U.S. patent application number 10/575017 was filed with the patent office on 2007-11-29 for coated paper as a printed material.
Invention is credited to Franz-Josef Becker, Viktor Uerlings.
Application Number | 20070272382 10/575017 |
Document ID | / |
Family ID | 34306855 |
Filed Date | 2007-11-29 |
United States Patent
Application |
20070272382 |
Kind Code |
A1 |
Becker; Franz-Josef ; et
al. |
November 29, 2007 |
Coated Paper as a Printed Material
Abstract
The present invention relates to a paper which contains a paper
substrate and a preparation applied to at least one side of the
paper substrate over the entire surface. The preparation contains
at least one surfactant and at least one pigment having a particle
diameter of from 1 to 500 nm, and a binder in a ratio to the
pigment of not more than 5 parts by weight of binder: 100 parts by
weight of pigment (based in each case on the solids content). In
present invention is also related to the process of production of
the paper.
Inventors: |
Becker; Franz-Josef;
(Gladbach, DE) ; Uerlings; Viktor; (Duren,
DE) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET
FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Family ID: |
34306855 |
Appl. No.: |
10/575017 |
Filed: |
July 13, 2004 |
PCT Filed: |
July 13, 2004 |
PCT NO: |
PCT/EP04/07699 |
371 Date: |
April 9, 2007 |
Current U.S.
Class: |
162/136 |
Current CPC
Class: |
D21H 23/22 20130101;
D21H 19/44 20130101; D21H 19/82 20130101; G03G 7/0026 20130101;
B41M 5/52 20130101; G03G 7/0013 20130101; G03G 7/002 20130101 |
Class at
Publication: |
162/136 |
International
Class: |
D21H 19/44 20060101
D21H019/44 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 8, 2003 |
EP |
03022471.1 |
Claims
1. Paper comprising: a) a paper substrate and b) a preparation
applied to at least one side of the paper substrate over the entire
surface and containing at least one surfactant and at least one
pigment having a particle diameter of from 1 to 500 nm, the
preparation containing a binder in a ratio to the pigment of not
more than 5 parts by weight of binder:100 parts by weight of
pigment (based in each case on the solids content).
2. The paper according to claim 1, wherein the preparation has a
coat weight of from 0.5 to 20 g/m.sup.2 (absolutely dry) per
side.
3. The paper according to claim 1, wherein from 0.05 to 2.5
g/m.sup.2 (absolutely dry) of surfactant are present per side in
the preparation.
4. The paper according to claim 1, wherein the surfactant is an
anionic, cationic, nonionic or amphoteric surfactant.
5. The paper according to claim 1, wherein from 0.45 to 17.5
g/m.sup.2 (absolutely dry) of pigment are present per side in the
preparation.
6. The paper according to claim 1, wherein the pigment has an
overall cationic and/or anionic and/or nonionic charge.
7. The paper according to claim 1, wherein the pigment is an oxide
and/or mixed oxide of a metal and/or an oxide and/or mixed oxide of
a semimetal/semiconductor.
8. The paper according to claim 1, wherein the preparation contains
at least one further additive.
9. The paper according to claim 1, wherein the paper substrate
contains at least one filler.
10. The paper according to claim 9, wherein the filler has a cavity
volume.
11. The paper according to claim 9, wherein the filler has an oil
number, measured according to DIN EN ISO 787-5, of from 10 to 150
g/100 g of filler.
12. The paper according to claim 9, wherein the filler is selected
from the group consisting of chalk, precipitated chalk, clay, talc,
calcined clay, alumina, aluminum hydroxide, gypsum, hydrated
alumina, silica, silicic acid, diatomaceous earth, titanium dioxide
and mixtures thereof.
13. The paper according to claim 1, wherein the paper substrate
contains at least one additive.
14. The paper according to claim 1, wherein at least one further
coating is present on the preparation on that side of the paper
substrate on which the preparation is applied.
15. The paper according to claim 14, wherein the coating contains
at least one pigment and at least one binder.
16. The paper according to claim 15, wherein the pigment has a
particle diameter of from 1 to 500 nm and is selected from the
group consisting of oxide and/or mixed oxide of a metal, oxide
and/or mixed oxide of a semimetal/semiconductor and mixtures
thereof.
17. The paper according claim 14, wherein the coating contains at
least one further additive.
18. Process for the production of a paper, comprising applying a
preparation containing at least one surfactant and at least one
pigment having a particle diameter of from 1 to 500 nm to the
entire surface on at least one side of a paper substrate, the
preparation containing binder in a ratio to pigment of not more
than 5 parts by weight of binder:100 parts by weight of pigment
(based in each case on the solids content).
19. The process for the production of a paper according to claim
18, further comprising applying a coating is on the preparation on
that side of the paper substrate on which the preparation was
applied.
20. (canceled)
21. (canceled)
Description
[0001] The present application relates to a natural paper having
good printability. The present application furthermore relates to
the provision of a process for the production of natural papers
having good printability.
