BIAXIALLY ORIENTED POROUS FILM HAVING A PARTICLES-CONTAINING POROUS LAYER AND AN INORGANIC COATING

Abstract

The invention relates to a biaxially oriented, single- or multi-layer porous film, containing a -nucleating agent and comprising at least one porous layer, which contains at least one propylene polymer and particles, said particles having a melting point of more than 200 C. On the outer surface of the porous layer, said porous film has a coating of inorganic, preferably ceramic particles.

Claims

1.-24. (canceled)

25. A biaxially oriented, single- or multi-layer porous film, containing a 3-nucleating agent and comprising at least one porous layer, which contains at least one propylene polymer and particles, said particles having a melting point of more than 200 C. and said porous film having, on the outer surface of the porous layer, a coating of inorganic.

26. The film according to claim 25, wherein the porosity of the film is produced by conversion of 3-crystalline polypropylene as the film is drawn.

27. The film according to claim 25, wherein the film contains 2 to 60% by weight of particles, in relation to the weight of the porous layer, and at most one particle having a particle size of >1 m can be detected in an SEM image of an uncoated film sample of 10 mm.sup.2.

28. The film according to claim 25, wherein no particles having a particle size of >1 m can be detected in an SEM image of an uncoated film sample of 10 mm.sup.2.

29. The film according to claim 25, wherein the -nucleating agent is contained in the porous, particle-containing layer of the film.

30. The film according to claim 25, wherein the porous, particle-containing layer of the film contains 50 to 85% by weight of propylene homopolymer, 15 to 50% by weight of propylene block copolymer, and 50 to 10,000 ppm of f-nucleating agent.

31. The film according to claim 25, wherein the coated film has a Gurley value of less than 500 s.

32. The film according to claim 25, wherein the particles of the porous layer are inorganic spherical particles.

33. The film according to claim 25, wherein the particles of the porous, particle-containing layer are not vacuole-initiating particles, wherein vacuole-initiating particles are particles which, under biaxial drawing of a polypropylene film without -nucleating agent, lower the density of the polypropylene film to <0.85 g/cm.sup.3.

34. The film according to claim 25, wherein the particles of the porous, particle-containing layer are inorganic particles, are electrically non-conductive oxides of the metals Al, Zr, Si, Sn, Ti and/or Y.

35. The film according to claim 25, wherein the particles of the porous, particle-containing layer are TiO.sub.2 particles.

36. The film according to claim 25, wherein the coating of inorganic particles are ceramic particles which comprises particles of which the particle size, expressed as D50 value, lies in the range between 0.05 and 15 m.

37. The film according to claim 25, wherein the particle of the coating comprises an electrically non-conductive oxide of the metals Al, Zr, Si, Sn, Ti and/or Y.

38. The film according to claim 25, wherein the particles of the coating comprise particles based on oxides of silicon with the molecular formula SiO.sub.2, and mixed oxides with the molecular formula AlNaSiO.sub.2, and oxides of titanium with the molecular formula TiO.sub.2, wherein these are present in crystalline, amorphous or mixed form.

39. The film according to claim 25, wherein the particles of the coating have a melting point of at least 200 C.

40. The film according to claim 25, wherein the particles of the coating are ceramic particles.

41. The film according to claim 40, wherein the ceramic coating has a thickness of from 0.5 m to 80 m.

42. The film according to claim 40, wherein the application amount of ceramic coating is 0.5 g/m.sup.2 to 80 g/m.sup.2.

43. The film according to claim 40, wherein the ceramic coating comprises ceramic particles, the compressive strength of which is at least 100 kPa.

44. The film according to claim 40, wherein the ceramic coating also contains at least one end-consolidated binder selected from the group of binders based on polyvinylene dichloride (PVDC), polyacrylates, polymethacrylates, polyethylene imines, polyesters, polyamides, polyimides, polyurethanes, polycarbonates, silicate binders, grafted polyolefins, polymers from the class of halogenated polymers, and mixtures thereof.

45. The film according to claim 40, wherein the ceramic coating also contains at least one end-consolidated binder based on polyvinylene dichloride (PVDC).

