U.S. patent application number 10/476620 was filed with the patent office on 2004-09-02 for method for recycling pulp rejects.
Invention is credited to Munchow, Dieter.
Application Number | 20040168783 10/476620 |
Document ID | / |
Family ID | 7684031 |
Filed Date | 2004-09-02 |
United States Patent
Application |
20040168783 |
Kind Code |
A1 |
Munchow, Dieter |
September 2, 2004 |
Method for recycling pulp rejects
Abstract
The present invention relates to a process for recycling cleaner
rejects from the preparation of paper, paperboard and cardboard and
to their use for the preparation of paper in the paper stock or as
a coating slurry for the paper industry.
Inventors: |
Munchow, Dieter; (Koln,
DE) |
Correspondence
Address: |
VENABLE, BAETJER, HOWARD AND CIVILETTI, LLP
P.O. BOX 34385
WASHINGTON
DC
20043-9998
US
|
Family ID: |
7684031 |
Appl. No.: |
10/476620 |
Filed: |
March 25, 2004 |
PCT Filed: |
January 24, 2002 |
PCT NO: |
PCT/EP02/00699 |
Current U.S.
Class: |
162/189 ;
162/135; 162/190 |
Current CPC
Class: |
D21H 17/01 20130101;
D21H 19/00 20130101 |
Class at
Publication: |
162/189 ;
162/190; 162/135 |
International
Class: |
D21H 017/01; D21H
019/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 8, 2001 |
DE |
101 22 331.5 |
Claims
1. A process for recycling solid cleaner rejects from the
preparation of paper, paperboard and cardboard, especially from
centrifugal cleaners from the preparation of paper, paperboard and
cardboard, characterized in that cleaner rejects, which contain
fibers, coating pigments and/or fillers, are milled to the desired
grain size distribution, optionally with the addition of water,
coating pigment, fresh filler and/or filler slurry, and employed as
a raw material for the paper stock and/or coating slurry.
2. The process according to claim 1, characterized in that the
separation of the cleaner rejects is effected by flocculation and
sedimentation, filtering, screening and/or centrifuging.
3. The process according to claim 1, characterized in that cleaner
rejects having a concentration of fillers and/or coating pigments
in an amount of from 1 to 99% by weight, especially from 30 to 70%
by weight, based on the solids content, are employed.
4. The process according to claim 3, characterized in that cleaner
rejects having a concentration of fibers in an amount of from 1 to
99% by weight, especially from 30 to 70% by weight, based on the
solids content, are employed.
5. The process according to one or more of claims 1 to 4,
characterized in that said cleaner rejects are milled in the
presence of from 1 to 1000% by weight, especially from 100 to 1000%
by weight, of water, based on the solids content.
6. The process according to one or more of claims 1 to 4,
characterized in that usual milling aids and/or dispersing aids are
added to a slurry having a solids content of from 30 to 85% by
weight, especially from 40 to 75% by weight.
7. The process according to any of claims 1 to 6, characterized in
that usual milling aids and/or dispersing aids are added in an
amount of from 1 to 100% by weight, based on the cleaner
rejects.
8. The process according to one or more of claims 1 to 7,
characterized in that cleaner rejects are milled to a slurry or
powder having a grain size distribution of from 10 to 99% by weight
of particles <1 .mu.m, especially from 10 to 95% by weight of
particles <1 .mu.m, respectively based on the equivalent
diameter.
9. The process according to one or more of claims 1 to 8,
characterized in that cleaner rejects are milled to a powder and/or
slurry having a grain size distribution of a) from 95 to 100% by
weight of particles <10 .mu.m; b) from 50 to 100% by weight of
particles <2 .mu.m, especially from 50 to 95% by weight of
particles <2 .mu.m; c) from 27 to 95% by weight of particles
<1 .mu.m, especially from 27 to 75% by weight of particles <1
.mu.m; and d) from 0.1 to 55% by weight of particles <0.2 .mu.m,
especially from 0.1 to 35% by weight of particles <0.2 .mu.m;
respectively based on the equivalent diameter of the particles.
