Patent Application
20160009093
The present invention is directed generally to a fluid cleaning textile for use in lithographic and ink jet printing systems. More specifically, the present invention is directed to a non-woven textile which is usable as an image transfer surface cleaning device in lithographic printer machines and as an inkjet nozzle-cleaning device in inkjet printer cleaning systems. Even more specifically, the present invention is directed to a non-woven textile largely comprised of low denier splitable staple fibers for use in lithographic blanket and cylinder ink-cleaning devices and in inkjet nozzle ink-cleaning cassettes. The non-woven fabric is manufactured utilizing at least 80 percent, by weight, splitable fibers each of less than 100 mm in length and which are purposely structured to become less than one denier in size during processing into a finished non-woven. Such a non-woven has a mass per unit area in the range from 20 grams per square meter (gsm) to 500 gsm and a measured air permeability value from 2 cubic feet per minute at ½ inch of water pressure (CFM), to 500 CFM. The present non-woven fabric most preferably has a peak tensile strength to mass per unit area ratio of at least 2.90 Newtons per 5 centimeters per GSM.
It is generally known in the art to use fabrics as cleaning media for printing machines. An inkjet printing machine cleaning fabric in disclosed in U.S. Pat. No. 6,957,881 to Nishina et al which describes the need to periodically maintain inkjet nozzle cleanliness and recites the use of a high density 0.1 denier fiber woven textile as a preferred media for an ink wiping device. Nishina does not disclose a specific fiber length nor make reference to a non-woven but does disclose the need for a cleaning fabric in an inkjet printing machine. A lithographic printer machine cleaning media is marketed as DuPont Sontara® PrintMaster and is advertised as providing a superior performance lithographic printer machine cleaning media due to its high absorbency, low linting, and high strength characteristics. Additionally, U.S. Pat. No. 5,974,976 to Gasparrini et al describes a reduced air content nonwoven fabric which is usable for cleaning various cylinders within a lithographic printing machine. Although Gasparrini does not claim any fiber detail comprising the non-woven, Sontara® is asserted as utilizing staple fibers which are equal to or more than 1 denier in size.
There is a continuing need to reduce printer machine down-time which, for the printer operator, equates to less waste, lower costs, less maintenance, and potentially higher profitability. A common configuration for a printer machine cleaning non-woven textile within a lithographic printer machine is in the form of a roll, which is installed into a housing cassette that is usable for periodically unwinding clean material, for delivering the clean non-woven material to the area requiring cleaning, and for rewinding consumed material within the cassette. Common configurations for printer machine cleaning non-woven materials within an inkjet printer encompass the aforementioned one, as well as rolls which do not unwind during use, continuous loop shapes, pads, or sheets, all of which are installed into a housing cassette which delivers the non-woven to the area requiring cleaning. The surface being cleaned in both lithographic and inkjet printer machines requires a non-woven to readily absorb fluid, to mechanically scrub and remove particulate from a surface, and also to retain the removed fluids and particulates, all without either depositing components of what comprises the non-woven or re-depositing any of the removed fluid and particulate.
It is common, in the prior art, to add woodpulp fibers to the composition of a non-woven to provided necessary absorbency. DuPont Sontara® PrintMaster acquires its high fluid absorbency through the use of a select amount of cellulose or woodpulp type fibers which are purposefully added to the non-woven construction. These natural fibers are well known to provide rapid and substantial absorbency similar to a “paper towel” used commonly for various applications. The limitation of this fiber type is its inherent nature to shed or to release portions of the woodpulp fibers upon contact with certain abrasive printer machine surfaces such as sharp nozzle plates, tacky rollers, or rough rollers, thus creating the need for an improved low-lint textile. Using synthetic man-made fibers and excluding the woodpulp content, as described in U.S. Pat. No. 7,745,358 to Benim et al, provides the ability to increase the shed resistance of a nonwoven by utilizing entirely synthetic fibers, such as polyester or poly(ethylene terephthalate).
It is also known to use continuous length filaments rather than staple fibers as one method to prevent fiber shed or fiber deposit. European patent 1,753,623 to Howey et al describes using a continuous filament synthetic construction which is thermally point-bonded to provide increased shed resistance. The two devices previously mentioned in European patent 1,753,623 to Howey et al, and U.S. Pat. No. 7,745,358 to Benim et al, increase the shed resistance of a non-woven but both discuss the use of thermal bonding to adhere the various components, when creating the final non-woven. Thermal bonding relies on a specific component of the non-woven to change phase from a solid to liquid and to then return to a solid. However, while this component is in the liquid phase, it tends to flow into adjacent components, thus acting as an adhesive within the non-woven structure. This reduces void space within the non-woven structure and also reduces fiber surface area, both of which negatively affect fluid absorbency and textile cleaning ability. If thermal point-bonding is not used in the construction of continuous length filament non-wovens, then these filaments are produced using the spunbond process which typically results in non-wovens having larger denier fibers. Such larger denier fibers will adversely affect mechanical cleaning ability or, if they are micro-denier sized, they can break and shed similarly to woodpulp containing non-wovens.
