FIELD OF THE INVENTION
This application is a continuation-in-part application of U.S. Ser. No. 10/295,017, filed Nov. 13, 2002, which application is incorporated herein by reference
- BACKGROUND OF THE INVENTION
The invention is embodied in a surface shape conformable and flexible wipe having at least two layers of material. The wipe, comprising a nanofiber layer and a flexible woven or non-woven fabric substrate, can remove soils in the form of inorganic or organic particulate, oily or greasy soils, or dispersions of particulate in liquid. The wipe has a layer specifically designed to trap or otherwise incorporate finely divided small particle size soil for efficient removal from a variety of contaminated surfaces. The wipe can also absorb oily or greasy soils into the fabric substrate. Further, when used with appropriate liquid (aqueous or organic) cleaning, dusting or other such compositions, the fine fiber layer can obtain an improved surface appearance due to the reduced size of any structure formed from cleaning compositions.
Both woven and non-woven fabrics have been used for many years for cleaning and polishing purposes. Such fabrics are typically manufactured by forming fiber into a woven or non-woven structure. These fabrics must conform to the contaminated surfaces for the purposes of either dry wiping (dusting) or wet wiping (with water or liquid cleaners or polishing composition) particulate, organic or inorganic soils, from contaminant laden surfaces. Such particulates are commonly considered soils and their removal is highly desirable in many environments for maintaining cleanliness, human health, improved production efficiency or through the removal of biological, chemical or radioactive contamination. These materials can also be used to renew or polish surfaces using finishing compositions to form a shining surface. Generally, the woven and non-woven fabrics have an absorbent assembly of fibers. Conventional cloths can often remove particulate at some level of efficiency and, when used wet, be able to absorb quantities of liquid material either as a result of liquid contamination or through the application of liquid cleaners to a soiled surface. Examples of conventional fabrics include Nankee et al., U.S. Pat. No. 3,686,024; Lindsey et al., U.S. Pat. No. 4,260,443; Packard et al., U.S. Pat. No. 4,851,069 and Makoui European Patent Application No. 35 96 15. In large part, these wipes are cellulosic composites that interact with water or other aqueous cleaners to obtain efficient cleaning capacity.
The prior art has also recognized that a unique type of finite length fine fiber materials can be included in such structures. Such structures are shown in Anderson et al., U.S. Pat. No. 4,100,324; Meitner, U.S. Pat. No. 4,307,143; Anderson et al., U.S. Pat. No. 5,651,862 and Torobin, U.S. Pat. No. 6,269,513. These nanofiber containing structures rely on a technology in which the nanofibers, in the form of reduced lengths of fiber, are incorporated and distributed throughout the non-woven or woven matrix and combined with other fiber in the fiber mass in the wipe. No discrete fine fiber layer is found in or on the wipe. The fine fiber inside the layers allegedly improves cleaning properties of the pad or composite material.
Our experience with conventional woven and non-woven wipes, even those containing nanofiber dispersed in the bulk material, is that these wipes have adequate, conventional cleaning properties. The wipes, however, often fail to substantially remove small particulate in a cleaning mode. The large fiber part of these materials results often in a level of finish formation not acceptable to users.
- BRIEF DESCRIPTION OF THE INVENTION
Accordingly, a substantial need exists for new conformable wipe configurations that are adapted to trapping and removing small particulate contaminant from surfaces. Such wipes can substantially improve cleaning efficiency by removing small particulate, soils, bacteria, chemical and biological contaminants and potentially radioactive materials as well. Such wipes, with reduced fiber size can form an improved surface finish by reducing surface defects.
The wipe structure constituting an aspect of the invention comprises at least a flexible conformable fabric substrate layer having discrete sides and a discrete fine fiber layer formed on at least one side of the substrate.
The fabric substrate used in making the wipe of the invention can comprise either a woven or non-woven fabric having a thickness of about 0.01 to 0.2 cm or about 0.02 to 0.1 cm, made from natural or synthetic materials. Natural materials include cotton or flax fibers. Synthetic polymer materials are known in the art. Many useful fabric substrates comprise a mixed cellulosic/synthetic, non-woven fabric made by combining cellulosic fiber with synthetic fibers such as polyolefins, polyesters, etc. Such fabrics are made by weaving or by adhering a layer of randomly laid fiber. Fabrics used in such wipes are available woven and nonwoven materials.
The fine fiber layer of the invention comprises a layer having a layer thickness of about 0.05 to 30 millimeters, a fiber diameter of about 0.05 to 5, a diameter of about 0.05 to 2 microns, or a diameter of about 0.05 to 0.5 microns, a basis weight of about 0.0012 to 3.5 grams per meter2 and a pore size that ranges from about 0.5 to 20 microns. The presence of the very small diameter fine fiber (compared to conventional fibers) permits the fine fiber to trap or incorporate inorganic particulate and absorb organic soil in cleaning operations. In polishing operations, the small dimensions of the fine fiber results in improved surface characteristics derived from polishing or first coating applications. The fine fiber layer on the flexible wipe of the invention provides a web of fibers having a smaller dimension than conventional cleaning wipes. Such small fibers, when used with a material that forms a surface finish or coating on a cleaning surface, can obtain a smoother, shinier, more aesthetically pleasing appearance. Any finish formed using the fine fiber layer will have an improved surface finish resulting from the improved surface characteristics left by the smaller fiber of the fine fiber layer. The fine fiber forms fewer and smaller defects than larger fiber wipes. Accordingly, the fine fiber wipes of the invention can be used in a process that forms an improved finish on a cleanable surface by contacting the surface with a composition that can form a coating on the surface, wiping the surface with a fine fiber layer (either saturated with the composition or with a composition pre-applied to the surface), distributing the coating and permitting the coating to form its final improved characteristic.
For the purpose of this disclosure, the term “inorganic particulate” typically refers to finely divided particulate soils derived from the environment including dust and dirt particulates having a particle size of about 10−3 to 105 micron, often 10−2 to 10 micron. The term “organic soils” typically include soils derived from human occupation, foods, cosmetics, cleaners, or common organic materials from the human environment. Often, such organic and inorganic soils can be combined with small particulate organic matter such as skin cells, hair components, insects and insect parts, etc.