[0002] In the paper industry, attempts are constantly being made to
improve the printability of papers. This applies in particular to
papers which are used in offset printing and to papers for the new
digital print media, such as, for example, inkjet papers or papers
for digital printers. In the case of the papers which are used for
said printing processes, it is possible in principle to distinguish
between two classes of papers: the natural papers and the coated
papers. In the case of the coated papers, at least one coating
which usually consists of pigments, binders and additives is
applied to that side of the paper on which printing is to be
effected. For improving the printability, a plurality of coats,
such as, for example, two or three coats, can also be applied to
the coated papers. This improves the printability as a function of
the coverage of the web of the raw paper, i.e. the more coating
applied, the better is the printability.
[0003] The applied coatings can be divided into two classes, namely
the glossy and the matt coatings. They differ in their composition
and in the subsequent processing steps in the production of the
coated papers. A surface treatment by means of a calender or a
smoothing unit after application of the coating will be mentioned
in particular here. A disadvantage here is that the impression,
i.e. the appearance and the feel, i.e. the haptic properties, of
the paper is adversely affected by the applied coatings.
[0004] Natural papers do not have these disadvantages. Since they
have no coating with the high coat weights of the coated papers,
the original character of the paper is retained. In particular, the
stiffness and the surface structure of the natural paper are not
changed or not significantly changed. This leads to a pleasant feel
on touching the papers (pleasant haptic properties) and a pleasant
visual appearance of these papers. For this reason, they are used
for high-quality applications, such as, for example, office
correspondence or demanding catalogs, brochures and books,
especially those which are artistically designed. The quality of
the print on natural papers is, however, poorer than on coated
papers. The surface contour of the natural paper is recognizable in
the print.
[0005] Owing to the fiber structure of the natural papers, the
surface of which, expressed simply, consists of peaks and valleys,
the printing ink is accepted to different extents in the printing
process. Particularly in the case of multicolor prints, this has a
disadvantageous effect since superposition of the individual
printing inks results here and the surface structure of the natural
paper is thus particularly visible in the print.
[0006] There has been no lack of attempts to combine both the
visual impression and the haptic properties of a natural paper with
the good printability of a coated paper.
[0007] EP 0 648 894 proposes providing a cardboard with a coating
which has a coat weight of 1-5 g/m.sup.2 and consists of a pigment
having an oil absorptivity of at least 80 g/100 g of pigment and a
binder. A disadvantage is that the composition described in EP 0
648 894 can be used only on boxboards having high weight, which
preferably have a basis weight of at least 180 g/m.sup.2.
[0008] In U.S. Pat. No. 6,387,213 the printability of a paper is
improved by applying a composition which contains a hollow plastic
pigment in a proportion of 30-60% by weight, based on the dry
weight of the coating. Furthermore, the formulation contains a
binder in a proportion of 40-70% by weight based on the dry weight
in the formulation, which binder is a modified starch having a high
molecular weight. The formulation should preferably be applied as a
contour coat to the paper substrate. The high costs of the coating,
which are due to the hollow plastic pigment and the modified starch
having a high molecular weight, are disadvantageous here.
[0009] EP 1 146 171 adopts another approach for improving the
printability of a paper. A top coat which contains a pigment and a
rheology-modifying/binder component is applied to a paper substrate
which has a surface roughness of less than 6 .mu.m and a surface
gloss of 5-80%. Here, it is preferable if the top coat is applied
as a single coat having a coat thickness which preferably
corresponds to the size of a pigment particle. A disadvantage of
the paper presented in EP 1 146 171 is that the paper substrate
must have a defined surface roughness of less than 6 .mu.m and that
the top coat must be applied to the substrate in a coat thickness
which corresponds to the size of the pigments.
[0010] The subsequently published European Patent Application 03
000 835.3 describes how it is possible to produce a patterned paper
which is dyed with nonuniform intensity. A mixture which contains
at least one surfactant and at least one pigment is applied
nonuniformly to a paper, i.e. not over the entire surface, a latent
image or pattern forming. In a subsequent step, the paper is
nonuniformly dyed by application of a dye solution and then dried.
What is essential here is that the mixture of surfactant and
pigment is applied to the paper not uniformly but only in the areas
where a pattern is to be subsequently recognizable. The changed
coloring may be both a more intense and a less intense coloring in
comparison with the untreated surface of the paper. European Patent
Application 03 000 835.3 does not disclose that the mixture of
surfactant and pigment is applied to a paper substrate over the
entire surface.
[0011] The object of the present invention is to provide a paper
which combines the good printability of coated papers with the
haptic properties and the visual impression of the natural papers.
In particular, the papers should be improved compared with papers
produced to date in such a way that very good printability by a
very wide range of printing processes can be achieved, in
particular by offset printing, digital printing and inkjet
printing. Otherwise, the properties peculiar to the natural papers
should be retained.
[0012] The technical object of the present invention is achieved by
a paper comprising: [0013] a) a paper substrate and [0014] b) a
preparation applied to at least one side of the paper substrate
over the entire surface and containing a surfactant and at least
one pigment having a particle diameter of from 1 to 500 nm, the
preparation containing a binder in a ratio to the pigment of not
more than 5 parts by weight of binder:100 parts by weight of
pigment (based in each case on the solids content).
[0015] It was found that the printability in the customary printing
processes is improved if such a preparation penetrates into the
paper substrate, the haptic properties and the visual impression of
the natural paper simultaneously being retained. The preparation
completely or virtually completely encloses mainly the fibers
localized at the surface of the paper substrate.
