Field of Art
[0001] The present invention relates to a modification of paper-based materials for applications
in packaging, in particular during microwave heating.
Background Art
[0002] The quantity of packaging material production grows exponentially worldwide. The
materials based on cellulose, essentially paper, have the highest quantity in production.
Progressively, important changes occur in structure and properties of the paper thin
layer. Also the generaly known paper applications change towards new technical fields,
e.g. structured foils with phase inclusions, microheterogenic foil materials with
visual signalization (wetness, microbe presence, enzyme, etc.), foil materials with
specific biological activity (intracellular chemical information systems, control
systems for transport flow regulation, immobilization layers of specific cultures,
etc.), foil materials for economic ayay of agricultural production, foil and dispersive
materials for ecological applications.
First paper, produced by felting of fibres, was invented in China at the beginning
of this era. Around the year 600 A.D., this production technology got into Japan and
Middle Asia, and around the year 900 A.D. to North Africa. In 11
th century, paper production began in Europe - in Spain and Italy. Mechanical paper
production began to evolve following the invention of paper machine around the year
1800 A.D. Paper is a product made by felting of fine plant fibres in aqueous dispersion
on a web. Surface paper mass is approximately up to 150 g/m
2. Paper exceeding this surface mass is called carton, and above 250 g/m
2 board. Papers can be divided to graphical papers, used for different kinds of printmaking
and writting, wrapping papers, used to protect different kinds of goods, technical
papers, used in technical practices, and special papers for special technical applications.
From the paper production point of view, it can be divided into two basic phases:
paper pulp preparation, including defibering, grinding, filling, gluing and coloring,
and paper pulp processing, using a paper machine. During the paper pulp preparation,
cellulose fibres are machined, which leads to their structural changes, e.g. fiber
dimension changes, increase in active surface of fibers and swelling of fibres. Individual
fibres undergo phases of defibering, spinning, grinding, egalization and homogenization.
To improve paper physicochemical properties, different types of inorganic fillers
such as kaolin, TiO
2, silica and Al
2O
3 are added to the pulp dispersion being of different shape and size ranging from tens
of nanometers to hundreds of micrometers allowing thus an entrapment of the fillers
particles in the paper cellulose fibrous mash (
WO 2012/059650,
WO 03/080932,
US 7842162). The shape of the kaolin particles used in patent
WO 2012/059650 was in the form of granules and agglomerates of essencially spherical form and being
of preferable size ranging from 10 to 40 µm. In the
US patent 782162 the shape of the filler particles of Al
2O
3 and TiO
2 was in the form of plate-like geometry, however applied clays (kaolinates and hallosites)
were present in the tubule shape. As an addition, the necessity of the oppositely-charged
nanoparticles in comparison to the pulp's fibers charge application is needed to allow
sequencial processing of the layer-by-layer coating of the pulp fibers. The starting
lignocellulose fibers are divided into separate portions which are separately nanocoated
with opposite charge, and then blended to form a complex aggregate pulp of nanocoated
fibers. Polyions used in the assembly are as follows polycations-poly(ethylenimine),
poly(dimethyldiallyl ammonium chloride, poly(allylamine), polylysine, chitosan, and
polyanions - poly(styrenesulfonate), poly(vinylsulfate), poly(acrylic acid), chitosan,
starch and polymers such as carboxymethylcellulose and cationic and anionic starch.
The paper machine is a complex technological device, comprising a head box, web, pressing
and drying parts. Furthermore, it may contain gluing presser, calendering and winding
of paper. In order to obtain a constant quality, paper pulp must be spread over the
web of the paper machine evenly (quantity and speed) along its whole width. Once the
paper pulp spreads over the web, water is removed from it. The head box contains paper
pulp with 0.6 % of dry mass, while by the end of the web the dry mass content is about
50 %. After water removal of a paper sheet on the web of the paper machine, more water
is being removed by pressing, generally in several consecutive pressers with gradually
increasing pressures. Drying part removes water residues and produces paper with dry-mass
of about 95 %. Furthermore, during certain types of paper production, coating of paper
is often required. Coating is performed directly in the paper machine by gluing pressers.
This process is followed by calendering, which gives the paper its required smoothness
and thickness. Winding of paper is the last operation during paper production using
paper machine. It might be followed by cutting into sheets, grading, wrapping and
weighting.