BRIEF DESCRIPTION OF THE FIGURES
One important characteristics of the wipe is the flexibility of the wipe and the flexibility of the fine fiber layer. While the polymers of the invention display flexural properties similar to unfilled polymer, the small fiber diameter gives the fiber on the wipe a unique flexibility and improved cleaning/polishing character. Cleaning pressure can bring the fine fiber into intimate contact with the soil, the surface regardless of its complexity. In contact with the soils, the unique nature of the fine fiber causes the fiber to combine with the soils and trap or accumulate soils as the fiber layer is mechanically stretched, wrapped and changed. In a polishing mode, the fiber small size can form an improved surface coating due to the coating having a reduced defect character due the size of the fiber. Larger conventional fiber leaves larger defects in the finished coating. In the wipe substrate, many synthetic and natural fiber materials are available that have substantial stiffness. Such materials cannot be made sufficiently flexible to be able to easily comply with complex surfaces faced by individuals who wish to clean or polish such surfaces. The wipes should be manufactured from a material that is flexible and easily conformable to the surface. The term “conformable” means that the wipe and the fine fiber layer can be placed into contact with a surface for cleaning proposes even with surfaces that have complex angled or curved surfaces. Minimal pressure can bring the fine fiber layer into intimate contact with substantially all surfaces of a complex article.
DETAILED DISCUSSION OF THE INVENTION
FIGS. 1-17 are scanning electron-photo micrographs (SEMS) of wipes with a nanofiber layer that have been used to remove both inorganic particulate and organic soils form a automotive glass surface or a polymeric dash surface. The figures show that the fibers can trap both organics and inorganic soils. Small particulate is enmeshed by the fiber while the organic soils coat the fibers on contact between the fiber and soil. The interaction of the surface and soil with the fine fiber layer changes the conformation of the fiber layer as the fibers trap particulate and accumulate organic soil.
The wipe of the invention comprises at least a two-layer structure. The first layer comprises a flexible, conformable, woven or non-woven fabric layer. The second layer comprises a layer of a nanofiber. The major difference between the fabric and the nanofiber is in the fiber size and the thickness of the layers. The conformable wipe can be applied to any flat, convex, concave or complex surface for the purpose of removing inorganic or organic soils or for the purpose of restoring a shiny, pleasing appearance to the surface.
For the purpose of this patent application, the term “fine fiber” refers to a fiber having an indeterminate length but a width of less than about 5 microns often, less than about 2 and often less than about 1 micron. In the wipe, the fine fiber is formed into a randomly oriented mesh of fiber in a layer that substantially covers a surface of the fabric substrate. Preferred fine fiber layer add-on parameters are as follows:
| || |
| || |
| ||Dimensions ||Range |
| || |
| ||Layer thickness (μm) ||0.1 to 5 |
| ||Solidity % || 5 to 40 |
| ||Density (gm-cm−3) ||0.9 to 1.6 (1.2 to 1.4) |
| ||Basis wt. (mg-cm−2) ||1.2 × 10−4 to 3.5 |
| || |
In one embodiment, a reduced amount but useful add-on amount of fine fiber would be a 0.1 to 1.75 micron thick layer of 5% to 40% solidity fiber layer (95% to 60% void fraction). In this case the basis weight is 4×10−4 to 0.11 mg-cm−2.
In another embodiment, an add-on amount of fine fiber would a 0.75 to 1.25 micron thick layer of 15% to 25% solidity fiber layer (85% to 75% void fraction) In this case the basis weight is 1.0×10−2 to 0.05 mg-cm−2.
In a final embodiment, the upper end of the add-on amount of fine fiber would be a 0.1-3 micron thick layer of 10% to 40% solidity fiber layer (90% to 60% void fraction). In this case the basis weight is 4×10−4 to 0.2 mg-cm−2.
For the purpose of this disclosure, the term “separate from fiber layer” is defined to mean that in the wipe structure, having a substantially sheet-like substrate, the fine fiber layer substantially covers the fabric substrate. The fine fiber layers can in theory be manufactured in one processing step that covers the entirety of one or both surfaces of a two sided flexible fabric. In most applications, we envision that a first fine fiber layer will be formed on one fabric side.
For the purpose of this disclosure, the term “fine fiber layer pore size or fine fiber web pore size” refers to a space formed between the intermingled fibers in the fine fiber layer.
For the purpose of this disclosure, the term “fabric or fabric substrate” refers to a woven or non-woven sheet like substrate, having a thickness of about 0.1 to 5 millimeters.
The wipe includes at least a fine fiber or nanofiber layer in combination with a fabric substrate material in a mechanically stable structure. The fine fiber layer must be sufficiently mechanically and chemically stable to obtain cleaning or polishing through interaction with soil and surface. These layers together provide excellent organic absorption, surface conformation, and high particle capture. After use the polymer fiber or fiber web may be substantially changed in physical conformation. Mechanical forces of wiping can substantially consolidate the fine fiber layer and distort the fine fiber substantially form its initial form. The wipes of the invention are manufactured by spinning fine fiber and then forming an interlocking web of microfiber on a porous wipe fabric substrate. In the spinning process the fiber can form physical bonds between fibers to interlock the fiber mat into an integrated layer on the fabric. Such a material can then be fabricated into the desired wipe format such as a dry or wet wipe.
The invention relates to polymeric compositions with improved properties that can be used in a variety of applications including the formation of nanofibers, fiber webs, fibrous mats, etc. The fine fibers that comprise the micro- or nanofiber containing layer of the invention can be fiber and can have a diameter of about 0.001 to 2 micron, preferably 0.05 to 0.5 micron. The thickness of the typical fine fiber layer ranges from about 1 to 100 times the fiber diameter with a basis weight ranging from about 4.5×10−4 to 2 mg-cm−2.
