Use of a coating layer with an acrylate polymer on a paper substrate for blocking oxygen transfer

Abstract

The invention relates to a use of a coating layer on a paper substrate for blocking oxygen transfer through the coated paper substrate, wherein the coating layer on the paper substrate is obtainable by a process, which comprises the steps of (a) providing a paper substrate with a surface, (b) applying onto the surface of the provided paper substrate an aqueous coating mass, and (c) drying of the paper substrate with the applied aqueous coating mass to obtain the coated paper substrate, wherein the aqueous coating mass contains an aqueous dispersion of a polymer P, which is obtainable by radically initiated emulsion polymerization of at least 25 parts by weight of a C.sub.1-C.sub.12 alkyl acrylate or a C.sub.1-C.sub.12 alkyl methacrylate based on the sum total of the parts by weight of all monomers, which is always 100, in the presence of a first degraded starch. It relates further to a coated paper substrate obtainable with a coating mass comprising the aqueous dispersion of the polymer P and a further saccharide, which is added after the polymerization of the monomers. It relates also to a process for manufacturing the coated paper substrate obtainable with a coating mass comprising the aqueous dispersion of the polymer P and the further saccharide.

Claims

1. A process for preparing a coated paper substrate comprising a coating layer on a paper substrate, wherein the coating layer is configured to block oxygen transfer through the coated paper substrate, the process comprising: applying onto the surface of the paper substrate an aqueous coating mass; and drying of the paper substrate with the applied aqueous coating mass to obtain the coated paper substrate; wherein the aqueous coating mass comprises an aqueous dispersion of a polymer, which is obtainable by radically initiated emulsion polymerization of: (i) at least 25 parts by weight of an acrylate monomer, which is a C.sub.1-C.sub.12 alkyl acrylate or a C.sub.1-C.sub.12 alkyl methacrylate; (ii) 0 to 70 parts by weight of styrene; (iii) 0 to 5 parts by weight of an acidic monomer, which contains one ethylenically unsaturated group and at least one acid group; (iv) 0 to 3 parts by weight of a crosslinking monomer, which contains at least two non-conjugated ethylenically unsaturated groups; (v) 0 to 2 parts by weight of butadiene; (vi) 0 to 20 parts by weight of a further monomer, which contains an ethylenically unsaturated group and which is different to the acrylate monomer, styrene, the acidic monomer, the crosslinking monomer or butadiene; wherein the sum total of the parts by weight of the monomers (i), (ii), (iii), (iv), (v) and (vi) is 100; in the presence of a first degraded starch in an amount of from 5 to 80 parts by weight based on the sum total of the parts by weight of the monomers (i), (ii), (iii), (iv), (v) and (vi), and a further saccharide, which is added after the polymerization of the monomers (i), (ii), (iii), (iv), (v) and (vi), and wherein the weight ratio of the sum of the monomers (i), (ii), (iii), (iv), (v) and (vi) and the first degraded starch to the further saccharide is from 5 to 0.25.

2. The process of claim 1, wherein the monomers (i), (ii), (iii), (iv), (v) and (vi) are selected in a way, that the dried aqueous dispersion of the polymer, which is polymerized in the presence of the first degraded starch, possesses a glass transition temperature below 40 C. as determined by the norm ISO 11357-2.

3. The process of claim 1, wherein the acrylate monomer is a C.sub.1-C.sub.8 alkyl acrylate or a C.sub.1-C.sub.8 alkyl methacrylate.

4. The process of claim 1, wherein the radically initiated emulsion polymerization comprises 20 to 70 parts by weight of styrene.

5. The process of claim 1, wherein the acidic monomer is an , -ethylenically unsaturated C.sub.3-C.sub.6 carboxylic acid.

6. The process of claim 1, wherein the radically initiated emulsion polymerization comprises 0 part by weight of a crosslinking monomer.

7. The process of claim 1, wherein The use according to any preceding claim, wherein the radically initiated emulsion polymerization comprises 0 part by weight of butadiene.

