid having an electrophoretic mobility which
differs from zero in an aqueous standard potassium chloride
solution at a pH which corresponds to the pH of the aqueous
reaction medium before the beginning of the addition of the
dispersants, [0020] c) at least one anionic, cationic and nonionic
dispersant being added to the aqueous solid particle dispersion
before the beginning of the addition of the at least one
ethylenically unsaturated monomer, [0021] d) thereafter from 0.01
to 30% by weight of the total amount of the at least one monomer
being added to the aqueous solid particle dispersion and being
polymerized to a conversion of at least 90% and [0022] e) the
remaining amount of the at least one monomer then being added
continuously under polymerization conditions at the rate at which
it is consumed.
[0023] Suitable for this process are all those finely divided
inorganic solids which form stable aqueous dispersions which, with
an initial solids concentration of .gtoreq.1% by weight, based on
the aqueous dispersion of the at least one inorganic solid, still
contain more than 90% by weight of the originally dispersed solid
in dispersed form one hour after their preparation without stirring
or shaking and whose dispersed solid particles have a diameter of
.ltoreq.100 nm and moreover have an electrophoretic mobility
differing from zero at a pH which corresponds to the pH of the
aqueous reaction medium before the beginning of the addition of the
dispersants.
[0024] The quantitative determination of the initial solids
concentration and of the solids concentration after one hour and
the determination of the particle diameter are effected by the
analytical ultracentrifuge method (in this context, cf. S. E.
Harding et al., Analytical Ultracentrifugation in Biochemistry and
Polymer Science, Royal Society of Chemistry, Cambridge, Great
Britain 1992, Chapter 10, Analysis of Polymer Dispersions with an
Eight-Cell-AUC-Multiplexer: High Resolution Particle Size
Distribution and Density Gradient Techniques, W. Machtle, pages 147
to 175). The values stated in the case of the particle diameters
correspond to the d.sub.50 values.
[0025] The method for the determination of the electrophoretic
mobility is known to a person skilled in the art (cf. for example
R. J. Hunter, Introduction to Modem Colloid Science, Section 8.4,
pages 241 to 248, Oxford University Press, Oxford, 1993, and K. Oka
and K. Furusawa, in Electrical Phenomena at Interfaces, Surfactant
Science Series, Vol. 76, Section 8, pages 151 to 232, Marcel
Dekker, New York, 1998). The electrophoretic mobility of the solid
particles dispersed in aqueous reaction medium is determined by
means of a commercial electrophoresis apparatus, for example the
Zetasizer 3000 from Malvern Instruments Ltd., at 20.degree. C. and
1 bar (absolute). For this purpose, the aqueous solid particle
dispersion is diluted with a pH-neutral 10 millimolar (mM) aqueous
potassium chloride solution (standard potassium chloride solution)
until the solid particle concentration is from about 50 to 100
mg/l. The adjustment of the test sample to the pH which the aqueous
reaction medium has before the beginning of the addition of the
dispersants is effected by means of the conventional inorganic
acids, for example dilute hydrochloric acid or nitric acid, or
bases, for example dilute sodium hydroxide solution or potassium
hydroxide solution. The migration of the dispersed solid particles
in the electric field is detected by means of the electrophoretic
light scattering (cf. for example B. R. Ware and W. H. Flygare,
Chem. Phys. Lett. 12 (1971), 81 to 85). The sign of the
electrophoretic mobility is defined by the direction of migration
of the dispersed solid particles, i.e. the electrophoretic mobility
of the dispersed solid particles is positive if they migrate to the
cathode and, on the other hand, is negative if they migrate to the
anode.
[0026] A suitable parameter for influencing or adjusting the
electrophoretic mobility of dispersed solid particles in a certain
environment is the pH of the aqueous reaction medium. By
protonation or deprotonation of the dispersed solid particles, the
electrophoretic mobility is changed in the positive direction in
the acidic pH range (pH<7) and in the negative direction in the
alkaline range (pH>7). The pH range suitable for the process
disclosed in WO 03000760 is that within which a free radical
aqueous emulsion polymerization can be carried out. This pH range
is as a rule from pH 1 to 12, frequently from pH 1.5 to 11, often
from pH 2 to 10.
[0027] The pH of the aqueous reaction medium can be adjusted by
means of commercial acids, for example dilute hydrochloric, nitric
or sulfuric acid, or bases, for example dilute sodium hydroxide
solution or potassium hydroxide solution. It is frequently
advantageous if a portion or the total amount of the amount of acid
or base used for the pH adjustment is added to the aqueous reaction
medium before the at least one finely divided inorganic solid.
[0028] What is important for the process disclosed according to WO
033000760 is that, when, under the abovementioned pH conditions,
the dispersed solid particles [0029] have an electrophoretic
mobility with a negative sign, from 0.01 to 10, preferably from
0.05 to 5, particularly preferably from 0.1 to 3, parts by weight
of at least one cationic dispersant, from 0.01 to 100, preferably
from 0.05 to 50, particularly preferably from 0.1 to 20, parts by
weight of at least one nonionic dispersant and at least one anionic
dispersant are used per 100 parts by weight of the at least one
ethylenically unsaturated monomer, the amount of which anionic
dispersant being such that the ratio of the number of equivalents
of anionic dispersant to that of cationic dispersant is greater
than 1, or [0030] have an electrophoretic mobility with a positive
sign, from 0.01 to 10, preferably from 0.05 to 5, particularly
preferably from 0.1 to 3, parts by weight of at least one anionic
dispersant, from 0.01 to 100, preferably from 0.05 to 50,
particularly preferably from 0.01 to 20, parts by weight of at
least one nonionic dispersant and at least one cationic dispersant
are used per 100 parts by weight of the at least one ethylenically
unsaturated monomer, the amount of which cationic dispersant being
such that the ratio of the number of equivalents of cationic
dispersant to that of anionic dispersant is greater than 1.
[0031] The ratio of the number of equivalents of anionic dispersant
to that of cationic dispersant is understood as meaning the ratio
of the number of moles of the anionic dispersant, multiplied by the
number of anionic groups contained per mole of the anionic
dispersant, divided by the number of moles of the cationic
dispersant used, multiplied by the number of cationic groups
contained per mole of the cationic dispersant. The same applies to
the ratio of the number of equivalents of cationic dispersant to
that of anionic dispersant.
[0032] The total amount of the at least one anionic, cationic and
nonionic dispersant used according to WO 03000760 can be initially
taken in the aqueous solid dispersion. However, it is also possible
initially to take only a portion of said dispersants in the aqueous
solid dispersion and to add the remaining amounts continuously or
batchwise during the free radical emulsion polymerization. However,
it is essential to the process that the abovementioned ratio of the
number of equivalents of anionic dispersant to that of cationic
dispersant is maintained before or during the free radical emulsion
polymerization, depending on the electrophoretic sign of the finely
divided solid. If inorganic solid particles which have an
electrophoretic mobility with a negative sign under the
abovementioned pH conditions are used, the ratio of the number of
equivalents of anionic dispersant to that of cationic dispersant
must therefore be greater than 1 during the entire emulsion
polymerization. In a corresponding manner, in the case of inorganic
solids particles having an electrophoretic mobility with a positive
sign, the ratio of the number of equivalents of cationic dispersant
to that of anionic dispersant must be greater than 1 during the
entire emulsion polymerization. It is advantageous if the ratios of
the numbers of equivalents are .gtoreq.2, .gtoreq.3, .gtoreq.4, 24
5, .gtoreq.6, .gtoreq.7 or .gtoreq.10, the ratios of the numbers of
equivalents particularly advantageously being from 2to 5.
