U.S. patent application number 11/659523 was filed with the patent office on 2008-12-11 for paper product with increased relative wet tensile strength and softness, method for production and use thereof.
Invention is credited to Stefano Bruzzano, Stephan Eichhorn, Andre Laschewsky, Nathalie Sieverling, Siegfried Stapel, Joachim Storsberg.
Application Number | 20080302497 11/659523 |
Document ID | / |
Family ID | 34981292 |
Filed Date | 2008-12-11 |
United States Patent
Application |
20080302497 |
Kind Code |
A1 |
Storsberg; Joachim ; et
al. |
December 11, 2008 |
Paper Product with Increased Relative Wet Tensile Strength and
Softness, Method for Production and Use Thereof
Abstract
The present invention relates to flat paper products having an
increased relative wet strength and softness, a method for the
production of the same and also the use of paper products of this
type in the form of tissue products. This is achieved by a
cross-linkage of the cellulose fibres contained in the paper
product with a cationic graft copolymer which is constructed on the
basis of polyethyleneoxide- or polyethyleneglycol segments and
polyethyleneimine segments.
Inventors: |
Storsberg; Joachim;
(Woerrstadt, DE) ; Bruzzano; Stefano; (Potsdam,
DE) ; Laschewsky; Andre; (Potsdam, DE) ;
Sieverling; Nathalie; (Potsdam, DE) ; Eichhorn;
Stephan; (Gernsheim, DE) ; Stapel; Siegfried;
(Mannheim, DE) |
Correspondence
Address: |
BARNES & THORNBURG LLP
11 SOUTH MERIDIAN
INDIANAPOLIS
IN
46204
US
|
Family ID: |
34981292 |
Appl. No.: |
11/659523 |
Filed: |
July 21, 2005 |
PCT Filed: |
July 21, 2005 |
PCT NO: |
PCT/EP2005/007962 |
371 Date: |
September 21, 2007 |
Current U.S.
Class: |
162/164.6 |
Current CPC
Class: |
C08G 73/0206 20130101;
D21H 17/56 20130101; D21H 21/20 20130101; C08G 73/024 20130101;
D21H 17/53 20130101 |
Class at
Publication: |
162/164.6 |
International
Class: |
D21H 17/54 20060101
D21H017/54 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 5, 2004 |
DE |
102004038132.1 |
Claims
1. A paper product having increased relative wet strength and
softness containing cellulose fibers which are cross-linked with a
graft copolymer comprising a polyethyleneimine segment of the
general formula I ##STR00005## x, y and z being chosen such that
the molar mass is in the range of 1000 to 2000000 D, and at least
one of a polyalkyleneoxide segment and a polyalkyleneglycol segment
of the general formula II, ##STR00006## with R.sub.1 and R.sub.2
independently of each other C.sub.1-C.sub.12-alkyl, and n being
chosen such that the molar mass thereof is in the range of 350 to
2000000 D.
2. The paper product according to claim 1 the graft copolymer has a
backbone comprising polyethyleneimine and grafts comprising at
least one polyalkyleneoxide and/or at least one
polyalkyleneglycol.
3. The paper product according to claim 1 wherein the graft
copolymer has a backbone comprising at least one polyalkyleneoxide
and/or at least one polyalkyleneglycol and grafts comprising
polyethyleneimine.
4. The paper product according to claim 1 wherein the
polyethyleneimine is linear.
5. The paper product according to claim 1 wherein the
polyethyleneimine is branched.
6. The paper product according to claim 1 wherein the
polyethyleneimine has a molar mass in the range of 20000 to 1000000
D.
7. The paper product according to claim 1 wherein the
polyalkyleneglycol is polyethyleneglycol.
8. The paper product according to claim 1 wherein the
polyalkyleneoxide is polyethyleneoxide.
9. The paper product according to claim 1 wherein the
polyalkyleneglycol and/or the polyalkyleneoxide has a molar mass in
the range of 350 to 1000000 D, in particular 350 to 80000 D.
10. The paper product according to claim 1 wherein a terminal
hydroxyl group of the polyalkyleneoxide and/or of the
polyalkyleneglycol is blocked.
11. The paper product according to claim 10 wherein the terminal
hydroxy group is blocked with a methoxy, ethoxy, propyloxy,
butyloxy and/or benzyloxy group.
12. A method for the production of flat paper products having an
increased relative wet strength and softness from a pulp stock, the
method comprising at least one of adding to the pulp stock, adding
to the paper product during production, and adding to the paper
product after production a graft copolymer comprising a
polyethyleneimine segment of the general formula I ##STR00007## x,
y and z being chosen such that the molar mass is in the range of
1000 to 2000000 D, and at least one of a polyalkyleneoxide segment
and a polyalkyleneglycol segment of the general formula II,
##STR00008## with R1 and R2 independently of each other
C1-C12-alkyl, and n being chosen such that the molar mass thereof
is in the range of 350 to 2000000 D.
