Note: Descriptions are shown in the official language in which they were submitted.
CA 02525626 2005-11-14
PACKAGING MATERIAL CONSISTING OF AN AT LEAST DOUBLE-
LAYERED COMPOSITE MATERIAL FOR PRODUCING
CONTAINERS FOR PACKING LIQUIDS
Description
The present invention relates to a packaging material comprising an at least
two-layer
laminate of sized paper or sized cardboard and at least one water-impermeable
film or
foil for packaging liquids, and to the use of paper products which have been
engine
sized and which have been laminated on one or both sides with a plastics film
or metal
foil, for producing containers for packaging liquids, in particular beverages.
EP-B-0 292 975 discloses the use of an emulsion of an alkylketene dimer in
combination with a cationic rosin size and an agent imparting insolubility,
such as alum,
for producing cardboard for packaging liquids. The cardboard is produced by
adding
size and alum to an aqueous slurry of cellulose fibers and draining the paper
stock on a
wire.
EP-A-1 091 043 discloses a process for producing a coated packaging cardboard,
an
aqueous slurry of cellulose fibers being engine sized with an aqueous
dispersion of a
rosin size, a synthetic size, such as alkylketene dimer, and at least one
aluminum
compound and the aqueous slurry being drained on a wire. The aqueous
dispersions of
engine sizes can, if appropriate, comprise a dispersant, e.g. cationic starch,
casein,
cellulose derivatives, polyvinyl alcohols, polyacrylamides or
polyethylenimines. The
cardboard is usually coated after the sizing.
Paper products laminated ~on both sides with a liquid-impermeable layer and
intended
for packaging foods are disclosed in WO-A-02!090206. The paper products are
engine
sized with aqueous dispersions of alkylketene dimers. The amount of
alkylketene
dimers is at least 0.25, preferably 0.25 - 0.4, % by weight, based on the
weight of the
dry paper products.
Further multilayer packaging materials whose base layer consists of paper or
cardboard are described, for example, in WO-A-97102140, WO-A-97/02181 and
WO-A-98/18680.
The prior art also discloses the use of size mixtures comprising aqueous
dispersions of
alkylketene dimers and polymer sizes for the engine sizing of paper and
cardboard, cf.
DE-A-32 35 529, WO-A=94/05855 and WO-A-96/31650.
Tha prior German application 10237913.0 discloses a process for producing
cardboard
for packaging liquids. In thi s process, the cardboard is produced by engine
sizing of an
PF 54531
CA 02525626 2005-11-14
2
aqueous slurry of cellulose fibers with at least one engine size in the
presence of at
least one retention aid and at least one cationic polymer and, if appropriate,
a water-
soluble aluminum compound and drainage of the paper stock on a wire. Sizes
described are alkylketene dimers, alkyl- and alkenylsuccinic anhydrides, alkyl
isocyanates, combinations of rosin size and alum and combinations of reaction
products of rosin size with carboxylic anhydrides and alum.
It is an object of the present invention to provide further packaging
materials based on
paper products, where the packagings should have in particular improved edge
penetration and improved adhesion of the laminates to paper or cardboard.
We have found that this object is achieved, according to the invention, by a
packaging
material comprising an at least two-layer laminate of a sized paper or sized
cardboard
and at least one water-impermeable film or foil for producing containers for
packaging
liquids, if the paper or the cardboard is in each case engine sized with a
polymer size.
The present invention also relates to the use of paper products which are
obtainable in
each case by
engine sizing of a paper stock comprising an aqueous slurry of cellulose
fibers with at
least one polymer size as an engine size or with a polymer size and an aqueous
dispersion of an alkylketene dimer or a mixture thereof in the presence of a
retention
aid and, if appropriate, of a water-soluble aluminum compound and, if
appropriate, at
least one cationic polymer,
drainage of the paper stock on the wire of a paper machine,
drying of the paper product and
lamination of the paper product on one or both sides with a plastics film or
metal foil,
for producing containers for packaging liquids, in particular beverages.
All cellulose fibers usually used in the paper industry, for example fibers of
wood pulp
and all annual plants, can be used for producing sized paper or sized
cardboard.
Mechanical pulp is understood as meaning, for example, groundwood,
thermomechanical pulp (TMP), chemothermomechanical pulp (CTMP), pressure
groundwood, semichemical pulp, high-yield pulp, refiner mechanical pulp (RMP)
and
wastepaper. Pulps which can be used in bleached or in unbleached form are also
suitable. Examples of these are sulfate, sulfite and soda pulps. Unbleached
pulps,
which are also referred to as unbleached kraft pulp, are preferably used. The
fibers
may be used alone or as a mixture with one another.
PF 54531 CA 02525626 2005-11-14
3
in the engine sizing of paper or cardboard, sizing is carried out during the
process for
the production of these materials, by adding an engine size to the paper stock
and
draining said paper stock on the wire of a paper machine with sheet formation.
According to the invention, the engine size used is a polymer size comprising
synthetic
polymers. The polymer sizes disclosed in JP-A-58/115 196 are aqueous polymer
dispersions which are a paper size and at the same time increase the strength
of
paper. These dispersions are prepared by polymerization of, for example,
styrene and
alkyl acrylates in the presence of starch and free radical polymerization
initiators in an
aqueous medium. The starch used in each case is digested or degraded before
the
polymerization, so that it is soluble in water. The polymers of these
dispersions are
graft polymers of styrene and alkyl acrylates on starch or modified starch.
