Paper and cardboard packaging with barrier coating

Abstract

Described is paper or cardboard packaging produced from mineral oil contaminated, (e.g., recycled) paper, wherein the packaging includes a barrier layer obtainable by applying an aqueous polymer dispersion comprising a copolymer obtainable by emulsion polymerization of C.sub.1-C.sub.4 alkyl (meth)acrylates, acid monomers, e.g., acrylic acid or methacrylic acid, 0-20 wt % of acrylonitrile and 0 to 10 wt % of further monomers in an aqueous medium in the presence of a carbohydrate compound, preferably in the form of a degraded starch, wherein the glass transition temperature of the copolymer is in the range from +10 to +45 C. The barrier layer may be situated on one of the surfaces of the packaging or form one of multiple layers of a multilayered packaging coating or be situated as a coating on one side of an inner bag situated within the packaging.

Claims

1. A paper or a cardboard packaging produced at least partly from mineral oil contaminated paper, wherein the packaging includes at least one barrier layer obtained by applying an aqueous polymer dispersion comprising at least one copolymer obtained by emulsion polymerization of (a) one or more principal monomers that are C.sub.1-C.sub.4 alkyl (meth)acrylates, (b) 0.1 to 5 wt % of one or more acid monomers, (c) 0-20 wt % of acrylonitrile and (d) 0 to 10 wt % of a further monomer other than the monomers (a) to (c), wherein a glass transition temperature of the copolymer is in the range from +10 to +45 C., wherein the emulsion polymerization is carried out in an aqueous medium comprising a carbohydrate compound, wherein the barrier layer comprises the carbohydrate compound, and wherein the barrier layer may be situated on one or more of the surfaces of the packaging; or the barrier layer may form at least one of multiple layers of a multilayered packaging coating.

2. The packaging of claim 1 wherein the copolymer comprises, in reacted form, at least 70 wt % of the one or more principal monomers (a).

3. The packaging of claim 1 wherein the carbohydrate compound is a degraded polysaccharide.

4. The packaging of claim 1 wherein the carbohydrate compound comprises degraded polysaccharides having an intrinsic viscosity .sub.i of less than 0.07 dl/g.

5. The packaging of claim 1 wherein the emulsion polymerization is carried out in an aqueous medium comprising 10 to 200 parts by weight of the carbohydrate compound per 100 parts by weight of monomer.

6. The packaging of claim 1 wherein the one or more principal monomers (a) are selected from the group consisting of methyl acrylate, methyl methacrylate, ethyl acrylate and n-butyl acrylate.

7. The packaging of claim 1 wherein the copolymer is obtained by emulsion polymerization of (a) 79.5 to 99.5 wt % of one or more principal monomers that are C.sub.1-C.sub.4 alkyl (meth)acrylates, (b) 0.5 to 5 wt % of one or more acid monomers selected from acrylic acid and methacrylic acid, (c) 0-20 wt % of acrylonitrile, and no further monomers other than the monomers (a) to (c).

8. The packaging of claim 1 wherein the glass transition temperature of the copolymer is in the range from +15 to +40 C.

9. The packaging of claim 1 wherein the monomer (d) is at least one selected from the group consisting of a C.sub.5-C.sub.20 alkyl (meth)acrylate, a vinyl ester of carboxylic acid comprising up to 20 carbon atoms, a vinylaromatic having up to 20 carbon atoms, an ethylenically unsaturated nitrile other than acrylonitrile, a vinyl halide, a vinyl ester of alcohol comprising 1 to 10 carbon atoms, an aliphatic hydrocarbon having 2 to 8 carbon atoms and one double bond and an aliphatic hydrocarbon having 2 to 8 carbon atoms and two double bonds.

10. The packaging of claim 1 wherein the copolymer is present in combination with up to 1 part by weight of a pigment, per 1 part by weight of copolymer.

11. The packaging of claim 1 wherein the copolymer is comprised in the aqueous polymeric dispersion in an amount of 15 to 75 wt %.

12. The packaging of claim 1 wherein the coating with the copolymer has a permeability to gaseous n-hexane of less than 50 g/m.sup.2 d at 23 C. and a coat weight of 5 to 30 g/m.sup.2 on paper.

13. The packaging of claim 1 wherein the mineral oil contamination comprises a volatile paraffin, a volatile naphthene and/or a volatile aromatic hydrocarbon.

14. The packaging of claim 1 wherein the barrier layer is from 2 to 30 m in thickness.

15. A process for producing the packaging of claim 1, the process comprising: applying the aqueous polymeric dispersion to a packaging substrate or to a surface of an inner bag; and drying the aqueous polymeric dispersion.

16. The process of claim 15 wherein the aqueous polymeric dispersion is applied to the packaging substrate by a printing process.

17. The process of claim 15 wherein the barrier layer is a barrier against volatile, hydrophobic organic compounds.

18. The process of claim 17 wherein the volatile, hydrophobic organic compounds have a solubility of less than 1 wt % in water at 20 C. and a molecular weight of less than 500.