8. The process of claim 1, wherein an amount of the further saccharide is from 21 to 720 parts by weight based on the sum total parts by weight of the monomers (i), (ii), (iii), (iv), (v) and (vi).

9. The process of claim 1, wherein the further saccharide is a native starch, a second degraded starch, which can chemically be similar to the first degraded starch, a chemically modified starch, a cellulose, a hemicellulose or a xyloglucane.

10. The process of claim 1, wherein the aqueous coating mass consists of: the aqueous dispersion of the polymer P; optionally the further saccharide; and an auxiliary ingredient; wherein the overall amount by weight of the sum total of the monomers (i), (ii), (iii), (iv), (v) and (vi), the first degraded starch and the further saccharide is at least 85% by weight based on the overall weight of the solids content of the aqueous coating mass.

11. A coated paper substrate, which possesses a coating layer on a surface of the paper substrate, wherein the coating layer on the surface of the paper substrate is obtainable by a process comprising: applying onto the surface of the paper substrate an aqueous coating mass; and drying of the paper substrate with the applied aqueous coating mass to obtain the coated paper substrate; wherein the aqueous coating mass comprises an aqueous dispersion of a polymer, which is obtainable by radically initiated emulsion polymerization of: (i) at least 25 parts by weight of an acrylate monomer, which is a C1-C12 alkyl acrylate or a C1-C12 alkyl methacrylate; (ii) 0 to 70 parts by weight of styrene; (iii) 0 to 5 parts by weight of an acidic monomer, which contains one ethylenically unsaturated group and at least one acid group; (iv) 0 to 3 parts by weight of a crosslinking monomer, which contains at least two non-conjugated ethylenically unsaturated groups; (v) 0 to 2 parts by weight of butadiene; (vi) 0 to 20 parts by weight of a further monomer, which contains an ethylenically unsaturated group and which is different to the acrylate monomer, styrene, the acidic monomer, the crosslinking monomer or butadiene; wherein the sum total of the parts by weight of the monomers (i), (ii), (iii), (iv), (v) and (vi) is 100; in the presence of a first degraded starch in an amount of from 5 to 80 parts by weight based on the sum total of the parts by weight of the monomers (i), (ii), (iii), (iv), (v) and (vi); and a further saccharide, which is added after the polymerization of the monomers (i), (ii), (iii), (iv), (v) and (vi); and wherein the weight ratio of the sum of the monomers (i), (ii), (iii), (iv), (v) and (vi) and the first degraded starch to the further saccharide is from 5 to 0.25.

12. The coated paper substrate of claim 11, wherein the monomers (i), (ii), (iii), (iv), (v) and (vi) are selected in a way, that the dried aqueous dispersion of the polymer, which is polymerized in the presence of the first degraded starch, possesses a glass transition temperature below 40 C. as determined by the norm ISO 11357-2.

13. The coated paper substrate of claim 11, wherein the acrylate monomer is a C.sub.1-C.sub.8 alkyl acrylate or a C.sub.1-C.sub.8 alkyl methacrylate.

14. The coated paper substrate of claim 11, wherein the radically initiated emulsion polymerization comprises 20 to 70 parts by weight of styrene.

15. The coated paper substrate of claim 11, wherein the acidic monomer is an , -ethylenically unsaturated C.sub.3-C.sub.6 carboxylic acid.

16. The coated paper substrate of claim 11, wherein an amount of the further saccharide is from 21 to 720 parts by weight based on the sum total parts by weight of the monomers (i), (ii), (iii), (iv), (v) and (vi).

17. The coated paper substrate of claim 11, wherein the aqueous coating mass further comprises an auxiliary ingredient in an amount of 0 to 15 parts by weight based on the sum total of the parts by weight of the monomers (i), (ii), (iii), (iv), (v) and (vi).

