Surface-treated fillers for ultrathin breathable films

Abstract

A breathable film is described having a basis weight from 1 g/m.sup.2 to 10 g/m.sup.2, a process for producing the breathable film and use of a surface-treated filler material product as filler in the breathable film. Finally, an article is described that includes the breathable film as well as the use of the breathable film in hygienic applications, medical applications, healthcare applications, filtration materials, geotextile products, agricultural applications, horticultural applications, clothing, footwear products, baggage products, household applications, industrial applications, packaging applications, building applications, or construction.

Claims

1. A breathable film having a basis weight from 1 g/m.sup.2 to 10 g/m.sup.2, the breathable film comprising at least one thermoplastic polymer and a surface-treated filler material product, 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 0.1 m to 7 m, a top cut particle size d.sub.98 of 15 m, a fineness such that at least 65 wt.-%, of all particles have a particle size of <1 m, a specific surface area (BET) 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, and a residual total moisture content of 1 wt.-%, based on the total dry weight of the at least one ground calcium carbonate-comprising filler material, and B) a treatment layer on the surface of the at least one ground calcium carbonate-comprising filler material comprising i. a phosphoric acid ester 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 ii. at least one saturated aliphatic linear or branched carboxylic acid and salty reaction products thereof, and/or iii. at least one aliphatic aldehyde and/or salty reaction products thereof, wherein the at least one saturated aliphatic linear or branched carboxylic acid is selected from the group consisting of carboxylic acids consisting of pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, nonadecanoic acid, arachidic acid, heneicosylic acid, behenic acid, tricosylic acid, lignoceric acid and mixtures thereof, and/or iv. at least one polydialkylsiloxane, and/or v. mixtures of the materials according to i. to iv., wherein the surface-treated filler material product comprises the treatment layer in an amount of from 0.1 wt.-% to 3 wt.-%, based on the total dry weight of the at least one ground calcium carbonate-comprising filler material.

2. The breathable film of claim 1, wherein the at least one ground calcium carbonate-comprising filler material is a wet ground calcium carbonate-comprising filler material.

3. The breathable film of claim 1, wherein the at least one thermoplastic polymer is a polyolefin.

4. The breathable film of claim 1, wherein the breathable film comprises the surface-treated filler material product in an amount from 1 wt.-% to 85 wt.-%, based on the total weight of the breathable film.

5. The breathable 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.

6. The breathable 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 0.25 m to 5 m, and/or b) a top cut particle size d.sub.98 of 12.5 m, and/or c) a fineness such that at least 65 wt. %, 70 wt.-%, of all particles have a particle size of <1 m.

7. The breathable film of claim 1, wherein the at least one ground calcium carbonate-comprising filler material has a specific surface area (BET) of from 0.5 m.sup.2/g to 50 m.sup.2/g, as measured using nitrogen and the BET method according to ISO 9277.

8. The breathable film of claim 1, wherein the at least one ground calcium carbonate-comprising filler material has a residual total moisture content of from 0.01 wt.-% to 0.2 wt.-%, based on the total dry weight of the at least one ground calcium carbonate-comprising filler material.

9. The breathable film of claim 1, wherein the surface-treated filler material product also has a moisture pick-up from 0.1 mg/g to 1 mg/g, at a temperature of 23 C. (2 C.).

10. The breathable film of claim 1, wherein the surface-treated filler material product also has a volatile onset temperature of 250 C.

