POROUS MEMBRANE WIPES AND METHODS OF MANUFACTURE AND USE

Abstract

A microporous membrane wipe and a method of using such microporous membrane wipe are disclosed. The microporous membrane wipe may be uniaxially or biaxially oriented microporous membrane. The uniaxially or biaxially oriented microporous membrane may be made from one or more block and/or impact copolymers of polyethylene and/or polypropylene. A method of using such a microporous membrane wipe for skin oil blotting is also disclosed. Further disclosed is a method of using such a microporous membrane wipe for cleaning a surface for the removal of fingerprints, smudges and the like, where such surfaces may include, for example, eyeglasses, electronics, cell phones, displays, optical devices, camera lenses, microscope lenses and other precision optics, and/or the like.

Claims

1-24 (canceled)

25. A microporous membrane wipe.

26. The microporous membrane wipe of claim 25 comprising: at least one layer of porous polymer film made by a dry-stretch process including the steps of: extruding a polymer into at least a single layer nonporous precursor, and biaxially stretching the nonporous precursor, the biaxial stretching including a machine direction stretching and a transverse direction stretching, the transverse direction stretching optionally including a simultaneous controlled machine direction relax, and having substantially round shaped pores, a porosity of about 40% to 90%, a ratio of machine direction tensile strength to transverse direction tensile strength in the range of about 0.5 to 5.0 and an Aquapore size of at least about 0.06 microns.

27. The microporous membrane wipe of claim 26, wherein the machine direction stretching of said biaxially stretching includes the step of transverse direction stretching with simultaneous machine direction stretching, and wherein said biaxially stretching optionally includes the step of transverse direction relax.

28. The microporous membrane wipe of claim 26, wherein said biaxially stretching of said nonporous precursor further includes an additional step of machine direction stretching.

29. The microporous membrane wipe of claim 26, wherein said dry-stretch process further includes the step of: machine direction stretching to form a porous intermediate prior to said biaxial stretching.

30. The microporous membrane wipe of claim 26, wherein said biaxially stretching of said nonporous precursor includes the machine direction stretching, an additional transverse direction stretching with simultaneous machine direction stretching, and an optional transverse direction relax.

31. The microporous membrane wipe of claim 26, wherein said dry-stretch process includes the steps of: machine direction stretching followed by said biaxial stretching including said transverse direction stretching with simultaneous controlled machine direction relax, a second transverse direction stretching with simultaneous machine direction stretching, followed by optional transverse direction relax.

32. The microporous membrane wipe of claim 26 wherein said dry-stretch process includes the step of transverse direction stretching without machine direction stretch or relax (machine direction stays at 100%).

33. The microporous membrane wipe of claim 26, with said porous polymer film further having a thickness of at least about 8 microns, a transverse direction tensile strength of at least about 225 kgf/cm.sup.2.

34. The microporous membrane wipe of claim 26, with said porous polymer film further having a transverse direction shrinkage of: less than about 6.0% at 90° C.; less than about 15.0% at 120° C.

35. The microporous membrane wipe of claim 26, with said porous polymer film further having a thickness in a range of about 8 microns to 80 microns.

36. The microporous membrane wipe of claim 26, wherein said nonporous precursor is one of a blown film and a slot die film.

37. The microporous membrane wipe of claim 26, wherein said nonporous precursor is a single layer or multilayer precursor formed by at least one of single layer extrusion and multilayer extrusion, or a multilayer precursor formed by at least one of coextrusion and lamination.

38. The microporous membrane wipe of claim 26, wherein said porous polymer film comprises one of polypropylene, polyethylene, blends thereof, impact copolymers, and combinations thereof.

