EASY TO DISPERSE CALCIUM CARBONATE TO IMPROVE HOT TACK STRENGTH

Abstract

The present invention relates to a process for producing an extrusion-coated material, an extrusion-coated material produced by the process, an article comprising the extrusion-coated material as well as the use of the extrusion-coated material in a lamination process.

Claims

1. A process for producing an extrusion-coated material comprising the following steps: a) providing at least one filler material in powder form, b) providing at least one polymer binder, c) providing at least one thermoplastic polymer, d) simultaneously or subsequently feeding the at least one filler material of step a) and the at least one polymer binder of step b) into a high speed mixer unit, e) mixing the at least one filler material of step a) and the at least one polymer binder of step b) in the high speed mixer unit to obtain a compacted material, f) reducing the temperature of the compacted material obtained in step d) below the melting point or glass transition temperature of the at least one polymer binder, g) combining the compacted material obtained in step f) and the at least one thermoplastic polymer of step c) to obtain a filled thermoplastic polymer, h) extrusion coating the filled thermoplastic polymer obtained in step g) on at least a portion of the surface of a substrate.

2. The process of claim 1, wherein the at least one filler material of step a) comprises a calcium carbonate-comprising filler material.

3. The process of claim 1, wherein the at least one filler material of step a) is a calcium carbonate-comprising filler material being selected from the group consisting of natural ground calcium carbonate, precipitated calcium carbonate, surface-modified calcium carbonate, and mixtures thereof, and preferably natural ground calcium carbonate.

4. The process of claim 1, wherein the at least one filler material of step a) has a weight median particle size d.sub.50 from 0.05 to 10 m, preferably from 0.1 to 7 m, more preferably from 0.25 to 5 m, and most preferably from 0.5 to 4 m.

5. The process of claim 1, wherein the at least one filler material of step a) is at least one surface treated filler material comprising a treatment layer on at least a part of the surface of the filler material, wherein the treatment layer comprises i) at least one mono-substituted succinic anhydride and/or at least one mono-substituted succinic acid and/or salty reaction products thereof, and/or ii) a phosphoric acid ester or blend of one or more phosphoric acid mono-ester and salty reaction products thereof and/or one or more phosphoric acid di-ester and salty reaction products thereof, and/or iii) at least one saturated aliphatic linear or branched carboxylic acid, and/or iv) at least one polydialkylsiloxane, and/or mixtures of the materials according to i) to iv).

6. The process of claim 5, wherein the at least one mono-substituted succinic anhydride consists of succinic anhydride mono-substituted with a group selected from a linear, branched, aliphatic and cyclic group having a total amount of carbon atoms from C2 to C30, preferably from C3 to C25, and most preferably from C4 to C20 in the substituent, and/or the one or more phosphoric acid mono-ester consisting of an o-phosphoric acid molecule mono-esterified with one alcohol molecule selected from unsaturated or saturated, branched or linear, aliphatic or aromatic alcohols having a total amount of carbon atoms from C6 to C30, preferably from C8 to C22, more preferably from C8 to C20, and most preferably from C8 to C18 in the alcohol substituent, and/or the one or more phosphoric acid di-ester consisting of an o-phosphoric acid molecule di-esterified with two alcohol molecules selected from the same or different, unsaturated or saturated, branched or linear, aliphatic or aromatic fatty alcohols having a total amount of carbon atoms from C6 to C30, preferably from C8 to C22, more preferably from C8 to C20, and most preferably from C8 to C18 in the alcohol substituent, and/or the saturated aliphatic linear or branched carboxylic acid is octanoic acid or stearic acid.

7. The process of claim 5, wherein the at least one surface-treated filler material comprises the treatment layer in an amount of at least 0.1 wt.-%, preferably in an amount from 0.1 to 3 wt.-%, based on the total dry weight of the at least one filler material.

8. The process of claim 1, wherein the at least one filler material is added in step d) in an amount from 50 to 99 wt.-%, preferably from 60 to 98 wt.-%, more preferably from 80 to 92 wt.-%, and most preferably from 87 to 90 wt.-%, based on the total weight of the compacted material.

9. The process of claim 1, wherein the at least one polymer binder of step b) has a rotational viscosity from 100 to 400 000 mPa.Math.s, preferably from 1 000 to 100 000 mPa.Math.s, and more preferably from 5 000 to 50 000 mPa.Math.s, at 190 C., by using a rotational viscosimeter.