13. The method according to claim 12 wherein said at least one of
adding to the pulp stock, adding to the paper product during
production, and adding to the paper product after production a
graft copolymer comprising a polyethyleneimine segment and at least
one of a polyalkyleneoxide segment and a polyalkyleneglycol segment
comprises at least one of adding to the pulp stock, adding to the
paper product during production, and adding to the paper product
after production a graft copolymer having a backbone comprising
polyethyleneimine and grafts comprising at least one of a
polyalkyleneoxide and a polyalkyleneglycol.
14. The method according to claim 12 wherein said at least one of
adding to the pulp stock, adding to the paper product during
production, and adding to the paper product after production a
graft copolymer comprising a polyethyleneimine segment and at least
one of a polyalkyleneoxide segment and a polyalkyleneglycol segment
comprises at least one of adding to the pulp stock, adding to the
paper product during production, and adding to the paper product
after production a graft copolymer having a backbone comprising at
least one of a polyalkyleneoxide and a polyalkyleneglycol and
grafts comprising polyethyleneimine.
15. The method according to claim 12 wherein said at least one of
adding to the pulp stock, adding to the paper product during
production, and adding to the paper product after production a
graft copolymer comprising a polyethyleneimine segment and at least
one of a polyalkyleneoxide segment and a polyalkyleneglycol segment
comprises adding a polyethyleneglycol segment.
16. The method according to claim 12 wherein said at least one of
adding to the pulp stock, adding to the paper product during
production, and adding to the paper product after production a
graft copolymer comprising a polyethyleneimine segment and at least
one of a polyalkyleneoxide segment and a polyalkyleneglycol segment
comprises adding a polyethyleneoxide segment.
17. The method according to claim 12 wherein adding a graft
copolymer comprising a polyethyleneimine segment comprises adding a
polyethyleneimine segment having a weight, relative to the initial
compounds, greater than 50% by weight.
18. The method according to claim 17 wherein adding a graft
copolymer comprising a polyethyleneimine segment comprises adding a
polyethyleneimine segment having a weight, relative to the initial
compounds, greater than 80% by weight.
19. The method according to claim 17 wherein adding a graft
copolymer comprising a polyethyleneimine segment comprises adding a
polyethyleneimine segment having a weight, relative to the initial
compounds, greater than 90% by weight.
20. The method according to claim 12 wherein said at least one of
adding to the pulp stock, adding to the paper product during
production, and adding to the paper product after production a
graft copolymer comprising a polyethyleneimine segment and at least
one of a polyalkyleneoxide segment and a polyalkyleneglycol segment
comprises at least one of adding a polyalkyleneoxide segment having
a blocked terminal hydroxyl group and adding a polyalkyleneglycol
segment having a blocked terminal hydroxyl group.
21. The method according to claim 20 wherein said at least one of
adding a polyalkyleneoxide segment having a blocked terminal
hydroxyl group and adding a polyalkyleneglycol having a blocked
terminal hydroxyl group comprises at least one of adding a
polyalkyleneoxide segment having a terminal hydroxyl group blocked
by one of a methoxy group, an ethoxy group, a propyloxy group, a
butyloxy group and a benzyloxy group, and adding a
polyalkyleneglycol having a terminal hydroxyl group blocked by one
of a methoxy group, an ethoxy group, a propyloxy group, a butyloxy
group and a benzyloxy group.
22. The method according to claim 12 further comprising converting
a free terminal hydroxy group of said at least one of the
polyalkyleneoxide and the polyalkyleneglycol with an
epihalogenhydrin into a polyethyleneglycol glycidyl ether and
grafting said polyethyleneglycol glycidyl ether onto the
polyethyleneimine via the amine groups.
23. Use of the paper products according to claim 1 as tissue
product.
Description
[0001] The present invention relates to flat paper products having
increased relative wet strength and softness, a method for the
production of the same and the use of paper products of this type
in the form of tissue products. This is achieved by cross-linkage
of the cellulose fibres contained in the paper product with a
cationic graft copolymer which is constructed on the basis of
polyethyleneoxide- or polyethyleneglycol segments and
polyethyleneimine segments.
[0002] The mutual cross-linkage of cellulose fibres in the paper
production process is crucial for the quality and the properties of
the produced paper. Without adhesives, cellulose fibres mainly form
only hydrogen bonds at the intersection points. Such paper has no
wet strength and has only a restricted elasticity or softness.
There is understood by wet strength the strength of papers in the
completely saturated state. In order to improve the adhesion of the
cellulose fibres to each other and hence the usage properties of
the paper, polymer adhesives inter alia on an epichlorohydrin base
or on a polyacrylamide base are used worldwide as so-called wet
strength agents.
[0003] The cellulose fibres used during paper production are
negatively charged. For a simple and economical paper production
method which is known to the person skilled in the art, it is most
favourable if treatment chemicals, e.g. wet strength agents, are
metered directly into the aqueous pulp stock with which the paper
is then produced. The industrial tissue production process may be
explained subsequently in brief.
