Note: Descriptions are shown in the official language in which they were submitted.
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Paper and cardboard packaging with barrier coating
Description
The present invention relates to paper or cardboard packaging produced from
mineral oil
contaminated, recycled paper with a barrier layer obtainable by applying an
aqueous polymeric
dispersion comprising a copolymer obtainable by emulsion polymerization of C1-
C4 alkyl
(meth)acrylates, acid monomers and optionally acrylonitrile and further
monomers, wherein the
glass transition temperature of the copolymer is in the range from +10 to +45
C. The barrier
layer may be situated on one of the surfaces of the packaging, or form one of
multiple layers of
a multilayered packaging coating or be situated as a coating on one side of an
inner bag
situated within the packaging.
Paperboard packaging is generally produced from recycled paper. In the case of
printed paper,
especially newspaper, the recycled paper may contain mineral oil residues from
the printing inks
typically used to print newspapers. Even at room temperature, volatiles
evaporate from these
residues and, in the case of food packaging, deposit on the food items packed
in the box, for
example pasta, semolina, rice or cornflakes. Even most of the inner bags
currently used, which
are made of polymer film, do not offer adequate protection. Studies carried
out by Zurich
Cantonal Laboratory detected an appreciable level of mineral oil residues in
food items which
were packed in packaging produced from recycled paper. The volatile mineral
oil constituents
are predominantly paraffinic and naphthenic hydrocarbons, known to be a health
concern, and
aromatic hydrocarbons, especially those of 15-25 carbon atoms.
There is accordingly a need to reduce the risk of food items becoming
contaminated with
mineral oil residues. One possibility would be to dispense with recycling of
newspaper in the
production of paperboards for the packaging of food. This is undesirable for
ecological reasons
and impracticable on account of the insufficient availability of virgin
cellulose. Another solution
would be to dispense with mineral oils in the printing inks for newsprint. But
this comes up
against technological obstacles, particularly with regard to the wipe-off
resistance of the print on
the paper surface. Grease and oil repellent barrier coatings are known in the
packaging sector.
WO 2006/053849 for example describes coatings based on waterborne polymeric
compositions
CA 02835273 2013-11-06
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for paper and board. The polymers do show good barrier properties against
liquid greasy
substances, but it has transpired that this does not necessarily also provide
a good barrier effect
against substances permeating in gaseous form, since the transport mechanisms
for the
permeating substances are different. In the case of liquid oils and greases,
transportation takes
place via the fibers, for which capillary forces and surface wetting play a
part. In the case of
problems with substances transferring in gaseous form, it is not capillarity
and wetting which are
important but sorption, diffusion and porosity. In addition, oils and greases
differ from
hydrocarbons, i.e., from mineral oil constituents, in their polarity and hence
in their diffusivity
through barrier layers.
It is an object of the present invention to provide packaging which despite
use of mineral oil
contaminated, recycled paper reduces the risk of packaged contents becoming
contaminated
with volatile mineral oil constituents.
This object is achieved according to the invention by paper or cardboard
packaging produced at
least partly from mineral oil contaminated, recycled paper, wherein the
packaging includes at
least one barrier layer obtainable by applying an aqueous polymeric dispersion
comprising at
least one copolymer obtainable by emulsion polymerization of
(a) one or more principal monomers selected from the group consisting of C1-
C4 alkyl
(meth)acrylates,
(b) 0.1 to 5 wt% of one or more acid monomers, e.g., selected from acrylic
acid and
methacrylic acid,
(c) 0-20 wt% of acrylonitrile and
(d) 0 to 10 wt% of further monomers other than the monomers (a) to (c),
wherein the glass transition temperature of the copolymer is in the range from
+10 to +45 C,
wherein the barrier layer may be situated on one or more of the surfaces of
the packaging, or
the barrier layer may form at least one of multiple layers of a multilayered
packaging coating or
the barrier layer may be situated as a coating on at least one side of an
inner bag situated within
the packaging. The packaging is useful for food in particular.
