DE29924500U1 - Disposable filter bag for vacuum cleaners - Google Patents

Abstract

A coarse filter layer comprises at least one of a wet-laid high capacity paper, dry-laid high capacity paper, high bulk melt blown non woven, a spun blown (modular) non woven, a micro denier spun-bond non woven positioned upstream in the direction of air flow of a filtration grade melt blown fleece. The basis weight and air permeability of filtration grade melt blown fleece layer, wet-laid high dust capacity layer, dry-laid high dust capacity paper and high bulk melt blown non woven are 10-50 g/m 2> and 100-1500 L/(m 2>s), 30-150 g/m 2> and 500-8000 L/(m 2>s), 30-150 g/m 2> and 500-8000 L/(m 2>s) and 30-180 g/m 2> and 300-8000 L/m 2>s respectively. The downstream of the filtration grade melt blown fleece layer has an outer layer comprising at least one of a spun-bond, wet-laid, dry-laid or hydroentangled non woven or netting with basis weight of about 6-80 g/m 2> and air permeability of about 500-10000 L/m 2>s and an odor absorbing composite comprising an activated carbon fiber layer having a basis weight of about 25-500 g/m 2> and air permeability of about 500-3000 L/m 2>s. Upstream of a backing layer of fleece has a basis weight of 15-100 g/m 2> and air permeability of 2000-5000 L/m 2>s. To the upstream of the coarse filter layer is the support layer which is one of a netting scrim bonded to the coarse filter layer, a wet-laid tissue fleece, spun bond non woven. The coarse filter layer material has suitable dielectric properties and is electrostatically charged. One layer is bonded to its adjacent layer with a porous hot melt adhesive. The dry-laid high capacity paper comprises bicomponent fibers with a sheath of polyethylene and a core of polypropylene having a melting point higher than the sheath. The core is disposed eccentric relative to the sheath. Alternatively, a multipurpose filtration capacity layer positioned upstream in the direction of air flow of another filtration layer which is selected from among a wet-laid or a dry-laid filter having a base weight of about 30- 100 g/m 2> and air permeability of about 100-3000 L/m 2>s and thermally bonded non woven having a basis weight of about 10-100 g/m 2> and air permeability of about 100-3000 L/m 2>s. The multipurpose filtration capacity layer is selected from among a wet-laid or a dry-laid high dust capacity paper, high bulk melt blown non woven, spun blown modular paper and micro denier spun bond non woven with basis weight and air permeability of 30-150 g/m 2> and 500-8000 L/m 2> s, 30-180 g/m 2> and 300-1500 L/m 2> s, 20-150 g/m 2> and 200-3000 L/m 2> s and 20-150 g/m 2> and 500-10000 L/m 2>s respectively. The multipurpose filtration layer is operative to provide to the composite structure a pressure drop of at most 30 m bar at fine dust particle loading of at least 6.5 g. The wet-laid high dust capacity paper consists of fibers with at least 15% chargeable or unchargeable synthetic fibers and complementary amount of wood pulp fibers and binder. The synthetic fibers are polyester or electrostatically charged polypropylene. The dry-laid high dust capacity paper of multilayer filtration layer is selected from among latex bonded fluff pulp fibers, thermally bondable-fusing fibers which are bicomponent polymer fibers, thermally bonded blend of thermally bondable fusing polymer fibers and fluff pulp fibers, thermally bonded blend of thermally bondable fusing fibers, fluff pulp fibers and electrostatically charged split film fibers, thermally bonded blend of mixed electrostatic fibers. Electrostatically charged melt blown fleece layer having basis weight of about 10- 50 g/m 2> and air permeability of 100-1500 L/m 2> s is positioned between the multipurpose filtration layer and the other filtration layer. An independent claim is also included for the method of filtering a gas.

Description

GRÜNECKER KINKELDEY ·3&Tgr;&thgr;£&kgr;&Mgr;*&Agr;^ S SChU/VAfcJHAUSSER

LAWYER ETAT

GKS & S MAXIMIUANSTRASSE 58 D-80538 MUNICH GERMANY

LAWYERS

MUNICH

DR. HELMUT EICHMANN

GERHARD 8ARTH

DR. ULRICH BLUMENRÖDER, LLM.

CHRISTA NIKLAS-FALTER

DR. MAXIMILIAN KINKELDEY, LLM.

DR. KARSTEN BRANDT

MICHAEL J. FRANKE, LLM.

UTE STEPHANI

DR. BERND ALLEKOTTE, LL.M.