[0004] The aqueous pulp stock is then passed during the industrial
process to the machine wire(s), is formed there and partly drained
and passes subsequently into the dry part of the tissue machine. In
the dry part there is the so-called steam-heated yankee cylinder
which has a surface temperature of 80 to 140.degree. C. In
addition, one or more gas-heated hoods can be situated thereabove
through which hoods hot air is blown onto the tissue web. The air
is heated for this purpose to temperatures of 200 to 750.degree. C.
During an extremely short contact time of a few ms on the cylinder,
the hardening process of the wet strength agents begins which is
concluded during the subsequent storage of the finished tissue web,
the so-called subsequent ripening.
[0005] In order that a potential wet strength agent can be absorbed
onto the cellulose fibre during application on the pulp stock, said
agent is advantageously water-soluble or water-dispersible and
cationic since the cellulose fibres used during paper production
are negatively charged. Therefore the use of cationic polymers as
wet strength agents in the paper or tissue industry, which are
based in part on very different chemical structurings such as
polyamides or polyacrylamides, is regarded as current state of the
art. These wet strength agents are normally added in quantities of
8 to 10 kg/tonne for household tissues. The cellulose fibres of the
paper or tissues hold together in the dry state in the network of a
sheet by means of fibre-fibre contact points which are based on van
der Waals or hydrogen bonds. These bonds are very sensitive to
water, i.e. the more moist the tissue becomes, the looser these
bonds become. In order to be able to produce so-called wet strength
papers, such as e.g. kitchen or household towel or toilet tissue,
wet strength agents are added which have the task of forming bonds
which are at least temporarily resistant to water. According to the
current state of the art, various chemically based polymer wet
strength agents are available in paper or tissue production which
are described in the relevant literature, e.g. in "Papermaking
Chemistry", Book 4, Ed. Leo Neimo, pp. 288-301. There are used
predominantly, melamine-formaldehyde resins (MF) (U.S. Pat. No.
4,461,858) and cationic polymers based on polyamide-epichlorohydrin
(PAE) and polyamidoamine-epichlorohydrin (PAAE) (U.S. Pat. No.
2,926,116, U.S. Pat. No. 2,926,154, U.S. Pat. No. 3,733,290, U.S.
Pat. No. 4,566,943, U.S. Pat. No. 4,605,702).
[0006] A disadvantage with the above-mentioned wet strength agents
is, on the one hand, that the treated tissue does in fact have
increased wet strength but has reduced softness. The sought
softness must then be achieved by an additional mechanical
treatment of the tissue. A further disadvantage of the PAEs is the
production-caused content of organic halogen compounds. WO 00/40639
describes a PAE-based wet strength agent with a low content of
organically bonded chlorine. Furthermore, water-dispersible wet
strength agents based on polyisocyanate are described in DE 196 40
205 A1, which are obtained by conversion of the initial components
polyisocyanate, polyalkyleneoxide polyether alcohol, of a
quaternised aminopolyalkyleneoxide polyether alcohol and also
possibly further auxiliary materials and additives. Furthermore, DE
698 14 359 T2 teaches that e.g. polyethyleneimine belongs to the
temporary wet strength agents.
[0007] Furthermore, it is known to the person skilled in the art
that polymers which have a low glass transition point, i.e.
.ltoreq.RT, have soft properties. DE 689 16 860 describes in detail
a method for the production of absorbent structures in which the
absorbing structures are produced from mixed paper raw materials,
of which one is treated with a latex with an elastomer core. The
softness is hereby achieved by the latex with the low glass
transition point. In order that the latices are absorbed onto the
cellulose fibre in the wet method, the latter have a polymer shell
based on oleyl polyethoxylate which carries a quaternary functional
(trimethyl) ammonium group at the end of the ethoxylate chain. It
is however disadvantageous with this method that the soft latices
are of a hydrophobic nature and hence have a negative influence on
the absorption capacity of the paper produced therefrom in a single
"one batch" application. Hence with this method various pulp stocks
must be worked with, only one of which is treated with the latex.
In a further step, the pulp stock treated with latex is mixed with
an untreated fibre suspension in order thus to achieve the
water-absorbing effect of the paper. WO 96/33310 describes a method
for the production of soft-creped tissue which is obtained by a
specially controlled production process, mainly by mechanical
treatment.
[0008] It is therefore the object of the present invention to
develop a wet strength agent which overcomes the above-mentioned
problems. The wet strength should thereby be increased without
having negative effects on the softness. At the same time, the
absorption of the paper should also not be negatively affected.
Furthermore, the application of chemicals should be effected in as
simple a manner as possible directly in the pulp or during
production of the paper product. Multistage methods, such as e.g.
mixing of treated pulp with untreated pulp as described for example
in DE 689 16 860 T2, should however be avoided. Furthermore, the
use of organically bonded halogens in the treatment chemicals
should be avoided.
[0009] This object is achieved by the paper product having the
features of claim 1 and the method for the production of the paper
product having the features of claim 12. The further dependent
claims reveal advantageous developments. In claim 23, the use of
the paper product according to the invention is described.