Mineral oil contaminated is to be understood as meaning that the paper
comprises amounts of
volatile hydrocarbons, especially volatile paraffins, volatile naphthenes
and/or volatile aromatic
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hydrocarbons having up to 25 carbon atoms, that are detectable by customary
methods of
analysis. Volatile hydrocarbons are hydrocarbons having up to 25 carbon atoms,
for example
from 5 to 22 carbon atoms. In one embodiment of the invention, the mineral oil
contamination
comes from printing inks and comprises volatile paraffins, volatile naphthenes
and/or volatile
aromatic hydrocarbons.
In what follows, the designation "(meth)acryl ..." and similar designations
are used as an
abbreviating notation for "acryl ... or methacryl ...".
The polymeric dispersions to be used according to the invention are
dispersions of polymers in
an aqueous medium. An aqueous medium may be for example completely ion-free
water or
else a mixture of water with a miscible solvent such as methanol, ethanol, or
tetrahydrofuran.
Preferably, no organic solvents are used. The solids contents of the
dispersions are preferably
in the range from 15 to 75 wt%, more preferably in the range from 40 to 60 wt%
and more
particularly above 50 wt%. The solids content can be set for example through
appropriate
adjustment of the water quantity used in the emulsion polymerization and/or of
the monomer
quantities. The median size of the polymer particles dispersed in the aqueous
dispersion is
preferably below 400 nm and more particularly below 300 nm. The median
particle size is more
preferably between 70 and 250 nm or between 80 and 150 nm. Median particle
size here refers
to the d50 value of the particle size distribution, i.e., 50 wt% of the total
mass of all particles have
a particle diameter smaller than the d50 value. The particle size distribution
can be determined in
a known manner using an analytical ultracentrifuge (W. Machtle,
Makromolekulare Chemie 185
(1984), pages 1025 ¨ 1039). The pH of the polymer dispersion is preferably set
to above pH 4
especially to a pH between 5 and 9.
The copolymers to be used according to the present invention are emulsion
polymers
obtainable by emulsion polymerization of free-radically polymerizable
monomers. The
copolymer is formed from one or more principal monomers (a), which are
selected from the
group consisting of C1-C4 alkyl (meth)acrylates. The principal monomers (a)
are preferably used
at not less than 70 wt% and more preferably at not less than 75 wt%, for
example from 79.5 to
99.5 wt%, based on the sum total of all monomers. Particularly preferred
principal monomers (a)
are selected from the group consisting of methyl acrylate, methyl
methacrylate, ethyl acrylate
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and n-butyl acrylate.
The copolymer is formed from one or more acid monomers (b). Acid monomers are
ethylenically
unsaturated free-radically polymerizable monomers with at least one acid
group, for example
monomers with carboxylic acid, sulfonic acid or phosphonic acid groups.
Carboxylic acid groups
are preferred. Acrylic acid, methacrylic acid, itaconic acid, maleic acid or
fumaric acid is suitable
for example. The acid monomers (b) are preferably selected from acrylic acid
and methacrylic
acid. The acid monomers (b) are used at 0.1 to 5 wt% and preferably at 0.5 to
5 wt%, based on
the sum total of all monomers.
The copolymer may optionally be formed of acrylonitrile as further monomer (c)
at 0 to 20 wt%,
based on the sum total of all monomers. In one embodiment of the invention,
the copolymer is
formed from acrylonitrile at 1-20 wt% and preferably 2-20 wt%.
The copolymer can optionally be formed of further monomers (d) other than the
monomers (a)
to (c). The amount of further monomers (d) is 0 to 10 wt% or 0 to 5 wt%, based
on the sum total
of all monomers. One embodiment utilizes from 0.1 to 10 wt% or from 0.1 to 5
wt% of further
monomers (d). Another embodiment utilizes no further monomers other than the
monomers (a)
to (c).