39. The microporous membrane wipe of claim 26, wherein said precursor is one of a single layer precursor and a multilayer precursor, said membrane further includes at least one nonwoven, woven, or knit layer bonded to at least one side of said porous polymer film, said membrane has substantially round shaped pores, a porosity of about 40% to 90%, a ratio of machine direction tensile strength to transverse direction tensile strength in the range of about 0.5 to 5.0 and an Aquapore size of at least about 0.07 microns, and a hydro-head pressure greater than about 140 psi, said polymer being selected from the group consisting of polyolefins, fluorocarbons, polyamides, polyesters, polyacetals (or polyoxymethylenes), polysulfides, polyphenyl sulfide, polyvinyl alcohols, impact copolymers, co-polymers thereof, blends thereof, and combinations thereof, said porous polymer film further having a porosity of about 65% to 90%, a ratio of machine direction tensile strength to transverse direction tensile strength in the range of about 1.0 to 5.0, a JIS Gurley of less than about 60, and an Aquapore size of at least about 0.08 microns, said biaxially stretching step of said dry-stretch process includes the simultaneous biaxial stretching of a plurality of separate, superimposed, layers or plies of nonporous precursor, wherein none of the plies are bonded together during the stretching process, and/or said biaxially stretching step of said dry-stretch process includes the simultaneous biaxial stretching of a plurality of bonded, superimposed, layers or plies of nonporous precursor, wherein all of the plies are bonded together during the stretching process.

40. A method of making a microporous membrane wipe, of making a microporous membrane wipe for skin oil blotting, of making a microporous membrane wipe for the removal of fingerprint, smudges and the like from surfaces like eyeglasses and electronics, like phone screens and other displays, of making a microporous membrane wipe as shown and described herein, and/or of making a layer of a microporous membrane wipe comprising the steps of: extruding a polymer into a nonporous precursor, and biaxially stretching the nonporous precursor, the biaxial stretching including a machine direction stretching and a transverse direction stretching, the transverse direction including a simultaneous controlled machine direction relax.

41. The method according to claim 40 wherein the polymer excludes any oils for subsequent removal to form pores or any pore-forming materials to facilitate pore formation, the polymer being a semi-crystalline polymer, the polymer being selected from the group consisting of polyolefins, fluorocarbons, polyam ides, polyesters, polyacetals (or polyoxymethylenes), polysulfides, polyvinyl alcohols, co-polymers thereof, and combinations thereof, further comprising the step of: annealing the non-porous precursor after extruding and before biaxially stretching, wherein annealing being conducted at a temperature in the range of Tm-80° C. to Tm-10° C., wherein biaxially stretching comprising the steps of: machine direction stretching, and thereafter transverse direction stretching including a simultaneous machine direction relax, wherein machine direction stretching being conducted either hot or cold or both, wherein cold machine direction stretching being conducted at a temperature <Tm-50° C. and/or hot machine direction stretching being conducted at a temperature <Tm-10° C., and/or wherein the total machine direction stretch being in the range of 50-500%, the total transverse direction stretch being in the range of 100-1200%, the machine direction relax from the transverse direction stretch being in the range of 5-80%, or combinations thereof.

Description

EXAMPLES

[0037] The test values reported herein, thickness, porosity, tensile strength, and aspect ratio, were determined as follows: thickness—ASTM-D374 using the Emveco Microgage 210-A micrometer; porosity—ASTM D-2873; tensile strength—ASTM D-882 using an Instron Model 4201; and aspect ratio-measurements taken from analyzing SEM images for pore size, pore diameter, and/or pore dimensions.

[0038] The following examples were produced by conventional dry-stretched techniques, except as noted.

Example 1

[0039] Polypropylene (PP) resin is extruded using a 2.5 inch extruder. The extruder melt temperature is 221° C. Polymer melt is fed to a circular die, The die temperature is set at 220° C., polymer melt is cooled by blowing air. Extruded precursor has a thickness of 27 μm and a birefringence of 0.0120. The extruded film was then annealed at 150° C. for 2 minutes. The annealed film is then cold stretched to 20% at room temperature, and then hot stretched to 228% and relaxed to 32% at 140° C. The machine direction (MD) stretched film has a thickness of 16.4 microns (μm), and porosity of 25%. The MD stretched film is then transverse direction (TD) stretched 300% at 140° C. with MD relax of 50%. The finished film has a thickness of 14.1 microns, and porosity of 37%. TD tensile strength of finished film is 550 Kgf/cm.sup.2.