10. The process according to one or more of claims 1 to 9,
characterized in that the milling of the cleaner rejects is
performed in a dry mill or wet mill, especially in a vertical
agitator ball mill.
11. Use of a cleaner reject slurry according to one or more of the
preceding claims for the preparation of a precoating slurry for the
paper industry, especially of coating slurries for various
segments, such as sheet-fed offset, rotary offset, intaglio
printing, cardboard and special papers.
12. Use of cleaner rejects as a slurry or powder according to any
of claims 1 to 10 to be employed in the stock in papermaking.
Description
[0001] The present invention relates to a process for recycling
cleaner rejects from the preparation of paper, paperboard and
cardboard and to their use for the preparation of paper in the
paper stock or as a coating slurry for the paper industry.
[0002] In the preparation of paper, the raw material, i.e., wood
pulp, wood, fine straw pulp or rag pulp, is also admixed with
repulped half-stock, fillers and pigments in order to achieve a
closed surface and thus to improve the properties of the paper,
especially the whiteness, opacity and printability.
[0003] Almost all papers are admixed with fillers which confer a
uniform formation, improved softness, whiteness and touch
especially to printing and writing papers. These fillers, mostly
called "ashes" since they remain as ashes in the combustion
analysis, are either added to the fiber suspension or applied in
the coating step.
[0004] Uncoated papers contain up to 35% by weight of fillers,
coated papers contain from 25 to 50% by weight thereof. The amount
of fillers employed is highly dependent on the intended use of the
paper. Highly filled papers have a lower strength and poorer sizing
properties.
[0005] The filler content in the paper stock is usually between 5
and 35% by weight and consists of primary pigments or recycled
coating pigments which may be derived from coating residuals or
from coated rejects. In addition to the whiteness of the filler
which is important for whitened papers, its grain size plays an
important role since it has a strong influence on the filler
efficiency and the physical properties of the paper, in particular
porosity. The proportion of filler remaining in the paper is
between 20 and 80% of the amount added to the fiber suspension.
[0006] As judged by their consumption, the following products have
rather great importance today as fillers and coating pigments:
china clay, calcium carbonate, precipitated calcium carbonate
(PCC), artificial aluminum silicates and oxide hydrates, titanium
dioxide, satin white, talcum and calcium silicate.
[0007] Subsequently to their coating with coating slurries, papers
are often smoothed, after drying, with a blade. The so-called
cleaner rejects obtained therein, also referred to as coated
rejects, mainly consist of minerals and fibers and may comprise
from 1 to 4% of the total volume of the paper produced. In most
cases, they are disposed of in dumps. Thus, for example, it has
been proposed to compress and compact the cleaner rejects by screw
extruders in order to reduce their volume. However, the total
amount of the cleaner rejects obtained and passed to disposal is
not reduced.
[0008] In the past, another possibility of treating the cleaner
rejects was to partly process them using centrifugal cleaners in
order to separate the fibers, on the one hand, and/or the coating
pigments and fillers, on the other hand, and reuse them at least in
part.
[0009] It is the object of the present invention to provide a new
environmentally friendly concept for treating the cleaner rejects,
especially from centrifugal cleaners, and to enable them to be
recycled as completely as possible.
[0010] In particular, the object of the invention is to provide a
process for the recycling of cleaner rejects while energy costs and
costs of raw materials, shipping costs as well as costs for dumping
are saved.
[0011] According to the invention, the above object is achieved by
a process for recycling cleaner rejects, especially from
centrifugal cleaners, from the preparation of paper, paperboard and
cardboard, characterized in that cleaner rejects, which contain
fibers, coating pigments and/or fillers, are milled to the desired
grain size distribution, optionally with the addition of water,
coating pigment, fresh filler and/or filler slurry, and employed as
a raw material for the paper stock and/or coating slurry.
[0012] The cleaner rejects, which are usually solid, contain
valuable raw materials which can be recovered by means of the
present invention and, after milling, recycled to various processes
of papermaking. Especially the cleaner rejects from paper mills
which prepare coated paper or cardboard grades contain large
quantities of coating pigment flakes. The thicker the coating
layer, the more difficult is the recovery of the flakes by the
prior art technologies. Double-coated grades or coated cardboard
grades may be mentioned here as particular examples. Another group
of paper industries are the SC-paper producing plants, which lose
large amounts of fillers through cleaner rejects.
