Stable aqueous dispersions comprising complexed starch

Abstract

Provided is a stable aqueous dispersion suitable for application to different substrates and especially to paper substrates for producing a barrier layer against compounds of the saturated and aromatic hydrocarbon type. The aqueous dispersion comprises destructurized starch in a complexed form. Also provided is the use of aqueous dispersion as a coating composition for paper based substrates, as a microencapsulant of fragrances and as a film-forming component for paints.

Claims

1. A stable aqueous dispersion for a coating composition producing a barrier layer against saturated and aromatic hydrocarbon compounds, comprising starch which consists of destructurized starch in a form complexed with at least one polymer containing groups of different hydrophilicity intercalated in the backbone or outside the backbone, wherein said dispersion has a dynamic viscosity of 30-300 mPa*s and a solid content of 12-50% by weight, and wherein the destructurized starch is a starch that has substantially lost its native granular structure and is substantially free of granular structure residues; and the destructurized starch in a complexed form is a starch free of residues of granular structure that shows one or more crystalline forms of any of the type V.sub.H, V.sub.A and E.sub.H as defined by the following: TABLE-US-00011 Crystalline form V.sub.H V.sub.A E.sub.H (2θ) (2θ) (2θ)  7.4 (±0.3)  7.7 (±0.3)  7.0 (±0.2) 12.8 (±0.2) 13.5 (±0.4) 12.0 (±0.3) 16.7 (±0.2) 15.7 (±0.1) 13.1 (±0.3) 18.3 (±0.2) 17.6 (±0.1) 18.2 (±0.4) 19.7 (±0.3) 19.3 (±0.2)  24.9 (±0.2). 22.2 (±0.2) 20.8 (±0.2) 24.9 (±0.2) 23.7 (±0.1) 26.4 (±0.1) 27.5 (±0.1) 28.6 (±0.1)

2. The stable aqueous dispersion according to claim 1, comprising, with respect to the total weight of the dispersion: 45-95% by weight of water, and 5-55% by weight of a starch-based composition comprising, with respect to the total weight of the starch-based composition: i) 30-90% by weight of destructurized starch; ii) 10-70% by weight of the at least one polymer containing groups of different hydrophilicity intercalated in the backbone or outside the backbone; and iii) 0-25% by weight of at least one plasticizer.

3. The stable aqueous dispersion according to claim 2, wherein said at least one polymer containing groups of different hydrophilicity intercalated in the backbone or outside the backbone is selected from: copolymers of ethylene with vinyl alcohol, acrylic acid and its salts, methacrylic acid and its salts, crotonic acid, itaconic acid and its salts, maleic anhydride, glycidyl methacrylate and mixtures thereof; vinyl acetate/vinyl alcohol copolymers; aliphatic polyurethanes, aliphatic and aliphatic/aromatic polyesters, random or block polyurethane/poly ether, polyurethane/poly ester, polyamide/polyester, polyester/poly ether, polyurea/polyester, polyurea/polyester copolymers, polycaprolactone/urethane, in which the molecular weight of the polycaprolactone blocks is between 300 and 3000.

4. The stable aqueous dispersion according to claim 2, wherein said at least one polymer containing groups of different hydrophilicity intercalated outside the backbone is at least one copolymer of ethylene with vinyl alcohol and/or with acrylic acid.

5. The stable aqueous dispersion according to claim 1, wherein said at least one polymer containing groups of different hydrophilicity intercalated in the backbone or outside the backbone is selected from: copolymers of ethylene with vinyl alcohol, acrylic acid and its salts, methacrylic acid and its salts, crotonic acid, itaconic acid and its salts, maleic anhydride, glycidyl methacrylate and mixtures thereof; vinyl acetate/vinyl alcohol copolymers; aliphatic polyurethanes, aliphatic and aliphatic/aromatic polyesters, random or block polyurethane/poly ether, polyurethane/poly ester, polyamide/polyester, polyester/poly ether, polyurea/polyester, polyurea/polyester copolymers, polycaprolactone/urethane, in which the molecular weight of the polycaprolactone blocks is between 300 and 3000.