[0016] An advantage is that the natural paper of the present
invention can be produced on units which are customary in the paper
industry, so that no additional production units are required. It
is furthermore advantageous that the natural paper of the present
invention can be recycled so that it can be disintegrated in
customary plants, such as, for example a pulper, and can be used
again for the further production of paper.
[0017] In the context of this invention, the term paper is to be
understood as meaning the finished, printable paper. It can be
present both as continuous product/product on reels and as product
cut to size. The paper comprises a paper substrate as support
material and a preparation applied to at least one side of the
paper substrate. The coating is a layer which is optionally applied
to the side of the paper substrate on which the preparation is
present. If coat weights are stated they relate to the applied mass
per unit area after conditioning to constant weight at 110.degree.
C. (absolutely dry). Preferred embodiments will be discussed
below.
[0018] In a preferred embodiment, the preparation can be applied to
both sides of the paper substrate, i.e. to the top and the bottom
of the paper substrate, over the entire surface.
[0019] The preparation may have an overall anionic, cationic or
neutral charge.
[0020] In a preferred embodiment, the preparation has a coat weight
of 0.5-20 g/m.sup.2 (absolutely dry) per side. Preferably 1-15
g/m.sup.2, more preferably 2-10 g/m.sup.2 and particularly
preferably 3-7 g/m.sup.2 of preparation are present on at least one
side of the paper substrate, over the entire surface.
[0021] Preferably 0.05-2.5 g/m.sup.2 (absolutely dry) of surfactant
are present per side in the preparation. A preferred embodiment
comprises 0.1-2.0 g/m.sup.2, more preferably 0.2-1.5 g/m.sup.2 and
most preferably 0.3-0.7 g/m.sup.2 of surfactant in the
preparation.
[0022] The surfactant can preferably be an anionic, cationic,
nonionic or amphoteric surfactant.
[0023] For example, suitable surfactants can be selected from (1)
hydrophilic polydialkylsiloxanes, (2) polyalkylene glycol, (3)
polypropylene oxide/polyethylene oxide copolymers, (4) fatty acid
ester-modified compounds of phosphate, sorbitan, glycerol,
polyethylene glycol, sulfosuccinic acids, sulfonic acid or
alkylamine, (5) polyoxyalkylene-modified compounds of sorbitan
esters, fatty amines, alkanolamides, castor oil, fatty acid, fatty
alcohol, (6) quaternary alcohol sulfate compounds, (7) fatty
imidazolines, (8) polyether-modified trisiloxanes and (9) mixtures
thereof.
[0024] Specific examples of water-soluble or alcohol-soluble
surfactants from the abovementioned classes of substances are, for
example, (1) poly(oxyalkylene) modifications of (a) sorbitan esters
(e.g. Alkamuls PSML-4 (poly(oxyethylene)sorbitan monolaurate),
Alkamuls PSMO-20 (poly(oxyethylene)sorbitan monooleate), Alkamuls
PSTO-20 (poly(oxyethylene)sorbitan trioleate), Alkaril Chemicals);
(b) fatty amines (e.g. Alkaminox T-2, T-5 (tallow aminoxyethylate),
Alkaminox SO-5(soya bean aminoxyethylate), Alkaril Chemicals,
(Icomeen T-2, Icomeen T-15, ICI Chemicals); (c) castor oil (e.g.
Alkasurf CO-10, Alkasurf CO-25B (castor oil oxyethylates), Alkaril
Chemicals); (d) alkanolamide (e.g. Alkamide C-2, C-5 (coconut oil
alkanolamide oxyethylates), Alkaril Chemicals); (e) fatty acids
(e.g. Alkasurf 075-9, Alkasurf 0-10, Alkasurf 0-14 (oleic acid
oxyethylates), Alkasurf L-14 (lauric acid oxyethylates), Alkasurf
P-7 (palmitic acid oxyethylates) Alkaril Chemicals); (f) fatty acid
alcohol (e.g. Alkasurf LAN-1, LAN-3, Alkasurf TDA-6, Alkasurf SA-2,
(linear alcohol oxyethylates), Alkasurf NP-1, NP-11, Rexol 130
(nonylphenol oxyethylates), Alkasurf OP-1, OP-12 (octylphenol
oxyethylates), Alkasurf LA-EP-15, Alkasurf LA-EP-25, Alkasurf
LA-EP-65 (linear alcohol oxyalkylates)); (2) hydrophilic
poly(dimethylsiloxanes) such as, for example, (a)
poly(dimethlysiloxane) provided with a monocarbinol terminal group
(PS558, Petrarch Systems Inc.) and poly(dimethylsiloxane) provided
