U.S. patent application number 10/432520 was filed with the patent office on 2004-05-20 for process for the production of a coated and pressed cellulosic fibrous flat substrate, suitable coating compositions, their production, the coated and pressed substrates and their use as substrates for graphic processes.
Invention is credited to Myatt, Scott.
Application Number | 20040094279 10/432520 |
Document ID | / |
Family ID | 9904081 |
Filed Date | 2004-05-20 |
United States Patent
Application |
20040094279 |
Kind Code |
A1 |
Myatt, Scott |
May 20, 2004 |
Process for the production of a coated and pressed cellulosic
fibrous flat substrate, suitable coating compositions, their
production, the coated and pressed substrates and their use as
substrates for graphic processes
Abstract
The invention provides a process for the production of a coated
and pressed cellulosic fibrous flat substrate of loose, optionally
bonded fibers, by application of (M) an aqueous coating
composition, containing a binder (B), a white pigment (W) and a
dispersant (D), wherein at least a part of the white pigment (W) is
(A) a particulate ammonium polyphosphate of crystalline form II of
average particle size<40 .mu.m and with a water solubility<10
g/l at 25.degree. C., to the face of the substrate and subjecting
to pressure, in particular for the production of coated and pressed
substrates of outstanding surface properties, particularly suitable
for graphic processing, and of outstanding non-flammability
properties, suitable coating compositions, their production, the
coated and pressed substrates and their use as substrates for
graphic processes, especially printing.
Inventors: |
Myatt, Scott; (Yorkshire,
GB) |
Correspondence
Address: |
CLARIANT CORPORATION
INTELLECTUAL PROPERTY DEPARTMENT
4000 MONROE ROAD
CHARLOTTE
NC
28205
US
|
Family ID: |
9904081 |
Appl. No.: |
10/432520 |
Filed: |
May 23, 2003 |
PCT Filed: |
November 28, 2001 |
PCT NO: |
PCT/IB01/02256 |
Current U.S.
Class: |
162/135 ;
106/18.15; 106/18.16; 162/158; 162/159; 162/162; 162/181.1 |
Current CPC
Class: |
D21H 19/38 20130101;
C09K 21/14 20130101; C09K 21/04 20130101; D21H 21/34 20130101; D21H
21/52 20130101 |
Class at
Publication: |
162/135 ;
162/158; 162/181.1; 162/159; 162/162; 106/018.15; 106/018.16 |
International
Class: |
D21H 019/38; D21H
023/22 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 29, 2000 |
GB |
0029071. |
Claims
1. Process for the production of a coated and pressed cellulosic
fibrous flat substrate of loose, optionally bonded fibers, by
application of (M) an aqueous coating composition, containing a
binder (13), a white pigment (W) and a dispersant (D), wherein at
least a part of the white pigment (W) is (A) a particulate ammonium
polyphosphate of crystalline form II of average particle size<40
.mu.m and with a water solubility<10 .mu.g/l at 25.degree. C.,
to the face of the substrate and subjecting to pressure.
2. A process according to claim 1, wherein the average particle
size of (A) is <25 .mu.m, with no particles exceeding the size
of 40 .mu.m.
3. A process according to claim 1 or 2, wherein the cellulosic
fibrous substrate is a non-woven substrate selected from a web of
paper, paperboard, board or non-woven tissue.
4. A process according to any one of claims 1 to 3 for coating and
flame-proofing, wherein (A) is present in a concentration efficient
for providing a flame-proofing action.
5. A process according to any one of claims 1 to 4, wherein (A) is
present in a concentration.gtoreq.4% by weight of (W).
6. A process according to any one of claims 1 to 5, wherein (W)
comprises (A) and a white mineral pigment (P) and/or a melamine
(poly)phosphate (L).
7. A process according to any one of claims 1 to 6, wherein (M)
further contains one or more further additives selected from (C)
which is (C.sub.1) at least one optical brightener and/or (C.sub.2)
at least one dyestuff, (E) a thickening agent, (F) at least one
resin other than (B) and (G) at least one formulation additive
suitable modifying or maintaining the physical form of the
composition.
8. A process according to any one of claims 1 to 7 wherein (G) is
selected from (G.sub.1) an anti-microbic agent, (G.sub.2) a
defoamer, (G.sub.3) a flow agent and/or (G.sub.4) an acid, base
and/or buffer for pH-adjustment.
9. A coating composition (M) as defined in claim 2.
10. A coating composition (M) according to claim 9, further defined
as in any one of claims 4 to 8.
11. A process for the production of a coating composition (M)
according to claim 9 or 10, wherein (W) is mixed at a
temperature.ltoreq.35.degree. C. with water and optionally
(G.sub.3), then with (D) and then with (B) and optionally with any
further of the components (C), (E), (F) and (G).
12. A cellulosic fibrous flat substrate of loose, optionally bonded
fibers coated with (M) by a process according to any one of claims
1 to 8.
13. A cellulosic fibrous substrate according to claim 12, which is
a coated paper, paperboard, board or non-woven tissue.
14. Use of a cellulosic fibrous flat substrate of loose, optionally
bonded fibers, coated with (M) by a process according to any one of
claims 1 to 8, as a substrate for a graphic process.
15. A process for the production of a cellulosic fibrous flat
substrate of loose, optionally bonded fibers, which has been
graphically processed, in particular written on, printed and/or
graphically processed in any other manner by application of at
least one graphic ink pattern to said substrate, and drying, which
is characterized in that the substrate used for this purpose is a
cellulosic fibrous flat substrate of loose, optionally bonded
fibers, coated with (M) according to claim 12 or 13.
Description
[0001] In the production of coatings on webs of loose, optionally
bonded fibrous material, especially on paper, a coating composition
is usually applied to the web of paper or other fibrous material
and is pressed e.g. with a plate or through press rolls or by other
means, in order to obtain a surface with certain physical and
aesthetic properties such as gloss, strength, pliability and
printability.
[0002] Since many fibrous materials, especially cellulosic
materials, and/or any compounds with which they have been treated,
may be flammable, it is often desired to treat them with a flame
retarding agent. In the case of webs of fibrous material, mainly
paper, such a treatment may be carried out by adding a flame
retardant to the paperstuff of which the paper is then made, or in
a size composition with which the paper is impregnated. For the
production of a coated paper the coating is then applied on the so
pretreated paper which is then subjected to pressure e.g. plate- or
roll-pressed. By this the applied coating--which may itself be
flammable--may however constitute a delaying hindrance for the
flame retarding effect in the substrate.
[0003] According to another way of application a flame retarding
paint may be applied to the substrate after it has been finished
(either uncoated or coated, as mentioned above) so that, when
applied on a coated substrate, this paint may impair the aesthetic
aspect and also some of the physical properties which were provided
by the previously applied coating (such as gloss or printability)
or, when applied on an uncoated substrate, it may not replace a
coating (or "enamel") because of its different way of application
and mostly also because of its different composition. The
application of such paints is sometimes also designated as
"coating", but this term signifies in this case only that the paint
is applied as a continuous film, and this is usually directly dried
after its application without subjecting it to a particular
pressure treatment.
[0004] In U.S. Pat. No. 5,049,187-A there are described fire
retardant aqueous coating solutions for use in forming a fire
retardant protective overcoat on a surface requiring such
protection, which are comprised of 1) a water soluble film-forming
cross-linkable copolymer of methyl vinyl ether and maleic
anhydride, 2) a water-soluble polyhydric alcohol which serves to
cross-link the copolymer when a coating of the composition is
applied over the surface and dried, and 3) a water-soluble ammonium
polyphosphate; these compositions are useful for forming a
transparent overcoat in particular for photographic elements,
AMGARD PI of Albright & Wilson Americas Inc. being mentioned
among others as an example of an ammonium polyphosphate component
3).