6. The stable aqueous dispersion according to claim 5, wherein said at least one polymer containing groups of different hydrophilicity intercalated outside the backbone is at least one copolymer of ethylene with vinyl alcohol and/or with acrylic acid.

7. The stable aqueous dispersion according to claim 1, wherein said at least one polymer containing groups of different hydrophilicity intercalated outside the backbone is at least one copolymer of ethylene with vinyl alcohol and/or with acrylic acid.

8. The stable aqueous dispersion according to claim 7, wherein said at least one copolymer of ethylene with vinyl alcohol contains 20-50% by moles of ethylene units.

9. The stable aqueous dispersion according to claim 7, wherein said at least one copolymer of ethylene with acrylic acid contains 70-99% by weight of ethylene units.

10. A barrier layer against saturated and aromatic hydrocarbon compounds obtained from the aqueous dispersion according to claim 1.

11. A coating composition for paper substrates obtained from the aqueous dispersion according to claim 1.

12. The coating composition according to claim 11, wherein the coating composition is obtainable by a coating process of a paper substrate comprising the steps of: i. applying on at least one face of said paper substrate a layer of the aqueous dispersion as a coating composition; and ii. drying said paper substrate comprising at least one layer of said coating composition.

13. The coating composition according to claim 12, wherein the drying of the paper substrate is effected by means of radiation, convection, contact or any combination thereof.

14. A biodegradable filler for the production of rubbers obtained from the aqueous dispersion according to claim 1.

15. A microencapsulant for fragrances obtained from the aqueous dispersion according to claim 1.

16. A film-forming component for paints comprising the aqueous dispersion according to claim 1.

17. A process for preparing the stable aqueous dispersion according to claim 1, comprising the steps of: i. feeding a starch-based composition comprising starch in a form complexed with at least one polymer containing groups of different hydrophilicity intercalated in the backbone or outside the backbone to a dispersing machine equipped with a vessel and a stirring system comprising at least one rotor and at least one stator; and ii. dispersing the starch-based composition in water by stirring vigorously with tangential speeds of from 10 s.sup.−1 to 50 s.sup.−1 until the dispersion is homogeneous and reaches a constant value of dynamic viscosity, and optionally iii. regulating the solid content of the aqueous dispersion by adding or removing the proper amount of water to reach a solid content of 5-55% by weight.

Description

(1) In a preferred embodiment the coating composition is biodegradable and therefore particularly suitable for the manufacture of laminated paper products which are biodegradable by composting according to standard EN 13432.

(2) FIG. 1 shows a phase contrast microscopy photograph of the dispersion according to Example 5.

(3) FIG. 2 shows a 150×SEM photograph of the cardboard according to Example 7.

(4) FIG. 3 shows a 150×SEM photograph of the cardboard according to Example 8.

(5) FIG. 4 shows a 150×SEM photograph of a cardboard without any coating composition.

(6) This invention will now be illustrated with reference to some non-limiting examples.

Example 1

(7) 56.3 parts of native maize starch (containing 12% by weight of water), 24.8 parts of polyethylene acrylic acid containing 20% by weight of acrylic acid, 7.9 parts of glycerine and 10.1 parts of water have been fed to an OMC twin screw extruder in accordance with the following operative conditions:

(8) thermal profile

(9) feed zone (° C.): 60

(10) extrusion zone (° C.): 145-170-180×4-150×2

(11) throughput (kg/h)=40

(12) SME (specific energy) (kWh/kg)=0.232

Example 2

(13) 49.6 parts of native maize starch (containing 12% by weight of water), 27.5 parts of polyethylene vinylalcohol containing 38% by mole of ethylene, 4.6 parts of polyethylene acrylic acid containing 20% by weight of acrylic acid, 7.2 parts of glycerine and 11.4 parts of water have been fed to a TSA twin screw extruder in accordance with the following operative conditions:

(14) thermal profile

(15) feed zone (° C.): 70

(16) extrusion zone (° C.): 70-180×5-160

(17) throughput (kg/h)=3

(18) SME (specific energy) (kWh/kg)=0.199

(19) The compositions according to Examples 1 and 2 have been grounded up at 25° C. and sieved to a particle size of <250 μm and analysed in a Philips X'Pert θ/2θ x-ray spectrometer using a Bragg-Brentane geometry, using X Cu K.sub.α radiation with λ=1.5416 Å and a power of 1.6 kW. The angular range used was from 5 to 60° (2θ) with steps of 0.03° (2θ) and an acquisition time of two seconds per step.