[0010] According to the invention, a paper product with increased
relative wet strength and softness is provided, which contains
cellulose fibres which are cross-linked with a graft copolymer
comprising a polyethyleneimine segment of the general formula
I,
##STR00001##
x, y and z being chosen such that the molar mass of the
polyethyleneimine segment is in the range of 1000 to 2000000
dalton, and also at least one polyalkyleneoxide- and/or at least
one polyalkyleneglycol segment of the general formula II,
##STR00002##
with R.sub.1 and R.sub.2 independently of each other C.sub.1 to
C.sub.12-alkyl, n being chosen such that the molar mass of the
polyalkyleneoxide- or polyalkyleneglycol segment is in the range of
350 to 2000000 dalton.
[0011] It was found surprisingly that by applying graft
copolymerisation in the aqueous pulp stock which comprises branched
or linear polyethyleneimine (PEI) on which polyalkyleneglycol- or
polyalkyleneoxide segments were grafted, i.e. were cross-linked
chemically with the N-atoms of the PEI by covalent bonding, the
above-mentioned problems can be overcome. Alternatively, the
above-mentioned problems can be overcome by the application of
graft copolymerisation in the aqueous pulp stock which comprises
polyalkyleneglycol- or polyalkyleneoxide segments onto which
polyethyleneimine was grafted. The above-mentioned problems are
however not overcome if mixtures of polyalkyleneglycol homopolymer
and PEI homopolymer or only polyalkyleneglycol homopolymer or only
PEI homopolymer are used. The effect according to the invention is
achieved only by the grafted polymer structure.
[0012] Preferably the backbone of the graft copolymer comprises
polyethyleneimine, there being bonded to the latter grafts
comprising at least one polyalkyleneoxide and/or at least one
polyalkyleneglycol. Another variant provides that the graft
copolymer has a backbone comprising at least one polyalkyleneoxide
and/or at least one polyalkyleneglycol, grafts comprising
polyethyleneimine then being present.
[0013] Preferably the graft copolymer comprises polyethyleneimine
with a molar mass in the range of 20000 to 1000000 dalton.
[0014] Preferably polyethyleneglycol is used as polyalkyleneglycol
or preferably polyethyleneoxide as polyalkyleneoxide. These thereby
have preferably a molar mass in the range of 350 to 1000000 dalton,
particularly preferred of 350 to 80000 dalton.
[0015] A terminal hydroxyl group of the polyalkyleneoxide and/or
polyalkyleneglycol is preferably blocked. Preferably the terminal
hydroxy group is thereby blocked with a methoxy, ethoxy, propyloxy,
butyloxy and/or benzyloxy group. The free terminal hydroxyl group
of the polyalkyleneglycol or polyalkyleneoxide is converted into a
chemical-reactive group, i.e. by reaction with epihalogenhydrin by
forming a polyethyleneglycolglycidyl ether. Polyalkyleneglycols
modified in this manner then form, by chemical reaction with the
primary and secondary amine groups of the polyethyleneimine, the
graft copolymers which are desired for the paper products according
to the invention.
[0016] According to the invention, likewise a method for the
production of flat paper products with increased relative wet
strength and softness is provided from a pulp stock, in which there
is added to the pulp stock a graft copolymer comprising a
polyethyleneimine segment of the general formula I
##STR00003##
x, y, z being chosen such that the molar mass is in the range of
1000 to 2000000 dalton, and also at least one polyalkyleneoxide-
and/or at least one polyalkyleneglycol segment of the general
formula II
##STR00004##
with R.sub.1 and R.sub.2 independently of each other C.sub.1 to
C.sub.12-alkyl and n being chosen such that the molar mass thereof
is in the range of 350 to 2000000 dalton, and/or the paper product
is treated during production thereof or subsequently with the graft
copolymer.
[0017] Polyalkyleneglycols can be coupled with polyethyleneimine by
various methods in order thus to obtain the desired graft
copolymers. Sung et al. (Biol. Pharm, Bull. 26(4), 492-500 (2003)
describe the synthesis of polyalkyleneglycols grafted on PEI. They
begin thereby in the synthesis of a polyethyleneglycol (MPEG) which
is terminated on one side with a methyl group and is converted with
epichlorohydrin with base effect into an epoxy-terminated MPEG.
This epoxy-terminated MPEG is grafted onto the PEI in a further
synthesis step so that a graft copolymer is obtained. By varying
the MPEG molecular weights which are used and also from the ratio
of epoxy-terminated MPEG to PEI, different structures with
different graft degrees and lengths of the graft branches can be
synthesised.
[0018] A further method of synthesising graft copolymers based on
polyalkyleneglycol-polyethyleneimine resides in bonding a
polyalkyleneglycol carboxylic acid, by the coupling methods
currently known from peptide chemistry, to the primary or secondary
amine groups of the PEI by linkage of peptide bonds. The current
coupling methods, e.g. with the help of carbodiimides are described
for example in "Amino acids, Peptides, Proteins", H. Jakubke, H.
Jeschkeit, Licensed Edition for the Chemistry Press, Weinheim,
1982, ISBN 3-527-25892-2. More recent coupling methods with
water-soluble coupling reagents, such as e.g.
