U.S. patent application number 10/479515 was filed with the patent office on 2004-08-05 for wet-strength finishing agents for paper.
Invention is credited to Bottcher, Claus, Frenzel, Stefan, Kruger, Ellen, Wendker, Martin.
Application Number | 20040149411 10/479515 |
Document ID | / |
Family ID | 7687616 |
Filed Date | 2004-08-05 |
United States Patent
Application |
20040149411 |
Kind Code |
A1 |
Kruger, Ellen ; et
al. |
August 5, 2004 |
Wet-strength finishing agents for paper
Abstract
They are mixtures of (a) from 1 to 99.9% by weight of a
water-soluble epihalohydrin-crosslinked polyamidoamine and (b) from
0.1 to 20% by weight of at least one other cationic polymer.
Inventors: |
Kruger, Ellen; (Otterstadt,
DE) ; Wendker, Martin; (Worms, DE) ; Frenzel,
Stefan; (Mannheim, DE) ; Bottcher, Claus;
(Lambsheim, DE) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Family ID: |
7687616 |
Appl. No.: |
10/479515 |
Filed: |
December 10, 2003 |
PCT Filed: |
May 29, 2002 |
PCT NO: |
PCT/EP02/05900 |
Current U.S.
Class: |
162/164.1 ;
162/164.3; 162/168.2 |
Current CPC
Class: |
D21H 21/20 20130101;
D21H 17/54 20130101; D21H 17/72 20130101; D21H 17/56 20130101 |
Class at
Publication: |
162/164.1 ;
162/164.3; 162/168.2 |
International
Class: |
D21H 021/20; D21H
017/72; D21H 023/04; D21H 023/76; D21H 017/55 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 11, 2001 |
DE |
101 27 829.2 |
Claims
We claim:
1. Wet strength enhancers for paper, comprising mixtures of (a)
from 1 to 99.9% by weight of an epihalohydrin-crosslinked
polyamidoamine and (b) from 0.1 to 20% by weight of at least one
other cationic polymer from the group consisting of addition
polymers containing vinylamine units, dicyandiamide-formaldehyde
condensates.
2. Wet strength enhancers as claimed in claim 1, comprising (a) an
epihalohydrin-crosslinked polyamidoamine and (b) a 1-100 mol %
hydrolyzed polyvinylformamide.
3. A process for producing paper by draining a paper stock in the
presence of a wet strength enhancer, which comprises using wet
strength enhancers comprising mixtures of (a) from 1 to 99.9% by
weight of an epihalohydrin-crosslinked polyamidoamine and (b) from
0.1 to 20% by weight of at least one other cationic polymer from
the group consisting of addition polymers containing vinylamine
units and dicyandiamide-formaldehyde condensates.
4. A process as claimed in claim 3, wherein the paper stock is
admitted with (a) an epihalohydrin-crosslinked polyamidoamine and
(b) at least one other cationic polymer concurrently or in any
order, said components (a) and (b) being used in any event in a
weight ratio of from 1 to 99.9:0.1 to 20.
5. The use of the wet strength enhancers of either of claims 1 and
2 in the production of paper by addition to the paper stock before
sheet formation in amounts from 0.1 to 4% by weight, based on dry
fiber.
Description
DESCRIPTION
[0001] The present invention relates to wet strength enhancers for
paper and to a process for producing wet-strengthened enhanced
paper. U.S. Pat. No. 2,926,154 discloses water-soluble reaction
products of an epihalohydrin and polyamidoamines. The reaction
products are used in papermaking by adding them to the paper stock
as wet strength agents.
[0002] WO-A-98/32798 discloses a polymer combination prepared by
crosslinking a polymer mixture of a polyamidoamine and a vinylamine
polymer with an epihalohydrin. These reaction products are added to
the paper stock in a papermaking process to add dry and wet
strength to the paper.
[0003] U.S. Pat. No. 4,880,497 discloses copolymers which contain
vinylamine units and which are formed by hydrolysis of copolymers
of N-vinylformamide and other ethylenically unsaturated monomers.
The copolymers containing vinylamine units are added to the paper
stock in the papermaking process to enhance the dry and wet
strength of paper.
[0004] The reaction products of the reaction of epihalohydrins with
amino-containing compounds have the disadvantage of containing
major amounts of chlorinous by-products.