[0005] EP-460516-A and GB-2243846-A relate to flame retardant
aqueous compositions comprising an ammonium polyphosphate, a
defined heat-curable resin and some defined further components (the
same AMGARD PI as above being mentioned as an example of the
ammonium polyphosphate).
[0006] These compositions on standing form a gel which on shearing
forms a pourable emulsion which on application to a fabric under
shearing then regels rapidly. They are applied to the back of the
fabric by back-coating.
[0007] U.S. Pat. No. 5,498,471-A describes an aqueous non-flowing
coating or impregnating composition for a non-woven or paper
substrate for flexible circuit boards, which composition includes
a) a cross-linked product of an aqueous dispersion of a
cross-linkable copolymerisate of acrylic esters and styrene and b)
an aqueous solution of a precondensate containing hydroxymethyl
groups (aminoplastics and phenoplastics) and which further contains
as a particulate dispersed flame retardant red phosphorus of a
grain size of 45 to 100 .mu.m (Exolit 405 being named as an
example) and an ammonium polyphosphate of a grain size of 25 to 75
.mu.m (Exolit 422 being named as an example). The coating
composition is applied to the substrate and dried, then the coated
substrate is laminated under pressure with the conductive metal
(copper) foil, by which the surface appearance of the coating is no
longer visible. If it were desired to print the paper or non-woven
backing of the laminated metal any such printing treatment would
thus have to be carried out on the non-coated side of the non-woven
or paper so that, from the view point of any printing or other
graphic use of the non-woven or paper surface after lamination, the
coating has been applied to the back of the paper or non-woven.
These coating compositions and the produced coatings contain the
red phosphorus which provides a corresponding shade to the
composition and coating; in the example this shade is hidden by the
addition of a blue pigment (Luconyl Blue).
[0008] In CS-B-239173 there is described a coating of paper,
cardboard or carton with a coating mix containing 10-40% of
aluminium hydroxide and 60 to 90% of kaolin as pigments, 0.2 to 2%
based on the pigment, of a flame retardant, e.g. of secondary
ammonium phosphate, and further 0.1 to 1.5%, based on the pigment,
of molecular colloids and 5 to 15%, based on the pigment, of
polyvinyl acetate.
[0009] In the above documents the ammonium polyphosphates are
employed in a form, a way of application and concentration that
provides just a form of flame retarding effect but that is of no
particular bearing in the appearance and graphic utilization of the
treated substrate.
[0010] It has now been found that particularly hard and insoluble
flame retarding polyphosphates of a particular particle size, as
defined below and which are not combined with red phosphorus, are
surprisingly well suitable in particular also as fillers or white
pigments in coating compositions for the production of coated and
pressed substrates, as defined below, of outstanding surface
properties, particularly suitable for graphic processing, and of
outstanding non-flammability properties.
[0011] The invention relates to a process for the production of
coated and pressed cellulosic fibrous substrates of loose,
optionally bonded fibers, to suitable coating compositions of
defined particle size of the dispersed particles, to their
production, to the coated and pressed substrates and to their use
as substrates for graphic processes, especially printing.
[0012] The invention thus firstly provides a process for the
production of a coated and pressed cellulosic fibrous flat
substrate of loose, optionally bonded fibers, by application of
[0013] (M) an aqueous coating composition, containing a binder (B),
a white pigment (W) and a dispersant (D), wherein at least a part
of the white pigment (W) is
[0014] (A) a particulate ammonium polyphosphate of crystalline form
11 of average particle size<40 .mu.m and with a water
solubility<10 g/l at 25.degree. C., to the face of the substrate
and subjecting to pressure.
[0015] As a flat substrate of loose, optionally bonded fibers there
is meant any such substrate in which the fibers are processed in
loose form to a web, which may be bonded with suitable binders.
These substrates are in particular those in which the loose fibers
in the form of webs serve for the production of paper, paperboard,
board or non-wovens, or are in the form of non-coated sheets of
paper, paperboard or board or of pre-formed non-coated non-woven
webs or tissues.
[0016] As a flat substrate made of loose optionally bonded fibers
there is more particularly meant any such substrate, in which loose
fibres have been directly processed to a flat substrate from an
aqueous suspension or by forming a fiber mat from dry loose fibers
mechanically or also with the aid of air; i.e. by processes in
which the fibres are not in the form of yarns or strands or any
woven or knitted fabric. As a substrate there may thus be employed
any fibrous cellulosic flat substrate made of loose optionally
bonded fibers, as is suitable for the application of a
particulate-pigment-containing coating and subjecting to pressure
(e.g. with plates, air knives or press rolls), in particular webs
of cellulosic fibers, mainly webs or sheets of paper, paperboard or
board or -non-woven tissue webs or mats. Preferably the process of
the invention is employed for the production of coated paperboard
or, most preferably, coated paper. The said mat, web or sheet
(preferably paper or paperboard) may be formed of any conventional
cellulosic fibrous material, e.g. from annual plants or wood, e.g.
chemical, semichemical and mechanical or groundwood pulp, or also
reclaimed or recycled paper (which may e.g. be broke, gray paper,
deinked paper, etc. and may optionally be bleached) and/or made
from processed rags.
[0017] The webs, mats or sheets to be employed as a substrate, may
have been produced by any conventional methods. In a web of paper
or paperboard the loose fibers may be bonded only mechanically and
with the own fibre substance (e.g. starch, pectine etc.) or
preferably also by means of suitable additives, e.g. a size. The
coating may be applied in one same sequence during papermaking, or
analogously in making the board or paperboard. Alternatively the
production of paper, paperboard or board may be carried out only
until a non-coated sheet of paper, paperboard or board is formed
and coating and pressing may be carried out separately. Also for
non-wovens it is possible to apply the coating to the optionally
bonded web in one same sequence in the production of the non-woven
tissue or in a separate treatment.
[0018] The aqueous coating composition (M) to be employed in the
process of the invention contains as an essential component a white
pigment (W) which is in particulate solid form, suitably dispersed
in the coating formulation.
[0019] In the coating of the invention the particulate white
pigment (W) may consist substantially only of (A) or may be a
mixture of (A) with a one or more components, in particular with
one or more white mineral pigments (P) and/or with one or more
melamine (poly)phosphates (L).
[0020] (W) may thus consist of one particulate component or of a
mixture of particulate components, at least a part of which is the
particulate ammonium polyphosphate (A) of crystalline form II which
is of the stated very small particle size and very low solubility.
Preferably its water solubility is <6 g/l at 25.degree. C.
[0021] The ammonium polyphosphates (A) are preferably of high
molecular weight and are preferably substantially linear. They may
be represented by the average formula (NH.sub.4PO.sub.3).sub.n,
wherein n represents the degree of polymerisation and is
preferably>800, more preferably>1000, e.g. even>4000.
[0022] The acid number of (A) is preferably <1, more preferably
<0.8, and the viscosity of an aqueous 20% suspension of (A) is
preferably below 200 mPa.multidot.s, more preferably below 120
mPa.multidot.s, most preferably in the range of 50 to 100
mPa.multidot.s.
[0023] The particulate ammonium polyphosphate (A) is of crystalline
form II, which may have been produced by any known or conventional
methods as are suitable for the production of such an ammonium
polyphosphate of low water solubility, e.g. by reaction of
phosphoric acid anhydride with ammonia and/or diammoniumphosphate,
optionally in the presence of urea or melamine, at elevated
temperature, at least a part of the reaction being carried out
preferably at a temperature in the range of 170 to 375.degree. C.,
or/and by tempering of a corresponding ammonium polyphosphate of
crystalline form I, IV or V at a suitable temperature between 200
and 375.degree. C.
