Surface-treated fillers for polyester films

Abstract

A mono or multi-layer polyester film is described. Also described, is a process for producing the mono or multi-layer polyester film, the use of a surface-treated filler material product as a voiding agent in the mono or multi-layer polyester film, and an article including the mono or multi-layer polyester film. Further, use of the mono or multi-layer polyester film is described in packaging products, insulating materials, solar, marine or aviation applications, science, electronic or acoustic applications, wires, cables, radio frequency identifications, flexible circuits, graphic arts, stone paper, holograms, filter products, cosmetic products, household products, imaging, recording media, or industrial products.

Claims

1. A mono or multi-layer polyester film, wherein at least one layer of the film comprises at least one polyester in an amount ranging from 20.0 wt.-% to <70 wt.-% and a surface-treated filler material product in an amount ranging from >30 wt.-% to 80.0 wt.-%, based on the total weight of the layer, wherein the surface-treated filler material product comprises: A) at least one ground calcium carbonate-comprising filler material having a weight median particle size d.sub.50 in the range from 0.5 m to 3.0 m, and B) a treatment layer on the surface of the at least one ground calcium carbonate-comprising filler material, wherein the treatment layer comprises i. at least one aliphatic aldehyde and/or a salty reaction product thereof, and/or ii. at least one mono-substituted succinic anhydride and/or a salty reaction product thereof, wherein the mono-substituted succinic anhydride comprises a succinic anhydride mono-substituted with a substituent that is a linear, branched, aliphatic or cyclic group having a total number of carbon atoms from at least C.sub.2 to C.sub.30 in the substituent, and/or iii. at least one polydialkylsiloxane, and/or iv. mixtures of the materials according to i. to iii., wherein the surface-treated filler material product comprises the treatment layer in an amount of from 0.1 wt.-% to 2.3 wt.-%, based on the total dry weight of the at least one ground calcium carbonate-comprising filler material.

2. The mono or multi-layer polyester film of claim 1, wherein the at least one polyester and surface-treated filler material product comprising layer of the film comprises the surface-treated filler material product in an amount ranging from 30.01 wt.-% to 80.0 wt.-%, based on the total weight of the layer.

3. The mono or multi-layer polyester film of claim 1, wherein the at least one polyester is selected from the group consisting of polyglycolic acid (PGA), polylactic acid (PLA), polycaprolactone (PCL), polyhydroxybutyrate (PHB), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polyethylene furanoate (PEF), bio-based polyesters, polyester-recycling materials and mixtures thereof.

4. The mono or multi-layer polyester film of claim 1, wherein the at least one polyester and surface-treated filler material product comprising layer of the film comprises the at least one polyester in an amount ranging from 20.0 wt.-% to 69.99 wt.-%, based on the total weight of the layer.

5. The mono or multi-layer polyester film of claim 1, wherein the at least one ground calcium carbonate-comprising filler material is a wet or dry ground calcium carbonate-comprising filler material and optionally is a wet ground calcium carbonate-comprising filler.

6. The mono or multi-layer polyester film of claim 1, wherein the at least one ground calcium carbonate-comprising filler material is natural ground calcium carbonate, precipitated calcium carbonate, modified calcium carbonate, surface-treated calcium carbonate, or a mixture thereof.

7. The mono or multi-layer polyester film of claim 1, wherein the at least one ground calcium carbonate-comprising filler material has a) a weight median particle size d.sub.50 from 0.5 m to 2.5 m, and/or b) a top cut particle size d.sub.98 of 15 m, and/or c) a fineness such that at least 15 wt.-%, of all particles have a particle size of <0.5 m, and/or d) a specific surface area (BET) of from 0.5 m.sup.2/g to 150 m.sup.2/g, as measured using nitrogen and the BET method according to ISO 9277.

8. The mono or multi-layer polyester film of claim 1, wherein the treatment layer on the surface of the at least one ground calcium carbonate-comprising filler material comprises at least one aliphatic aldehyde and/or a salty reaction product thereof.

9. The mono or multi-layer polyester film of claim 1, wherein the surface-treated filler material product comprises the treatment layer in an amount of from 0.2 wt.-% to 2.0 wt.-%, based on the total dry weight of the at least one ground calcium carbonate-comprising filler material.

10. The mono or multi-layer polyester film of claim 1, wherein the at least one polyester and surface-treated filler material product comprising layer of the film further comprises a thermoplastic polymer.