N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride are
described for example in Sheehan et al. (J. Am. Chem. Soc. 95, 875
(1973)), Nozaki et al. (Bull. Chem. Soc. Jpn. 55, 2165 (1982)) and
Schmidt et al. (J. Chem. Soc. Chem. Commun. 1687 (1992)).
[0019] It is also possible with the above-mentioned methods to
graft polyethyleneimines onto polyethyleneglycols. This is possible
for example by using bifunctional polyethyleneglycols, such as e.g.
polyethyleneglycol diacids or polyethyleneglycolbisglycidyl
ether.
[0020] Particularly preferred are coupling methods with activators
which permit coupling under aqueous conditions, such as e.g.
N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride. The
coupling can be implemented in principle also with organic
water-free solvents by means of carbodiimides and carbonyl
diimidazoles.
[0021] The above-mentioned graft copolymer is added as an additive
to a paper product, in particular to a so-called tissue product.
Further paper products, to which the described graft copolymer can
be added as additive are inter alia graph paper, newspaper,
cardboard, copy paper and special papers, such as for example
banknotes or even filter papers. A so-called tissue paper, which
tissue products comprise, differs from normal papers in particular
by its very low basis weight of normally less than 40
g/m.sup.2.
[0022] In general there are described as "tissue papers" or better
as raw tissue papers the single-layer intermediate products, which
come from the paper machine, comprising light papers, i.e. produced
with a low basis weight, which were dry-creped as a rule on a
so-called yankee cylinder with the help of a crepe scraper. The
single-layer raw tissue comprising respectively one or more layers
can thereby be constructed.
[0023] There are termed as "tissue products" all the single or
multilayer end products which are produced from raw tissue and
orientated to the requirements of the end user, i.e. are
manufactured with the most varied of requirement profiles.
[0024] Typical properties of tissue papers are the good capacity to
absorb strength energy, their drapability, good textile-like
flexibility, properties which are often termed as crumple-softness,
high surface softness, a high specific volume with a tactile
thickness, as high a liquid absorption capacity as possible and,
according to the application, a suitable wet and dry strength and
also an interesting optical appearance of the outer product
surface. Because of these properties, tissue papers are processed
into tissue products (tissue paper products) and are then available
to the end user in the most varied of forms and assemblies, for
example as wipes, handkerchiefs, household towels, in particular as
kitchen towels, as sanitary products, (e.g. toilet papers), as
paper tissues, cosmetic tissues or serviettes.
[0025] For successful use of tissue products in the most varied of
application areas, dependent upon the purpose of use, frequently
different and partly contradictory properties are required.
[0026] Tissue papers are produced nowadays as a rule by three
different methods. These methods are: [0027] the wet crepe process
[0028] the dry crepe process and [0029] the through air drying
process
[0030] The methods differ as a result of the construction of the
tissue machine. In the case of the through air drying process, the
press for mechanical draining of the tissue web is therefore
replaced by throughflow cylinders through which hot air is blown
(energetic drying). Also the construction of the so-called wire
part, in which the web is formed and partially drained, can be
different. The sheet formation can be formed on only one wire
(breast roller former) between two wires (C-wrap or S-wrap former)
or between one wire and a felt (crescent former).
[0031] Despite these differences, all the plants have a similarly
constructed so-called constant part. This differs mainly in whether
the material inlet is operated with only one or several layers. If
multilayer tissue papers are produced according to the so-called
multilayer method, some units, such as e.g. the material inlet
pump, must be present whenever the finished tissue paper is
intended to have layers.
[0032] The constant part of a tissue machine begins with the pulper
in which dried pulp is dissolved or with a stacked tower in which
up to several hundred cubic meters of pulp stock can be stored and
ends at the material inlet. Since in a plurality of circulations
material-water suspensions are returned from the machine to
different points in the constant part, these circulations also fall
in the constant part region (e.g. wire water or machine rejects).
Pulpers are used if dried pulp is to be broken up. This pulp is
delivered as a rule from an external pulp factory. Stacked towers
are used if pulp is produced in the same works (integrated factory)
or waste paper is processed. These two raw materials are then not
dried before use on the tissue but only drained up to a material
density of maximum 25% (250 g fibres in 1 l water) in order to
separate the circulations of the tissue machine and the pulp
factory or waste paper processing.
[0033] In tissue production, the most varied of pulps or types of
waste paper can be used as fibre material. Both sulphate and
sulphite pulps are used. The bleaching can be implemented without
chlorine or with chlorine-containing chemicals, such as e.g.
hypochlorite. The pulp is generally produced from different woods
(deciduous and coniferous woods). Other fibrous materials, such as
e.g. CTMP (Chemical Thermo Mechanical Pulp--chemical-mechanical
wood material), can likewise be used. The fibrous materials can be
used individually or mixed. If a multilayer material inlet is used,
generally different fibrous material is used in all the different
layers. Hence in the different legs of the constant part, different
units can be used.
[0034] The fibrous material has both an influence on the units used
in the constant part of the tissue machine and on the metering
point for the chemicals which are used. Dependent upon the type of
fibre e.g. more or fewer cleaning units must be used (thick
material cleaner, cleaner, pressure sorter etc.). Also refiners are
used differently according to the type of fibre.