[0024] Processes of this kind are known in the art and are
described e.g. in EP-A-49763, 88265, 411381, 480180 and 537475 and
in DE-A-2330174.
[0025] The ammonium polyphosphates II known in the art usually have
a varying average particle size, e.g. in the range of 500 to 5
.mu.m. According to the invention there are employed (A) of average
particle size below 40 .mu.m. Preferably the average particle size
is low, preferably in the range of 0.1 to 35 .mu.m, more preferably
1 to 25 .mu.m, most preferably 2 to 15 .mu.m, the lower average
particle sizes, in particular below 25 .mu.m, especially below 15
.mu.m or even.ltoreq.10 .mu.m (e.g. in the range of 2 to 15 .mu.m)
being particularly preferred. Further it is also preferred that the
particles of (A) be all of a size below 40 .mu.m. If desired, the
particles of (A) may even be all below 30 .mu.m or even below 25
.mu.m. The small particle size of (A) may e.g. be produced by
comminuting a conventional ammonium polyphosphate II, suitably by
grinding or milling to the desired particle size, and if necessary
screening, or e.g. by selecting the inferior size particles in
production lots of a broad range of particle sizes e.g. by suitable
screening and/or sieving. For the purpose of the invention it is in
particular preferred to comminute crystalline ammonium
polyphosphate II produced by tempering at the high temperatures
mentioned above, although it is very hard and milling will require
suitable ball mills or bead mills and a corresponding milling time,
or to separate correspondingly small particle size proportion from
a so produced ammonium polyphosphate II. The harder qualities of
ammonium polyphosphate II are preferred for the process of the
invention. It is in particular surprising that these small particle
size ammonium polyphosphates 11 are suitable as white pigments or
white fillers in coatings, especially paper coatings, and more
particularly that they are of similar or even superior properties
as compared to conventional mineral white pigments or fillers.
[0026] As (P), i.e. as a white mineral pigment or filler, there is
intended any such inorganic white pigment or filler as
conventionally employed in coating compositions and which may
comprise true minerals and also inorganic compounds analogous to
mineral products, i.e. modified minerals or also synthetically
produced inorganic compounds of analogous or related properties to
mineral white pigments or fillers. As mineral products there may be
mentioned e.g. kaolin, calcium carbonate, barytes, bentonite, mica,
montmorillonite, slate, talc and titanium dioxide. As products
obtained by processing minerals there may be mentioned e.g. calcium
carbonate or sulphate, barium sulphate, satin white and
argillaceous minerals. As products obtained by a synthetic reaction
to produce a compound of properties similar to those of mineral
forms there may be mentioned e.g. titanium dioxide, silica, calcium
carbonate or sulphate, barium sulphate (blanc fixe), alums and
cementitious powders. Their particle size may range in a scope as
per se conventionally employed in coating compositions; in
particular their average particle size may be well below 40 .mu.m
and also well below 25 .mu.m. White mineral pigments used in
coating compositions for paper are mostly of a particle size in the
range of 0.1 to 10 .mu.m, best pigment properties and light
scattering being achieved mostly at a particle size in the range or
0.2 to 2 .mu.m, particle sizes in the higher ranges of e.g. 2 to 10
.mu.m being usually more suitable for fillers.
[0027] The term "white pigment" as used herein is intended to
include as well particulate white components with typical white
pigment properties (such as crystallinity, size and light
refraction) as also particulate white components which may be used
as fillers (e.g. where the light scattering properties may be
somewhat inferior to those of the typical pigments, but which still
contribute to the whiteness and opacity of the coating).
[0028] According to a particular feature of the invention, (W)
contains also a particulate melamine (poly)phosphate (L). Melamine
(poly)phosphates are known substances and may be represented by the
general formula
(C.sub.3H.sub.6N.sub.6).sub.m(NH.sub.3).sub.p.multidot.(H-
PO.sub.3).sub.n, in which n is as defined above, m is a number
corresponding to the proportion of melamine employed and
is.ltoreq.n (e.g. n/2 to n), and p is a number in the range from 0
to n-m. They can be produced by known methods or analogously to
known methods, in particular analogously to ammonium
polyphosphates, by reaction of melamine with phosphorus pentoxide
and optionally ammonia and/or urea under elevated temperature
conditions. Where desired or required, their particle size may be
reduced by comminuting analogously as described above for (A). The
particle size of (L) is in particular compatible with the one of
the other components, in particular it is similar to the one of
(A), i.e. the average particle size is below 40 .mu.m, preferably
below 25 .mu.m, with preferably no particles exceeding 40 .mu.m,
those with an average particle size below 15 .mu.m or
even.ltoreq.10 .mu.m (e.g. in the range of 0.5 to 15 or 1 to 10
.mu.m) being particularly preferred. Their solubility in water is
also very low, in particular lower than the one of (A) and they are
preferably practically insoluble; their solubility in water at
20.degree. C. is e.g. below 6 g/l, especially below 1 g/l.
Commercially available grades are e.g. of a water
solubility.ltoreq.0.1 .mu.l.
[0029] If another particulate white pigment component, i.e. (P) or
(L) or both, is present together with (A) in (W), this may be e.g.
(P) alone or (L) alone or a mixture of (P) and (L). Where (W) is a
mixture of (A) with other components, in particular with mineral
pigments (P) and/or with (L), (A) is expediently present in an
efficient proportion. Preferably (A) constitutes at least 4% by
weight of (W), advantageously 5 to 100% of (W), more preferably 20
to 100%, the remaining up to 96, 95 or respectively 80% being (P)
or (L) or (P)+(L).
[0030] If only (P) is present together with (A) in (W) the weight
ratio of (P) to (A) in (W) is e.g. in the range of from 0.1/10 to
10/0.5 advantageously 0.1/10 to 10/1, preferably 0.1/10 to 5/1,
more preferably 0.1/10 to 4/1. When (L) is present in (W) it may
replace a part or even all of (P). If (L) is present, the weight
ratio of [(L)+(P)]:(A) is e.g. in the range of from 0.1/10 to
10/0.5, advantageously 0.1/10 to 10/1, preferably 0.1/10 to 5/1,
more preferably 0.1/10 to 4/10.
[0031] If both (P) and (L) are present together with (A), the
weight ratio of (P) to (L) may be in any desired range as suitable
for the envisaged purpose, e.g. in the range of from 0.1/10 to
10/0.1 advantageously 0.1/10 to 4/10, preferably 0.1/10 to 2/10,
more preferably 0.1/10 to 1/10.
[0032] According to a preferred feature no (P) is present in (W),
especially when (L) is present.
[0033] A further essential component of the aqueous coating
compositions (M) is the binder (B). As a binder (B) there may be
employed any conventional binder or mixture of binders as is
usually employed in coating compositions, especially in paper
coatings. Representative binders are conventional polymers,
e.g.
[0034] (B.sub.1) styrene/butadiene polymers,
[0035] (B.sub.2) acrylic co- or ter-polymers,
[0036] (B.sub.3) polyvinyl acetates
[0037] and (B.sub.4) polyurethanes.
[0038] The binder (B) may be present in (M) in concentrations
conventional per se, as suitable for binding the pigment particles
to the substrate. The ratio of (B) to (W) on a dry basis is e.g. in
the range of 1/0.2 to 1/20, preferably 1/1 to 1/12, more preferably
1/3 to 1/8.
[0039] The dispersants (D) may be any dispersants or mixtures of
dispersants as conventionally employed in paper coating
compositions and are preferably anionic or non-ionic dispersants.
They may be simple non-polymeric compounds or polymers, e.g. also
of protective colloid character. As examples of non-polymeric
non-ionic dispersants there may be mentioned adducts of ethylene
oxide and optionally propylene oxide to an aliphatic alcohol such
as C.sub.1-24-fatty alkohols (natural or synthetic alkohols) to a
mono- or dialkylphenol with 6 to 18 carbon atoms in the total of
alkyl radicals present, with an HLB e.g. in the range of 8 to 16.