Issues concerning paper based packaging materials (cellulose pulp) and their modifications
for microwave applications are discussed worldwide for several decades. The principal
solution for this kind of packaging is in preparation of paper composed from a plurality
of layers and an inserted metalized PET-based (e.g.
EP 642989), LDPE (
EP 437946,
CN 202295622) polymeric layer, enabling a selective absorbance of microwave energy and a volume
extensibility change (shrinkage) once the final temperature is reached (
JP 2010001041,
US6066375).
US patent 4391833 describes coated heat resistant paperboard product which may be constructed into
a container for food to be used in either conventional or microwave ovens. Paperboard
product is constructed in such a way, that to one side of the surface the water impermeable
layer is appliled and from the other side continuous water permeable layer is affixed.
As an impermeable layer the polytetramethylene terephthalate, or polycyclohexalene
dimethylene terephthalate, and other materials such as polycyclohexalene dimethylene
terephthalate-phtalic acid copolymer, nylon 6, nylon 66, nylon 6/66 copolymers. As
a deposition technique of the water impermeable layer on the paper board the extrusion
coating method is used. In Canadian patent
CA 2867598 is decribed method of preparation of shear resistant preflocullated fillers used
in papermaking. The idea of this patent is in creating larger agglomerates through
treatment with coagulants and/or flocullants prior to their addition to the paper
stock. The whole procedure is based on two step addition of flocculating agents to
the dispersion. As the polymeric flocculants the copolymer and terpolymers of (meth)acrylamide
with dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyl
acrylate, diethylaminoethyl methacrylate or their quarternary ammonium forms made
with dimethyl sulfate, methyl chloride or benzyl chloride. Representative anionic
polymers include copolymers of acrylamide with sodium acrylate and/or 2-acrylamido
2-methylpropane sulfonic acid or an acrylamide homopolymer. As the coagulants the
common inorganic and organic substances on sodium aluminate, ferric and epichlorhydrin-dimethylamine
copolymers etc. are used. Another patent (
US 3804656) discloses preparation of the pigment dispersion and its use in papermaking based
on combination of nonionic surface active agent and a cationic surfactant at an alkaline
pH. As a nonionic dispersant the ethylene oxide condensates of alkyl phenols, ethylene
oxide condensates of alcohols such as octyl alcohol and ethylene oxide condensates
of thioalcohols and mixed condensed polyethylene polypropylene glycols. As the cationic
surface active agents the nonpolymeric quarternary ammonium salts such as lauryldimethyl
benzyl ammonium chloride, lauryltrimethyl ammonium chlopride, di-isobutyl phenoxy
ethoxy ethyl dimethylbenzyl ammonium chloride are used. The nonionic dispersant is
used in amount with the range of 0.1 percent to 0.5 percent, based on the weight of
the pigment or filler. Cationic surface active agent is employed in amount within
the range of 0.1 percent to 0.5 percent of the pigment or filler. The ratio of nonionic
surfactant to cationic surfactant depends on the species of pigment and end use of
the product and generally is in the range of from about 20 to 80 parts by weight nonionic
surfactant to 80 to 20 parts by weight cationic surfactant.
From a practical application point of view, concerning a heat preparation of food
in a microwave field, also the ability of the pagkaging to resist the infiltration
of moisture, oil or grease should be considered important, besides the above mentioned
aspects of efficiency of microwave energy absorption and its transformation to heat.
Disclosure of the Invention
[0003] The subject of the present invention is a paper-based composite planar material,
which contains cellulose fibers and filler particles, selected from kaolin, TiO
2, Al
2O
3 and the mixtures thereof, of size in the range of from 50 nm to 5 µm, preferably
from 0.5 µm to 5 µm. The filler particles content is in the range of from 5 to 65
% (w/w). In order to maintain a perfect dispersion of filler particles, their stabilization
is necessary, using at least one polymeric surfactant of the type of polyoxyglycol
of a weight average molecular mass from 5 kDa to 1.8 MDa.
The composite material further contains a surface layer containing a mixture of at
least one hydrophilic polymer, preferably a cellulose derivative, more preferably
hydroxyethyl cellulose or carboxymethyl cellulose, of the weight mean molecular mass
from 10 kDa to 1.5 MDa, with iron oxide, aluminium oxide, titanium oxide and/or silicon
oxide particles. Said metal oxide may contain the metal in various oxidation states
(for example Fe
2O
3, Fe
3O
4, FeO, FeO
2, Al
2O
3, TiO
2, SiO
2). Starch might be used instead of the hydrophilic polymer. Metal oxide particles
are individually dispersed in the surface layer, and ensure the antimicrobial properties
related to following photochemical, microwave or plazmochemical generation of active
forms of oxygen. The metal oxide particles are present in the surface layer in the
amount of from 0.1 to 15 % (w/w) relative to the dry mass of the composite material.