[0013] Now, by means of the present invention, the cleaner rejects
are milled and optionally admixed with water, coating pigment,
filler and/or filler slurry. The cleaner reject slurry or the
milled powder is then recycled to the papermaking process for the
paper stock and/or as a coating slurry.
[0014] On a closer inspection of the cleaner rejects, fractions of
fillers, coating pigment flakes, fiber suspension residuals, such
as fiber lumps or splinters, as well as foreign matter, for
example, sand, can be discovered.
[0015] After the milling of the cleaner rejects, the distribution
of the particle sizes of the cleaner rejects is essentially the
same as the original distribution in the coating pigments, fillers
or filler/pigment slurries. Thus, at the same time, by means of the
present invention, more than 95% of the total cleaner rejects, or
even the full amount thereof, can be recovered and recycled to
production.
[0016] Then, the cleaner rejects processed according to the
invention serves, for example, as a filler, whereby the consumption
of fresh filler or pigment can be reduced consistently.
[0017] According to the invention, the milling of the cleaner
rejects is preferably installed in a centrifugal cleaner system
downstream from the last of usually several stages of a centrifugal
cleaner. The accepted stock from the additional cleaner system is
recycled to the previous stage, and the residual amount of the
cleaner rejects forms the final reject.
[0018] In an existing cleaner system, the simplest application area
is intended to comprise installing the milling after the last but
one cleaner stage and employing the last cleaner process as a final
stage.
[0019] When the process according to the invention was performed,
it was found that the distribution of particle sizes of the coating
pigment flakes had been refined and that the original distribution
of the pigment particles had been achieved. This could be seen from
the quantity of finer particles, especially in the differential
distribution. The fiber knots were extracted and predominantly
refined.
[0020] In papermaking, it is usual to employ the fillers and
coating pigments either as powders or in the form of concentrated
slurries with a solids content of preferably from 30 to 85% by
weight for the paper stock or for the preparation of coating
slurries. The fresh fillers and pigments are usually supplied by
the manufacturers with the desired whiteness and grain size
distribution as a slurry or powder.
[0021] In the processing of cleaner rejects, it is of course
required to separate and discard the coarse dirt contents
consisting of splinters, sand grains and other impurities. For this
purpose, multistage centrifugal cleaners are usually employed. The
screenings thus obtained consist of fibers, fillers, pigments, fine
sand, black particles and agglomerates of fillers and pigments, or
pigments, fibers and fillers. "Filler" usually means the fine
particles employed in the paper stock; "pigment" means the fine
particles employed in the coat.
[0022] Known methods which suggest themselves for the separation of
the undesirable contents of the cleaner rejects are flocculation
and sedimentation, filtering, screening and/or centrifuging. In
this case, a mixture of different pigments is usually present which
often contains china clay, calcium carbonate and talcum.
Agglomerates frequently form during the separation processes due to
flocculation and charge reversal; they can now be milled according
to the invention.
[0023] According to the invention, the milling into powders or
slurries can be performed continuously or discontinuously in usual
dry mills or wet mills, especially agitator ball mills, for
example, having a content of from 700 to 5000 l or more. Milling
media, preferably milling balls, especially having a diameter of
from 1 to 4 mm, are used.
[0024] Screens, preferably sieve bends, for separating impurities
(ball crushings, separating materials, rust etc.) are usually used
for processing. Laser measuring instruments serve to determine and
control the milling fineness during the milling process and for the
computer-based control of the agitator ball mill system.
[0025] Therefore, for the preparation of new coating slurries or
also, optionally, for use in the paper stock, it may be required to
enhance the whiteness by per se known methods. The disruption of
agglomerates which adversely affect the flowing properties of a
coating slurry at the blade by forming doctor streaks and adversely
affect the properties of the coat is particularly preferred.