11. The mono or multi-layer polyester film of claim 10, wherein the at least one polyester and surface-treated filler material product comprising layer of the film comprises the thermoplastic polymer in a range of from 0.1 wt.-% to 29.9 wt. %, based on the total weight of the layer.

12. The mono or multi-layer polyester film of claim 1, wherein the film or the at least one polyester and surface-treated filler material product comprising layer, has a) a density in a range of from 1.8 g/cm.sup.3 to 2.4 g/cm.sup.3, and/or b) an opacity of 50%.

13. The mono or multi-layer polyester film of claim 1, wherein the at least one polyester and surface-treated filler material product comprising layer of the film further comprises an inorganic filler material different from the surface-treated filler material product.

14. The mono or multi-layer polyester film of claim 1, wherein the film or the at least one polyester and surface-treated filler material product comprising layer, comprises an additive selected from the group consisting of light stabilizers, optionally 2-hydroxybenzophenones, 2-hydroxybenzotriazoles, organonickel compounds, salicylic esters, cinnamic ester derivatives, resorcinol monobenzoates, oxanilides, hydroxybenzoic esters, sterically hindered amines and triazines, hydroxy-phenyl-triazin, optical brightener, blue dyes, blue dyes soluble in polyester, antiblocking agents, white pigments and mixtures thereof.

15. The mono or multi-layer polyester film of claim 1, wherein the film is a cast film, a blown film, a double bubble film or a mono axially oriented polyester film.

16. A process for producing the mono or multi-layer polyester film as defined in claim 1, the process comprising the steps of: a) providing a composition comprising at least one polyester and a surface-treated filler material product, and b) forming a film from the composition of step a), wherein the surface-treated filler material product comprises A) at least one ground calcium carbonate-comprising filler material having a weight median particle size d.sub.50 in the range from 0.5 m to 3.0 m, and B) a treatment layer on the surface of the at least one ground calcium carbonate-comprising filler material, wherein the treatment layer comprises: (i) at least one aliphatic aldehyde and/or a salty reaction product thereof, and/or (ii) at least one mono-substituted succinic anhydride and/or a salty reaction product thereof, wherein the mono-substituted succinic anhydride comprises a succinic anhydride mono-substituted with a substituent that is a linear, branched, aliphatic or cyclic group having a total number of carbon atoms from at least C.sub.2 to C.sub.30 in the substituent, and/or (iii) at least one polydialkylsiloxane, and/or (iv) mixtures of the materials according to i. to iii., wherein the surface-treated filler material product comprises the treatment layer in an amount of from 0.1 wt.-% to 2.3 wt.-%, based on the total dry weight of the at least one ground calcium carbonate-comprising filler material.

17. The process of claim 16, wherein the composition provided in step a) is a masterbatch obtained by mixing and/or kneading the at least one polyester and the surface-treated filler material product to form a mixture and continuously pelletizing the obtained mixture or a compound obtained by mixing and/or kneading the at least one polyester and the surface-treated filler material product to form a mixture and continuously pelletizing the obtained mixture.

18. The process of claim 16, wherein the composition provided in step a) is a masterbatch or compound comprising the surface-treated filler material product in an amount of from >30 wt.-% to 85 wt. %, based on the total weight of the masterbatch or compound.

19. The process of claim 16, wherein the composition comprising at least one polyester and a surface-treated filler material product of step a) is obtained by adding the surface-treated filler material product, optionally before or after, to the polycondensation process of the at least one polyester.

20. The process of claim 16, wherein process steps a) and b) are carried out simultaneously, optionally in that the at least one polyester and the surface-treated filler material product are added directly into an extruder to carry out step b).

21. The process of claim 16, wherein the process further comprises a step c) of stretching the film obtained in step b) in only one direction among machine direction (MD) or transverse direction (TD).

22. A voiding agent in a mono or a multi-layer polyester film, the voiding agent comprising a surface-treated filler material product, wherein the polyester film is a mono or multi-layer polyester film comprising at least one layer comprising at least one polyester in an amount ranging from 20.0 wt.-% to <70 wt.-% and the surface-treated filler material product in an amount ranging from >30 wt.-% to 80.0 wt.-%, based on the total weight of the layer, wherein the surface-treated filler material product comprises: A) at least one ground calcium carbonate-comprising filler material having a weight median particle size d.sub.50 in the range from 0.5 m to 3.0 m, and B) a treatment layer on the surface of the at least one ground calcium carbonate-comprising filler material, wherein the treatment layer comprises: i. at least one aliphatic aldehyde and/or a salty reaction product thereof, and/or ii. at least one mono-substituted succinic anhydride and/or a salty reaction product thereof, wherein the mono-substituted succinic anhydride comprises a succinic anhydride mono-substituted with a substituent that is a linear, branched, aliphatic or cyclic group having a total number of carbon atoms from at least C.sub.2 to C.sub.30 in the substituent, and/or iii. at least one polydialkylsiloxane, and/or iv. mixtures of the materials according to i. to iii., wherein the surface-treated filler material product comprises the treatment layer in an amount of from 0.1 wt.-% to 2.3 wt.-%, based on the total dry weight of the at least one ground calcium carbonate-comprising filler material.

