U.S. patent application number 10/556471 was filed with the patent office on 2007-01-11 for packaging material consisting of an at least double-layered composite material for producing containers for packing liquids.
This patent application is currently assigned to BASF Aktiengesellschaft. Invention is credited to Simon Champ, Roland Ettl.
Application Number | 20070010386 10/556471 |
Document ID | / |
Family ID | 33453863 |
Filed Date | 2007-01-11 |
United States Patent
Application |
20070010386 |
Kind Code |
A1 |
Champ; Simon ; et
al. |
January 11, 2007 |
Packaging material consisting of an at least double-layered
composite material for producing containers for packing liquids
Abstract
Packaging material comprises an at least two-layer laminate of a
paper engine-sized in each case with a polymer size or sized
cardboard and at least one water-impermeable film or foil for
producing containers for packaging liquids, and paper products
which are obtainable in each case by (i) engine sizing of a paper
stock comprising an aqueous slurry of cellulose fibers with at
least one polymer 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, (ii) drainage of the paper stock on the wire of a paper
machine, (iii) drying of the paper product and (iv) lamination of
the paper product on one or both sides with a plastics film or
metal foil are used for producing containers for packaging liquids,
in particular beverages.
Inventors: |
Champ; Simon; (Ludwigshafen,
DE) ; Ettl; Roland; (Hassloch, DE) |
Correspondence
Address: |
C. IRVIN MCCLELLAND;OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
BASF Aktiengesellschaft
Ludwigshafen
DE
67056
|
Family ID: |
33453863 |
Appl. No.: |
10/556471 |
Filed: |
May 6, 2004 |
PCT Filed: |
May 6, 2004 |
PCT NO: |
PCT/EP04/04820 |
371 Date: |
November 10, 2005 |
Current U.S.
Class: |
493/51 ; 162/135;
162/158 |
Current CPC
Class: |
D21H 19/04 20130101;
D21H 19/78 20130101; B32B 2307/7265 20130101; D21H 19/20 20130101;
D21H 27/10 20130101; B32B 29/00 20130101; B32B 27/10 20130101; B32B
2553/00 20130101; D21H 19/22 20130101; D21H 21/16 20130101; D21H
19/84 20130101; B32B 7/12 20130101; D21H 19/30 20130101 |
Class at
Publication: |
493/051 ;
162/135; 162/158 |
International
Class: |
D21H 23/00 20060101
D21H023/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 16, 2003 |
DE |
103222677 |
Jan 13, 2004 |
DE |
1020040019924 |
Claims
1. 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 producing containers for
packaging liquids, wherein the paper or the cardboard is in each
case sized with a polymer size.
2. The packaging material as claimed in claim 1, wherein the paper
or the cardboard is in each case engine sized with a polymer
size.
3. The packaging material as claimed in claim 1, wherein the paper
or the cardboard is in each case surface sized with a polymer
size.
4. The packaging material as claimed in claim 1, wherein the paper
or the cardboard is additionally sized in the presence of aqueous
dispersions of reactive sizes and/or combinations of rosin size and
alum.
5. The packaging material as claimed in claim 1, wherein the paper
or the cardboard is obtainable by successive addition of aqueous
alkylketene dispersions and aqueous polymer size dispersions to the
paper stock and drainage of the paper stock on the wire of a paper
machine.
6. The packaging material as claimed in claim 1, wherein the paper
or the cardboard is obtainable by simultaneous addition of aqueous
alkylketene dimer dispersions and aqueous polymer size dispersions
to the paper stock and drainage of the paper stock on the wire of a
paper machine.
7. The packaging material as claimed in claim 1, wherein the paper
or the cardboard is obtained by sizing with a size mixture
comprising an aqueous polymer size dispersion and an aqueous
alkylketene dimer dispersion.
8. The packaging material as claimed in claim 1, wherein the paper
or the cardboard is additionally sized in the presence of cationic
polymers.
9. The packaging material as claimed in claim 1, wherein the paper
or the cardboard is in each case laminated on both sides with a
water-impermeable plastics film and/or metal foil.
10. The packaging material as claimed in claim 1, wherein the paper
or the cardboard is laminated on one or both sides with a film of
polyethylene, polypropylene, copolymer of ethylene and propylene,
polyester, polyvinyl alcohol, copolymer of ethylene and vinyl
acetate, copolymer of ethylene and vinyl alcohol, or polyamide
and/or an aluminum foil.