DR. ELVIRA PFRANG, LL M.

KARIN LOCHNER

BABETT ERTLE

CHRISTINE NEUHIERL

SABINE PRÜCKNER PATENT ATTORNEYS EUROPEAN PATENT ATTORNEYS MUNICH

DR. HERMANN KINKELDEY PETER H. JAKOB WOLFHARD MEISTER HANS HILGERS DR. HENNING MEYER-PLATH ANNEUE EHNOLD THOMAS SCHUSTER DR. KLARA GOLDBACH MARTIN AUFENANGER GOTTFRIED KUTZSCH DR. HEIKE VOGELSANG-WENKE REINHARD KNAUER DIETMAR KUHL DR. FRANZ-JOSEF ZIMMER BETTINA K. REICHELT DR. ANTON K. PFAU DR. UDO WEIGELT RAINER BERTRAM JENS KOCH, M.S. (U of PA) M.S.

BERND ROTHAEMEL DR. DANIELA KINKELDEY THOMAS W. LAUBENTHAL DR. ANDREAS KAYSER DR. JENS HAMMER DR. THOMAS EICKELKAMP JOCHEN KILCHERT DR. THOMAS FRIEDE

YOUR REF.

OUR REF.

G5006-06533/DM

PATENT ATTORNEYS

EUROPEAN PATENT ATTORNEYS

BERLIN

PROF. DR. MANFRED BÖNING

DR. PATRICK ERK, M.S. (MIT)

COLOGNE

DR. MARTIN DROPMANN

CHEMNITZ

MANFRED SCHNEIDER

OF COUNSEL PATENT ATTORNEYS

AUGUST GRÜNECKER DR. GUNTER BEZOLD DR. WALTER LANGHOFF

DR. WILFRIED STOCKMAIR (-1996)

DATE

14.04.2003

Documents required for registration Utility model branch from EP 02 018 932.0 of 23 August 2002 Applicant: AIRFLO EUROPE N.V.

GASTON EYSKENSLAAN 2 NOLIMPARK 1503 OVERPELT BELGIUM

Vacuum cleaner bags and improved vacuum cleaner bags

GRÜNEECKER KINKELDEY
STOCKMAIR & SCHWANHÄUSSER
MAXIMIUANSTR. 58
D-80538 MUNICH
GERMANY

.•FAX'flGRTS}+43*89* 22*02 87: :

••*FAX*(GR4)*· + 4^*39 21*86 92% ' http://www.grunecker.de
e-mail: postmaster@grunecker.de

0EUT5CHE BANK MUNICH ijjo. 1J 51734 *BLZ 70(3 700 SWIFT: DEUT DE MM

VERSION TO BE ENTERED VACUUM BAGS AND IMPROVED VACUUM BAGS FIELD OF INVENTION

This invention relates to a new disposable vacuum cleaner bag composition which is considerably superior to existing vacuum cleaner bag designs in terms of dust holding capacity, minimal increase in pressure drop upon dust loading and ease of bag manufacture and dimensional stability, while achieving filtration efficiency values which compare highly favourably with the best commercially available bags.

BACKGROUND OF THE INVENTION

In recent years, a number of companies have developed raw materials and components for vacuum cleaner bags to replace the older single-layer paper bags and the familiar double-layer bags with bags having a downstream filter paper and an upstream tissue paper having upstream layers of either wet-laid tissues or nonwovens such as ultrafine meltblown (MB) nonwovens, occasionally referred to herein as "filtration grade MB nonwovens." Some vacuum cleaner manufacturers have even marketed bagless vacuum cleaners to avoid the cost of bags. However, this type of vacuum cleaner has lower suction power and the compartment that holds the dust must be emptied by hand, and this largely offsets its advantages by exposing the worker and the environment to the concentrated dust. Nevertheless, the bagless vacuum cleaner has prompted manufacturers to improve the overall effectiveness of bags. In addition, the invention relates to fibrous components that are randomly laid down in three dimensions using dry-laying and wet-laying techniques to achieve low density and high volume for new

To provide filters with greater air permeability and particle holding or storage capacity.

The prior art has addressed the problem of providing a vacuum cleaner bag with improved filtration performance or filtration efficiency. US Patent No. 5,080,702, Home Care Industries, Inc., discloses a container-type disposable filter bag comprising a structure of layers arranged side by side, namely an inner and an outer layer of an air-permeable material. US Patent No. 5,647,881 (EPO 0 822 775 B1) discloses a three-layer composition of an outer carrier layer, a middle charged fiber filter layer with certain properties and an inner diffusion layer which is only connected to the fiber filter layer at at least one seam. The purpose of the diffusion layer is mainly to provide the filter bag with shock load resistance or strength. EPO 0 338 479 (Gessner) discloses a dust filter bag with a fibrillated fleece-covered outer layer of filter paper. The fibrillated filtration grade nonwoven layer is arranged upstream of the filter paper.