The surface layer is solidified by physical or chemical procedures by the addition
of cross-linking agent, thermally or plasmachemically (for example by corona treatment
or microwave plasma). For example divinyl sulfone, glutaraldehyde and others might
be used as cross-linking agents, in concentrations in the range of from 0.01 to 7
% (w/w), and optionally other known procedures might be used.
[0004] Filler particles are preferably deposited on the surface of the cellulose fibers.
This is achieved by an addition of colloid dispersion of nano/micro-particles of the
filler, based on kaolinite, TiO
2, Al
2O
3, SiO
2 and/or kaolin, into a dispersion of paper pulp, which is based on cellulose pulp,
during the preparation procedure.
[0005] The described material has significantly better values of vapor, water and oil permeability.
[0006] In a preferred embodiment, the composite material may further contain refining additives
based on acrylate dispersions or vinyl acetate, preferably in the range of from 0.001
to 20 % (w/w), to enable modulation of strength and wettable characteristics.
[0007] In another preferred embodiment, the surface layer might further contain a photochemically
active substance enabling to monitor sterility changes visually by color changes,
which is particularly preferable for example in food-processing and food-storing applications.
[0008] The invention further contains a packaging material for microwave applications, which
contains the composite material according to the present invention.
[0009] The present invention also relates to use of the composite material for microwave
applications and/or for food-processing and/or food-storing applications.
[0010] The present invention further encompasses a method for preparing the composite material,
wherein a colloid dispersion of nano/micro-particles of the filler, based on TiO
2, Al
2O
3, SiO
2 and/or kaolin, having a particle size in the range of from 50 nm to 5 µm, whereas
the filler particle content is in the range of from 5 to 65 % (w/w), is added into
a dispersion of paper pulp based on cellulose pulp, the filler nano/micro particles
are stabilized by addition of a polyoxyglycol type surfactant having a weight average
molecular mass from 5 kDa to 1.8 MDa, and the resulting mixture is placed on a wire
(paper web). The colloid dispersion is stabilized by a surfactant, for example a polymeric
surfactant of the type of polyoxyglycol, preferably of a weight average molecular
mass from 5 kDa to 1.8 MDa. In one preferred embodiment, refining additives based
on acrylate dispersions or vinyl acetate can be added to the mixture.
The resulting composite material is further coated with a surface layer containing
a mixture of at least one hydrophilic polymer, preferably a cellulose derivative,
more preferably hydroxyethyl cellulose or carboxymethyl cellulose, of the weight mean
molecular mass from 10 kDa to 1.5 MDa, with iron oxide, aluminium oxide, titanium
oxide and/or silicon oxide particles, present in the surface layer in the amount of
from 0.1 to 15 % (w/w) relative to the dry mass of the composite material. Said metal
oxide may contain the metal in various oxidation states (for example Fe
2O
3, Fe
3O
4, FeO, FeO
2, Al
2O
3, TiO
2, SiO
2). Starch might be used instead of the hydrophilic polymer. The surface layer is then
solidified by physical or chemical procedures by the addition of cross-linking agent,
thermally or plasmachemically (for example by corona treatment or microwave plasma).
Brief Description of Figures
[0011]
Fig. 1. Depiction of original cellulose fibers (by SEM).
Fig. 2. Depiction of covering of cellulose fibres by microparticles of kaolinite (by
SEM).
Fig. 3. Detailed surface structure of cellulose fibers covered by a kaolinite based
filler (by SEM).
Fig. 4. Dependence of equilibrium contact angle of wetting upon the age of a glycerol
drop for unmodified paper.
Fig. 5. Dependence of equilibrium contact angle of wettability upon the age of a glycerol
drop for a modified paper sample.
Fig. 6. The influence of kaolin addition upon kinetics of glycerol wettability on
studied paper samples. The experimental point empty circle with a cross has been excluded
from the linear regression calculation. Full circle: critical time t1, empty circle: critical time t2.
Fig. 7. The influence of size of the kaolin filler particles (diameter of the particles)
on the kinetics of glycerol wettability on studied paper samples. The experimental
point empty circle with a cross has been excluded from the linear regression calculation.