[0005] It is an object of the present invention to provide improved
wet strength enhancers for paper.
[0006] We have found that this object is achieved according to the
invention by wet strength enhancers for paper, comprising mixtures
of
[0007] (a) from 1 to 99.9% by weight of a water-soluble
epihalohydrin-crosslinked polyamidoamine and
[0008] (b) from 0.1 to 20% by weight of at least one other cationic
polymer from the group consisting of
[0009] addition polymers containing vinylamine units,
[0010] dicyandiamide-formaldehyde condensates.
[0011] Particular preference is given to wet strength enhancers
comprising
[0012] (a) a water-soluble epichlorohydrin-crosslinked
polyamidoamine and
[0013] (b) a 1-100 mol % hydrolyzed polyvinylformamide.
[0014] The invention also provides a process for producing paper by
draining a paper stock in the presence of a wet strength enhancer,
which comprises using wet strength enhancers comprising mixtures
of
[0015] (a) from 1 to 99.9% by weight of a water-soluble
epihalohydrin-crosslinked polyamidoamine and
[0016] (b) from 0.1 to 20% by weight of at least one other cationic
polymer from the group consisting of
[0017] addition polymers containing vinylamine units and
[0018] dicyandiamide-formaldehyde condensates.
[0019] In this papermaking process the paper stock is admixed with
(a) an epihalohydrin-crosslinked polyamidoamine and (b) at least
one other cationic polymer concurrently or in any order, said
components (a) and (b) being used in any event in a weight ratio of
from 1 to 99.9:0.1 to 20.
[0020] The invention further provides for the use of the
above-described wet strength enhancers in the making of paper by
addition to the paper stock before sheet formation in amounts of
from 0.1 to 4% by weight, based on dry fiber.
[0021] Component (a) of the paper wet strength enhancers according
to the invention may be a water-soluble epihalohydrin-crosslinked
polyamidoamine. Polyamidoamines may be prepared by condensation of
dicarboxylic acids with polyalkylenepolyamines, cf. U.S. Pat. No.
2,926,154 and WO-A-98/32798. For example, from 0.8 to 1.4 mol of a
polyalkylenepolyamine is used per mole of dicarboxylic acid.
[0022] Polyamidoamines are preferably prepared using aliphatic
dicarboxylic acids having 2 to 10 carbon atoms, for example oxalic
acid, malonic acid, succinic acid, maleic acid, glutaric acid,
adipic acid, azelaic acid and lauric acid. Preferred dicarboxylic
acids are adipic acid and glutaric acid.
[0023] Examples of polyalkylenepolyamines are diethylenetriamine,
tripropylenetetramine, tetraethylenepentamine,
methyl-bis-(3-aminopropyl)- amine, diaminopropylethylenediamine,
bisaminopropylethylenediamine and aminopropylethylenediamine.
[0024] The condensation of dicarboxylic acids with
polyalkylenepolyamines is effected at elevated temperature, for
example at from 110 to 220.degree. C. The water formed in the
course of the condensation is distilled out of the reaction
mixture. The condensation may also be effected in the presence of
lactones or lactones of carboxylic acids having 4 to 8 carbon
atoms. The reaction with epihalohydrins, preferably
epichlorohydrin, is effected in aqueous solution at for example
from 20 to 100.degree. C., preferably from 30 to 80.degree. C. The
reaction of polyamidoamines with epihalohydrins is carried on only
to that point at which the resultant reaction products remain
dissolved in water. Once the viscosity of the reaction solution has
attained the desired value, the reaction is terminated by addition
of an acid, for example acetic acid or formic acid. This provides
aqueous solutions of an epichlorohydrin-crosslinked polyamidoamine
having a viscosity of for example from 50 to 2000 mPas, preferably
from 60 to 400 mPas (determined in a Brookfield viscometer at
20.degree. C., spindle 2, 20 revolutions per minute, concentration
of the aqueous polymer solution: 12.5% by weight).
[0025] Useful cationic polymers may be derived for example from
synthetic and natural cationic polymers. Useful natural polymers
include for example cationic polysaccharides, cationic starch,
cationic amylose and derivatives thereof, cationic amylopectin and
derivatives thereof and also cationic guar derivatives.