In the vacuum cleaner bag of the invention, the main function of the inner layer is a high dust storage capacity or a high dust holding capacity, a property that has not yet been disclosed on this scale in the prior art.

With the advent of electrostatically charged MB fleeces, it has become possible to produce bag laminates with filtration efficiencies of the order of 99.8 - 99.9% for fine dust at medium airflow. However, conventional MB fleeces are essentially flat filters. Consequently, filter structures using MB fleeces quickly become charged with dust, reducing air suction and losing further dust holding capacity in the vacuum cleaner. Today, standard vacuum cleaner bags have an air permeability of 200 to 400 l/(m ² s). It is desirable to have a combination of paper types and other layers, including MB layers, that give high efficiency of up to 99.9% and also allow high flow with minimal increase in pressure gradient as measured by the DIN 44956-2 test.

A first object of this invention is to provide a new vacuum cleaner bag composition having extremely high filtration performance with respect to fine dust and maximum performance of a vacuum cleaner in terms of continuous high suction for picking up dust without significant increase in pressure drop until the bag is full.

A second object of this invention is to provide a bag having a composition such that it has the stiffness necessary for manufacture and molding on conventional vacuum cleaner bag manufacturing equipment.

A third object of this invention is to provide a vacuum cleaner bag media that is best suited to the new European trend towards small vacuum cleaners, of course with smaller vacuum cleaner bags, due to its excellent filtration performance and superior, non-blocking, high airflow performance.

These and other objects of the inventor will also be apparent to those skilled in the art from the following disclosure.

The "Nonwoven Fabrics Handbook of the Association of the Nonwoven Fabrics Industry", 1992 is incorporated herein by reference in its entirety.

SUMMARY OF THE INVENTION

The above-described objects are achieved by the filter according to claim 1. In particular, a disposable vacuum cleaner bag or throw-away vacuum cleaner bag with an air permeability greater than 400 l/(m ² s) was developed. This was achieved in particular by placing a filter paper on the upstream air side of a filtration grade MB fleece/

spunbond two-ply component, rather than placing the filter paper on the outside (ie, downstream air side) of the bag as is typically done. It should be noted, however, that prior art bag designs often place a lightweight (typically 13 g/m ² ) tissue web upstream of the MB web to support and protect the MB web from abrasion. However, this lightweight tissue web filters only some of the largest dust particles.

With the new filter bag construction, it is possible to use a coarse filter paper, sometimes referred to herein as a "high dust holding capacity" paper or layer, a "multipurpose" or "capacity" paper or layer, at the most upstream layer within the bag. This invention also allows for optional use of lightweight tissue batt, netting or other scrim at the innermost layer upstream of this filter paper. This removes large dust particles through the coarse filter paper (and possibly to a lesser extent through the lightweight tissue batt, if used). The filtration grade MB portion of the bag fabric can serve more efficiently as a filter without clogging since it does not have to hold the bulk of the dust. If desired, a wet laid tissue can also be used in front of the coarse paper. This construction is different from previous designs which used MB layers on the inside of the bag and which relied on the MB batt for both dust holding and filtration. In addition, the paper gives the bag the rigidity needed to manufacture and form the new bag composition from conventional vacuum cleaner bag manufacturing equipment.

The new vacuum cleaner bag thus comprises a flat composition of a coarse filter layer comprising at least (a) a wet-laid paper with high dust holding capacity, (b) a dry-laid paper with high dust holding capacity, (c) a high bulk meltblown nonwoven, or (d) a (modular) spunblown nonwoven, arranged upstream of the direction of air flow of a filtration grade meltblown nonwoven layer formed as a bag with at least one means for defining an air inlet in the flat composition and at least one seam forming the flat composition as a bag. The filter layer effective according to this invention arranged downstream of the coarse capacity layer is sometimes referred to herein as a "secondary" or "high performance filtration" layer.

According to a further development of this invention, there is now also provided a composite structure for a vacuum cleaner bag with improved efficiency, comprising a multi-purpose filtration layer, referred to herein as a "high dust holding capacity" paper or layer, referred to as a "high dust holding capacity" paper or layer.