[0035] The tissue production is assisted, improved or controlled by
the use of chemicals. Normally a difference is thereby made between
process chemicals, functional chemicals, coating chemicals for the
yankee cylinder and chemicals for cleaning.
[0036] Process chemicals are inter alia pH regulators, defoamers,
retention and flocculation aids for improving the fibre retention
during the sheet formation or for coagulating fibres in a disc
filter or a microflotation, disruptive material fixers for binding
undesired particles in the system and also biocides for attacking
bacteria and for avoiding the formation of slime.
[0037] Functional chemicals serve inter alia as wet strength agents
for increasing the strength of the wet tissue paper, as dry
strength agents for increasing the strength of the dry tissue
paper, as so-called softener/debonders for improving the surface
softness and for reducing the stiffness of the tissue paper and
also as colourants and optical brighteners for increasing the
degree of whiteness.
[0038] Coating chemicals for the yankee cylinder are used inter
alia for controlling the adhesion of the tissue paper on the yankee
cylinder, the number of chemicals used being able to vary normally
between one and for instance five.
[0039] Suitable chemicals for cleaning are inter alia organic and
inorganic acids and caustic sodas. These are normally used for
cleaning the wires and felts in the tissue machine.
[0040] The location of use of chemicals of this type and hence also
the graft copolymers to be used according to the invention as wet
strength agents within the tissue machine can be very different.
Normally however the functional chemicals and hence also the
described graft copolymers are intended to be metered at a point at
which, directly after their metering, good mixing with the fibre
suspension is effected. Suitable points of the tissue machine are
therefore inter alia the rapid mixer, the material level box or
connection pipes directly in front of pumps. Further possible
addition locations are situated both in the wet part of the tissue
machine, at the end of the wire part, in front of or within the
press part and also in the dry part disposed after the press part.
Furthermore the possibility also exists of applying treatment
chemicals, such as e.g. wet strength agents, by spray application
onto the yankee cylinder. The addition of such treatment chemicals
can be effected also on the Pope roller with production of a
treatment agent film which is subsequently transferred to the
tissue web during the rolling process. Treatment chemicals can be
added, also within doubling machines or within processing machines,
onto the outer layers of the tissue paper or of the tissue
product.
[0041] The metering point is not only dependent upon the units
contained in the constant part but also upon the fibrous material
which is used, the process water quality (pH value, water hardness,
conductivity etc.) and also upon the use of different chemicals on
the same tissue machine. If for example wet strength agents are
used together with dry strength agents and/or softeners, it must be
ensured that both or all three chemicals can be absorbed onto the
fibre and the metering points must be chosen such that the
chemicals cannot react with each other before they are fixed on the
fibres.
[0042] Also the reaction time with the fibrous material can be of
different lengths. Hence the metering point can be nearer and
further removed from the material inlet according to the fibrous
material which is used.
[0043] If the chemicals which are used are sensitive to shear
stress, it must be ensured that no units are situated between the
metering point and the material inlet in which the chemical can
again be sheared off from the fibres.
[0044] The subject according to the application is intended to be
explained in more detail with reference to the subsequent examples
without restricting said subject to the examples shown here.
[0045] FIG. 1 shows the basis weight of the graft copolymers
produced according to the examples, in comparison with a wet
strength agent of the of the art.
[0046] FIG. 2 shows the breaking length in the dry state of the
graft copolymers according to examples 2 to 9 in comparison with a
wet strength agent of the state of the art.
[0047] FIG. 3 shows the breaking length in the wet state of the
graft copolymers according to examples 2 to 9 in comparison with a
wet strength agent of the state of the art.
[0048] FIG. 4 shows the relative wet moisture of the graft
copolymers according to examples 2 to 9 in comparison with a wet
strength agent of the state of the art.
EXAMPLE 1
Synthesis of Epoxy-Terminated methoxy-poly(ethyleneglycol)-glycidyl
ether (MPEG)
[0049] Polyethyleneglycol monomethyl ether (Fluka, 35 g; M=350
g/mol; 0.1 mol) was added to a mixture comprising epichlorohydrin
(Aldrich, 27.76 g; 0.3 mol; M=92.53 g/mol, b.p.: 115-117.degree.),
sodium hydroxide (3.2 g; 0.08 mol; M=40 g/mol) and water (0.5 ml)
and heated for 16 h at 60.degree. C. under an argon atmosphere.
Heating took place thereafter for 1.5 h at 90.degree. C.
[0050] The reaction mixture was dissolved in 150 ml chloroform and
mixed with 100 ml water. By adding sodium dihydrogen phosphate
(NaH.sub.2PO.sub.4), the aqueous phase was adjusted to a pH value
of 7. The precipitated solid material was filtered off and
discarded. After separating the aqueous phase, the organic phase
was washed twice with 50 ml water and subsequently dried with
sodium sulphate. Subsequently, the chloroform was distilled off in
the vacuum. Epichlorohydrin residue remaining in the product was
removed in the high vacuum at 10.sup.-2-10.sup.-3 mbar. In order to
check the complete removal of epichlorohydrin, a sample was heated
in the aqueous, basic medium then acidified with nitric acid and
mixed with silver nitrate. The test was negative (no precipitation
of silver chloride), which means the absence of halogen in the
product.