11. The breathable film of claim 1, wherein the film has a basis weight from 5 to 10 g/m.sup.2.

12. A process for producing a breathable film having a basis weight from 1 g/m.sup.2 to 10 g/m.sup.2, the process comprising the steps of: a) providing a composition comprising at least one thermoplastic polymer and a surface-treated filler material product, and b) forming a film from the composition of step a), and c) stretching the film obtained in step b) into at least one direction, 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 0.1 m to 7 m, a top cut particle size d.sub.98 of 15 m, a fineness such that at least 65 wt. %, of all particles have a particle size of <1 m, a specific surface area (BET) from 0.5 to 150 m.sup.2/g, as measured using nitrogen and the BET method according to ISO 9277, and a residual total moisture content of 1 wt. %, based on the total dry weight of the at least one ground calcium carbonate-comprising filler material, and B) a treatment layer on the surface of the at least one ground calcium carbonate-comprising filler material comprising i. a phosphoric acid ester blend of one or more phosphoric acid mono-ester and salty reaction products thereof and/or one or more phosphoric acid diester and salty reaction products thereof, and/or ii. at least one saturated aliphatic linear or branched carboxylic acid and salty reaction products thereof, wherein the at least one saturated aliphatic linear or branched carboxylic acid is selected from the group consisting of carboxylic acids consisting of pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, nonadecanoic acid, arachidic acid, heneicosylic acid, behenic acid, tricosylic acid, lignoceric acid and mixtures thereof, and/or iii. at least one aliphatic aldehyde and/or salty reaction products thereof, and/or iv. at least one polydialkylsiloxane, and/or v. mixtures of the materials according to i. to iv., wherein the surface-treated filler material product comprises the treatment layer in an amount of from 0.1 to 3 wt. %, based on the total dry weight of the at least one ground calcium carbonate-comprising filler material.

13. The process of claim 12, wherein the composition provided in step a) is a masterbatch or a compound obtained by mixing and/or kneading the at least one thermoplastic polymer and the surface-treated filler material product to form a mixture and continuously pelletizing the obtained mixture under water.

14. An article comprising the breathable film having a basis weight from 1 g/m.sup.2 to 10 g/m.sup.2 according to claim 1, wherein the article is selected from the group consisting of hygiene products, medical products, healthcare products, filter products, geotextile products, agriculture products, horticulture products, clothing, footwear products, baggage products, household products, industrial products, packaging products, building products, and construction products.

15. The breathable film of claim 3, wherein the at least one thermoplastic polymer is selected from the group consisting of polypropylene, polyethylene, polybutylene, and mixtures thereof.

16. The breathable film of claim 3, wherein the at least one thermoplastic polymer is selected from the group consisting of high density polyethylene (HDPE), linear low density polyethylene (LLDPE), low density polyethylene (LDPE), ultra-low density polyethylene (ULDPE), very low density polyethylene (VLDPE), and mixtures thereof.

17. The breathable film of claim 4, wherein the surface-treated filler material product is present in an amount from 2 wt.-% to 80 wt.-%.

18. The breathable film of claim 4, wherein the surface-treated filler material product is present in an amount from 5 wt.-% to 75 wt.-%.

19. The breathable film of claim 4, wherein the surface-treated filler material product is present in an amount from 10 wt.-% to 65 wt.-%.

20. The breathable film of claim 4, wherein the surface-treated filler material product is present in an amount from 15 wt.-% to 60 wt.-%.

21. The breathable film of claim 5, wherein the at least one ground calcium carbonate-comprising filler material is natural ground calcium carbonate.

22. The breathable film of claim 6, wherein the weight medium particle size d.sub.50 is from 0.5 m to 4 m.

23. The breathable film of claim 6, wherein the weight medium particle size d.sub.50 is from 0.6 m to 1 m.

24. The breathable film of claim 6, wherein the top cut particle size d.sub.98 is <10 m.

25. The breathable film of claim 6, wherein the top cut particle size d.sub.98 is <7.5 m.

26. The breathable film of claim 6, wherein the top cut particle size d.sub.98 is <3 m.

27. The breathable film of claim 6, wherein the fineness is such that at least 70 wt.-% of all particles have a particle size of <1 m.

28. The breathable film of claim 6, wherein the fineness is such that at least 75 wt.-% of all particles have a particle size of <1 m.

29. The breathable film of claim 6, wherein the fineness is such that at least 80 wt.-% of all particles have a particle size of <1 m.

30. The breathable film of claim 7, wherein the specific surface area (BET) is from 0.5 m.sup.2/g to 35 m.sup.2/g.

31. The breathable film of claim 7, wherein the specific surface area (BET) is from 0.5 m.sup.2/g to 15 m.sub.2/g.

32. The breathable film of claim 8, wherein the residual total moisture content is from 0.02 wt. % to 0.15 wt. %.

33. The breathable film of claim 8, wherein the residual total moisture content is from 0.04 wt.-% to 0.15 wt.-%.

34. The breathable film of claim 9, wherein the moisture pick-up is from 0.2 mg/g to 0.9 mg/g.

35. The breathable film of claim 9, wherein the moisture pick-up is from 0.2 mg/g to 0.8 mg/g.

36. The breathable film of claim 10, wherein the volatile onset temperature is 260 C.

37. The breathable film of claim 10, wherein the volatile onset temperature is 270 C.

38. The breathable film of claim 11, wherein the basis weight is from 6 g/m.sup.2 to 10 g/m.sup.2.

39. The breathable film of claim 11, wherein the basis weight is from 7 g/m.sup.2 to 9 g/m.sup.2.

40. The breathable film of claim 11, wherein the basis weight is about 8 g/m.sup.2.

Description

DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows an SEM image of sample 3.