Dispersing aids, fillers and pigments additionally employed in the
milling process reduce the overall consumption of these
materials.
[0026] In the cleaner rejects, the ratio of fillers and/or pigments
to fibers can vary widely. It is particularly preferred according
to the invention to employ cleaner rejects having an optionally
enriched concentration of fillers and/or coating pigments within a
range of from 5 to 90% by weight, especially from 30 to 70% by
weight, based on the solids content. Thus, the fiber content, on
the one hand, or the content of filler and/or coating pigment may
vary, for example, from 1 to 99% by weight, or from 99 to 1% by
weight. "Enrichment" within the meaning of the present invention
especially comprises the addition of fresh filler and/or fresh
pigment.
[0027] Therefore, according to the present invention, china clay,
natural or precipitated calcium carbonates, artificial or natural
aluminum silicates and oxide hydrates, titanium dioxide, satin
white, dolomite, mica, metal flakes, especially aluminum flakes,
bentonite, rutile, magnesium hydroxide, gypsum, sheet silicates,
talcum, calcium silicate and other rocks and earths are preferably
used as the fresh pigment and/or fresh filler before, after and/or
during the milling.
[0028] The fresh pigment or fresh filler is preferably employed as
a powder, aqueous fresh-pigment containing and/or fresh-filler
containing slurries in the presence of the cleaner rejects and
optionally usual milling aids and/or dispersing aids to give a
slurry with a solids content of, for example, from 30 to 85% by
weight, especially from 40 to 75% by weight.
[0029] Preferably, the added amount of fibers, coating pigments
and/or fillers (recycled or fresh) is from 1 to 100% by weight,
based on the cleaner rejects.
[0030] Particularly preferred is the addition of water in order to
employ the cleaner rejects milled according to the invention in a
diluted slurry for the stock flow. Slurries having a solids content
of from 5 to 50% by weight, especially from 10 to 20% by weight,
are preferably employed. Accordingly, in a preferred embodiment
according to the invention, the milling is performed in the
presence of water in an amount of from 1 to 1000% by weight,
especially from 100 to 1000% by weight, based on the solids
content.
[0031] The cleaner rejects are preferably milled to a slurry or
powder having a grain size distribution of from 10 to 99% by weight
of particles <1 .mu.m, especially from 10 to 95% by weight of
particles <1 .mu.m, respectively based on the equivalent
diameter.
[0032] From EP 0 625 611 A1, grain size distributions for coating
pigments are known which are also preferably adjusted by means of
the present invention. Thus, it is particularly preferred according
to the present invention for the pigments to have the following
grain size distribution:
[0033] a) from 95 to 100% by weight of particles <10 .mu.m;
[0034] b) from 50 to 100% by weight of particles <2 .mu.m,
especially from 50 to 95% by weight of particles <2 .mu.m;
[0035] c) from 27 to 95% by weight of particles <1 .mu.m,
especially from 27 to 75% by weight of particles <1 .mu.m;
and
[0036] d) from 0.1 to 55% by weight of particles <0.2 .mu.m,
especially from 0.1 to 35% by weight of particles <0.2
.mu.m;
[0037] respectively based on the equivalent diameter of the
particles.
[0038] In addition, according to the invention, a broad variation
of the whiteness and grain size distributions is possible, which
can be controlled, in particular, by the manner and duration of
milling. Thus, it is possible to mix a relatively coarse fresh
filler and water in situ with a large amount of cleaner rejects for
introducing this slurry into the paper stock after milling. In the
same way, it is possible to use a smaller amount of cleaner rejects
and to perform a finer milling with fresh pigment in situ which is
then used as a coating pigment, especially in precoating.
[0039] Even though per se known wetting agents, stabilizers,
milling aids and dispersing aids may be employed according to the
invention during the mixing and milling of the cleaner rejects, as
known, for example, from EP 0 625 611 A1, the quantity thereof
required is clearly reduced according to the invention as compared
to the prior art. The cleaner rejects already contain some amount
of the mentioned agents which are recycled to the papermaking
process according to the invention.