As examples of nonpolymeric anionic dispersants there may mentioned
aliphatic sulphonic acids in salt form such as sodium
C.sub.11-24-alkane sulphonates, or araliphatic sulphonic acids in
salt form such as sodium mono- or dialkylbenzenesulphonates with 6
to 18 carbon atoms in the total of alkyl radicals present, and
aliphatic carboxylic acid salts (soaps) such as C.sub.12-24-fatty
acid salts, e.g. alkali metal salts (preferably sodium salts) or
ammonium salts (including also amine salts of low molecular amines,
such as mono-, di- or tri-ethanol- or -isopropanol-amine), or also
natural products or derivatives, in particular from pulping
processes, such as talloil soaps and lignine sulphonates.
Preferably the dispersants (D) are polymers, more preferably water
soluble polymers, in particular polyacrylic acid salts (e.g. alkali
metal or ammonium salt, usually of an average molecular weight in
the range of 2000 to 10000) or polyphosphates (e.g. a water soluble
ammonium polyphosphates, e.g. of a degree of polymerisation of 3 to
30, e.g. tetra or hexametaphosphate), and may be present in very
low concentrations as suitable for maintaining a uniform
distribution of the undissolved particles in the aqueous
composition. Preferably the concentration of (D) is in the range of
0.01 to 1%, more preferably 0.1 to 0.5% referred to the weight of
the dry content of the coating composition (M).
[0040] The coating compositions (M) may optionally contain further
components, as may be desired or suitable depending on the desired
effect, on the employed method and employed apparatus for
application and on the nature and composition of the substrate,
e.g. dyestuffs and/or optical brighteners and any optional
assistants such as surface active agent, thickeners, resins and/or
formulation additives. Thus (M) may further contain one or more
further additives selected from
[0041] (C) which is
[0042] (C.sub.1) at least one optical brightener
[0043] and/or (C.sub.2) at least one dyestuff,
[0044] (E) a thickening agent,
[0045] (F) at least one resin other than (B)
[0046] and (G) at least one formulation additive, suitable for
modifying or maintaining the physical form of the composition and
which is suitably employed in minor amounts.
[0047] (C.sub.1) may be any optical brightener suitable for the
optical brightening of cellulosic substrates, especially paper,
and/or for use in coating compositions, and is preferably anionic.
Among the anionic optical brighteners are preferred those of the
4,4'-bistriazinylaminostil- bene-2,2'-di-sulphonic acid series,
especially those in which each triazinyl ring is substituted with
two amino groups, one of which is an optionally sulphonated aniline
radical and the other is aliphatic. There may be employed known
optical brighteners as are commercially available and as are
conventionally employed also in coatings.
[0048] (C.sub.2) may be any dye suitable for the dyeing of
cellulosic substrates, especially paper, for which it is preferably
a water soluble preferably anionic dye, and/or for use in coating
compositions, for which it may be a water soluble preferably
anionic dye, or may also be a dye insoluble in water.
[0049] Among the anionic dyes are preferred
[0050] (C.sub.2') direct dyes.
[0051] The insoluble dyes are in particular
[0052] (C.sub.2") colour pigments.
[0053] There may be employed any direct dyes and pigments e.g. as
defined under these name in the "Colour Index" (published by The
Society of Dyers and Colourists) and known in the art, in
particular as are commercially available and as are conventionally
employed also in coatings.
[0054] As (E) there may be employed known thickening agents, in
particular as are conventionally employed in coating compositions
for paper coatings; preferably (E) an acrylic polymer or a
poly-urethane.
[0055] As (F) there may be employed any resins as conventionally
employed in coating pastes, in particular a resin containing
hydroxymethyl groups or oxirane rings and which is curable, in
particular with a suitable binder (B). Preferably (F) is a curable
resin selected from:
[0056] (F.sub.1) melamine/formaldehyde resins,
[0057] (F.sub.2) urea/formaldehyde resins,
[0058] (F.sub.3) glyoxal resins,
[0059] (F.sub.3) epoxy resins
[0060] and (F.sub.5) polyurethanes
[0061] Among the mentioned resins (F) are preferred (F.sub.1),
(F.sub.2) and (F.sub.5), especially (F.sub.1).
[0062] Components (E) and (F) serve for adjusting the consistency
of (M) and the mechanical properties of the final coating, such as
strength, pliability, elasticity and touch of the coated and
pressed dry product, and their amount and kind will also depend on
the chosen application method and apparatus.
[0063] In the formulation of the coating composition a binder, such
as (B), depending on its particular constitution may also
contribute to a minor degree to the thickness of the composition
and/or to the mechanical properties of the final coated product,
and vice versa (E) or (F) may also contribute to a minor degree to
the binding of the components in (M). The choice and concentration
of any components (E) and/or (F) will mainly depend on the desired
properties of (M) and the mechanical properties of the coated
product in the presence of a certain chosen binder (B), and it is
in the skill of the coating specialist to choose the components and
to adjust their concentrations depending on the desired mechanical
properties of the coating mass (M) and of the coated product and
also on the employed apparatus and method.
[0064] Component (G) is at least one formulation additive, i.e. a
product for providing and maintaining a certain constitution of the
composition (M), in particular--for example--in order to protect it
against the damaging action of micro-organisms or to avoid a
disturbing foam formation or further, if desired, in order to
provide or modify the flowability properties of the composition
and/or also in order to select a preferred pH which may be suitable
for the particular composition and favour its storage and
application properties.
[0065] As (G) there may in particular be employed:
[0066] (G.sub.1) an anti-microbial agent,
[0067] (G.sub.2) a defoamer,
[0068] (G.sub.3) a flow agent
[0069] and/or (G.sub.4) an acid, base and/or buffer for
pH-adjustment.
[0070] As (G.sub.1) there may be employed any antimicrobial agent
as commercially available and conventionally employed for
protecting an aqueous coating composition from the damaging action
of micro-organisms; it may e.g. be microbial growth inhibitor or a
microbicide (e.g. a fungicide), as commercially available, e.g. of
the 1,2-benzisothiazolin-3-one series, and may be employed in an
efficient concentration, e.g. <3% by weight referred to (M),
suitably in the commercially indicated concentrations, e.g. in a
concentration of 0.01 to 3%, preferably 0.05 to 1%, more preferably
0.1 to 0.2% by weight referred to (M).
[0071] As (G.sub.2) there may be employed any defoamer as
commercially available and conventionally employed in coating
compositions, e.g. a defoamer of the polydimethyl-siloxane or
alkoxane series. It may be employed in a sutable efficient
concentration, e.g. in the commercially indicated concentrations,
e.g. in a concentration of 0.01 to 1%, preferably 0.05 to 0.2%,
more preferably 0.05 to 0.1% by weight referred to (M).
[0072] As (G.sub.3) there may be employed any flow agents as
commercially available and conventionally employed for modifying
the flow properties of coating compositions. (G.sub.3) may e.g. be
a preferably saturated fatty acid salt (e.g. of 16-24 carbon atoms
in the fatty acid) preferably a stearic acid salt, e.g. an alkali
metal salt, alkaline earth metal salt or ammonium salt, and is
present in a suitable efficient concentration, e.g. in the range of
0.01 to 5%, preferably 0.05 to 2%, more preferably 0.1 to 1.5% by
weight referred to (M). A flow agent (G.sub.3) is preferably
employed, in particular to adjust the viscosity of the coating
dispersion to such values as suitable for the employed coating
apparatus and speed and depending also on the kind of substrate,
the particular composition of (M) and the desired effect,
preferably so that the viscosity is kept at values below 3000
mPa.multidot.s, preferably below 1500 mPa.multidot.s.