The fine fiber-containing wipe of the invention can be used to clean virtually any soil or contaminated surfaces. Such surfaces can include surfaces in the home including metal, plastic, wood, glass or other common household surface. Surfaces found in industry including process equipment, instrumentation, computer equipment, communications equipment, etc. Surfaces common in the hospital environment such as instrumentation, beds, gurneys, operating theater environments, laboratory environments, etc. Other important surfaces include surfaces that may be contaminated by chemical or biological agents, radioactive agents derived from weapon research, manufacture or terrorist threat. Other surfaces can be surfaces of parts of the human body. The wipes can be used for medical, hygienic or cosmetic purposes. Such applications include baby wipes, medical wipes; cosmetic wipes facial wipes or flushable materials. Such surfaces can be substantially planar, formed into simple curves or configured into complex shapes having complex curvature, sharp edges, corners or grooves. Such surfaces can be contaminated with either organic or inorganic soils or combinations thereof. As a result, the wipe of the invention must be flexible and conformable to any surface requiring cleaning or polishing. The wipe must be sufficiently flexible such that the nanofiber layer can contact substantially the entire surface during cleaning operations. The fine fiber layer must come into contact with organic, inorganic or particulate soils in order to permit the fine fiber to obtain the organic soils as a coating on the fiber and to enmesh the particulate soil in the fine fiber structure. As can be seen in the photomicrographs shown in FIGS. 1 through 17 of the invention, the fine fiber materials of the invention are engineered such that the fiber can enmesh particulate soil and can absorb organic soil onto the surface of the fiber for cleaning purposes. This property is the result of both the chemical nature of the fine fiber and its size and distribution in the fine fiber layer.
Polymeric materials have been fabricated in non-woven and woven fabrics, fibers, microfibers and nanofibers. The polymer materials that can be used in the fine fiber or the polymeric fiber fabric compositions of the invention include both addition polymer and condensation polymer materials such as polyolefin, polyacetal, polyamide, polyester, cellulose ether and ester, polyalkylene sulfide, polyarylene oxide, polysulfone, modified polysulfone polymers and mixtures thereof. Preferred materials that fall within these generic classes include polyethylene, polypropylene, poly(vinylchloride), polymethylmethacrylate (and other acrylic resins), polystyrene, and copolymers thereof (including ABA type block copolymers), poly(vinylidene fluoride), poly(vinylidene chloride), polyvinylalcohol in various degrees of hydrolysis (87% to 99.5%) in crosslinked and non-crosslinked forms. Preferred addition polymers tend to be glassy (a Tg greater than room temperature). This is the case for polyvinylchloride and polymethylmethacrylate, polystyrene polymer compositions or alloys or low in crystallinity for polyvinylidene fluoride and polyvinylalcohol materials. One class of polyamide condensation polymers include nylon materials. The term “nylon” is a generic name for all long chain synthetic polyamides. Typically, nylon nomenclature includes a series of numbers such as in nylon-6,6 which indicates that the starting materials are a C6 diamine and a C6 diacid (the first digit indicating a C6 diamine and the second digit indicating a C6 dicarboxylic acid compound). Another nylon can be made by the polycondensation of epsilon caprolactam in the presence of a small amount of water. This reaction forms a nylon-6 (made from a cyclic lactam—also known as episilon-aminocaproic acid) that is a linear polyamide. Further, nylon copolymers are also contemplated. Copolymers can be made by combining various diamine compounds, various diacid compounds and various cyclic lactam structures in a reaction mixture and then forming the nylon with randomly positioned monomeric materials in a polyamide structure. For example, a nylon 6,6-6,10 material is a nylon manufactured from hexamethylene diamine and a C6 and a C10 blend of diacids. A nylon 6-6,6-6,10 is a nylon manufactured by copolymerization of epsilonaminocaproic acid, hexamethylene diamine and a blend of a C6 and a C10 diacid material.
Block copolymers are also useful in the process of this invention. One example is an ABA (styrene-EP-styrene) or AB (styrene-EP) polymer. Examples of such block copolymers are Kraton® type of styrene-b-butadiene and styrene-b-hydrogenated butadiene (ethylene propylene), Pebax® type of e-caprolactam-b-ethylene oxide, Sympatex® polyester-b-ethylene oxide and polyurethanes of ethylene oxide and isocyanates.
Addition polymers like polyvinylidene fluoride, syndiotactic polystyrene, copolymer of vinylidene fluoride and hexafluoropropylene, polyvinyl alcohol, polyvinyl acetate, amorphous addition polymers, such as poly(acrylonitrile) and its copolymers with acrylic acid and methacrylates, polystyrene, poly(vinyl chloride) and its various copolymers, poly(methyl methacrylate) and its various copolymers, can be solution spun with relative ease because they are soluble at low pressures and temperatures. However, highly crystalline polymer like polyethylene and polypropylene require high temperature, high pressure solvent if they are to be solution spun. Therefore, solution spinning of the polyethylene and polypropylene is very difficult. Electrostatic solution spinning is one method of making nanofibers and microfiber.
Fluoropolymer materials can be used in the fine fiber layers of the invention. Fluoropolymer elastomers are preferred. The most commonly available Fluoropolymer elastomer is the Viton® (DuPont) elastomeric composition. The preferred use of the fluoropolymer elastomer is in the dual layer of fine fiber. Such dual layers can comprise a fabric substrate, a first layer of fluoropolymer elastomer fine fiber followed by a second layer of a second fine fiber composition.
Viton exhibits good resistance to most oils, chemicals, solvents, and halogenated hydrocarbons, and an excellent resistance to ozone, oxygen, and weathering. Also referred to as fluoroelastomers, fluorocarbon compounds are thermoset elastomers containing fluorine. Fluorocarbons make excellent general-purpose fibers thanks to their exceptional resistance to chemicals, oils, and temperature extremes (−15° F. to +400° F.). Specialty compounds can further extend the low temperature limit down to −22° F. for dynamic seals and −40° F. in static applications. Fluorocarbons typically have good temperature performance, and resistance to ozone and sunlight. Over the last five decades, this remarkable combination of properties has prompted the use of fluorocarbon seals in a variety of demanding sectors. The useful temperature range of the materials is about −10° F. to +400° F. in continuous service.