18. The coated paper substrate of claim 11, wherein the paper substrate is a paper or a cardboard.

19. The coated paper substrate of claim 11, wherein the coated paper substrate is a segment of a wall of a container suitable for packaging, which possesses an interior room completely surrounded by the wall, wherein from 45% to 100% of the area of the wall based on the overall area of the wall is the segment.

20. A process for manufacturing a coated paper substrate, which possesses a coating layer on a surface of a paper substrate, the process comprising: applying onto the surface of the provided paper substrate an aqueous coating mass; and drying of the paper substrate with the applied aqueous coating mass to obtain the coated paper substrate; wherein the aqueous coating mass comprises: an aqueous dispersion of a polymer, which is obtainable by radically initiated emulsion polymerization of: (i) at least 25 parts by weight of an acrylate monomer, which is a C1-C12 alkyl acrylate or a Cl-C12 alkyl methacrylate; (ii) 0 to 70 parts by weight of styrene; (iii) 0 to 5 parts by weight of an acidic monomer, which contains one ethylenically unsaturated group and at least one acid group; (iv) 0 to 3 parts by weight of a crosslinking monomer, which contains at least two non-conjugated ethylenically unsaturated groups; (v) 0 to 2 parts by weight of butadiene; (vi) 0 to 20 parts by weight of a further monomer, which contains an ethylenically unsaturated group and which is different to the acrylate monomer, styrene, the acidic monomer, the crosslinking monomer or butadiene; wherein the sum total of the parts by weight of the monomers (i), (ii), (iii), (iv), (v) and (vi) is 100; in the presence of a first degraded starch in an amount of from 5 to 80 parts by weight based on the sum total of the parts by weight of the monomers (i), (ii), (iii), (iv), (v) and (vi); and a further saccharide, which is added after the polymerization of the monomers (i), (ii), (iii), (iv), (v) and (vi); wherein the weight ratio of the sum of the monomers (i), (ii), (iii), (iv), (v) and (vi) and the first degraded starch to the further saccharide is from 5 to 0.25.

Description

EXPERIMENTAL PART

(1) Unless the context suggests otherwise, percentages are always by weight. A reported content is based on the content in aqueous solution or dispersion if not stated otherwise.

(2) Numerical values for content in the tables are rounded to full numbers if not stated otherwise.

(3) The solids content is measured as the weight obtained when a defined amount, for example 5 g, is dried at 140 C. in a drying cabinet to a constant weight.

(4) The glass transition temperature of the aqueous polymer dispersions is determined by differential scanning calorimetry in analogy to DIN EN ISO 11357-2. A sample is poured out a room temperature and evaporates in laboratory atmosphere overnight. Afterwards, a drying at 120 C. for 1 hour takes place. The DSC apparatus Q2000 from TA Instruments Inc. is run with a program of heating to 150 C., maintaining for 2 minutes, fast cooling to 130 C. and afterwards heating with 20 K/minute. The analysis of Tg occurs in accordance with ISO 11357-2 (half height).

(5) Synthesis of Aqueous Polymer Dispersions

(6) Materials:

(7) AA acrylic acid EA ethyl acrylate MMA methyl methacrylate nBA n-butyl acrylate ST styrene MD maltodextrin APBDS alkylated phenoxybenzenedisulfonate, sodium salt SUS/ITD mixture of sulphosuccinate, sodium salt and of isotridecanol ethoxylate SPDS peroxodisulfate, sodium salt H.sub.2O.sub.2 hydrogen peroxide ASCA ascorbic acid

(8) The used maltodextrin is C*Plus 10988 (RTM Cargill, aqueous solution with a content of 50% by weight) based on corn starch and dextrin equivalents in the range from 16.5-19.9.

(9) The used sodium salt of an alkylated phenoxybenzene disulfonate is Dowfax 2A1 (RTM Dow Chemical, an aqueous solution with a content of 45% by weight).

(10) The used mixture of sulphosuccinate, sodium salt and of isotridecanol ethoxylate is Lumiten I-SC (RTM BASF, an aqueous solution with a content of 58% by weight).