Full circle: critical time t1, empty circle: critical time t2.
Fig. 8. Mossbauer spektra of a solidified surface layer of carboxymethylcellulose
filled with dispersed nanoparticles of iron(III) oxide with the size of 60 nm (left)
and 40 nm (right): (a) transmission and (b) conversion electrone 57Fe Mossbauer spektra. Measurements were carried out at room temperature of 23 °C.
The concentration of iron(III) oxide nanoparticles was 5 % (w/w).
Examples
Example 1: Preparation of the composite material
[0012] The preparation procedure of the composite material is based on classical paper technologies,
where an additional element (a colloidal dispersion of filler nano/micro particles
based on kaolinite, TiO
2, Al
2O
3, SiO
2 and kaolin in a concentration range of from 2 to 65 % (w/w) and of an exactly defined
mean particle diameter in a range of from 50 nm to 5000 nm) is added to the system
of paper dispersion on the basis of cellulose pulp. The filler nano/micro particles
are stabilized electrostatically, eventually sterically, for example by a polymeric
auxiliary preparation addition, based on amphoteric polymeric polyoxyglycol type surfactant
(e.g. polyethylene oxide (PEO)) of the mean molecular mass in a range of from 5 kDa
to 1.8 MDa and in a concentration range of from 0.0001 to 12.0 % (w/w) of the mass
of the dispersion.
The dispersion treated by the above-described method is further mixed with paper pulp
and deposited on a paper web. By this method, a selective coverage of individual cellulose
fibers by filler particles of exactly defined distribution of particle sizes is achieved,
enabling formation of a complex nano-structured layer in a cross-section of the final
paper sheet. After water removal, common further paper processing is applied, including
pressing and other common paper processing procedures.
Example 2: Paper coating procedure
[0013] Subsequently to the preparation of nano-structured paper according to Example 1,
a coating procedure takes place, using a water soluble dispersion of cellulose derivatives
(preferably hydroxyethyl cellulose, carboxymethyl cellulose) of the mean molecular
mass in a range of from 10 kDa to 1.5 MDa mixed with nanoparticles of iron, aluminium
or silicium oxides of variable oxidation stages or combinations thereof (variable
mass ratio lies in the range of from 0.01 to 30 % (w/w)). The water soluble dispersion
of hydrophile polymers might be replaced by a starch dispersion (e.g. Perlsize or
Perlcoat (Lyckeby Amylex)).
Example 3: Solidification of surface layer
[0014] After the paper coating procedure according to Example 2, its solidification is then
performed using physical or chemical procedures with the addition of a suitable cross-linking
agent. The solidification is performed thermally or plasmachemically (e.g. by corona
treatment or microwave plasma). Divinylsulphon, glutaraldehyde etc. in concentrations
in a range of from 0.01 to 7 % (w/w) might be used as cross-linking agents, or, alternatively,
other known procedures.
Example 4: Material properties evaluation
[0015] In order to evaluate the wettability of the tested papers, a method of following
the kinetics of sinking-in was chosen, based on monitoring of the contact angle of
wetting changes with the age of a glycerole drop. It is possible to expect that when
the contact wetting angle is 0°, the surface is perfectly wet. The time needed to
reach this situation - critical time - corresponds to the time on the x axes (age
of a drop) necessary to obtain a perfect wettability. By comparison of individual
critical times it is possible to compare the resistance of individual papers tested
towards liquid infiltration. As can be seen from kinetic curves, in most cases the
dependence of contact wetting angle of glycerole on studied papers decreased with
increasing time, showing a characteristic linear progression in the starting stages
of infiltration and limit linear progression at the end of the experiment. Therefore
a method of tangents was chosen, and a critical time was calculated as a cross-section
of tangents with the time axes at the beginning and the end of the experiment (see
Fig. 4 for ordinary paper and Fig. 5 for a paper according to Example 3). The first
tangent (from the beginning of the experiment) can be associated with the property
characterizing surface roughness of the sample, influencing the speed of equilibrium
state establishement. The second tangent (from the end of the experiment) can be associated
with the property characterizing the inner structure of the paper, related to the
infiltration into a microporous structure of the paper layer.