Further polymer sizes are disclosed in EP-B-0 257 412 and EP-B-0 267 770. They
are
prepared by copolymerization of acrylonitrile andlor methacrylonitrile and at
least one
acrylate of a monohydric, saturated C3- to C8-alcohol by an emulsion
polymerization
method in an aqueous solution which comprises a degraded starch, in the
presence of
free radical initiators, preferably hydrogen peroxide or redox initiators. The
degraded
starches have viscosities n; of from 0.04 to 0.50 dl/g. Such starches are
obtained, for
example, in an oxidative, thermal, acidolytic or enzymatic degradation of a
natural or
cationically or anionically modified starch. Natural starches from potatoes,
wheat, corn,
rice or tapioca are advantageously used. An enzymatically degraded potato
starch is
preferred. The degraded starches act as emulsifiers in the copolymerization
_of, fnr
example, styrene and n-butyl acrylate in an aqueous medium. The aqueous
solution in
which the copolymerization is carried out comprises, for example, from 1 to
25% by
weight of at least one degraded starch. For example, from 10 to 150 preferably
from 40
to 100, parts by weight of the abovementioned monomers are polymerized in 100
parts
by weight of such a solution. Instead of acrylonitrile and/or
methacrylonitrile, it is also
possible to use styrene in the copolymerization, cf. WO-A-94/05855. Aqueous
dispersions of copolymers having a mean particle diameter of, for example,
from 50 to
500 nm, preferably from 100 to 300 nm, are obtained. These polymer dispersions
are
presumably graft polymers of the monomers used in each case tin degraded
starch.
Further polymer sizes based on copolymers of styrene.and C3- to C8-alkyl
(meth)acrylates are disclosed in WO 02!14393. They are prepared by
copofymerization
of said monomers in an aqueous medium in the presence of degraded starch and
free
radical polymerization initiators by a two-stage process.
Other suitable polymer sizes are those aqueous polymer dispersions which can
be
prepared in the presence of synthetic polymeric protective colloids. They are
obtainable, for example, by copolymerization of from 2 to 32 parts of a
mixture of
PF 54531
CA 02525626 2005-11-14
4
(a) styrene, acrylonitrile and/or methacrylonitrile,
(b) acrylates and/or methacryiates of C,- to C,8-alcohofs andlor vinyl esters
of
saturated C2- to C4-carboxylic acids and, if required,
(c) other monoethylenically unsaturated copolymerizable monomers
in aqueous solution in the presence of 1 part by weight of a solution
copolymer of
(1 ) di-C,- to C4-alkylamino-Cz- to C4-alkyl (meth)acrylates which, if
appropriate, may
be protonated or quaternized,
(2) nonionic, hydrophobic, ethylenically unsaturated monomers, in these
monomers,
if they are polymerized by themselves, form hydrophobic polymers, and, if
appropriate,
(3) monoethylenically unsaturated C3- to CS-carboxylic acids or their
anhydrides, the
molar ratio of (1) : (2) : (3) being 1 : 2.5 to 10 : 0 to 1.5, copolymerized.
First, a solution copolymer i ~ prepared by copolymerizing the monomers of
groups (1)
and (2) and, if appropriate, (3) in a water-miscible organic solvent. Suitable
solvents
are, for example, C,- to Ca-carboxylic acids, such as formic acid; acetic acid
and
propionic acid, or C,- to C4-alcohols, such as methanol, ethanol, n-propanol
or
isopropanol, and ketoses, such as acetone. Preferably used monomers of group
{1)
are dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate,
dimethylaminopropyl methacrylate and dimethylaminopropyl acrylate. The
monomers
of group (1) are preferably used in protonated or in quaternized form.
Suitable
quaternizing agents are, for example, methyl chloride, dimethyl sulfate and
benzyl
chloride.
Monomers of group (2) which are used are nonionic, hydrophobic, ethylenicafly
unsaturated compounds which, if they are polymerized by themselves, form
hydrophobic polymers. These include, for example, styrene, methylstyrene, C,-
to C,$-
alkyl esters of acrylic acid or methacrylic acid, for example methyl acrylate,
ethyl
acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, tert-butyl
acrylate and
isobutyl acrylate, and isobutyl rnethacrylate, n-butyl methacrylate and tert-
butyl
methacrylate. Acrylonitrile, methacrylonitrile, vinyl acetate, vinyl
propionate and vinyl
butyrate are also suitable. Mixtures of the monomers of group (2) can also be
used in
the copoiymerization, for example mixtures of styrene and isobutyl acrylate.
The
solution copolymers serving as an emulsifier can, if appropriate, also
comprise
PF 54531
CA 02525626 2005-11-14
monomers of group (3) incorporated in the form of polymerized units, for
example
monoethylenically unsaturated C3- to CS-carboxylic acids or their anhydrides,
e.g.
acrylic acid, methacrylic acid, itaconic acid, malefic acid, malefic anhydride
or itaconic
anhydride. The molar ratio (1) : (2) : (3) is 1 : 2.5 to 10 : 0 to 1.5. The
copolymer
5 solutions thus obtained are diluted with water and serve in this form as a
protective
colloid for the polymerization of the abovementioned monomer mixtures of the
components (a) and (b) and, if appropriate, (c). Suitable monomers of group
(a) are
styrene, acrylonitrile, methacrylonitrile or mixtures of styrene and
acrylonitrile or of
styrene and methacrylonitrile. Monomers of group (b) which are used are
acrylates
andlor methacrylates of C,- to C,8-alcohols andlor vinyl esters of saturated
C2- to C4-
carboxylic acids. This group of monomers corresponds to the monomers of group
(2)
which are described above. Preferably used monomers of group (b) are butyl
acrylate
and butyl methacrylate, e.g. isobutyl acrylate, n-butyl acrylate and isobutyl
methacrylate. Monomers of group (c) are, for example, monoethylenically
unsaturated
C3- to C5-carboxylic acids, acrylamidomethylpropanesulfonic acid, sodium
vinylsulfonate, vinylimidazole, N-vinylformamide, acrylamide, methacrylamide
and N-
vinylimidazoline. From 1 to 32 parts by weight of a monomer mixture of the
components (a) to (c) are usEd per part by weight of the copolymer. The
monomers of
the components (a) and (b) can be copolymerized in any desired ratio, e.g. in
a molar
ratio of from 0.1 : 1 to 1 : 0.1.