46. The film according to claim 40, wherein the ceramic coating contains 98% by weight to 50% by weight of ceramic particles and 2% by weight to 50% by weight of at least one end-consolidated binder selected from the group of binders based on polyvinylene dichloride (PVDC), polyacrylates, polymethacrylates, polyethylene imines, polyesters, polyamides, polyimides, polyurethanes, polycarbonates, silicate binders, grafted polyolefins, polymers from the class of halogenated polymers, and mixtures thereof.

47. Lithium, lithium-ion, lithium-polymer or alkaline earth batteries which comprise the film according to claim 25.

48. High-power or high-performance systems comprising the film according to claim 25.

Description

EXAMPLES

Example A: Batch Production

[0162] In a first step, a batch was produced from polymer (polypropylene) and particles and was used in the following test. This batch was produced as follows:

[0163] Approximately 60% by weight of a TiO2 pigment (Huntsmann TR28) together with 0.04% by weight of calcium pimelate as nucleating agent (calcium pimelate) were mixed, melted and granulated in a twin-screw extruder at a temperature of 230 C. and a screw revolution rate of 270 rpm with 39.96% by weight of granular material formed from isotactic polypropylene homopolymer (melting point 162 C.; MFI 3 g/10 min). The SEM images of the batch show finely distributed TiO2 particles with a particle size of from 20 to 500 nm without agglomerates of larger than 1 m, The -activity of the batch shows a value of 91% with the second heating.

Example B: Film Production

Film example: 1

[0164] After the extrusion method, a two-layer preliminary film was extruded from a flat film die at an extrusion temperature of 240 to 250 C. Here, the throughputs of the extruder were selected such that the thickness ratio of the layers A:B was 1:2. The multi-layer preliminary film was first removed on a chilling roll and cooled. The multi-layer preliminary film was then oriented and ultimately fixed in the longitudinal and transverse direction. The layers of the film had the following composition:

[0165] Composition of Layer A:

TABLE-US-00001 40% by weight TiO2 batch according to example A formed of 60% by weight TiO2 approx. 39.96% by weight propylene homopolymer 0.04% by weight nucleating agent in each case based on the batch
60% by weight polypropylene mixture formed of:
approx. 60% by weight of propylene homopolymer (PP) with an n-heptane-soluble proportion of 4.5% by weight (based on 100% PP) and a melting point of 165 C.; and a melt flow index of 3.2 g/10 min at 230 C. and 2.16 kg load (DIN 53 735) and
approx. 39.96% by weight of propylene ethylene block copolymer with an ethylene proportion of approx. 5% by weight based on the block copolymer and a melt flow index (230 C. and 2.16 kg) of 6 g/10 min
0.04% by weight nano Ca pimelate as -nucleating agent in each case based on the mixture

[0166] Composition of Layer B:

approx. 80% by weight propylene homopolymer (PP) with an n-heptane-soluble proportion of 4.5% by weight (based on 100% PP) and a melting point of 165 C.; and a melt flow index of 3.2 g/10 min at 230 C. and 2.16 kg load (DIN 53 735) and
approx. 19.96% by weight of propylene ethylene block copolymer with an ethylene proportion of approx. 5% by weight based on the block copolymer and a melt flow index (230 C. and 2.16 kg) of 6 g/10 min
0.04% by weight nano Ca pimelate as -nucleating agent

[0167] The layers of the film additionally contained stabiliser and neutralising agent in conventional amounts. The nano Ca pimelate was produced as described in examples 1a or 1b of WO2011047797.

[0168] The polymer mixture was drawn after extrusion over a first take-off roll and a further roll trio, cooled and solidified, then longitudinally drawn, transversely drawn and fixed, wherein the following conditions were selected in particular: [0169] extrusion: extrusion temperature 245 C. [0170] chilling roll: temperature 125 C., [0171] discharge speed: 1.5 m/min (dwell time on the take-off roll: 55 sec) [0172] longitudinal extension: preheating roll: 92 drawing roll T=90 C. [0173] longitudinal drawing by the factor of 3.6 [0174] transverse drawing: heating field T=145 C. [0175] drawing field T=145 C. [0176] transverse drawing by the factor of 4.8 [0177] convergence: 13%

[0178] A roll of 1500 m continuous length was produced without tears. The porous film thus produced was approximately 30 m thick and had a density of 0.33 g/cm.sup.3 and had a uniform white-opaque appearance. The porosity was 665% and the Gurley value 160 s. SEM images of the surface of side A showed no TiO2 agglomerates and no particles with a particle size >1 m on an examined area of 10 mm.sup.2.