[0033] A further process for the treatment of paper surfaces
comprises treating the surface of the paper with an aqueous
dispersion which by mixing an aqueous polymer dispersion with at
least one dispersed, finely divided organic solid which has a
weight average particle diameter of <100 nm (process 2).
[0034] Aqueous polymer dispersions are generally known. They are
fluid systems which contain, present as the disperse phase
dispersed in an aqueous dispersing medium, polymer balls consisting
of a plurality of entangled polymer chains, i.e. the polymer matrix
or polymer particle. The diameter of the polymer particles is
frequently from 10 to 5000 nm.
[0035] The preparation of an aqueous polymer dispersion is
effected, for example, by means of free radical aqueous emulsion
polymerization. The procedure for a free radical aqueous emulsion
polymerization of ethylenically unsaturated monomers has been
widely described and is therefore sufficiently well known to a
person skilled in the art [cf. for example Encyclopedia of Polymer
Science and Engineering, Vol. 8, pages 659 to 677, John Wiley &
Sons, Inc., 1987; D. C. Blackley, Emulsion Polymerisation, pages
155 to 465, Applied Science Publishers, Ltd., Essex, 1975; D. C.
Blackley, Polymer Latices, 2.sup.nd Edition, Vol. 1, pages 33 to
415, Chapman & Hall, 1997; H. Warson, The Applications of
Synthetic Resin Emulsions, pages 49 to 244, Ernest Benn, Ltd.,
London, 1972; D. Diederich, Chemie in unserer Zeit 24 (1990), 135
to 142, Verlag Chemie, Weinheim; J. Piirma, Emulsion
Polymerisation, pages 1 to 287, Academic Press, 1982; F. Holscher,
Dispersionen synthetischer Hochpolymerer, pages 1 to 160,
Springer-Verlag, Berlin, 1969 and DE-A 40 03 422]. It is usually
carried out by dispersing the ethylenically unsaturated monomers in
the presence of dispersants in an aqueous medium and polymerizing
them by means of at least one free radical polymerization
initiator. The process disclosed in WO 03000760 differs from this
procedure only in an additional presence of at least one finely
divided inorganic solid which has an electrophoretic mobility
differing from zero and in the use of a special dispersant
combination during the polymerization.
[0036] Metals, metal compounds, such as metal oxides and metal
salts, but also semimetal and nonmetal compounds, are suitable
finely divided inorganic solids which can be used for both novel
processes. Noble metal colloids, for example palladium, silver,
ruthenium, platinum, gold and rhodium, and alloys containing them
can be used as finely divided metal powders. Examples of finely
divided metal oxides are titanium dioxide (for example commercially
available as Hombitec.RTM. grades from Sachtleben Chemie GmbH),
zirconium(IV) oxide, tin(II) oxide, tin(IV) oxide (for example
commercially available as Nyacol.RTM. SN grades from Akzo-Nobel),
alumina (for example commercially available as Nyacol.RTM. AL
grades from Akzo-Nobel), barium oxide, magnesium oxide, various
iron oxides, such as iron(II) oxide (wuestite), iron(II) oxide
(hematite) and iron(II/III) oxide (magnetite), chromium(III) oxide,
antimony(III) oxide, bismuth(III) oxide, zinc oxide (for example
commercially available as Sachtotece grades from Sachtleben Chemie
GmbH), nickel(II) oxide, nickel(III) oxide, cobalt(II) oxide,
cobalt(III) oxide, copper(II) oxide, yttrium(III) oxide (for
example commercially available as Nyacol.RTM. YTTRIA grades from
Akzo-Nobel), cerium(IV) oxide (for example commercially available
as Nyacol.RTM. CEO2 grades from Akzo-Nobel), in amorphous form
and/or in their various crystal modifications, and the hydrated
oxides thereof, for example hydrated titanium(IV) oxide, hydrated
zirconium(IV) oxide, hydrated aluminum oxide (for example
commercially available as Disperal.RTM. grades from Condea-Chemie
GmbH) and hydrated iron(III) oxide, in amorphous form and/or in
their different crystal modifications. The following amorphous
metal salts and metal salts present in their different crystal
structures can in principle be used in the novel process: sulfides,
such as iron(II) sulfide, iron(II) sulfide, iron(II) disulfide
(pyrite), tin(II) sulfide, tin(IV) sulfide, mercury(II) sulfide,
cadmium(II) sulfide, zinc sulfide, copper(II) sulfide, silver
sulfide, nickel(II) sulfide, cobalt(II) sulfide, cobalt(III)
sulfide, manganese(II) sulfide, chromium(III) sulfide, titanium(II)
sulfide, titanium(III) sulfide, titanium(IV) sulfide, zirconium(IV)
sulfide, antimony(III) sulfide and bismuth(II) sulfide, hydroxides,
such as tin(II) hydroxide, aluminum hydroxide, magnesium hydroxide,
calcium hydroxide, barium hydroxide, zinc hydroxide, iron(II)
hydroxide and iron(III) hydroxide, sulfates, such as calcium
sulfate, strontium sulfate, barium sulfate and lead(IV) sulfate,
carbonates, such as lithium carbonate, magnesium carbonate, calcium
carbonate, zinc carbonate, zirconium(IV) carbonate,
iron(II)-carbonate, and iron(III)-carbonate, orthophosphates, such
as lithium orthophosphate, calcium orthophosphate, zinc
orthophosphate, magnesium orthophosphate, aluminum orthophosphate,
tin(III) orthophosphate, iron(II) orthophosphate and iron(III)
orthophosphate, metaphosphates, such as lithium metaphosphate,
calcium metaphosphate and aluminum metaphosphate, pyrophosphates,
such as magnesium pyrophosphate, calcium pyrophosphate, zinc
pyrophosphate, iron(III) pyrophosphate and tin(II) pyrophosphate,
ammonium phosphates, such as magnesium ammonium phosphate and zinc
ammonium phosphate, hydroxyapatite [Ca.sub.5{(PO.sub.4).sub.3OH}],
orthosilicates, such as lithium orthosilicate, calcium/magnesium
orthosilicate, aluminum orthosilicate, iron(II) orthosilicate,
iron(III) orthosilicate, magnesium orthosilicate, zinc
orthosilicate, zirconium(III) orthosilicate and zirconium(IV)
orthosilicate, metasilicates, such as lithium metasilicate,
calcium/magnesium metasilicate, calcium metasilicate, magnesium
metasilicate and zinc metasilicate, sheet silicates, such as sodium
aluminum silicate and sodium magnesium silicate, in particular in
spontaneously delaminating form, for example Optigel.RTM. SH (grade
from Sudchemie AG), Saponit.RTM. SKS-20 and Hektorit.RTM. SKS 21
(grades from Hoechst AG) and Laponite.RTM. RD and Laponite.RTM. GS
(grades from Laporte Industries Ltd.), aluminates, such as lithium
aluminate, calcium aluminate and zinc aluminate, borates, such as
magnesium metaborate and magnesium orthoborate, oxalates, such as
calcium oxalate, zirconium(IV) oxalate, magnesium oxalate, zinc
oxalate and aluminum oxalate, tartrates, such as calcium tartrate,
acetylacetonates, such as aluminum acetylacetonate and iron(III)
acetylacetonate, salicylates, such as aluminum salicylate,
citrates, such as calcium citrate, iron(II) citrate and zinc
citrate, palmitates, such as aluminum palmitate, calcium palmitate
and magnesium palmitate, stearates, such as aluminum stearate,
calcium stearate, magnesium stearate and zinc stearate, laurates,
such as calcium laurate, linoleates, such as calcium linoleate,
oleates, such as calcium oleate, iron(II) oleate or zinc
oleate.