The monomers of group (c) are, if required, used for modifying the properties
of the
copolymers.
Sizes of this type are described, for example, in EP-B-0 051 144, EP-B-0 058
313 and
EP-B-0 150 003.
Preferably used polymer sizes are aqueous polymer dispersions which are
obtainable
by copolymerization of
from 20 to 65% by weight of styrene, acrylonitrile and/or methacrylonitrile,
from 80 to 35% by weight of acrylates and/or methacrylates of monohydric
saturated
C3- to Ce- alcohols and
from 0 to 20°I° by weight of other monoethylenically unsaturated
copolymerizable
monomers, such as acrylamide, methacrylamide, vinylformamide, acrylic acid,
methacrylic acid, malefic acid, itaconic acid, 2-acrylamido-2-
methylpropanesulfonic acid
or basic monomers, such as dimethylaminoethyl acrylate, dimethylaminoethyl
methacrylate, dimethylaminopropyl acrylate or dimethylaminopropyl
methacrylate, the
basic monomers generally being used in the form of hydrochlorides or in a form
quaternized with methyl chloride, dimethyl sulfate or benzyl chloride,
PF 54531
CA 02525626 2005-11-14
s
in the presence of free radical initiators by an emulsion polymerization
method in an
aqueous solution of a degraded starch as a protective colloid.
Other preferably used polymer sizes are aqueous polymer dispersions which are
obtainable by copolymerization of
from 60 to 90% by weight of styrene and/or methylstyrene,
from 10 to 40% by weight of 1,3-butadiene and/or isoprene and
from 0 to 20% by weight of other monoethylenically unsaturated copolymerizabfe
monomers, such as acrylic acid, methacrylic acid, itaconic acid, acrylamide,
methacrylamide or N-vinylpyrrolidone,
in the presence of free radical initiators by an emulsion polymerization
method in an
aqueous solution of a degraded starch as a protective colloid.
The polymer sizes are preferably cationic or anionic. The charge of the
aqueous
dispersions is based either can the type of comonomers incorporated in the
form of
polymerized units in the copolymers (for example, the polymer size dispersion
is
cationic when basic monomers are used, whereas they are anionic as a result of
incorporation of, for example, acrylic acid or its salts in the form of
polymerized units) or
on the charge of the protective colloid used in each case. For example, the
use of
catioriic . .starch as an emulsifier leads to cationic polymer sine
~lig~2rginng.
For the engine sizing of paper or cardboard, for example, from 0.1 to 2.0,
preferably
from 0.2 to 0.75, % by weight, based on dry paper product, of polymer size
(i.e. 100%
strength polymer) are used.
The engine sizing of paper and cardboard can additionally be carried out in
the
presence of aqueous dispersions of reactive sizes, such as alkylketene dimers,
C5- to
C22-alkyl- and/or CS- to C2z-alkenylsuccinic anhydrides, chloroformic esters
and C,2- to
C36-alkyl isocyanates, and in the presence of combinations of rosin size and
alum or of
combinations of reaction products of rosin size with carboxylic anhydrides and
alum.
Instead of alum or in combination with alum, it is possible to use other
aluminum-
comprising compounds, such as polyaluminum chlorides or the polyaluminum
compounds disclosed in EP-B-1 091 043.
Among the reactive sizes, C,2- to Cz2-alkylketene dimers, e.g.
stearyldiketene,
lauryldiketene, palmityldiketene, oleyldiketene, behenyldiketene or mixtures
thereof,
are preferably used.
PF 54531
CA 02525626 2005-11-14
7
Suitable succinic anhydrides are, for example, decenylsuccinic anhydride,
octenylsuccinic anhydride, dodecenylsuccinic anhydride and n-
hexadecenylsuccinic
anhydride.
The reactive sizes are usually used in the form of an aqueous dispersion. For
example,
alkylketene dimers are dispersed in an aqueous solution of a cationic starch,
or
nonionic or anionic emulsifiers are used for stabilizing the alkylketene
dimers. The
reactive size dispersions formed are cationically or anionically charged or
neutral,
depending on the type and amount of the emulsifiers, or mixtures of
emulsifiers
compatible with one another, which are used.