10. The process of claim 1, wherein the at least one polymer binder of step b) is selected from the group consisting of polyolefins, ethylene copolymers, e.g. ethylene-1-hexene copolymers or ethylene-1-octene copolymers, metallocene based polypropylenes, polypropylene homo- or co-polymers, preferably amorphous polypropylene homopolymers, and/or mixtures thereof.

11. The process of claim 1, wherein the at least one thermoplastic polymer of step c) is selected from homopolymers and/or copolymers of polyolefins, polyamides, polystyrenes, polyacrylates, polyvinyls, polyurethanes, halogen-containing polymers, polyesters, polycarbonates and/or mixtures thereof.

12. The process of claim 1, wherein the substrate of step h) is selected from a paper, a paperboard, foil, preferably an aluminium-foil or a metallized foil, a nonwoven fabric, a polymeric film, preferably a BOPP-film, a PET-film, PBT-film or a nylon-film, and combinations thereof.

13. The process of claim 1, wherein the compacted material is added in step g) in an amount from 1 to 80 wt.-%, preferably from 3 to 40 wt.-% and, more preferably from 5 to 30 wt.-% and most preferably from 10 to 20 wt.-% based on the total weight of the filled thermoplastic polymer.

14. Extrusion-coated material produced by a process according to claim 1.

15. An article comprising an extrusion-coated material according to claim 14, wherein the article is selected from the group consisting of composite cans, cups, bricks and pouches, ream wrappings, multi-wall bags, liners for cartons, corrugated shipping containers, fibre drums, vacuum-forming materials for blister packaging, book or booklet covers, meat wraps, cheese wraps, packaging of confectionery and cigarettes, display materials, stickers, seals, graphic applications, protection of drugs, protection of cosmetics and envelopes.

16. Use of an extrusion-coated material according to claim 14 in a lamination process.

Description

EXAMPLES

[0328] 1 Measurement Methods

[0329] In the following the measurement methods implemented in the examples are described.

[0330] Ash Content

[0331] The ash content in wt.-% of a compacted material sample or a filled polymer, based on the total weight of the sample, was determined by incineration of a sample in an incineration crucible which was put into an incineration furnace at 570 C. for 2 hours. The ash content was measured as the total amount of remaining inorganic residues.

[0332] Hot Tack Measurements

[0333] The hot tack measurements have been carried out according to ASTM F1921 method B on a Hot Tack Tester model 4000 (J&B, Belgium) using the Hot-Tack Software Hot Tack 32-4000 v0.9, using the following conditions: pressure 1 000 N/mm.sup.2, seal time=0.5 s, cool time=0.2 s, peel speed=100 m/s, width=25 mm, size of films 25 mm300 mm.

[0334] Peel Force

[0335] The adhesion force between the extrusion coated polymer layer and the substrate is measured in a peel test using Zwick 180 equipment. In the test, the sealing layer is first manually separated from the base substrate by scratching the polymer layer off the substrate. Substrate and polymer layer are then fixed in the sample holder and peeled off with a constant speed at an angle of 180. The test samples had width and length of 15 and 130 mm, respectively. The speed of peeling was 200 mm/min. The adhesion test samples were drawn from the middle of the laminate (cross-direction) to avoid any neck-in influence on the coating weight stability. The peel force is measured as the average of the mean force from tests on three samples. The samples have been stored for 48 hours to 76 hours prior testing.

[0336] Compacted Material

[0337] 2.1 Starting Materials

[0338] The following starting materials have been used for the preparation of the compacted material: [0339] Filler I: Calcium carbonate (ash content=87.5 wt.-%, d.sub.98=15 m, d.sub.50=2.6 m, 0.5 surfaced coated with fatty acid, commercially available from Omya International AG, Switzerland) [0340] Filler II: Titanium dioxide rutile type pigment from chloride process grade Kronos 2220 commercially available from Kronos B.V, the Netherlands [0341] Filler III: Calcium oxide, oil damped Caloxol CP2-HU, commercially available from Omya International AG, Switzerland [0342] Binder A: Blend of 70 wt.-% ethylene-1-octene-copolymer (Affinity GA 1900), density (ASTM D792)=0.87 g/cm.sup.3 according to technical data sheet, rotational viscosity=8 500 mPa.Math.s at 190 C., commercially available from The Dow Chemical Company, USA and 30 wt.-% metallocene based polypropylene wax (Licocene PP-1302), density (23 C.; ISO 1183)=0.87 g/cm.sup.3, according to technical data sheet, rotational viscosity=130 mPa.Math.s at 190 C., commercially available from Clariant International Ltd., Switzerland. [0343] Binder B: vis-broken polypropylene homopolymer Borstar HL 520 FB,density (ASTM D792)=0.905 g/cm.sup.3 according to technical data sheet, rotational viscosity=20 000 mPa.Math.s at 190 C., commercially available from BorealisAG, Austria