[0026] Synthetic cationic polymers include for example
polyethyleneimines. They may be prepared by polymerizing
ethyleneimine in aqueous solution in the presence of acid-detaching
compounds, acids or Lewis acids. Polyethyleneimines are
commercially available and their molar masses range for example
from 200 to 2 000 000, preferably from 200 to 1 000 000. The
process of the invention particularly preferably utilizes
polyethylenimines having molar masses from 500 to 800 000.
[0027] A further class of synthetic cationic compounds is that of
the addition polymers containing vinylamine units. They may be
prepared from open-chain N-vinylcarboxamides of the formula 1
[0028] where R.sup.1 and R.sup.2 are identical or different and are
each selected from the group consisting of hydrogen and
C.sub.1-C.sub.6-alkyl. Useful monomers include for example
N-vinylformamide (R.sup.1.dbd.R.sup.2.dbd.H in formula I),
N-vinyl-N-methylformamide, N-vinylacetamide,
N-vinyl-N-methylacetamide, N-vinyl-N-ethylacetamide,
N-vinyl-N-methylpropionamide and N-vinylpropionamide. The polymers
may be prepared by polymerizing the monomers mentioned alone, mixed
with each other or together with other monoethylenically
unsaturated monomers. The addition polymers in question are
preferably homo- or copolymers of N-vinylformamide.
[0029] Useful monoethylenically unsaturated monomers for
copolymerization with N-vinylcarboxamides include all compounds
copolymerizable therewith. Examples thereof are vinyl esters of
saturated carboxylic acids of 1 to 6 carbon atoms such as vinyl
formate, vinyl acetate, vinyl propionate and vinyl butyrate. Useful
comonomers further include ethylenically unsaturated
C.sub.3-C.sub.6-carboxylic acids, for example acrylic acid,
methacrylic acid, maleic acid, crotonic acid, itaconic acid and
vinyl ester acid and also their alkali metal and alkaline earth
metal salts, esters, amides and nitriles of the carboxylic acids
mentioned, for example methyl acrylate, methyl methacrylate, ethyl
acrylate and ethyl methacrylate. Further useful carboxylic esters
are derived from glycols or polyalkylene glycols where in each case
only one OH group is esterified, for example hydroxyethyl acrylate,
hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxybutyl
acrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate and
also monoacrylate esters of polyalkylene glycols having a molar
mass of from 500 to 10 000. Useful comonomers further include
esters of ethylenically unsaturated carboxylic acids with
aminoalcohols, for example dimethylaminoethyl acrylate,
dimethylaminoethyl methacrylate, diethylaminoethyl acrylate,
diethylaminoethyl methacrylate, dimethylaminopropyl acrylate,
dimethylaminopropyl methacrylate, diethylaminopropyl acrylate,
dimethylaminobutyl acrylate and diethylaminobutyl acrylate. Basic
acrylates can be used in the form of the free bases, salts with
mineral acids such as hydrochloric acid, sulfuric acid or nitric
acid, the salts with organic acids such as formic acid, acetic
acid, propionic acid or of sulfonic acids or in quaternized form.
Useful quaternizing agents include for example dimethyl sulfate,
diethyl sulfate, methyl chloride, ethyl chloride or benzyl
chloride.
[0030] Useful comonomers for the monomers of the formula I further
include amides of ethylenically unsaturated carboxylic acids such
as acrylamide, methacrylamide and also N-alkylmonoamides and
diamides of monoethylenically unsaturated carboxylic acids with
alkyl radicals of from 1 to 6 carbon atoms, for example
N-methylacrylamide, N,N-dimethylacrylamide, N-methylmethacrylamide,
N-ethylacrylamide and N-propylacrylamide and tert-butylacrylamide
and also basic (meth)acrylamides, for example
dimethylaminoethylacrylamide, dimethylaminoethylmethacrylamide,
diethylaminoethylacrylamide, diethylaminoethylmethacrylamide,
dimethylaminopropylacrylamide, diethylaminopropylacrylamide,
dimethylaminopropylmethacrylamide and
diethylaminopropylmethacrylamide.