Example 2

[0040] Polypropylene (PP) resin is extruded using a 2.5 inch extruder. The extruder melt temperature is 220° C. Polymer melt is fed to a circular die. The die temperature is set at 200° C., polymer melt is cooled by blowing air. Extruded precursor has a thickness of 9.5 μm and a birefringence of 0.0160. HDPE resin is extruded using a 2.5 inch extruder. The extruder melt temperature is 210° C. Polymer melt is fed to a circular die. Die temperature is set at 205° C., polymer melt is cooled by air. Extruded precursor has a thickness of 9.5 μm and a birefringence of 0.0330. Two PP layers and one PE layer are laminated together to form a PP/PE/PP tri-layer film. Lamination roll temperature is 150° C. Laminated tri-layer film is then annealed at 125° C. for 2 minutes. The annealed film is then cold stretched to 20% at room temperature, and then hot stretched to 160% and relaxed to 35% at 113° C. The MD stretched film has a thickness of 25.4 microns, and porosity of 39%. The MD stretched film is then TD stretched 400% at 115° C. with MD relax of 30%. The finished film has a thickness of 19.4 microns and porosity of 63%. TD tensile strength of finished film is 350 Kgf/cm.sup.2.

Example 3

[0041] PP resin and HDPE resin are extruded using a co-extrusion die to form a PP/PE/PP tri-layer film. Extruder melt temperature for PP is 243° C., and extruder melt temperature for PE is 214° C. Polymer melt is then fed to a co-extrusion die which is set at 198° C. Polymer melt is cooled by blowing air. The extruded film has a thickness of 35.6 microns. The extruded precursor is then annealed at 125° C. for 2 minutes. The annealed film is then cold stretched to 45% at room temperature and hot stretched to 247% and relaxed to 42% at 113° C. The MD stretched film has a thickness of 21.5 microns and porosity of 29%. The MD stretched film is then TD stretched 450% at 115° C. with 50% MD relax. The finished film has a thickness of 16.3 microns and porosity of 59%. TD tensile strength of finished film is 570 Kgf/cm.sup.2.

Example 4

[0042] PP resin and HDPE resin are co-extruded and MD stretched the same way as in example 3. The MD stretched film is then TD stretched 800% at 115° C. with 65% MD relax. The finished film has a thickness of 17.2 microns and porosity of 49%. TD tensile strength of finished film is 730 Kgf/cm.sup.2.

Example 5

[0043] PP resin and PE resin are extruded using a co-extrusion die. Extruder melt temperature for PP is 230.sup.0 C., and extruder melt for PE is 206° C. Polymer melt is then fed to a co-extrusion die which is set at 210° C. Polymer melt is then cooled by blowing air. The extruded film has a thickness of 36.0 microns. The extruded precursor is then annealed at 105° C. for 2 minutes. The annealed film is then cold stretched to 20%, and then hot stretched at 105° C. to 155% and then relaxed to 35%. The MD stretched film is then TD stretched 140% at 110° C., with 20% MD relax. The finished film has a thickness of 14.8 microns and porosity of 42%. TD tensile strength of finished film is 286 Kgf/c

Example 6

[0044] PP resin and PE resin are extruded using a co-extrusion die to form a PP/PE/PP trilayer film. Extruder melt temperature for PP is 245° C,, and extruder melt temperature for PE is 230° C. Polymer melt is then fed to a co-extrusion die which is set at 225° C. Polymer melt is cooled by blowing air. The extruded film has a thickness of 27 microns and a birefringence of 0. 0120. The extruded precursor is then annealed at 115° C. for 2 minutes. The annealed film is then cold stretched to 22% at room temperature and hot stretched to 254% and relaxed to 25% at 120° C. (total machine direction stretch=251%). The MD stretched film has a thickness of 15 microns and porosity of 16%. The MD stretched film is then TD stretched 260% at 130° C. with 50% MD relax, followed by a simultaneous MD and TD stretch of 50% and 216% in each direction at 130° C., and finally the film is held fast in the MD (100%) and allowed to relax 57.6% in the TD at a temperature of 130° C. The finished film has a thickness of 7,6 microns and porosity of 52%. TD tensile strength of finished film is 513 Kgf/cm.sup.2.