Suitable haloelastomers for use herein include any suitable halogen containing elastomer such as chloroelastomers, bromoelastomers, fluoroelastomers, or mixtures thereof. Fluoroelastomer examples include those described in detail in Lentz, U.S. Pat. No. 4,257,699, as well as those described in Eddy et al., U.S. Pat. No. 5,017,432 and Ferguson et al., U.S. Pat. No. 5,061,965. The disclosures of each of these patents are totally incorporated herein by reference. The original commercial fluorocarbon, Viton® A, is the general-purpose type and is still the most widely used. It is a copolymer of vinylidene fluoride (VF2) and hexafluoropropylene (HFP). Generally composed of 60-70% fluorine, Viton A compounds offer excellent resistance against many automotive and aviation fuels, as well as both aliphatic and aromatic hydrocarbon process fluids and chemicals. Viton A compounds are also resistant to engine lubricating oils, aqueous fluids, steam, and mineral acids. Viton B fluorocarbons are terpolymers combining tetrafluoroethylene (TFE) with VF2 and HFP. Depending on the exact formulation, the TFE partially replaces either the VF2 (which raises the fluorine level to approximately 68%) or the HFP (keeping the fluorine level steady at 66%). Viton B compounds offer better fluids resistance than the Viton A copolymers. Viton GF fluorocarbons are tetrapolymers composed of TFE, VF2, HFP, and small amounts of a cure site monomer (Csm). Presence of the cure site monomer allows peroxide curing of the compound, which is normally 70% fluorine. As the most fluid resistant of the FKM types, Viton GF compounds offer improved resistance to water, steam, and acids.
Viton GFLT fluorocarbons are similar to Viton GF, except that perfluoromethylvinyl ether (PMVE) is used in place of HFP. The “LT” in Viton GFLT stands for “low temperature.” The combination of VF2, PMVE, TFE, and a cure site monomer is designed to retain both the superior chemical resistance and high heat resistance of the G-series fluorocarbons. In addition, Viton GFLT compounds (typically 67% fluorine) offer the lowest swell and the best low temperature properties of the types discussed here. Viton GFLT can seal in a static situation down to approximately −40° F. A brittle point of −50° F. can be achieved through careful compounding.
As described therein, the next generation of these fluoroelastomers include copolymers and terpolymers of vinylidenefluoride, hexafluoropropylene and tetrafluoroethylene, which are known commercially under various designations as VITO® A, VITON® E, VITON® E60C, VITON® E45, VITON® E430, VITON® B910, VITON® GH, VITON® B50, VITON® E45, and VITON® GF. The VITON designation is a Trademark of E.I. DuPont de Nemours, Inc. Two preferred known fluoroelastomers are (1) a class of copolymers of vinylidenefluoride, hexafluoropropylene and tetrafluoroethylene, (such as a copolymer of vinylidenefluoride and hexafluoropropylene) known commercially as VITOA® A, (2) a class of terpolymers of vinylidenefluoride, hexafluoropropylene and tetrafluoroethylene known commercially as VITON® B, and (3) a class of tetrapolymers of vinylidenefluoride, hexafluoropropylene, tetrafluoroethylene and a cure site monomer. The cure site monomer can be those available from DuPont such as 4-bromoperfluorobutene-1,1,1-dihydro-4-bromoperfluorobutene-1,3-bromoperfluoropropene-1,1,1-dihydro-3-bromoperfluoropropene-1, or any other suitable, known, commercially available cure site monomer. In another preferred embodiment, the fluoroelastomer is a tetrapolymer having a relatively low quantity of vinylidenefluoride. An example is VITON® GF, available from E.I. DuPont de Nemours, Inc. The VITON® GF has 35 weight percent of vinylidenefluoride, 34 weight percent of hexafluoropropylene and 29 weight percent of tetrafluoroethylene with 2 weight percent cure site monomer. Typically, these fluoroelastomers are cured with a nucleophilic addition curing system, such as a bisphenol crosslinking agent with an organophosphonium salt accelerator as described in further detail in the above-referenced Lentz patent and in U.S. Pat. No. 5,017,432. The fluoroelastomer is generally cured with bisphenol phosphonium salt, or a conventional aliphatic peroxide curing agent. Some of the aforementioned haloelastomers and others that can be selected include VITON® E45, AFLAS®, FLUOREL®, FLUOREL® II, TECHNOFLON® and the like commercially-available haloelastomers. Similar polymers are available from 3M as Dyneon products.
We have also found a substantial advantage to forming polymeric compositions comprising two or more polymeric materials in polymer admixture, alloy format or in a crosslinked chemically bonded structure. We believe such polymer compositions improve physical properties by changing polymer attributes such as improving polymer chain flexibility or chain mobility, increasing overall molecular weight and providing reinforcement through the formation of networks of polymeric materials.
In one embodiment of this concept, two related polymer materials can be blended for beneficial properties. For example, a high molecular weight polyvinylchloride can be blended with a low molecular weight polyvinylchloride. Similarly, a high molecular weight nylon material can be blended with a low molecular weight nylon material. Further, differing species of a general polymeric genus can be blended. For example, a high molecular weight styrene material can be blended with a low molecular weight, high impact polystyrene. A Nylon-6 material can be blended with a nylon copolymer such as a Nylon-6; 6,6; 6,10 copolymer. Further, a polyvinylalcohol having a low degree of hydrolysis such as a 87% hydrolyzed polyvinylalcohol can be blended with a fully or superhydrolyzed polyvinylalcohol having a degree of hydrolysis between 98 and 99.9% and higher. All of these materials in admixture can be crosslinked using appropriate crosslinking mechanisms. Nylons can be crosslinked using crosslinking agents that are reactive with the nitrogen atom in the amide linkage. Polyvinylalcohol materials can be crosslinked using hydroxyl reactive materials such as monoaldehydes, such as formaldehyde, ureas, melamine-formaldehyde resin and its analogues, boric acids and other inorganic compounds. dialdehydes, diacids, urethanes, epoxies and other known crosslinking agents. Crosslinking technology is a well known and understood phenomenon in which a crosslinking reagent reacts and forms covalent bonds between polymer chains to substantially improve molecular weight, chemical resistance, overall strength and resistance to mechanical degradation.