Film Example 2

[0179] A two-layer film as described in film example 1 was produced. In contrast to film example 1, the discharge speed was increased to 2.5 m/min. The composition of the layers and the other method conditions remained the same. In spite of the increased discharge speed, 800 m of continuous length were produced without tears. Here, the thickness reduced to 20 m. In spite of the shorter dwell time on the take-off roll, the Gurley value reduced surprisingly to approximately 140 seconds. In this film as well, no TiO2 agglomerates were identified on the side A by means of SEM, and no particles with a particle size >1 m were identified over an area of 10 mm.sup.2.

Film Example 3

[0180] A film as described in film example 1 was produced. In contrast to film example 1, the layer B now had the same composition as layer A. The composition of layer A and the method conditions remained the same. A single-layer film was thus produced. The thickness of the film was 31 m and the Gurley value reduced surprisingly to less than 100 seconds. This composition as well demonstrated very good fault-free extent, and a roll of 2000 m continuous length was thus produced. Neither side of the film showed any TiO2 agglomerates by means of SEM, and no particles with a particle size >1 m were identified over an area of 10 mm.sup.2.

Film Example 4

[0181] A single-layer film as described in film example 3 with 24% by weight of TiO2 was produced. The discharge speed was (as in film example 2) increased to 2.5 m/min. The (same) composition of layers A and B and the other method conditions remained the same. With the increased discharge speed of 2.5 m/min, a roll of 1000 m continuous length without tears was produced. Here, the thickness reduced to 20 m and the Gurley value remained, as in example 3, surprisingly less than 100 seconds. In this film no agglomerates were identified on either side by means of SEM, and no particles with a particle size >1 m were identified over an area of 10 mm.sup.2.

Film Example 5

[0182] A film as described in film example 3 with 24% by weight of TiO2 was produced. In contrast to film example 3, the polypropylene mixture now contained no nucleating agent and thus had the following composition:

approx. 60% by weight propylene homopolymer (PP) with an n-heptane-soluble proportion of 4.5% by weight (based on 100% PP) and a melting point of 165 C.; and a melt flow index of 3.2 g/10 min at 230 C. and 2.16 kg load (DIN 53 735) and
approx. 40% by weight propylene ethylene block copolymer with an ethylene proportion of approx. 5% by weight based on the block copolymer and a melt flow index (230 C. and 2.16 kg) of 6 g/10 min

[0183] Otherwise, the composition of the layer and the composition of the TiO2 batch and the method conditions were not changed compared to example 3.

[0184] Here as well, a roll of 1000 m continuous length without tears could be produced. The thickness of the film was 28 m. Here, the Gurley value remained, as in film example 3, surprisingly less than 100 seconds. In this film as well, no agglomerates were identified in either layer by means of SEM, and no particles with a particle size >1 m were identified over an area of 10 mm.sup.2.

Film Example 6

[0185] A two-layer film as described in film example 1 was produced. In contrast to film example 1 the concentration of the TiO2 batch in layer A was increased to 60% and the proportion of the polypropylene mixture was reduced to 40%, such that 36% by weight of TiO2 was present in the layer A. The composition of layer B and the method conditions remained the same. This composition as well demonstrated very good fault-free extent, and a roll of 1000 m continuous length was produced. The thickness of the film was 27 m and the Gurley value reduced surprisingly to less than 100 seconds. Side A of the film did not reveal, by SEM, any agglomerates >1 m over an area of 10 mm.sup.2. However, one particle with a particle size of approx. 1.2 m was identified.

Film Example 7

[0186] A two-layer film was produced under the same conditions and with the same formulation as film example 2. However, the discharge speed was increased to 5 m/min and therefore the end film speed was increased to 19 m/min. In order to ensure production of a film of constant thickness under these conditions, the extrusion throughput was additionally doubled. This composition also demonstrated a very good fault-free extent at the higher process speed, and a roll with 1000 m continuous length was produced. The thickness of the film was 27 m and the Gurley value increased compared to example 2 to 170 seconds, wherein the -content measured on the preliminary film reduced slightly to 57%. Side A of the film did not reveal any agglomerates in SEM, and no particles with a particle size >1 m were identified over an area of 10 mm.sup.2.