11. The packaging material as claimed in claim 1, wherein the paper
or the cardboard has a basis weight of from 80 to 400 g/m.sup.2 and
is laminated on both sides with a polyethylene film.
12. A method for producing a container for packaging liquids
comprising producing a paper product which is obtained by (i)
engine sizing of a paper stock comprising an aqueous slurry of
cellulose fibers with at least one polymer 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, optionally, of a
water-soluble aluminum compound and, optionally, at least one
cationic polymer, (ii) drainage of the paper stock on the wire of a
paper machine, (iii) drying of the paper product and (iv)
lamination of the paper product on one or both sides with a
plastics film or metal foil.
Description
[0001] 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.
[0002] 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.
[0003] 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.
[0004] 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.
[0005] Further multilayer packaging materials whose base layer
consists of paper or cardboard are described, for example, in
WO-A-97/02140, WO-A-97/02181 and WO-A-98/18680.
[0006] 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.
[0007] The prior German application 10237913.0 discloses a process
for producing cardboard for packaging liquids. In this process, the
cardboard is produced by engine sizing of an 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.
[0008] 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.
[0009] 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.
[0010] The present invention also relates to the use of paper
products which are obtainable in each case by
[0011] 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.
[0012] 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.
[0013] 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.
[0014] Further polymer sizes are disclosed in EP-B-0 257 412 and
EP-B-0 267 770. They are prepared by copolymerization of
acrylonitrile and/or methacrylonitrile and at least one acrylate of
a monohydric, saturated C.sub.3- to C.sub.8-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 .eta..sub.i 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 copolymerizatiori of, for 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 on degraded starch.
[0015] Further polymer sizes based on copolymers of styrene and
C.sub.3- to C.sub.8-alkyl (meth)acrylates are disclosed in WO
02/14393. They are prepared by copolymerization of said monomers in
an aqueous medium in the presence of degraded starch and free
radical polymerization initiators by a two-stage process.
[0016] 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 [0017] (a)
styrene, acrylonitrile and/or methacrylonitrile, [0018] (b)
acrylates and/or methacrylates of C.sub.1- to C.sub.18-alcohols
and/or vinyl esters of saturated C.sub.2- to C.sub.4-carboxylic
acids and, if required, [0019] (c) other monoethylenically
unsaturated copolymerizable monomers in aqueous solution in the
presence of 1 part by weight of a solution copolymer of [0020] (1)
di-C.sub.1- to C.sub.4-alkylamino-C.sub.2- to C.sub.4-alkyl
(meth)acrylates which, if appropriate, may be protonated or
quatemized, [0021] (2) nonionic, hydrophobic, ethylenically
unsaturated monomers, in these monomers, if they are polymerized by
themselves, form hydrophobic polymers, and, if appropriate, [0022]
(3) monoethylenically unsaturated C.sub.3- to C.sub.5-carboxylic
acids or their anhydrides, the molar ratio of (1): (2): (3) being
1:2.5 to 10:0 to 1.5, copolymerized.
[0023] First, a solution copolymer is 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.sub.1- to C.sub.3-carboxylic acids, such as formic acid, acetic
acid and propionic acid, or C.sub.1- to C.sub.4-alcohols, such as
methanol, ethanol, n-propanol or isopropanol, and ketones, 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.
[0024] Monomers of group (2) which are used are nonionic,
hydrophobic, ethylenically unsaturated compounds which, if they are
polymerized by themselves, form hydrophobic polymers. These
include, for example, styrene, methylstyrene, C.sub.1- to
C.sub.18-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 methacrylate, 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 copolymerization, for example mixtures of styrene and isobutyl
acrylate. The solution copolymers serving as an emulsifier can, if
appropriate, also comprise monomers of group (3) incorporated in
the form of polymerized units, for example monoethylenically
unsaturated C.sub.3- to C.sub.5-carboxylic acids or their
anhydrides, e.g. acrylic acid, methacrylic acid, itaconic acid,
maleic acid, maleic anhydride or itaconic anhydride. The molar
ratio (1): (2): (3) is 1:2.5 to 10:0 to 1.5. The copolymer
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 and/or methacrylates of
C.sub.1- to C.sub.18-alcohols and/or vinyl esters of saturated
C.sub.2- to C.sub.4-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 C.sub.3- to C.sub.5-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.