·

which is arranged upstream in the direction of the air flow of a second filtration layer selected from (a) a wet-laid filter paper having a basis weight of about 30 to 100 g/m ² and an air permeability of about 100 - 3000 l/(m ² s) and (b) a thermally bonded spunbond nonwoven having a basis weight of about 10-100 g/m ² and an air permeability of about 500 - 10000 l/(m ² s) and preferably about 2000 - 6000 l/(m ² s).

A preferred example is a thermally bonded dry laid paper with high dust capacity comprising a mixture of fluff pulp, bicomponent fibers (for thermal bonding) and electrostatically charged split film fibers. Basically, in one aspect, the new composite vacuum cleaner bag structure with improved efficiency comprises placing a wet or dry laid capacity paper with an air permeability of up to 8000 l/(m ² s) in front of a wet laid filter paper with an air permeability of up to about 3000 l/(m ² s).

According to another preferred aspect, the invention provides the optional inclusion of a meltblown nonwoven intermediate layer having a basis weight of about 50 g/m ² and an air permeability of about 100 - 1500 l/(m ² s) and disposed between the multipurpose filtration layer and the second filtration layer. In a variant, the optional meltblown nonwoven intermediate layer may be electrostatically charged.

A scrim of typically about 13 ^gsm basis weight may be disposed on one or both sides of the multipurpose filtration layer and second filtration layer pair for improved abrasion resistance and ease of bag manufacture. Preferably, the scrim is disposed as the outermost upstream layer of the structure. Also, some or all of the layers in the new improved performance bag constructions may be bonded together using hot melt adhesives, adhesives, or thermal or ultrasonic bonding, or a combination of these bonding techniques.

A vacuum cleaner bag using the composite structure with improved efficiency of this invention has been found to have favorable filtration performance compared to other vacuum cleaner bag structures.

• · · ♦

Improved efficiency bags generally perform better than 95% performance according to the DIN 44956-2 test and can typically endure two or three times more DIN dust loading cycles than comparable bag designs. They also have up to five times more DIN loading cycles than conventional bag designs characterized by either a scrim in front of standard wet-laid paper or by an MB filter fleece in front of a standard wet-laid paper. With the optional electrostatically charged MB interlayer, the new designs have superior, high fine dust filtration performance for 0.1 - 0.3 pm NaCl particles.

High filtration grade nonwovens such as electrostatically charged MB, modular spunbond and microdenier spunbond media can also be incorporated into the new designs of this invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic cross-section of a conventional vacuum cleaner bag construction consisting of wet-laid tissue (inside the bag) and filter paper (air outlet side).

Fig. 2 is a schematic cross-section of a two-layer vacuum cleaner bag in which an ultrafine MB nonwoven fabric within the bag serves as both a dust storage and filter component.

Fig. 3 is a schematic cross-section of a three-layer vacuum cleaner bag in which a wet-laid tissue fleece with very low dust holding capacity has been added to protect the MB fleece from abrasion.

Figure 4 is a schematic cross-section of a three-layer vacuum cleaner bag construction according to this invention in which a special bulk MB is disposed in front of a filtration grade MB fleece and the spunbond layer is disposed on the outside of the bag.

Figure 5 is a schematic cross-section of a three-layer vacuum cleaner bag construction according to this invention in which wet-laid capacity paper is disposed in front of a filtration grade MB nonwoven. The outer layer may be a spunbond, wet-laid, dry-laid, hydroentangled nonwoven, netting, or any type of nonwoven or woven scrim.

Fig. 6 is a schematic cross-section of a three-layer vacuum cleaner bag construction according to this invention in which dry-laid capacity paper is disposed in front of a meltblown nonwoven. The outer layer may be a spunbond, wet-laid, dry-laid, hydroentangled or other nonwoven scrim.

Fig. 7 is a schematic cross-section of a new vacuum cleaner bag according to

Example 7, in which a nonwoven/carbon layer is arranged as an odor absorbing layer with substantially the same filtration properties as a filter combination which serves only for dust filtering.

Fig. 8A is a schematic cross-sectional view of an embodiment of the vacuum cleaner bag construction according to this invention.

Fig. 8B is another schematic cross-sectional view of an embodiment of the vacuum cleaner bag construction according to this invention.

Fig. 8C is another schematic cross-sectional view of an embodiment of the vacuum cleaner bag construction according to this invention.

Fig. 8D is another schematic cross-sectional view of an embodiment of the vacuum cleaner bag construction according to this invention.