Film Example 8

[0187] A two-layer film was produced under the same conditions and with the same formulation as film example 2. However, the discharge speed was increased to 7.5 m/min and therefore the end film speed was increased to 28 m/min. In order to ensure production of a film of constant thickness under these conditions, the extrusion throughput was additionally doubled. This composition also demonstrated a very good fault-free extent at the higher process speed, and a roll with 1000 m continuous length was produced. The thickness of the film was 24 m and the Gurley value increased compared to example 7 to 198 seconds, wherein the 3-content measured on the preliminary film reduced slightly to 54%. Side A of the film did not reveal any agglomerates in SEM, and no particles with a particle size >1 m were identified over an area of 10 mm.sup.2.

Film Example 9

[0188] A two-layer film was produced under the same conditions and with the same formulation as film example 2 was produced. However, the discharge speed was increased to 10 m/min and therefore the end film speed was increased to 37 m/min. In order to ensure production of a film of constant thickness under these conditions, the extrusion throughput was additionally doubled. This composition also demonstrated a very good fault-free extent at the higher process speed, and a roll with 1000 m continuous length was produced. The thickness of the film was 24 m and the Gurley value increased compared to example 8 to 222 seconds, wherein the -content measured on the preliminary film reduced slightly to 51%. Side A of the film did not reveal any agglomerates in SEM, and no particles with a particle size >1 m were identified over an area of 10 mm.sup.2.

Film Example 10

[0189] A two-layer film was produced under the same conditions as film example 2. However, in layer A and layer B the propylene-ethylene block copolymer was replaced by an increase of the proportion of the propylene homopolymer (PP).

[0190] This composition also demonstrated a very good fault-free extent in spite of the absence of the block copolymer, and a roll with 1000 m continuous length was produced. The thickness of the film was 27 m and the Gurley value was 170 seconds. This composition also demonstrated very good fault-free extent, and a roll of 1000 m continuous length was produced. Side A of the film did not reveal any agglomerates in SEM, and no particles with a particle size >1 m were identified over an area of 10 mm.sup.2.

Comparative Example 1

[0191] A film was produced under the same conditions as described in film example 1. In contrast to film example 1, the same mixture as for layer B was used for layer A and therefore the addition of TiO2 was omitted. The composition of layer B and also the method conditions remained the same. A single-layer film was thus produced. The thickness of the film was 29 m and the Gurley value was 200 seconds.

Comparative Example 2

[0192] A film was produced under the same conditions as described in comparative example 1. In contrast to comparative example 1, the discharge speed was increased here to 2.5 m/min. With the increased discharge speed 500 m of continuous length without tears were produced. Here, the thickness reduced to 20 m and the Gurley value increased to 280 seconds.

Comparative Example 3

[0193] A two-layer film was produced under the same conditions as described for film example 1. In contrast to film example 1, the composition of the batch of layer A was changed. The TiO2 was replaced by an Al2O3 with a mean particle diameter of 3 m. The composition of the polypropylene mixture of layer A, the composition of layer B, and the method conditions remained the same. However, it was not possible to produce a film on account of numerous tears.

Comparative Example 4

[0194] A two-layer film was produced under the same conditions as described for film example 1. However, the TiO2 instead of a batch was incorporated into the extruder by direct metered addition. Tears were encountered frequently during the production process. The few films produced in principle demonstrated the same properties as the films according to example 1. Side A of the film showed a number of agglomerates in SEM with a size of from 1 to 3 m over an area of 10 mm.sup.2.