[0344] 2.2 Preparation of the Compacted Material

[0345] The compacted material has been manufactured by using a horizontal Ring-Layer-Mixer/Pelletizer, namely Amixon RMG 30 with a process length of 1 200 mm, and a diameter of 230 mm, equipped with 3 feeding ports in sequence, and 1 out-let port. The cylinder is fitted with a heating/cooling double wall. Compacting is obtained by a rotating, cylindrical, pin-fitted screw. The filler has been preheated to 110 C., and fed gravimetrically into the first feed port at the rate of 22.6 kg/h. The binder has been injected in liquid state at a temperature of 230 C. through feeding port 2 at the required rate (kg/h) related to component A at 2.4 kg/h (weight ratio filler:binder=88:12). Compacting is carried out in the Ring-Layer-Mixer/Pelletizer at 180 C. and a screw speed of 800 rpm. The product leaves the Mixer/Pelletizer through the outlet port, is transferred by gravity into a second Ring-Layer-Mixer/Pelletizer for further compacting and cooling, operated at a temperature of 140 C. and a screw speed of 400 rpm. Both units were of identical size and dimensions. The resulting compacted material leaves the unit through the outlet port, and is free of dust and free flowing.

TABLE-US-00001 TABLE 1 Compositions and properties of prepared compacted materials CM1 to CM4 (wt.-% is based on total weight of the compacted material). CM1 CM2 CM3 CM4 Filler I [wt.-%] 88.0 87.0 88.0 Filler II [wt.-%] 87.0 Filler III [wt.-%] 1.0 Binder A [wt.-%] 12.0 12.0 13.0 Binder B [wt.-%] 12 Ash content [wt.-%] 87.5 87.5 87.5 86

[0346] 3 Extrusion Coating

[0347] 3.1 Starting Materials

[0348] 3.1.1 Polymer

[0349] Polymer 1: Polyethylene, DOW LD-PE PG 7004 (commercially available from The Dow Chemical Company, Horgen)

[0350] Polymer 2: Polyethylene, LDPE LA PG 0710 (commercially available from Total Petrochemicals, Belgium), melt flow rate (190 C./2.16kg) 7.5 g/10 min.), density (ASTM D792)=0.918 g/cm.sup.3

[0351] 3.1.2 Fillers [0352] A) Masterbatch pellets comprising calcium carbonate and polyethylene in a weight ratio of 75:25 (ash content=75 wt.-%, calcium carbonate d.sub.98=15 m, d.sub.50=2.6 m, commercially available from Omya International AG, Switzerland); [0353] B) Masterbatch pellets comprising 88 parts by weight calcium carbonate and 12 parts by weight of a blend of (80 wt.-% ethylene-1-octene-copolymer (Affinity GA 1900) and 20 wt.-% propylene-ethylene-copolymer wax (Licocene PP-1302)) and 17 parts by weight polyethylene (ash content=75 wt.-%, calcium carbonate d.sub.98=15 m, d.sub.50=2.6 m, commercially available from Omya International AG, Switzerland). [0354] C) Compacted Material (CM1 to CM4) as described under point 2.

[0355] 3.1.3 Base Paper

[0356] Uncoated wood-free, Ziegler Z-Offset 80 g/m.sup.2 (Ziegler Papier AG, Switzerland)

[0357] 3.2 Preparation of Filled Polymer for Extrusion Coating

[0358] Formulations were preblended in a rotating drum mixer and subsequently filled in the extruder hopper of the extrusion coating line.

TABLE-US-00002 TABLE 2 Compositions and properties of prepared filled polymers (FP1 to FP5, wt.-% is based on total weight of the filled polymer). FP1 FP2 FP3 FP4 FP5 Filler A [wt.-%] (comparative) 10 20 20 CM1 [wt.-%] (invention) 10 16 Polymer 1 [wt.-%] 90 84 90 80 80 Ash content [wt.-%] 9 14 8 15 15

[0359] Formulations FP6 to FP16 were preblended in a rotating drum mixer and subsequently filled in the extruder hopper of the extruder.

[0360] The two components of formulations FP6 to FP 16 have been fed continuously by to loss in weight feeders (Coperion K-Tron K-CL-SFS-KT20) to the hopper of the extruder.