(20) Analysis of the X-ray pattern revealed the presence of diffraction peaks shown in table 1 indicating formation of the complex between the starch and the polymers containing hydrophobic groups intercalated with hydrophobic sequences (E.sub.H, V.sub.H and V.sub.A forms).

(21) TABLE-US-00002 TABLE 1 diffraction peaks of the Compositions according to Examples 1 and 2 Example 1 (2θ) Example 2 (2θ)  6.8 — 11.8 — — 12.7 13.1 — 18.1 — 20.7 —

(22) The compositions according to Example 1 and 2 have been grounded up at 25° C. and sieved to a particle size of <250 μm have been analyzed by means of a Brabender Viscograph-E Belotti amilograph under the following conditions:

(23) Dry content: 23.1%

(24) Temperature profile: Initial temperature (° C.)=25° C., heating rate (° C./min)=1.5 Peak Temperature=85° C.; Isothermal Step=30′, cooling rate (° C./min)=1.5; Final Temperature (° C.)=25

(25) Rpm=70

(26) Viscosity of Example 1 and 2 in terms of Brabender Units (BU) are respectively of 8 and 6 BU.

Comparative Example 1

(27) 15.2 g of sodium hydroxide (≥97%, Fluka) have been dissolved into 700 ml of deionised water at 95-100° C. under stirring, in a 1 l conical flask equipped with a condensing system.

(28) Once all the sodium hydroxide is dissolved, 70 g of poly(ethylene-co-acrylic acid) (EAA—20% by weight of acrylic acid) Dow Primacor 59801 have been added keeping the system in the same conditions (stirring, temperature and condenser) leaving a reaction time of three hours. The solution is then let to cool down up to 50-60° C. and discharged into aluminium vessels. The aluminium vessels have been put into an oven at 60° C. for 12 hours in order to remove the excess of water and then the obtained salt has been removed by scratching it from the aluminium vessels using a steel spatula. The water content of the obtained salt has been measured by means of thermogravimetrical analysis (Perkin Elmer TGA 7) at 120° C. for 2 hours resulting 9.3%.

(29) 7.48 g of EAANa have been dissolved into 400 ml of deionised water at 50° C. and the solution has been then let cooling down to ambient temperature. An amount of 17 g of native corn starch has been added to the solution and put into a Brabender Viscograph-E Belotti under the following conditions:

(30) Temperature profile: Initial temperature (° C.)=25° C., heating rate (° C./min)=1.5 Peak Temperature=85° C.; Isothermal Step=30′, cooling rate (° C./min)=1.5; Final Temperature (° C.)=25

(31) Rpm=70

(32) The viscosity of Comparative Example 1 in terms of Brabender Units (BU) at the end of the cycle is approximately 70 BU.

Comparative Example 2

(33) 12.2 g of EAANa prepared according to Comparative Example 1 have been dissolved into 400 ml of deionised water at 50° C. and the solution has been then let cooling down to ambient temperature. An amount of 41.4 g of native corn starch has been added to the solution and put into a Brabender Viscograph-E Belotti under the following conditions:

(34) Temperature profile: Initial temperature (° C.)=25° C., heating rate (° C./min)=1.5 Peak Temperature=85° C.; Isothermal Step=30′, cooling rate (° C./min)=1.5; Final Temperature (° C.)=25

(35) Rpm=70

(36) The viscosity of Comparative Example 2 in terms of Brabender Units (BU) at the end of the cycle is approximately 250 BU.

Examples 3 to 6

(37) The compositions according to Example 1 and 2 have been water dispersed using the procedures listed in Table 2.