(2) FIG. 2 shows an SEM image of sample 6.

(3) FIG. 3 shows an SEM image of sample 9.

(4) FIG. 4 shows an SEM image of sample 12.

EXAMPLES

1 Measurement Methods and Materials

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

(6) Particle Size

(7) The particle distribution of the untreated ground calcium carbonate-comprising filler material was measured using a Sedigraph 5120 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.

(8) Specific Surface Area (BET)

(9) The specific surface area was measured using nitrogen and the BET method according to ISO 9277.

(10) Ash Content

(11) The ash content in [%] of the masterbatches 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 is measured as the total amount of remaining inorganic residues.

(12) Force at Break

(13) Force at break determination was performed according to ISO 527-3. The film specimen width was of 15 mm and the testing length was 5 cm.

(14) Maximum Elongation at Break

(15) Elongation at break determination was performed according to ISO 527-3. The film specimen width was of 15 mm and the testing length was 5 cm.

(16) Tensile E-Modulus (Modulus of Elasticity)

(17) Tensile E-modulus determination was performed according to ISO 527-3. The film specimen width was of 15 mm and the testing length was 5 cm. The E-modulus corresponded to the inclination of the tensile test curve between the points at 0.02% and 2% elongation.

(18) Visual Evaluation of the Film

(19) Film samples have been put under a light microscope. Calcium carbonate agglomerates appear black upon illumination from below and white upon illumination from above.

(20) Water Vapour Transmission Rate (WVTR)

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

(22) Hydrostatic Pressure Test (Water Column)

(23) The hydrostatic pressure test has been carried out according to a procedure which is equivalent to AATCC Test Method 127-2013, WSP 80.6 and ISO 811. A film sample (test area=10 cm.sup.2) was mounted to form a cover on the test head reservoir. This film sample was subjected to a standardized water pressure, increased at a constant rate until leakage appears on the outer surface of the film, or water burst occurred as a result of film failure (pressure rate gradient=100 mbar/min.). Water pressure was measured as the hydrostatic head height reached at the first sign of leakage in three separate areas of the film sample or when burst occurs. The head height results were recorded in centimetres or millibars of water pressure on the specimen. A higher value indicated greater resistance to water penetration. The TEXTEST FX-3000, Hydrostatic Head Tester (Textest AG, Switzerland), was used for the hydrostatic pressure measurements.

2 Materials

(24) CC1 (inventive): Natural ground calcium carbonate, 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 2.2 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

(25) CC2 (inventive): Natural ground calcium carbonate, 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.

(26) P1: LLDPE Dowlex 2035G (MFR: 6 g/10 min (190 C., 2.16 kg), density: 0.919 g/cm.sup.3 according to technical data sheet), commercially available from The Dow Chemical Company, USA.

(27) P2: LDPE Dow SC 7641 (MFR: 2 g/10 min (190 C., 2.16 kg), density: 0.923 g/cm.sup.3 according to technical data sheet), commercially available from The Dow Chemical Company, USA.

(28) P3: Polyethylene Elite 5230G (MFR: 4 g/10 min (190 C., 2.16 kg), density: 0.916 g/cm.sup.3 according to technical data sheet), commercially available from The Dow Chemical Company, USA.

(29) P4: Polypropylene homopolymer Braskem Polypropylene H358-02 (MFR: 2.1 g/10 min (230 C., 2.16 kg), density: 0.900 g/cm.sup.3 according to technical data sheet), commercially available from Braskem Europe GmbH.

