HIGH-POROSITY SEPARATOR FILM WITH COATING AND SHUT DOWN FUNCTION

Abstract

The invention concerns a biaxially orientated, single- or multi-layered porous film which comprises at least one porous layer and this layer contains at least one propylene polymer and polyethylene; (i) the porosity of the porous film is 30% to 80%; and (ii) the permeability of the porous film is <1000 s (Gurley number);

characterized in that (iii) the porous film comprises an inorganic, preferably ceramic coating; and (iv) the coated porous film has a Gurley number of <1500 s; and (v) the coated porous film has a Gurley number of >6000 s when it is heated for 5 minutes to over 140 C.

The coated, porous film has dual safety features. Furthermore, the invention also concerns a process for the production of a film of this type as well as its use in high energy or high performance systems, in particular in lithium, lithium ion, lithium-polymer and alkaline-earth batteries.

Claims

1-33. (canceled)

34. A biaxially orientated, single- or multi-layered porous film which comprises at least one porous layer and this layer contains at least one propylene polymer and polyethylene and at least one -nucleation agent; (I) the porosity of the porous film is 30% to 80%; and (II) the permeability of the porous film is <1000 s (Gurley number); wherein (III) the porous film comprises an inorganic coating applied directly to the porous layer without pretreatment of the film with primers; and no post-treatment of the surface of the film with corona, plasma or flame treatment; and (IV) the coated porous film has a Gurley number of <1500 s; and (V) the coated porous film has a Gurley number of >6000 s when it is heated for 5 minutes to over 140 C. and wherein the porosity of the film is obtained by the pathway via transformation of beta crystals of polypropylene to alpha crystals of polypropylene, wherein the film contains A. 50% to 85% by weight of propylene homopolymer, and B. 15% to 50% by weight of propylene block copolymer and 50 to 10000 ppm of (3-nucleation agent and wherein the inorganic coating consists of inorganic particles and a final consolidating binder selected from the group formed by binders based on polyvinylidene dichloride (PVDC), polyacrylates, polymethacrylates, polyethyleneimines, polyesters, polyamides, polyimides, polyurethanes, polycarbonates, silicate binders, polymers from the halogenated polymer class, and blends thereof and the amount of the final consolidating binder is from is 0.5 g/m.sup.2 to 20 .sub.g/m2.sub..

35. The film as claimed in claim 34, wherein the porosity is produced by transformation of -crystalline polypropylene upon drawing the film.

36. The film as claimed in claim 35, wherein the -nucleation agent is a calcium salt of pimelic acid and/or suberic acid and/or a nanoscale iron oxide.

37. The film as claimed in claim 34, wherein the density of the film is in the range 0.1 to 0.5 g/cm.sup.3.

38. The film as claimed in claim 34, wherein the thickness of the film is 10 to 100 m.

39. The film as claimed in claim 34, wherein the propylene polymers are not produced using metallocene catalysts.

40. The film as claimed in claim 34, wherein the polyethylene is present in quantities of at least 5% by weight with respect to the propylene polymers and/or propylene block copolymers present.

41. The film as claimed in claim 34, wherein the polyethylene is a HDPE or MDPE with a melting peak in the range 115 C. to 140 C.

42. The film as claimed in claim 41, wherein the HDPE has a MFI (50 N/190 C.) of more than 0.1 to 50 g/10 min measured using DIN 53 735 and a viscosity number, measured using DIN 53 728 part 4 or ISO 1191, in the range 100 to 450 cm.sup.3/g, a density, measured at 23 C. in accordance with DIN 53 479, method A or ISO 1183, in the range >0.94 to 0.97 g/cm.sup.3 and a melting point, measured using DSC (maximum of melting curve, heating rate 20 C./min), between 120 C. and 145 C.