TABLE-US-00002 TABLE 1 CE1 CE2 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Particle material / / TiO2 TiO2 TiO2 TiO2 TiO2 TiO2 Mean particle nm 200 200 200 200 200 200 size Particle shape spherical spherical spherical spherical spherical spherical Nucleator conc. % 0.04 0.04 0.04 0.04 0.04 0.04 0 0.04 Film structure single- single- two-layer two-layer single- single- single- two-layer layer layer A/B A/B layer layer layer A/B TiO2 conc. % by 0 24 24 24 24 24 24 36 in layer A weight Ratio A/B 1:2 1:2 1:2 Length in metres m 500 500 1600 800 2000 1000 1000 800 without tears Discharge speed m/min 1.5 2.5 1.5 2.5 1.5 2.5 1.5 1.5 Particles with a 0 0 0 0 0 1 size >1 m over 10 mm.sup.2 Process speed m/min 5.92 9.25 5.92 9.25 5.92 9.25 5.92 5.92 Thickness m 29 20 30 20 31 20 28 27 Density Kg/m.sup.3 0.32 0.33 0.34 0.35 0.35 0.37 0.37 0.33 Porosity % 60.5 59.5 58.5 57.5 57.5 55.5 55.5 59.5 Maximum pore nm 65 63 79 76 146 152 146 84 size Mean pore size nm 57 54 58 57 119 109 112 67 Gurley s/100 cm.sup.3 199 280 160 138 91 98.9 99.9 144 -content % 66 64 63 64 66 62 61 66 preliminary film Ex. 7 Ex. 8 Ex. 9 Ex. 10 Particle material TiO2 TiO2 TiO2 TiO2 Mean particle nm 200 200 200 200 size Particle shape spherical spherical spherical spherical Nucleator conc. % 0.04 0.04 0.04 0.04 Film structure two-layer two-layer two-layer two-layer A/B A/B A/B A/B TiO2 conc. % by 24 24 24 24 in layer A weight Ratio A/B 1:2 1:2 1:2 1:21:2 Length in metres m 1000 1000 1000 1000 without tears Discharge speed m/min 5 7.5 10 2.5 Particles with a 0 0 0 0 size >1 m over 10 mm.sup.2 Process speed m/min 18.5 27.75 37.00 9.25 Thickness m 27 24 21 30 Density Kg/m.sup.3 0.37 0.39 0.41 0.34 Porosity % 55.5 53.5 51.5 58.5 Maximum pore nm 64 66 69 76 size Mean pore size nm 56 57 57 57 Gurley s/100 cm.sup.3 55 53 50 72 -content % 170 196 222 170 preliminary film

[0195] Production of the Dispersions:

[0196] Binder-Particle Dispersion 1:

[0197] 1 g of nanoscale TiO2 (Aeroxide TiO2 P25 from Evonik) was first dispersed in 9 g of water to obtain an aqueous 10% by weight particle-containing aqueous dispersion. 5 g of a binder dispersion were then added to this particle dispersion. The two dispersions were mixed with one another by stirring. The binder dispersion was an aqueous acrylate dispersion with an acrylate proportion of 20% by weight (Neocryl FL-715 in H2O from DSM Neoresins). 15 g of the binder-particle dispersion were then added to and mixed with 1.5 g isopropanol for improved wetting of the separator. In this way, 16.5 g of the finished particle-binder dispersion were obtained for the coating.

[0198] Binder-Particle Dispersion 2:

[0199] A dispersion as described in dispersion example 1 was produced. In contrast to dispersion example 1, 2 g of nanoscale TiO2 (Aeroxide TiO2 P25 from Evonik) were dispersed in 8 g of water to obtain an aqueous 20% by weight particle-containing dispersion. 5 g of the aqueous acrylate dispersion (Neocryl FL-715 in H2O from DSM Neoresins with an acrylate proportion of 20% by weight) were then added to and stirred together with this particle dispersion. Another 15 g of the binder-particle dispersion were then mixed with 1.5 g isopropanol. In this way, 16.5 g of the finished particle-binder dispersion were obtained for the coating.

[0200] Binder-Particle Dispersion 3:

[0201] A dispersion as described in dispersion example 1 was produced. In contrast to dispersion example 1, 3 g of nanoscale TiO2 (Aeroxide TiO2 P25 from Evonik) were dispersed in 7 g of water to obtain an aqueous 30% by weight particle-containing dispersion. 5 g of the aqueous acrylate dispersion (Neocryl FL-715 in H2O from DSM Neoresins with an acrylate proportion of 20% by weight) were then added to and stirred together with this particle dispersion. Another 15 g of the binder-particle dispersion were then mixed with 1.5 g isopropanol. In this way, 16.5 g of the finished particle-binder dispersion were obtained for the coating.