[0073] The pH of (M) may vary broadly, in particular from
distinctly acidic to strongly basic, especially from 5.5 to 13,
preferably 7 to 10, more preferably 8 to 9; if required or desired,
it may be adjusted by the addition of one or more additives
(G.sub.4), which may e.g. be a base such as ammonium hydroxide,
alkali metal hydroxide or carbonate or magnesium oxide, a strong
mineral acid such as phosphoric acid or sulphuric acid, or a strong
aliphatic carboxylic acid e.g. with 1 to 6 carbon atoms (such as
formic, acetic, oxalic, lactic or citric acid) and/or optionally a
buffer salt such as ammonium or sodium hydrogen phosphates.
[0074] The consistency of the flame-proofing coating composition
(M), in particular its dry substance content, density and viscosity
may vary broadly, depending e.g. on the method of application and
the employed apparatus, on the substrate and on the desired effect.
The dry substance content of (M) may in particular be in the range
of 1 to 90%, advantageously 5 to 85%, preferably 20 to 80%, more
preferably 25 to 75%. The proportion of (W) and of (A) in (M) may
thus also vary accordingly. Preferably (W) represents the main
component--i.e. >50%, more preferably 60 to 95% by weight--of
the dry substance content of (M) and more preferably (A) or even a
mixture of (A) with (L) as described above represents a substantial
proportion, e.g. >8%, or even the main component--i.e.
.gtoreq.50%, more preferably 60 to 95% by weight--of the dry
substance content of (M), and thus (A) may outweigh each or even
all other components of the dry substance content of (M). The
viscosity of (M) may thus also vary broadly so long as (M) may
still be spread on the substrate; the rotational viscosity measured
in a Brookfield viscosimeter at 30 rpm and 20.degree. C. may e.g.
be in the range of 1 to 15000 mPa.multidot.s, advantageously 10 to
8000 mPa.multidot.s, preferably 100 to 3000 mPa.multidot.s, more
preferably 400 to 1500 mPa.multidot.s.
[0075] The coating compositions of the invention is a dispersion of
the above described very fine particle size of the dispersed
particulate solid components, i.e. white pigment (W) [(A) and, if
present, also (P) and/or (L), being in particular of an average
particle size below 25 .mu.m] and any other optionally present
pigment (C.sub.2") which is also of a particle size in the stated
range (in particular in the microcrystalline to kryptocrystalline
grain size range), which are present together with the binder (B),
the dispersant (D) and any further component of (M). The binders
(B) present, which may be more or less hydrophilic and more or less
dissolved or swollen in the aqueous phase, are not considered
within the above definition of dispersed particulate solid
components of very fine particle size. More particularly the
particulate dispersed pigment components present in (M) essentially
consist only of (W) and optionally (C.sub.2"). More preferably no
pigments (C.sub.2") are present and the particulate dispersed solid
components consist essentially only of (W).
[0076] The aqueous compositions (M) can be produced by mixing the
components in a suitable way, analogous to conventional methods. In
particular the coating compositions (M) may be produced by first
mixing (W), more particularly the pigment components (A) and
optionally any (L) and/or (P), with water and optionally (G.sub.3),
adding (D) and then (B) followed by the addition of any further of
the components (C), (E), (F) and/or (G) as required or desired. The
mixing is advanageously carried out at a temperature not exceeding
35.degree. C., preferably at a temperature in the range of 12 to
25.degree. C., and any further water may be added as required for
achieving a certain desired concentration and viscosity. The mixing
is expediently carried out with stirring and at a concentration of
the components in water at which the composition is readily
stirrable.
[0077] The produced composition (M)--which in particular is a
flowable aqueous dispersion--is ready for use and can be handled
and applied analogously to any other coating composition for paper,
paperboard, board or non-woven tissue, by means of conventional
coating techniques in which pressure is applied either during the
coating or after application of the coating composition or
both.
[0078] As a fibrous flat substrate of loose, optionally bonded
fibers there may be employed any suitable support web or sheet,
especially paper, paperboard or board made from any desired
conventional primary and/or secondary substances which are suitable
for the production of paper, paperboard or board, in particular
made from conventional fibre material, principally cellulosic fibre
material, for example from hardwood (for example maple, birch,
beech, poplar), from softwood (for example pine, spruce, larch,
fir), from annual plants (for example straw, jute, ramie, bagasse,
flax, hemp, reed, sisal, coconut, cotton) or from textile fibres
(for example rags, cotton, linen, flax, ramie, jute) or also from
recycled paper production waste or from used paper, where the
non-digested fibres, namely textile fibres, wood fibres and fibres
from annual plants, can be processed in a manner which is
conventional per se to give pulp, for example by mechanical and/or
chemical and/or thermal methods (in particular wood pulp,
mechanical wood pulp, brown wood pulp, yellow straw pulp, chemical
pulp, semichemical pulp and chemically digested pulp), and recycled
printed paper or used paper, can, if necessary, be deinked. If
desired or if necessary, the material can be bleached with
conventional bleaching agents, for example reductively and/or
oxidatively (for example with sodium hydrosulphite, thiourea
dioxide or hydrogen peroxide). The substrates may be lignin-free or
lignin-containing, e.g. containing.gtoreq.5%,
preferably.gtoreq.10%, of lignin, based on dry fibres, such as
paper containing wood pulp or semichemical pulp or board containing
wood pulp or semichemical pulp. The pulp or the corresponding
fibres can, if desired after blending various types of fibre and/or
types of pulp with one another, for example from mechanically
digested pulp and/or chemically (sulphite or sulphate method)
and/or thermally digested pulp and/or combination-digested pulp
(semichemical pulp), be processed further, optionally with at least
10% of recycled paper or used paper. It is possible to use any
desired conventional additives which are suitable for papermaking,
such as, for example drainage and/or retention agents, and if
desired optical brighteners, dyes, sizing agents and/or fillers
(for example kaolin, talc or other silicates or calcium carbonate),
as can usually be admixed with the aqueous pulp composition before
sheet formation, and fixatives.
[0079] The aqueous pulp suspension intended and formulated for the
production of the web can be applied in any conventional manner to
the wire end, where the dewatering to the desired water content
takes place. From the wire end, the web is then transported to the
press section, where the water content is reduced further, for
example usually in the range from 70 to 30%, so that the moist
sheet reaches the dry end with a water content of .ltoreq.30%.
After the dry end, the support sheet produced is usually fed
through the calender (intermediate or dry calender) or otherwise
through drying rolls and can if desired by given a surface sizing.
The coating with (M) can be carried out subsequently during
papermaking, or the not yet coated paper or board may be dried and
rolled up and the coating with (M) is then carried out afterwards,
more particularly at the final user's factory, more particularly
immediately before printing. (M) may be applied to the face of the
substrate or also to both sides.
[0080] The coating of the invention may be carried out by any
suitable method conventional per se in which pressure is applied
either during coating or after application of the coating
composition (M) to the substrate or both. The substrate coated with
(M) may thus be dried at elevated temperature, preferably at a
temperature in the range of 60 to 150.degree. C., preferably
through drier rolls, and may then optionally be calendered or
embossed, or the coated and not yet dried web may be subjected to
pressure by conventional means, e.g. by means of an air knife, a
rod or bar, a blade or brushes (for improving penetration and
distribution of the coating) or to roll pressure, and is then
dried, or/and the coated substrate may be subjected to plate or
cylinder pressure optionally after drying e.g. through drier
rolls.