43. The film as claimed in claim 41, wherein the MDPE has a MFI (50 N/190 C.) of more than 0.1 to 50 g/10 min, measured using DIN 53 735, a density, measured at 23 C. in accordance with DIN 53 479, method A or ISO 1183, in the range >0.925 to 0.94 g/cm.sup.3 and a melting point, measured using DSC (maximum of melting curve, heating rate 20 C./min) between 115 C. and 130 C.

44. The film as claimed in claim 34, wherein the inorganic coating comprises ceramic particles with a particle size, expressed as the D50 value, in the range 0.05 to 15 m.

45. The film as claimed in claim 44, wherein the ceramic particle comprises an electrically non-conducting oxide of the metals Al, Zr, Si, Sn, Ti and/or Y.

46. The film as claimed in claim 44, wherein the ceramic particles comprise a) particles based on oxides of silicon with the molecular formula SiO.sub.2, b) mixed oxides with the molecular formula AlNaSiO.sub.2, or c) oxides of titanium with the molecular formula TiO.sub.2, wherein they may be present in the crystalline, amorphous or mixed form.

47. The film as claimed in claim 44, wherein the ceramic particles have a melting point of at least 160 C.

48. The film as claimed in claim 34, wherein the thickness of the inorganic ceramic coating is 0.5 m to 80 m.

49. The film as claimed in claim 34, wherein the quantity of inorganic coating which is applied is 0.5 g/m.sup.2 to 80 g/m.sup.2.

50. The film as claimed in claim 44, wherein the quantity ceramic particles which is applied is 0.4 g/m.sup.2 to 60 g/m.sup.2.

51. The film as claimed in claim 34, wherein the inorganic coating further comprises a final consolidating binder based on polyvinylidene dichloride (PVDC).

52. The film as claimed in claim 34, wherein the inorganic coating comprises ceramic particles with a minimum compressive strength of 100 kPa.

53. The film as claimed in claim 34, wherein the inorganic coating comprises 98% by weight to 50% by weight of ceramic particles and 2% by weight to 50% by weight of at least one terminally consolidating binder selected from the group formed by binders based on polyvinylidene dichloride (PVDC), polyacrylates, polymethacrylates, polyethyleneimines, polyesters, polyamides, polyimides, polyurethanes, polycarbonates, silicate binders, polymers from the halogenated polymer class, and blends thereof.

54. A separator in performance systems which comprises the film as claimed in claim 34.

55. A system which comprise the film as claimed in claim 34.

56. The system as claimed in claim 55, wherein the system has energy densities of 350 to 400 Wh/L.

57. The film as claimed in claim 34, which further comprises an additional polyolefin which is selected from the group consisting of: a) random copolymers of ethylene and propylene with an ethylene content of 20% by weight or less, b) random copolymers of propylene with C.sub.4-C.sub.8 olefins, with an olefin content of 20% by weight or less, and c) terpolymers of propylene, ethylene and butylene with an ethylene content of 10% by weight or less and with a butylene content of 15% by weight or less.

58. The film as claimed in claim 34, wherein the -nucleation agent is present in an amount from 50 to 5000 ppm.

59. The film as claimed in claim 34, wherein the -nucleation agent is present in an amount from 50 to 2000 ppm.

60. The film as claimed in claim 57, wherein the -nucleation agent is present in an amount from 50 to 2000 ppm.

61. The film as claimed in claim 34, wherein the porosity of the porous film is 50% to 70%.

62. The film as claimed in claim 60, wherein the porosity of the porous film is 50% to 70%.

63. The film as claimed in claim 34, wherein the porous film to be coated has a density in the range 0.1 to 0.6 g/cm.sup.3 and has a bubble point not over 350 nm and has a mean pore diameter in the range 50 to 100 nm.

64. The film as claimed in claim 62, wherein the porous film to be coated has a density in the range 0.2 to 0.5 g/cm.sup.3 and has a bubble point from 50 to 300 nm and has a mean pore diameter in the range 60-80 nm.