(11) The other used materials are commercially available for example from Aldrich Inc. or BASF SE.

Example D-1

Aqueous Polymer Dispersion No. D1

(12) After flushing a reactor with nitrogen, 203 g demineralized water and 0.5 g aqueous solution of Dowfax 2A1 (45% by weight) are placed in a reactor. The resulting mixture is heated to 92 C. Afterwards, a mixture of 240 g water, 6 g aqueous solution of Dowfax 2A1 (45% by weight), 15 g acrylic acid, 350 g n-butyl acrylate and 136 g styrene as an emulsion feed is added into the reactor over 3 hours. At the same time as the emulsion feed, 48 g solution of aqueous sodium peroxodisulfate solution (7% by weight) as an initiator feed is also added over 3.5 hours into the reactor. After the end of the initiator feed, the mixture is kept at 92 C. for 30 minutes for the completion of the polymerization. The reaction mixture is then cooled down to room temperature. The pH is adjusted to approximately pH 7 using an aqueous solution of sodium hydroxide (15% by weight) to obtain an aqueous polymer dispersion, which has a solid content of 50%. The Tg is 5 C.

Example D-2

Aqueous Polymer Dispersion No. D2

(13) After flushing a reactor with nitrogen, 234 g demineralized water and 324 g aqueous solution of maltodextrin (C*Plus 10998, RTM Cargill, 50% by weight) are placed in the reactor. The resulting mixture is heated to 92 C. Afterwards, 21.4 g aqueous solution of sodium peroxodisulfate (7% by weight) is added and stirred for 5 minutes. A mixture of 207 g water, 11 g aqueous solution of Dowfax 2A1 (45% by weight), 15 g acrylic acid, 311 g n-butyl acrylate and 214 g styrene as an emulsion feed is added into the reactor over 3 hours. At the same time as the emulsion feed, 50 g of an aqueous solution of sodium peroxodisulfate (7% by weight) as an initiator feed is also added over 3.5 hours into the reactor. After the end of the initiator feed, the mixture is kept at 92 C. for 30 minutes for the completion of the polymerization. The reaction mixture is then cooled down to room temperature. The pH is adjusted to approximately pH 7 using an aqueous solution of sodium hydroxide (15% by weight) to obtain an aqueous polymer dispersion, which has a solid content of 50%. The Tg is 12 C.

Example D-3

Aqueous Polymer Dispersion No. D3

(14) After flushing a reactor with nitrogen, 135.0 g demineralized water and 217.3 g aqueous solution of maltodextrin (C*Plus 10998, RTM Cargill, 50% by weight) are placed in the reactor. The resulting mixture is heated to 92 C. Afterwards, 2.59 g aqueous solution of sodium peroxodisulfate (7% by weight) is added and stirred for 5 minutes. A mixture of 156.3 g water, 12.1 g of an aqueous solution of Dowfax 2A1 (45% by weight), 3.12 g of an aqueous solution of Lumiten I-SC (58% by weight), 3.63 g acrylic acid, 159.4 g methyl methacrylate and 199.26 g ethyl acrylate as an emulsion feed is added into the reactor over 3 hours. Concomitantly to the emulsion feed, 10.36 g aqueous solution of sodium peroxodisulfate (7% by weight) as an initiator feed is also added over the 3.5 hours into the reactor. After the end of the emulsion feed and the initiator feed, the mixture is kept at 92 C. for 45 minutes for the completion of the polymerization. Afterwards, 1.45 g of an aqueous solution of hydrogen peroxide (25% by weight) is added and then a feed consisting of 13.06 g water and 6.37 g ascorbic acid is started and fed over 30 minutes to the reactor. Then the reactor is cooled to room temperature. The pH is adjusted to approximately pH 7 using an aqueous solution of sodium hydroxide (15% by weight) to obtain an aqueous polymer dispersion having a solid content of 50% with a pH of around 2. The Tg is 25 C.