[0037] Amorphous silica and/or silica present in different crystal
structures may be mentioned as important semimetal compounds which
may be used according to the invention. Silica suitable according
to the invention is commercially available and can be obtained, for
example, as Aerosil.RTM. (grade from Degussa AG), Levasil.RTM.
(grade from Bayer AG), Ludox.RTM. (grade from DuPont), Nyacole and
Bindzil.RTM. (grades from Akzo-Nobel) and Snowtex.RTM. (grade from
Nissan Chemical Industries, Ltd.). Nonmetal compounds suitable
according to the invention are, for example, colloidal graphite or
diamond.
[0038] Particularly suitable finely divided inorganic solids are
those whose solubility in water at 20.degree. C. and 1 bar
(absolute) is .ltoreq.1, preferably .ltoreq.0.1, in particular
.ltoreq.0.01, g/l. Compounds selected from the group consisting of
silica, alumina, tin(IV) oxide, yttrium(III) oxide, cerium(IV)
oxide, hydrated aluminumoxide, calcium carbonate, magnesium
carbonate, calcium orthophosphate, magnesium orthophosphate,
calcium metaphosphate, magnesium metaphosphate, calcium
pyrophophate, magnesium pyrophosphate, iron(II) oxide, iron(III)
oxide, iron(II/III) oxide, titanium dioxide, hydroxylapatite, zinc
oxide and zinc sulfide are particularly preferred. Silica sols
which have an electrophoretic mobility with a negative sign are
particularly preferred.
[0039] The commercially available compounds of the Aerosil.RTM.,
Levasil.RTM., Ludox.RTM., Nyacol.RTM. and Bindzil.RTM. grades
(silica), Disperal.RTM. grades (hydrated aluminum oxide),
Nyacol.RTM. AL grades (alumina), Hombitec.RTM. grades (titanium
dioxide), Nyacol.RTM. SN grades (tin(IV) oxide), Nyacol.RTM. YTTRIA
grades (yttrium(III) oxide), Nyacol.RTM. CEO2 grades (cerium(IV)
oxide) and Sachtotec.RTM. grades (zinc oxide) can also
advantageously be used in the novel processes.
[0040] The finely divided inorganic solids which can be used in the
novel processes are such that the solid particles dispersed in the
aqueous reaction medium have a particle diameter of .ltoreq.100 nm.
Those finely divided inorganic solids whose disperse particles have
a particle diameter of >0 nm but .ltoreq.90 nm, .ltoreq.80 nm,
.ltoreq.70 nm, .ltoreq.60 nm, .ltoreq.50 nm, .ltoreq.40 nm,
.ltoreq.30 nm, .ltoreq.20 nm or .ltoreq.10 nm and all values in
between are successfully used. Finely divided inorganic solids
which have a particle diameter of .ltoreq.50 nm are advantageously
used. The particle diameters are determined using the analytical
ultracentrifuge method.
[0041] The finely divided solids are obtainable by a procedure
known in principle to a person skilled in the art and are obtained,
for example, by precipitation reactions or chemical reactions in
the gas phase (in this context, cf. E. Matijevic, Chem. Mater. 5
(1993), 412 to 426; Ullmann's Encyclopedia of Industrial Chemistry,
Vol. A 23, pages 583 to 660, Verlag Chemie, Weinheim, 1992; D. F.
Evans, H. Wennerstrom in The Colloidal Domain, pages 363 to 405,
Verlag Chemie, Weinheim, 1994, and R. J. Hunter in Foundations of
Colloid Science, Vol. 1, pages 10 to 17, Clarendon Press, Oxford,
1991).
[0042] The stable solid dispersion is frequently prepared directly
during the synthesis of the finely divided inorganic solids in an
aqueous medium or alternatively by dispersing the finely divided
inorganic solid in the aqueous medium. Depending on the method of
preparation of the finely divided inorganic solids, this is
effected either directly, for example in the case of precipitated
or pyrogenic silica, alumina, etc., or with the aid of suitable
auxiliary units, for example dispersers or ultrasonic
sonotrodes.
[0043] However, only those finely divided inorganic solids whose
aqueous solid dispersion, with an initial solids concentration of
.gtoreq.1% by weight, based on the aqueous dispersion of the finely
divided inorganic solid, still contains more than 90% by weight of
the originally dispersed solid in dispersed form one hour after
their preparation or as a result of stirring up or shaking up the
sedimented solids, without further stirring or shaking, and whose
dispersed solid particles have a diameter of .ltoreq.100 nm are
suitable according to the invention. Initial solids concentrations
of .ltoreq.60% by weight are usual. Advantageously, however,
initial solids concentrations of .ltoreq.55, .ltoreq.50,
.ltoreq.45, .ltoreq.40, .ltoreq.35, .ltoreq.30, .ltoreq.25,
.ltoreq.20, .ltoreq.15 or .ltoreq.10% byweight and .gtoreq.2,
.gtoreq.3, .gtoreq.4 or .gtoreq.5% by weight and all values in
between, based in each case on the aqueous dispersion of finely
divided inorganic solid, can also be used. According to the
invention, from 1 to 1000, as a rule from 5 to 300, frequently from
10 to 200, parts by weight of the at least one finely divided
inorganic solid are used per 100 parts by weight of the at least
one ethylenically unsaturated monomer in the preparation of aqueous
composite particle dispersions (process 1) or 100 parts by weight
of dispersion polymer (process 2).
[0044] Both in the preparation of the aqueous composite particle
dispersion and in the preparation of the aqueous polymer dispersion
and in the mixing thereof with the finely divided inorganic solid,
dispersants are present which keep both the finely divided
inorganic solid particles and the monomer droplets, and the
composite particles formed or the mixture of the polymer particles
and of the finely divided inorganic solid, dispersed in the aqueous
phase and thus ensure the stability of the aqueous dispersions
produced. Considerable dispersions are both the protective colloids
usually used for carrying out free radical aqueous emulsion
polymerization and emulsifiers.
[0045] A detailed description of suitable protective colloids
appears in Houben-Weyl, Methoden der organischen Chemie, Volume
XIV/1, Makromolekulare Stoffe, Georg-Thieme-Verlag, Stuttgart,
1961, pages 411 to 420.
[0046] Suitable neutral protective colloids are, for example,
polyvinyl alcohols, polyalkylene glycols, cellulose derivatives,
starch derivatives and gelatin derivatives.
[0047] Suitable anionic protective colloids, i.e. protective
colloids whose component having a dispersing effect has at least
one negative electrical charge, are, for example, polyacrylic acids
and polymethacrylic acids and the alkali metal salts thereof,
copolymers containing acrylic acid, methacrylic acid,
2-acrylamido-2-methylpropanesulfonic acid, 4-styrenesulfonic acid
and/or maleic anhydride, and the alkali metal salts thereof, and
alkali metal salts of sulfonic acids of high molecular weight
compounds, for example polystyrene.
[0048] Suitable cationic protective colloids, i.e. protective
colloids whose component having a dispersing effect has at least
one positive electrical charge, are, for example, the homo and
copolymers containing those derivatives of N-vinylpyrrolidone,
N-vinylcaprolactam, N-vinylcarbazole, 1-vinylimidazole,
2-vinylimidazole, 2-vinylpyridine, 4-vinylpyridine, acrylamide,
methacrylamide, amino-carrying acrylates, methacrylates,
acrylamides and/or methacrylamides which are protonated and/or
alkylated on the nitrogen.