For example, anionic emulsifiers can be added to alkylketene dimer dispersions
which
were emulsified with the aid of cationic starch in water. If the charge of the
anionic
emulsifiers predominates over the charge of the cationic emulsifiers, an
anionically
charged alkyl diketone dimer dispersion is obtained. Anionically charged
aqueous
alkylketene dispersions are preferably prepared by emulsifying alkylketene
dimers in
aqueous solutions of anionic emulsifiers. For example, condensates of
naphthalenesulfonic acid and formaldehyde, suffonated polystyrene, C,°-
to
C22-alkylsulfuric acids, ligninsulfonic acid, phenolsulfonic acid,
naphthalenesulfonic acid
or the sodium, potassium or ammonium salts of said acids can be used as
anionic
emulsifiers. Copolymers of acrylic acid and malefic acid, homopolymers of
acrylic acid,
homopolymers of methacrylic acid, copolymers of isobutpne and malefic 2cid
andJor
acrylic acid, hydrolyzed copolymers of isobutene or diisobutene and malefic
anhydride
are also suitable emulsifiers for the preparation of anionic alkylketene dimer
dispersions. The acid groups of the homo- and copolymers can, for example, be
partly
or completely neutralized with sodium hydroxide solution, potassium hydroxide
solution
or ammonia and used in this form as anionic emulsifiers. The molar mass MW of
the
homopolymers and of the copolymers is, for example, from 1 000 to 15 000,
preferably
from 1 500 to 10 000. The emulsifiers are used, for example, in amounts of up
to 3.5,
preferably up to 2, % by weight, based on the reactive size to be dispersed.
The reactive sizes are alternatively used in the engine sizing of the paper
products to
be used according to the invention as substrate material for the packaging
materials.
They are used in particular when packaging materials having particularly good
edge
penetration are desired. They are then employed in amounts which are usually
required for the production of sized paper products, e.g, from 0.1 to 2.0,
preferably from
0.1 to 0.5, % by weight, based on dry cellulose fibers. For example, from 0 to
90,
preferably from 50 to 90, parts by weight of reactive sizes are used per 100
parts by
weight of polymer size. If mixtures of a polymer size dispersion and of an
aqueous
dispersion of a reactive size are used, the mixtures comprise, for example,
from 5 to
PF 54531 CA 02525626 2005-11-14
50, preferably from 10 to 30, % by weight, based in each case on the polymer
content,
of polymer (100% strength).
If reactive sizes are used together with a polymer size, the reactive sizes,
preferably
alkyfketene dimer dispersions, can first be added to the paper stock and then
the
polymer size dispersions can be metered. However, the alkylketene dimer
dispersion
and at least one polymer size dispersion can also be added simultaneously to
the
paper stock and the latter then drained with sheet formation, or a mixture of
a reactive
size, such as at least one alkylketene dimer dispersion, and at least one
polymer size
dispersion is added to the paper stock and the latter is then drained with
sheet
formation.
The polymer sizes can of course also be used as surface sizes by applying
them, for
example with the aid of a size press, to the surface of the paper or spraying
them onto
the surface of the paper.
The draining of the paper stack is additionally effected in the presence of a
retention
aid. Apart from anionic retention aids or nonionic retention aids, such as
polyacrylamides, cationic polymers are preferably used as retention aids and
as
drainage aids. A significant improvement in the runability of the paper
machines is
achieved thereby. Cationic retention aids which may be used are all products
commercially available for this purpose. These are, for example, cationic
polyacrylamides, polydiallyldimethylammonium chlorides, polyethylenimines,
polyamines having a molar mass of more than 50 000, polyamines which, if
appropriate, are modified by grafting-on of ethylenimine, polyetheramides,
polyvinylimidazoles, polyvinylpyrrolidines, polyvinylimidazolines,
polyvinyltetrahydropyridines, pofy(dialkylaminoalkyl vinyl ethers),
poly(diallkylaminoalkyl (meth)acrylates) in protonated or in quarternized
form, and
polyamidoamines obtained from a dicarboxylic acid, such as adipic acid, and
polyalkylenepolyamines, such as diethylenetriamine, which are grafted with
ethylenimine and crosslinked with polyethylene glycol dichlorohydrin ethers
according
to DE-B-24 34 816, or polyamidoamines which have been reacted with
epichlorohydrin to give water-soluble condensates, and copolymers of
acrylamide or
methacrylamide and dialkylaminoethyl acryfates or methacryfates, for example
copolymers of acrylamide and dimethylaminoethyl acrylate in the form of the
salt with
hydrochloric acid or in a form quaternized with methyl chloride. Further
suitable
retention aids are microparticle systems comprising cationic polymers, such as
cationic
starch and finely divided silica, or comprising cationic polymers, such as
cationic
polyacrylamide, and bentonite.
PF 54531
CA 02525626 2005-11-14
9
The cationic polymers which are used as retention aids have, for example,
Fikentscher
K values of at least 140 (determined in 5% strength aqueous sodium chloride
solution
at a polymer concentration of 0.5% by weight, a temperature of 25°C and
a pH of 7).
They are preferably used in amounts of from 0.01 to 0.3% by weight, based on
dry
cellulose fibers.
If appropriate, at least one cationic polymer may also be added to the aqueous
slurry of
cellulose fibers, in addition to the abovementioned substances. Examples of
cationic
polymers are polymers comprising vinylamine units, polymers comprising
vinylguanidine units, polymers comprising dialkylaminoalkyl(meth)acrylamide
units,
polyethylenimines, polyamidoamines grafted with ethylenimine andlor
polydiallyldimethylammonium chlorides. The amount of cationic polymers is, for
example, from 0.001 to 2.0, preferably from 0.01 to 0.1, % by weight, based on
dry
cellulose fibers.
Polymers comprising vinylamine units are known, cf. US-A-4,421,602, US-A-
5,334,287,
EP-A-0 216 387, US-A-5,981,689, WO-A-00/63295 and US-A-6,121,409. They are
prepared by hydrolysis of open-chain polymers comprising N-vinylcarboxamide
units.
These polymers are obtainable, for example, by polymerization of N-
vinylformamide, N-
vinyl-N-methylformamide, N-vinylacetamide, N-vinyl-N-methylacetamide, N-vinyl-
N-
ethylacetamide and N-vinylpropionamide. Said monomers can be polymerized
either
alone or together with other monomers.
