AQUEOUS DISPERSION FOR IMPROVING BARRIER PROPERTIES

Abstract

The invention relates to a fiber preparation treated with an aqueous polyolefin dispersion having a pH value from 7.5-9.4 containing a. from 50 to 100 wt. % of an aqueous dispersion A comprising the following ingredients: i. from 41 to 98 wt. % of A1, a copolymer of ethylene and (meth)acrylic acid having a content of (meth)acrylic based groups of at least 14 wt. % based on the total weight of the copolymer or a mixture of different copolymers of ethylene and (meth)acrylic acid each having a content of (meth)acrylic based groups of at least 14 wt. % based on the total weight of the copolymer, ii. from 1 to 59 wt. % of A2, another olefinic structure units containing hydrocarbon polymer, or a mixture of other olefinic structure units containing hydrocarbonpolymers, and iii. from 0-35 wt. % of additive different from A1 and A2, b. from 0 to 50 wt. % of a compound B, where compound B is a material dispersible or soluble in water and different from any of the ingredients of dispersion A wherein the wt. % of A and B is based on the solid content of the whole aqueous polyolefin dispersion, the wt. % of the ingredients of dispersion A is based on the solid content of dispersion A, the sum of the wt. % of ingredients i to iii of dispersion A is 100%.

Claims

1. Fiber preparation treated with an aqueous polyolefin dispersion having a pH value from 7.5-9.4, the aqueous polyolefin dispersion containing; a. from 50 to 100 wt. % of an aqueous dispersion A comprising the following ingredients: i. from 41 to 98 wt. % of A1, A1 being a copolymer of ethylene and (meth)acrylic acid having a content of (meth)acrylic based groups of at least 14 wt. % based on the total weight of the copolymer or a mixture of different copolymers of ethylene and (meth)acrylic acid each having a content of (meth)acrylic based groups of at least 14 wt. % based on the total weight of the copolymer, ii. from 1 to 59 wt. % of A2, A2 being a hydrocarbon polymer containing olefinic structure units, or a mixture of hydrocarbon polymers containing other olefinic structure units, and iii. from 0-35 wt. % of additive different from A1 and A2, b. from 0 to 50 wt. % of a compound B, where compound B is a material dispersible or soluble in water and different from any of the ingredients of dispersion A wherein the wt. % of A and B is based on the solid content of the whole aqueous polyolefin dispersion, the wt. % of the ingredients of dispersion A is based on the solid content of dispersion A, the sum of the wt. % of ingredients i to iii of dispersion A is 100%.

2. The fiber preparation according to claim 1 in which the aqueous dispersion A comprises the following ingredients: i. from 51 to 95 wt. % of A1, ii. from 5 to 49 wt. % of A2, and iii. from 0-35 wt. % of additive different from A1 and A2.

3. The fiber preparation according to claim 1, wherein at least 60 wt. % of A1 have a content of (meth)acrylic based groups of at least 19 wt. % based on the total weight of the copolymer.

4. The fiber preparation according to claim 1, wherein at least 60 wt. % of A2 are provided by copolymers containing ethylene structural units.

5. The fiber preparation according to claim 1, where at least 60 wt. % of A2 is selected from polyolefines with ethylene and 1-octene structural units and polyolefines with ethylene and propylene structural units.

6. The fiber preparation according to claim 1 wherein the aqueous polyolefin dispersion contains, as an ingredient of B, less than 5 wt. % of PEG, based on the solid content of the whole aqueous dispersion.

7. The fiber preparation according to claim 1 wherein the aqueous polyolefin dispersion contains dispersed hybrid particles containing A1 and A2.

8. The fiber preparation according to claim 1, wherein the whole aqueous polyolefin dispersion has a solid content of 10-60 wt. %.

9. A solid article formed from the fiber preparation according to claim 1.

10. The fiber preparation according to claim 1 in which at least 80 wt. % of the fibers are cellulose fibers of a paper or a carton article.