Example 7

[0045] PP resin and PE resin are extruded using a co-extrusion die to form a PP/PE/PP trilayer film. Extruder melt temperature for PP is 222° C., and extruder melt temperature for PE is 225° C. Polymer melt is then fed to a co-extrusion die which is set at 215° C. Polymer melt is cooled by blowing air. The extruded film has a thickness of 40 microns and birefringence of 0.0110. The extruded precursor is then annealed at 105° C. for 2 minutes. The annealed film is then cold stretched to 36% at room temperature and hot stretched to 264% and relaxed to 29% at 109° C. (total machine direction stretch=271%). The MD stretched film has a thickness of 23.8 microns and porosity of 29.6%. The MD stretched film is then TD stretched 1034% at 110° C. with 75% MD relax. The finished film has a thickness of 16.8 microns and porosity of 46%. TD tensile strength of finished film is 1037 Kgf/cm.sup.2.

Example 8

[0046] A PP based impact copolymer is extruded to form a film. Extruder melt temperature is 249° C., Polymer melt is fed to an extrusion die set at 215° C. The polymer melt is cooled by blowing air. The extruded film has a thickness of 34 μm and birefringence of 0.0116. The extruded precursor is then annealed at 154° C. for 2 minutes. The annealed film is then cold stretched to 30% at room temperature and hot stretched 190% and relaxed 61% at 140° C. (total machine direction stretch=159%). The MD stretched film has a thickness of 26 μm and porosity of 40%. The MD stretched film is then TD stretched 260% at 150° C. with 50% MD relax, followed by a simultaneous MD and TD stretch of 50% and 216%, respectively, at 150° C.

[0047] In the following table, Table 1, the results of the foregoing experiments are summarized and compared to two commercially available dry-stretched films: A) CELGARD® 2400 (single ply polypropylene membrane); and B) CELGARD® 2325 (tri-layer polypropylene/polyethylene/polypropylene membrane).

TABLE-US-00001 TABLE 1 TD MD Tensile Tensile MD/TD TD Thickness strength strength tensile stretching (um) Porosity (kgf/cm.sup.2) (kgf/cm.sup.2) ratio A N/A 25.4 37% 160 1700 10.6 B N/A 25.1 40% 146 1925 13.2 Ex 1 300% 14.1 37% 550 1013 1.8 Ex 2 400% 19.4 63% 350 627 1.8 Ex 3 450% 16.3 59% 570 754 1.3 Ex 4 800% 17.2 49% 730 646 0.9 Ex 5 140% 14.8 42% 286 1080 3.8 Ex 6 418% 7.6 52% 513 1437 2.8 Ex 7 1034%  16.8 46% 1037 618 0.6 Ex 8 450% 17 73% 287 558 1.9

Example 9

[0048] In this Example, a procedure similar to Example 8 was followed up through machine direction stretching. In particular, a PP based impact copolymer is extruded to form a film. Extruder melt temperature is 249° C., Polymer melt is fed to an extrusion die set at 215° C. The polymer melt is cooled by blowing air. The extruded film has a thickness of 34 μm and birefringence of 0.0116. The extruded precursor is then annealed at 154° C. for about 10 minutes. The annealed film is then cold stretched to 30% at room temperature and hot stretched 190% and relaxed 61% at 140° C. (total machine direction stretch =159%). The MD stretched film has a thickness of 26 μm and porosity of 40%.