Fig. 6 shows the influence of a degree of paper filling (expressed as a kaolin concentration
within a working dispersion) on the critical times t
1 and t
2. As it is apparent from this dependence, the critical time t
1 is not influenced by the filler concentration. On the contrary, the critical time
t
2 depends on the microporous structure of the paper layer, and linearly increases with
increasing concentration of fillers. Such linear increase confirms the increasing
resistance against the infiltration of testing liquid of 75 % (t
2 = 32 s, t
2 of an unfilled paper is 8 s).
The influence of additives in coating of cellulose fibres is demonstated by 15-times
higher increase (from 8 s to 120 s) of both critical times (t
1 and t
2) upon acrylate dispersion addition, comparing with unmodified paper.
The last monitored parameter was the size of filler particles (kaolin). The summary
of the results is in Fig. 7. The granulometry of particles does not influence the
surface roughness of the sample (t
1), related to the technological procedure of paper preparation. However, a significant
increase of paper resistance towards infiltration of liquids for particles with diameter
less than 200 µm (increase of critical time t
2 from 4 s to 39 s) was observed. In order to characterize the infiltration of vapours,
experiments with hexane vapours were performed using selected paper samples using
iGC method (inversion gas chromatography).
The influence of mineral composition, used as microwave radiation absorption, is important
for the efficiency of the change of microwave energy into heat. In our case, we focused
on minerals of the type of kaolin, as a frequent filler in paper applications, but
with an eye on the dependence of dielectric constant (imaginary part) on the size
of the particles, moisture and shape of the particles. Kaolinite exhibits characteristics
suitable for its applications in packaging for microwave heating. Slight warming (temperatures
around 110 °C) takes place.
From the efficient transformation of microwave radiation into heat point of view,
the most suitable layer seems to be a layer of dispersed iron oxide (Fe
3O
4, magnetite), or eventually Fe
2O
3 or other metal oxides in different oxidation states, which are deposited on the surface
of the above mentioned paper, i.e. a composite of cellulose/filler, forming a homogeneous
distribution of magnetite nano particles. Such layer contains a solidified layer of
hydrophilic polymer of a defined molar mass, which is further solidified by physical
or chemical procedures in order to exhibit exactly defined swelling characteristics
when exposed to moisture. This ensures the ability of selective surface wrinklage
of the above described sandwich structure paper/coating, influencing the ability of
microwave radiation absorption by this system. This combination of nano structured
cellulose layer with fibres selectively coated by defined filler particles (with relatively
narrow distribution of particle sizes) based on kaolinite, and a hydrophilic layer
of dispersed magnetite particles of exact granulometry (in the range of from units
to hundreds of nanometers), enabling an efficient absorption of microwave radiation
and its transformation into heat. It can be assumed a selective absorption of the
magnetic, as well as the electrical component of the microwave field by the specifically
organized metal oxide nanoparticles in the prepared planar sandwich composite, e.g.
in octahedral or tetrahedral configuration of iron atoms within the crystal lattice
of its oxide, as it is for a layer of Fe
2O
3 nanoparticles in a solidified carboxymethylcellulose (Fig. 8).
Industrial Applicability
[0016] Coated and filled papers, according to the present invention, can find their applications
mainly in packaging of food used for microwave heating, e.g. roasted corn, pizza,
ready-to-cook food, prepared meals, etc.
1. A paper-based composite planar material, characterized in that it contains cellulose fibers and filler particles selected from kaolin, TiO2, Al2O3 and mixtures thereof, said filler particles having a size in the range of from 50
nm to 5 µm, whereas the filler particle content is in the range of from 5 to 65 %
(w/w), and whereas the paper-based composite planar material further contains at least
one polymeric surfactant of the polyoxyglycol type, having a weight average molecular
mass from 5 kDa to 1.8 MDa, and whereas the paper-based composite planar material
further contains a surface layer containing a mixture of at least one hydrophilic
polymer or starch, preferably a cellulose derivative, with iron oxide, aluminium oxide,
titanium oxide and/or silicon oxide particles, present in the surface layer in the
amount of from 0.1 to 15 % (w/w) relative to the dry mass of the composite material;
the said surface layer being solidified by cross-linking or thermally or plasmachemically.
2. The composite material according to the claim 1, characterized in that the filler particles are deposited on the surface of the cellulose fibers.
3. The composite material according to any one of the preceding claims, characterized in that it further contains at least one acrylate- or vinyl acetate-based refining additive,
suitable for modulation of strength and wettable characteristics.
4. The composite material according to any one of the preceding claims, characterized in that the surface layer further contains a photochemically active substance for monitoring
sterility changes visually using color changes.