Example D-4

Aqueous Polymer Dispersion No. D4

(15) After flushing a reactor with nitrogen, 203 g demineralized water and 0.5 g aqueous solution of Dowfax 2A1 (45% by weight) are placed in a reactor. The resulting mixture is heated to 92 C. Afterwards, a mixture of 240 g water, 9.25 g aqueous solution of Dowfax 2A1 (45% by weight), 15 g acrylic acid, 290 g n-butyl acrylate and 196 g styrene as an emulsion feed is added into the reactor over 3 hours. At the same time as the emulsion feed, 61.7 g solution of aqueous sodium peroxodisulfate solution (7% by weight) as an initiator feed is also added over 3.5 hours into the reactor. After the end of the initiator feed, the mixture is kept at 92 C. for 30 minutes for the completion of the polymerization. The reaction mixture is then cooled down to room temperature. The pH is adjusted to approximately pH 7 using an aqueous solution of sodium hydroxide (15% by weight) to obtain an aqueous polymer dispersion, which has a solid content of 50%. The Tg is 7 C.

Example D-5

Aqueous Polymer Dispersion No. D5

(16) After flushing a reactor with nitrogen, 135.0 g demineralized water is placed in the reactor. The resulting mixture is heated to 92 C. Afterwards, 2.59 g aqueous solution of sodium peroxodisulfate (7% by weight) is added and stirred for 5 minutes. A mixture of 156.3 g water, 12.1 g of an aqueous solution of Dowfax 2A1 (45% by weight), 3.12 g of an aqueous solution of Lumiten I-SC (58% by weight), 3.63 g acrylic acid, 159.4 g methyl methacrylate and 199.26 g ethyl acrylate as an emulsion feed is added into the reactor over 3 hours. Concomitantly to the emulsion feed, 10.36 g aqueous solution of sodium perox-odisulfate (7% by weight) as an initiator feed is also added over the 3.5 hours into the reactor. After the end of the emulsion feed and the initiator feed, the mixture is kept at 92 C. for 45 minutes for the completion of the polymerization. Afterwards, 1.45 g of an aqueous solution of hydrogen peroxide (25% by weight) is added and then a feed consisting of 13.06 g water and 6.37 g ascorbic acid is started and fed over 30 minutes to the reactor. Then the reactor is cooled to room temperature. The pH is adjusted to approximately pH 7 using an aqueous solution of sodium hydroxide (15% by weight) to obtain an aqueous polymer dispersion having a solid content of 50% with a pH of around 2. The Tg is 29 C.

(17) Table 1-A summarizes the employed amounts of monomers, other ingredients and radical initiators for the polymer dispersions No. D1 to D5 on a relative weight basis, i.e. parts per hundred parts of monomers. Additionally, the formal solid content less initial MD, the formal solid content of initial MD and the formal solid content of reacted monomers are stated.

(18) TABLE-US-00001 TABLE 1-A monomer/ dispersion No. other ingredient D1.sup.a) D2.sup.b) D3.sup.b) D4.sup.a) D5.sup.a) AA 3 3 1 3 1 EA 55 55 MMA 44 44 nBA 70 58 58 ST 27 39 39 initial MD.sup.c) 30 30 APBDS 0.6 0.9 1.5 0.9 1.5 SUS/ITD 0.5 0.5 SPDS 0.7 0.9 0.2 0.9 0.2 H.sub.2O.sub.2 0.1 0.1 ASCA 0.2 0.2 formal solid 100 77 77 100 100 content less initial MD.sup.d) [%] formal solid 23 23 content of initial MD [%] formal solid 99 76 75 98 98 content of reacted monomers [%] Footnotes: .sup.a)comparative .sup.b)according to the invention .sup.c)MD present at beginning of polymerization .sup.d)relative content of parts other than initial MD based on the solids content of the aqueous dispersion e) relative content of parts of initial MD based on the solids content of the aqueous dispersion
Mixtures of Synthesized Aqueous Polymer Dispersions with Maltodextrin
Procedure