Fig. 8E is another schematic cross-sectional view of an embodiment of the vacuum cleaner bag construction according to this invention.

Fig. 8F is another schematic cross-sectional view of an embodiment of the vacuum cleaner bag construction according to this invention.

Fig. 8G is another schematic cross-sectional view of an embodiment of the vacuum cleaner bag construction according to this invention.

Fig. 8H is another schematic cross-sectional view of an embodiment of the vacuum cleaner bag construction according to this invention.

Fig. 81 is another schematic cross-sectional view of an embodiment of the vacuum cleaner bag construction according to this invention.

Fig. 8J is another schematic cross-sectional view of an embodiment of the vacuum cleaner bag construction according to this invention.

Fig. 8K is another schematic cross-sectional view of an embodiment of the vacuum cleaner bag construction according to this invention.

Fig. 8L is another schematic cross-sectional view of an embodiment of the vacuum cleaner bag construction according to this invention.

Fig. 8M is another schematic cross-sectional view of an embodiment of the vacuum cleaner bag construction according to this invention.

Fig. 8N is another schematic cross-sectional view of an embodiment of the vacuum cleaner bag construction according to this invention.

Fig. 80 is another schematic cross-sectional view of an embodiment of the vacuum cleaner bag construction according to this invention.

Fig. 8P is another schematic cross-sectional view of an embodiment of the vacuum cleaner bag construction according to this invention.

Fig. 8Q is another schematic cross-sectional view of an embodiment of the vacuum cleaner bag construction according to this invention.

Fig. 8R is another schematic cross-sectional view of an embodiment of the vacuum cleaner bag construction according to this invention.

Fig. 8S is another schematic cross-sectional view of an embodiment of the vacuum cleaner bag construction according to this invention.

Fig. 8T is another schematic cross-sectional view of an embodiment of the vacuum cleaner bag construction according to this invention.

Fig. 8U is another schematic cross-sectional view of an embodiment of the vacuum cleaner bag construction according to this invention.

Fig. 8V is another schematic cross-sectional view of an embodiment of the vacuum cleaner bag construction according to this invention.

Fig. 8W is another schematic cross-sectional view of an embodiment of the vacuum cleaner bag construction according to this invention.

Fig. 8X is another schematic cross-sectional view of an embodiment of the vacuum cleaner bag construction according to this invention.

Fig. 8Y is another schematic cross-sectional view of an embodiment of the vacuum cleaner bag construction according to this invention.

Fig. 8Z is another schematic cross-sectional view of an embodiment of the vacuum cleaner bag construction according to this invention.

Fig. 8AA is another schematic cross-sectional view of an embodiment of the vacuum cleaner bag construction according to this invention.

Fig. 9 is a graphical representation of the pressure drop (mbar) for vacuum cleaner bags as a function of the fine dust loading (PTI/fine) according to DIN 44956-2, carried out for examples 1 to 3 and 5 to 7.

Fig. 10 is a graphical representation of the pressure drop (mbar) for vacuum cleaner bags as a function of the fine dust loading according to DIN 44956-2, performed for Example 4, Airflow and Example 2, 3M.

Fig. 11 is a graph showing a comparison of airflow as a function of particulate matter loading (PTI/fine).

Fig. 12 is a schematic cross-section of a conventional vacuum cleaner bag construction.

Fig. 13 is a schematic cross-section of another vacuum cleaner bag design.

Figure 14 is a schematic cross-section of an embodiment of an improved efficiency bag structure with a meltblown interlayer according to this invention.

Figure 15 is a schematic cross-section of another embodiment of an improved efficiency bag structure having a latex bonded, dry laid, multi-purpose layer of high dust capacity fluff pulp upstream of a second wet laid paper filtration layer according to this invention.

Figure 16 is a schematic cross-section of another embodiment of an improved efficiency bag structure having a thermally bonded, dry-laid, multi-purpose, high dust capacity layer upstream of a second wet-laid paper filtration layer according to this invention.

· · I

· 1

11

Fig. 17 is a graphical representation of the pressure drop for selected vacuum cleaner bag structures as a function of particulate matter loading.

characters

18A-18P are schematic cross-sectional views of selected embodiments of bag structures having improved efficiencies of this invention in which a wet-laid paper layer is the most downstream layer.

characters

19Q-19AF are schematic cross-sectional views of selected embodiments of the improved efficiencies bag structures of this invention in which a spunbond nonwoven layer is the most downstream layer.

characters

20AG-20BL are schematic cross-sectional views of selected embodiments of the improved efficiencies bag structures of this invention in which adjacent layers are bonded by a hot melt adhesive.