[0040] The powders or slurries obtainable according to the present
invention may be employed to particular advantage in the paper
industry, especially for the preparation of a coat for paper
coating or in the paper stock. When the fiber content is low, the
cleaner rejects milled according to the invention is preferably
employed in the coating slurry, and when the fiber content is high,
it is preferably employed in the paper stock. According to the
invention, a good retention on the screen is obtained. Particularly
preferred is the use of the cleaner rejects milled according to the
invention for the preparation of offset paper. In addition, the
slurries according to the invention are also suitable for the
preparation of a coating slurry for light-weight coated papers,
especially with high coating speeds, and for the preparation of
rotary offset papers, especially for the preparation of
light-weight coated rotary offset papers, the coating of cardboard
and special papers, such as labels, wallpapers, silicone base
paper, self-copying paper, and for admixture with intaglio printing
paper. Thus, the coating pigment slurries obtainable according to
the invention may be employed, in particular, in sheet-fed offset
papers, especially for sheet-fed offset single coating, sheet-fed
offset double coating: sheet-fed offset precoating and sheet-fed
offset top coating; in rotary offset papers, especially for LWC
rotary offset single coating, rotary offset double coating: rotary
offset precoating and rotary offset top coating; in intaglio
printing, especially for LWC intaglio single coating, intaglio
double coating: intaglio precoating and intaglio top coating; in
cardboard, especially for cardboard double coating: cardboard
precoating and cardboard top coating; and for special papers,
especially for labels and flexible packings.
[0041] The process offers the opportunity to employ the pigment
slurries prepared according to the invention without a loss in
quality in the base papers, coatings and especially final qualities
prepared therewith.
[0042] In the following, some coating formulations which can be
obtained according to the present invention are given for
illustrative purposes (all figures converted to weight parts of
solids (atro/active ingredient)). The amounts of fillers and/or
pigment slurries can be partly or wholly replaced by corresponding
amounts of cleaner rejects milled according to the invention.
[0043] 1. Sheet-Fed Offset Paper
[0044] 1.1 Sheet-Fed Offset Single Coating
[0045] 70 parts by weight of commercially available CaCO.sub.3
(type 90)
[0046] 30 parts by weight of commercially available clay (fine,
e.g., U.S. No. 1)
[0047] 11 parts by weight of commercially available latex
(acrylate)
[0048] 0.6 parts by weight of commercially available
carboxymethylcellulose (CMC)
[0049] 0.8 parts by weight of commercially available hardener
(urea-formaldehyde, melamine-formaldehyde, epoxy resin)
[0050] 0.5 parts by weight of commercially available brightener
(opt.)
[0051] 0.5 parts by weight of commercially available Ca
stearate
1 solids content: 64% Brookfield viscosity (100/min): 1,200 mPa
.multidot. s pH value: 8.5
[0052] 1.2 Sheet-Fed Offset Double Coating
[0053] 1.2.1 Sheet-Fed Offset Precoating
[0054] 100 parts by weight of commercially available CaCO.sub.3
(type 60 or 75)
[0055] 10 parts by weight of commercially available latex
[0056] 4 parts by weight of commercially available starch (native,
oxidized, corn or potato starch)
[0057] 0.8 parts by weight of commercially available hardener
(urea-formaldehyde, melamine-formaldehyde, epoxy resin)
[0058] 0.5 parts by weight of commercially available brightener
(opt.)
2 solids content: 66% Brookfield viscosity (100/min): 1,100 mPa
.multidot. s pH value: 9.0
[0059] 1.2.2 Sheet-Fed Offset Top Coating
[0060] 70 parts by weight of commercially available CaCO.sub.3
(type 90)
[0061] 30 parts by weight of commercially available clay (fine,
e.g.; U.S. No. 1)
[0062] 10 parts by weight of commercially available latex
(acrylate)
[0063] 0.6 parts by weight of commercially available CMC
[0064] 0.8 parts by weight of commercially available hardener
(urea-formaldehyde, melamine-formaldehyde, epoxy resin)
[0065] 0.5 parts by weight of commercially available brightener
(opt.)