[0031] Useful comonomers for the monomers of the formula I further
include N-vinylpyrrolidone, N-vinylcaprolactam, acrylonitrile,
methacrylonitrile, N-vinylimidazole and also substituted
N-vinylimidazoles, for example N-vinyl-2-methylimidazole,
N-vinyl-4-methylimidazole, N-vinyl-5-methylimidazole,
N-vinyl-2-ethylimidazole and N-vinylimidazolines such as
N-vinylimidazoline, N-vinyl-2-methylimidazoli- ne and
N-vinyl-2-ethylimidazoline. N-Vinylimidazoles and
N-vinylimidazolines are used not only in the form of the free bases
but also after neutralization with mineral acids or organic acids
or after quaternization, a quaternization being preferably effected
with dimethyl sulfate, diethyl sulfate, methyl chloride or benzyl
chloride. Also useful are diallyldialkylammonium halides, for
example diallyldimethylammonium chlorides.
[0032] Useful comonomers for N-vinylcarboxamides further include
sulfo-containing monomers, for example vinylsulfonic acid,
allylsulfonic acid, methallylsulfonic acid, styrenesulfonic acid,
the alkali metal or ammonium salts of these acids or 3-sulfopropyl
acrylate.
[0033] The copolymers contain for example
[0034] from 99.99 to 1 mol % of N-vinylcarboxamides of the formula
I and
[0035] from 1 to 99 mol % of other monoethylenically unsaturated
monomers copolymerizable therewith
[0036] in copolymerized form.
[0037] To prepare vinylamine polymers it is preferable to start
from homopolymers of N-vinylformamide or from copolymers obtainable
by copolymerization of
[0038] N-vinylformamide with
[0039] vinyl formate, vinyl acetate, vinyl propionate,
acrylonitrile or N-vinylpyrrolidone
[0040] and subsequent hydrolysis of the homo- or copolymers to form
vinylamine units from the copolymerized N-vinylformamide units, the
degree of hydrolysis being for example in the range from 1 to 100
mol %. For instance, polyvinylamine is obtained by complete
hydrolysis (degree of hydrolysis 100 mol %) of homopolymers of
N-vinylformamide.
[0041] The hydrolysis of the above-described polymers is effected
according to known processes by the action of acids, bases or
enzymes. This converts the copolymerized monomers of the
above-indicated formula I through detachment of the group 2
[0042] where R.sup.2 is as defined for formula I, into polymers
which contain vinylamine units of the formula 3
[0043] where R.sup.1 is as defined for formula I.
[0044] The homopolymers of the N-vinylcarboxamides of the formula I
and their copolymers may be hydrolyzed to an extent in the range
from 1 to 100 mol %, advantageously to an extent in the range from
5 to 100 mol %, preferably to an extent in the range from 10 to 100
mol %. In most cases, the degree of hydrolysis of the homo- and
copolymers is in the range from 20 to 95 mol %. The degree of
hydrolysis of the homopolymers is synonymous with the vinylamine
units content of the polymers. In the case of copolymers containing
units derived from vinyl esters, the hydrolysis of the
N-vinylformamide units can be accompanied by a hydrolysis of the
ester groups with the formation of vinyl alcohol units. This is the
case especially when the hydrolysis of the copolymers is carried
out in the presence of aqueous sodium hydroxide solution.
Copolymerized acrylonitrile is likewise chemically modified in the
hydrolysis, for example converted into amide groups or carboxyl
groups. The homo- and copolymers containing vinylamine units may
optionally contain up to 20 mol % of amidine units, formed for
example by intramolecular reaction of an amino group with an
adjacent amide group, for example of copolymerized
N-vinylformamide.
[0045] Polymers containing vinylamine units also include hydrolyzed
graft polymers of N-vinylformamide on polysaccharides, polyalkylene
glycols and polyvinyl acetate. The N-vinylformamide units grafted
onto the polymers are converted into the corresponding addition
polymers containing vinylamine units by hydrolysis to detach formyl
groups. Graft polymers containing vinylamine units are described
for example in U.S. Pat. No. 5,334,287, U.S. Pat. No. 6,048,945 and
U.S. Pat. No. 6,060,566.
[0046] In an embodiment of the present invention, the cationic
polymers are used in the form of salt-free aqueous solutions or
low-salt aqueous solutions containing not more than 5% by weight
and preferably not more than 2% by weight of an inorganic salt.
Such salt-free or low-salt solutions may be prepared by
ultrafiltration or by precipitation of the neutral salts with
organic solvents such as acetone, methyl ethyl ketone or
alcohols.
[0047] Preferred cationic polymers are
[0048] addition polymers containing vinylamine units.