The further monomers (d) may be selected from the group consisting of C5-C20
alkyl
(meth)acrylates, vinyl esters of carboxylic acids comprising up to 20 carbon
atoms,
vinylaromatics having up to 20 carbon atoms, ethylenically unsaturated
nitriles other than
acrylonitrile, vinyl halides, vinyl ethers of alcohols comprising 1 to 10
carbon atoms, aliphatic
hydrocarbons having 2 to 8 carbon atoms and one or two double bonds, or
mixtures thereof.
C5-C10 Alkyl (meth)acrylates, such as 2-ethylhexyl acrylate, are suitable for
example. Mixtures of
alkyl (meth)acrylates are also suitable in particular. Vinyl esters of
carboxylic acids having 1 to
20 carbon atoms are for example vinyl laurate, vinyl stearate, vinyl
propionate, vinyl versatate
and vinyl acetate. Useful vinylaromatic compounds include vinyltoluene, a-
methylstyrene,
p-methylstyrene, alpha-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene and
preferably styrene.
Methacrylonitrile is an example of nitriles. Vinyl halides are chlorine,
fluorine or bromine-
substituted ethylenically unsaturated compounds, preferably vinyl chloride and
vinylidene
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chloride. Vinyl methyl ether and vinyl isobutyl ether are examples of suitable
vinyl ethers.
Preference is given to vinyl ethers of alcohols comprising 1 to 4 carbon
atoms. As hydrocarbons
having 4 to 8 carbon atoms and two olefinic double bonds there may be
mentioned butadiene,
isoprene and chloroprene. C5 to Cio alkyl acrylates and methacrylates and
vinylaromatics,
In one embodiment of the invention, the copolymer is obtainable from
(b) 0.5 to 5 wt% of one or more acid monomers selected from acrylic acid and
methacrylic acid,
(c) 0-20 wt% of acrylonitrile, and
no further monomers other than the monomers (a) to (c).
The monomers of copolymer are adapted in terms of type and amounts such that
the glass
transition temperature of the emulsion polymer is in the range from +10 to +45
C, preferably
from +15 to +40 C. The glass transition temperature can be determined by
differential scanning
calorimetry (ASTM D 3418-08 "midpoint temperature").
Copolymers may be obtained by emulsion polymerization, in which case an
emulsion polymer is
concerned. An emulsion polymerization generally utilizes ionic and/or nonionic
emulsifiers
and/or protective colloids/stabilizers as surface-active compounds to augment
monomer
dispersion in the aqueous medium. Protective colloids are polymeric compounds
which on
polymer particles and water. A detailed description of suitable protective
colloids is found in
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Houben-Weyl, Methoden der organischen Chemie, volume XIV/1, Makromolekulare
Stoffe,
Georg-Thieme-Verlag, Stuttgart, 1961, pages 411 to 420. Useful protective
colloids include for
example amphiphilic polymers, i.e., polymers having hydrophobic and
hydrophilic groups.
Natural polymers, such as starch, or synthetic polymers may be concerned.
Useful emulsifiers
include both anionic and nonionic surface-active substances the number average
molecular
weight of which is typically below 2000 g/mol or preferably below 1500 g/mol,
while the number
average molecular weight of protective colloids is above 2000 g/mol, for
example in the range
from 2000 to 100 000 g/mol and more particularly in the range from 5000 to 50
000 g/mol.
Anionic and nonionic emulsifiers are preferably used as surface-active
substances. Suitable
emulsifiers are for example ethoxylated C8-C36 fatty alcohols having a degree
of ethoxylation in
the range from 3 to 50, ethoxylated mono-, di- and tri-C4-C12-alkylphenols
having a degree of
ethoxylation in the range from 3 to 50, alkali metal salts of dialkyl esters
of sulfosuccinic acid,
alkali metal and ammonium salts of C8-C12 alkyl sulfates, alkali metal and
ammonium salts of
C12-C18alkylsulfonic acids and alkali metal and ammonium salts of C9-C18
alkylarylsulfonic acids.