65. The film as claimed in claim 34, wherein the porous film to be coated has a roughness Rz (ISO 4287, roughness measurement, one line, amplitude parameter roughness profile, Leica DCM3D instrument, Gauss filter, 0.25 mm) which is rom 0.3 m to 6 m.

66. The film as claimed in claim 64, wherein the porous film to be coated has a roughness Rz (ISO 4287, roughness measurement, one line, amplitude parameter roughness profile, Leica DCM3D instrument, Gauss filter, 0.25 mm) which is rom 0.5 m to 3.5 m.

67. The film as claimed in claim 34, wherein the final consolidating binder selected from the group formed by binders based on polyacrylates, polymethacrylates, polyethyleneimines, polyesters, polyamides, polyimides, polyurethanes, polycarbonates, silicate binders, polymers from the halogenated polymer class, and blends thereof.

Description

EXAMPLES

[0130] Three different inorganic coatings were made up for the inorganic, preferably ceramic coating. To this end, a commercially available PVDC coating (DIOFAN A 297) was used as a binder with the inorganic particles; water and isopropanol were added in a manner so as to adjust the viscosity of the coating to allow uniform distribution of the DIOFAN A 297 onto the polypropylene film using a wire applicator blade. In addition, the fraction of the PVDC was selected so that on the one hand, after drying off the solvent component, an abrasion-resistant coating was formed and on the other hand, there was still enough open (coating-free) zones between the ceramic particles for an open, air-permeable porous structure to be formed. The composition of the coating mass is shown in detail in Table 1. The organic particles were spherical silicate particles (Zeeospheres, 3M) and TiO.sub.2 particles.

Production of Films Mentioned in the Example

[0131]

TABLE-US-00001 TABLE 1 Composition of inorganic coatings Particle, % by Water, % by Particle Particle size weight weight Isopropanol, % PVDC coating Coating 1 Spherical 1-10 m 65 13 8 13 silicate (SiO.sub.2) Coating 2 Spherical 1-10 m 58 17 8 17 silicate (SiO.sub.2) Coating 3 TiO.sub.2 100-300 nm 47 23 12 18

Film Example 1

[0132] In the extrusion process, a single ply pre-film was extruded from a slot die at an extrusion temperature of 240 C. to 250 C. This pre-film was first taken off onto a chill roller and cooled down. The pre-film was then orientated longitudinally and transversely and finally fixed. The film had the following composition:

[0133] Approximately 60% by weight of highly isotactic propylene homopolymerisate (PP) with a 13C-NMR isotacticity of 97% and an n-heptane soluble fraction of 2.5% by weight (relative to 100% PP) and a melting point of 165 C.; and a melt flow index of 2.5 g/10 min at 230 C. and 2.36 kg load (DIN 53 735); and approximately 20% by weight of HDPE (high density polyethylene) with a density of 0.954 (ISO 1183) and an MFI of 0.4 g/10 rain at; 190 C. and 2.16 kg load (ISO 1133/D) or 27 g/10 min at 190 C. and 21.6 kg load (ISO 1333/G) and a melting point of 130 C. (DSC: peak at 10 C./min heating rate); the melt range began at 123 C., approximately 20% by weight of propylene-ethylene block copolymerisate with an ethylene content of 5% by weight with respect to the block copolymer and an MFI (230 C. and 2.16 kg) of 6 g/10 min and a melting point (DSC) of 165 C.; and

[0134] 0.04% by weight of Ca pimelate as -nucleation agent.

[0135] The film additionally contained the usual small quantities of stabilizer and neutralising agent. After extrusion, the molten polymer blend was taken off and solidified over a first take-off roller and a further roller trio, then drawn longitudinally, transversely and fixed; details of the conditions are as follows:

[0136] Extrusion: extrusion temperature 235 C.

[0137] Take-off roller: temperature 125 C.,

[0138] Take-off speed: 4 m/min

[0139] Longitudinal drawing: drawing roller T=90 C.

[0140] Longitudinal drawing: factor 3.0

[0141] transverse drawing: heating zones T=125 C.