19. The process of claim 17 wherein the barrier layer is an aroma barrier layer or a barrier layer against volatile mineral oil constituents.

Description

EXAMPLES

(1) Unless the context suggests otherwise, percentages are by weight. A reported content relates to the content in aqueous solution or dispersion.

(2) The following input materials were used: MMA methyl methacrylate MA methyl acrylate AS acrylic acid S styrene nBA n-butyl acrylate AN acrylonitrile C Dry MD 01915: maltodextrin (Cargill) C Sweet 01403: glucose syrup (Cargill) C Plus 10998: maltodextrin, liquid (Cargill) Acronal S 505 binder for paper and paperboard coating, styrene/acrylate/acrylonitrile copolymer, about 50% strength Finntalc talc powder, platelet-shaped pigment HG90 Hydragloss 90 calcium carbonate pigment

Examples 1-3

Preparation of Polymer Dispersions (Comparative Dispersions)

(3) Purge a reactor with nitrogen and add 450.0 g of demineralized water and 3.0 g of emulsifier (Disponil LDBS 20, 20% in water) as initial charge. The mixture in the initial charge is heated to 70-90 C. Then, 21.43 g of sodium peroxodisulfate (7% strength) are added before stirring for 50 minutes. Meter the emulsion feed consisting of 240.0 g of water, 26.67 g of emulsifier (Dowfax 2A1, 45% in water) and 600.0 g of monomer mixture as per table 1 into the reactor over 2 hours. After the emulsion feed has ended allow the system to polymerize for 45 min. The reactor is then cooled down to room temperature. Solids content: about 45%

Examples 4-7

Preparation of Carbohydrate-Stabilized Polymer Dispersions

(4) Purge a reactor with nitrogen and add 427.1 g of demineralized water and C Dry MD 01915 (94.7% strength) in the amounts of table 1. The mixture in the initial charge is heated to 86 C. Then, 3.2 g of sodium peroxodisulfate (7% strength) are added before stirring for 5 minutes. Meter the emulsion feed consisting of 180.0 g of water, 20.0 g of emulsifier (Dowfax 2A1, 45% strength) and 450.0 g of monomer mixture as per table 1 into the reactor over 2 hours. Concurrently with the emulsion feed the initiator feed is started (12.9 g of sodium peroxodisulfate, 7% strength) and likewise metered in over 2 hours. After the emulsion feed has ended allow the system to polymerize for 45 min. The reactor is then cooled down to room temperature. Solids content: as per table 1.

Example 8

Preparation of Polymer Dispersions Stabilized with Glucose Syrup

(5) Purge a reactor with nitrogen and add 351.8 g of demineralized water and 312.5 g of C Sweet 01403 glucose syrup (72% strength). The mixture in the initial charge is heated to 86 C. Then, 3.2 g of sodium peroxodisulfate (7% strength) are added before stirring for 5 minutes. Meter the emulsion feed consisting of 180.0 g of water, 20.0 g of emulsifier (Dowfax 2A1, 45% strength) and 450.0 g of monomer mixture as per table 1 into the reactor over 2 hours. Concurrently with the emulsion feed the initiator feed is started (12.9 g of sodium peroxodisulfate, 7% strength) and likewise metered in over 2 hours. After the emulsion feed has ended allow the system to polymerize for 45 min. The reactor is then cooled down to room temperature. Solids content: as per table 1.

(6) TABLE-US-00001 TABLE 1 Copolymer compositions, quantities in wt % Degraded Solids Exam- starch content ples Monomers [pphm] .sup.1) Tg (%) 1 55 MA/44 MMA/1 AS ca 50 C. 45 2 14 S/69 nBA/14 AN/3 AS ca 5 C. 45 3 55 EA, 44 MMA, 1 AS 30 C. 45 4 55 EA, 44 MMA, 1 AS 30 30 C. 47 5 55 EA, 44 MMA, 1 AS 50 30 C. 50 6 55 EA, 44 MMA, 1 AS 75 30 C. 54 7 55 EA, 44 MMA, 1 AS 100 30 C. 57 8 55 EA, 44 MMA, 1 AS 50 30 C. 50 .sup.1) weight parts per hundred weight parts of monomers

Examples 9-14

Preparation of Carbohydrate-Stabilized Polymer Dispersions

(7) Purge a reactor with nitrogen and add demineralized water and C Plus 10998 maltodextrin (94.7% strength) in the amounts of table 2. The mixture in the initial charge is heated to 86 C. Then, 3.2 g of sodium peroxodisulfate (7% strength) are added before stirring for 5 minutes. Meter the emulsion feed consisting of 180.0 g of water, 20.0 g of emulsifier (Dowfax 2A1, 45% strength) and 450.0 g of monomer mixture (4.5 g of acrylic acid, 198.0 g of methyl methacrylate and 247.5 g of ethyl acrylate) into the reactor over 2 hours. Concurrently with the emulsion feed the initiator feed is started (12.9 g of sodium peroxodisulfate, 7% strength) and likewise metered in over 2 hours. After the emulsion feed has ended allow the system to polymerize for 45 min. The reactor is then cooled down to room temperature.