When emulsifiers and/or protective colloids are (co)used as auxiliaries for
dispersing the
monomers, the amounts used thereof are for example in the range from 0.1 to 5
wt%, based on
the monomers. Trade names of emulsifiers are for example Dowfax 2 A1, Emulan
NP 50,
Dextrol OC 50, Emulgator 825, Emulgator 825 S, Emulan OG, Texapon NSO,
Nekanil
904 S, Lumiten I-RA, Lumiten E 3065, Lumiten ISC, Disponil NLS, Disponil
LDBS 20,
Disponil FES 77, Lutensol AT 18, Steinapol VSL, Emulphor NPS 25. The surface-
active
substance is typically used in amounts of 0.1 to 10 wt%, based on the monomers
to be
polymerized.
The emulsion polymerization temperature is generally in the range from 30 to
130 C and
preferably in the range from 50 to 90 C. The polymerization medium may consist
of water only
but also of mixtures of water with miscible liquids such as methanol. It is
preferable to use just
water. The emulsion polymerization may be carried out not only as a batch
operation but also in
the form of a feed stream addition process, including staged or gradient mode.
Preference is
given to the feed stream addition process wherein a portion of the
polymerization batch is
initially charged, heated to the polymerization temperature, incipiently
polymerized and
subsequently admixed with the rest of the polymerization batch continuously or
else stagewise,
typically via two or more spatially separated feed streams of which one or
more comprise the
,
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monomers in pure or emulsified form.
The emulsion polymerization process may utilize the customary known
assistants, for example
water-soluble initiators and chain transfer agents. Water-soluble initiators
for an emulsion
polymerization are for example ammonium or alkali metal salts of
peroxydisulfuric acid, e.g.
sodium peroxodisulfate, hydrogen peroxide or organic peroxides, for example
tert-butyl
hydroperoxide. Redox (reduction-oxidation) initiator systems are also
suitable. Redox initiator
systems consist of one or more than one usually inorganic reducing agent and
one or more than
one organic or inorganic oxidizing agent. The oxidizing component comprises
for example the
abovementioned initiators for an emulsion polymerization. The reducing
components are for
example alkali metal salts of sulfurous acid, e.g., sodium sulfite, sodium
hydrogensulfite, alkali
metal salts of disulfurous acid such as sodium disulfite, bisulfite addition
compounds of aliphatic
aldehydes and ketones, such as acetone bisulfite or reducing agents such as
hydroxymethane-
sulfinic acid and salts thereof, or ascorbic acid. The redox initiator systems
may be used
together with soluble metal compounds where the metallic component can exist
in two or more
valency states. Customary redox initiator systems are for example ascorbic
acid/iron(II)
sulfate/sodium peroxodisulfate, tert-butyl hydroperoxide/sodium disulfite,
tert-butyl
hydroperoxide/sodium hydroxymethanesulfinic acid or tert-butyl
hydroperoxide/ascorbic acid.
The individual components, for example the reducing component, can also be
mixtures, for
example a mixture of the sodium salt of hydroxymethanesulfinic acid and sodium
disulfite. The
compounds mentioned are usually used in the form of aqueous solutions, the
lower
concentration being determined by the water quantity tolerable in the
dispersion and the upper
concentration by the solubility in water of the compound in question. In
general, the
concentration is in the range from 0.1 to 30 wt%, preferably 0.5 to 20 wt% and
more preferably
1.0 to 10 wt%, based on the solution. The amount of initiators is generally in
the range from 0.1
to 10 wt% and preferably in the range from 0.5 to 5 wt%, based on the monomers
to be
polymerized. Two or more different initiators can also be used in an emulsion
polymerization. To
remove the residual monomers, the initiator is typically also added after the
actual emulsion
polymerization has ended.
Chain transfer agents may be used in the polymerization, for example in
amounts of 0 to 0.8
part by weight, based on 100 parts by weight of the monomers to be
polymerized, which
,
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reduces the molar mass. Suitable chain transfer agents include for example
compounds having
a thiol group such as tert-butyl mercaptan, mercaptoethyl propionate, 2-
ethylhexyl thioglycolate,
ethyl thioglycolate, mercaptoethanol, mercaptopropyltrimethoxysilane, n-
dodecyl mercaptan, or
tert-dodecylmercaptan. It is further possible to use chain transfer agents
without thiol group, for
The polymer dispersion used for coating the packaging may consist solely of
the emulsion
In one embodiment of the invention, the at least one copolymer is used in
combination with up
The coating of polymer dispersion on the substrate acts as a barrier layer. A
particularly
wt% and more particularly at least 5 wt% and up to 60 or up to 75 wt%.