5. Packaging material for microwave applications, characterized in that it contains the composite material according to any one of the preceding claims.
6. A method for preparing the composite material according to any one of claims 1 to
4, characterized in that a colloid dispersion of nano/micro-particles of a filler, based on TiO2, Al2O3, SiO2 and/or kaolin, having a particle size in the range of from 50 nm to 5 µm, whereas
the filler particle content is in the range of from 5 to 65 % (w/w), is added into
a dispersion of paper pulp based on cellulose pulp; the filler nano/micro particles
are stabilized by addition of a polyoxyglycol type surfactant having a weight average
molecular mass from 5 kDa to 1.8 MDa; the resulting mixture is placed on a paper web,
wherein the colloid dispersion is stabilized by a surfactant; the resulting composite
material is further coated with a surface layer containing a mixture of at least one
hydrophilic polymer or starch with iron oxide, aluminium oxide, titanium oxide and/or
silicon oxide particles, present in the surface layer in the amount of from 0.1 to
15 % (w/w) relative to the dry mass of the composite material; and the surface layer
is solidified by addition of a cross-linking agent, thermally or plasmachemically.
7. Use of the composite material according to any one of claims 1 to 4 for microwave
applications and/or for food-processing and/or food-storing applications.
1. Papierbasiertes flächiges Kompositmaterial, dadurch gekennzeichnet, dass es Cellulosefasern und Füllstoffpartikel ausgewählt aus Kaolin, TiO2, Al2O3 und Mischungen davon enthält, wobei die Füllstoffpartikel eine Größe im Bereich von
50 nm bis 5 µm aufweisen, wobei der Gehalt an Füllstoffpartikeln liegt im Bereich
von 5 bis 65% (Gew./Gew.), und wobei das papierbasierte flächige Kompositmaterial
weiterhin mindestens ein polymeres Tensid vom Polyoxyglykol-Typ mit einer gewichtsmittleren
Molekülmasse von 5 kDa bis 1,8 MDa enthält, und wobei das papierbasierte flächige
Kompositmaterial weiterhin eine Oberflächenschicht, die eine Mischung aus mindestens
einem hydrophilen Polymer oder Stärke, vorzugsweise einem Cellulosederivat, mit Eisenoxid-,
Aluminiumoxid-, Titanoxid- und/oder Siliciumoxidpartikeln enthält, die Mischung in
der Oberflächenschicht in einer Menge von 0,1 bis 15% (Gew./Gew.) relativ zur Trockenmasse
des Kompositmaterials vorhanden ist; wobei die Oberflächenschicht durch Vernetzung
oder thermisch oder plasmachemisch verfestigt ist.
2. Kompositmaterial nach Anspruch 1, dadurch gekennzeichnet, dass die Füllstoffpartikel auf der Oberfläche der Cellulosefasern abgeschieden sind.
3. Kompositmaterial nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass es ferner mindestens ein auf Acrylat oder Vinylacetat basierendes Raffinationsadditiv
enthält, das zur Modulation der Festigkeit und der benetzbaren Eigenschaften geeignet
ist.
4. Kompositmaterial nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass die Oberflächenschicht ferner eine photochemisch aktive Substanz zur visuellen Überwachung
von Sterilität unter Verwendung von Farbänderungen enthält.
5. Verpackungsmaterial für Mikrowellenanwendungen, dadurch gekennzeichnet, dass es das Kompositmaterial nach einem der vorhergehenden Ansprüche enthält.
6. Verfahren zur Herstellung des Kompositmaterials nach einem der Ansprüche 1 bis 4,
dadurch gekennzeichnet, dass eine Kolloiddispersion aus Nano-/Mikropartikeln eines Füllstoffs, basierend auf TiO2, Al2O3, SiO2 und/oder Kaolin, eine Partikelgröße im Bereich von 50 nm bis 5 µm aufweisend, wobei
der Gehalt an Füllstoffpartikeln im Bereich von 5 bis 65% (Gew./Gew.) liegt, wird
zu einer Dispersion von Papierzellstoff auf Cellulosezellstoffbasis gegeben; die Füllstoff-Nano-/Mikropartikeln
werden durch Zugabe eines Tensids vom Polyoxyglycol-Typ mit einer gewichtsmittleren
Molekülmasse von 5 kDa bis 1,8 MDa stabilisiert; die resultierende Mischung wird auf
eine Papierbahn gelegt, wobei die Kolloiddispersion durch ein Tensid stabilisiert
wird; das resultierende Kompositmaterial wird ferner mit einer Oberflächenschicht
beschichtet, die eine Mischung aus mindestens einem hydrophilen Polymer oder Stärke
mit Eisenoxid-, Aluminiumoxid-, Titanoxid- und/oder Siliciumoxidpartikeln enthält,
die in der Oberflächenschicht in einer Menge von 0,1 bis 15% (Gew./Gew.) vorhanden
sind relativ zur Trockenmasse des Kompositmaterials; und die Oberflächenschicht wird
durch Zugabe eines Vernetzungsmittels thermisch oder plasmachemisch verfestigt.