[0142] Drawing zones: T=125 C.

[0143] Transverse drawing: factor 5.0

[0144] Fixing: T=125 C.

[0145] The porous film produced in this manner was about 25 m thick, had a density of 0.38 g/cm.sup.3 and had an even, white-opaque appearance.

Film Example 2

[0146] In the extrusion process, a single ply pre-film was extruded from a slot die at an extrusion temperature of 240 to 250 C. The extrusion throughput was increased by 30% compared with film example 1. This pre-film was first taken off onto a chill roller and cooled down. The pre-film was then orientated longitudinally and transversely and finally fixed. The film had the following composition:

[0147] Approximately 80% by weight of highly isotactic propylene homopolymerisate (PP) with a .sup.13C-NMR isotacticity of 97% and an n-heptane soluble fraction of 2.5% by weight (relative to 100% PP) and a melting point of 165 C.; and a melt, flow index of 2.5 g/10 min at 230 C. and 2.16 kg load (Dill 53 735); and approximately 20% by weight of HDPE (high density polyethylene) with a density of 0.954 (ISO 1183) and an MFI of 0.4 g/10 min at 190 C. and 2.16 kg load (ISO 1133/D) or 27 g/10 min at 130 C. and 21.6 kg load (ISO 1333/G) and a melting point of 130 C. (DSC: peak at 10 C./min heating rate); the melt range began at 125 C. Further, the film contained 0.04% by weight of Ca pimelate as -nucleation agent.

[0148] The film additionally contained the usual small quantities of stabilizer and neutralising agent.

[0149] After extrusion, the molten polymer blend was taken off and solidified over a first take-off roller and a further roller trio, then drawn longitudinally, transversely and fixed; details of the conditions are as follows:

[0150] Extrusion: extrusion temperature 235 C.

[0151] Take-off roller: temperature 125 C., dwell time on take-off roller 60 sec

[0152] Longitudinal drawing: drawing roller T=90 C.

[0153] Longitudinal drawing: factor 3.0

[0154] Transverse drawing: heating zones T=125 C.

[0155] Drawing zones: T=125 C.

[0156] Transverse drawing: factor 5.0

[0157] Fixing: T=125 C.

[0158] The porous film produced in this way was about 30 m thick, had a density of 0.38 g/cm.sup.3 and had an even, white-opaque appearance. The Gurley number was 380 s. After the heat treatment in the oven at 135 C. for 5 min, the Gurley number was >9000 s/100 cm.sup.3.

Example 1

[0159] Silicate coating with the composition of coating 1 (Table 1) was manually applied using a wire applicator blade (wire diameter: 0.4 mm) to a microporous BOPP film with a shut down function (film example 1). Wetting of the film with the ceramic suspension was uniform. The coated film was then dried for one hour at 90 C. in a drying cabinet. After drying, the coating exhibited good adhesion to the film. Next, the coating weight, thickness of the coating layer and the permeability to air were determined using the Gurley number. Only a slight increase in the Gurley number was observed, from 360 s to 380 s.

Example 2

[0160] Silicate coating with the composition of coating 2 (Table 1) was manually applied using a wire applicator blade (wire diameter: 0.4 mm) to a microporous BOPP film with a shut down function (film example 1). After coating, wetting of the film with the ceramic suspension was uniform. After drying, the coating, as was the case for Example 2, exhibited better adhesion than in Example 5. The Gurley number was also substantially higher. The Gurley number was observed to have increased from 360 s to 570 s.

Example 3

[0161] Titanium oxide coating with the composition of coating (Table 1) was manually applied using a wire applicator blade (wire diameter: 0.4 mm) to a microporous BOPP film with a shut down function (film example 1). After coating, wetting of the film with the ceramic suspension was uniform. After drying, the coating exhibited good adhesion to the film. An increase in the Gurley number was observed, from 360 s to 460 s.