dicarbonol terminal group (PS555, PS556, Petrarch Systems Inc.);
(b) poly(dimethylsiloxane)-b-poly(methylsiloxanalkylene oxide)
copolymers (PS 073, PS 072, PS 071, Petrarch Systems Inc.), Alkasil
HEP 182-280, Alkasil HEP 148-330 (Alkaril Chemicals),
nonhydrolyzable co-polymers containing Si--C-bonds; (c)
poly(dimethylsiloxane)-b-poly(propylene oxide)-b-poly(ethylene
oxide) copolymers (Alkasil NEP 73-70, Alkaril Chemicals) a
hydrolyzable copolymer containing Si--O--C-bonds; (d)
polyquaternary poly(dimethylsiloxane) copolymers (which can be
obtained by the addition reaction of an
.alpha.,.omega.-hydrogenpolysiloxane with epoxides containing
olefinic bonds and subsequent reaction of a product with a
diamine); (3) fatty imidazolines and their derivatives, such as for
example, (a) Alkazine-O (oleyl derivative); (b) Alkazine TO (tall
oil derivatives); (c) Alkateric 2C1B (dicarboxylic acid
cocosimidazoline sodium salt) Alkaril Chemicals; (d) Arzoline-4;
(e) Arzoline-215, Baker Chemicals; (4) fatty acid esters of (a)
phosphates (e.g. Alkaphos B6-56A, Alkaril Chemicals); (b) sorbitan
(e.g. Alkamuls STO (sorbitan trioleate), Alkamuls SML (sorbitan
monolaurate), Alkamuls SMO (sorbitan monooleate), Alkaril
Chemicals); (c) glycerol compounds (e.g. Alkamuls GMO-45LG
(glyceryl monooleate), Alkamuls GDO (glyceryl dioleate), Alkamuls
GTO (glyceryl trioleate); (d) poly(ethylene glycols) (Alkamuls 600
DO (dioleate), Alkamuls 400-ML (monolaurate), Alkamuls 600 MO
(monooleate), Alkamuls 600 DL (dilaurate), Alkamuls 600 DT
(ditallow), Alkaril Chemicals); (e) sulfosuccinic acid (e.g.
Alkasurf SS-O-75 (sodium dioctylsulfosuccinate), Alkasurf SS-DA4-HE
(oxyethylated alcohol sulfosuccinate), Alkasurf SS-L7DE (sodium
sulfosuccinate ester of lauric acid diethanolamide), Alkasurf
SS-L-HE (sodium laurylsulfosuccinate), Alkaril Chemicals); (f)
sulfonic acid (e.g. Alkasurf CA (calcium dodecylbenzenesulfonate),
Alkasurf IPAM (isopropylamine dodecylbenzenesulfonate), Alkaril
Chemicals); (g) alkylamines (e.g. Alkamide SDO (soya bean
diethanolamide), Alkamide CDE (coconut diethanolamide), Alkamide
2104 (coconut fatty acid diethanolamide), Alkamide CMA (coconut
monoethanolamide), Alkamide L9DE (lauryl diethanolamide), Alkamide
L7Me (lauryl monoethanolamide), Alkamide L1PA (lauryl
monoisopropylamide), Alkaril Chemicals); (5) quaternary compounds,
such as, for example, (a) non-polymeric quaternary ammonium
ethosulfate (e.g. Finquat CT, Cordex T-172, Finetex Corporation);
(b) quaternary dialkyldimethylmethosulfate (e.g. Alkaquat DHTS
(hydrogenated tallow)); (c) alkoxylated quaternary di-fatty
methosulfate (e.g. Alkasurf DAET (tallow derivative)); (d)
quaternary fatty idazoline methosulfate (e.g. Alkaquat T (tallow
derivatives), Alkaril Chemicals); (6) water-soluble copolymers of
lipophilic poly(propylene oxide) with hydrophilic
poly(ethyleneoxide) such as, for example, (a) methanol-soluble
Tetronic 150R1, Pluronic L-101, Tetronic 902, Tetronic 25R2 (BASF
Corporation), Alkatronic EGE-1 (Alkaril Chemicals); (b)
water-soluble Tetronic 908, 50R8, 25R8, 904, 90R4, Pluronic F-77,
all from BASF Corporation, and Alkatronic EGE 25-2 and PGP 33-8
from Alkaril Chemicals; (7) poly(alkylene glycol) and its
derivatives, such as, for example (a) polypropylene glycol (Alkapol
PPG 425, Alkapol PPG-4000, Alkaril Chemicals); (b) poly(propylene
glycol dimethacrylate), poly(ethylene glycol diacrylate),
poly(ethylene glycol dimethacrylate), poly(ethylene glycol
monomethyl ether), poly(ethylene glycol dimethyl ether),
poly(ethylene glycol diglycidyl ether) (all from Polysciences); (c)
poly(1,4-oxybutylene glycol) (Scientific Polymer Products) and the
like.
[0025] Preferred surfactants include linear alcohol oxyethylates
(e.g. Alkasurf LA-EP-65, LA-EP-25 and LA-EP-15 obtainable from
Alkaril Chemicals), nonylphenol oxyethylates (e.g. Alkasurf NP-11
obtainable from Alkaril Chemicals and Rexol 130 obtainable from
Hart Chemicals), octylphenol oxyethylates (e.g. Alkasurf OP-12
obtainable from Alkaril Chemicals), oleic acid oxyethylates (e.g.