Freudenberg's Evolon® is an example of a micro-denier, continuous filament, cleaning non-woven and is detailed in U.S. Pat. No. 6,706,652 to Groten et al. BMP America first utilized Evolon® for lithographic and inkjet printer cleaning applications in 2004, recognizing that sub-denier or micro-denier splitable continuous filaments are preferred due to the amount of available surface area each fiber provides per surface area of finished textile. This high amount of available filament surface area provides a high amount of void space in which fluid can readily be absorbed. This is also supported by U.S. Pat. No. 7,745,358 Benim et al which also describes the addition of up to 10 percent of splitable staple micro-fibers to increase non-woven absorbency. When micro-denier splitable continuous filaments are highly entangled such as in Evolon®, the opportunity for a filament to break and shed exists but resistance to shed is much improved. Therefore, such micro-denier splitable continuous filaments have proven to be a viable option as a printer machine cleaning non-woven. However, they are challenging to manufacture and thus are costly. They also exhibit poor uniformity at lower basis weights.
The caliper thickness of such a non-woven, when used in a printer cleaning system, has a direct impact on the quantity of textile which can be contained within the delivery cassette. One way to decrease caliper thickness is to squeeze or calendar the non-woven to a lower caliper thickness value, as described in U.S. Pat. No. 5,974,976 to Gasparrini et al. However, calendaring often adds cost to a process, thus increasing final non-woven cost. It will thus be seen that a need exists for an improved non-woven which has the ability to mechanically scrub a surface, to present a uniform surface area, to absorb and retain waste, to resist shedding, to allow for quantitatively more non-woven within a given space, and to provide a cost advantage, all while meeting prior art non-woven strength specifications.
An object of the present invention is to provide a non-woven textile suitable for use as a waste cleaning device for use in lithographic and inkjet printing machines.
Another object of the present invention is to provide a non-woven textile useable as a cleaning device for collecting and containing printer-ink.
Yet a further object of the present invention is to provide a printer-ink cleaning device that provides uniform and efficient removal of waste ink from an inked surface that is superior to prior art.
Typically, waste ink accumulates over time on a roller, cylinder, jacket, or print-blanket surface within a lithographic or offset printer. In accordance with the present invention, the non-woven fabric, when used as a lithographic printer ink cleaning device, can contact a surface which contains waste ink, will quickly remove such waste ink, and will resist fiber shed resulting from such contact with the surface containing the waste ink.
Inkjet printing typically relies on nozzles to spray atomized ink onto a printing media. Over time, these inkjet nozzles will collect excess ink and will also collect dust and other environmental contaminants, all of which need to be periodically cleaned and removed. In accordance with the present invention, the non-woven fabric, when used as an inkjet printer ink cleaning device, can contact a surface which contains waste ink and contaminants, such as a nozzle, will quickly remove such waste ink, and will resist fiber shed resulting from such contact with the surface containing the waste ink.
The present invention is directed to hydroentangled non-wovens which are formed from splitable staple fibers and which are suitable for use as strong, cost effective, and improved cleaning performance textiles that are utilized within offset and inkjet printing machines to clean various inked surfaces. The non-wovens have the ability to match or to surpass the cleaning ability of a continuous filament micro-denier non-woven, to surpass the tensile strength per unit mass ratio of commercially available printer machine cleaning non-wovens, to surpass the fiber uniformity of continuous filament non-wovens, to surpass the shed resistance of a continuous filament micro-denier non-woven and woodpulp or cellulose containing non-wovens, to match or surpass the absorbency of wood-pulp or cellulose containing non-wovens, and to be cost competitive in the commercial marketplace.
An important characteristic of the non-woven fabric in accordance with the present invention is its tensile strength to mass per unit area ratio. This value is determined by dividing the peak tensile strength of the non-woven by the weight per unit area of that non-woven. As an arbitrary numerical example, if a non-woven sample has a measured weight of 50 grams per square meter (gsm) and is measured to have a peak tensile strength of 100 Newtons per 5 centimeter (N/5 cm), that non-woven has a strength to weight ratio of 2 N/5 cm/gsm. Superior tensile strength to mass per unit area ratios indicate a higher entanglement of fibers and an overall improved non-woven construction, fiber structure, and uniformity.