EXAMPLE 2
Synthesis of PEI-Graft-PEG
[0051] There was added to a solution of
methoxy-poly(ethyleneglycol)-glycidyl ether (from example 1) (12.0
g; 0.03 mol; Mw=400 g/mol) in 10 ml methanol a solution of
polyethyleneimine (Aldrich, Mw=40000 g/mol, 14.9 g, 0.0006 mol) in
30 ml methanol. The homogeneous mixture was agitated for 12 h under
reflux. Subsequently the reaction mixture was purified by means of
dialysis against water (dialysis hose ZelluTrans by Roth, MWCO
4000-6000 g/mol). The resulting graft copolymer was isolated by
freeze-drying.
EXAMPLE 3
Synthesis of PEI-Graft-PEG
[0052] There was added to a solution of
methoxy-poly(ethyleneglycol)-glycidyl ether (from example 1) (10.0
g; 0.025 mol; Mw=400 g/mol) in 10 ml methanol a solution of
polyethyleneimine (Aldrich, Mw=40000 g/mol, 20.0 g, 0.0005 mol) in
30 ml methanol. The homogeneous mixture was agitated for 12 h under
reflux. Subsequently the reaction mixture was purified by means of
dialysis against water (dialysis hose ZelluTrans by Roth, MWCO
4000-6000 g/mol). The resulting graft copolymer was isolated by
freeze-drying.
EXAMPLE 4
Synthesis of PEI-Graft-PEG (PEI-PEG 3)
[0053] There was added to a solution of
methoxy-poly(ethyleneglycol)-glycidyl ether (from example 1) (0.4
g; 0.001 mol; Mw=400 g/mol) in 10 ml methanol a solution of
polyethyleneimine (Aldrich, Mw=40000 g/mol, 8.0 g, 0.0002 mol) in
30 ml methanol. The homogeneous mixture was agitated for 12 h under
reflux. Subsequently the reaction mixture was purified by means of
dialysis against water (dialysis hose ZelluTrans by Roth, MWCO
4000-6000 g/mol). The resulting graft copolymer was isolated by
freeze-drying.
[0054] Yield: 74% of the theoretical
EXAMPLE 5
PEI-PEG 7
[0055] There was added to a solution of
methoxy-poly(ethyleneglycol)-glycidyl ether (from example 1) (0.88
g; 0.0022 mol; Mw=400 g/mol) in 10 ml methanol a solution of
polyethyleneimine (Aldrich, Mw=40000 g/mol, 8.0 g, 0.0002 mol) in
30 ml methanol. The homogeneous mixture was agitated for 12 h under
reflux. Subsequently the reaction mixture was purified by means of
dialysis against water (dialysis hose ZelluTrans by Roth, MWCO
4000-6000 g/mol). The resulting graft copolymer was isolated by
freeze-drying.
[0056] Yield: 90% of the theoretical
EXAMPLE 6
PEI-PEG 14
[0057] There was added to a solution of
methoxy-poly(ethyleneglycol)-glycidyl ether (from example 1) (1.76
g; 0.0044 mol; Mw=400 g/mol) in 10 ml methanol a solution of
polyethyleneimine (Aldrich, Mw=40000 g/mol, 8.0 g, 0.0002 mol) in
30 ml methanol. The homogeneous mixture was agitated for 12 h under
reflux. Subsequently the reaction mixture was purified by means of
dialysis against water (dialysis hose ZelluTrans by Roth, MWCO
4000-6000 g/mol). The resulting graft copolymer was isolated by
freeze-drying.
[0058] Yield: 82% of the theoretical
EXAMPLE 7
PEI-PEG 20
[0059] There was added to a solution of
methoxy-poly(ethyleneglycol)-glycidyl ether (from example 1) (6.00
g; 0.015 mol; Mw=400 g/mol) in 10 ml methanol a solution of
polyethyleneimine (Aldrich, Mw=40000 g/mol, 20.0 g, 0.0005 mol) in
30 ml methanol. The homogeneous mixture was agitated for 12 h under
reflux. Subsequently the reaction mixture was purified by means of
dialysis against water (dialysis hose ZelluTrans by Roth, MWCO
4000-6000 g/mol). The resulting graft copolymer was isolated by
freeze-drying.
[0060] Yield: 75% of the theoretical
EXAMPLE 8
PEI-PEG High Molecular
[0061] There was added to a solution of
methoxy-poly(ethyleneglycol)-glycidyl ether (from example 1) (4.8
g; 0.012 mol; Mw=400 g/mol) in 10 ml of an aqueous 0.1 M NaCl
solution, a solution of high-molecular polyethyleneimine (Fluka,
Mw=800000 g/mol, 16.0 g of a 50% aqueous solution,
1.times.10.sup.-5 mol) in 30 ml of a 0.1 M aqueous NaCl solution.