(38) TABLE-US-00003 TABLE 2 procedures for preparing the dispersions according to Examples 3 to 6 Example 3 Example 4 Example 5 Example 6 Machine IKA IKA IKA IKA Ultra- Ultra- DR2000/ DR2000/ Turrax Turrax 10 10 T25 T25 Recirculating system no no yes yes Grinding and no no yes yes sieving <400 μm Wetting time (under — — 60 60 stirring) before dis- persion (min) Composition according 0.01 0.04 31 — to Example 1 (kg) Composition according — — — 20 to Example 2 water (kg) 0.1 0.1 72 80 water/sulfuric acid 0.002 0 2.1* 0 (96%) 50/50 (m/m) solution (kg) Tangential speed (s.sup.−1) 24 24 28 28 Vessel Volume (dm.sup.3) 0.25 0.25 150 150 Steady stirring revo- 24000 24000 5040 5040 lution speed (1/min) Stirring time(min) 20 20 150 180 Initial temperature (° C.) 25 25 30 30 Final temperature (° C.) 80 85 90 96 *the solution was added after 90 minutes of stirring

(39) The dispersions according to example 3 and 5 have been neutralised with 50% m/m sodium hydroxide solution.

(40) The dispersions according to example 3 to 6, appeared milky and without lumps.

(41) The dispersions according to Examples 3 to 6 and Comparative Examples 1 and 2 have been characterized by dynamic viscosity, melt viscosity, Phase Contrast Optical Microscopy and X-ray diffraction (of the dried dispersion).

(42) The dynamic viscosity of Example 3 (approximately 9% of dry content) and Example 5 (approximately 30% of dry content) and of Comparative Example 1 (approximately 5.5% of dry content) and Comparative Example 2 (approximately 9% of dry content) has been analyzed over a period of two weeks by means of an Haake VT 500 viscometer equipped with an MV-I rotor at 30° C. and 45 rpm. All the aged sample have been previously shacked for 10 seconds in order to homogenize them.

(43) TABLE-US-00004 TABLE 3 dynamic viscosity (mPa * s) over time Time Comparative Comparative (gg) Example 1 Example 2 Example 3 Example 5 0 162 623 72 133 1 144 615 70 131 2 145 620 72 129 3 140 605 72 132 7 134 334 70 134 14 120 310 72 133

(44) While Comparative Examples 1 and 2 show a decreasing viscosity during the two weeks period that is especially remarkable for Comparative Example 2 (higher dry content), the viscosity of Example 3 and Example 5 remains constant.

(45) It has to be highlighted that Comparative Example 1 has approximately the same viscosity of Example 5 but with a solid content of 5.6% against 30%. On the contrary, Comparative Example 2, having the same solid content of Example 3, shows a dynamic viscosity one order of magnitude higher. This is a focal point in order to obtain a significant basic weight of barrier material with a single deposition step keeping the viscosity at a low level, suitable for industrial deposition.

(46) The dispersions according to Examples 4 and 5 have been dried by casting at air at ambient temperature and pelletized. About 30 g of these dried dispersions has been conditioned to a water content of 6.6% (measured by weight loss after 2 h at 120° C.) and a rheological flow curve has been obtained by means of a Göttfert RT2000/V capillary rheometer according to ASTM D-3835 (at T=180° C., L/D=10).

(47) TABLE-US-00005 TABLE 4 melt viscosity Example 4 Example 5 η (Pa * s) η (Pa * s) Initial shear rate (s.sup.−1) = 7.2 6100 344 Final shear rate (s.sup.−1) = 292 481 35

(48) The dried dispersion according to Example 4, where acid is not used, shows a pseudoplasic flow curve trend with viscosity value of an order of magnitude higher than Example 5_where acid is used. This shows how it is possible to adjust the viscosity of the dispersions by reducing the molecular weight of the destructurized starch.