23. An article comprising a mono or multi-layer polyester film according to claim 1, wherein the article is selected from the group consisting of packaging products, optionally flexible packaging products, food contact articles, paper or glass coverings, insulating materials, solar articles, optionally photovoltaic front or backsheets, marine or aviation articles, science articles, electronic or acoustic articles, optionally displays, wires, cables, radio frequency identification articles, flexible circuits, graphic arts, optionally labels, stone paper, optionally bags, packages, boxes, books, booklets, brochures, loyalty cards, business cards, greeting cards, corrugated boards, envelopes, food trays, labelling, games, tags, magazines, signage, billboards, stationary, diaries, pads or notebooks, and holograms, filter products, cosmetic products, household products, imaging, recording media, optionally photographic paper, X-ray film or thermal transfer imaging or industrial products, optionally capacitors, release sheets, fiberglass panels, laminating films, hot stamping foils and insulation facing.

24. A method of making an article, the method comprising incorporating the mono or multi-layer polyester film according to claim 1 into the article wherein the article is a packaging product, optionally a flexible packaging product, a food contact article, a paper or glass covering, an insulating material, a solar article, optionally photovoltaic front or backsheet, a marine or aviation article, a science article, electronic or acoustic article, optionally display, wire, cable, radio frequency identification article, flexible circuit, graphic art, optionally label, stone paper, optionally bag, package, box, book, booklet, brochure, loyalty card, business card, greeting card, corrugated board, envelope, food tray, labelling, game, tag, magazine, signage, billboard, stationary, diary, pad or notebook, and hologram, filter product, cosmetic product, household product, imaging, recording media, optionally photographic paper, X-ray film or thermal transfer imaging or industrial product, optionally capacitor, release sheet, fiberglass panel, laminating film, hot stamping foil or insulation facing.

25. The mono or multi-layer polyester film of claim 8, wherein the treatment layer comprises the at least one mono-substituted succinic anhydride and/or salty reaction product thereof.

26. The mono or multi-layer polyester film of claim 1, wherein the treatment layer on the surface of the at least one ground calcium carbonate-comprising filler material comprises at least one polydialkylsiloxane.

27. The mono or multi-layer polyester film of claim 10, wherein the thermoplastic polymer is crosslinked with a crosslinking agent and/or is selected from the group consisting of a polyolefin selected from the group consisting of polypropylene, polyethylene, polybutylene, and mixtures thereof, a cyclic olefin copolymer (COC), a polyketone, a polysulphone, a fluoropolymer, a polyacetal, an ionomer, an acrylic resin, a polystyrene resin, a polyurethane, a polyamide, a polycarbonate, a polyacrylonitrile and a copolymerized resin and mixtures thereof, which is dispersed in the at least one polyester.

28. The mono or multi-layer polyester film of claim 13, wherein inorganic filler material is selected from the group consisting of alumina, silica, titanium dioxide, alkaline metal salts, optionally barium carbonate, calcium sulfate, barium sulfate and mixtures thereof, optionally in an amount of 1 wt.-% to 10 wt.-% based on the total weight of the layer.

29. The mono or multi-layer polyester film of claim 1, wherein the at least one ground calcium carbonate-comprising filler material has a specific surface area (BET) of from 2.5 m.sup.2/g to 150 m.sup.2/g, as measured using nitrogen and the BET method according to ISO 9277.

30. The mono or multi-layer polyester film of claim 1, wherein the surface-treated filler material product comprises the treatment layer in an amount of from 0.6 wt.-% to 2.3 wt.-%, based on the total dry weight of the at least one ground calcium carbonate-comprising filler material.

Description

EXAMPLES

1 Measurement Methods and Materials

(1) In the following, measurement methods and materials implemented in the examples are described.