[0081] Conventional application coating techniques which may be
mentioned and are suitable for the application of (M) according to
the invention are e.g.: air knife coating, rod or bar coating,
blade coating, transfer roll coating, size press coating, kiss roll
coating, spray coating, brush coating, dip coating, reverse roll
coating and cast coating. In some of these pressure is already
applied during application of the coating composition, such as in
air knife coating, rod or bar coating, blade coating, transfer roll
coating, size press coating, reverse roll coating and cast coating,
in the other pressure is applied after application of the coating
composition, such as in kiss roll coating, spray coating, brush
coating and dip coating. The applied pressure may vary broadly and
is e.g. .gtoreq.0.5 bar, preferably is .gtoreq.1 bar
superatmospheric pressure, and may range e.g. up to the maximum
pressure allowed by the employed machine and system.
[0082] Depending on the envisaged use and quality of the product,
the pressure applied in coating or immediately afterwards, for
smoothening and equalizing the surface may already suffice;
according to a particularly preferred feature of the invention, the
coated paper or board after having been coated is subjected to
pressure, e.g. through drier rolls, or according to a still further
preferred feature, it is subjected to pressure after having been
intermediately dried, preferably this latter variant comprises
subjecting the coated and intermediately dried substrate to
pressure by means of cylinders or plates, in particular by
calendering or embossing, or/and when applying a water mark to the
paper or/and when printing. If multilayered board is being
produced, the respective lower, middle and upper layers are couched
to one another in the press section before drying; for each of the
layers there may be employed a composition (M).
[0083] The quantity of (A) applied to the substrate may be in any
desired range; suitably it is present in such a proportion as to
provide--in the (M)-coated substrate--a perceivable effect in the
coating, in particular in the physical properties of the coated
material (mainly brilliance, whiteness, opacity and printability)
and especially in flame retarding properties. The invention thus
further provides a process for coating and flame-proofing the
stated substrates by coating with (M) as described above, wherein
(A) is present in a concentration efficient for providing a
flame-proofing action. (M) may be applied to the substrate in a
coating weight (dry substance) e.g. in the range of 0.1 to 100
g/m.sup.2 (for paper preferably 0.1 to 60 g/m.sup.2 more
preferably--depending on the way of applicaion--1 to 30 or even 5
to 25 g/m.sup.2, for paperboard preferably 0.2 to 100 g/m more
preferably 2 to 50 g/m.sup.2, for non-woven tissue web preferably
0.1 to 100 g/m.sup.2 more preferably 5 to 50 g/m.sup.2).
[0084] The suitable and preferred concentrations and viscosities
may vary not only depending on the particular substrate,
composition and desired effect but also on the chosen particular
application method and apparatus. Thus for some representative
application methods of those mentioned above the preferred way of
working is as follows:
[0085] Air Knife Coating
[0086] An excess of coating mix (M) is applied to the base paper
and the mobile portion is metered off by means of air. The air is
delivered through a carefully controlled slot having an air
pressure between 5 and 45 kilo Pascals, that cuts into the fluids
portion of the coating layer like a knife. The solids content of
(M) is preferably in the range 35-50% and and the viscosity is
preferably in the range of 100400 mPa.multidot.s, with which defect
free and print mottle free coatings may be achieved. Typical coat
weights using air knife configurations preferably range from 4-30
g/m.sup.2. The preferred metering will in particular be selected
depending on the particular employed apparatus, nature of the
substrate and composition of (M), mainly by:
[0087] 1. The energy of the air jet.
[0088] 2. The angle of the airjet in conjunction with the coated
surface and the backing roll.
[0089] 3. The distance between the application and metering
points.
[0090] 4. Machine speed.
[0091] 5. Solids content and viscosity of the coating composition
(M).
[0092] Bar (or Rod) Coating
[0093] An excess of coating mix (M) is applied to the base paper
with the surplus being metered off using a rod or bar (normally
termed metering bar or rod). The metering bar may be stationary or
rotating with or against the direction of the web. Smooth bars
normally meter the coating by an applied pressure, whilst wire
wound bars (sometimes called Meyer bars), have a secondary metering
effect. The coating mix is contained in the valleys between the
windings, thus depending on the size of the wire used; the valleys
will contain a corresponding amount of coating mix. Depending on
the coat weight required, a particular bar may be chosen. The
solids content of (M) is preferably in the range 30-63% and and the
viscosity is preferably in the range of 100-1500 mPa.multidot.s,
with which defect free and print mottle free coatings may be
achieved. Typical coat weights using bar or rod configurations
preferably range from 2-15 g/m.sup.2. The preferred metering will
in particular be selected depending on the particular employed
apparatus, nature of the substrate and composition of (M), mainly
by:
[0094] 1. The type of bar or rod chosen
[0095] 2. The pressure applied to the bar and its position relative
to the backing roll.
[0096] 3. Base paper properties, e.g. roughness, porosity
[0097] 4. The distance between the application and metering
points.
[0098] 5. Solids content and viscosity of the coating composition
(M).
[0099] Blade Coating
[0100] An excess of coating mix (M) is applied to the base paper
with the surplus being metered off (scraped off) using a blade.
There are many types and configurations of blade; i.e. stiff, bent,
flexible, but all have generic requirements for coating quality.
The viscosity of the coating mix (M) will change depending on the
shear rate applied to it during the coating process. This will
depend upon the coater speed, pressure applied to the blade, blade
geometry (i.e. angle, thickness, etc.) and the degree of
compressibility of the web. The solids content of (M) is preferably
in the range 45-75% and the viscosity is preferably in the range of
700-3500 mPa.multidot.s, with which defect free and print mottle
free coatings may be achieved. Typical coat weights using blade
configurations preferably range from 2-25 g/m.sup.2. The preferred
metering will in particular be selected depending on the particular
employed apparatus, nature of the substrate and composition of (M),
mainly by:
[0101] 1. The type of blade and configuration
[0102] 2. The pressure applied to the blade and its position
relative to the backing roll.
[0103] 3. Base paper properties, e.g. roughness, porosity
[0104] 4. The distance between the application and metering
points.
[0105] 5. Solids content and viscosity of the coating composition
(M).
[0106] 6. Hydrodynamic effects (rheology).
[0107] Transfer Roll Coating
[0108] The coating mix (M) is progressively transferred from one
roll to other, being evened out as it travels before being
transferred to the web. Any conventional number of transfer rolls
can be employed, but preferably 2 to 15 are used. The rolls can be
made of various materials and can operate in different directions
and speeds. The solids content of (M) is preferably in the range of
30-60% and the viscosity is preferably in the range of 100-800
mPa.multidot.s, with which defect free and print mottle free
coatings may be achieved. Typical coat weights using transfer roll
configurations preferably range from 0.5-15 g/m.sup.2. The
preferred metering will in particular be selected depending on the
particular employed apparatus, nature of the substrate and
composition of (M), mainly by:
[0109] 1. The number of transfer rolls and type of covering.
[0110] 2. The pressure applied between the transfer rolls, and to
the base sheet.
[0111] 3. Base paper properties, i.e., roughness, and porosity.
[0112] 4. Solids content and viscosity of the coating composition
(M).
[0113] The application of (M) can be carried out on one or both
sides, depending on the type and purpose of the paper or board.
One-sided application is suitable, for example, for a cardboard top
layer, for label, poster or packing paper. Two-sided application is
suitable, for example, for graphic papers, book printing, magazine,
newspaper, letter, drawing or office paper, or also for special
single-layer types of cardboard, such as, for example Bristol
board.
[0114] The invention provides the possibility of producing a most
broad choice of coatings in various kinds and of optimum properties
and in particular of high flame retarding properties. In
particular, by the possibility of using various ways of application
and of processing (also in the drier section and/or in
calendering), by employing various kinds, consistencies and
quantities of coating composition on various kinds of substrates, a
correspondingly very broad choice of coated product of high flame
retarding efficiency and fine appearance, in particular optimum
whiteness and graphic properties, becomes available.