[0202] Binder-Particle Dispersion 4:

[0203] 1 g of Al2O3 particles (AKP-3000 from Sumimoto, D50 value: 0.66 m) was first dispersed in 9 g of water to obtain an aqueous 10% by weight particle-containing dispersion. 2 g of a binder dispersion were then added to this particle dispersion and the mixture was stirred. The binder dispersion was an aqueous acrylate dispersion with an acrylate proportion of 20% by weight (Neocryl FL-715 in H2O from DSM Neoresins). 12 g of the binder-particle dispersion were then added to and mixed with 1.5 g isopropanol. In this way, 13.5 g of the finished dispersion were obtained.

[0204] Binder-Particle Dispersion 5:

[0205] A dispersion as described in dispersion example 4 was produced. In contrast to dispersion example 4, 2 g of sub-m Al2O3 particles (AKP-3000 from Sumimoto, D50 value: 0.66 m) were dispersed in 8 g of water to obtain an aqueous 20% by weight particle-containing dispersion. 2 g of the aqueous acrylate dispersion (acrylate proportion of 20% by weight Neocryl FL-715 in H2O from DSM Neoresins) were then added to and stirred together with this particle dispersion. 12 g of the binder-particle dispersion were then mixed with 1.5 g isopropanol. In this way, 13.5 g of the finished particle-binder dispersion were obtained.

[0206] Binder-Particle Dispersion 6:

[0207] 1 g of boehmite (A12020H) particles (Dispersal 40 from Sasol. D50: 350 nm) was first dispersed in 9 g of water to obtain an aqueous 10% by weight particle-containing dispersion. 2 g of the aqueous acrylate dispersion (acrylate proportion of 20% by weight Neocryl FL-715 in H2O from DSM Neoresins) were then added to and mixed with this particle dispersion. 12 g of the binder-particle dispersion were then mixed with 1.5 g isopropanol. In this way, 13.5 g of the finished particle-binder dispersion were obtained.

[0208] Binder-Particle Dispersion 7:

[0209] A dispersion as described in dispersion example 4 was produced. In contrast to dispersion example 4, 2 g of boehmite particles (Dispersal 40 from Sasol. D50: 350 nm) were dispersed in 8 g of water to obtain an aqueous 20% by weight particle-containing dispersion. 2 g of the aqueous acrylate dispersion (acrylate proportion of 20% by weight Neocryl FL-715 in H2O from DSM Neoresins) were then added to and stirred together with this particle dispersion. 12 g of the binder-particle dispersion were then mixed with 1.5 g isopropanol. In this way, 13.5 g of the finished particle-binder dispersion were obtained.

[0210] Production of Coated Films:

[0211] Table 2:

[0212] For the described coating examples 1 to 7 described hereinafter, the film according to film example 4 was coated with the binder-particle dispersions 1 to 7. The results are summarised in Table 2.

Coating Example 1

[0213] Samples of DIN A4 size were cut from the particle-containing film from film example 4 and fixed on a glass plate. The dispersion (approx. 5 to 10 g) from dispersion example 1 was then applied to the surface of the particle-containing film using a hand-held doctor blade. The film was then dried for 5 min at 70 C. in a drying cabinet and was then examined in respect of its properties. After drying, a coating weight of approx. 2 g/m.sup.2 was determined for the ceramic coating by means of weighing. The thickness of the separator increased after coating from 20 m to 22 m. The Gurley value increased from 98 to 165 s. The coating demonstrated excellent adhesion in the Tesa test.

Coating Example 2

[0214] The dispersion 2 was applied to the surface of the particle-containing film using a hand-held doctor blade as described in coating example 1. The film was then dried for 5 min at 70 C. in a drying cabinet. After the drying, a coating weight of approx. 2 g/m.sup.2 was determined for the ceramic coating. The thickness of the separator increased after coating from 20 m to 22.5 m. The Gurley value increased from 98 to 142 s. The coating demonstrated very good adhesion in the Tesa test.

Coating Example 3

[0215] The dispersion 3 was applied to the surface of the particle-containing film using a hand-held doctor blade as described in coating example 1. The film was then dried for 5 min at 70 C. in a drying cabinet. After the drying, a coating weight of approx. 2 g/m.sup.2 was determined for the ceramic coating. The thickness of the separator increased after coating from 20 m to 22 m. The Gurley value increased from 98 to 123 s. The coating demonstrated very good adhesion in the Tesa test.