Alkasurf O-14 obtainable from Alkaril Chemicals),
poly(dimethylsiloxane)-b-poly(propylene oxide)-b-poly(ethylene
oxide) co-polymers (e.g. Alkasil NEP 73-70 obtainable from Alkaril
Chemicals), castor oil ethoxylates (e.g. Alkasurf CO25B obtainable
from Alkaril Chemicals), cocosimidazolinedicarboxylic acid sodium
salts (e.g. Alkateric 2C1B obtainable from Alkaril Chemicals) and
coconut fatty acid diethanolamide (e.g. Alkamid S104 obtainable
from Alkaril Chemicals). The Alkasurf surfactants are
advantageously biodegradable.
[0026] Further preferred surfactants are fatty alcohols modified
with ethylene oxide/propylene oxide, and modified fatty alcohol
polyglycol ethers, such as, for example, Hydropalat.RTM. 120 XP
(obtainable from Cognis/Henkel)
[0027] Preferably 0.1-19.5 g/m.sup.2 (absolutely dry) of pigment
are present in the preparation. Preferably from 0.2 to 19.3
g/m.sup.2, more preferably from 0.3 to 18.5 g/m.sup.2 particularly
preferably from 0.4 to 18 g/m.sup.2 and most preferably from 0.45
to 17.5 g/m.sup.2 of pigment are present in the preparation. The
pigment can preferably have an overall cationic and/or anionic
and/or nonionic charge. In the context of this invention, anionic
pigments are those pigments in which the surface of the pigment has
an overall anionic charge. Cationic pigments are those pigments in
which the surface of the pigment has an overall cationic charge.
Nonionic pigments are those pigments in which the surface of the
pigments has an overall neutral or substantially neutral
charge.
[0028] The pigment is preferably an oxide and/or mixed oxide of a
metal. However, it may also be the oxide and/or mixed oxide of a
semimetal/semiconductor.
[0029] The pigments used in the preparation preferably have a large
specific BET surface area of, preferably, from 50 to 800 m.sup.2/g
and more preferably from 100 to 400 m .sup.2/g. The pigment
particles themselves have a diameter of 1-500 nm, preferably 10-100
nm and more preferably 20-70 nm.
[0030] The pigments can preferably be selected from the group
consisting of oxides of metals or semimetals, such as, for example,
silicon, magnesium, calcium, aluminum, zinc, chromium, iron,
copper, tin or lead. Preferred pigments are silicas, gibbsite,
bayerite, nordostrandite, boehmite, pseudoboehmite, diaspore,
aluminas, preferably corundum, aluminum hydroxide, magnesium
silicate, basic magnesium carbonate, titanium dioxide, tin oxide,
aluminum silicate, calcium carbonate, talc, clay, hydrotalcite,
silica, colloidal silica, precipitated silica, inorganic
substances, such as, for example, diatomite, organic substances,
such as, for example, resin-like pigments comprising
melamine/formaldehyde resins, urea/formaldehyde resins, ethylene
resins, styrene resins, acrylate resins or combinations
thereof.
[0031] Colloidal suspensions of SiO.sub.2 particles, which are
preferably non porous SiO.sub.2 particles can also be used as
pigment. The suspension can have an anionic or cationic charge.
Here, the particle size of the SiO.sub.2 particles can vary from 1
to 100 nm, the particle size preferably being from 10 to 50 nm. The
Cartacoat.RTM. K grades from Clariant, in particular Cartacoat.RTM.
301A liquid, Cartacoat.RTM. 302A liquid, Cartacoat.RTM. 302C liquid
and Cartacoat.RTM. 303A liquid, may be mentioned by way of example
for this class of pigments. Alternatively, anionic or cationic
colloidal silica, which is sold under the trade name Ludox.RTM. CL
or Ludox.RTM. TMA by Grace-Davison, can be used.
[0032] Preferably at least one additive may be present in the
preparation. Additives which may be used are those which are
familiar to the person skilled in the art, such as, for example,
rheology modifiers, viscosity regulators (thickeners), dyes or
brighteners. If a viscosity regulator is used, it is preferable to
use crosslinked modified polyacrylates, such as, for example,
Cartacoat.RTM. MS liquid, obtainable from Clariant. According to
the invention, however, the preparation contains a binder in a
ratio of binders to pigment (based in each case on solids content)
of hot more than 5:100, preferably not more than 3:100,
particularly preferably not more than 2:100, in order to obtain the
haptic properties of natural paper.
[0033] The binders used are preferably those which do not have a
crosslinking effect, so that no solidification of the applied
preparation layer occurs. In the strict sense, according to the
invention no "binder" is used in the preparation but preferably
thickeners or viscosity regulators, which, however, can also be
used as binders in papermaking, such as, for example, cellulose
(types), such as carboxymethylcellulose (CMC), are used for
adjusting the flowability of the preparation. The thickeners are,
however, used in amounts which are so small that they do not act as
binders in the preparation, i.e. do not bind the pigments to one
another and/or the pigments to the paper substrate, but merely
adjust the viscosity and flowability of the preparation to be
applied to a desired value. Such thickeners or viscosity regulators
are generally known to the person skilled in the art in the area of
papermaking. According to the invention, the thickeners do not have
to meet any particular requirement. The amount of the thickener
used is in the customary range in which such agents are used and
depends on the properties of the thickener used.