11. A product made from a fiber preparation, wherein the product is made by a process comprising applying an aqueous polyolefin dispersion as a binder and/or as a coating to fibers and thereafter removing the water of the aqueous polyolefin dispersion, and the aqueous polyolefin dispersion has a pH value from 7.5-9.4 and contains: a. from 50 to 100 wt. % of an aqueous dispersion A comprising the following ingredients: i. from 41 to 98 wt. % of A1, A1 being a copolymer of ethylene and (meth)acrylic acid having a content of (meth)acrylic based groups of at least 14 wt. % based on the total weight of the copolymer or a mixture of different copolymers of ethylene and (meth)acrylic acid each having a content of (meth)acrylic based groups of at least 14 wt. % based on the total weight of the copolymer, ii. from 1 to 59 wt. % of A2, A2 being a hydrocarbon polymer containing olefinic structure units, or a mixture of hydrocarbon polymers containing other olefinic structure units, and iii. from 0-35 wt. % of additive different from A1 and A2, b. from 0 to 50 wt. % of a compound B, where compound B is a material dispersible or soluble in water and different from any of the ingredients of dispersion A wherein the wt. % of A and B is based on the solid content of the whole aqueous polyolefin dispersion, the wt. % of the ingredients of dispersion A is based on the solid content of dispersion A, the sum of the wt. % of ingredients i to iii of dispersion A is 100%.

12. The product according to claim 11, wherein the water of the aqueous polyolefin dispersion is removed by drying.

13. The product according to claim 11 comprising paper or carton.

14. A process comprising applying an aqueous polyolefin dispersion as a binder and/or as a coating composition to a fiber-based substrate, the aqueous polyolefin dispersion having a pH value from 7.5-9.4 and containing: a. from 50 to 100 wt. % of an aqueous dispersion A comprising the following ingredients: i. from 41 to 98 wt. % of A1, A1 being a copolymer of ethylene and (meth)acrylic acid having a content of (meth)acrylic based groups of at least 14 wt. % based on the total weight of the copolymer or a mixture of different copolymers of ethylene and (meth)acrylic acid each having a content of (meth)acrylic based groups of at least 14 wt. % based on the total weight of the copolymer, ii. from 1 to 59 wt. % of A2, A2 being a hydrocarbon polymer containing olefinic structure units, or a mixture of hydrocarbon polymers containing other olefinic structure units, and iii. from 0-35 wt. % of additive different from A1 and A2, b. from 0 to 50 wt. % of a compound B, where compound B is a material dispersible or soluble in water and different from any of the ingredients of dispersion A wherein the wt. % of A and B is based on the solid content of the whole aqueous polyolefin dispersion, the wt. % of the ingredients of dispersion A is based on the solid content of dispersion A, the sum of the wt. % of ingredients i to iii of dispersion A is 100%.

15. The process according to claim 14 imparting grease-resistance, water-resistance, and/or water-vapor-resistance to the fiber-based substrate.

16. The fiber preparation according to claim 1 wherein the aqueous polyolefin dispersion contains, as an ingredient of B, less than 4 wt. % of PEG, based on the solid content of the whole aqueous dispersion.

17. A sheet formed from the fiber preparation according to claim 1.

18. The product according to claim 12, wherein the water of the aqueous polyolefin dispersion is removed by drying at temperatures above 75 C.

19. The process according to claim 14, wherein the fiber-based substrate comprises paper or carton.

Description

DEFINITIONS

[0061] Within the content of this description the following definitions are used [0062] (meth)acrylic means acrylic and/or methacrylic; [0063] A homogeneous polymer containing compound is a compound that shows no optical defects when cast into a film with a thickness in the range of 1 to 2 mm.