3 Examples

Example 1Preparation of Compounds (CO)

(30) Compounds containing 50 wt.-% CC1 or CC2, respectively, were continuously prepared on a lab scale Buss kneader (PR46 from Buss AG, Switzerland). The obtained compounds were pelletized on a spring load pelletizer, model SLC (Gala, USA) in a water bath having a starting temperature between 20 and 25 C. The compositions and filler contents of the prepared compounds are compiled in Table 1 below. The precise filler content was determined by the ash content.

(31) TABLE-US-00001 TABLE 1 Compositions and properties of prepared compounds. Ash P1 P2 P3 P4 content Compound Filler [wt.-%] [wt.-%] [wt.-%] [wt.-%] [wt.-%] CO1 CC1 45 5 50.0 CO2 CC1 50 49.4 CO3 CC1 40 10 50.0 CO4 CC2 45 5 50.2 CO5 CC2 50 49.9 CO6 CC2 40 10 50.5

(32) The results shown in Table 1 confirm that compounds with good quality were produced.

Example 2Preparation of Breathable Films

(33) Breathable films were produced by a pilot-extrusion cast-film line with integrated MDO-II unit (Dr. Collin GmbH, Germany) the extruder temperature settings were 195 C.-210 C.-230 C.-230 C., and the rotation speed of the extruder was approximately 35 rpm and 20 rpm respectively, using the compounds of Example 1. The roller speed of the stretching unit was changed and optimized until a good stretched film was achieved.

(34) The film quality of the obtained breathable films was inspected visually and the films were tested regarding their water vapour transmission rate (WVTR) and their hydrostatic pressure. The results are shown in Table 2 below.

(35) TABLE-US-00002 TABLE 2 Compositions and properties of prepared breathable films. Extruder Film Hydrostatic speed grammage Film WVTR pressure Sample [rpm] Compound [g/m.sup.2] quality [g/(m.sup.2 day)] [mbar] 1 35 CO1 13.1 ok 4 400 257 2 35 CO2 13.6 ok 1 600 470 3 35 CO3 13.3 ok 3 300 208 4 35 CO4 13.1 ok 4 200 237 5 35 CO5 13.3 ok 1 500 367 6 35 CO6 13.1 ok 3 300 175 7 20 CO1 7.1 ok 4 400 115 8 20 CO2 7.6 ok 2 100 282 9 20 CO3 7.6 ok 3 300 123 10 20 CO4 7.6 ok 4 200 139 11 20 CO5 7.9 ok 1 100 292 12 20 CO6 7.5 ok 3 300 87

(36) The results shown in Table 2 confirm that the inventive breathable film has a good quality and breathability.

(37) SEM images of the samples 3, 6, 9 and 12 are shown in FIG. 1 to 4.

(38) The mechanical properties, such as the force at break, E-modulus as well as the elongation at break in machine and cross direction, of the obtained breathable films are outlined in Tables 3 and 4.

(39) TABLE-US-00003 TABLE 3 Compositions and mechanical properties of prepared breathable films. Film samples taken in machine direction (MD). Max. Extruder Force at Elongation speed break E-modulus at break Sample [rpm] Compound [N] - MD [MPa] - MD [%] - MD 1 35 CO1 17 550 21.4 2 35 CO2 30.3 1 763 37 3 35 CO3 12.9 373 64.7 4 35 CO4 11.9 371 29.8 5 35 CO5 27.6 1 099 63 6 35 CO6 10.4 320 81.5 7 20 CO1 11.0 712 13.1 8 20 CO2 21.9 2 157 21.3 9 20 CO3 7.8 598 37.2 10 20 CO4 7.7 439 13.9 11 20 CO5 15.9 1 200 22.6 12 20 CO6 5.9 360 45.3

(40) TABLE-US-00004 TABLE 4 Compositions and mechanical properties of prepared breathable films. Film samples taken in cross direction (CD). Max. Extruder Force at Elongation speed break E-modulus at break Sample [rpm] Compound [N] - CD [MPa] - CD [%] - CD 1 35 CO1 0.67 67 407 2 35 CO2 2.3 313 437 3 35 CO3 1.06 127 480 4 35 CO4 0.69 52 358 5 35 CO5 2.3 301 348 6 35 CO6 1.0 97 461 7 20 CO1 0.34 59 353 8 20 CO2 1.1 253 202 9 20 CO3 0.51 125 463 10 20 CO4 0.32 45 332 11 20 CO5 1.2 234 302 12 20 CO6 0.45 94 331