[0025] The monomers of group (c) are, if required, used for
modifying the properties of the copolymers.
[0026] 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.
[0027] 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 C.sub.3- to C.sub.8- alcohols and
[0028] from 0 to 20% by weight of other monoethylenically
unsaturated copolymerizable monomers, such as acrylamide,
methacrylamide, vinylformamide, acrylic acid, methacrylic acid,
maleic 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, 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
copolymerizable 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.
[0029] The polymer sizes are preferably cationic or anionic. The
charge of the aqueous dispersions is based either on 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 cationic starch
as an emulsifier leads to cationic polymer size dispersions.
[0030] 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.
[0031] 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, C.sub.5- to C.sub.22-alkyl-
and/or C.sub.5- to C.sub.22-alkenylsuccinic anhydrides,
chloroformic esters and C.sub.12- to C.sub.36-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.
[0032] Among the reactive sizes, C.sub.12- to C.sub.22-alkylketene
dimers, e.g. stearyldiketene, lauryldiketene, palmityldiketene,
oleyldiketene, behenyidiketene or mixtures thereof, are preferably
used.
[0033] Suitable succinic anhydrides are, for example,
decenylsuccinic anhydride, octenylsuccinic anhydride,
dodecenylsuccinic anhydride and n-hexadecenylsuccinic
anhydride.
[0034] 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.
[0035] 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, sulfonated polystyrene,
C.sub.10- to C.sub.22-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 maleic acid,
homopolymers of acrylic acid, homopolymers of methacrylic acid,
copolymers of isobutene and maleic acid and/or acrylic acid,
hydrolyzed copolymers of isobutene or diisobutene and maleic
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 M.sub.W 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.
[0036] 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 50,
preferably from 10 to 30, % by weight, based in each case on the
polymer content, of polymer (100% strength).
[0037] If reactive sizes are used together with a polymer size, the
reactive sizes, preferably alkylketene 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.
[0038] 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.
[0039] The draining of the paper stock 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,
poly(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 acrylates or methacrylates,
for example copolymers of acrylamide arid 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.
[0040] 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.degree. 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.
[0041] 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 and/or
polydiallyidimethylammonium 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.
[0042] Polymers comprising vinylamine units are known, cf. U.S.
Pat. No. 4,421,602, U.S. Pat. No. 5,334,287, EP-A-0 216 387, U.S.
Pat. No. 5,981,689, WO-A-00/63295 and U.S. Pat. No. 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.
[0043] 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.sub.1- to C.sub.6-alkyl vinyl ethers, e.g.
methyl or ethyl vinyl ether. Further suitable comonomers are
esters, amides and nitriles of ethylenically unsaturated C.sub.3-
to C.sub.6-carboxylic acids, for example methyl acrylate, methyl
methacrylate, ethyl acrylate and ethyl methacrylate, acrylamide and
methacrylamide and acrylonitrile and methacrylonitrile.
[0044] Further suitable carboxylic esters are derived from glycols
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 ethylenically
unsaturated carboxylic acids with amino alcohols, for example
dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate,
diethylaminoethyl acrylate, diethylaminoethyl methacrylate,
dimethylaminopropyl 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, 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.
[0045] Further suitable comonomers are amides of ethylenically
unsaturated carboxylic acids, 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, dimethylaminopropylmethacrylamide and
diethylaminopropylmethacrylamide.
[0046] N-Vinylpyrrolidone, N-vinylcaprolactam, acrylonitrile,
methacrylonitrile, N-vinylimidazole and substituted
N-vinylimidazoles, e.g. N-vinyl-2-methylimidazole,
N-vinyl4-methylimidazole, N-vinyl-5-methylimidazole and
N-vinyl-2-ethylimidazole, and N-vinylimidazolines, 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.
[0047] The copolymers comprise for example, [0048] from 95 to 5,
preferably from 90 to 10, mol % of at least one N-vinylcarboxamide
and [0049] 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.
[0050] Polymers comprising vinylamine units are preferably prepared
starting from homopolymers of N-vinylformamide or from copolymers
which are obtainable by copolymerization of [0051] N-vinylformamide
with [0052] vinyl formate, vinyl acetate, vinyl propionate,
acrylonitrile, N-vinylcaprolactam, N-vinylurea, N-vinylpyrrolidone
or C.sub.1- to C.sub.6-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.
