Gas separation – Flexible or collapsible bag type – Seaming – reinforcing or bag structure
Reexamination Certificate
2000-04-28
2002-05-28
Simmons, David A. (Department: 1724)
Gas separation
Flexible or collapsible bag type
Seaming, reinforcing or bag structure
C055S486000, C055S487000, C055SDIG002, C015S347000, C015S352000
Reexamination Certificate
active
06395046
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention concerns a dust filter bag which has at least one non-woven tissue and at least one layer of carrier material.
The requirements for the performance of filters of the filter bags which are used in modern vacuum cleaners have been clearly increased in recent years. Above all ever greater significance is attributed to the field of the removal of fine particles, because this not only corresponds to the increased consciousness of hygiene, but—against the background of the increasing number of sufferers from allergy and in particular the number of those allergic to household dust—the exit air from the vacuum cleaner should be as far as possible composed of few allergy carriers. In order to achieve the aim of improving the deposit of fine particles, in recent years numerous efforts have been made which were aimed at the development of new materials, bag designs and filter systems. For example, three layered filter bags were produced or downstream fine particle filter elements were used as the ejection filter. The disasdvantages of these versions are either to be found in the inadequate improvement of the precipitation of the fine particles or in a strongly increased filter resistance, which leads to a reduced suction power of the device.
A major step forward in the improvement of the fine particle precipitation, a few years ago, was the development of the meltblown fine non-woven tissues and their use in special vacuum cleaner bags. These fine fiber components make possible a clear alleviation for those allergic to household dust due to the purer blow out air of the vacuum cleaner. Thus today in the United States, already about 25% of the dust filter bags are produced with a meltblown fiber layer, with increasing tendency.
2. Discussion of the Prior Art
The basic structure of such bags is shown in patents DE 38 12 849, U.S. Pat. Nos. 5,080,702 and 4,589,894. As is disclosed in DE 38 12 849, such meltblown fiber layers have typically a fiber diameter of 0.5 to 18 microns, a basic weight of 10 to 50 g/m
2
, and an air permeability of 200 to 1500 l/m
2
×s. However, from the view point of today, these dust filter bags have a disadvantage: although a high filter precipitation performance is achieved, these technologies have their limits to the extent that further improvement of the finest particle precipitation inevitably makes it necessary to increase the basis weight of the fine particle filter layer, which simultaneously has a strongly negative influence on the filter resistance and therefore on the suction power of the devices. These negative effects increase to the same extent as the precipitation of the finest particles is improved. In addition, due to the increase in the basis weight of the meltblown layer for the improvement of the finest particle precipitation, the processing of these filter combinations is complicated, because the meltblown layer, due to its structure, causes strong reset forces, which complicate the folding of the filter laminate to form a flat dust filter bag, particularly in the zone of the wound base which closes the bag.
A different technology, which is used above all in Europe because of the different design features of the European vacuum cleaner, includes the concept of the micro exhaust filter, which is downstream from the dust filter bag on the exhaust air side. High quality exhaust air filters meanwhile consist of cassette designs with pleated filter elements. The technical drawback of these extensive versions is also to be found in an increased filter resistance for the totality of the filter system, in comparison with systems without micro exhaust air filters, of filter bags and exhaust air filters, whereby in this case as well the suction power of the devices is strongly adversely affected. In addition there is the fact that due to the dust throughput degree of the filter bag, the stoppage degree of the downstream exhaust air filter increases with increasing time in use, whereby an additional adverse effect results for the suction power of the device. In order to exclude these disadvantages, multifareous tests have been made, to adjust the precipitation power of the filter system above all for fine particles to the high level which has been achieved and at the same time clearly to reduce the adverse effect on the suction power, but until now without the desired success.
SUMMARY OF THE INVENTION
The invention is based on the object of producing a dust filter bag with an especially good degree of dust precipitation for the finest particles below 0.5 microns in size, which at the same time has a low initial filter resistance and a small tendency to stoppage, whereby a high suction power of the vacuum cleaner remains, even with increasing filling of the dust filter bag during use.
In accordance with the invention, the object is attained by a dust filter bag which has at least one layer of carrier material and at least one non-woven tissue layer, in which the at least one layer of non-woven tissue has a nano non-woven tissue layer with an average fiber diameter of 10 to 1000 nm, preferably 50 to 500 nm, a basis weight (ISO 536) from 0.05 to 2 g/m
2
, preferably from 0.2 to 0.5 g/m
2
, and an air permeability (ISO 9237) of 1500 to 20000 l/m
2
×s, preferably from 2000 to 10000 l/m
2
×s, and the at least one carrier material layer has an air permeability (ISO 9237) of more than 70 l/m
2
×s, preferably from 200 to 900 l/m
2
×s, a breaking resistance (ISO 1924-2) in the longitudinal direction of more that 20 N/15 mm strip width, preferably of more than 35 N/15 mm strip width, and in the transverse direction of more than 10 N/15 mm strip width, preferably of more than 18 N/15 mm strip width.
The term which is used here “nano fibers” makes it clear that the fibers have a diameter in the nano meter range, specially from 10 to 1000 nm, preferably from 50 to 500 nm.
The nano non-woven tissue which is used in accordance with the invention consists due to the production process usually of soluble or thermoplastic polymers, which are soluble in water and in an organic solvent.
Special preference is given to polymers soluble in water such as polyvinyl alcohol, polyvinyl pyrolidon, polyethylene oxide or copolymers thereof, cellulose, methyl cellulose, propyl cellulose, starch or mixtures thereof.
The polymers specially preferred which are soluble in an organic solvent are polystyrene, polycarbonate, polyamide, polyurethane, polyacrylate, polymethacrylate, polyvinyl acetate, polyvinyl acetal, polyvinyl ether, cellulose acetate or copolymers or mixtures thereof.
Specially preferred thermoplastic polymers are polyethylene, polypropylene, polybutene-1. polymethyl pentene, polychloro trifluoroethylene, polyamide, polyester, polycarbonate, polysulfon, polyether sulfon, polyphenylene sulfide, polyacryl nitrile, polyvinyl chloride, polystyrene, polyaryl ether keton, polyvinylene flouride, polyoxy methylene, polyurethane or copolymers or mixtures thereof.
The nano non-woven tissue which is the decisive component for a high degree of precipitation of finest dust is preferably produced in that a thermoplastic polymer is spun in the molten state or a polymer dissolved in a suitable solvent is spun from nozzles in a strongly electrical field to form the finest fibers and on a substrate which is guided past a counter electrode it is deposited in the form of a planar structure. This process is known as the electro spinning process. The diameter of the fibers can be controlled by the process parameters, namely the viscosity of the melt in the case of thermoplasts and/or the concentration and viscosity of the polymer solution. The basis weights of the nano non-woven tissue are determined on the one hand by the mass flow through the nozzles and on the other by the speed at which the substrate is moved under the nozzles. The air permeability of the nano non-woven tissue is influenced by the thickness of the fibers and by their packing density.
The production of nano fibers from various pol
Emig Dietmar
Klimmek Albrecht
Raabe Ernst
FiberMark Gessner GmbH & Co.
Pham Minh-Chau T.
Scully Scott Murphy & Presser
Simmons David A.
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