(2) Intrinsic Viscosity

(3) The intrinsic viscosity is measured according to DIN ISO 1628/1 and DIN ISO 1628/5, October 1999 (in decalin at 135 C.).

(4) MFR.sub.2

(5) The MFR.sub.2 is measured according to ISO 1133 (230 C., 2.16 kg load).

(6) Crystallization Temperature T.sub.c

(7) The crystallization temperature is measured by differential scanning calorimetry (DSC) on a Mettler-Toledo Polymer DSC instrument (Mettler-Toledo (Schweiz) GmbH, Switzerland). The crystallization curve was obtained during 10 C./min cooling and heating scans between 30 C. and 225 C. Crystallization temperatures were taken as the peak of endotherms and exotherms.

(8) Particle Size

(9) The particle distribution of the untreated ground calcium carbonate-comprising filler material was measured using a Sedigraph 5100 from the company Micromeritics, USA. The method and the instruments are known to the skilled person and are commonly used to determine grain size of fillers and pigments. The measurement was carried out in an aqueous solution comprising 0.1 wt.-% Na.sub.4P.sub.2O.sub.7. The samples were dispersed using a high speed stirrer and supersonics.

(10) Specific Surface Area (BET)

(11) Throughout the present document, the specific surface area (in m.sup.2/g) of the filler material is determined using the BET method (using nitrogen as adsorbing gas), which is well known to the skilled man (ISO 9277:2010).

(12) Ash Content

(13) The ash content in [wt.-%] of the masterbatches and films was determined by incineration of a sample in an incineration crucible which is put into an incineration furnace at 570 C. for 2 hours. The ash content was measured as the total amount of remaining inorganic residues.

(14) Film Thickness

(15) The film thickness was determined using a digital measuring slide Mitutoyo IP 66 (Mitutoyo Europe GmbH, Neuss, Germany). Measured values were reported in m.

(16) Density of a Film or Layer

(17) The density was determined from a test piece whereby a precise area of film (100 mm100 mm) is cut and weighed on an analytical balance. An average film thickness was determined by taking nine thickness measurements allocated over the whole film surface. The density was calculated and reported in [g/cm.sup.3]. Also an average yield in m.sup.2/kg and the unit weight in g/m.sup.2 can be calculated from these values.

(18) Moisture Pick-Up

(19) The term moisture pick-up susceptibility in the meaning of the present invention refers to the amount of moisture absorbed on the surface of the filler and is determined in mg moisture/g of the dry treated mineral filler product after exposure to an atmosphere of 10 and 85% of relative humidity, resp., for 2.5 hours at a temperature of +23 C. (2 C.). The treated mineral filler product is first held at an atmosphere of 10% of relative humidity for 2.5 hours then the atmosphere is changed to 85% of relative humidity, where the sample is held for another 2.5 hours. The weight increase between 10% and 85% relative humidity is then used to calculate the moisture pick-up in mg moisture/g of dry treated filler product. The blank value of the equipment was determined as being 0.15 to 0.2 mg/g, e.g. 0.19 mg/g. The results in the present application are net values, i.e. the measured value minus the blank value.

(20) Hydrophilicity

(21) The hydrophilicity of a filler is evaluated at +23 C. by determining the minimum water to ethanol ratio in a volume/volume based water/ethanol-mixture needed for the settling of the majority of said filler, where said filler is deposited on the surface of said water/ethanol-mixture by passage through a house hold tea sieve. The volume/volume base is related to the volumes of both separate liquids before blending them together and do not include the volume contraction of the blend. The evaluation at +23 C. refers to a temperature of +23 C.2 C.

(22) A 8:2 volumetric ratio of a water/ethanol-mixture has typically a surface tension of 41 mN/m and a 6:4 volumetric ratio of a water/ethanol-mixture has typically a surface tension of 26 mN/m measured at +23 C. (2 C.) as described in the Handbook of Chemistry and Physics, 84.sup.th edition, David R. Lide, 2003 (first edition 1913).

(23) Measurement of the Total Volatiles

(24) For the purpose of the present application, the total volatiles associated with fillers and evolved over a temperature range of 25 to 350 C. is characterized according to % mass loss of the filler sample over a temperature range as read on a thermogravimetric (TGA) curve.