Suitable monoethylenically unsaturated monomers which are copolymerized with
the
N-vinylcarboxamides are all compounds copolymerizable therewith. Examples of
these
are vinyl esters of saturated carboxylic acids of 1 to 6 carbon atoms, such as
vinyl
formate, vinyl acetate, vinyl propionate and vinyl butyrate, and vinyl ethers,
such as C,-
to C6-alkyl vinyl ethers, e.g. methyl or ethyl vinyl ether. Further suitable
comonomers
are esters, amides and nitrites of ethylenically unsaturated C3- to C6-
carboxylic acids,
for example methyl acrylate, methyl methacrylate, ethyl acrylate and ethyl
methacrylate, acrylamide and methacrylamide and acrylonitrile and
methacrylonitrile.
Further suitable carboxylic esters are derived from glycols or or polyalkylene
glycols, in
each case only one OH group being esterified, e.g. hydroxyethyl acrylate,
hydroxyethyl
methacrylate, hydroxypropyl acrylate, hydroxybutyl.acrylate, hydroxypropyl
methacrylate, hydroxybutyl methacrylate and monoesters of acrylic acid with
polyalkylene glycols having a molar mass of from 500 to 10 000. Further
suitable
comonomers are esters of ethyfenically unsaturated carboxylic acids with amino
alcohols, for example dimethylaminoethyl acrylate, dimethylaminoethyl
methacrylate,
diethylaminoethyl acrylate, diethyfaminoethyl methacrylate,
dimethylamiriopropyl
PF 54531
CA 02525626 2005-11-14
acrylate, dimethylaminopropyl methacrylate, diethylaminopropyl acrylate,
dimethylaminobutyl acrylate and diethylaminobutyl acrylate. The basic
acrylates can be
used in the form of the free bases, of the salts with mineral acids, such as
hydrochloric
acid, sulfuric aicd or nitric acid, of the salts with organic acids, such as
formic acid,
5 acetic acid, propionic acid or the sulfonic acids, or in quaternized form.
Suitable
quaternizing agents are, for example, dimethyl sulfate, diethyl sulfate,
methyl chloride,
ethyl chloride and benzyl chloride.
Further suitable comonomers are amides of ethylenically unsaturated carboxylic
acids,
10 such as acrylamide, methacrylamide and N-alkylmono- and diamides of
monoethylenically unsaturated carboxylic acids having alkyl radicals of 1 to 6
carbon
atoms, e.g. N-methylacrylamide, N,N-dimethylacrylamide, N-
methylmethacrylamide, N-
ethylacrylamide, N-propylacrylamide and tert-butylacrylamide and basic
(meth)acrylamides, e.g. dimethylaminoethylacrylamide, dimethylaminoethyl
methacrylamide, diethylaminoethylacrylamide, diethylaminoethylmethacrylamide,
dimethylaminopropylacrylamide, diethylaminopropylacrylamide,
dimethyfaminopropylmethacrylamide and diethylaminopropylmethacryfamide.
N-Vinylpyrrolidone, N-vinylcaprolactam, acrylonitrile, methacrylonitrile, N-
vinylimidazole
and substituted N-vinylimidazoles, e.g. N-vinyl-2-methylimidazole, N-vinyl-4-
methylimidazole, N-vinyl-5-methylimidazole and N-vinyl-2-ethylimidazole, and N-
vinylimidazalines, such as N-vinylimidazoline. N-vinyl-2-methylimidazoline and
N-vinyl-
2-ethylimidazoline, are furthermore suitable as comonomers. Apart from being
used in
the form of the free bases, N-vinylimidazoles and N-vinylimidazolines are also
employed in a form neutralized with mineral acids or organic acids or in
quaternized
form, the quaternization preferably being carried out with dimethyl sulfate,
diethyl
sulfate, methyl chloride or benzyl chloride. Diallyldialkylammonium halides,
e.g.
diallyldimethylammonium chloride, are also suitable.
The copolymers comprise for example,
from 95 to 5, preferably from 90 to 10, mol% of at least one N-
vinylcarboxamide
and
- from 5 to 95, preferably from 10 to 90, mol% of other monoethylenically
unsaturated monomers copolymerizable therewith
incorporated in the form of polymerized units. The comonomers are preferably
free of
acid groups.
PF 54531
CA 02525626 2005-11-14
11
Polymers comprising vinylamine units are preferably prepared starting from
homopolymers of N-vinylformamide or from copolymers which are obtainable by
copolymerization of
- N-vinylformamide with
- vinyl formate, vinyl acetate, vinyl propionate, acrylonitrile, N-
vinylcaprolactam, N-
vinylurea, N-vinylpyrrolidone or C,- to C6-alkyl vinyl ethers
and subsequent hydrolysis of the homopolymers or of the copolymers with
formation of
vinylamine units from the polymerized N-vinylformamide units, the degree of
hydrolysis
being, for example, from 5 to 100, preferably from 70 to 100, mol%. The
hydrolysis of
the polymers described above is effected by the action of acids, bases or
enzymes by
known methods. When acids are used as the hydrolyzing agent, vinylamine units
of the
polymers are present as ammonium salt, whereas the free amino groups form in
the
case of the hydrolysis with bases.