[0034] According to the invention, binder for the purpose of
binding the pigments to one another and to the paper substrate is
not used in the preparation. Even if a thickener which is also
suitable as a binder is used, it is present only in amounts which
do not permit binding as described above. Such a preparation
without "binder" used for the purpose of binding improves the
printability of the paper substrate without substantially changing
the haptic properties, so that said properties substantially
correspond to those of natural paper.
[0035] The paper substrate preferably contains a filler. It is
preferable if the filler has a cavity volume. The cavity volume of
the filler can preferably be measured by the oil number of the
filler, according to DIN EN ISO 787-5.
[0036] According to DIN EN ISO 787-5, the filler preferably has an
oil number of 10-150 g/100 g of filler, more preferably of 30-80
g/100 g of filler and particularly preferably of 30-70 g/100 g of
filler.
[0037] The filler can preferably be selected from the group
consisting of chalk, precipitated chalk, clay, talc, calcined clay,
alumina, aluminum hydroxide, gypsum, hydrated alumina, silica,
silicic acid, diatomaceous earth, titanium dioxide, and mixtures
thereof. The filler may furthermore preferably have an overall
anionic or an overall cationic charge.
[0038] The proportion of filler in the paper substrate is
preferably 3-30% by weight, based on the total weight of the paper
substrate after conditioning at a constant weight at 110.degree. C.
(absolutely dry). Preferably, the proportion of filler is 5-25% by
weight, more preferably 7-20% by weight, particularly preferably
9-18% by weight and most preferably 10-15% by weight.
[0039] The paper substrate can preferably contain at least one
additive. Preferred additives are wet strength agents, starches,
antifoams, retention aids, brighteners, dyes and mixtures thereof.
In a preferred embodiment, the paper substrate contains a
proportion of wet strength agents which makes it possible to
moisten the paper substrate again in the subsequent processing
steps without the strength being reduced by water absorption to
such an extent that the paper web tears during subsequent
processing steps.
[0040] The paper substrate may contain all fibers customary for the
person skilled in the art, such as, for example, chemical pulp or
groundwood. Preferably, the paper substrate contains a mixture of
long-fiber and short-fiber chemical pulps.
[0041] The paper preferably has a basis weight, varied according to
ISO 536, of from 40 to 400 g/m.sup.2. The basis weight is
preferably from 60 to 300 g/m.sup.2, more preferably from 70 to 280
g/m.sup.2 and most preferably from 80 to 250 g/m.sup.2.
[0042] The preparation can be applied at least to one side of the
paper substrate online, i.e. within the paper machine, to the paper
substrate. Preferred coating units are the size press coating units
similar to the size press, the film press, the billblade, the
curtain coater, the airbrush, the blade, doctor blade coating and
spray coating.
[0043] It is however also possible to apply the preparation at
least to one side of the paper substrate in a finishing step
downstream of the production of the paper substrate. This can be
effected by means of coating units which are familiar to the person
skilled in the art, such as, for example, by means of a size press,
a coating unit similar to the size press, a film press, a blade, an
airbrush, a doctor blade, a curtain coater, a spray coater or a
reverse gravure coating unit.
[0044] Unexpectedly, the preparation improves the printability of
the paper substrate without having a substantial or detectable
disadvantageous influence on the optical or the haptic properties
of the paper substrate. The paper substrate retains or virtually
retains the visual and haptic impression of an untreated natural
paper. The preparation penetrates over the entire surface and
uniformly into the surface of the paper substrate and thereby
unexpectedly prevents the irregularity of a subsequently applied
print, which irregularity is otherwise caused by the peaks and
valleys of the paper surface. Thus, for example, in offset
printing, the ink application is uniform. An indication of this is
the so-called mottling of the printed paper. The mottling indicates
how homogeneous the printout in offset printing on the paper is.
With a paper of the present invention, the homogeneity of the
offset print is comparable with the homogeneity of the offset print
on a coated paper. Furthermore, the paper of the present invention
has a stiffness and a volume which are comparable with untreated
and uncoated papers.
[0045] In a further embodiment, at least one further coating may be
present on the preparation on the same side of the paper substrate
on which the preparation is applied.
[0046] The coating preferably contains at least one pigment and at
least one binder.
[0047] In a preferred embodiment, the applied pigment has a
particle diameter of from 1 to 500 nm and can preferably be
selected from the group consisting of oxide and/or mixed oxide of a
metal, oxide and/or oxide of a semi-metal/semiconductor and
mixtures thereof. More preferably, it is possible to use all
pigments which can also be used as a pigment in the
preparation.
[0048] The coating can preferably contain at least one further
additive. Additives which may be used are all additives which are
familiar to the person skilled in the art, such as, for example,
binders, viscosity regulators (thickeners), brighteners, antifoams,
dyes, dispersants and surfactants. Surfactants which may be used
are all surfactants which are familiar to the person skilled in the
art, and preferably the surfactants which are used in the
preparation. Furthermore, it is possible to use all viscosity
regulators which can also be used in the preparation. The coating
preferably has a coat weight of 0.5-20 g/m.sup.2 (absolutely dry)
per side. Preferably, the coat weight of the coating is 2-15
g/m.sup.2, more preferably 3-12 g/m.sup.2 and most preferably 3-10
g/m.sup.2. The coat weight of the coating is preferably such that
the surface of the paper substrate on which the preparation is
present is homogeneously wetted by the coating.