(25) TGA analytical methods provide information regarding losses of mass and volatile onset temperatures with great accuracy, and is common knowledge; it is, for example, described in Principles of Instrumental analysis, fifth edition, Skoog, Holler, Nieman, 1998 (first edition 1992) in Chapter 31 pages 798 to 800, and in many other commonly known reference works. In the present invention, thermogravimetric analysis (TGA) is performed using a Mettler Toledo TGA 851 based on a sample of 500+/50 mg and scanning temperatures from 25 to 350 C. at a rate of 20 C./minute under an air flow of 70 ml/min.

(26) The skilled man will be able to determine the volatile onset temperature by analysis of the TGA curve as follows: the first derivative of the TGA curve is obtained and the inflection points thereon between 150 and 350 C. are identified. Of the inflection points having a tangential slope value of greater than 45 relative to a horizontal line, the one having the lowest associated temperature above 200 C. is identified. The temperature value associated with this lowest temperature inflection point of the first derivative curve is the volatile onset temperature.

(27) The total volatiles evolved on the TGA curve is determined using Stare SW 9.01 software. Using this software, the curve is first normalised relative to the original sample weight in order to obtain mass losses in % values relative to the original sample. Thereafter, the temperature range of 25 to 350 C. is selected and the step horizontal (in German: Stufe horizontal) option selected in order to obtain the % mass loss over the selected temperature range.

(28) Opacity

(29) The opacity measurements were done according to DIN 53146 by measuring the whiteness of a film sample on a black and a white substrate using a Byk-Gardner Spectro-Guide (Byk-Gardner GmbH, Germany). The opacity is the contrast ratio of the two measurements. The units are percent % and a perfectly opaque material will have an opacity value of 100%.

(30) Water Vapor Transmission Rate (WVTR)

(31) The WVTR value of the polyester films was measured with a Lyssy L80-5000 (PBI-Dansensor A/S, Denmark) measuring device according to ASTM E398.

2 Materials

(32) CC1 (inventive): Natural ground calcium carbonate, stone feed commercially available from Omya International AG, Switzerland (d.sub.50: 0.8 m; d.sub.98: 3 m, content of particles<0.5 m=35%), surface-treated with 1.7 wt.-% stearic acid (commercially available from Sigma-Aldrich, Croda) based on the total weight of the natural ground calcium carbonate. BET: 8.5 m.sup.2/g.

(33) CC2 (inventive): Natural ground calcium carbonate, stone feed commercially available from Omya International AG, Switzerland (d.sub.50: 0.8 m; d.sub.98: 3 m, content of particles<0.5 m=35%), surface-treated with 1.7 wt.-% alkenyl succinic anhydride (CAS [68784-12-3], concentration>93%) based on the total weight of the natural ground calcium carbonate. BET: 8.5 m.sup.2/g.

(34) CC3 (inventive): Natural ground calcium carbonate, stone feed commercially available from Omya International AG, Switzerland (d.sub.50: 1.7 m; d.sub.98: 6 m, content of particles<0.5 m=12%), surface-treated with 1.0 wt. % stearic acid (commercially available from Sigma-Aldrich, Croda) based on the total weight of the natural ground calcium carbonate. BET: 3.4 m.sup.2/g.

(35) CC4 (inventive): Natural ground calcium carbonate, stone feed commercially available from Omya International AG, Switzerland (d.sub.50: 1.7 m; d.sub.98: 6 m, content of particles <0.5 m=12%), surface-treated with 0.7 wt. % alkenyl succinic anhydride (CAS [68784-12-3], concentration>93%) based on the total weight of the natural ground calcium carbonate. BET: 3.4 m.sup.2/g.

(36) CC5 (inventive): Natural ground calcium carbonate, stone feed commercially available from Omya International AG, Switzerland (d.sub.50: 1.7 m; d.sub.98: 6.5 m, content of particles<2 m=57%), surface-treated with 1 wt.-% stearic acid (commercially available from Sigma-Aldrich, Croda) based on the total weight of the natural ground calcium carbonate. BET: 4 m.sup.2/g.

(37) CC6 (inventive): Natural ground calcium carbonate, stone feed commercially available from Omya International AG, Switzerland (d.sub.50: 2.6 m; d.sub.98: 15 m, content of particles<2 m=38%), surface-treated with 0.6 wt.-% stearic acid (commercially available from Sigma-Aldrich, Croda) based on the total weight of the natural ground calcium carbonate. BET: 2.5 m.sup.2/g.

(38) CC7 (comparative): Natural ground calcium carbonate, commercially available from Omya International AG, Switzerland (d.sub.50: 5 m; d.sub.98: 20 m), surface-treated with 0.5 wt.-% stearic acid (commercially available from Sigma-Aldrich, Croda) based on the total weight of the natural ground calcium carbonate. BET: 2.1 m.sup.2/g.