[0049] Of course, mixtures of emulsifiers and/or protective
colloids may also be used. Frequently, exclusively emulsifiers
whose relative molecular weights, in contrast to the protective
colloids, are usually below 1500 are used as dispersants. Of
course, where mixtures of surface-active substances are used, the
individual components must be compatible with one another, which
can be checked by means of a few preliminary experiments in case of
doubt. An overview of suitable emulsifiers appears in Houben-Weyl,
Methoden der organischen Chemie, Volume XIV/1, Makromolekulare
Stoffe, Georg-Thieme-Verlag, Stuttgart, 1961, pages 192 to 208.
[0050] Customary nonionic emulsifiers are, for example, ethoxylated
mono-, di- and trialkyphenols (degree of ethoxylation: from 3 to
50, alkyl radical: C.sub.4 to C.sub.12) and ethoxylated fatty
alcohols (degree of ethoxylation: from 3 to 80; alkyl radical:
C.sub.8 to C.sub.36). Examples of these are Lutensol.RTM. A grades
(C.sub.12C.sub.14-fatty alcohol ethoxylates, degree of
ethoxylation: from 3 to 8), Lutensol.RTM. AO grades
(C.sub.13C.sub.15-oxo alcohol ethoxylates, degree of ethoxylation:
from 3 to 30), Lutensol.RTM. AT grades (C.sub.16C.sub.18-fatty
alcohol ethoxylates, degree of ethoxylation: from 11 to 80),
Lutensol.RTM. ON grades (C.sub.10-oxo alcohol ethoxylates, degree
of ethoxylation: from 3 to 11) and the Lutensole.RTM. TO grades
(C.sub.13-oxo alcohol ethoxylates, degree of ethoxylation: from 3
to 20) from BASF AG.
[0051] Conventional anionic emulsifiers are, for example, alkali
metal and ammonium salts of alkyl sulfates (alkyl radical: C.sub.8
to C.sub.12), of sulfuric monoesters of ethoxylated alkanols
(degree of ethoxylation: from 4 to 30, alkyl radical: C.sub.12 to
C.sub.18) and ethoxylated alkylphenols (degree of ethoxylation:
from 3 to 50, alkyl radical: C.sub.4 to C.sub.12), of
alkanesulfonic acids (alkyl radical: C.sub.12 to C,.sub.8) and of
alkylarylsulfonic acids (alkyl radical: C.sub.9 to C.sub.18).
[0052] Compounds of the formula I ##STR1## where R.sup.1 and
R.sup.2 are H or C.sub.4- to C.sub.24-alkyl and are not
simultaneously H, and A and B may be alkali metal ions and/or
ammonium ions, have also proven to be further anionic emulsifiers.
In formula I, R.sup.1 and R.sup.2 are preferably linear or branched
alkyl of 6 to 18, in particular 6, 12 or 16, carbon atoms or --H,
R.sup.1 and R.sup.2 not both simultaneously being H. A and B are
preferably sodium, potassium or ammonium, sodium being particularly
preferred. Compounds I in which A and B are sodium, R.sup.1 is
branched alkyl having 12 carbon atoms and R.sup.2 is H or R.sup.1
are particularly advantageous. Industrial mixtures which contain
from 50 to 90% by weight of the monoalkylated products, for example
Dowfax 2A1 (brand of Dow Chemical Company), are frequently used.
The compounds I are generally known, for example from U.S. Pat. No.
4,269,749, and are commercially available.
[0053] Suitable cationic emulsifiers are as a rule primary,
secondary, tertiary or quaternary ammonium salts, alkanolammonium
salts, pyridinium salts, imidazolinium salts, oxazolinium salts,
morpholinium salts, thiazolinium salts and salts of amine oxides,
quinolinium salts, isoquinolinium salts, tropylium salts, sulfonium
salts and phosphonium salts having a C.sub.6- to C.sub.18-alkyl,
C.sub.6- to C.sub.18-aralkyl or a heterocyclic radical. Examples
are dodecylammonium acetate or the corresponding hydrochloride, the
chlorides or acetates of the various
2-(N,N,N-trimethylammonium)ethylparaffinic acid esters,
N-cetylpyridinium chloride, N-laurylpyridinium sulfate and
N-cetyl-N,N,N-trimethylammonium bromide,
N-dodecyl-N,N,N-trimethylammonium bromide,
N-octyl-N,N,N-trimethylammonium bromide,
N,N-distearyl-N,N-dimethylammonium chloride and the Gemini
surfactant N,N'-(lauryldimethyl)ethylenediamine dibromide. Numerous
further examples appear in H. Stache, Tensid-Taschenbuch,
Carl-Hanser-Verlag, Munich, Vienna, 1981 and in McCutcheon's,
Emulsifiers & Detergents, MC Publishing Company, Glen Rock,
1989.
[0054] The aqueous dispersions which can be used according to the
invention in processes 1 and 2 contain, as a rule, from 0.1 to 10,
often from 0.5 to 7.0, frequently from 1.0 to 5.0,% by weight,
based in each case on the aqueous dispersion, of dispersant.
Emulsifiers are preferably used.
[0055] Suitable ethylenically unsaturated monomers for the
preparation of the composite particles which can be used according
to the invention (process 1) and the dispersion polymer used
according to the invention (process 2) are, inter alia, in
particular monomers which can be subjected to free radical
polymerization in a simple manner, such as ethylene, vinylaromatic
monomers, such as styrene, .alpha.-methylstyrene, o-chlorostyrene
or vinyltoluenes, esters of vinyl alcohol and monocarboxylic acids
of 1 to 18 carbon atoms, such as vinyl acetate, vinyl propionate,
vinyl n-butyrate, vinyl laurate and vinyl stearate, esters of
.alpha.,.beta.monoethylenically unsaturated mono- and dicarboxylic
acids preferably of 3 to 6 carbon atoms, in particular acrylic
acid, methacrylic acid, maleic acid, fumaric acid and itaconic
acid, with alkanols of in general 1 to 12, preferably 1 to 8, in
particular 1 to 4, carbon atoms, in particular methyl, ethyl,
n-butyl, isobutyl and 2-ethylhexyl acrylate and methacrylate,
dimethyl maleate or di-n-butyl maleate, nitriles of
.alpha.,.beta.-monoethylenically unsaturated carboxylic acids, such
as acrylonitrile, and conjugated C.sub.4-8-dienes, such as
1,3-butadiene and isoprene. Said monomers are, as a rule, the main
monomers, which together usually account for an amount of
.gtoreq.50, .gtoreq.80 or .gtoreq.90% by weight, based on the total
amount of the monomers to be polymerized by the novel process. As a
rule, these monomers have only moderate to low solubility in water
under standard conditions [20.degree. C., 1 bar (absolute)].
[0056] Monomers which usually increase the internal strength of the
films of the polymer matrix generally have at least one epoxy,
hydroxyl, N-methylol or carbonyl group, or at least two
nonconjugated ethylenically unsaturated double bonds. Examples of
these are monomers having two vinyl radicals, monomers having two
vinylidene radicals and monomers having two alkenyl radicals.
Particularly advantageous are the diesters of dihydric alcohols
with .alpha.,.beta.-monoethylenically unsaturated monocarboxylic
acids, among which acrylic and methacrylic acid are preferred.