[0049] The coating can be applied to both sides of the paper
substrate if a preparation is present on both sides of the paper
substrate. However, if a preparation is present on both sides of
the paper substrate, it is also possible for the coating to be
applied on the preparation only on one side of the paper
substrate.
[0050] The coating may have an overall anionic, cationic or neutral
charge. Preferably, the coating has an overall anionic charge if
the preparation has an overall cationic charge, or the coating
preferably has an overall cationic charge if the preparation has an
overall anionic charge.
[0051] The coating can be applied using any coating unit which is
familiar to the person skilled in the art. Furthermore, the coating
can be applied within the paper machine (online), i.e. during the
production of the paper substrate. However, it is just as possible
to apply the coating after production of the paper substrate in a
subsequent processing step. Suitable coating units are, for
example, the size press, coating units similar to the size press,
the film press, the blade coater, the airbrush, the doctor blade,
the curtain coater and the spray coater.
[0052] All abovementioned papers (with or without the coating) can
furthermore be subjected to aftertreatment steps. Thus, the surface
of the paper can be further calendered. This can be effected by a
smoothing unit, a matt calender, a calender or a brush calender.
Those processes in which the smoothness of the paper is increased
without the volume of the paper being substantially reduced by this
step are advantageous. Alternatively, the surface contour of the
paper can be changed by an embossing step. For example, an
embossing calender is suitable for this purpose. The surface
structure can be changed on both sides of the paper or only on one
side of the paper, which is preferably the side on which the
preparation is present.
[0053] All abovementioned papers can be used as a print medium in
printing processes which are familiar to the person skilled in the
art. It is preferable if the printing process is selected from the
printing processes consisting of offset printing, digital printing,
inkjet printing, gravure printing, flexographic printing, newspaper
printing, relief printing, letterpress printing, sublimation
printing, laser printing, electrophotographic printing processes
and combinations of the abovementioned printing processes.
[0054] By applying the coating to that side of the paper substrate
on which the preparation is present, the printability of the paper
is further improved. Unexpectedly, however, the character of the
paper is not changed or not substantially changed by the coating.
Both the appearance and the haptic properties of the paper are not
adversely influenced or not substantially adversely influenced by
the coating. The paper retains the character of an uncoated paper.
In comparison with untreated papers, however, the printing quality
is significantly improved.
[0055] The present invention is explained below with reference to
the following examples, without it being intended to limit it
thereto.
EXAMPLES
1. Preparations
1.1. Production of the Preparations 1 to 3
[0056] Tylose.RTM. H60000 YP2 is dissolved with stirring in the
amount of water stated in Table 1 for establishing the desired
viscosity. After a clear solution has been obtained,
Hydropalat.RTM. 120 EXP is added. The corresponding pigment slurry
is then added. Stirring is effected for a further 30 minutes in
order to obtain the preparations 1-3. TABLE-US-00001 TABLE 1
Ingredients Preparation 1 Preparation 2 Preparation 3 Tylose .RTM.
H60000 YP2.sup.1 0.1 g 0.1 g 0.1 g Hydropalat .RTM. 120 EXP.sup.2
0.5 g 0.5 g 0.5 g Ludox .RTM. CL.sup.3 24.6 g Cartacoat .RTM. K
301A liquid.sup.4 24.6 g Ludox .RTM. TMA.sup.5 21.8 g Water 80 g 80
g 80 g .sup.1Tylose .RTM. H60000 YP2: carboxymethylcellulose having
a molecular weight of 60000 u (Clariant). .sup.2Hydropalat .RTM.
120 EXP: nonionic surfactant based on EO/PO-modified fatty alcohol,
modified fatty alcohol polyglycol ether (Cognis/Henkel).
.sup.3Ludox .RTM. CL: cationic colloidal suspension of silica in
water (30% by weight of SiO.sub.2; Grace Davison). .sup.4Cartacoat
.RTM. K 301A liquid: colloidal suspension of nonporous SiO.sub.2
particles (pH 10, 30% of SiO.sub.2, particle size 12 nm, Clariant).
.sup.5Ludox .RTM. TMA: anionic colloidal silica in water (34% by
weight of SiO.sub.2; Grace Davison)
1.2. Application of the Preparations 1 to 3 to a Paper
Substrate.
[0057] A paper provided with a neutral size and having a basis
weight of 120 g/m.sup.2 (filler content 15%, filled with PRECARB
200 (Schafer Kalk), precipitated CaCO.sub.3, oil number (measured
according to DIN EN ISO 787-5) 65 g/100 g of powder) is immersed in
one of the preparations 1 to 3. The excess amount of preparation is
squeezed out between two rubber rolls and the paper is then dried
by means of a photodrier (heated metal roll around which a textile
web runs; for drying, the paper is introduced into the nip between
metal roll and textile web). The coat weight of the preparation on
the paper substrate is 3 g/m.sup.2 (absolutely dry) per side.