The fine fiber can be made of a polymer material or a polymer plus additive. One preferred mode of the invention is a polymer blend comprising a first polymer and a second, but different polymer (differing in polymer type, molecular weight or physical property) that is conditioned or treated at elevated temperature. The polymer blend can be reacted and formed into a single chemical specie or can be physically combined into a blended composition by an annealing process. Annealing implies a physical change, like crystallinity, stress relaxation or orientation. Preferred materials are chemically reacted into a single polymeric specie such that a Differential Scanning Calorimeter analysis reveals a single polymeric material. Such a material, when combined with a preferred additive material, can form a surface coating of the additive on the microfiber that provides oleophobicity, hydrophobicity or other associated improved stability when contacted with high temperature, high humidity and difficult operating conditions. The fine fiber of the class of materials can have a diameter of about 0.01 to 5 microns. Such microfibers can have a smooth surface comprising a discrete layer of the additive material or an outer coating of the additive material that is partly solubilized or alloyed in the polymer surface, or both. Preferred materials for use in the blended polymeric systems include nylon 6; nylon 66; nylon 6-10; nylon (6-66-610) copolymers and other linear generally aliphatic nylon compositions. A preferred nylon copolymer resin (SVP-651) was analyzed for molecular weight by the end group titration. (J. E. Walz and G. B. Taylor, determination of the molecular weight of nylon, Anal. Chem. Vol. 19, Number 7, pp 448-450 (1947). A number average molecular weight (Mn) was between 21,500 and 24,800. The composition was estimated by the phase diagram of melt temperature of three component nylon, nylon 6 about 45%, nylon 66 about 20% and nylon 610 about 25%. (Page 286, Nylon Plastics Handbook, Melvin Kohan ed. Hanser Publisher, New York (1995)).
Reported physical properties of SVP 651 resin are:
|Property ||ASTM Method ||Units ||Typical Value |
|Specific Gravity ||D-792 ||— || 1.08 |
|Water Absorption ||D-570 ||% || 2.5 |
|(24 hr immersion) |
|Hardness ||D-240 ||Shore D || 65 |
|Melting Point ||DSC ||° C. (° F.) ||154 (309) |
|Tensile Strength ||D-638 ||MPa (kpsi) || 50 (7.3) |
|@ Yield |
|Elongation at Break ||D-638 ||% ||350 |
|Flexural Modulus ||D-790 ||MPa (kpsi) ||180 (26) |
|Volume Resistivity ||D-257 ||ohm-cm || 1012 |
We have found that additive materials can significantly improve the properties of the polymer materials in the form of a fine fiber. The resistance to the effects of heat, humidity, impact, mechanical stress and other negative environmental effect can be substantially improved by the presence of additive materials. We have found that while processing the microfiber materials of the invention, that the additive materials can improve the oleophobic character, the hydrophobic character and can appear to aid in improving the chemical stability of the materials. We believe that the fine fibers of the invention in the form of a microfiber are improved by the presence of these oleophobic and hydrophobic additives as these additives form a protective layer coating, ablative surface or penetrate the surface to some depth to improve the nature of the polymeric material. We believe the important characteristics of these materials are the presence of a strongly hydrophobic group that can preferably also have oleophobic character. Strongly hydrophobic groups include fluorocarbon groups, hydrophobic hydrocarbon surfactants or blocks and substantially hydrocarbon oligomeric compositions. These materials are manufactured in compositions that have a portion of the molecule that tends to be compatible with the polymer material affording typically a physical bond or association with the polymer while the strongly hydrophobic or oleophobic group, as a result of the association of the additive with the polymer, forms a protective surface layer that resides on the surface or becomes alloyed with or mixed with the polymer surface layers. For 0.2-micron fiber with 10% additive level, the surface thickness is calculated to be around 50 Å, if the additive has migrated toward the surface. Migration is believed to occur due to the incompatible nature of the oleophobic or hydrophobic groups in the bulk material. A 50 Å thickness appears to be reasonable thickness for protective coating. For 0.05-micron diameter fiber, 50 Å thickness corresponds to 20% mass. For 2 microns thickness fiber, 50 Å thickness corresponds to 2% mass. Preferably the additive materials are used at an amount of about 2 to 25 wt. %. Oligomeric additives that can be used in combination with the polymer materials of the invention include oligomers having a molecular weight of about 500 to about 5000, preferably about 500 to about 3000 including fluoro-chemicals, nonionic surfactants and low molecular weight resins or oligomers. A useful material for use as an additive material in the compositions of the invention is tertiary butylphenol oligomers. Such materials tend to be relatively low molecular weight aromatic phenolic resins. Such resins are phenolic polymers prepared by enzymatic oxidative coupling. The absence of methylene bridges result in unique chemical and physical stability. These phenolic resins can be crosslinked with various amines and epoxies and are compatible with a variety of polymer materials. Examples of these phenolic materials include Enzo-BPA, Enzo-BPA/phenol, Enzo-TBP, Enzo-COP and other related phenolics were obtained from Enzymol International Inc., Columbus, Ohio.
The wipe structures of the invention can be improved using a tackifying resin. The presence of an effective amount of tackifying resin on the substrate or associated with the nanofibers of the invention can improve the tendency of the overall wipe to collect and remove particulate from a soiled surface. Tackifying resins are generally known to add tack in formulated systems. Polymers formulated with a tackifier can obtain temporary or permanent tack to a surface. Tackifying resins are low molecular weight amorphous polymers. Tackifying resins have been applied to formulated adhesives, inks, chewing gums, and other formulated materials. In formulated adhesives, resins are used to generate tack and specifically, adhesion to substrate surfaces. Tackifiers are generally used in combination with a high molecular weight polymeric material that forms the backbone of the adhesive and generate adhesion to substrate surfaces and cohesive character within the polymer and adhesive mass. Formulators typically use such tackifying resins to create the best balance between adhesion and cohesion to optimize adhesive formulations. Tackifying resins can be divided into three groups: hydrocarbon resin, rosin materials and terpene materials. Hydrocarbon resins are typically based on petroleum feed stocks polymerized into low molecular weight materials. Petroleum feed stocks are typically olefinic materials derived from the refining process and are often easily polymerized into low molecular amorphous polymers. Some other ydrocarbon resins are typically based on natural feed stocks obtained from natural plant sources such as pine trees. Terpene resins are generally derived from natural sources, wood turpentine or from Kraft sulfate pulping processes. Rosin (also known as one of the “naval stores”) is one of the oldest raw materials in the adhesive industry. Rosin can be used as derived from natural sources or can be converted into a rosin ester. Three types of rosins are used for resin manufacture. Gum rosin, wood rosin and tall oil rosin are all generated from pine tree and other arboreal sources. Rosin materials, unlike hydrocarbon resins, are not truly polymeric in nature. In fact, they are a blend of different molecules including abietic, pimaric, and other materials derived from terpene-like natural products. The carboxylic functionality in these rosin materials are often esterified using various alcohol materials. The softening point of the subsequent ester can be modified using a selected alcohol material. Often, these resins are esterified with glycerol, pentaerythritol, methanol, triethylene glycol, and other similar relatively low molecular weight mono-, di-, tri- and polyhydroxy alcohol materials. Terpene resins are typically based on resins formed by cationic polymerization of alpha-pinene, beta-pinene and d-limonene feed stocks. These generally pinene feed stocks produce resins of low color and range of softening points.