In most cases, the degree of hydrolysis of the homo- and copolymers is from 80
to
95 mol%. The degree of hydrolysis of the homopolymers is equivalent to the
content of
vinylamine units in the polymers. In the case of copolymers which comprise
vinyl esters
in the form of polymerized units, hydrolysis of the ester groups with
formation of vinyl
alcohol units may occur in addition to the hydrolysis of the N-vinylfor!ramide
:.nits. This
is the case in particular when the hydrolysis of the copolymers is carried out
in the
presence of sodium hydroxide solution. Acrylonitrile incorporated in the form
of
polymerized units is likewise chemically changed in the hydrolysis. Here, for
example,
amido groups or carboxyl groups form. The homo- and copolymers comprising
vinylamine units may if appropriate comprise up to 20 mol% of amidine units,
which are
formed, for example, by reaction of formic acid with two neighboring amino
groups or
by intramolecular reaction of an amino group with a neighboring amido group,
for
example of N-vinylformamide incorporated in the form of polymerized units. The
molar
masses M", of the polymers comprising vinylamine units are, for example, from
500 to
10 million, preferably from 1 000 to 5 million (determined by light
scattering). This molar
mass range corresponds, for example, to K values of from 5 to 300, preferably
from 10
to 250 (determined according to H. Fikentscher in 5% strength aqueous sodium
chloride solution at 25°C and a polymer concentration of 0.5% by
weight).
The polymers comprising vinylamine units are preferably used in salt-free
form. Salt-
free aqueous solutions of polymers comprising vinylamine units can be
prepared, for
example, from the salt-containing polymer solutions described above with the
aid of
ultrafiltration through suitable membranes at cut-offs of, for example, from 1
000 to
PF 54531
CA 02525626 2005-11-14
12
500 000, preferably from 10 000 to 300 000, Dalton. The below-described
aqueous
solutions of other polymers comprising amino and/or ammonium groups can also
be
obtained in salt-free form with the aid of ultrafiltration.
Derivatives of polymers comprising vinylamine units can also be used as
cationic
polymers. Thus, it is possible, for example, to prepare a multiplicity of
suitable
derivatives from the polymers comprising vinylamine units by amidation,
alkylation,
sulfonamide formation, urea formation, thiourea formation, carbamate
formation,
acylation, carboxymethylation, phosphonomethylation or Michael addition of the
amino
groups of the polymer. Of particular interest here are uncrosslinked
polyvinylguanidines, which are obtainable by reaction of polymers comprising
vinylamine units, preferably polyvinyiamines, with cyanamide (R'R2N-CN, where
R' and
Rz are H, C,- to C4-alkyl, C3- to C6-cycloalkyl, phenyl, benzyl, alkyl-
substituted phenyl
or naphthyl), cf. US-A-6,087,448, column 3, line 64 to column 5, line 14.
The polymers comprising vinylamine units also include hydrolyzed graft
polymers of,
for example, N-vinylformamide on polyalkylene glycols, polyvinyl acetate,
polyvinyl
alcohol, polyvinylformamides, polysaccharides, such as starch,
oligosaccharides or
monosaccharides. The graft polymers are obtainable by subjecting, for example,
N-
vinylformamide to free radical polymerization in an aqueous medium in the
presence of
at least one of said grafting bases, if appropriate together with other
copolymerizable
monomers, and then hydrolzying the grafted-on vinylformamide ~ snits in a
knr_,wn
manner to give vinylamine units.
Suitable cationic polymers are also polymers of
dialkylaminoalkyl(meth)acrylamides.
Suitable monomers for the preparation of such polymers are, for example,
dimethylaminoethylacrylamide, dimethylaminoethylmethacrylamide,
dimethylaminopropylacrylamide, dimethylaminopropylmethacrylamide,
diethylaminoethylacrylamide, diethyfaminoethylmethacrylamide and
diethylaminopropyfacrylamide. These monomers can be used in the form of the
free
bases, of the salts with inorganic or organic acids or in quaternized form in
the
polymerization. They can be subjected to free radical polymerization to give
homopolymers or, together with other copolymerizable monomers, to give
copolymers.
The polymers comprise, for example, at least 30, preferably at least 70,
mol°!° of said
basic monomers incorporated in the form of polymerized units.
Further suitable cationic polymers are polyethylenimines which can be
prepared, for
example, by polymerization of ethylenimine in aqueous solution in the presence
ef
acid-eliminating compounds, acids or Lewis acids as a catalyst.
Polyethylenimines
have, for example, molar masses of 2 million, preferably from 200 to 1 000
000.
PF 54531 CA 02525626 2005-11-14
13
Pofyethylenimines having molar masses of from 500 to 750 000 are particularly
preferably used. The polyethylenimines can, if appropriate, be modified, for
example,
alkoxylated, alkylated or amidated. They can also be subjected to a Michael
addition or
a Stecker synthesis. The polyethylenimine derivatives obtainable thereby are
likewise
suitable as cationic polymers.