Examples of such monomers having two nonconjugated ethylenically
unsaturated double bonds are alkylene glycol diacrylates and
dimethacrylates, such as ethylene glycol diacrylate, 1,2-propylene
glycol diacrylate, 1,3-propylene glycol diacrylate, 1,3-butylene
glycol diacrylate, 1,4-butylene glycol diacrylates and ethylene
glycol dimethacrylate, 1,2-propylene glycol dimethacrylate,
1,3-propylene glycol dimethacrylate, 1,3-butylene glycol
dimethacrylate or 1,4-butylene glycol dimethacrylate, and
divinylbenzene, vinyl methacrylate, vinyl acrylate, allyl
methacrylate, allyl acrylate, diallyl maleate, diallyl fumarate,
methylenebisacrylamide, cyclopentadienyl acrylate, triallyl
cyanurate or triallyl isocyanurate. Also of particular importance
in this context are the C.sub.1-C.sub.8-hydroxyalkyl methacrylates
and acrylates, such as n-hydroxyethyl, n-hydroxypropyl or
n-hydroxybutyl acrylate and methacrylate, and compounds such as
diacetoneacrylamide and acetylacetoxyethyl acrylate or
methacrylate. According to the invention, the abovementioned
monomers are incorporated in the form of polymerized units in
amounts of up to 5% by weight, based on the total amount of the
monomers to be polymerized.
[0057] Monomers containing siloxane groups, such as the
vinyltrialkoxysilanes, for example vinyltrimethoxysilane,
alkylvinyidialkoxysilanes, acryloyloxyalkyltrialkoxysilanes or
methacryloyloxyalkyltrialkoxysilanes, for example
acryloyloxyethyltrimethoxysilane,
methacryloyloxyethyltrimethoxysilane,
acryloyloxypropyltrimethoxysilane or
methacryloyloxypropyltrimethoxysilane, can optionally also be used.
These monomers are used in amounts of up to 2, frequently from 0.01
to 1, often from 0.05 to 0.5,% by weight, based in each case on the
total amount of monomers.
[0058] Those ethylenically unsaturated monomers A which contain at
least one acid group and/or the corresponding anion thereof or
those ethylenically unsaturated monomers B which contain at least
one amino, amido, ureido or N-heterocyclic group and/or the
ammonium derivatives thereof which are protonated or alkylated on
the nitrogen may additionally be used as monomers. The amount of
monomers A or monomers B is up to 10, often from 0.1 to 7,
frequently from 0.2 to 5,% by weight, based on the total amount of
monomers.
[0059] Ethylenically unsaturated monomers having at least one acid
group are used as monomers A. The acid group may be, for example, a
carboxyl, sulfo, sulfuric acid, phosphoric acid and/or phosphonic
acid group. Examples of monomers A are acrylic acid, methacrylic
acid, maleic acid, fumaric acid, itaconic acid, crotonic acid,
4-styrenesulfonic acid, 2-methacryloyloxyethylsulfonic acid,
vinylsulfonic acid and vinylphosphonic acid and phosphoric
monoesters of n-hydroxyalkyl acrylates and n-hydroxyalkyl
methacrylates, for example phosphoric monoesters of hydroxyethyl
acrylate, n-hydroxypropyl acrylate, n-hydroxybutyl acrylate and
hydroxyethyl methacrylate, n-hydroxypropyl methacrylate and
n-hydroxybutyl methacrylate. According to the invention, however,
it is also possible to use the ammonium and alkali metal salts of
the abovementioned ethylenically unsaturated monomers having at
least one acid group. Sodium and potassium are particularly
preferred as the alkali metal. Examples here are the ammonium,
sodium and potassium salts of acrylic acid, methacrylic acid,
maleic acid, fumaric acid, itaconic acid, crotonic acid,
4-styrenesulfonic acid, 2-methacryloyloxyethylsulfonic acid,
vinylsulfonic acid and vinylphosphonic acid and the mono- and
diammonium, mono- and disodium and mono- and dipotassium salts of
the phosphoric monoesters of hydroxyethyl acrylate, n-hydroxypropyl
acrylate, n-hydroxybutyl acrylate and hydroxyethyl methacrlate,
n-hydroxypropyl methacrylate or n-hydroxybutyl methacrylate.
[0060] Acrylic acid, methacrylic acid, maleic acid, fumaric acid,
itaconic acid, crotonic acid, 4-styrenesulfonic acid,
2-methacryloyloxyethylsulfonic acid, vinylsulfonic acid and
vinylphosphonic acid are preferably used.
[0061] Ethylenically unsaturated monomers which contain at least
one amino, amido, ureido or N-heterocyclic group and/or the
ammonium derivatives thereof which are protonated or alkylated on
the nitrogen are used as monomers B.
[0062] Examples of monomers B which contain at least one amino
group are 2-aminoethyl acrylate, 2-aminoethyl methacrylate,
3-aminopropyl acrylate, 3-aminopropyl methacrylate, 4-amino-n-butyl
acrylate, 4-amino-n-butyl methacrylate, 2-(N-methylamino)ethyl
acrylate, 2-(N-methylamino)ethyl methacrylate,
2-(N-ethylamino)ethyl acrylate, 2-(N-ethylamino)ethyl methacrylate,
2-(N-n-propylamino)ethyl acrylate, 2-(N-n-propylamino)ethyl
methacrylate, 2-(N-isopropylamino)ethyl acrylate,
2-(N-isopropylamino)ethyl methacrylate, 2-(N-tert-butylamino)ethyl
acrylate, 2-(N-tert-butylamino)ethyl methacrylate (for example
commercially available as Norsocryl.RTM. TBAEMA from Elf Atochem),
2-(N,N-dimethylamino)ethyl acrylate (for example commercially
available as Norsocryl.RTM. ADAME from Elf Atochem),
2-(N,N-dimethylamino)ethyl methacrylate (for example commercially
available as Norsocryl.RTM. MADAME from Elf Atochem),
2-(N,N-diethylamino)ethyl acrylate, 2-(N,N-diethylamino)ethyl
methacrylate, 2-(N,N-di-n-propylamino)ethyl acrylate,
2-(N,N-di-n-propylamino)ethyl methacrylate,
2-(N,N-diisopropylamino)ethyl acrylate,
2-(N,N-diisopropylamino)ethyl methacrylate, 3-(N-methylamino)propyl
acrylate, 3-(N-methylamino)propyl methacrylate,
3-(N-ethylamino)propyl acrylate, 3-(N-ethylamino)propyl
methacrylate, 3-(N-n-propylamino)propyl acrylate,
3-(N-n-propylamino)propyl methacrylate, 3-(N-isopropylamino)propyl
acrylate, 3-(N-isopropylamino)propyl methacrylate,
3-(N-tert-butylamino)propyl acrylate, 3-(N-tert-butylamino)propyl
methacrylate, 3-(N,N-dimethylamino)propyl acrylate,
3-(N,N-dimethylamino)propyl methacrylate,
3-(N,N-diethylamino)propyl acrylate, 3-(N,N-diethylamino)propyl
methacrylate, 3-(N,N-di-n-propylamino)propyl acrylate,
3-(N,N-di-n-propylamino)propyl methacrylate,
3-(N,N-diisopropylamino)propyl acrylate and
3-(N,N-diisopropylamino)propyl methacrylate.