Low molecular weight hydrocarbon resins can be used as tackifying materials. Hydrocarbon resins are typically made by polymerizing C5 aliphatic resins, C9 aromatic resins, dicyclopentadiene cycloaliphatic resins or mixtures thereof. Feed stocks for manufacturing these resins are typically derived from petroleum feed stocks containing isoprene, cyclopentadiene, dicyclopentadiene, piperylene and other C5 feed stocks. The primary monomers used in C5 resins include various pentadienes, dicyclopentadienes and cyclopentene. In essence, C5 resins are aliphatic materials having both saturated and unsaturated carbon atoms. C9 resins typically are at least partially aromatic in nature since the C9 resins often contain vinyl toluene monomers, dicyclopentadiene monomers, indene monomers, methylstyrene monomers, styrene monomers and methylindene monomers. C9 resins are available in a wide variety of softening points and molecular weights. Hydrogenating these hydrocarbon resins produces another class of hydrocarbon resins that are improved in color and temperature stability of the resins. Hydrogenating these resins removes color and saturates the vinyl residues in the polymer forming substantially saturated carbon atoms. Further, partial and selective hydrogenation can be used to produce a variety of materials with broad saturated carbon, aliphatic carbon and aromatic carbon, compatibility and good thermal and chemical stability. These tackifying resins can be characterized with color, softening point, molecular weight, melt viscosity, thermal stability and compatibility. The preferred resins for use in the wipes of the application are those resins with low odor, water white to low color, storage stability and compatibility with the fine fiber material and the cellulosic or other substrate material.
An extremely wide variety of flexible fabric materials exist for different cleaning and polishing applications. The durable nanofibers and microfibers described in this invention can be added to any of the fabrics. These fabrics can be woven or non-woven. The fabrics can be single layer or multiplayer. Each layer can comprise a single component woven or non-woven fiber or a blended, woven or non-woven fiber. The fabric layers can be combined with an interior non-fiber layer such as a sponge, a scrubbing mesh layer, a film barrier layer or a reservoir layer. The fabrics can be combined with a handle, support or a block to aid in cleaning or polishing. The wipes described in this invention can also be used to substitute for existing fabric wiping materials giving the significant advantage of improved performance. Cleaning and polishing is improved due to their small diameter, while exhibiting greater durability.
The wipe construction according to the present invention includes a first layer of a permeable fabric substrate having a first surface. A first layer of fine fiber is secured to the first surface of the first layer of fabric. Preferably the first layer of fabric comprises fibers having an average diameter of at least 10 microns, typically and preferably about 12 (or 14) to 30 microns. Also preferably the first layer of permeable fabric comprises a layer having a basis weight of no greater than about 100 grams/meter2, preferably about 40 to 80 g/m2, and most preferably at least 20 g/m2. Preferably the first layer of permeable fabric is at least −0.008 inch (200 microns) thick, and typically and preferably is about 0.01 to 0.05 inch (103 microns) thick.
The microfiber or nanofiber of the unit can be formed by the common electrostatic spinning process. Barris, U.S. Pat. No. 4,650,506, details the apparatus and method of the electro spinning process and is expressly incorporated herein by reference. Apparatus used in such process includes a reservoir in which the fine fiber forming polymer solution is contained, a pump and a rotary type emitting device or emitter to which the polymeric solution is pumped and applied. The emitter generally consists of a rotating portion. The rotating portion then obtains polymer solution from the reservoir, and as it rotates in the electrostatic field, the electrostatic field, as discussed below, accelerates a droplet of the solution toward the collecting fabric surface. Facing the emitter, but spaced apart therefrom, is a substantially planar grid upon which the collecting surface (i.e. fabric or multilayer of multifiber fabric is positioned. Air can be drawn through the grid. The collecting surface is positioned adjacent opposite ends of grid. A high voltage electrostatic potential is maintained between emitter and grid by means of a suitable electrostatic voltage source.
In use, the polymer solution is pumped to the rotating portion from reservoir. The electrostatic potential between grid and the emitter imparts a charge to the material that cause liquid to be emitted therefrom as thin fibers which are drawn toward grid where they arrive and are collected on substrate fabrics. In the case of the polymer in solution, solvent is evaporated off the fibers during their flight to the grid; therefore, the fibers arrive at the fabric. The fine fibers bond to the fabric fibers first encountered at the grid. Electrostatic field strength is selected to ensure that the polymer material as it is accelerated from the emitter to the fabric; the acceleration is sufficient to render the material into a very thin microfiber or nanofiber structure. Increasing or slowing the advance rate of the collecting fabric can deposit more or less emitted fibers on the forming fabric, thereby allowing control of the thickness of each layer deposited thereon.
The wipe of the invention can be pre-moistened (i.e.) combined with a liquid material and packaged in a container that maintains the wipe inn its pre-moistened condition. The container can comprise a single use envelope or a multiuse pop-up dispenser or related containers. The liquid materials can include cleaners, disinfecting solutions, decontaminating solutions, coating solutions, wax coating solutions, cosmetic solutions, human deodorant solutions, facial moisturizers, facial cleaners, make-up removing solutions and other materials. Virtually any liquid cleaner composition or composition that can lay down a smooth coating can be combined with the wipes of the invention.