Coating Example 4

[0216] The dispersion 4 was applied to the surface of the particle-containing film using a hand-held doctor blade as described in coating example 1. The film was then dried for 5 min at 70 C. in a drying cabinet before it was examined. After the drying, a coating weight of approx. 2.5 g/m.sup.2 was determined for the ceramic coating. The thickness of the separator increased after coating from 20 m to 22.5 m. The Gurley value increased from 98 to 159 s. The coating demonstrated excellent adhesion in the Tesa test.

Coating Example 5

[0217] The dispersion 5 was applied to the surface of the particle-containing film using a hand-held doctor blade as described in coating example 1. The film was then dried for 5 min at 70 C. in a drying cabinet before it was examined further. After the drying, a coating weight of approx. 2.5 g/m.sup.2 was determined for the ceramic coating. The thickness of the separator increased after coating from 20 m to 23 m. The Gurley value increased from 98 to 138 s. The coating demonstrated good adhesion in the Tesa test.

Coating Example 6

[0218] The dispersion 6 was applied to the surface of the particle-containing film using a hand-held doctor blade as described in coating example 1. The film was then dried for 5 min at 70 C. in a drying cabinet before it was examined further. After the drying, a coating weight of approx. 2.5 g/m.sup.2 was determined for the ceramic coating. The thickness of the separator increased after coating from 20 m to 23 m. The Gurley value increased from 98 to 144 s. The coating demonstrated very good adhesion in the Tesa test.

Coating Example 7

[0219] The dispersion 7 was applied to the surface of the particle-containing film using a hand-held doctor blade as described in coating example 1. The film was then dried for 5 min at 70 C. in a drying cabinet before it was examined further. After the drying, a coating weight of approx. 2.5 g/m.sup.2 was determined for the ceramic coating. The thickness of the separator increased after coating from 20 m to 22.5 m. The Gurley value increased from 98 to 128 s. The coating demonstrated good adhesion in the Tesa test.

TABLE-US-00003 TABLE 2 Binder-particle dispersions 1 to 7 on film example 4 Coating Coating Coating Coating Coating Coating Coating example example example example example example example 1 2 3 4 5 6 7 Binder Acrylate Neocryl FL-175 in H2O (DSM neoresins) Initial weight of binder disp. [g] 5 5 5 2 2 2 2 Proportion of binder in binder disp. [%] 20 20 20 20 20 20 20 Ceramic Aeroxide TiO2 P25 in H2O Sumimoto AKP 3000 Boehmite Dispersal 40 Initial weight of ceramic disp. [g] 10 10 10 10 10 10 10 Proportion of ceramic in ceramic disp. [%] 10 20 30 10 20 10 20 Wetting agent Isopropanol Initial weight of wetting agent [g] 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Total dispersion [g] 16.5 16.5 16.5 13.5 13.5 13.5 13.5 % by weight acrylate in coating disp. 6.06 6.06 6.06 2.96 2.96 2.96 2.96 % by weight particles in coating disp. 6.06 12.12 18.18 7.41 14.81 7.41 14.81 Ceramic:binder ratio 1:1 2:1 3:1 ~72:28 ~83:17 ~72:28 -83:17 Weight per unit area [g/m.sup.2] 10.8 11.08 10.88 10.52 11.68 11.56 11.6 Coating weight [g/m.sup.2] 2 2 2 2.5 2.5 2.5 2.5 Thickness [m] 22 22.5 22 22.5 23 23 23 Gurley [sec/100 cm.sup.3] 165 142 123 159 138 144 128 Adhesion good good good good good good good

[0220] Table 3

[0221] For comparative examples 1 to 7 (Table 3), the film according to film comparative example 2 was coated with the binder-particle dispersions 1 to 7. The results are summarised in Table 3.