(49) Phase contrast optical microscopy has been performed on the dispersion according to Example 5 by means of a Leitz Wetzlar Orthoplan model phase contrast optical microscope using the following parameters: magnification 400×, objective EF 40/0.65 Phaco 2, phase ring no. 5. A drop of dispersion has been placed on a microscopic glass with a Pasteur pipette and observed after having placed another microscopic glass onto it and thinned the thickness with a gentle pressure. The dispersion proved to be free of any residues with a granular structure that could be attributed to native starch or to granular starch residues, thus providing evidence of the destructurized nature of the starch (see FIG. 1)

(50) X-ray diffraction of the dried dispersion according to Example 5 and Comparative Example 1 has been performed by means of a Philips X'Pert θ/2θ x-ray spectrometer equipped with a Bragg-Brentano geometry, using X Cu K.sub.α radiation with λ=1.5416 Å and a power of 1.6 kW. The angular range used was from 5 to 60° (2θ) with steps of 0.03° (2θ) and an acquisition time of two seconds per step.

(51) Analysis of the X-ray pattern revealed the presence of diffraction peaks shown in table 5 indicating loss of native starch crystallinity and formation of the complex between the starch and the polymers containing hydrophobic groups intercalated with hydrophobic sequences (V.sub.H).

(52) TABLE-US-00006 TABLE 5 diffraction peaks of the dispersion according to Example 5 and Comparative Example 1 Example 5 (2θ) Comparative Example 1 (2θ) 12.9 — — 18.5 19.7 —

(53) In this case, it can be highlighted that the diffraction peaks present in the dried dispersion according to Example 5, differs from the diffraction peaks detected for the composition according to Example 1. Without willing to be bound to any theory, it is believed that this change in the diffraction peaks distribution is linked to the transition from a crystalline form to another during the preparation of the dispersion.

Example 7

(54) A recycled cardboard sheets of A4 size of 450 μm thickness has been coated in a single deposition step with approximately 10 ml of dispersion according to Example 5 by means of a pipette and removing the excess of dispersion by rolling a steel rod long 40 cm and having a diameter of 7 mm. Straight after deposition, the cardboard has been put in an oven at 200° C. for 30 s for drying it.

(55) Then it has been let to condition at ambient temperature overnight.

(56) A basic weight of dry coating of approximately 15 g/m.sup.2 has been obtained with a single deposition step.

Example 8

(57) A recycled cardboard sheets of A4 size of 450 μm thickness has been coated in a single deposition step with approximately 10 ml of dispersion according to Example 6 by means of a pipette and removing the excess of dispersion by rolling a steel rod long 40 cm and having a diameter of 7 mm. Straight after deposition, the cardboard has been put in an oven at 200° C. for 30 s for drying it.

(58) Then it has been let to condition at ambient temperature overnight.

(59) A basic weight of dry coating of approximately 13 g/m.sup.2 has been obtained with a single deposition step.

(60) The coated cardboards according to Example 7 and 8 have been cut into approximately 30 pieces of nearly 8×3 cm. A pair of pieces has been sunk for half of their length in a 100 ml becker filled with deionised water for nearly 5 seconds. Then the sunk coated faces of one piece has been slightly scratched for a few seconds to the sunk coated face of the other piece and mostly of the coating has been moved from the cardboard into the water. This operation has been repeated on the other half of the two pieces for all the 30 pieces.

(61) The water has been removed by a gentle air flow under mild heating (i.e. 60° C.) and a final drying step has been performed in an oven at 120° C. for 2 hours.

(62) At the end of this step an amount of approximately 500 mg to 1 g of dry coating has been obtained which once pulverized with mortar and pestle has been analyzed by X-ray diffraction by means of a Philips X'Pert θ/2θ x-ray spectrometer using a Bragg-Brentano geometry, using X Cu K.sub.α radiation with λ=1.5416 Å and a power of 1.6 kW. The angular range used was from 5 to 60° (2θ) with steps of 0.03° (2θ) and an acquisition time of two seconds per step.

(63) Analysis of the X-ray pattern revealed the presence of diffraction peaks shown in table 7 indicating of the presence of the complex between the starch and the polymers containing hydrophobic groups intercalated with hydrophobic sequences (V.sub.H and V.sub.A).

(64) TABLE-US-00007 TABLE 7 diffraction peaks of the coating composition after removal from the cardboard Example 7 (2θ) Example 8 (2θ) 13.1 12.8 19.6 19.6 20.8

(65) This shows that the diffraction peaks of the complexed starch are detectable after removal from the cardboard of the coating composition.