The liquid material used for the wipe of the invention can be an aqueous based or solvent based material. Aqueous based materials are typically manufactured by combining the active ingredient or formulation in an aqueous base. The aqueous base of the material can include solvent materials that are soluble or dispersible in the aqueous media. Such liquid materials used in the wipes of the invention can also be based on solvent chemistry. Such solvents include alcohol, light petroleum distillate, ketones, ethers and other typically volatile solvent materials. Such liquids can also contain some small proportion of an aqueous material that can be either dissolved or suspended in the solvent solution.
The liquid compositions of the invention can include surfactant materials, chelator materials, disinfectants, sanitizers, bleaches, lubricants, and other active materials that can act to either remove soil from surfaces or to provide a coating on the clean surfaces after soil removal. One important embodiment of the wipe of the invention includes a wipe that can form a useful coating on surfaces. Such coatings can comprise a wax, a polymeric material, a silicone wax or other coating material. One important advantage of the wipes of the invention is the nanofiber material on the wipe can obtain an improved surface characteristic due to the small fiber size of the wipe fine fiber layer. As the coating material is laid down by the wipe during cleaning or cleaning and coating, the fine fiber size tends to form a coating layer with substantially reduced defect size in the coating layer resulting in an improved surface gloss or smoothness. Glass cleaner materials can include isopropanol and ammonium hydroxide and ether solvents such as 2-butoxyethanol and ethylene glycol n-alkyl ether. A polish and cleaner can include paraffinic hydrocarbon solvent, silicone, naphtha solvent (petroleum distillate). Skin cleaner can include water, propylene glycol, PEG-75 Lanolin, Disodium anionic surfactant, Polysorbate materials, Methylparaben, 2-Bromo-2-Nitropropane-1, 3-Diol, Fragrance, etc. Facial cleaner wipes can include water, alcohol (10%), butylene glycol, laureth-(EO)x nonionic, phenoxyethanol, salicylic acid, panthenol, propylene glycol, PEG-7, glyceryl cocoate, fragrance, PEG-substituted hydrogenated castor oil, disodium EDTA, benzoic acid, fragrance, menthol, t-butyl alcohol, etc. Hard surface cleaner wipes can contain quaternary ammonium compounds. Make-up remover wipes can include water, alkylene glycol, glycerin, herbal extract, vitamin-E acetate, aloe vera, panthenol, ginseng (panax ginseng) extract, anionic surfactant, benzyl alcohol, PEG-40 hydrogenated castor oil, alkylene glycol, polysorbate 20, fragrance, citric acid and DMDM hydantoin. Disinfectant wipes can include sodium hypochlorite, ethyl alcohol, Quats, etc.
Examples 1,2 and 3 show the preparation of a nanofiber layer on a wipe substrate. The wipe is tested for cleaning properties on automotive surfaces to test the cleaning properties of the material with organic and inorganic particulate soil.
- Example 1
The wipe substrate material used for the following examples was made from a blend of cellulose and polypropylene fibers, blended in such a way as to make one side of the material predominantly cellulose, while the other side of the material is predominantly polypropylene. The composite material has a basis weight of approximately 58 grams per square meter and a thickness of approximately 0.016 inch.
- Example 2
Polyamide fibers were electrospun onto the polypropylene-rich side of a blended fiber wipes material (blend of polypropylene and cellulose). The fiber size was 0.25 micron having a basis weight of the nanofiber application was approximately 0.21 g-m−2. The resulting material was then used to wipe the dash panel of a 1995 Ford Contour (nanofiber side in contact with the windshield), by swiping the material across the dash panel, back and forth, 3 times in an approximate 14″ path. The SEM's and analysis associated with this test are shown in FIGS. 1-4.
- Example 3
Polyamide fibers were electrospun onto the polypropylene-rich side of a blended fiber wipes material (blend of polypropylene and cellulose). The basis weight of the nanofiber application was approximately 0.21 g-m−2, with a fiber size of approximately 0.25 microns. The resulting material was then used to wipe the interior windshield of a 1995 Ford Contour (nanofiber side in contact with the windshield), by wiping in a circular motion (approximate 8″ diameter circle) 3 times, followed by wiping back and forth over the same area of the windshield 3 times, in a 10″ path. The SEM's and analysis associated with this test are FIGS. 5-11.
- Automotive Dash Testing
Polyamide fibers were electrospun onto the cellulose-rich side of a blended fiber wipes material (blend of polypropylene and cellulose). The basis weight of the nanofiber application was approximately 0.21 g-m−2, with a fiber size of approximately 0.25 microns. The resulting material was then used to wipe the dash panel of a 1995 Ford Contour (nanofiber side in contact with the windshield), by swiping the material across the dash panel, back and forth, 3 times in an approximate 14″ path. The scanning electro micrographs and analysis associated with this test are shown in FIGS. 12-17.
Nanofibers were applied to the polypropylene side of the two layer cellulosic/polypropylene material. The wipe was tested by its use in an automobile and was wiped on a vehicle dash.
- Automotive Window Testing
In FIG. 1, at ×200 magnification, we see dirt, particulate 10 sized as 50-70 μm, with many much smaller particulate in the nanofiber web 11. Fabric substrate 12 is shown in the background. Much of the nanofiber web 11 is discontinuous and dirt covered. In FIG. 2, at ×1500 magnification, we see soil particles 20 and nanofiber 21 wound and bound together with substrate fabric fiber 23 in background. Some portion of the particles is held in nanofiber/particulate bundle 24. Other particulate 25 is adhered to the surface of the nanofibers, presumably through Van der Waal's forces. In FIG. 3, at ×5000 magnification, we can see dirt particulate 30 bundled in the discontinuous nanofiber web 31. In FIG. 1, at ×200 magnification again, in places where the nanofiber web is gone, dirt is migrated into the depth of the substrate past the nanofiber layer where particulate wedges between fibers. Small particles are clearly preferentially retained by nanofiber versus larger particulate in larger fibers. In FIG. 4, at ×10,000 magnification, dirt particulate 40 is shown wound up in nanofiber 41. We see particles 42 about 0.2 μm in size.
Sample is nanofibers applied to the polypropylene side of the two layer non-woven, wiped on vehicle interior window.
