| US20210245481A1 | 2021-08-12 | |||
| EP3638846A1 | 2020-04-22 | |||
| US5897411A | 1999-04-27 |
| CLAIMS A method for producing a food grade paper material with a water vapour and oxygen barrier effect in sheets or rolls, characterised by subjecting at least one surface of a paper substrate to a treatment with at least one dispersion comprising a polymer resin-based binding dispersing phase comprising a polyurethane resin and a dispersed PVOH and/or SiO2-based phase, wherein said dispersion has between 5 and 50 % by weight of said dispersed phase, wherein said treatment envisages the application of one or more treatment layers that form a uniform coating of said at least one surface having a weight comprised between 10 and 25 gr/m2 The method for producing a food grade paper material with a water vapour and oxygen barrier effect in sheets or rolls according to the preceding claim, characterised in that said dispersed phase is provided in turn in the form of an aqueous dispersion. The method for producing a food grade paper material with a water vapour and oxygen barrier effect in sheets or rolls according to any preceding claim, characterised in that said polymer resin-based binding dispersing phase comprises an acrylic resin functionalised with -COOH groups. The method for producing a food grade paper material with a water vapour and oxygen barrier effect in sheets or rolls according to claim 2, characterised in that said dispersing phase comprises said polyurethane resin in a mixture with a styrene-acrylic and/or styrene- butadiene synthetic latex. The method for producing a food grade paper material with a water vapour and oxygen barrier effect in sheets or rolls according to the preceding claim, characterised in that said dispersing phase has from 2 to 4 parts by weight of synthetic latex for every part by weight of PVOH. The method for producing a food grade paper material with a water vapour and oxygen barrier effect in sheets or rolls according to either of claims 4 and 5, characterised in that said dispersing phase has from 1 to 2 parts by weight of synthetic latex for every part by weight of polyurethane resin. The method for producing a food grade paper material with a water vapour and oxygen barrier effect in sheets or rolls according to any preceding claim, characterised in that said dispersed phase also includes inorganic pigments selected from talc and/or kaolin. The method for producing a food grade paper material with a water vapour and oxygen barrier effect in sheets or rolls according to any preceding claim, characterised in that said coating has a viscosity comprised between 120 and 400 cP at 6 RPM. The method for producing a food grade paper material with a water vapour and oxygen barrier effect in sheets or rolls according to any preceding claim, characterised in that said treatment is formulated so as to impart barrier properties having OTR values of less than 1 CC/m2/day at 23°C and 50%RH and WVTR values of less than 1 CC/m2/day at 23°C and 50%RH. A food grade paper material with a water vapour and oxygen barrier effect in sheets or rolls, characterised in that it comprises a paper substrate comprising cellulose fibres, at least one polymeric substance and an inorganic filler, and at least one surface of said paper substrate treated with at least one dispersion comprising a polymer resin-based binding dispersing phase comprising a polyurethane resin and a dispersed PVOH and/or SiO2- based phase, wherein said dispersion has between 5 and 50 % by weight of said dispersed phase, wherein said treatment envisages the application of one or more treatment layers that form a uniform coating of said at least one surface having a weight comprised between 10 and 25 gr/m2. |
VAPOUR AND OXYGEN BARRIER EFFECT IN SHEETS OR ROLLS AND PAPER MATERIAL THUS OBTAINED
DESCRIPTION
The present invention refers to a method for producing a food grade paper material with a water vapour and oxygen barrier effect in sheets or rolls, and to a paper material thus obtained.
Paper materials in sheets or rolls with oxygen barrier (in jargon "OTR") and water vapour (in jargon "WVTR") properties at different temperature and humidity conditions are known.
Such barrier properties are mostly obtained by the combination of a polymeric layer derived from extruded or coupled polyolefins.
These paper materials are used, for example, in the food packaging sector where barrier effect, printability and recyclability are key factors.
One of the major drawbacks related to the use of these paper materials is represented by the presence of the polymeric layer derived from polyolefins.