Preferably, the level of
the at least one copolymer in aqueous dispersion is in the range from 15 to 75
wt%, or in the
range from 40 to 60 wt%. Preferred aqueous dispersions of the copolymers have
a viscosity of
to 150 000 mPas, or 200 to 5000 mPas (measured with a Brookfield viscometer at
20 C, 20
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scattering or freeze fracture electron microscopy.
According to the invention, the carrier substrates are coated with an aqueous
dispersion of at
least one of the copolymers described above. Suitable substrates are in
particular paper,
cardboard and polymeric film/sheet. The dispersions used for coating may
comprise further
added or auxiliary substances, for example thickeners to set the rheology,
wetting auxiliaries or
binders.
To use the coating composition, it is applied to paper, cardboard or a
polymeric carrier
film/sheet on coating machines for example. When webs are used, the polymer
dispersion is
typically applied from a trough via an application roll and leveled using an
air brush. Other ways
to apply the coating include for example the reverse gravure process, spraying
processes or a
roller blade or other coating processes known to a person skilled in the art.
The carrier substrate
has been coated on at least one side, i.e., it may have been coated one-
sidedly or both-sidedly.
Preferred application processes for paper and cardboard are curtain coating,
air blade, bar
coating or blade coating. Preferred application processes for film/sheet
coating are blade, wire-
wound bar, airbrush, counterrotating roll application processes,
counterrotating gravure coating,
casting head or nozzle.
The amounts applied to the sheetlike materials are preferably in the range
from 1 to 10 g (of
polymer solids) per m2, preferably from 2 to 7 g/m2 in the case of polymeric
film/sheet or
preferably from 5 to 30 g/m2 in the case of paper or cardboard. After the
coating compositions
have been applied to the carrier substrates, the solvent/water is evaporated.
For this, in the
case of a continuous process, the material may be led through a dryer duct,
which may be
equipped with an infrared irradiating device, for example. Thereafter, the
coated and dried
material is led over a chill roll and finally wound up. The thickness of the
dried coating is
preferably at least 1 pm, more particularly in the range from 1 to 50 pm and
more preferably in
the range from 2 to 30 pm or from 5 to 30 pm.
The barrier layer may be situated on at least one of the surfaces of the
packaging. It may also
form at least one of multiple layers of a multilayered packaging coating, or
it may be situated as
a coating on at least one side of an inner bag within the packaging. The
barrier coating may be
CA 02835273 2013-11-06
applied directly to a surface of the carrier material; however, still other
layers may be situated
between the carrier and the barrier coating, for example primer layers,
further barrier layers or
colored or black and white printing ink layers. The barrier layer is
preferably situated on the
inner side of the packaging, the side which faces the packaged contents.
5
The inner bag is preferably made of a polymeric film/sheet. The material of
the inner bag is
preferably selected from polyolefins, preferably polyethylene or oriented
polypropylene, while
the polyethylene may have been produced not only by the high pressure
polymerization process
but also by the low pressure polymerization process of ethylene. To still
further improve
10 adherence to film/sheet, the carrier film/sheet may first be subjected
to a corona treatment.
Other suitable carrier films/sheets are for example films/sheets of polyester,
such as
polyethylene terephthalate, films/sheets of polyamide, polystyrene and
polyvinyl chloride. In one
embodiment, the carrier material comprises biodegradable films/sheets, for
example of
biodegradable aliphatic-aromatic copolyesters and/or polylactic acid, for
example Ecoflex or
Ecovio0 film/sheet. Suitable copolyesters are formed for example of
alkanediols, especially C2
to C8 alkanediols such as, for example, 1,4-butanediol, of aliphatic
dicarboxylic acids, especially
C2 to C8 dicarboxylic acids such as, for example, adipic acid or of aromatic
dicarboxylic acids
such as terephthalic acid for example.