(19) An aqueous polymer dispersion is mixed with an aqueous solution of maltodextrin (C*Plus 10998, RTM Cargill, 50% by weight) by stirring at 23 C. for 30 min with a Pentraulik stirrer at moderate speed (around 300-1000 rpm). In case of alternatives to maltodextrin, a lower solids content of the mixture than 50% by weight of the mixture is possible. The mixtures obtained according to this general procedure are depicted in tables 2-A, 2-B and 2-C.

(20) Tables 2-A, 2-B and 2-C indicate for every mixture the employed ingredients based on their solids content on a relative weight basis, i.e. parts per hundred parts of final solids content of the mixture.

(21) TABLE-US-00002 TABLE 2-A mixture No. ingredient D1.sub.0.75-MD.sub.0.25.sup.a) D1.sub.0.50-MD.sub.0.50.sup.a) D1.sub.0.25-MD.sub.0.75.sup.a) aqueous dispersion 75 50 25 No. D1.sup.c) [%] post MD.sup.d) [%] 25 50 75 solids content 50 50 50 of mixture [%] formal content of 75 50 25 parts of aqueous dispersion No. D1 less initial MD.sup.e) [%] initial MD.sup.f) [%] formal content of 74 50 25 parts of reacted monomers of aqueous dispersion No. D1.sup.g) [%] Footnotes: .sup.a)comparative b) according to the invention .sup.c)calculated based on solids content of the aqueous dispersion .sup.d)MD admixed to the aqueous dispersion after synthesis based on solids content .sup.e)calculated assuming no initial MD is present during polymerization and based on solids content of mixture .sup.f)MD present at beginning of polymerization and based on solids content of the mixture .sup.g)based on solids content of the mixture

(22) TABLE-US-00003 TABLE 2-B mixture No. ingredient D2.sub.0.75-MD.sub.0.25.sup.b) D2.sub.0.50-MD.sub.0.50.sup.b) D2.sub.0.25-MD.sub.0.75.sup.b) aqueous 75 50 25 dispersion No. D2.sup.c) [%] post MD.sup.d) [%] 25 50 75 solids content 50 50 50 of mixture [%] formal content 58 39 19 of parts of aqueous dispersion No. D2 less initial MD.sup.e) [%] initial MD.sup.f) [%] 17 11 6 formal content 57 38 19 of parts of reacted monomers of aqueous dispersion No. D2.sup.g) [%] Footnotes: compare table 2-A

(23) TABLE-US-00004 TABLE 2-C mixture No. ingredient D3.sub.0.75-MD.sub.0.25.sup.b) D3.sub.0.50-MD.sub.0.50.sup.b) D3.sub.0.25-MD.sub.0.75.sup.b) aqueous 75 50 25 dispersion No. D3.sup.c) [%] post MD.sup.c) [%] 25 50 75 solids content 50 50 50 of the mixture [%] formal content of 58 39 19 parts of aqueous dispersion No. D3 less initial MD.sup.e) [%] initial MD.sup.f) [%] 17 11 6 formal content 56 38 19 of parts of reacted monomers of aqueous dispersion No. D3.sup.g) [%] Footnotes: compare table 2-A
Preparation of Coated Papers
Procedure a) The aqueous polymer dispersion as obtained in the synthetic procedure, the mixture of a synthesized aqueous polymer dispersion with maltodextrin or the other stated coating material is diluted with water in such a way that no streaks from the wire-wound rod are visible when the base paper (Magnostar (RTM Sappi), 70 g/m.sup.2, precoated with 6 g/m.sup.2 of a coating mass comprising based on solids parts 70 parts Hydrocarb 60 (RTM Omya, calcium carbonate), 30 parts Hydrocarb 90 (RTM Omya, calcium carbonate) and 5.5 parts Styronal D 809 (RTM BASF, a styrene-butadiene binder), the coating mass having a solids content of 68.5% by weight and being applied with a blade) is coated. The base paper is then placed on the paper underlay of the coating table in portrait format. The wire-wound rod is placed ca. 8 cm from the bottom edge of the paper. A small amount of coating colour is applied to the paper in front of the rod, and applied to the strip of the base paper by pressing the rod down gently with both hands and mowing it at a constant speed across the paper. The strip of paper is then hung up to dry in an oven and dried for 1 min at 130 C. b) After the paper has been left to cool down, 55 cm samples are taken from the uncoated upper edge of the base paper and from the coated area. Both samples are weighed and the coat weight relative to the area is calculated. If the value obtained is lower or higher than the foreseen value, different combinations of pressure, coating speed, choice of wire-wound rod and the dilution of the coating colour can be selected until the desired result is obtained when the procedure is repeated. c) The coat weight relative to area in g/m.sup.2 is calculated from the mass of the coated sample less the uncoated sample. The foreseen weight of the applied coat weight is 15 g/m.sup.2 based on solids content of the aqueous coating mass.