[0222] Film comparative example 2 with dispersions 1 to 7: Seven samples of DIN A4 size were cut from the film according to film comparative example 2 and fixed on a glass plate. 5 to 10 g of each of the dispersions from dispersion examples 1 to 7 were then applied to the surface of the film according to comparative example 2 using a hand-held doctor blade. The films thus coated were then dried for 5 min at 70 C. in a drying cabinet and then examined in respect of their properties. The coating weight after drying, the thickness and the Gurley value and the adhesion of the coated film were examined. The results are summarised in Table 3.

TABLE-US-00004 TABLE 3 Dispersion examples 1 to 7 on film according to comparative example 2 Coating Coating Coating Coating Coating Coating Coating example example example example example example example 1 2 3 4 5 6 7 Binder Acrylate Neocryl FL-175 in H2O (DSM neoresins) Initial weight of binder disp. [g] 5 5 5 2 2 2 2 Proportion of binder in binder disp. [%] 20 20 20 20 20 20 20 Ceramic Aeroxide TiO2 P25 in H2O Sumimoto AKP 3000 Boehmite Dispersal 40 Initial weight of ceramic disp. [g] 10 10 10 10 10 10 10 Proportion of ceramic in ceramic disp. [%] 10 20 30 10 20 10 20 Wetting agent Isopropanol Initial weight of wetting agent [g] 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Total dispersion [g] 16.5 16.5 16.5 13.5 13.5 13.5 13.5 % by weight acrylate in coating disp. 6.06 6.06 6.06 2.96 2.96 2.96 2.96 % by weight particles in coating disp. 6.06 12.12 18.18 7.41 14.81 7.41 14.81 Ceramic:binder ratio 1:1 2:1 3:1 ~72:28 ~83:17 ~72:28 ~83:17 Weight per unit area [g/m.sup.2] 10.8 11.08 10.88 10.52 11.68 11.56 11.6 Coating weight [g/m.sup.2] 2 2 2 2.5 2.5 2.5 2.5 Thickness [m] 22 22.5 22 22.5 23 23 23 Gurley [sec/100 cm.sup.3] 665 620 580 523 538 585 553 Adhesion poor good good poor good good good

[0223] Table 4

[0224] For examples 1 to 10 of Table 4, the film according to film examples 1 to 10 was coated with the binder-particle dispersion 3. The results are summarised in Table 4.

[0225] Examples 1 to 10 with dispersion 3 on film examples 1 to 10: Samples of DIN A4 size were cut from the films according to film examples 1 to 10 and fixed on a glass plate. The dispersion according to dispersion example 3 was then applied to the surface of these film samples 1 to 10 using a hand-held doctor blade. In the case of the films according to film examples 1, 2 and 6 to 10, the surface of the particle-containing layer (layer A) was coated. The films thus coated were then dried for 5 min at 70 C. in a drying cabinet and then examined in respect of their properties. The coating weight after drying, the thickness and the Gurley value and the adhesion of the coated film were examined. The results are summarised in Table 4.

TABLE-US-00005 TABLE 4 Dispersion according to example 3: 20% acrylate binder + 30% TiO2 particles (acrylate Neocryl FL-715 DSM neoresins) in water with isopropanol Dispersion example 3 on films according to examples 1 to 10 Film Film Film Film Film Film Film Film Film Film example example example example example example example example example example 1 2 3 4 5 6 7 8 9 10 Thickness [m] 30 20 31 20 28 27 27 24 21 30 Density [kg/m.sup.3] 0.34 0.35 0.35 0.37 0.37 0.33 0.37 0.39 0.41 0.34 Porosity [%] 58.5 57.5 57.5 55.5 55.5 59.5 55.5 53.5 51.5 58.5 Maximum pore size [nm] 79 76 146 152 146 84 64 66 69 76 Mean pore size [nm] 58 57 119 109 112 67 56 57 57 57 Gurley [s/100 cm.sup.3] before coating 160 138 91 98.9 99.9 144 170 196 222 170 -content preliminary film [%] 63 64 66 62 61 66 55 53 50 72 Values after coating Weight per unit area [g/m.sup.2] 12.4 9.1 12.73 9.1 11.74 11.41 11.41 10.42 9.43 12.4 Application weight [g/m.sup.2] 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Thickness [m] 32 22 33 22 30 29 29 26 23 32 Gurley of coated film [sec/100 cm.sup.3] 195 188 146 123 144 144 260 296 310 224 Adhesion good good good good good good good good good good