[0064] Measurement Methods

[0065] The following measurement methods were used to characterize the individual components and the obtained products mentioned in this description:

[0066] Melt Flow Index (MFI) was determined in accordance with ISO 1133 in a Zwick/Roell extrusion plastometer. The MFI is measured at 190 C. at a load of 2.16 kg. For each measurement, 6 gr of material was heated for 5 minutes inside the measurement cylinder prior to the start of a measurement. The MFI is the average value for three portions.

[0067] The melting temperature of a component was determined using differential scanning calorimetry according to ISO 11357. For the measurement a Mettler Toledo DSC Star System was used. The measurements were carried out under nitrogen in a temperature range of 60 to 200 C. and a heating rate of 10 K/min.

[0068] The solid content of a dispersion was determined in a Moisture Analyzer HC103 from Mettler-Toledo GmbH. The measurements are done at 130 C. for 30 minutes, then the weight is constant.

[0069] The viscosity of a dispersion was measured using a Thermo Fisher Scientific HAAKE Rotation Rheometer RV1 at 20 C. using a double-cone DC60/2 Ti L configuration in combination with a MPC/DC60 geometry. The measurements were performed during 120 s at shear rates between 0 and 120 s.sup.1. The viscosity values at shear rate 114 s.sup.1 are evaluated.

[0070] The particle size was measured using a Microtrac S3500 laser diffraction system, using a wet dispersion module. For each measurement, 1 ml of a dispersion was added to the 1 l dispersing module, where the dispersing module was filled with water with a pH in the range of 7-10. The further settings are cell size 2 mm, ultra sound duration 60 s. The specific value is 50-value in m, which corresponds to the average particle size.

[0071] The pH value was determined by a pH meter PCE-228 of PCE Instruments accorded to DIN ISO 8975 of the undiluted dispersion.

[0072] The preparation of the samples for the different barrier tests contains several steps: The dispersion is applied to the substrate with a wire bar and then it is dried at 120 C. for 120 seconds in an oven.

[0073] The coating weight of the of the applied dispersion layer was determined gravimetrically. For this purpose, circles with a defined area are cut out from the uncoated substrate using circular cutter and weighed with an analytical balance. Then circles with the same area are cut out from the coated substrate and weighted, too. The difference is standardized and describes the load quantity in grams per square meter.

[0074] The water vapour permeability is measured accorded to ISO 15106-2 and ASTM F1249 with the C390H Water Vapor Transmission Rate Test System from Labthink. The measurements were done at two different conditions (23 C. and 50% rh and 38 C. and 90% rh). The coated side of the substrates was faced to the water vapor side of the measuring device.

[0075] The water absorption/resistance was measured using a COBB Tester accorded to DIN EN ISO 535 (Paper and boardDetermination of water absorptiveness). For this purpose, the sample is cut out and weighted with an analytical balance. Afterwards, the sample is exposed to water in the COBB tester for a certain time and then couched between two blotting papers to remove the excess water from the sample surface. Then the wet sample is weighted, too and the difference is standardized and describes the water absorption in grams per square meter. The time can vary between 60 seconds (COBB 60) and 1800 seconds (COBB 1800).

[0076] The oil/grease resistance was also determined using the COBB tester in accordance with test procedures of DIN EN ISO 535. The sample is cut out and weighted with an analytical balance. Afterwards, the sample is exposed to oil in the COBB tester for a certain time and then couched between two blotting papers to remove the excess oil from the sample surface. Then the oily sample is weighted, too and the difference is standardized and describes the oil absorption in grams per square meter.

[0077] According to a preferred embodiment the fiber preparation according to the present invention forms a solid article, which is preferably provided by sheet. Typically, at least 80 wt. % of the fibers are provided by cellulose fibers so that the fiber preparation is provided by a paper or a carton article.

[0078] The relevant fibers might be selected from cellulose and lignocellulose fibers and combinations thereof which are obtainable from annual or perennial plants, in particular from wood.