The homogeneous mixture was agitated for 12 h under reflux.
Subsequently the reaction mixture was purified by dialysis against
water (dialysis hose ZelluTrans by Roth, MWCO 4000-6000 g/mol). The
resulting graft copolymer was isolated by freeze-drying.
[0062] Yield: 59% of the theoretical
EXAMPLE 9
Production of a Graft Copolymer Via Peptide Coupling of a PEG
Carboxylic Acid with PEI (PEG-COOH-g-PEI)
[0063] In a 100 ml three-neck flask, 0.72 g PEG600-di-acid (Fluka,
M=600 g/mol; 1.210-3 mol) and 575.1 mg
N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride
(Merck, 310-3 mol) were dissolved in 10 ml distilled water.
Subsequently the solution was mixed with 345.3 mg
N-hydroxysuccinimide (Fluka, 310-3 mol). After 10 minutes, 4.0 g
polyethyleneimine (Aldrich, MW=40000 g/mol; 110-4 mol) in 20 ml
H.sub.2O were added and agitated for 12 h at 20.degree. C.
Subsequently the reaction mixture was purified by dialysis against
water (dialysis hose ZelluTrans by Roth, MWCO 4000-6000 g/mol). The
resulting graft copolymer was isolated by freeze-drying
[0064] Yield: 55% of the theoretical
EXAMPLE 10
Sheet Formation Test with the Graft Copolymers Produced in A
[0065] The laboratory sheet formation was effected according to the
rapid Kothen method. The production of the laboratory sheets was
effected according to DIN EN ISO 5269-2: 1998. The rapid Kothen
laboratory sheet former comprises a sheet forming device, the
transition elements and a plurality of vacuum dryers. In principle
a circular laboratory sheet is formed from a fibre suspension on a
wire cloth by suction effect. The sheet is subsequently dried under
defined conditions.
[0066] The basis weight of the formed sheet is 75.+-.2 g/m.sup.2
otro (oven dried), i.e. one sheet has a mass of 2.36 g.+-.0.06
g.
[0067] The pulp used for the tests was non-predried spruce sulphite
pulp (Pulp Factory Mannheim) with a degree of beating of 15 SR.
[0068] A pulp suspension with a material density of 0.236% was used
to produce the laboratory sheets. The chemicals to be tested were
added in a 2.5% solution to a litre of the pulp stock until
concentrations of 3.6 and 9 kg/t were set. The reaction time with
constant agitation was always 2 min, thereafter the laboratory
sheet formation was effected according to the mentioned method. For
the test, the laboratory sheets were conditioned to normal
conditions (23.degree. C., 50% relative humidity) (DIN EN 20187
1993).
[0069] The strength (breaking force) of paper is the force measured
during the test at the moment of breakage of the sample. In order
to minimise the variations in the basis weight, the breaking length
is determined from the breaking force according to the following
formula: breaking length=10.sup.6.times.breaking force/(basis
weight.times.strip width.times.acceleration due to gravity)
[m].
[0070] The samples used had a width of 15 mm, the free gripped
length was 100 mm. The testing was effected following DIN EN ISO
1924-2 1994-04. Wet breaking loads were tested on papers which were
immersed in advance in distilled water for 30 s (DIN ISO 3781
1994-10).
[0071] In order to determine the relative wet strength, the ratio
of the breaking length in the moist state to the dry breaking
length was formed:
Relative wet strength=breaking force (wet)/breaking force
(dry).times.100(%)
[0072] The results of the chemicals produced according to examples
2 to 9 were tested in comparison with a standard wet strength agent
(PAAE) on the laboratory sheet and are presented in FIGS. 1 to 4
and in Table 1.
TABLE-US-00001 TABLE 1 Breaking Breaking Relative Metering Basis
length length wet quantity weight dry wet strength (kg/t)
(g/m.sup.2) (m) (m) (%) PAAE 3 78.0 5012 635 12.7 6 79.0 5304 955
18.0 9 78.0 5456 1088 19.9 Example 3 77.1 4832 167 3.4 2 6 77.1
5194 508 9.8 9 76.8 5130 626 12.2 Example 3 75.5 5082 213 4.2 3 6
77.1 5137 509 9.9 9 77.1 5075 661 13.0 Example 3 76.1 5272 270 5.1
4 6 75.8 5122 627 12.2 9 75.2 5274 789 15.0 Example 3 75.5 5040 339
6.7 5 6 72.9 5142 686 13.3 9 74.8 5366 731 13.6 Example 3 74.8 5274
327 6.2 6 6 74.5 5164 631 12.2 9 77.4 5409 753 13.9 Example 3 77.1
5024 281 5.6 7 6 75.5 5283 599 11.3 9 76.4 4996 643 12.9 Example 3
75.2 4990 347 7.0 8 6 75.8 5332 655 12.3 9 75.8 5463 805 14.7
Example 3 75.2 5444 484 8.9 9 6 74.5 5762 800 13.9 9 75.2 5588 1027
18.4
* * * * *