The thickness of carrier films/sheets is generally in the range from 10 to 200
pm.
To obtain specific surficial or coating properties for the films/sheets and
packaging media, for
example good printability, still better barrier or blocking behavior, good
water resistance, it may
be advantageous for the coated substrates to be overcoated with covering
layers that
additionally confer these desired properties, or for the barrier coating to be
subjected to a
corona treatment. The substrates which have been precoated according to the
invention exhibit
good overcoatability. Overcoating can again be done using one of the processes
recited above,
or simultaneous multiple coating can be done, for example by using a curtain
coater, in a
continuous operation without intermediary winding and unwinding of the
film/sheet or paper for
example. The barrier layer according to the invention is thereby situated in
the interior of the
system, and the covering layer then determines the surficial properties. The
covering layer has
good adherence to the barrier layer.
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The invention also provides a process for producing packaging, which process
comprises a
composition in the form of an above-described aqueous polymeric dispersion
being provided
and applied to a packaging substrate or to the surface of an inner bag and
dried, wherein the
aqueous polymeric dispersion comprises at least one of the above-described
copolymers and
may optionally comprise further polymers.
The invention also provides for the use of an aqueous polymeric dispersion
comprising at least
one of the above-described copolymers for producing a barrier layer against
volatile mineral oil
constituents, more particularly for producing packaging, more particularly
food packaging.
The substrates coated according to the invention exhibit an outstanding
barrier performance
against volatile mineral oil constituents. The coated substrates as such can
be used as
packaging media. The coatings have very good mechanical properties and exhibit
good
blocking behavior for example.
Examples
Unless the context suggests otherwise, percentages are by weight. A reported
content relates to
the content in aqueous solution or dispersion.
The following input materials were used:
DINP diisononyl phthalate
MMA methyl methacrylate
MA methyl acrylate
AS acrylic acid
styrene
nBA n-butyl acrylate
AN acrylonitrile
Bu butadiene
Test for fat barrier
A 10x10 cm sheet of blotting paper was coated with the particular polymer and
contacted with a
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test fat or oil (2 ml of oleic acid for example). The area of the field soaked
through with fat is
measured after up to 16 hours at 60 C. Strikethrough is assessed after x
hours, depending on
quality.
Barrier test against gaseous mineral oil constituents (test method 1)
The following were packed on top of each other:
1. donor: 30g/m2 paper laden with 1% of Gravex 913 mineral oil for printing
inks (Shell)
2. spacer paper to prevent any wetting contact, 30g/m2
3. barrier material to be tested
4. acceptor: commercial PE film 20 pm, LLDPE of density 0.915 g/cm3
This pack (basal dimensions 10x10 cm) was wrapped with aluminum foil on all
sides.
The test system was stored at 60 C and analyzed by periodically cutting off a
strip of the
acceptor film, extracting with n-hexane for 2 h at 25 C and using online HPLC-
GC to measure
the level of mineral oil constituents having 15-25 carbon atoms. The
breakthrough time for the
mineral oil constituents to break through the barrier material was determined.
The breakthrough
time is the time whereafter mineral oil constituents above the detection limit
are first detected in
the extract.
Barrier test against gaseous mineral oil constituents (test method 2)
9 ml of hexane are poured into a vessel containing a sponge and closed with a
lid which has an
opening and a sealing ring (internal diameter 63 mm). The opening is tightly
closed with the
barrier material to be tested, while the barrier material does not come into
contact with the
hexane-drenched sponge. The weight decrease of the vessel is measured. The
weight
decrease is a measure of the hexane exiting through the barrier material via
the gas phase, and
thus is a measure of the barrier performance against gaseous mineral oil
constituents. The
weight decrease in grams is converted to 1 m2 of paper area and then reported
as g/m2 d.