[0115] According to the coating process of the invention it is
possible to obtain, even with coating compositions (M) that do not
contain any (P), coatings of excellent, surprisingly high
whiteness, brillancy, opacity and surface properties and
simultaneously with high flame retarding efficiency. By combining
an optical brightener in (M) the whiteness may even be increased.
They are suitable for producing coated substrates, especially
paper, paperboard and board, of outstanding graphic properties,
especially printability properties, for which any kind of printing
method is suitable, e.g. offset printing, ink jet, laser or screen
printing or any other kind of printing methods, including typing
and photocopying. Also the further physical properties of the
coated material are not impaired, such as strength, pliability and
compressibility, and the flame retarding properties are optimal.
The coating process of the invention is suitable for producing any
kind of coated paper, paperboard, board or non-woven tissue,
especially coated paper for printing purposes, preferably of 50 to
400 g/m.sup.2, such as letter, magazine, newspaper, drawing or
office paper, book printing paper, label paper, poster paper, wall
paper, packing paper and building paper. The fastness properties
are also optimal and the paper and board sheets surface-coated with
(W) in accordance with the invention are also very resistant to
yellowing caused by the action of light and/or heat. The (M)-coated
products may be recycled analogously to any other coated paper,
where in the recycling process the insoluble components (W) settle
out and can be separated, and any traces of suspended or
(colloidally) dissolved component of (M) may be precipitated or
flocculated with suitable flocculating agents as conventionally
employed in backwater purification and sludge dewatering.
[0116] A further subject-matter of the invention is the process for
the production of a substrate which has been graphically processed,
in particular written on, printed and/or graphically processed in
any other manner by application of at least one graphic ink pattern
to said substrate, and drying, which is characterized in that the
substrate used for this purpose is a flat substrate as described
above, especially paper, paperboard, board or non-woven tissue,
which has been coated with (M) and subjected to pressure as
described above.
[0117] By the coating process of the invention, in particular as
described above, there may be produced coated paper or paperboard
with a smooth, level, regular surface, which is particularly
suitable as a substrate for printing. Especially printing processes
as mentioned above can be used, principally intaglio printing,
newspaper printing, letterpress printing and offset printing in
general. In particular, a same level paper or paperboard can be
used as substrate both for intaglio printing and for offset
printing.
[0118] Printing can be carried out using any desired conventional
printing inks which contain constituents which are conventional per
se, essentially at least one dye and a suitable carrier or a
suitable binder and optionally additives. As dyes, principally
pigments (for example those as defined and also listed under
"Pigments" in the Colour Index), optionally combined with mineral
fillers, come into consideration, as usually employed in printing
inks; as binders, principally resins, which are advantageously
mixed with oils, come into consideration. The resins are mostly
alkyd resins and/or or phenyl-modified colophony resins and can, if
desired, be blended with further carrier substances, such as
suitable types of asphalt; as oils, oxidatively drying oils
(principally vegetable oils, in particular linseed oil or wood oil)
and physically drying mineral oils can be employed. As additives,
drying agents are advantageously employed, such as, for example,
tin, cobalt or manganese salts, for example manganese octanoate,
or/and optionally further additives, such as waxes. Such components
and additives or corresponding printing inks are known in general
terms and are described in large number in the specialised
literature, for example in EP-A-42515, 228372 and 666293. If
desired, however, water-borne printing inks can also be used, for
example those as described in EP-A-633143. The composition of such
printing inks is, for example,
[0119] 10-35% of colorant (consisting of 10-25% of pigment and
0-15% of mineral filler)
[0120] 20-73% of resins (if desired blended up to half with blend
substances, such as asphalt or oxidatively drying oils)
[0121] 15-60% of mineral oil
[0122] 2-12% of additives (for example drying agents and, if
desired, waxes).
[0123] For experimental purposes, it is also possible to use
standard printing inks, as also commercially available (for example
the test inks 40 8001 Inko.RTM. 11,2; 40 8002 Inko.RTM. 14,8; 40
8003 Inko.RTM. 19,5 and 40 8004 Inko.RTM. 25,0 from Farbenfabriken
Michael Huber, Munich, Germany), or inks conforming to BS 4666.
[0124] Clear prints with optimum colour body, fastness and contours
can be produced on the said substrates, and the printing properties
not being impaired (in particular with regard e.g. to any
interfering flaking phenomena, ink deposits or missing dots or ink
penetration). by the presence of the above described high
proportions of (A) in (M).
[0125] In the following Examples, the parts denote parts by weight
and percentages denote percent by weight; the temperatures are
indicated in degrees Celsius. The employed ammonium polyphosphate
II is of average particle size 10 .mu.m with no particles exceeding
40 .mu.m obtained by comminuting the commercially available
ammonium polyphosphate II Exolit.RTM. AP 422 in a ball mill, the
other components employed in the compositions and examples are
commercially available products. The papers employed in the
following examples are those produced in the paper mill and how
they are employed in the respective paper production step which
corresponds to the following examples. DIN stands for Deutsche
Industrie-Norm, NF stans for Norme Francaise and BS stands for
British Standard.
[0126] The following coating compositions (M) are employed, which
are produced by mixing at 22.degree. C. the ammonium polyphosphate
and any further pigment with water and with calcium stearate with
stirring, and then adding the binder and then the other
components:
[0127] Coating Composition M1
[0128] An aqueous coating composition of 60% dry substance content
consisting per 100.2 parts of dry substance of
1 Ingredients parts Ammonium polyphosphate II 86.2
Styrene/butadiene polymer (binder) 12.9 Calcium stearate (flow
agent) 0.9 Melamine/formaldehyde resin 0.9 Sodium polyacrylate
(dispersant) 0.2 1,2-Benz-isothiazolin-3-one (fungicide) 0.1
[0129] particularly suitable for blade, rod, cast or reverse roll
coating.
[0130] Coating Composition M2
[0131] An aqueous coating composition of 50% dry substance content
consisting per 100.5 parts of dry substance of
2 Ingredients parts Ammonium polyphosphate II 10.0 Talc (pigment)
14.9 Titanium dioxide (pigment) 14.9 Acrylic copolymer (binder)
59.7 Calcium stearate (flow agent) 0.5 Polydimethylsiloxane
(defoamer) 0.2 Sodium polyacrylate (dispersant) 0.2
1,2-Benz-isothiazolin-3-one (fungicide) 0.1
[0132] particularly suitable for air knife, blade, brush, rod,
screen, cast or reverse roll coating.
[0133] Coating Composition M3
[0134] An aqueous coating composition of 50% dry substance content
consisting per 101.2 parts of dry substance of
3 Ingredients parts Ammonium polyphosphate II 52.6 Clay (pigment)
35.1 Styrene/butadiene polymer (binder) 11.4 Calcium stearate (flow
agent) 0.9 Melamine/formaldehyde resin 0.9 Sodium polyacrylate
(dispersant) 0.2 1,2-Benz-isothiazolin-3-one (fungicide) 0.1
[0135] particularly suitable for air knife, blade, brush, rod,
screen, cast or reverse roll coating.
[0136] Coating Composition M4
[0137] An aqueous coating composition of 40% dry substance content
consisting per 100.9 parts of dry substance of
4 Ingredients parts Ammonium polyphosphate II 66.1 Clay (pigment)
16.5 Styrene/butadiene polymer (binder) 16.5 Calcium stearate (flow
agent) 0.8 Melamine/formaldehyde resin 0.8 Sodium polyacrylate
(dispersant) 0.2
[0138] particularly suitable for air knife, brush, rod, screen or
reverse roll coating.
