Gas separation – Two or more separators – Plies or layers of different characteristics or orientation
Reexamination Certificate
2001-10-16
2004-03-16
Pham, Ming-Chau T. (Department: 1724)
Gas separation
Two or more separators
Plies or layers of different characteristics or orientation
C055S382000, C055S487000, C055SDIG002, C055SDIG005, C055SDIG001, C095S057000, C095S287000, C095S078000, C096S015000, C096S069000, C015S347000, C015S352000
Reexamination Certificate
active
06706086
ABSTRACT:
BACKGROUND DESCRIPTION Field of the invention
The invention relates to a dust filter bag including a highly porous backing material ply and to a method of producing the dust filter bag.
There has been a significant increase in recent years in the demands on the filtration capacity of dust filter bags as employed in modern vacuum cleaners. In this respect it is especially in the field of fine-particle arrestance that is gaining ever-increasing significance, achievable by the use of e.g. meltblown fibrillated fiber or nanofiber non-woven filtration layers. These filtration layers are combined with backing materials and then processed into dust filter bags.
Backing material for high-efficiency filtration layers comprises, as a rule, paper since this offers the advantage of being very good to process on conventional dust filter bag makers. Corresponding paper backings are disclosed in WO 97/30772 and in EP 0 960 645. In making use of currently conventional bonding and folding techniques, paper backing materials feature, more particularly, the advantage of high productivity in bag production. Furthermore, paper backings can be made sufficiently rugged for use in vacuum cleaners.
One major drawback in using papers as the backing is the restricted air permeability, resulting in a low system suction/blow capacity. Making a paper backing with higher air permeability reduces the strength of the material: i.e. significantly increasing the pulp percentages as suitable for achieving high values of air permeability in paper-making would be at the expense of the strengthening components. The strength of the paper would no longer be sufficient to withstand the mechanical stresses on the bag in the vacuum cleaner during operation, ending in the bag bursting. Boosting the percentage of strengthening raw material components by increasing the total basis weight is likewise no solution since increasing the total basis weight in turn reduces the air permeability of the paper.
To get round the disadvantage of high filtration resistance and the undesirable tendency of the material becoming blocked, spunbond nonwovens have been employed as the backing materials for high efficiency filtration layers. Thus, there is described e.g. in WO 97/30772 a vacuum cleaner bag which comprises a spunbond nonwoven as the outer ply of the bag. The particular advantage in this arrangement as described is the low blockage tendency of the bag since the composite of the backing material and filtration layer has a high air permeability.
However, the big disadvantage is the textile-like structure of spunbond nonwovens which, although having the desired properties as to high air permeability whilst featuring sufficient strength in use as a backing in vacuum cleaner bags, fail to permit processing on conventional vacuum cleaner bag makers in employing conventional technologies. This is due to these materials not permitting folding as needed for this processing, on the one hand, and on top of this the water-based size and adhesive types available for this production process being unsuitable due to the polymer raw material structure of spunbond nonwovens. On the other, printing the outer ply of the bag, a mandatory requirement in this branch, is not possible with known grades of spunbond nonwovens. In addition to this, for processing such materials a stamping process needs to be used in which the individual bags are stamped out by a hot stamp with simultaneous sealing of the seams. This process is unsatisfactory because of its low productivity.
It is against this background that the invention is based on the objective of providing a dust filter bag which whilst permitting high system suction/blower capacity, is sufficiently rugged for use in vacuum cleaners and which is simple and cost-effective to manufacture; the invention likewise providing a corresponding method of production.
This objective is achieved in accordance with the invention by a dust filter bag comprising at least one filter material ply and at least one backing material ply, the backing material ply featuring an air permeability of at least 900 l/m
2
×s, a burst strength of at least 70 kPa, a rupture strength longitudinally better than 10 N and transversely better than 3 N, a flexural rigidity longitudinally better than 0.5 cN cm
2
and transversely better than 0.25 cN cm
2
, a basis weight of 30-80 g/m
2
and a droplet sink-in time of less than 10 min.
The air permeability of the backing material ply employed in accordance with the invention amounts to at least 900 l/m
2
×s, preferably 900 l/m
2
×s to 8000 l/m
2
×s, particularly preferred being an air permeability in the range of 1500-3500 l/m
2
×s, all as measured in accordance with EN ISO 9237. An air permeability of at least 900 l/m
2
×s permits a sufficiently high system suction/blower capacity.
The backing material ply as used in accordance with the invention has a burst strength of at least 70 kPa, preferably 70 kPa to 350 kPa, particularly preferred being a burst strength in the range of 120 to 210 kpa, all measured in accordance with DIN 53141 but using a test surface area of 10 cm
2
instead of 7.8 cm
2
in deviating from this DIN standard. It has been discovered that when the burst strength of the backing material ply is at least 70 kPa the dust filter bag in accordance with the invention is sufficiently rugged to prevent the bag from bursting when used in the vacuum cleaner.
The rupture strength of the backing material ply in the dust filter bag in accordance with the invention is at least 10 N longitudinally, preferably 10 N to 60 N, particularly preferred being a rupture strength longitudinally in the range of 20 to 40 N, as measured in accordance with EN ISO 1924-2 (N/15 mm strip width).
The rupture strength of the backing material ply in the dust filter bag in accordance with the invention is at least 3 N transversely, preferably 3 N to 50 N, particularly preferred being a rupture strength transversely in the range of 10 to 30 N, as measured in accordance with EN ISO 1924-2 (N/15 mm strip width).
The flexural rigidity of the backing material ply in the dust filter bag in accordance with the invention is better than 0.5 cN cm
2
longitudinally, preferably better than 1.0 cN cm
2
, the flexural rigidity being better than 0.25 cN cm
2
transversely, preferably better than 0.75 cN cm
2
, all measured in accordance with DIN 53864 with a specimen width of 15 mm (a specimen width of 20 mm being used in accordance with DIN 53864).
It has been discovered in accordance with the invention that a backing material ply, comprising a corresponding rupture strength and a corresponding flexural rigidity as indicated above, permits processing on a conventional bag maker as used in the production of dust filter bags including paper backing materials. Being able to use a conventional bag maker now permits simple and cost-effective production of the dust filter bag in accordance with the invention.
In addition, it has been discovered that for assuring adequate adhesiveness with water-based adhesives as used generally in dust filter bag production, it is important that the backing material ply in accordance with the invention needs to feature a droplet sink-in time of less than 10 min, preferably less than 5 min, particularly preferably less than 1 minute. The droplet sink-in time is measured as follows: a droplet of ink (formulated of 50 ml Pelikan ink 4001 and 950 ml distilled water) is applied to the surface of the specimen with a burette from a height of 1 cm. The droplet sink-in time corresponds to the time between the first contact of the droplet with the surface and the point in time at which no bright spots are discernible on the surface, i.e. until the droplet has fully sunk into the material. As long as the droplet has not sunk into the specimen, the bright spot is still discernible. Once the droplet has totally diffused into the material, no liquid is visible on the surface and the bright spot has disappeared.
The basis weight of the backing material in accordance with
Emig Dietmar
Klimmek Albrecht
Raabe Ernst
FiberMark Gressner GmbH & Co. KG
Pham Ming-Chau T.
Scully Scott Murphy & Presser
LandOfFree
Dust filter bag including a highly porous backing material ply does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Dust filter bag including a highly porous backing material ply, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Dust filter bag including a highly porous backing material ply will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3265342