This polymeric layer, in addition to not complying with some directives in force in the food sector (for example, the guidelines inherent in SUP and related Legislative Decree no. 196 of 8 November 2021), does not allow obtaining those oxygen and water vapour barrier values (e.g. OTR values around 50 CC/m2/day at 23°C and 50%RH and WVTR values around 50 CC/m2/day at 23 °C and 50%RH) that are particularly wished in the food packaging sector.
The technical task proposed by the present invention is, therefore, to realize a method for producing a food grade paper material with a water vapour and oxygen barrier effect in sheets or rolls, and a paper material thus obtained that eliminate the drawbacks of the known art.
Within the scope of this technical task, an object of the invention is to provide a food grade paper material in sheets or rolls with all the above-mentioned barrier functions having OTR values lower than 1 CC/m2/day at 23°C and 50%RH and WVTR values lower than 1 CC/m2/day at 23°C and 50%RH.
Another object of the invention is to provide a food grade paper material in sheets or rolls that is heat sealable on one side while maintaining printability characteristics.
Another object of the invention is to realise a food grade paper material in sheets or rolls with the mentioned barrier properties durable over time.
A further object of the invention is to realise a paper material for food use in sheets or rolls that can be produced in a simple and repeatable way with the use of well-established techniques.
The technical task, as well as this and other objects, according to the present invention are reached by providing a method for producing a food grade paper material with a water vapour and oxygen barrier effect in sheets or rolls, characterised by subjecting at least one surface of a paper substrate to a treatment with at least one dispersion comprising a polymer resin-based binding dispersing phase and a PVOH- and/or SiCh-based dispersed phase.
Said paper substrate is made by means of a continuous papermaking machine.
In one embodiment of the invention said binding dispersing phase is transparent.
In one embodiment of the invention said polymer resin comprises a polyurethane resin.
In one embodiment of the invention said dispersed phase is in turn provided in the form of an aqueous dispersion.
In one embodiment of the invention said polymer resin-based binding dispersing phase comprises an acrylic resin functionalised with -COOH groups.
In one embodiment of the invention said dispersing phase comprises said polyurethane resin in a mixture with a styrene-acrylic and/or styrene-butadiene and/or polyester polyurethane synthetic latex.
In one embodiment of the invention said dispersing phase has from 2 to 4 parts by weight of synthetic latex for every part by weight of PVOH.
In one embodiment of the invention said dispersing phase has from 1 to 2 parts by weight of synthetic latex for every part by weight of polyurethane resin.
In one embodiment of the invention said dispersion has between 5 and 50% by weight of said dispersed phase.
In one embodiment of the invention said dispersed phase also includes inorganic pigments selected from talc and/or kaolin.
In one embodiment of the invention said treatment provides for the application of one or more treatment layers that form a uniform coating of said at least one surface.
In one embodiment of the invention said coating has a weight comprised between 10 and 25 gr/m 2 .
In one embodiment of the invention said coating has a viscosity comprised between 120 and 400 cP at 6 RPM.
In one embodiment of the invention said treatment is formulated so as to impart barrier properties having OTR values of less than 1 CC/m2/day at 23°C and 50%RH and WVTR values of less than 1 CC/m2/day at 23 °C and 50%RH.
The present invention also refers to a food grade paper material with a water vapour and oxygen barrier effect in sheets or rolls.
In one embodiment of the invention said paper material comprises a paper substrate comprising cellulose fibres, at least one polymeric substance and an inorganic filler, and at least one surface of said paper substrate treated with at least one dispersion comprising a polymer resin-based binding dispersing phase and a PVOH- and/or SiO2-based dispersed phase.
Said paper material, as mentioned, has barrier properties having OTR values of less than 1 CC/m2/day at 23°C and 50%RH and WVTR values of less than 1 CC/m2/day at 23°C and 50%RH.
Advantageously, the surface treatment adopted is based on dispersions in water.