Example 4

[0162] Silicate coating with the composition of coating 1 (Table 1) was manually applied using a wire applicator blade (wire diameter: 0.7 mm) to a microporous BOPP film with a shut down function (film example 2). After coating, wetting of the film with the ceramic suspension was uniform. After drying, adhesion of the coating was good. The Gurley number increased from 380 s to 420 s.

Example 5

[0163] Titanium oxide coating with the composition of coating 3 (Table 1) was manually applied using a wire applicator blade (wire diameter: 0.7 mm) to a microporous BOPP film with a shut down function (film example 1). After coating, wetting of the film with the ceramic suspension was uniform. After drying, the coating exhibited good adhesion to the film. An increase in the Gurley number was observed, from 380 s to 510 s.

Example 6 (Comparative)

[0164] An attempt was made to manually apply the silicate coating with the composition of coating 1 (Table 1) to a commercially available microporous separator from Celgard (C200) as described in Example 1 using a wire applicator blade (wire diameter 0.4 mm). No wetting by the coating solution was observed and it flaked off again after drying.

Example 7 (Comparative)

[0165] An attempt was made to manually apply the silicate coating with the composition of coating 2 (Table 1) to the separator from Celgard (C200) as described in Example 2 using a wire applicator blade (wire diameter 0.4 mm). Again, no wetting by the coating solution, with an increased PVDC content, was observed and it flaked off again after drying.

Example 8 (Comparative)

[0166] An attempt was made to manually apply the silicate coating with the composition of coating 1 (Table 1) to another commercially available polyolefin separator from UBE as described in Example 1 using a wire applicator blade (wire diameter 0.4 mm). The coating solution exhibited no wetting and flaked off again after drying.

Example 9 (Comparative)

[0167] An attempt was made to manually apply the silicate coating with the composition of coating 2 (Table 1) to the polyolefin separator from UBE as described in Example 2 using a wire applicator blade (wire diameter 0.4 mm). Again, the coating with an increased PVDC content exhibited no wetting and flaked off again after drying.

Example 10 (Comparative)

[0168] An attempt was made to manually apply the silicate coating with the composition of coating 1 (Table 1) to a commercially available biaxially drawn polypropylene packaging film (GND 30 from Treofan) which, for the purposes of printability, had been treated by corona treatment to increase the surface tension compared with untreated PP films, in the manner of Example 1 using a wire applicator blade (wire diameter 0.4 mm). Again, the coating with an increased PVDC content exhibited no wetting and flaked off again after drying.

Example 11 (Comparative)

[0169] Coating 2, with the increased PVDC content, also exhibited no wetting and adhesion to the biaxially drawn polypropylene packaging film GND 30 from Treofan.

TABLE-US-00002 TABLE 2 Shut down Wire Gurley Gurley function diameter number number Gurley Layer Separator/ Coating applicator, before after number thickness Coating film type formula mm coating coating 5 min@ 135 C. coating/m weight/g/m.sup.2 Wetting Adhesion Ex 1 PBS 20 Coat 1 0.4 360 380 >5000s 37 53 yes yes Ex 2 PBS 20 Coat 2 0.4 360 570 >5000s 33 50 yes yes Ex 3 PBS 20 Coat 3 0.4 360 460 >5000s 35 59 yes yes Ex 4 PBS 30 Coat 1 0.7 380 420 >5000s 52 63 yes yes Ex 5 PBS 30 Coat 3 0.7 380 510 >5000s 52 63 yes yes Ex 6 (C) Celgard C Coat 2 0.4 660 >5000s None None 200 Ex 7 (C) Celgard C Coat 3 0.4 660 >5000s None None 200 Ex 8 (C) UBE 3014 Coat 2 0.4 580 >5000s None None Ex 9 (C) UBE 3014 Coat 3 0.4 580 >5000s None None Ex 10 (C) GND 30 Coat 2 0.4 None None Ex 11 (C) GND 30 Coat 3 0.4 None None