Another important characteristic of the non-woven fabric of the present invention is the fiber size, quantified by denier and length, which comprises the non-woven. The fiber size is obtained by utilizing purposefully made splitable staple fibers of less than 100 mm in length and by mechanically processing the splitable fibers to obtain a highly tangled and uniform non-woven fabric largely consisting of fibers which have become smaller than one denier due to processing. Fibers which are smaller than one denier will be referred to as microdenier fibers and are synonymous with the term microfiber.
Splitable microdenier continuous filaments, as opposed to staple fibers, were introduced to ink cleaning applications by BMP in 2004 based on the recognition of the high amount of available surface area per unit volume of such filaments, which allowed for superior cleaning and fluid absorbency. This structure is also mechanically tough. However, an inherent limitation of non-wovens which contain continuous filaments is poor uniformity, when produced in relatively low basis weights and particularly in weights of less than 80 grams per square meter. The use of a split staple microfiber provides the non-woven of the subject invention with a uniform distribution of mass per unit area and a mechanically tough structure due to the staple fiber's ability to entangle in three dimensions within the textile versus a more typical two dimensional entanglement, which is common among non-wovens which contain continuous filaments. The high degree of staple microfiber entanglement and uniformity is also present when producing textiles at basis weights of less than 80 grams per square meter, which is the weight range where continuous microfiber textiles struggle.
Uniform distribution of mass within the non-woven is a direct result of the ability to process the staple fiber through a non-woven carding machine. The carding machine parameters and the staple fiber length are both specified to provide improved distribution, while longer fibers or other processes for creating a non-woven structure, such as the spunbond process, adversely affect mass distribution. After the splitable staple fibers are further processed and are split into smaller microdenier fibers, the mass distribution uniformity is only improved beyond the carding machine capability.
One way of measuring such uniformity is to test and to record air permeability at various locations throughout the finished textiles and to then compare the standard deviation of readings between the different textiles. The split staple microdenier textile, in accordance with the present invention, has a much lower standard deviation, which correlates to higher uniformity. The increased uniformity of microfibers, per unit area of the non-woven, provides a highly tangled structure which is shed resistant and mechanically superior, when compared to similar non-woven structures which are composed of larger denier or of continuous length fibers. The uniform structure also provides a strong capillary force which results in the non-woven having an affinity for ink in printer cleaning applications.
Capillary force in a non-woven is a function of the surface tension of fluid with respect to fiber type, of the contact angle of the fluid on the fiber and of the fiber surface area per unit volume of the non-woven. Capillary force in a non-woven is analogous to capillary head in a vertical capillary tube. This is based on the concept that the space between the fibers in the non-woven can be approximated as a vertical capillary tube. The equation for force in a vertical capillary tube is given as follows:
F=2πrσLV cos θLS
where,
where,
The splitable staple fiber non-woven in accordance with the present invention overcomes the limitations of the prior materials. It is a substantial advance in the art.
While the novel features of the splitable staple fiber non-woven useable as an ink cleaning device in accordance with the present invention are set forth with particularity in the appended claims, a full and complete understanding of the invention may be made by referring to the detailed description of the preferred embodiments, as presented subsequently, and as illustrated in the accompanying drawings in which:
The term non-woven, as used herein, refers to a textile without a specified pattern or quantity of fibers or filaments oriented in specific axes of the textile surface. The term can also be defined as the opposite structure of a knitted or woven textile structure.
The term hydroentangled, as used herein, describes a non-woven manufacturing method in which the fibers are locked into place and entangled using high pressure fluid jets.
The term splitable, as used herein, is used to describe a fiber that reduces its size when processed through a variety of steps. The fiber is typically composed of more than one polymeric substance contained within the same filament and is formed in a way such that the multiple polymers are segmented and separable by chemical or physical means. Common splitable fiber cross section structures include, but are not limited to, segmented pie, “islands in the sea,” segmented tri-lobes, segmented cross, segmented ribbons, striped round fibers, hollow fiber core, and hollow segmented pie. Common polymers used include, but are not limited to, polyethylene terephthalate (polyester or PET), co-polyester, Polyamide (Nylon 6 or Nylon 6,6), polypropylene, polyethylene, and polyvinyl alcohol.
The term staple is used to describe a natural fiber or a finite length synthetic fiber which has been cut from a filament. Typical cut length of the staple fiber is between 0.2 inches and 6 inches.