[0049] Various multi-ply rolls of machine direction stretched film were then stretched in the transverse direction according to various conditions reported in Table 2 below,

TABLE-US-00002 TABLE 2 Stretch Speed Preheat Stretch Anneal Ratio (feet Temp Temp Temp Sample (X) per min) (F.) (F.) (F.) Roll 9A 4.8 7 320 310 310 Roll 9B 4.8 20 320 310 310 Roll 9C 4.8 7 310 300 300 Roll 9D 4.8 7 300 290 290 Roll 9E 4.8 7 290 280 280 Roll 9F 4.8 25 290 280 280
The process used in Example 9 did not include a simultaneous machine direction relax during TD stretching. And yet the results obtained were comparable to results obtained when such a simultaneous machine direction relax is employed during TD stretching. This means that various processes according to this embodiment may increase the throughput and/or speed of processes used to make microporous membranes and various wipes. See, for example, Rolls 9B and 9F, for which the speed through transverse stretching was 20 and 25 feet per minute, respectively, versus 7 feet per minute for other roll samples.

[0050] Once the various multi-ply roll samples described above were TD stretched, various properties of a ply of such rolls were determined, as shown in Table 3 below:

TABLE-US-00003 TABLE 3 Basis Wt Thickness Thickness Roll (gsm) (μm, avg) (std. dev., μm) 9A 2.6 10.356 2.244 9B 2.3 15.576 1.196 9C 2.7 18.46 0.89 9D 3 15.84 1.116 9E 3 17.303 1.37 9F 3.1 17.06 0.956

Example 10

[0051] In the following examples, oil absorption testing was performed on various samples of microporous membrane wipes made in accordance with various objects of the present invention. Such wipes were compared with commercially available wipes. In particular, separate tests were performed using two types of oil (dodecane, a somewhat thin oil, and canola oil, a thicker oil, possibly more analogous to oil found in skin, such as fingers or face). The designated oil was poured into a 4″ diameter petri dish to a depth of approximately 3 mm. A piece of paper towel was folded several times and placed in the petri dish such that the paper towel became saturated with oil. Facial blotter samples were cut into rectangular strips and were weighed on a Mettler Toledo AL104 laboratory scale to obtain the “pre-oiled weight.” Next, each strip was placed on the saturated paper towel until the strip was fully saturated. The saturated strip was then weighed again to obtain the “oiled weight.”

[0052] The facial blotter samples included the following: [0053] 1. Celgard® polypropylene copolymer microporous membrane wipe, 14-16 μm thickness, 3.0-3.6 gsm basis weight (Celgard® “EZ3030”). This material was tested in both single-layer and double-layer configurations. In some embodiments, these wipes were referred to as Celgard® premium facial blotters. These wipes were made in accordance with various embodiments of the present invention. [0054] 2. Comparative Japanese polypropylene facial blotter sold globally under the Clean & Clear® brand name and produced by 3M in Japan. Ingredients listed on the packaging for such facial blotters included polypropylene, mineral oil, dimethyldibenzylidene sorbitol, and ultramarines. Product procured in the US (see Table 5) was 37-39 μm thick with a basis weight of 25-26 gsm. Product procured in Taiwan (see Tables 4 and 5) was 39-43 μm thick with a basis weight of 25 gsm. [0055] 3. Comparative cellulose-based (or paper-based) facial blotters sold under the Cosmed and Petite Garden brand names. Ingredients listed on the packaging for the Cosmed facial blotters included 100% pure flax pulp. The Cosmed blotters were 22 μm thick with a basis weight of 16 gsm. The Petite Garden blotters were 28 μm thick with a basis weight of 16 gsm.

[0056] Testing was performed to determine oil absorption of dodecane for various samples, and the results are shown in Table 4 below. The oil absorption ratio represents the amount of oil absorbed (mg) divided by the pre-oiled weight of the particular sample.