(39) CC8 (comparative): Natural ground calcium carbonate, commercially available from Omya International AG, Switzerland (d.sub.50: 5 m; d.sub.98: 30 m), without surface-treatment. BET: 2.1 m.sup.2/g.

(40) The surface-treatment of CC1 to CC7 has been carried out by using the methods described in EP 2 722 368 A1.

(41) P1: Polyethylene terephthalate (PET), Lighter C93 PET, commercially available from Equipolymers GmbH, Germany (intrinsic viscosity: 0.80.02 dl/g, crystallinity min. 50%, melting point 247 C., according to the technical data sheet provided by the supplier).

3 Examples

Example 1Preparation of Masterbatches

(42) Polypropylene masterbatches containing the calcium carbonate fillers CC1 to CC8 and the polymer P1 were continuously prepared on a lab scale Buss kneader (Buss PR46 from Buss AG, Switzerland). The polymer P1 was pre-dried prior to processing in an oven at 160 C. for 4 hours. The compositions and filler contents of the prepared masterbatches are compiled in Table 1 below. The precise filler content was determined by the ash content.

(43) TABLE-US-00001 TABLE 1 Composition and filler content of prepared masterbatches. Filler content Masterbatch Filler [wt.-%] MB1 (inventive) CC1 50 MB2 (inventive) CC2 50 MB3 (inventive) CC3 50 MB4 (inventive) CC4 50 MB5 (inventive) CC5 50 MB6 (inventive) CC6 50 MB7 (comparative) CC7 50 MB8 (comparative) CC8 50

(44) Masterbatches MB1 to MB6 could be produced in good quality, whereas masterbatches MB7 and MB8 were difficult to compound and received pellets were of bad quality.

Example 2Preparation of Polyester Cast Films Via Masterbatch

(45) Cast films were prepared on a Collin Laboratory Film Line (Dr. Collin GmbH, Germany) with a twin screw extruder with a diameter of 30 mm wide T-die and a take-up system, which had temperature controlled chill-rolls. The chilled roll was kept 20 mm from the T-die to produce a polyester sheet having a thickness of around 1 000 m. The extruder and die temperatures were consistent throughout the experiment. The die temperature was set at 270 C.; the line speed was 0.5 m/min. The masterbatch or polymer was mixed with the neat polymer P1 to receive cast films with the concentrations given in Table 2.

(46) TABLE-US-00002 TABLE 2 Compositions and properties of prepared cast films Filler content Film Sample Masterbatch [wt.-%] 1 (comp.) no 0 2 (inv.) MB1 35 3 (inv.) MB1 45 4 (inv.) MB2 35 5 (inv.) MB2 45 6 (inv.) MB3 35 7 (inv.) MB3 45 8 (inv.) MB4 35 9 (inv.) MB4 45 10 (inv.) MB5 35 11 (inv.) MB5 45 12 (inv.) MB6 35 13 (inv.) MB6 45

(47) All films shown in Table 2 are cast films which were produced in good quality with visual good appearance.

Example 3Preparation of Polyester Cast Films Via Direct Extrusion

(48) Cast films were prepared on a Collin Laboratory Film Line (Dr. Collin GmbH, Germany) with a twin screw extruder with a diameter of 30 mm wide T-die and a take-up system, which had temperature controlled chill-rolls. The chilled roll was kept 20 mm from the T-die to produce a polypropylene sheet having a thickness of around 1 000 m. The extruder is equipped with a vacuum venting system to remove during the extrusion volatiles and moisture coming from the raw materials. The extruder and die temperatures were consistent throughout the experiment. The die temperature was set at 270 C.; the line speed was 0.5 m/min. The masterbatch or polymer was mixed with the neat polymer P1 to receive cast films with the concentrations given in Table 2.

(49) TABLE-US-00003 TABLE 3 Compositions and properties of prepared cast films Filler content Film Sample Filler [wt.-%] 1 (comp.) no 0 2 (inv.) CC1 60 3 (inv.) CC1 70 4 (inv.) CC2 60 5 (inv.) CC2 70 6 (inv.) CC3 60 7 (inv.) CC3 70 8 (inv.) CC4 60 9 (inv.) CC4 70 10 (inv.) CC5 60 11 (inv.) CC5 70 12 (inv.) CC6 60 13 (inv.) CC6 70