1.3. Assessment of the Printability
[0058] The paper substrates provided with the preparations 1 to 3
and, as a comparison, the untreated paper substrate, and a
commercially available, coated paper (150 g/m.sup.2 total weight,
surface-treated, 20 g/m.sup.2 of a pigment coat are applied to each
side of the paper), are printed on one side using a Prufbau
apparatus with a blue printing ink. The homogeneity and intensity
of the printed blue area is then visually assessed, the rating 1
denoting very good homogeneity and intensity of the printed blue
area and the rating 6 denoting insufficient homogeneity and
intensity of the printed blue area. The assessment is shown in
Table 2. TABLE-US-00002 TABLE 2 Sample Homogeneity and intensity
rating Preparation 1 1-2 Preparation 2 1-2 Preparation 3 1-2 Paper
substrate (comparison) 5 Commercially available coated paper 1
(comparison)
[0059] The commercially available, coated paper received the rating
1 and thus shows very good printability, whereas the paper
substrate has only inadequate printability (rating 6). On the other
hand, when it was provided with one of the preparations 1 to 3, the
paper substrate unexpectedly shows a printability which has the
rating 1-2 and is thus only insignificantly poorer than the
printability of the coated paper. Nevertheless, the haptic
properties and the visual impression of the paper substrate
provided with the preparations are not changed or not significantly
changed.
2. Coatings
2.1. Production of the Coatings 1 to 4
[0060] Acronal 500D.RTM. and Mowiol.RTM. 8/88 solution are added
with stirring to the amount of water stated in Table 3. Thereafter,
the corresponding pigment slurry and, in the case of the coating 1,
additionally Cartacoat.RTM. MS liquid are added. Stirring is
effected for a further 30 minutes in order to obtain the coatings 1
to 4. TABLE-US-00003 TABLE 3 Ingredients Coating 1 Coating 2
Coating 3 Coating 4 Ludox TMA 250 g Cartacoat .RTM. K301A 600 g
Cartacoat .RTM. K302C.sup.6 400 g Cartacoat .RTM. K303A.sup.7 400 g
Cartacoat .RTM. MS fl..sup.8 0.34 g Acronal 500D .RTM..sup.9 6.8 g
14.4 g 9.6 g 19.2 g Mowiol .RTM. 8/88 5.7 g 12.0 g 8.0 g 16.0 g
solution.sup.10 Water 94.7 g 129.6 g 86.4 g 92.8 g .sup.6Cartacoat
.RTM. 302C: cationic colloidal suspension of nonporous SiO.sub.2
particles (pH 4, 30% of SiO.sub.2, particle size 25 nm, Clariant)
.sup.7Cartacoat .RTM. 303A: colloidal suspension of nonporous
SiO.sub.2 particles (pH 9, 30% of SiO.sub.2, particle size 50 nm,
Clariant) .sup.8Cartacoat .RTM. MS liquid: crosslinked modified
polyacrylate (37% solids content) .sup.9Acronal 500D .RTM.: aqueous
dispersion of a polystyrene/vinyl acetate copolymer (50% by weight,
BASF AG) .sup.10Mowiol .RTM. 8/88 solution: 15% strength polyvinyl
alcohol solution, 15% strength solution of Mowiol .RTM. 8/88
(Clariant) in water.
2.2. Application of the Coatings 1 to 4 to a Paper Substrate which
was Treated with One of the Preparations 1-3
[0061] A paper substrate provided according to 1.2 with one of the
preparations 1 to 3 is immersed in one of the coatings 1 to 4. The
excess amount of coating is squeezed out between two rubber rolls,
and the paper is then dried by means of a photodrier (heated metal
roll around which a textile web runs; for drying, the paper is
introduced into the nip between metal roll and textile web). The
coat weight of the coating on the paper substrate provided with the
preparation is 3 g/m.sup.2 (absolutely dry) per side.
2.3. Assessment of the Printability
[0062] The paper substrates provided with the preparations 1 to 4
and, as a comparison, the untreated paper substrate, and a
commercially available, coated paper (150 g/m.sup.2 total weight,
surface-treated, 20 g/m.sup.2 of a pigment coat are applied to each
side of the paper), are printed on one side using a Prufbau
apparatus with a blue printing ink. The homogeneity and intensity
of the printed blue area is then visually assessed, the rating 1
denoting very good homogeneity and intensity of the printed blue
area and the rating 6 denoting insufficient homogeneity and
intensity of the printed blue area. The assessment is shown in
Table 4. TABLE-US-00004 TABLE 4 Homogeneity and intensity Sample of
the print Preparation Coating Rating Preparation 1 Coating 1 1
Coating 2 1 Coating 3 1 Coating 4 1 Preparation 2 Coating 1 1
Coating 2 1 Coating 3 1 Coating 4 1 Preparation 3 Coating 1 1
Coating 2 1 Coating 3 1 Coating 4 1 Paper substrate (comparison) 5
Commercially available coated paper (comparison) 1
[0063] The commercially available coated paper has the rating 1 and
thus shows very good printability, whereas the paper substrate has
only inadequate printability (rating 5). On the other hand, when it
was provided with one of the preparations 1 to 3 and then with one
of the coatings 1 to 4, the paper substrate unexpectedly shows a
printability which has the rating 1 and is thus comparable with the
printability of the coated paper. Nevertheless, the haptic
properties and the visual impression of the paper substrates
provided with the preparations and coatings are not changed or not
significantly changed.
* * * * *