(66) A piece of 5×5 mm size of the cardboards according to Example 7, 8 and untreated cardboard has been gold coated by means of an Agar B7341 sputter coater at a current strength of 40 mA for 40 seconds.

(67) Then the samples have been analysed using a Zeiss Supra 40 scanning electron microscope with the following operative conditions:

(68) magnification: 150-1000× (with reference to Polaroid standard 545)

(69) accelerating voltage=10 kV

(70) working distance=approximately 5 mm

(71) The cardboards coated according to Example 7 (see FIG. 2) and 8 (see FIG. 3) show a uniform surface, i.e. a substantially complete coverage of the surface cellulose fibres present on the surface of the untreated cardboard (see FIG. 4)

(72) Determination of the Barrier Effect Against Saturated and Aromatic Hydrocarbons of the Dispersion According to Example 5

(73) Preparation of the Polluting Solutions PS1: a solution made of (w/w): Hexadecane (Sigma-Aldrich Reagent Plus 99%) 92.0%, Phenanthrene (Acros Organics 97%) 6.6%, Hexacosane (hereinafter “C26H54”) (Aldrich 99%) 1.7% has been prepared in a 20 ml flask under stirring at 70° C. for 3 hours. PS2: a solution made of (w/w): Toluene (Sigma-Aldrich Chromasolv 99.9%) 99.29%, Perylene (Fluka 97%) 0.47%, C26H54 (Aldrich 99%) 0.24% has been prepared in a 20 ml flask under stirring at 80° C. for 3 hours.

(74) Preparation of Polluted Cardboards PC1: 25 μl of PS1 have been added (at approximately 70° C.) by means of an Hamilton 25 μl microsyringe to a piece of virgin cardboard of 270 μm thickness of 3.5×3.5 cm size and conditioned at ambient temperature for half an hour. PC2: 240 □μl of PS2 have been added (at approximately 80° C.) by means of an ILS 500□□ μl microsyringe to a piece of virgin cardboard of 270□ μm thickness of 3.5×3.5 cm size. The solution addition has been made in three steps (3×80 □μl) in order to avoid overflowing. The cardboard has been then conditioned at ambient temperature for half an hour. PC3: a commercial recycled cardboard of 450 μm thickness of 7×7 cm size has been also taken as further Polluted Cardboard (PC3).

(75) Coating of Polluted Cardboards

(76) a) Coating with the Dispersion According to Example 5

(77) PC1, PC2 and PC3 have been coated in one single step with approximately 3 ml of dispersion according to Example 5 by means of a pasteur pipette removing the excess of dispersion by rolling a steel rod long 40 cm and having a diameter of 7 mm. Straight after deposition, the cardboards have been put in an oven at 200° C. for 30 s for drying it.

(78) Then they have been let to condition at ambient temperature overnight.

(79) The basic weight of the dry coating has been found to be of 15 g/m.sup.2

(80) Test of Migration on Rice (PC1/PC2 Cardboards)

(81) Approximately 6 g of rice (Riso Fino S. Andrea—Italy) have been put in two different weighing bottles of 55 mm of diameters covering homogeneously their bottom.

(82) PC1-Example 5 and PC2-Example 5 have been put inside the weighing bottles with the polluted side facing the rice. In order to assure the contact between the cardboard and the rice a weight of 56 g over a surface of 23×23 mm has been put on the cardboard.

(83) Then the weighing bottle has been covered and put in an oven at 40° C. for 9 days.

(84) Test of Migration on Activated Charcoal (PC3 Cardboard)

(85) Approximately 9 g of activated charcoal 8-20 mesh (Sigma Aldrich) have been put in one weighing bottle of 11 cm of diameters covering homogeneously their bottom.

(86) PC3-Example 5 has been put inside the weighing bottle with the polluted side facing the activated charcoal. In order to assure the contact between the cardboard and the activated charcoal a weight of 97 g over a circular surface of 24 cm2 has been put on the cardboard. Then the weighing bottle has been covered and put in an oven at 70° C. for 24 hours.