[0049] The molar mass M.sub.w of the cationic polymers is not less
than 15 000 and is preferably in the range from 50 000 to 10
million. The molar mass M.sub.w of the cationic polymers is
determined by light scattering. The cationic polymers may have a
charge density of at least 1.5 and preferably from 4 to 15 meq/g
(measured at pH 7).
[0050] Useful fibers for producing the pulps include all types
customary for this purpose, for example mechanical pulp, bleached
and unbleached chemical pulp and paper stocks from all annual
plants. Mechanical pulp includes for example groundwood pulp,
thermomechanical pulp (TMP), chemothermomechanical pulp (CTMP),
pressure groundwood, semichemical pulp, high yield chemical pulp
and refiner mechanical pulp (RMP). Useful chemical pulps include
for example sulfate, sulfite and soda pulps. Preference is given to
using unbleached chemical pulps, which is also known as unbleached
kraft pulp. Useful annual plants for producing paper stocks include
for example rice, wheat, sugarcane and kenaf. Pulps are also
produced using waste paper alone or mixed with other fibers. Waste
paper also includes coated waste, which, owing to its binder
content for coating and printing ink compositions, gives rise to
white pitch. Stickies are due to the adhesives from sticky labels
and letter envelopes, due to adhesive materials from spine gluing
and due to hotmelts. The fibers mentioned may be used alone or
mixed with each other.
[0051] The inventive wet strength enhancers comprised of components
(a) and (b) contain for example from 0.1 to 20% and preferably from
0.2 to 5% by weight of a cationic natural and/or synthetic polymer.
The wet strength enhancers are added to the paper stock in the
papermaking process in amounts from 0.1 to 5% by weight, preferably
from 0.5 to 4% by weight, each percentage being based on dry fiber.
However, components (a) and (b) can also be added separately to the
paper stock in the papermaking process, in the above-described
ratio. It is possible, for instance, first to add component (a) to
the paper stock and then to add component (b) just ahead of the
headbox for example. However, the order of the components can also
be reversed and similarly the two components can also be added
concurrently through a two-material nozzle or through two
separately disposed metering positions, to the paper stock.
[0052] Whereas the wet strength of paper cannot be increased to
beyond a certain value by raising the amount of a customary wet
strength agent, for example an epichlorohydrin-crosslinked
polyamidoamine as per component (a), which is added to the paper
stock, the wet strength enhancer of the invention provides a
further increase in the wet strength of the paper.
[0053] The percentages in the examples are by weight. The wet
breaking length was determined according to DIN ISO 3781 following
a 15 minute immersion in water.
EXAMPLES
[0054] The stock model used was a 3.3 g/l consistency pulp of 100%
bleached pine sulfate beaten to 32.degree. SR and having a pH of
7.1. Samples of this pulp were each admixed with the wet strength
agents reported in Table 1 and the mixture obtained in each case
was drained on a Rapid-Kothen sheet former. The basis weight of the
sheets of paper was 55 g/m.sup.2 in each case. The sheets were
stored at 110.degree. C. for 5 minutes. The wet tensile strength of
the sheets was then determined by the method indicated above. The
materials used and the results obtained therewith are reported in
the table.
[0055] Wet strength agent 1: commercially available water-soluble
epichlorohydrin-crosslinked polyamidoamine (Luresin.RTM. KNU),
polymer concentration 13.5% by weight
[0056] Wet strength agent 2: commercially available water-soluble
epichlorohydrin-crosslinked polyamidoamine (Kymene.RTM. G 3),
polymer concentration 16% by weight
[0057] PVAm: aqueous solution of polyvinylamine having a molar mass
Mw of 400 000 g/mol, polymer concentration 11.8% by weight
[0058] Wet breaking length [m] on use of wet strength agent 1, 2 or
PVAm
1 Wet Wet Addition to strength strength paper stock agent 1 agent 2
PVAm Comparison 1 2% of CP.sup.1) 912 m 872 m 480 m Comparison 2 5%
of CP 1550 m 1492 m 1328 m Comparison 3 10% of CP 2165 m 1935 m
1459 m Example 1 5% of CP + 2% 2161 m 2094 m -- of PVAm Example 2
5% of CP + 2% 2030 m 1972 m -- of PVAm .sup.1)CP = commercial
product
* * * * *