[0063] Examples of monomers B which contain at least one amido
group are acrylamide, methacrylamide, N-methylacrylamide,
N-methylmethacrylamide, N-ethylacrylamide, N-ethylmethacrylamide,
N-n-propylacrylamide, N-n-propylmethacrylamide,
N-isopropylacrylamide, N-isopropylmethacrylamide,
N-tert-butylacrylamide, N-tert-butylmethacrylamide,
N,N-dimethylacrylamide, N,N-dimethylmethacrylamide,
N,N-diethylacrylamide, N,N-diethylmethacrylamide,
N,N-di-n-propylacrylamide, N,N-di-n-propylmethacrylamide,
N,N-diisopropylacrylamide, N,N-diisopropylmethacrylamide,
N,N-di-n-butylacrylamide, N, N-di-n-butylmethacrylamide, N-(3-N',
N'-dimethylaminopropyl)methacrylamide, diacetoneacrylamide,
N,N'-methylenebisacrylamide, N-(diphenylmethyl)acrylamide,
N-cyclohexylacrylamide, but also N-vinylpyrrolidone and
N-vinylcaprolactam.
[0064] Examples of monomers B which contain at least one ureido
group are N,N'-divinylethyleneurea and 2-(1-imidazolin-2-onyl)ethyl
methacrylate (for example commercially available as Norsocryl.RTM.
100 from Elf Atochem).
[0065] Examples of monomers B which contain at least one
N-heterocyclic group are 2-vinylpyridine, 4-vinylpyridine,
1-vinylimidazole, 2-vinylimidazole and N-vinylcarbazole.
[0066] The following compounds are preferably used:
2-vinylpyridine, 4-vinylpyridine, 2-vinylimidazole,
2-(N,N-dimethylamino)ethyl acrylate, 2-(N,N-dimethylamino)ethyl
methacrylate, 2-(N,N-diethylamino)ethyl acrylate,
2-(N,N-diethylamino)ethyl methacrylate, 2-(N-tert-butylamino)ethyl
methacrylate, N-(3-N',N'-dimethylaminopropyl)methacrylamide and
2-(1-imidazolin-2-onyl)ethyl methacrylate.
[0067] Depending on the pH of the aqueous reaction medium, a part
or the total amount of the abovementioned nitrogen-containing
monomers B may be present in the quaternary ammonium form
protonated on the nitrogen.
[0068] Examples of monomers B which have a quaternary alkylammonium
structure on the nitrogen are 2-(N,N,N-trimethylammonium)ethyl
acrylate chloride (for example commercially available as
Norsocryl.RTM. ADAMQUAT MC 80 from Elf Atochem),
2-(N,N,N-trimethylammonium)ethyl methacrylate chloride (for example
commercially available as Norsocryle MADQUAT MC 75 from Elf
Atochem), 2-(N-methyl-N,N-diethylammonium)ethyl acrylate chloride,
2-(N-methyl-N,N-diethylammonium)ethyl methacrylate chloride,
2-(N-methyl-N,N-dipropylammonium)ethyl acrylate chloride,
2-(N-methyl-N,N-dipropylammonium)ethyl methacrylate,
2-(N-benzyl-N,N-dimethylammonium)ethyl acrylate chloride (for
example commercially available as Norsocry.RTM. ADAMQUAT BZ 80 from
Elf Atochem), 2-(N-benzyl-N,N-dimethylammonium)ethyl methacrylate
chloride (for example commercially available as Norsocryl.RTM.
MADQUAT BZ 75 from Elf Atochem),
2-(N-benzyl-N,N-diethylammonium)ethyl acrylate chloride,
2-(N-benzyl-N,N-diethylammonium)ethyl methacrylate chloride, 2-(
N-benzyl-N,N-dipropylammonium)ethyl acrylate chloride,
2-(N-benzyl-N,N-dipropylammonium)ethyl methacrylate chloride,
3-(N,N,N-trimethylammonium)propyl acrylate chloride,
3-(N,N,N-trimethylammonium)propyl methacrylate chloride,
3-(N-methyl-N,N-diethylammonium)propyl acrylate chloride,
3-(N-methyl-N,N-diethylammonium)propyl methacrylate chloride,
3-(N-methyl-N,N-dipropylammonium)propyl acrylate chloride,
3-(N-methyl-N,N-dipropylammonium)propyl methacrylate chloride,
3-(N-benzyl-N,N-dimethylammonium)propyl acrylate chloride,
3-(N-benzyl-N,N-dimethylammonium)propyl methacrylate chloride,
3-(N-benzyl-N,N-diethylammonium)propyl acrylate chloride,
3-(N-benzyl-N,N-diethylammonium)propyl methacrylate chloride,
3-(N-benzyl-N,N-dipropylammonium)propyl acrylate chloride and
3-(N-benzyl-N,N-dipropylammonium)propyl methacrylate chloride. Of
course, the corresponding bromides and sulfates can also be used
instead of said chlorides.
[0069] 2-(N,N,N-Trimethylammonium)ethyl acrylate chloride,
2-(N,N,N-trimethylammonium)ethyl methacrylate chloride,
2-(N-benzyl-N,N-dimethylammonium)ethyl acrylate chloride and
2-(N-benzyl-N,N-dimethylammonium)ethyl methacrylate chloride are
preferably used.
[0070] Mixtures of the abovementioned ethylenically unsaturated
monomers can of course also be used.
[0071] All those free radical polymerization initiators which are
capable of initiating a free radical aqueous emulsion
polymerization are suitable for the preparation of the aqueous
composite particle dispersion and of the aqueous polymer dispersion
by free radical polymerization. In principle, these may be both
peroxides and azo compounds. Redox initiator systems are of course
also suitable. Peroxides which may be used in principle are
inorganic peroxides, such as hydrogen peroxide or peroxodisulfates,
such as the mono- or di-alkali metal or ammonium salts of
peroxodisulfuric acid, for example the mono- and disodium or mono-
and dipotassium or ammonium salts, or organic peroxides, such as
alkyl hydroperoxides, for example tert-butyl, p-menthyl or cumyl
hydroperoxide, and dialkyl or diaryl peroxides, such as
di-tert-butyl or dicumyl peroxide. Azo compounds used are
substantially 2,2'-azobisisobutyronitrile,
2,2'-azobis(2,4-dimethylvaleronitrile) and
2,2'-azobis(amidinopropyl) dihydrochloride (AIBA, corresponds to
V-50 from Wako Chemicals). Suitable oxidizing agents for redox
initiator systems are substantially the abovementioned peroxides.
Sulfur compounds having a low oxidation state, such as alkali metal
sulfites, for example potassium and/or sodium sulfite, alkali metal
hydrogen sulfites, for example potassium and/or sodium hydrogen
sulfide, alkali metal bisulfites, for example potassium and/or
sodium metabisulfite, formaldehyde sulfoxylates, for example
potassium and/or sodium formaldehyde sulfoxylate, alkali metal
salts, especially potassium and/or sodium salts of aliphatic
sulfinic acids and alkali metal hydrogen sulfides, for example
potassium and/or sodium hydrogen sulfide, salts of polyvalent
metals, such as iron(II) sulfate, iron(II) ammonium sulfate or
iron(II) phosphate, enediols, such as dihydroxymaleic acid, benzoin
and/or ascorbic acid, and reducing saccharides, such as sorbose,
glucose, fructose and/or dihydroxyacetone, may be used as
corresponding reducing agents. As a rule, the amount of the free
radical polymerization initiator used is from 0.1 to 5% by weight,
based on the total amount of the monomer mixture.