(8) TABLE-US-00002 TABLE 2 Copolymer compositions/starch, quantities in wt % Degraded Water quantity in initial Solids Example starch [pphm] .sup.1) charge [g] content (%) 9 30 180 50 10 50 180 50 11 75 180 51 12 100 180 51 13 150 158 51 14 200 135 51 .sup.1) weight parts per hundred weight parts of monomers

Example 15

Comparator

(9) Like Example 3 except that C Plus 10998 maltodextrin (30 pphm) is admixed after the polymerization.

Example 16

Comparator

(10) C Plus 10998 liquid maltodextrin

(11) Coated papers were produced by a manual coater or a lab coater being used to apply a test composition to calendered standard paper at 25-28 g/m.sup.2 coat weight as sum of two coats and drying.

(12) Barrier Test Against Gaseous Mineral Oil Constituents

(13) 9 ml of hexane are poured into a vessel containing a sponge and closed with a lid which has an opening and a sealing ring (internal diameter 63 mm). The opening is tightly closed with the barrier material to be tested, while the barrier material does not come into contact with the hexane-drenched sponge. The weight decrease of the vessel is measured. The weight decrease is a measure of the hexane exiting through the barrier material via the gas phase, and thus is a measure of the barrier performance against gaseous mineral oil constituents. The weight decrease in grams is converted to 1 m.sup.2 of paper area and then reported as g/m.sup.2 d.

(14) Test for Shear Stability

(15) 100 g of test composition in a 1 liter square bottle are stirred with a Pentraulik stirrer having a jagged stirring disk at a speed of 8000 rpm for 5 minutes. After shearing, the test composition is filtered through a 125 sieve, dried at 70 C. for 2 hours and the filter residue is arithmetically projected on 1 kg of test composition and assessed as a measure of shear stability. The less filter residue is obtained, the less coagulum has formed in the course of shearing and the greater the shear stability is.

(16) Pore Test

(17) A test oil with blue dye (terpentine oil or oleic acid with 2% Sudan Blue) is rubbed with a ball of absorbent cotton over a substrate surface coated with a test composition and immediately removed again with a clean area of the ball of absorbent cotton. Pores and uncoated places discolor at once, the oil on the intact coating is removable without causing any coloration. The test area is assessed by visual inspection. The less the discoloration, the greater the absence of pores in the coated surface.

(18) The test results are summarized in tables 3 and 4.

(19) TABLE-US-00003 TABLE 3 Test results of Examples 1-7 Hexane Degraded Shear stability permeation Example starch [pphm] .sup.1) in % coagulum [g/m.sup.2 d] Pore test 1 slightly unstable 200-220 poor, Ca. 0.3% many pores 2 stable 260-290 very good, <0.01% no pores 3 unstable 1-5 good Ca. 3.6% Few pores 4 30 stable 1-5 very good, <0.01% no pores 5 50 stable 1-5 very good, <0.01% no pores 6 75 stable 1-5 very good, <0.01% no pores 7 100 stable 1-5 very good, <0.01% no pores .sup.1) weight parts per hundred weight parts of monomers

(20) The results show that Examples 4 to 7 according to the invention evince the best combination of advantageous properties in respect of shear stability, hexane permeation and pore formation.

(21) TABLE-US-00004 TABLE 4 Test results of Examples 9-16 Degraded Polymer Hexane starch dispersion permeation Example [pphm] .sup.1) shear stable [g/m.sup.2 d] Film property 3 0 no 1-5 good (blocking) 9 30 yes 1-5 good (little blocking) 10 50 yes 1-5 good (little blocking) 11 75 yes 1-5 good (little blocking) 12 100 yes 25 good (little blocking) 13 150 yes 45 good (little blocking) 14 200 yes 45-50 poor, brittle 15 30 (as no 1-5 good blend) 16 n.a. n.a. 1500 .sup.1) weight parts per hundred weight parts of monomers

(22) The results show that the optimum amount of carbohydrate is in the range from 30 to 150 pphm and that shear stability benefits when the carbohydrates are already present during the polymerization.

Examples 17-21

Pigmented Paper Coating Slips

(23) Paper coating slips having the compositions as per table 5 were produced. The coating slips were adjusted with a thickener (Sterocoll HT) to viscosities of about 1500-2000 mPas (Brookfield 100/min) and with NaOH to a pH of about 8.2 to 8.3. The results of barrier tests are summarized in table 5.

(24) TABLE-US-00005 TABLE 5 Compositions of Examples 17-21, quantities in parts by weight based on solids content Polymer Hexane dispersion Acronal S permeation Example of Example 4 505 Pigment [g/m.sup.2 d] 17 100 4 18 80 20 Finntalc 6 19 50 50 HG90 700 (comparator) 20 37.5 12.5 50 HG90 70 21 50 50 HG90 40