Polyamidoamines grafted with ethylenimine and obtainable, for example, by
condensation of dicarboxylic acids with polyamines and subsequent grafting-on
of
ethylenimine are also suitable. Suitable polyamidoamines are obtained, for
example, by
reacting dicarboxylic acids of 4 to 10 carbon atoms with
polyalkylenepolyamines which
comprise from 3 to 10 basic nitrogen atoms in the molecule. Examples of
dicarboxylic
acids are succinic acid, malefic acid, adipic acid, glutaric acid, suberic
acid, sebacic
acid and terephthalic acid. In the preparation of the polyamidoamines,
mixtures of
dicarboxylic acids may also be used, as may mixtures of a plurality of
polyalkylenepolyamines. Suitable polyalkylenepolyamines are, for example,
diethylenetriamine, triethylenetetramine, tetraethylenepentamine,
dipropylenetriamine,
dipropylenetetramine, dihexamethylenetriamine, aminopropylethylenediamine and
bisaminopropylethylenediamine. For the preparation of the polyamidoamines, the
dicarboxylic acids and polyalklenepolyamines are heated to relatively high
temperatures, for example to temperatures in the range from 120 to
220°C, preferably
from 130 to 180°C. The water formed during the condensation is removed
from the
system. In the condensation., lactonPS or lactams ~of carboxylic acids ef 4 to
8 car Son
atoms can, if appropriate, also be used. For example, from 0.8 to 1.4 mol of a
polyalkylenepolyamine are used per mole of a dicarboxylic acid. These
polyamidoamines are grafted with ethylenimine. The grafting reaction is
carried out, for
example, in the presence of acids or Lewis acids, such as sulfuric acid or
boron
trifluoride etherates, at, for example, from 80 to 100°C. Compounds of
this type are
described, for example, in DE-B-24 34 816.
The optionally crosslinked polyamidoamines, which are, if appropriate
additionally
grafted with ethylenimine before the crosslinking, are also suitable as
cationic
polymers. The crosslinked polyamidoamines grafted with ethylenimine are water-
soluble and have, for example, an average molecular weight MW of from 3 000 to
2 million Dalton. Conventional crosslinking agents are, for example,
epichlorohydrin or
bischlorohydrin ethers of alkylene glycols and polyalkylene glycols.
Other suitable cationic polymers are polyallylamines. Polymers of this type
are
obtained by homopofymerization of allylamine, preferably in the form
neutralized with
acids, or by copolymerization of allylamine with other monoethylenically
unsaturated
monomers which are described above as comonomers for N-vinylcarboxarnides.
PF 54531 CA 02525626 2005-11-14
14
In addition, water-soluble crosslinked polyethylenimines which are obtainable
by
reacting polyethylenimines with crosslinking agents, such as epichlorohydrin
or
bischlorohydrin ethers of polyalkylene glycols having from 2 to 100 ethylene
oxide
and/or propylene oxide units and also have free primary and/or secondary amino
groups are suitable. Amidic polyethylenimines which are obtainable, for
example, by
amidation of polyethylenimines with C,- to C22-monocarboxylic acids are also
suitable.
Further suitable cationic polymers are alkylated polyethylenimines and
alkoxylated
polyethylenimines. In the alkoxylation, for example, from 1 to 5 ethylene
oxide or
propylene oxide units are used per NH unit in the polyethylenimine.
The abovementioned cationic polymers have, for example, K values of from 8 to
300,
preferably from 15 to 180 (determined according to H. Fikentscher in 5%
strength
aqueous sodium chloride solution at 25% and at a polymer concentration of 0.5%
by
weight). At a pH of 4.5, they have, for example, a charge density of at least
1,
preferably at least 4, meqlg of polyelectrolyte.
Preferred cationic polymers are polymers comprising vinylamine units and
polyethylenimines. Examples of these are:
vinylamine homopolymers, frcm 10 to 100% hydrolyzed polyvinylformamides,
partly or
completely hydrolyzed copolymers of vinylformamide and vinyl acetate, vinyl
alcohol,
vinylpyrrolidone or acrylamide, in each case having molar masses of 3 000 - 2
000 000,
and
polyethylenimines, crossfinked polyethylenimines or amidated
polyethylenimines, which
have in each case molar masses of from 500 to 3 000 000.
The polymer content of the aqueous solution is, for example, from 1 to 60,
preferably
from 2 to 15, in general from 5 to 10, % by weight.
Cardboard is usually produced by draining a slurry of cellulose fibers. The
use of kraft
pulp is preferred. Furthermore, the use of TMP and CTMP is of particular
interest. The
pH of the cellulose fiber slurry is, for example, from 4 to 8, preferably from
6 to 8. The
drainage of the paper stock can be carried out batchwise or continuously on a
paper
machine. Cationic polymer, engine size and retention aid can be added in any
chosen
sequence. However, a procedure in which first the retention aid and then the
cationic
polymer, preferably polyvinylamine, and then at least one reactive size, such
as
alkylketene dimer, alkyl- or alkenylsuccinic anhydride, in combination with an
aluminum
compound or a mixture of these sizes and a polymer size are added to the
aqueous
PE 54531 CA 02525626 2005-11-14
cellulose fiber slurry is preferred. According to another embodiment, first at
feast one
polymer size, then the retention aid and finally the cationic polymer are
metered.
In the production of the paper products to be used according to the invention,
other
5 assistants usually suitable may be present, for example fixing agents, dyes,
bactericides and dry andJor wet strength agents for paper.
After the drainage of the paper stock and drying of the paper product, an
engine sized
cardboard having a basis weight of from 80 to 400, preferably from 120 to 220,
g/m2 is
10 obtained. The cardboard is laminated on one or both sides with a plastics
film or metal
foil, such as aluminum foil.
Suitable plastics films may be produced from polyethylene, polypropylene,
polyamide
or polyester. The films or foils can be bonded to the sized paper products,
for example,
15 with the aid of an adhesive. In such cases, films or foils which are coated
with an
adhesive are generally uszd and the laminate is pressed. However, the surface
of the
sized paper products can also be coated with an adhesive and the film or foils
then
applied to one or both sides and the resulting laminate pressed. However, the
films or
foils can also be processed with the cardboard directly by the action of
heating and
pressure to give a laminate, from which the suitable structures for production
of the
packaging for liquids are then cut out. The packagings are preferably used in
the food
sector, for example for packing beverages, such as miners! water, juices or
milk, or for
the production of beverage vessels, such as cups. In the case of these
packagings, it is
important that they have good edge penetration, i.e. the cardboard should
absorb very
little or virtually no liquid. The adhesion of films or foils to the paper
products sized with
polymer sizes is better than that of films or foils to paper products which
are sized
exclusively with alkylketene dimers.