Example 1:
Comparative test of fat barrier/barrier against gaseous mineral oil
constituents
Barrier performance against fats and oils, i.e., against fatty acids and fatty
acid esters (fat
CA 02835273 2013-11-06
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barrier) and the barrier against gaseous mineral oil constituents, i.e.,
against volatile
hydrocarbons (mineral oil barrier hereinbelow) were tested by test 1 for the
polymers listed in
table 1. The results are summarized in table 1.
Table 1: Barrier performances of certain polymers
Polymer Test fat/oil Fat barrier
Mineral oil barrier
amorphous aromatic-aliphatic polyester-
DINP + no penetration -
breakthrough < 4d
polyurethane
partly crystalline aliphatic polyester-
DINP + no penetration -
breakthrough <4d
polyurethane
MMA/MA/AS copolymer DINP - area partially saturated
+ no penetration
Tg ca. 50 C oleic acid with fat
partly crystalline aromatic-aliphatic
DINP + no penetration -
breakthrough < 4d
polyester-polyurethane
DINP
polyethylene film+ no penetration -
breakthrough < ld
oleic acid
S/nBA/AN/AS copolymer, Tg 5 C oleic acid + no penetration -
breakthrough <4d
- no hexane barrier
(test 2)
The results show that coatings having a fat barrier effect do not necessarily
have any efficacy as
barrier against gaseous mineral oil constituents. The MMA/MA/AS copolymer
tested does
actually provide a mineral oil barrier when coated on polyethylene for
example. Yet it was found
that the film-forming properties of this polymer on paper are not good enough,
presumably due
to the high glass transition temperature, and the coating has void areas
wherethrough the test
oil is able to penetrate.
Example 2: Preparation of polymer dispersions
Purge a reactor with nitrogen and add 450.0 g of demineralized water and 3.0 g
of emulsifier
(Disponil LDBS 20, 20% in water) as initial charge. The mixture in the
initial charge is heated
to 70-90 C. Then, 21.43 g of sodium peroxodisulfate (7% strength) are added
before stirring for
50 minutes. Meter the emulsion feed consisting of 240.0 g of water, 26.67 g of
emulsifier
(Dowfax 2A1, 45% in water) and 600.0 g of monomer mixture as per table 2 into
the reactor
over 2 hours. After the emulsion feed has ended allow the system to polymerize
for 45 min. The
reactor is then cooled down to room temperature.
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Solids content: about 45%
Table 2: Copolymer compositions, quantities in wt%
Example Monomers Tg [ C]
d50 [nm]l)
B1 74% EA/10% MMA/15% AN/1% AS
10 104
B2 65 /0 EA/19% MMA/15 /0 AN/1% AS
19 107
B 3 80% MA/19'Y MMA/1% AS 36 97
B 4 90% MA/9% AN/1% AS 29 132
B5 55% EA/44'Y MMA/1% AS 30 110
B 6 65% MA/19'Y MMA/15% AN/1% AS
47
B 7 65% MA/19% MMA/15 /0 AN/1% AS
47
B 8 54% EA/44% MMA/2 /0 AS 33
(calculated) 119
B 9 52% EA/44% MMA/4% AS 36 (calculated) 120
1) Weight average particle size d50
Example 3: Comparative test of barrier against gaseous mineral oil
constituents
Various barrier materials were tested for barrier performance against gaseous
mineral oil
constituents using test method 2. The results are summarized in table 3.
Table 3: Barrier performances of certain polymers
Example Tg [ C] Hexane permeation
[g m2d]
B 1 10 0.2-0.3
B2 19 0.6
B3 36 0.5
B4 29 2
B5 30 0.3
B6 47 100-150
B7 47 120-160
B 8 33 (calculated) 1.8
B 9 36 (calculated) 2.1
55 MA/44 MMA/1 AS copolymer 50 200-270
14 S/69 nBA/14 AN/3 AS copolymer 5 268
30 Bu/65 S/5 AS 20 > 300
' CA 02835273 2013-11-06
The results show that the inventive examples B1 to B5, B8 and B9 have very
good barrier
properties against gaseous mineral oil constituents.