[0072] The entire range from 0 to 170.degree. C. is suitable as the
reaction temperature for the free radical aqueous polymerization
reaction in the presence or absence of the finely divided inorganic
solid. As a rule, temperatures of from 50 to 120.degree. C.,
frequently from 60 to 110.degree. C., often from .gtoreq.70 to
100.degree. C., are used. The free radical aqueous emulsion
polymerization can be carried out at a pressure less than, equal to
or greater than 1 bar (absolute), it being possible for the
polymerization temperature to exceed 100.degree. C. and to be up to
170.degree. C. Readily volatile monomers, such as ethylene,
butadiene or vinyl chloride, are preferably-polymerized
under-superatmospheric pressure. The pressure may be 1.2, 1.5, 2,
5, 10 or 15 bar or may also assume higher values. If emulsion
polymerizations are carried out under reduced pressure, pressures
of 950, frequently 900, often 850, mbar (absolute) are established.
The free radical aqueous emulsion polymerization is advantageously
carried out at 1 bar (absolute) under an inert gas atmosphere, for
example under nitrogen or argon.
[0073] The aqueous reaction medium can in principle also comprise
water-soluble organic solvents, such as methanol, ethanol,
isopropanol, butanols, pentanols, acetone, etc. However, the
polymerization reaction is preferably effected in the absence of
said solvents.
[0074] In addition to the abovementioned components, free radical
chain transfer compounds may optionally also be used in the
processes for the preparation of the aqueous composite particle
dispersion or the aqueous polymer dispersion, in order to reduce or
control the molecular weight of the polymers obtainable by the
polymerization. Substantially aliphatic and/or araliphatic halogen
compounds, for example n-butyl chloride, n-butyl bromide, n-butyl
iodide, methylene chloride, ethylene chloride, chloroform,
bromoform, bromotrichloromethane, dibromodichloromethane, carbon
tetrachloride, carbon tetrabromide, benzyl chloride or benzyl
bromide, organic thio compounds, such as primary, secondary or
tertiary aliphatic thiols, for example ethanethiol, n-propanethiol,
2-propanethiol, n-butanethiol, 2-butanethiol,
2-methyl-2-propanethiol, n-pentanethiol, 2-pentanethiol,
3-pentanethiol, 2-methyl-2-butanethiol, 3-methyl-2-butanethiol,
n-hexanethiol, 2-hexanethiol, 3-hexanethiol,
2-methyl-2-pentanethiol, 3-methyl-2-pentanethiol,
4-methyl-2-pentanethiol, 2-methyl-3-pentanethiol,
3-methyl-3-pentanethiol, 2-ethylbutanethiol, 2-ethyl-2-butanethiol,
n-heptanethiol and its isomeric compounds, n-octanethiol and its
isomeric compounds, n-nonanethiol and its isomeric compounds,
n-decanethiol and its isomeric compounds, n-undecanethiol and its
isomeric compounds, n-dodecanethiol and its isomeric compounds,
n-tridecanethiol and its isomeric compounds, substituted thiols,
for example 2-hydroxyethanethiol, aromatic thiols, such as
benzenethiol, ortho-, meta- or para-methylbenzenethiol, and all
further sulfur compounds described in Polymerhandbook 3.sup.rd
edition, 1989, J. Brandrup and E. H. Immergut, John Wiley &
Sons, Section II, pages 133 to 141, but also aliphatic and/or
aromatic aldehydes, such as acetaldehyde, propionaldehyde and/or
benzaldehyde, unsaturated fatty acids, such as oleic acid, dienes
having nonconjugated double bonds, such as divinylmethane or
vinylcyclohexane, or hydrocarbons having readily abstractable
hydrogen atoms, for example toluene, are used. However, it is also
possible to use mixtures of the abovementioned free radical chain
transfer compounds which do not interfere. The optionally used
total amount of the free radical chain transfer compounds is as a
rule .ltoreq.5, often .ltoreq.3, frequently .ltoreq.1,% by weight,
based on the total amount of the monomers to be polymerized.
[0075] The aqueous composite particle dispersions used according to
the invention and the aqueous dispersions comprising aqueous
polymer dispersion and finely divided inorganic solid usually have
a total solids content of from 1 to 70, frequently from 5 to 65,
often from 10 to 60,% by weight.
[0076] The composite particles or dispersion polymers used
according to the invention have, as a rule, particle diameters of
>0 and .ltoreq.1000 nm, frequently .ltoreq.500 nm, often
.ltoreq.250 nm. The determination of these particle diameters, too,
is effected by the analytical ultracentrifuge method. The stated
values correspond to the d.sub.50 values.
[0077] The composite particles which can be used according to the
invention may have different structures. The composite particle may
contain one or more of the finely divided solid particles. The
finely divided solid particles may be completely surrounded by the
polymer matrix. However, it is also possible for a part of the
finely divided solid particles to be surrounded by the polymer
matrix while another part is arranged on the surface of the polymer
matrix. Of course, it is also possible for a major part of the
finely divided solid particles to be bound on the surface of the
polymer matrix.
[0078] It should also be stated that the aqueous composite particle
dispersions can be dried in a simple manner to give redispersible
composite particle powders (for. example by freeze-drying or
spray-drying). This is true in particular when the glass transition
temperature of the polymer matrix of the composite particles
obtainable according to the invention is .gtoreq.50.degree. C.,
preferably .gtoreq.60.degree. C., particularly preferably
.gtoreq.70.degree. C., very particularly preferably
.gtoreq.80.degree. C., especially preferably .gtoreq.90.degree. C.
or .gtoreq.100.degree. C. The composite particle powders are also
suitable for the novel treatment of paper surfaces.
[0079] The mixtures of aqueous polymer dispersion and finely
divided inorganic solid are obtained, for example, by stirring the
corresponding amount of the finely divided inorganic solid, either
in the form of powder or in the form of an aqueous solid
dispersion, into an aqueous polymer dispersion stirred at from 20
to 25.degree. C. (room temperature) and mixing homogeneously.
[0080] In the novel treatment of the paper surface, the composite
particles or the mixture of dispersion polymer and finely divided
inorganic solid is or are applied to the paper surface in an amount
of from 0.1 to 100, often from 0.2 to 20, frequently from 0.5 to
10, g/m.sup.2 of paper. Larger amounts are also conceivable but as
a rule are not economically expedient. If the composite particles
or the mixture of dispersion polymer and finely divided inorganic
solid is or are applied to the paper surface in the form of aqueous
polymer dispersions, the abovementioned amounts are based on those
amounts of composite particles or of mixture of dispersion polymer
and finely divided inorganic solid which are contained in the
aqueous dispersions. After the application of the aqueous
dispersions, a drying step familiar to a person skilled in the art
is as a rule carried out.
[0081] In particular, those composite particles or dispersion
polymers whose polymers can be formed into films and whose minimum
film formation temperature is .ltoreq.150.degree. C., preferably
.ltoreq.100.degree. C., particularly preferably .ltoreq.50.degree.
C., are used for the novel process. Since the minimum film
formation temperature is no longer measurable below 0.degree. C.,
the lower limit of the minimum film formation temperature can be
specified only by the glass transition temperature. The glass
transition temperatures should not fall below -60.degree. C.,
preferably -30.degree. C. The determination of the minimum film
formation temperature is effected according to DIN 53 787 or ISO
2115 and the determination of the glass transition temperature
according to DIN 53 765 (differential scanning calorimetry, 20
K/min, midpoint measurement).