TABLE-US-00004 TABLE 4 Pre-oiled Oiled Oil (dodecane) weight weight absorption ratio Product type Sample (mg) (mg) (mg/mg) Celgard ® single- 1 8.6 57.6 5.67 layer PP membrane 2 9.0 55.9 5.19 facial blotter 3 9.0 64.1 6.15 (EZ3030) 4 8.2 51.7 5.33 Average: 5.58 Celgard ® two- 5 19.2 102.8 4.35 layer PP membrane 6 19.4 101.0 4.22 facial blotter 7 17.8 86.9 3.87 (EZ3030) 8 16.7 89.0 4.34 Average: 4.20 Paper blotting 9 62.6 131.3 1.10 sheet (Cosmed) 10 62.4 139.3 1.23 11 61.0 142.9 1.34 12 62.4 141.5 1.27 Average: 1.23 Paper blotting 13 46.8 97.1 1.07 sheet (Petite 14 46.3 113.8 1.46 Garden) 15 48.3 99.7 1.06 16 45.7 102.6 1.25 Average: 1.21 Plastic blotting 17 57.0 94.2 0.65 sheet (Clean & 18 59.1 111.1 0.88 Clear ®, sourced 19 55.8 102.1 0.83 in Taiwan) 20 57.9 99.2 0.71 Average: 0.77

[0057] The results above in Table 4 reveal that the single-layer and double-layer Celgard® polypropylene wipes according to the present invention performed better in oil absorption testing (using dodecane) than the comparative samples.

[0058] Testing was also performed to determine oil absorption of canola oil for various samples, and the results are shown in Table 5 below:

TABLE-US-00005 TABLE 5 Pre-oiled Oiled Oil (canola oil) weight weight absorption ratio Product type Sample (mg) (mg) (mg/mg) Celgard ® single- 21 8.7 118.9 12.61 layer PP membrane 22 8.8 123.3 12.96 facial blotter 23 7.2 110.0 14.35 (EZ3030) 24 7.9 122.0 14.51 Average: 13.61 Celgard ® two- 25 17.9 171.2 8.58 layer PP membrane 26 18.0 175.3 8.72 facial blotter 27 18.3 174.3 8.51 (EZ3030) 28 18.2 184.1 9.10 Average: 8.73 Paper blotting 29 64.5 252.2 2.91 sheet (Cosmed) 30 62.2 238.3 2.83 31 65.0 239.1 2.68 32 62.9 250.1 2.97 Average: 2.85 Paper blotting 33 46.2 178.5 2.86 sheet (Petite 34 47.8 179.2 2.75 Garden) 35 47.7 186.7 2.92 36 46.1 171.7 2.72 Average: 2.81 Plastic blotting 37 55.3 168.1 2.04 sheet (Clean & 38 54.2 162.2 1.99 Clear ®, sourced 39 54.8 170.5 2.11 in Taiwan) 40 55.7 170.4 2.06 Average: 2.05 Plastic blotting 41 55.7 163.7 1.94 sheet (Clean & 42 57.7 158.6 1.75 Clear ®, sourced 43 52.1 154.2 1.96 in US) 44 55.8 161.4 1.89 Average: 1.88
The results above in Table 5 reveal that the single-layer and double-layer Celgard® polypropylene wipes according to the present invention performed better in oil absorption testing (using canola oil) than the comparative samples.

[0059] In accordance with at least selected embodiments, aspects or objects, the present invention may relate to new or improved microporous membranes, new or improved porous membrane wipes, new or improved microporous membrane wipes, and/or methods of manufacture, marketing, and/or use thereof, toward a new or improved method for oil blotting utilizing a microporous membrane wipe, preferably an oil loving or oleophilic material, such as a polyolefin (PO), PP or PE microporous membrane wipe, preferably a dry process PO, PP or PE microporous membrane wipe, like use in blotting oil from one's skin or face, and/or the removal of fingerprint, smudges and the like from other surfaces like eyeglasses, electronics, cell phones, displays, optical devices, camera lenses, microscope lenses and other precision optics, and/or the like, to microporous membrane wipes that may be a uniaxially or a biaxially oriented microporous membrane, may be a uniaxially or biaxially oriented microporous membrane made from one or more copolymers, such as impact and/or block copolymers of polyethylene (PE) and/or polypropylene (PP), and/or the like.

[0060] The present invention may be embodied in other forms without departing from the spirit and the essential attributes thereof, and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention. Additionally, the invention illustratively disclosed herein suitably may be practiced in the absence of any element which is not specifically disclosed herein.