[0139] Coating Composition M5
[0140] An aqueous coating composition of 40% dry substance content
consisting per 100.9 parts of dry substance of
5 Ingredients parts Ammonium polyphosphate II 41.3 Calcium
carbonate (pigment) 41.3 Acrylic copolymer (binder) 16.5 Calcium
stearate (flow agent) 0.8 Melamine/formaldehyde resin 0.8 Sodium
polyacrylate (dispersant) 0.2
[0141] particularly suitable for air knife, brush, rod, screen or
reverse roll coating.
[0142] Coating Composition M6
[0143] An aqueous coating composition of 62% dry substance content
consisting per 101.51 parts of dry substance of
6 Ingredients parts Ammonium polyacrylate (dispersant) 0.29
Ammonium polyphosphate II 82.18 Styrene/butadiene polymer (binder)
16.44 Calcium stearate (flow agent) 1.1 Melamine/formaldehyde resin
1.1 Optical brightener 0.33 1,2-Benz-isothiazolin-3-one (fungicide)
0.07
[0144] particularly suitable for blade and rod coating.
[0145] Coating Composition M7
[0146] An aqueous coating composition of 64% dry substance content
consisting per 101 parts of dry substance of
7 Ingredients parts Ammonium polyacrylate (dispersant) 0.2 Ammonium
polyphosphate II 64.5 Melamine polyphosphate 21.5 Styrene/butadiene
polymer (binder) 12.9 Calcium stearate (flow agent) 0.9
Melamine/formaldehyde resin 0.9 1,2-Benz-isothiazolin-3-one
(fungicide) 0.1
[0147] particularly suitable for blade coating.
[0148] As sodium polyacrylate dispersant in Coating Compositions M1
to M5 there may be employed e.g. DISPEX N40 (Ciba).
[0149] As ammonium polyacrylate dispersant in Coating Compositions
M6 and M7 there may be employed e.g. Mowiplus XW330 (Clariant).
[0150] As acrylic copolymer binder in Coating Compositions M2 and
M5 there may be employed e.g. ACRONAL S320D (BASF).
[0151] As styrene/butadiene polymer binder in Coating Compositions
M1, M3, M4, M6 and M7 there may be employed e.g. INTEX 5584
(Enichem).
[0152] As melamine/formaldehyde resin in Coating Compositions M1
and M3 to M7 there may be employed e.g. Beetle Resin PT-3745
(BIP).
[0153] The melamine polyphosphate of coating composition M7 is of
water solubility<0.1 g/l at 20.degree. C., particle size
distribution: 98%<25 .mu.m and 50%<10 .mu.m, nitrogen content
42-44% and phosphor content 12-14%, e.g. MELAPUR.RTM. 200
(DSM).
[0154] As calcium stearate there may be employed e.g. NOPCOTE C104
(Henkel).
[0155] The 1,2-benz-isothiazolin-3-one fungicide may be employed
e.g. in the form of the commercial product PROXEL BD20
(Avecia).
[0156] The optical brightener in Coating Composition M6 is of
formula 1
[0157] in the form of its sodium salt.
EXAMPLE 1
Blade
[0158] A wood free, surface sized and uncoated paper (100
g/m.sup.2)[made of 50% hardwood, 50% softwood] is coated with
Coating Composition M1 by means of a trailing blade (set 30.degree.
to backing roll), at a pressure of 6 bar/mm, at a speed of 600
m/min to a coating weight of 20 g/m.sup.2 (dry substance), and is
then pre-dried using short wave infrared and completed using
conventional high velocity hot air driers.
[0159] There is obtained an evenly silk finished paper of high
whiteness and with good flame resistance determined by means of NF
P 92-502 (1995).
[0160] Analogously as the Coating Composition M1, Coating
Compositions M2, M3, M6 and M7 are employable in Example 1.
Example 2
Screen
[0161] A wood free, unsized and uncoated paper (150 g/m.sup.2)[made
of 20% hardwood, 80% softwood] is coated with M2 by means of a
screen coater (1 mm mesh), at a pressure of 1 bar, at a speed of
100 m/min to a coating weight of 50 g/m.sup.2 (dry substance), and
is then dried using conventional high velocity hot air driers,
before being embossed at 5 bar.
[0162] There is obtained a decoratively finished paper of high
whiteness and with good flame resistance determined by means of BS
476 (part 7:1987).
[0163] Analogously as the Coating Composition M2, Coating
Compositions M3 and M5 are employable in Example 2.
Example 3
Rod
[0164] A wood free, unsized and uncoated paper (85 g/m.sup.2)[made
of 45% hardwood, 55% softwood] is coated with M3 by means of a
smooth metering rod, at a pressure of 3 bar, at a speed of 600
m/min to a coating weight of 15 g/m.sup.2 (dry substance), and is
then pre-dried using short wave infrared drier and completed using
conventional high velocity hot air driers, before being
super-calendered at 350 kN/m.
[0165] There is obtained a gloss finished paper of high whiteness
and with good flame resistance determined by means of DIN 9102
(part 1).
[0166] Analogously as the Coating Composition M3, Coating
Compositions M1, M2, M4, M5 and M6 are employable in Example 3.
Example 4
Air knife
[0167] A wood free, unsized and uncoated paper (85 g/m.sup.2)[made
of 45% hardwood, 55% softwood] is coated with M4 by means of a
airknife, at a air pressure of 30 Kpa (0.4 mm gap), at a speed of
300 m/min to a coating weight of 15 g/m.sup.2 (dry substance), and
is then pre-dried using short wave infrared drier and completed
using conventional high velocity hot air driers, before being
super-calendered at 350 kN/m.
[0168] There is obtained a gloss finished paper of high whiteness
and with good flame resistance determined by means of DIN 9102
(part 1).
[0169] Analogously as the Coating Composition M4, Coating
Compositions M2, M3 and M5 are employable in Example 4.
Example 5
Air knife
[0170] A wood free, unsized and uncoated paper (90 g/m.sup.2)[made
of 45% hardwood, 55% softwood] is coated with M5 by means of a air
knife, at a air pressure of 30 Kpa (0.4 mm gap), at a speed of 400
m/min to a coating weight of 15 g/m.sup.2 (dry substance), and is
then pre-dried using short wave infrared drier and completed using
conventional high velocity hot air driers, before being calendered
at 100 kN/m.
[0171] There is obtained a matt finished paper of high whiteness
and with good flame resistance determined by means of DIN 9102
(part 1).
[0172] Analogously as the Coating Composition M5, Coating
Compositions M.sub.2, M.sub.3 and M.sub.4 are employable in Example
5.
EXAMPLE 6
Blade
[0173] A wood free, surface sized and uncoated paper (100
g/m.sup.2)[made of 50% hardwood, 50% softwood] is coated with
Coating Composition M1 by means of a trailing blade (set 30.degree.
to backing roll), at a pressure of 6 bar/mm, at a speed of 600
m/min to a coating weight of 20 g/m.sup.2 (dry substance), and is
then pre-dried using short wave infrared and passed through a soft
nip calender located after the last drying section, using a
combination of hard-chilled iron rolls and elastomer-covered
rolls.
[0174] There is obtained an evenly silk finished paper of high
whiteness and with good flame resistance determined by means of NF
P 92-502 (1995).
[0175] Analogously as the Coating Composition M1, Coating
Compositions M2, M3, M6 and M7 are employable in Example 6.
Example 7
Printing
[0176] A wood free, coated paper produced according to Example 1
(120 g/m.sup.2) cut to the dimensions 360 mm.times.520 mm (B3) is
printed with inks conforming to BS 4666 by means of a sheet fed
four colour off-set litho printing press, at a speed of 4000
impressions an hour. There is obtained a high quality print.
[0177] In the same way as the coated paper produced according to
Example 1 there may be printed the papers coated according to each
of Examples 2, 3, 4, 5 and 6.
* * * * *