(24) Other employed coating materials are maltodextrin MD-Glyc a mixture of maltodextrin and glycerin in a weight ratio of 85:15 in the form of an aqueous solution with 22% solids content starch PVOH polyvinyl alcohol

(25) Maltodextrin alone only forms a brittle coating film, which crushes already at bending of the coated paper and thus destroys the coating layer. The added glycerin acts as a softening agent and allows the coated paper to be bended without forming cracks.

(26) The used maltodextrin is C*Plus 10998 (RTM Cargill, aqueous solution with a content of 50% by weight).

(27) The used starch is C*Film TCF 07311 (RTM Cargill, obtained as a powder with 8% humidity content, preparation of an aqueous solution of 30% by weight solids content by calculation via dissolving the powder at 23 C. without lumps, heating the mixture to 90 C. for around 20 minutes and cooling).

(28) The used polyvinyl alcohol is Mowiol 4-88 (RTM Kuraray Europe, an aqueous solution of 22% by weight is prepared by adding the powder to water and boiling up).

(29) Coated papers Pa-1 to Pa-17 with the applied coating mass are depicted in table 3-A.

(30) Physical Properties of Coated Papers

(31) The oxygen permeability is determined according to the test as described below.

(32) Test equipment for Oxygen Permeability

(33) The test chamber is a stainless steel permeation cell (50 cm.sup.3 volume) with an inlet for nitrogen gas, an outlet and a glass window. Oxygen is detected by the fluorescence technology OpTech-O.sub.2 (RTM MOCON). OpTech-O.sub.2 uses fluorescent chemistries such as the platinum chemistry to measure a rate of decay of the fluorescence. The rate is directly proportional to the concentration of oxygen present. A sensor, which is an adhesive label with a fluorescent colorant, is placed inside the permeation cell behind the glass window. This sensor will fluoresce or give off light in an amount that is directly proportional to the amount of oxygen in the permeation cell. This fluorescence is read by a detector (with LED light) that is placed outside the permeation cell next to the glass window. The measurement does not consume oxygen.

(34) Test Procedure for Oxygen Permeability

(35) The test chamber is a permeation cell and placed in a conditioned room with 23 C. and 50% relative humidity. The permeation cell (100 cm.sup.3 volume, round opening with an area of 100 cm.sup.2, height of around 7 cm from the bottom to the opening) is covered with the punched out paper sample with a diameter of 14 cm. The opening is accordingly closed by the paper sample, which represents a boundary surface to outside air. The permeation cell is flushed with nitrogen until the platinum-fluorescence detector indicates 0% oxygen. The nitrogen stream is stopped, the inlet and the outlet of the permeation cell are closed and the measuring program is started. Oxygen from outside air can only enter by permeation through the paper sample. The detector reads the fluorescence decay rates at the sensor inside the permeation cell, which are quantitatively influenced in case of the presence of oxygen, in regular intervals and the data are transformed in % oxygen. A paper with a poor oxygen barrier performance leads to a quick increase of oxygen in the permeation cell within a few hours, whereas a paper with good oxygen barrier performance leads to only a small or no increase of oxygen in the permeation cell. Dependent on the performance, the test lasts 12 hours or 24 hours. A program calculates the permeation rate in cm.sup.3 oxygen per square meter and per day [oxygen cm.sup.3/(m.sup.2 d)]. A low value is desired. The data given in table 3-A are the direct test values measured against air with around 20% oxygen content, i.e. without conversion to pure oxygen and without conversion to a specific permeability based on a standardized film thickness.