The desired barrier effect is therefore obtained from an aqueous-based coating, without the need for further processing such as those on the market (e.g. extrusions, couplings or laminations).
The paper material is therefore suitable for direct and indirect contact with dry and fatty foods, is recyclable according to European standards (for example Aticelca 501:2019), printable and reworkable for the production of sachets or functional packaging.
Obviously the treatment can be applied to only one or also to both main surfaces of the paper material.
One of the most advantageous aspects of the invention consists in the use of natural and/or synthetic resins used as a binder in the dispersing phase of the dispersion.
The use of synthetic resins, among which the polyurethane resin, has surprisingly turned out to be particularly suitable due to the fact of carrying out a closing action of the treated surface which is therefore more homogeneous and consequently more suitable for laying homogeneous layers of printing inks, and at the same time due to the fact of increasing the binding power and of increasing the oxygen and water vapour barrier at particularly low values less than 1 CC/m2/day at 23 °C and 50%RH while maintaining good printability characteristics and allowing good heat-sealability.
Surprisingly it was also found that the use of a dispersion of PVOH-based polymers and silicones in the first treatment layers allows a further closure of the paper without compromising printability.
In the paper substrate the polymeric substance is adapted to give the cellulose fibres dry and wet mechanical resistance, and the inorganic filler is adapted to give the material good machinability and chemical stability characteristics. Preferably, the polymeric substance included in the paper substrate comprises one or more resins based on colophony and/or alkyl ketene dimer and/or acetyl succinic acid and/or epichlorohydrin and/or carboxymethylcellulose.
Preferably, the inorganic filler is a mineral filler comprising one or more substances selected in the group consisting of carbonates, kaolins, talc and mixtures thereof.
The process for manufacturing the aforementioned paper material in sheets, involves making the paper substrate by means of a continuous papermaking machine, and applying the functional surface treatment outside and downstream of the continuous papermaking machine.
To promote polymerization of the binders of the dispersing phase, the paper substrate in sheets can be subjected to heating in an infrared or hot air oven.
By way of example, two possible compositions of the paper material in sheets are shown below.
EXAMPLE 1
Paper material in sheets
- paper substrate: 85% by weight
-first treatment layer: 10% by weight
-second treatment layer: 5% by weight of which the paper substrate is of a type and composition known in the state of the art while the treatment layers have the composition shown below.
First treatment layer
Dispersion and emulsion phase of which:
- PVOH dispersion: 50% by weight
-styrene-acrylic synthetic latex: 49%
-silicone emulsion: 1%
Second treatment layer Dispersing phase of which:
- polyurethane resin 20% by weight
-styrene-acrylic synthetic latex: 70%
-silicone emulsion: 1%
-additives: 9%
EXAMPLE 2
Paper material in sheets
- paper substrate: 80% by weight
-first treatment layer (patina): 15% by weight
-second treatment layer: 5% by weight
-third treatment layer: 5% by weight of which the paper substrate is of the type and composition known in the state of the art while the treatment layers have the composition shown below.
First treatment layer
-inorganic pigment, particularly talc or kaolin: 30% by weight
-styrene-butadiene synthetic latex: 60%
-additives: 10%
Second treatment layer
Dispersion and emulsion phase of which:
- PVOH dispersion: 50% by weight
-styrene-acrylic synthetic latex: 40%
-additives: 10%
Third treatment layer
Dispersing phase of which: - polyurethane resin 30% by weight
-styrene-acrylic synthetic latex: 50%
- dispersion of ester-based polymers and mixtures of non-glyceride esters based on natural wax 10%
-silicone emulsion: 1%
-additives: 9%
The paper material with barrier properties in sheets and/or rolls thus conceived is susceptible to numerous modifications and variants, all falling within the scope of the inventive concept; moreover, all the details are replaceable by technically equivalent elements.
In practice, the materials used, as well as the dimensions, can be any depending on the needs and the state of the art.
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