TABLE-US-00003 TABLE 3 Compositions and properties of prepared filled polymers (FP6 to FP16, wt.-% is based on total weight of the filled polymer). FP6 FP7 FP8 FP9 FP10 FP11 FP12 FP13 FP14 FP15 FP16 Filler A 12 24 [wt.-%] (comparative) Filler B 12 24 [wt.-%] (comparative) CM1 [wt.-%] 10 20 (invention) CM2 [wt.-%] 10 20 (invention) CM3 [wt.-%] 10 20 (invention) CM4 [wt.-%] 10 (invention) Polymer 2 90 80 90 80 90 80 90 88 76 88 76 [wt.-%] Ash content 9 18 9 18 9 18 9 9 18 9 18 [wt.-%]

[0361] 3.3 Extrusion Coating with FP1 to FPS

[0362] The extrusion coating has been carried out on an EK Pack A2 Extrusion coater (Coater: BLM/Moncalvao, Extrusion Coater) with a machine speed of 80 m/min and a coating width of 60 cm. The extruder was set to an increasing temperature profile as follows: 250 C., 260 C., 270 C., 280 C., 290 C. and 300 C. The screw speed was 100 rpm. The temperature for the extrusion die has been set to 300 C. to 306 C., the resulting mass temperature was 290 C. to 310 C.

TABLE-US-00004 TABLE 4 Compositions and properties of prepared extrusion coated papers (ECP1 to ECP 8, wt.-% is based on total weight of the filled polymer in the polymer used for extrusion-coating). Filler level [wt.-%] Coating weight [g/m.sup.2] ECP1 (invention) 10 FP1 15 ECP2 (invention) 16 FP2 15 ECP3 (comparative) 10 FP3 15 ECP4 (comparative) 20 FP4 15 ECP5 (comparative) 20 FP5 32 ECP6 (comparative) .sup.a 15 ECP7 (comparative) .sup.a 30 .sup.aunfilled polymer.

[0363] 3.4 Sealability

[0364] FIG. 1 shows the hot tack measurements at different sealing temperatures. As can be gathered from FIG. 1 the extrusion coated papers comprising a compacted material as polymer filler show superior sealability properties. Remarkable and completely surprising is not only the improvement in view of extrusion coated papers comprising an unfilled polymer but also the improvement in view of extrusion coated paper filled with a masterbatch filler.

[0365] 3.5 Extrusion Coating with FP6 to FP16

[0366] The extrusion coating has been carried out on a Dr. Collin Extrusion coating line MF-EXB-400with a machine speed of 25 m/min and a coating width of 25 cm. The extruder was set to an increasing temperature profile as follows: 250 C., 260 C., 280 C., 300 C., 320 C. and 320 C. The screw speed was 50 rpm. The temperature for the extrusion die has been set to 320 C., the resulting mass temperature was 315 C. to 325 C. The coating weight was 15 g/m.sup.2. There was no pretreatment of the substrate.

[0367] 3.6 Peel Force

TABLE-US-00005 TABLE 5 Peel force of formulations FP 6 to FP 16. FP6 FP7 FP8 FP9 FP10 FP11 FP13 FP14 FP15 FP16 Peel force [N] 0.8 0.6 0.9 0.8 1 0.6 0.7 0.4 0.4 0.3

[0368] Table 5 shows the peel force. As can be gathered from table 5 the extrusion coated papers comprising a compacted material as polymer filler show superior adhesion properties. All formulation with 9 wt.-% ash content provide higher peel force when using the innovative filler compared to the comparative pellet fillers. Also all formulation with 18 wt.-% ash content provide higher peel force when using the filler according to the invention compared to the comparative pellet fillers. This is remarkable and completely surprising. Filler B comprises the identical combination of binders (amount and kind) than CM2. Surprisingly the peel force is much higher for FP8 and FP9 comprising CM2 than for FP13 and FP14 comprising filler B.

[0369] 3.7 Sealability

TABLE-US-00006 TABLE 6 Hot tack force of formulations FP6 to FP 16 at 110 C. seal bar temperature. FP6 FP7 FP10 FP11 FP12 FP13 FP14 FP15 FP16 Hot tack force [N] 4.09 3.52 4.61 3.5 4.82 3.76 3.5 3.75 3.3

[0370] Table 6 shows the hot tack measurements at 110 C. sealing bar temperature. As can be gathered from table 6 the extrusion coated papers comprising a compacted material as polymer filler show superior sealing properties compared to pellet masterbatches. All formulation with 9 wt.-% ash content provide hot tack force when using the innovative compacted filler compared to the comparative pellet fillers. Also all formulation with 18 wt.-% ash content provide higher hot tack when using the innovative filler compared to the comparative pellet fillers. This is remarkable and completely surprising.