(36) Table 3-A shows the measured oxygen permeability of an untreated paper, i.e. Pa-0, and the coated papers No. Pa-1 to Pa-17.

(37) TABLE-US-00005 TABLE 3-A applied coating mass [dispersion No., mixture oxygen permeability paper No. No. or other coating material] [cm.sup.3 oxygen/(m.sup.2 d)] Pa-0.sup.a) .sup.a),c) >10,000 Pa-1.sup.a) D1.sup.a) >1,000 Pa-2.sup.a) D1.sub.0.75-MD.sub.0.25.sup.a) 300 Pa-3.sup.a) D1.sub.0.50-MD.sub.0.50.sup.a) >1,000 Pa-4.sup.a) D1.sub.0.25-MD.sub.0.75.sup.a) >10,000 Pa-5.sup.b) D2.sup.b) 3.0 Pa-6.sup.b) D2.sub.0.75-MD.sub.0.25.sup.b) 0.9 Pa-7.sup.b) D2.sub.0.50-MD.sub.0.50.sup.b) 0.2 Pa-8.sup.b) D2.sub.0.25-MD.sub.0.75.sup.b) 2.0 Pa-9.sup.b) D3.sup.b) 80 Pa-10.sup.b) D3.sub.0.75-MD.sub.0.25.sup.b) 20 Pa-11.sup.b) D3.sub.0.50-MD.sub.0.50.sup.b) 0.5 Pa-12.sup.b) D3.sub.0.25-MD.sub.0.75.sup.b) 60 Pa-13.sup.a) D4.sup.a) >1,000 Pa-14.sup.a) D5.sup.a) >1,000 Pa-15.sup.a) MD-Glyc.sup.a) >10,000 Pa-16.sup.a) PVOH.sup.a) >10,000 Pa-17.sup.a) starch.sup.a) >10,000 Footnotes: .sup.a)comparative .sup.b)inventive .sup.c)no coating material applied

(38) The measured results of the papers Pa-0 to Pa-17 show (a) that Pa-5 respectively Pa-9, which are both coated with an emulsion polymer polymerized in the presence of maltodextrin, provide a lower oxygen permeability than Pa-13 respectively Pa-14, which are both coated with the respective related emulsion polymer polymerized in the absence of maltodextrin; (b) that Pa-5 to Pa-12, which are coated with a coating mass containing an aqueous dispersion of an emulsion polymer polymerized in the presence of maltodextrin, provide a lower oxygen permeability than Pa-1 to Pa-4, which are coated with a coating mass containing an aqueous dispersion of an emulsion polymer polymerized in the absence of maltodextrin; (c) that Pa-6 to Pa-8, which are coated with a coating mass with additionally admixed maltodextrin, provide lower oxygen permeability than Pa-5, which is coated without additionally admixed maltodextrin; (d) that Pa-10 to Pa-12, which are coated with a coating mass with additionally admixed maltodextrin, provide lower oxygen permeability than Pa-9, which is coated without additionally admixed maltodextrin; (e) that Pa-15, Pa-16 and Pa-17, which are coated either with a mixture of maltodextrin and glycerin, with poly(vinyl alcohol) or with starch, does not provide a relevant reduction of oxygen permeability under the test conditions.