[0053] 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-vinylformamide units. 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.sub.W 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.degree. C. and a polymer concentration of 0.5% by
weight).
[0054] 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 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.
[0055] 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
polyvinylamines, with cyanamide (R.sup.1R.sup.2N-CN, where R.sup.1
and R.sup.2 are H, C.sub.1- to C.sub.4-alkyl, C.sub.3- to
C.sub.6-cycloalkyl, phenyl, benzyl, alkyl-substituted phenyl or
naphthyl), cf. U.S. Pat. No. 6,087,448, column 3, line 64 to column
5, line 14.
[0056] 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 units in a known manner to give vinylamine
units.
[0057] 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, diethylaminoethylmethacrylamide and
diethylaminopropylacrylamide. 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.
[0058] Further suitable cationic polymers are polyethylenimines
which can be prepared, for example, by polymerization of
ethylenimine in aqueous solution in the presence of
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. Polyethylenimines 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.
[0059] 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, maleic 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.degree.
C., preferably from 130 to 180.degree. C. The water formed during
the condensation is removed from the system. In the condensation,
lactones or lactams of carboxylic acids of 4 to 8 carbon 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.degree. C. Compounds of this type
are described, for example, in DE-B-24 34 816.
[0060] 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-soluable and have, for example, an average molecular weight
M.sub.W of from 3 000 to 2 million Dalton. Conventional
crosslinking agents are, for example, epichlorohydrin or
bischlorohydrin ethers of alkylene glycols and polyalkylene
glycols.
[0061] Other suitable cationic polymers are polyallylamines.
Polymers of this type are obtained by homopolymerization 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-vinylcarboxainides.
[0062] 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.sub.1- 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.
[0063] The abovementioned catonic 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, meq/g of polyelectrolyte.
[0064] Preferred cationic polymers are polymers comprising
vinylamine units and polyethylenimines. Examples of these are:
[0065] vinylamine homopolymers, from 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, crosslinked 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.
[0066] 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 cellulose
fiber slurry is preferred. According to another embodiment, first
at least one polymer size, then the retention aid and finally the
cationic polymer are metered.
[0067] In the production of the paper products to be used according
to the invention, other assistants usually suitable may be present,
for example fixing agents, dyes, bactericides and dry and/or wet
strength agents for paper.
[0068] 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/m.sup.2 is obtained.
The cardboard is laminated on one or both sides with a plastics
film or metal foil, such as aluminum foil.
[0069] 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, with the aid of an
adhesive. In such cases, films or foils which are coated with an
adhesive are generally used 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 mineral 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.
[0070] In 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.degree. C. and a pH of 7 at a polymer concentration of 0.5% by
weight. The molar masses M.sub.W of the polymers were measured by
light scattering.
EXAMPLE
Determination of the Edge Penetration
[0071] The cardboard produced in each case was laminated on both
sides with a polyethylene adhesive tape. The thickness of the
cardboard was then determined. Test strips measuring 25.times.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.degree. 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/m.sup.2 was then
calculated from the increase in weight.
Ink Flotation Time
[0072] 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
[0073] 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 g/m.sup.2.
Examples 1 to 6
[0074] 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.degree. 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.RTM. 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 g/m.sup.2 were obtained.
[0075] The following polymer sizes were used:
[0076] Polymer size A: Basoplast.RTM. 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).
[0077] Polymer size B: Basoplast.RTM. 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).
[0078] Polymer size C: Basoplast.RTM. 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-US-00001
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
[0079] The sheets were then dried on a steam-heated drying cylinder
at 90.degree. 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.sup.3 (heating of the laminate under pressure
to 30.degree. C.). The edge penetration of the three-layer laminate
was then determined. The results are shown in table 3.
Comparative Examples 1 to 4
[0080] 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.degree. 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.RTM.
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/m.sup.2.
TABLE-US-00002 TABLE 2 Comparative [%] stearyldiketene, example
based on dry fibers 1 0.1 2 0.2 3 0.35 4 0.60
[0081] The sheets were then dried on a steam-heated drying cylinder
at 90.degree. C. to a water content of 6-10%. 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 are shown in table 3. TABLE-US-00003 TABLE
3 Edge penetration [kg/m.sup.2] Cobb 60 sec for (peroxides) for
laminated cardboard cardboard Sample according to example 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
* * * * *