[0066] 0.7 parts by weight of commercially available Ca
stearate
3 solids content: 64% Brookfield viscosity (100/min): 1,200 mPa
.multidot. s pH value: 8.5
[0067] 2. Rotary Offset Paper
[0068] 2.1 LWC Rotary Offset Single Coating
[0069] 50 parts by weight of commercially available CaCO.sub.3
(type 90)
[0070] 50 parts by weight of commercially available clay (fine,
Engl. clay)
[0071] 2 parts by weight of commercially available starch (native,
oxidized, corn or potato starch)
[0072] 12 parts by weight of commercially available latex (XSB)
[0073] 0.8 parts by weight of commercially available hardener
(urea-formaldehyde, melamine-formaldehyde, epoxy resin)
[0074] 0.7 parts by weight of commercially available brightener
(opt.)
[0075] 0.5 parts by weight of commercially available Ca
stearate
4 solids content: 62% Brookfield viscosity (100/min): 1,400 mPa
.multidot. s pH value: 8.5
[0076] 2.2 Rotary Offset Double Coating
[0077] 2.2.1 Rotary Offset Precoating
[0078] 100 parts by weight of commercially available CaCO.sub.3
(type 60 or 75)
[0079] 4 parts by weight of commercially available starch (native,
oxidized, corn or potato starch)
[0080] 12 parts by weight of commercially available latex (XSB)
[0081] 0.8 parts by weight of commercially available hardener
(urea-formaldehyde, melamine-formaldehyde, epoxy resin)
[0082] 0.5 parts by weight of commercially available brightener
(opt.)
5 solids content: 66% Brookfield viscosity (100/min): 1,200 mPa
.multidot. s pH value: 9.0
[0083] 2.2.2 Rotary Offset Ton Coating
[0084] 60 parts by weight of commercially available CaCO.sub.3
(type 95)
[0085] 40 parts by weight of commercially available clay (fine,
Engl. clay)
[0086] 10 parts by weight of commercially available latex (XSB)
[0087] 0.6 parts by weight of commercially available CMC
[0088] 0.8 parts by weight of commercially available hardener
(urea-formaldehyde, melamine-formaldehyde, epoxy resin)
[0089] 0.5 parts by weight of commercially available brightener
(opt.)
[0090] 0.5 parts by weight of commercially available Ca
stearate
6 solids content: 64% Brookfield viscosity (100/min): 1,200 mPa
.multidot. s pH value: 8.5
[0091] 3. Intaglio Printing Paper
[0092] 3.1 LWC Intaglio Single Coating
[0093] 70 parts by weight of commercially available clay (normal,
Engl. clay)
[0094] 30 parts by weight of commercially available talcum
[0095] 5.0 parts by weight of commercially available latex
(acrylate sole binder)
[0096] 0.2 parts by weight of commercially available thickener
(synthetic)
[0097] 1.0 parts by weight of commercially available Ca
stearate
7 solids content: 58% Brookfield viscosity (100/min): 1,200 mPa
.multidot. s pH value: 8.5
[0098] 3.2 Intaglio Double Coating
[0099] 3.2.1 Intaglio Precoating
[0100] 100 parts by weight of commercially available CaCO.sub.3
(type 75)
[0101] 6.0 parts by weight of commercially available latex
(acrylate sole binder)
[0102] 0.3 parts by weight of commercially available thickener
(synthetic)
[0103] 0.5 parts by weight of commercially available Ca
stearate
8 solids content: 66% Brookfield viscosity (100/min): 1,200 mPa
.multidot. s pH value: 9.0
[0104] 3.2.2 Intaglio Top Coating
[0105] 85 parts by weight of commercially available clay (Engl.
clay)
[0106] 15 parts by weight of commercially available clay (calcined
clay)
[0107] 5.0 parts by weight of commercially available latex
(acrylate sole binder)
[0108] 0.2 parts by weight of commercially available thickener
(synthetic)
[0109] 0.8 parts by weight of commercially available Ca
stearate
9 solids content: 57% Brookfield viscosity (100/min): 1,300 mPa
.multidot. s pH value: 8.5
[0110] 4. Cardboard
[0111] 4.1 Cardboard Double Coating
[0112] 4.1.1 Cardboard Precoating
[0113] 100 parts by weight of commercially available CaCO.sub.3
(type 75)
[0114] 3 parts by weight of commercially available starch (native,
oxidized, corn or potato starch)
[0115] 14 parts by weight of commercially available latex (XSB)
[0116] 0.8 parts by weight of commercially available hardener
(urea-formaldehyde, melamine-formaldehyde, epoxy resin)
[0117] 0.5 parts by weight of commercially available brightener
(opt.)