- Automotive Window Testing
In FIG. 5, at ×200 magnification, we see much less dust and dirt 52, than FIGS. 1-4, most of the nanofiber web 50 is still substantially intact due reduced abrasion from particulate from a cleaner surface. Fabric substrate fiber 51 is in background. In FIG. 6, at ×2500 magnification, we see an area of rolled-up nanofiber 60 adjacent to nanofiber web 62, with a coating of agglomerated substantially organic soil or contaminant 61 on the nanofiber. The window soil is not largely inorganic particulate, but is greasy, organic matter that coats the fiber as compared to the dry particulate on the dash that is enmeshed by or entangled in the nanofiber. The organic soil is easily picked up by the nanofiber web, which provides a substantial of surface area contact and a compatible surface. In FIG. 7, at ×10000 magnification, we see a close-up picture of the organic soil 61 coating the fiber with adjacent nanofiber 70 and web 71.
In FIG. 8 at ×200 magnification, we see most of the web structure 80 intact, with little particulate 81 or contaminant.
- Automotive Dash Testing
In FIG. 9 at ×1000 magnification, we see some contaminant particles 90 on the web 91, some on the fiber of substrate surface 92. We can also see areas where nanofiber web is discontinuous. The large substrate fiber 92 without a nanofiber covering suggests that it has moved from its original location, driving, wiping. There is also evidence of organic contaminant 93 collected on the nanofiber web portion bonded to the substrate fibers. In FIG. 10 at ×4000 magnification, we see organic contaminant 100 on nanofibers 101, as well as some particulate 102 that has been captured/wedged behind the nanofiber structure. In FIG. 11 at ×17000 magnification, we see the captured/wedged particle 102 behind nanofiber 110. We can discern contaminants as small as 0.05-0.1 μm. There is also a coiled-up section of nanofibers agglomerated with particles and organic soil 111 bundled in a fiber web.
Sample is nanofibers on pulp side wiped on dash.
- Automotive Dash Testing
FIG. 12 at ×200 magnification, we see that more of the nanofiber web is intact than samples in FIGS. 1-4. There is a lot of particulate 120, some areas of exposed substrate fiber 121 and discontinuous nanofiber web 122. FIG. 13 at ×1000 magnification, we see that many particles 130 are collected on the nanofiber web surface 131, but that some particles 132 have been captured between the nanofiber layer and the substrate fibers or in the fabric. Particulate can move into the depth through nanofiber web hole and migrate behind. FIG. 14 at ×4000 magnification, we see a close-up of the particle 132 behind the web 140, with other particulate 141 on top. Particulate 142, as small as 0.5 μm, can be seen held or entangled in the fiber. FIG. 13 at ×1000 magnification again, we see a particle underneath the nanofiber web, as far as 50 μm away from a hole large enough to allow its passage.
Sample is nanofibers applied to pulp side, wiped across dash.
In FIG. 15 at ×200 magnification, we see most of nanofiber web 150 intact with some holes 151 and discontinuous areas. In FIG. 16 at ×1500 magnification, we see a few particles 160 wrapped up in nanofibers 161. We see a large (20-30 μm) particle 162 sitting on top of the nanofiber web. We see a large substrate fiber 163 that has captured few a particles 164 on its surface. In FIG. 17 at ×6000 magnification, we see a close-up of the captured particles 160 and the nanofiber web 161. In FIG. 16 at ×1500 magnification again, we see a particle lodged underneath the nanofiber web. This particle is perhaps 30 μm away from the nearest web discontinuity that is sufficiently sized to allow its passage.
In previously filed applications, the formation of fine fiber layers on filtration media has been disclosed. Such filter structures are different than a wipe structure. In order to establish a clear distinction between a wipe material and a filtration structure, a number of consumer wipe materials were purchased and tested for stiffness characteristics. Filtration media must have characteristic stiffness to operate in the filtration environment in which a stream of liquid or gas passes through the filter and particulate is removed. The media must be stiff enough to survive the mechanical stress placed on the filter media by the moving fluid. Both dry and wet wipes were tested. Wet wipes were washed and dried before testing for stiffness.
Wipes substrates tested—wet (all were soaked in filtered deionized water at room temperature for 10 minutes, with three water change-out, then dried in an oven at 85° C. for 10 minutes). Rain-X Glass cleaner with Anti-Fog Wipes—Rain-X; Rain-X Wipes; Wet Ones Antibacterial Wipes—Playtex Products Inc. Pledge Wipes—S.C. Johnson & Son, Inc. Clorox Disinfecting Wipes—The Clorox Company Windex Glass and Surface Wipes—S.C. Johnson & Son, Inc. Clean & Clear Deep Action Cleansing Wipes_Johnson & Johnson Pond's Cleansing and Make-Up Remover Towelettes—Chesebrough-Pond's USA Co. Wipes materials tested—dry Swiffer disposable cloths—Proctor & Gamble Pledge Grab-It dry cloths—S.C. Johnson & Son, Inc. Each sample was tested for stiffness according to TAPPI T-543 om-00: “Bending Resistance of Paper (Gurley-Type Tester)”. In performing the test, a bending resistance/stiffness test instrument is used that consists of a balanced pendulum or pointer which is center-pivoted and can be weighted at three points below its center. The pointer moves freely in both left and right directions on cylindrical jewel bearings which make the mechanism highly sensitive even to light-weighted materials.
A sample of a specific size is attached to a clamp, which in turn is located on a motorized arm, which also moves left and right. The bottom 0.25 inch of the sample overlaps the top of the pointer (a triangular shaped “vane”). During the test the sample is moved against the top edge of the vane, moving the pendulum until the sample bends and releases it.
On digital models, the point of release is automatically measured by an optical encoder and displayed on a digital readout. this readout continuously displays readings from tests performed in both the left and right directions. In addition, the on-board microprocessor automatically computes and displays the average of left and right stiffness data after each measurement is performed. For flat sheet materials, the operator can then press a button to automatically convert the point-of-release reading on the display to force (milligrams).
However, none of the material samples had sufficient stiffness to be measured using this method. The minimum stiffness value that can be accurately measured on this Gurley stiffness tester is approximately 300 mg. As such, the stiffness of each of these materials is known to be less than 300 mg. Typical stiffness values for other filter media types are about 350-12,000 mg.
The foregoing constitutes a complete description of the embodiments of the invention recognized to date. However, since the invention can reside in a variety of embodiments without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.