[0082] It may be advantageous if the paper coated with composite
particles, particularly when coating is effected in the form of
their aqueous dispersions, is subjected, after the coating process,
to pressures and/or temperatures such that the polymer contained in
the composite particles (process 1) forms a film. The same also
applies if the paper surfaces are coated according to process 2
with an aqueous dispersion of a mixture of polymer and finely
divided inorganic solid. Whether the drying conditions
(temperature/pressure) are chosen so that the polymer forms a film,
for example with the use of aqueous dispersions, or whether the
film formation is effected in a downstream separate step is of no
importance. When the corresponding aqueous dispersions are used,
the film formation step frequently takes place during the
drying.
[0083] The coated papers obtainable by the novel processes have a
wide range of uses, for example as writing paper, newsprint, paper
for journals, catalogs or books, as banknote paper, Bible paper,
kraft paper, capacitor paper or photographic paper.
[0084] Advantageously, the novel papers can be written on and, for
example, printed on by means of offset, flexographic and gravure
printing processes. In particular the printed novel papers
obtainable by the offset printing process have advantages with
regard to their dry strength, wet picking resistance and ink
absorption resistance and their good mottle properties.
EXAMPLES
I. Preparation of an Aqueous Composite Particle Dispersion
[0085] 416.6 g of Nyacol.RTM. 2040 and then a mixture of 2.5 g of
methacrylic acid and 12 g of a 10% strength by weight aqueous
solution of sodium hydroxide were introduced in the course of 5
minutes into a 2 I four-necked flask equipped with a reflux
condenser, a thermometer, a mechanical stirrer and a metering
apparatus, at from 20 to 25.degree. C. (room temperature) and 1 bar
(absolute) under a nitrogen atmosphere and with stirring (200
revolutions per minute). A mixture of 10.4 g of a 20% strength by
weight aqueous solution of the nonionic surfactant Lutensol.RTM. AT
18 (trade name of BASF AG, C.sub.16C.sub.18-fatty alcohol
ethoxylate having on average 18 ethylene oxide units) and 61.4 g of
demineralized water was then added to the stirred reaction mixture
in the course of 15 minutes. 0.83 9 of
N-cetyl-N,N,N-trimethylammonium bromide (CTAB), dissolved in 200 g
of demineralized water, was then metered into the reaction mixture
in the course of 60 minutes. The reaction mixture was then heated
to a reaction temperature of 80.degree. C.
[0086] At the same time, a monomer mixture consisting of 117.5 g of
methyl methacrylate, 130 g of n-butyl acrylate and 0.5 g of
methacryloyloxypropyltrimethoxysilane was prepared as feed 1 and an
initiator solution consisting of 2.5 g of sodium peroxodisulfate,
11.5 g of a 10% strength by weight solution of sodium hydroxide and
100 g of demineralized water was prepared as feed 2.
[0087] 21.1 9 of feed 1 and 57.1 9 of feed 2 was then added via two
separate feed lines in the course of 5 minutes to the reaction
mixture stirred at the reaction temperature. The reaction mixture
was then stirred for one hour at the reaction temperature. 0.92 g
of a 45% strength by weight aqueous solution of Dowfax.RTM. 2A1 was
then added to the reaction mixture. In the course of 2 hours,
beginning at the same time, the remainders of feed 1 and feed 2
were then metered continuously into the reaction mixture.
[0088] Thereafter, the reaction mixture was stirred for a further
hour at reaction temperature and then cooled to room
temperature.
[0089] The aqueous composite particle dispersion thus obtained had
a solids content of 40.1% by weight, based on the total weight of
the aqueous composite particle dispersion.
[0090] By dilution with demineralized water, the solids content of
the aqueous composite particle dispersion was brought to 10% by
weight at room temperature with stirring.
II. Testing of Performance Characteristics
[0091] For the investigation, wood-free base paper (basis weight 70
g/m.sup.2) from Scheufelen,-Germany, was coated with 10 g/m.sup.2
of a coating slip (calculated as solid), consisting of [0092] 70
parts by weight of Hydrocarb.RTM. 90 (calcium carbonate from Omya
AG, Switzerland), [0093] 30 parts by weight of Amazon Plus.RTM.
(kaolin from CADAM S.A, Brazil), [0094] 0.15 part by weight of
Polysalz.RTM. (45% strength by weight aqueous solution of a
polyacrylic acid sodium salt from BASF AG, Germany), [0095] 10
parts by weight of Styronal.RTM. PR 8736 (50% strength by weight
aqueous styrene/butadiene dispersion from BASF AG, Germany), [0096]
0.3 part by weight of Sterocoll.RTM. FD (25% strength by weight
aqueous ethyl acrylate/acrylic acid/methacrylic acid dispersion
from BASF AG, Germany) and [0097] 34 parts by weight of
demineralized water, by means of a DT Laboratory Coater from DT
Paper Science Oy Ab, Finland at 30.degree. C. and atmospheric
pressure (stiff blade having a thickness of 0.3 mm). The paper web
was dried by means of an IR drying unit and air drying (8 IR lamps
of 650 watt each, throughput speed 30 m/min).
[0098] Test strips measuring 35 cm.times.20 cm were cut from the
paper webs and were uniformly coated with the dilute aqueous
composite particle dispersion. The amount of said dispersion was
such that the amount of composite particles was 1.0 g/m.sup.2 of
paper surface. The test strips were then stored for 15 hours at
23.degree. C. and a relative humidity of 50% (DIN 50014-23/50-2).
The test strips were then calendered by means of the table
laboratory calender K8/2 from Kleinewefers Anlagen GmbH, Germany,
at room temperature. The nip pressure between the rolls was 200
kN/cm paper width and the speed was 10 m/min. The process was
carried out four times altogether.
Comparative Example
[0099] The comparative example was carried out according to the
abovementioned example, with the exception that the surface was not
treated with the aqueous composite particle dispersion.
Determination of the Dry Picking Resistance Using the IGT Proof
Printer (IGT Dry)
[0100] The test strips were printed at increasing speed in a
printing unit (IGT printability tester AC2/AIC2) using a standard
ink (printing ink 3808 from Lorilleux-Lefranc). The maximum
printing speed was 200 cm/s. The ink was applied at a nip pressure
of 350 N/cm.
[0101] The speed, in cm/sec, at which there were 10 picks from the
paper coating slip (pick points) after the beginning of printing is
stated as a measure of the dry picking resistance. The higher this
printing speed at the tenth pick point, the better is the result
rated.
Wet Picking Resistance
[0102] The test strips were produced and prepared as in the case of
the testing of the dry picking resistance.
[0103] The printing unit (IGT printability tester AC2/AIC2) was set
up in such a way that the test strips were moistened with water
before the printing process.
[0104] The printing was carried out at a constant speed of 0.6
cm/s.
[0105] Picks from the paper are visible as unprinted areas. For the
determination of the wet picking resistance, the ink density in
comparison with a solid hue is therefore determined in % using a
color densitometer. The higher the stated ink density, the better
the wet picking resistance.
Picking Resistance in the Case of Multiple Printing (Offset
Test)
[0106] The printing of the test strips [cf. testing of the dry
picking resistance] was carried out at a constant speed of 1 m/s
and at a nip pressure of 200 N/cm.
[0107] The printing process was repeated after 30 seconds. The
number of passes until picking occurred is stated as the picking
resistance. The larger the number of print processes until the
first picking occurs, the better is the result rated.
TABLE-US-00001 TABLE 1 List of results Dry picking Wet picking
Offset test resistance in cm/s resistance % Number Example 71 57 6
Comparative example 63 51 4
* * * * *