DETAILED DESCRIPTION

The filter structures of this invention are intended for vacuum cleaner bags and for vacuum filters in general. By "vacuum filter" is meant a filter structure intended to be operated so that a gas, preferably air, usually carrying dry, solid particles, flows through the structure. In this application, the convention has been adopted that the filter inlet side is referred to as "upstream" and the filter discharge side as "downstream". Occasionally, the terms "before" and "after" are used herein to refer to the relative positions of structural layers as upstream and downstream. Of course, there is a pressure gradient across the filter during filtration, sometimes referred to as "pressure drop". Vacuum cleaner

>♦ *

12

typically use bag-style filters. Typically, the upstream side of a vacuum cleaner bag is the inside and the downstream side is the outside.

PIN44956-2:

DIN 44956-2 was applied to determine the increase in pressure drop of five different examples of vacuum cleaner bag designs after dust loading with fine dust at the following levels: O ₁ 0.5,1.0,1.5, 2.0 and 2.5 grams.

Air permeability after fine dust loading test:

The dust loading part of DIN 44956-2 was carried out with 0.5 gram increments from 0 to 2.5 g/m ² /s for 7 bags of each sample. However, the pressure drop values were not recorded again. The maximum sustained air permeability values were then determined for the bags that met the determined dust loading levels.

had.

Materials referred to in this patent application are described in more detail below:

Standard vacuum cleaner filter bag paper

This type of paper has traditionally been used as a single ply where it provides dust filtration and containment as well as the strength and abrasion resistance required for a vacuum cleaner bag. This paper is also strong enough to allow easy manufacture on standard bag making equipment. This paper is composed predominantly of unbleached wood pulp with 6-7% of a synthetic fibre such as polyethylene terephthalate (PET) type polyester and is manufactured by wet-laid processes. The standard paper typically has a basis weight of about 30-80 g/m ² and often about 50 g/m ² . The PET fibres typically have a fineness of 1.7 dtex and lengths of 6-10 mm. This paper has an air permeability in the range of about 200-500 l/(m ² s) and an average pore size of about 30 μm. However, the performance, determined according to the DIN 44956-2 test, is only about 86%. Another disadvantage is that the pores quickly become clogged with dust, and the dust storage capacity is further limited by the very thin paper thickness of only about 0.20 mm.

Spunbond nonwoven

A nonwoven made of spunbond polymer fibers can be used as a second filtration layer downstream of the coarse layer. The fibers can be made of any spunbondable polymer, such as polyamides, polyesters or polyolefins. The basis weight of the spunbond nonwoven should be about 10-100 g/m ² and preferably about 30 - 40 g/m ² . The spunbond nonwoven should have an air permeability of about 500 - 10000 l/(m ² s) and preferably about 2000 - 6000 l/(m ² s), measured according to DIN 53887. The spunbond can also be electrostatically charged.

Scrim or carrier fleece

Scrim generally refers to very open, porous paper or nonwoven with a light basis weight. The basis weight of the scrim is typically about 10-30 g/m ² and often about 13-17 g/m ² . The scrim, sometimes called a support fleece, usually has an air permeability of 500 - 10000 l/(m ² s). It is used primarily to protect the multi-purpose layer with high dust capacity from abrasion. The scrim can filter the largest particles. The scrim, like any other layer of the bag, can be electrostatically charged, provided that the material has suitable dielectric properties.

Wet-laid paper with high dust capacity

High dust capacity wet laid paper, often referred to herein as "wet laid capacity paper", is bulkier, thicker and more permeable than standard vacuum cleaner bag filter paper. In its role as a pre-filter in the vacuum cleaner bag assembly, it performs several functions, namely, resisting impact loading, filtering large dirt particles, filtering a significant proportion of small dust particles, storing or retaining large quantities of particles while preventing air from easily passing through, thereby providing a low pressure drop at high particle loading, which increases the life of the vacuum cleaner bag.

The wet-laid capacity paper usually comprises a fiber mixture of fibers from wood pulp and synthetic fibers. It typically comprises up to about 70% wood pulp and correspondingly more synthetic fiber, such as PET, than the standard paper described above. It has a greater thickness than the standard paper of about 0.32 mm with a typical basis weight of 50 g/m ² . The pore size is much larger, the average pore size can be larger than 160 μm . This allows the paper to hold much more dust in its pores before it becomes clogged. The basis weight of the wet-laid capacity paper is typically about 30-150 g/m ² and preferably about 50 - 80 g/m ² .