1n the examples which follow, percentages are by weight, unless evident
otherwise
from the context. The K values were determined according to H. Fikentscher,
Cellulose-Chemie 13 (1932), 58-64 and 71-74, in 5% strength aqueous sodium
chloride solution at 25°C and a pH of 7 at a polymer concentration of
0.5% by weight.
The molar masses MW of the polymers were measured.by light scattering.
Examples
Determination of the edge penetration
The cardboard produced in each case was laminated on both sides with a
polyethylene
adhesi~~e tape. The thickness of the cardboard was then determined. Test
strips
PF 54531 CA 02525626 2005-11-14
16
measuring 25 x 75 mm were then cut from the cardboard and weighed in each
case. In
order to determine the edge penetration, the test strips were dipped in a bath
which
comprised a 30% strength hydrogen peroxide solution thermostated at
70°C. The test
strips were removed from the bath after a residence time of 10 minutes. Excess
hydrogen peroxide was absorbed by means of filter paper. The test strips were
once
again weighed. The edge penetration in kg/m2 was then calculated from the
increase in
weight.
Ink flotation time
The ink flotation time (measured in minutes) is the time which a test ink
requires
according to DIN 53126 for 50% strike-through through a test sheet.
Cobb value
The determination was carried out according to DIN 53 132 by storing the paper
sheets
for a period of 60 seconds in water. The water absorption is stated in glmz.
Examples 1 to 6
0. 75%, based in each case on dry paper stock, of a cationic starch (Solvitose
BPN)
was added as a retention aid to a paper stock having a consistency of 10 gh
and
comprising 100% unbleached pine sulfate pulp having a freeness of 20°SR
(Schopper-
Riegler), and the pH of the mixture was brought to 7. In each case the amounts
of
stearyldiketene stated in the table, in the form of an aqueous dispersion
(Basoplast~
4118MC), and an aqueous dispersion of the polymer sizes likewise stated in
table 1
were then metered. The fiber slurries were thoroughly mixed in each case and
drained
on a Rapid-Kothen sheet former. Sheets having a basis weight of 150 glm2 were
obtained.
The following polymer sizes were used:
Polymer size A: BasopIastC~ 250D (aqueous dispersion of a copolymer, prepared
by
emulsion polymerization of acrylonitrile and n-butyl acrylate in the presence
of
degraded cationic starch as an emulsifier and hydrogen peroxide as an
initiator).
Polymer size B: Basoplast~ 265D (aqueous dispersion of a copolymer, prepared
by
emulsion polymerization of styrene and n-butyl acrylate in the presence of
degraded
cationic starch as an emulsifier and hydrogen peroxide as an initiator).
PF 54531
CA 02525626 2005-11-14
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Polymer size C: BasopIastO PR8172 (aqueous dispersion of a copolymer, prepared
by
emulsion polymerization of styrene and n-butyl acrylate in the presence of
cationic
starch as an emulsifier and hydrogen peroxide as an initiator).
Table 1
Example Stearyldiketene [%], Amount of polymer size
No. based on dry fibers Type[%], based
on dry fibers
1 0.1 A 0.25
2 0.1 A 0.5
3 0.1 B 0.25
4 0.1 B 0.5
5 0.1 C 0.25
6 0.1 C 0.5
The sheets were then dried on a steam-heated drying cylinder at 90°C to
a water
content of 6 - 10%. After the drying, the Cobb value of the sheets was
determined. The
sheets were then laminated on both sides with an adhesive tape polyethylene
having a
density of 0.918 g/cm' (heating of the laminate under pressure to
30°C). The edge
penetration of the three-layer laminate was then determined. The results are
shown in
table 3.
Comparative examples 1 to 4
0.75%, based in each case on dry paper stock, of a cationic starch (Solvitose
BPN)
was added as a retention aid to a paper stock having a consistency of 10 g/l
and
comprising 100% unbleached pine sulfate pulp having a freeness of 20°SR
(Schopper-
Riegler), and the pH of the mixture was brought to 7. In each case the amounts
of
stearyldiketene shown in table 2 were then metered in the form of an aqueous
dispersion (Basoplast~ 4118MC). Thereafter, in each case the aqueous fiber
slurries
were thoroughly mixed and were drained on a Rapid-Kothen sheet former to give
a
paper product having a basis weight of 150 g/m2.
Table 2
Comparative example [%] stearyldiketene, based on dry
fibers
1 0.1
- 2 0.2
3 0.35
4 0.60
PF 54531 CA 02525626 2005-11-14
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The sheets were then dried on a steam-heated drying cylinder at 90°C to
a water
content of 6 - 10°l0. After the drying, the Cobb value of the sheets
was determined. The
sheets were then adhesively bonded on both sides to a polyethylene adhesive
tape
(pressing of the laminate under pressure). The edge penetration of the three-
layer
laminate with respect to hydrogen peroxide was then determined. The results
ace
shown in table 3.
Table 3
Sample accordingCobb 60 sec for Edge penetration [kg/m'J
to cardboard (Peroxides) for laminated
example cardboard
1 20 10.9
2 21 10.6
3 23 6.6
4 22 4.6
5 20 10.2
6 23 11.3
Sample according
to comparative
example
1 20 12.1
2 24 8.6
3 20 7.2
4 21 5.3