(87) Pollutant Extraction from PC1/PC2 Migration Test on Rice

(88) At the end of migration test, activated charcoal or rice have been put inside a 50 ml flask and 20 ml of toluene (Sigma-Aldrich Chromasolv 99.9%) have been added. The flask has been heated up to 170° C. under stirring with a condensing system and the extraction has been carried on for 2 hours.

(89) Pollutant Extraction from PC3 Migration Test on Activated Charcoal

(90) At the end of migration test, activated charcoal or rice have been put inside a 50 ml flask and 30 ml of toluene (Sigma-Aldrich Chromasolv 99.9%) have been added. The flask has been heated up to 170° C. under stirring with a condensing system and the extraction has been carried on for 2 hours.

(91) Pollutant Extraction from PC1/PC2/PC3 Cardboards (Reference)

(92) In order to have a reference of the amount of MOSH and MOAH inside the cardboards, PC1, PC2 and PC3 have been cut in pieces of about 1.5×1.5 cm and put inside a 50 ml flask and 20 ml of toluene (Sigma-Aldrich Chromasolv 99.9%) for PC1/PC2 or 30 ml for PC3, have been added. The flask has been heated up to 170° C. under stirring with a condensing system and the extraction has been carried on for 2 hours.

(93) Gas Chromatography-Mass Spectrometry (GC-MS) Analysis

(94) An amount of 1 ml of liquid coming from the extraction has been filtered at 0.2 μl into 1 ml vials and sealed before performing GC-MS analysis in the following conditions:

(95) Gas-Chromatograph: Thermo Trace GC Ultra;

(96) Column: Phenomenex Zebron ZB-5MSi (length: 30 m—diameter: 0.25 mm;

(97) Injector temperature (° C.)=300;

(98) Transfer-line temperature (° C.)=280;

(99) Carrier=Helium;

(100) Flow (ml/min)=1;

(101) Split Flow (ml/min)=50;

(102) Temperature run:

(103) Isothermal step (° C.-min)=70-4;

(104) Temperature scan: T.sub.in(° C.)=70—heating rate (° C./min)=15-T.sub.fin(° C.)=340;

(105) Isothermal step (° C.-min)=340-5;

(106) Injection type: splitless;

(107) Injection volume (μ1)=1;

(108) Mass Spectrometer: Thermo DSQ

(109) Source temperature (° C.)=250;

(110) Ionization type: ElectronImpact;

(111) Scan Type: Polluted cardboard positive ion SIM; Recycled Cardboard: Full Scan

(112) Peak detection for polluted cardboards (D): phenanthrene=178; C26H54=57+366; perylene=252

(113) Peak detection for recycled cardboard (D): 33-500

(114) Two repetitions of each sample have been analyzed by GC-MS and results are calculated in terms of peak area of the single molecular ion and percentage of reduction of the interested peak on treated samples compared to the reference).

(115) For each pollutant, the barrier effect of the coating composition according to the invention has been determined according to the following formula:

(116) $\mathrm{barrier}\mathrm{effect}=\frac{\left(P_{\mathrm{reference}}-P_{\mathrm{PCi}\text{-}\mathrm{Example}5}\right)}{P_{\mathrm{referemce}}}.Math.100$

(117) Wherein P.sub.reference=peak area of the single molecular ion in the reference cardboard (without coating); P.sub.PCi-Example 5=peak area of the single molecular ion in the PC1, PC2 or PC3 cardboard (with coating layer obtained with the dispersion according to Example 5)

(118) The results of the migration tests are reported in herebelow tables 8-10

(119) TABLE-US-00008 TABLE 8 Results of migration on rice with PC1cardboards Barrier effect (%) phenanthrene 97.3 C26H54 99.8

(120) TABLE-US-00009 TABLE 9 Results of migration on rice with PC2cardboards Barrier effect (%) Perylene 100.0 C26H54 98.8

(121) TABLE-US-00010 TABLE 10 Results of migration on activated charcoal with PC3 cardboards Barrier effect (%) Alkane C23H48 95.8 Alkane C24H50 97.6 Alkane C25H52 100.0 Alkane C26H54 99.6 Alkane C27H56 100.0