The wet-laid capacity paper has a fine dust particle filtration performance of about 66 - 67%, determined according to DIN 44956-2. It is essential that the wet-laid capacity paper has an air permeability that is higher than that of the standard filter paper. The lower limit of the permeability should therefore preferably be at least about 500 l/(m ² s), more preferably at least about 1000 l/(m ² s) and most preferably at least about 2000 l/(m ² s). The upper limit of the permeability is defined to ensure that the paper filters and retains a majority of the dust particles larger than about 10 μm . Accordingly, the secondary high-performance filter medium arranged downstream can filter out and capture fine particles for a much longer period before a significant increase in pressure drop across or through the filter occurs. Accordingly, the air permeability of the wet-laid capacity paper should preferably be at most about 8000 l/(m ² s), more preferably at most about 5000 l/(m ² s), and most preferably at most about 4000 l/(m ² s). Thus, the wet-laid capacity paper is exceptionally well designed as a multipurpose filtration layer to be placed upstream of the secondary high performance filtration layer.

Dry laid paper with high dust capacity

Prior to this invention, dry-laid paper with high dust capacity, sometimes referred to here as "dry-laid capacity paper", was not used as a filter in vacuum cleaner bags. Dry-laid paper is not formed from a water suspension or slurry, but is produced using an air-laying technique and preferably using a fluff pulp process. Hydrogen bonds, which play a major role in the mutual attraction of molecular chains, are not formed in the absence of water. Thus, for the same basis weight, dry-laid capacity paper is usually much thicker than standard paper and wet-laid capacity paper. For a typical weight of 70 g/m ^2, the thickness is 0.90 mm, for example.

The dry laid capacity paper tissues can be bonded primarily by two methods. The first method is latex bonding, in which the latex binder is applied from water-based dispersions. Impregnation techniques such as spraying or dipping and squeezing (padder roll application), in both cases followed by a drying and heat curing process, can be used. The latex binder can also be applied in discrete patterns such as dots, diamonds, crosshatches or wavy lines by means of gravure rollers, followed by drying and curing.

The second method is thermal bonding, e.g., by using binder fibers. Binder fibers, sometimes referred to herein as "thermally bondable fusible fibers," are defined in the Nonwoven Fabric Handbook (1992 edition) as "fibers having a lower softening point than other fibers in the web. Under the application of heat and pressure, they act as a binder." These thermally bondable fusible fibers generally melt completely at locations where sufficient heat and pressure are applied to the web, causing the matrix fibers to adhere to one another at their crossover points. Examples include co-polyester polymers, which adhere to a wide range of fibrous materials when heated.

In a preferred embodiment, thermal bonding can be achieved by adding at least 20%, preferably up to 50%, of a bicomponent ("B/C")

polymer fiber to the dry-laid web. Examples of B/C fibers include fibers having a core of polypropylene ("PP") and a sheath of a more heat-sensitive polyethylene ("PE"). The term "heat-sensitive" means that the thermoplastic fibers become soft and sticky at a temperature 3 - 5°C below the melting point. The sheath polymer should preferably have a melting point in the range of about 90 - 160 ⁰ C, and the core polymer should have a higher melting point, preferably at least about 5°C higher than that of the sheath polymer. For example, PE melts at 121 ⁰ C and PP melts at 161 - 163°C. This helps in bonding the dry laid web when it is passed between the nip of a thermal calender or in a through-air oven where thermally bonded fibers are obtained with less heat and pressure to produce a less compact, more open and more breathable structure. In a further preferred embodiment, the core of the core/sheath of the B/C fiber is arranged eccentrically with respect to the sheath. The closer the core is arranged to one side of the fiber, the more likely the B/C fiber will curl during the thermal bonding step, thereby increasing the volume of the dry laid capacity paper. This will of course increase its dust holding capacity. Therefore, in a further preferred embodiment, the core and sheath are arranged side by side in the B/C fiber and the bonding is achieved by means of a through-air oven. A thermal calender that would compress the web more than in Through-flow bonding is less preferred in this case. Other polymer combinations that can be used in core/sheath or side-by-side B/C fibers include PP with low melting co-polyester polymers and polyester with nylon 6. The dry-laid high-capacity layer can also be formed substantially entirely of bicomponent fibers.