[0079] Also, synthetic fibers, especially thermoplastic synthetic fibers might be usede.g. on the basis of: glycolic acid polymer, polyolefin, polyethylene terephthalate, polyester, polyamide, polylactide, polyvinyl alcohol or polybutylene succinate. Additionally, reinforcement fibers might be used, e.g. selected from polymer fibers, mineral fibers, non-wood natural fibers and glass-fibers and combinations thereof. The fibers might be biodegradable and/or recyclable.

[0080] The corresponding fiber made products might be carrier bags and sacks, shopping bags, refuse sacks, wrappings of goods, industrial packages, medical packages, coverts, envelopes and bags for replacing plastic bags.

[0081] The present invention also relates to a product on the basis of a fiber preparation as described above, wherein the treating with the aqueous polyolefin dispersion is performed by applying the aqueous polyolefin dispersion as a binder and/or as a coating of fibers and thereafter the water of the aqueous polyolefin dispersion is removed.

[0082] Typically, the water of the aqueous polyolefin dispersion is removed by drying, preferably at temperatures above 75 C. The relevant (drying) temperature should be generally sufficient high in order to allow a film-building of the contained polymer. Said film-building might be important regarding barrier properties.

[0083] Said product is typically provided by paper or by carton. The treatment of the relevant paper substrate with the aqueous polymer dispersion might be performed by coating with a squeegee/wire bar, flexoroll or by spraying.

[0084] Additionally, the present invention provides the use of an aqueous polyolefin dispersion as described above as a binder and/or as a coating composition for a fiber based substrate, preferably for paper or carton.

[0085] The intention of said use is preferably to improve the barrier properties concerning grease-resistance, water-resistance and/or water-vapor-resistance.

[0086] Especially these barrier properties are important for the quality of paper packaging materials.

EXAMPLES

[0087] Various aqueous dispersions were prepared using the following procedure: [0088] In a first step a compound was prepared by mixing and kneading the individual ingredients in a Leistritz ZSE 18 Maxx twin screw extruder at a temperature in the range of 80-150 C. (temperature was selected based on the ingredients), where different temperature zones were created inside the extruder. The pressure inside the extruder was 35 bar maximum. [0089] In a next step the extruded compound was fed into a Bchi 2 l Pressure reactor, equipped with a dissolver mixer operating at speeds between 100-1000 rpm. The dispersion was prepared at elevated temperature in the range of 90-150 C. at sometimes elevated pressure (additional pressure in the range of 0-100 bar). After the formation of a homogeneous dispersion the cooling of the mixture is essential. The cooling has to be performed as quickly as possible at crystallization temperature of the polymers until maximum temperature of 40 C.

[0090] The ingredients (in parts by weight, based on solid content) and conditions for each example are given in Table 1 below.

TABLE-US-00001 TABLE 1 Example 0* 1 2 3 4 5* EAA #3 100 60 60 60 60 100 POE #8 40 POP #11 40 20 EPM #82 40 20 Laponite 1.65 3.3 3.3 4 4 Solid content (%) 28 30.5 31 31 26 26 Base NH.sub.3 NH.sub.3 NH.sub.3 NH.sub.3 NH.sub.3 NH.sub.3 pH value 9.0 9.4 8.9 8.9 8.9 8.5 Viscosity [mPa .Math. s] 104 144 512 540 200 817 Water resistance 11.8 1.64 3.71 8.5 5.99 11.0 Cobb-water 1800 [g/m.sup.2] WVTR 23 C., 50% rh 63 58 32 30 55 73 [g/m2*d] WVTR 38 C., 90% rh 480 422 209 224 217 304 [g/m2*d] EAA #3: dispersible polymer which is an ethylene acrylic acid copolymer (20 wt % acrylic acid), POE #8: polyolefin plastomer containing Ethylen and 1-Octen, POP #11: propylene-based elastomer with an ethylene content of 15 wt %, EPM #82: ethylene propylene copolymer (28 wt % propylene), Laponite: synthetic layered phosphate modified silicate with a specific surface area of 330 m.sup.2/g.