In this first example, 51 mm long EASTLON 2.0 denier mechanically splitable staple microfibers, composed of polyester and nylon, are processed through a bale opening machine (2 in
The result is a splitable staple microfiber 63 gram per square meter (gsm) textile (ASTM D-461 Section 11) with a thickness of 0.39 millimeters (ISO 9073-2) and an average peak tensile strength, in the machine direction, of 269 Newtons per 5 centimeters (N/5 cm) (ASTM D-5035-11). The ratio of this peak strength to weight is 4.27 N/5 cm per gsm. In comparison, Freudenberg's prior art Evoion®, at a weight of 60 gsm, has a measured average peak tensile strength, in the machine direction, of 165 N/5 cm and a strength to weight ratio of 2.75 N/5 cm per gsm. Air permeability testing is one way to compare material uniformity. As discussed previously,
The splitable staple fiber three dimensional entanglement of the present invention provides much better resistance to shed than does Freudenberg's prior art Evolon® which is more two dimensionally entangled. Abrasion resistance of the present invention textile was compared to that of Evolon® using a model 5130 Taber Abraser from Teledyne Taber, North Tonawanda, N.Y. Weight loss per unit area abraded was recorded in milligrams per square centimeter (mg/CM2) and thickness loss was recorded in millimeters and was converted to percent thickness loss. Samples were tested for 100 cycles using an H-18 abrasion wheel with 1500 grams of total weight on each arm. The target 60 gsm textile of the present invention lost 113 mg/cm2 and 16.0% of its original thickness while Evolon® 60 gsm lost 321 mg/cm2 which is a factor of 2.8 times the 60 gsm textile amount, of the present invention and lost 22.4% of the original thickness which is a factor of 1.4 times the 60 gsm textile amount of the present invention. Thus, the present invention, of a splitable staple fiber non-woven has an improved tensile strength to mass per unit area ratio, improved uniformity, and improved resistance to shed while maintaining the prior art non-woven ability to mechanically scrub a surface and to absorb and retain waste.
In this example, 51 mm long EASTLON 2.0 denier mechanically splitable staple microfibers, composed of polyester and nylon, are processed through a bale opening machine (2 in
The result is a splitable staple microfiber, 38 gram per square meter (gsm), textile (ASTM D-461 Section 11) with a thickness of 0.27 millimeters (ISO 9073-2) and an average peak tensile strength, in the machine direction, of 154 Newtons per 5 centimeters (N/5 cm) (ASTM D-5035-11). The ratio of this peak strength to weight is 4.05 N/5 cm per gsm. Recall that Freudenberg's prior art Evoion®, at a weight of 60 gsm, has a measured average peak tensile strength in the machine direction of 165 N/5 cm and a strength to weight ratio of 2.75 N/5 cm per gsm. As discussed,
In this example, 51 mm long EASTLON 2.0 denier mechanically splitable staple microfibers, composed of polyester and nylon, are processed through a bale opening machine 2 and a carding machine 3 to uniformly spread the fibers across the width of a moving belt 4. The belt 4 transports the web of fibers or multiple layers of webs 5, targeting a total final weight of 170 grams per square meter, to a series of high pressure water jets 8 and perforated cylinders 7. Water jet orifices of the water jets 8 are spaced between 0.5 mm and 1.0 mm apart with diameters ranging from 100 to 160 microns. Pressures of approximately 200 bar are used to split and to three-dimensionally entangle the splitable staple microfibers at multiple hydroentangling stations along the production path. The resultant split and entangled textile is then vacuum dried, using vacuum system 9, squeezed using rollers 10, and heated in drying system 11 to remove all water content.
The result is a splitable staple microfiber, 162 gram per square meter (gsm), textile (ASTM D-461 Section 11) with a thickness of 0.76 millimeters (ISO 9073-2) and an average peak tensile strength, in the machine direction, of 595 Newtons per 5 centimeters (N/5 cm) (ASTM D-5035-11). The ratio of this peak strength to weight is 3.67 N/5 cm per gsm. Freudenberg's prior art Evolon® at a weight of 160 gsm, has a measured average peak tensile strength, in the machine direction, of 417 N/5 cm and a strength to weight ratio of 2.61 N/5 cm per gsm, once again demonstrating that the subject invention provides a splitable staple fiber nonwoven matching or surpassing the strength of a continuous filament nonwoven. Thus, the present invention provides a splitable staple fiber non-woven which has an improved tensile strength to mass per unit area ratio while maintaining the ability of the prior art non-woven to mechanically scrub a surface and to absorb and retain waste.
While preferred embodiments of a Splitable staple fiber non-woven useable as an ink cleaning device, in accordance with the present invention, have been set forth fully and completely hereinabove, it will be apparent to those persons skilled in the art that various changes and modifications may be made without departing from the spirit and scope thereof which is accordingly limited only by the following claims.