7. Verwendung des Kompositmaterials nach einem der Ansprüche 1 bis 4 für Mikrowellenanwendungen
und/oder für lebensmittelverarbeitende und/oder lebensmittelspeichernde Anwendungen.
1. Un matériau planaire composite à base de papier, caractérisé en ce qu'il contient des fibres de cellulose et des particules de charge choisies parmi le
kaolin, TiO2, Al2O3 et leurs mélanges, lesdites particules de charge ayant une taille comprise entre
50 nm et 5 µm, la teneur en particules de charge est comprise entre 5 et 65 % (en
poids), et en ce que le matériau planaire composite à base de papier contient en outre au moins un tensioactif
polymère du type polyoxyglycol ayant une masse moléculaire moyenne en poids de 5 kDa
à 1,8 Mda, et en ce que le matériau planaire composite à base de papier contient en outre une couche superficielle
contenant un mélange d'au moins un polymère hydrophile ou amidon, de préférence un
dérivé de cellulose, avec des particules d'oxyde de fer, d'oxyde d'aluminium, d'oxyde
de titane et/ou d'oxyde de silicium, présente dans la couche superficielle en une
quantité de 0,1 à 15% (en poids) par rapport à la masse sèche du matériau composite;
ladite couche superficielle étant solidifiée par réticulation ou par voie thermique
ou plasmachimique.
2. Le matériau composite selon la revendication 1, caractérisé en ce que les particules de charge sont déposées à la surface des fibres de cellulose.
3. Le matériau composite selon l'une quelconque des revendications précédentes, caractérisé en ce qu'il contient en outre au moins un additif d'affinage à base d'acrylate ou d'acétate
de vinyle, l'additif d'affinage étant adapté à la modulation de la résistance et des
caractéristiques mouillables.
4. Le matériau composite selon l'une quelconque des revendications précédentes, caractérisé en ce que la couche superficielle contient en outre une substance photochimiquement active
pour surveiller visuellement les changements de stérilité en utilisant des changements
de couleur.
5. Un matériau d'emballage pour des applications micro-ondes, caractérisé en ce qu'il contient le matériau composite selon l'une quelconque des revendications précédentes.
6. Un procédé de préparation du matériau composite selon l'une quelconque des revendications
1 à 4, caractérisé en ce qu'une dispersion colloïdale de nanoparticules/microparticules de la charge, à base de
TiO2, Al2O3, SiO2 et/ou de kaolin, d'une taille de particule comprise entre 50 nm et 5 µm, et de la
teneur en particules de charge étant comprise entre 5 et 65% (en poids), est ajoutée
dans une dispersion de pâte à papier à base de pâte de cellulose; les nano/micro particules
de charge sont stabilisées par addition d'un tensioactif de type polyoxyglycol ayant
une masse moléculaire moyenne en poids de 5 kDa à 1,8 MDa; le mélange résultant est
placé sur une bande de papier, dans laquelle la dispersion de colloïde est stabilisée
par un tensioactif; le matériau composite résultant est ensuite revêtu d'une couche
superficielle contenant un mélange d'au moins un polymère hydrophile ou d'amidon avec
des particules d'oxyde de fer, d'oxyde d'aluminium, d'oxyde de titane et/ou d'oxyde
de silicium, présentes dans la couche superficielle en une quantité de 0,1 à 15% (en
poids) par rapport à la masse sèche du matériau composite; et la couche superficielle
est solidifiée par l'addition d'un agent de réticulation, ou par voie thermique ou
plasmachimique.
7. Utilisation du matériau composite selon l'une quelconque des revendications 1 à 4
pour des applications micro-ondes et/ou pour des applications agro-alimentaires et/ou
pour des applications de stockage alimentaires.