10 solids content: 66% Brookfield viscosity (100/min): 1,000 mPa
.multidot. s pH value: 9.0
[0118] 4.1.2 Cardboard Top Coating
[0119] 50 parts by weight of commercially available CaCO.sub.3
(type 90)
[0120] 50 parts by weight of commercially available clay
(fine/Engl. clay)
[0121] 13 parts by weight of commercially available latex
(acrylate)
[0122] 2 parts by weight of commercially available co-binder
(acrylate)
[0123] 0.8 parts by weight of commercially available hardener
(urea-formaldehyde, melamine-formaldehyde, epoxy resin)
[0124] 0.6 parts by weight of commercially available Ca
stearate
11 solids content: 60% Brookfield viscosity (100/min): 1,200 mPa
.multidot. s pH value: 8.5
[0125] 5. Special Papers
[0126] 5.1. Labels
[0127] 70 parts by weight of commercially available clay
(normal/Engl. clay)
[0128] 10 parts by weight of commercially available TiO.sub.2
(rutile)
[0129] 20 parts by weight of commercially available CaCO.sub.3
(type 90)
[0130] 16 parts by weight of commercially available latex (XSB)
[0131] 0.5 parts by weight of commercially available hardener (EH)
(urea-formaldehyde, melamine-formaldehyde, epoxy resin)
[0132] 0.6 parts by weight of commercially available Ca
stearate
12 solids content: 60% Brookfield viscosity (100/min): 1,200 mPa
.multidot. s pH value: 8.5
[0133] 5.2 Flexible Packing
[0134] 80 parts by weight of commercially available clay (normal,
Engl. clay)
[0135] 20 parts by weight of commercially available CaCO.sub.3
(type 90)
[0136] 14 parts by weight of commercially available latex
(acrylate)
[0137] 0.8 parts by weight of commercially available CMC
[0138] 0.5 parts by weight of commercially available hardener
(urea-formaldehyde, melamine-formaldehyde, epoxy resin)
[0139] 0.6 parts by weight of commercially available brightener
(opt.)
[0140] 1.0 parts by weight of commercially available Ca
stearate
13 solids content: 58% Brookfield viscosity (100/min): 1,200 mPa
.multidot. s pH value: 8.5
EXAMPLE
[0141] Cleaner rejects from the process of a commercially available
papermaking machine of the prior art were milled in a 15% by weight
suspension to a slurry having a grain size of <10 .mu.m and
added to the stock flow of the paper stock.
[0142] Shortly after the connecting of the milling installation
with the cleaner rejects milled according to the invention, an
increase of the ashes content in the paper could be
established.
[0143] The ashes content increased, and the dosage of filler could
be consequently reduced. From the milling installation, about 16 to
18 l/min of pigment slurry consisting of milled cleaner rejects was
supplied to the pulp chest. To maintain the ashes content on the
predetermined constant level, the usual dosage of fresh filler
could be reduced from 10 l/h to 6.0 l/h.
[0144] In the covered period, the milling installation ran without
trouble. The ashes content of the stock flow varied to the usual
extent. The retention slightly decreased initially, but increased
to the usual values in the course of the experiment. The amount
saved was about 240 l/h of fresh pigment slurry.
[0145] The test run over about 10 hours showed that the processed
cleaner rejects can be employed again as a filler in the stock by
the process according to the invention without retention loss.
[0146] Statements relating to the composition of the cleaner reject
slurries:
14 solids content: about 24.0% pigment proportion: about 85.0%,
based on the solids content fiber proportion: about 15.0%, based on
the solids content
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