In general, the mean pore size of dry laid capacity paper is between the pore size of standard paper and wet laid capacity paper. The filtration efficiency as determined by the DIN 44956-2 test is about 80%. Dry laid capacity paper should have about the same basis weight and permeability as the wet laid capacity paper described above, i.e. in a range of about 500 - 8000 l/(m ² s), preferably about 1000 - 5000 l/(m ² s) and most preferably about 2000 - 4000 l/(m ² s). It has an excellent

dust storage capacity and has the advantage that it is much more uniform in weight and thickness than wet-laid papers.

Several preferred embodiments of dry-laid capacity paper are contemplated. One is a latex-bonded fluff pulp fiber composition. That is, the fibers comprising the paper consist essentially of fluff pulp. The term "fluff pulp" means a nonwoven component of the vacuum cleaner bag of this invention which is made by mechanically shredding pulp rolls, i.e., fibrous material made from wood, and then aerodynamically transporting the pulp to tissue forming components of air-laying or dry forming machines. A Wiley mill can be used to shred the pulp. So-called Dan-Web or M and J machines are useful for dry forming. A fluff pulp component and the dry-laid layers of fluff pulp are isotropic and are thus characterized by disordered fiber orientations in the directions of all three orthogonal dimensions. That is, they have a large proportion of fibers oriented away from the plane of the nonwoven and particularly perpendicular to the plane, compared to three-dimensional anisotropic nonwovens. Fluff pulp fibers used in this invention are preferably about 0.5 - 5 mm long. The fibers are held together by a latex binder. The binder can be applied as either a powder or an emulsion. The binder is usually present in the dry laid capacity paper in the range of about 10-30 wt% and preferably about 20 - 30 wt% binder solids based on the weight of the fibers.

In another preferred embodiment, the dry-laid capacity paper comprises a thermally bonded blend of fluff pulp fibers and at least one of split film fibers or bicomponent polymer fibers. More preferably, the blend of fluff pulp fibers comprises fluff pulp fibers and bicomponent polymer fibers.

Split film fibers are essentially flat, rectangular fibers that can be or become electrostatically charged before or after being incorporated into the composite structure of the invention. The thickness of the split film fibers can be between 2 and 100 μm , the thickness can be between 5 μm and 2 mm and the length

can be between 0.5 and 1/jjnmJ. The preferred dimensions of the split film fibers . .. . .. . . ^T *. .··.: ^ö ···· ^r

However, they have a thickness of about 5 to 20 μm, a width of about 15 to 60 [im and a length of about 0.5 to 3 mm.

The split film fibers of the invention are preferably made from a polyolefin such as polypropylene (PP). However, any polymer suitable for making fibers can be used for the split film fibers of the composite structures of the invention. Examples of suitable polymers include, but are not limited to, polyolefins such as homopolymers and copolymers of polyethylene, polyterephthalates such as poly(ethylene terephthalate) (PET), poly(butylene terephthalate) (PBT), poly(cyclohexyl-dimethylene terephthalate) (PCT), polycarbonate and polychlorotrifluoroethylene (PCTFE). Other suitable polymers include nylon, polyamides, polystyrenes, poly-4-methylpentene-1, polymethyl methacrylates, polyurethanes, silicones, polyphenylene sulfides. The split film fibers can also comprise a mixture of homopolymers and copolymers. In the present application, the invention is exemplified using split film fibers made of polypropylene.

The use of PP polymers with different molecular weights and morphologies in layered film structures has been proven to produce films with the appropriate balance of mechanical properties and brittleness required for the production of split film fibers. These PP split film fibers can also subsequently be provided with the appropriate amount of crimp. All dimensions of the split film fibers can of course be changed during the production of the fibers.

One method of making the split fibers is disclosed in U.S. Patent No. 4,178,157. Polypropylene is melted and extruded into a film which is then blown into a large tube (balloon) into which ambient air is introduced or allowed to penetrate, according to conventional bubble-stretching techniques. Inflation of the balloon with air serves to quench the film and biaxially orient the molecular structure of the PP molecular chains, resulting in increased strength. The balloon is then collapsed and the film is stretched between two or more pairs of rolls in which the film is held in the nip of two contacting rolls, with different pressures applied between the two contacting rolls. This provides additional stretching in the machine.

direction, which is achieved by operating the second group of rollers at a higher surface speed than the first group. The result is an even greater molecular orientation of the film in the machine direction, which subsequently becomes the long dimension of the split film fibers.

The film may be electrostatically charged before or after it has been cooled. Although various electrostatic charging techniques may be used, two methods have been found to be most suitable. The first method involves passing the film approximately midway through a gap of about 3.75 - 7.5 cm (1.5 - 3 inches) between two DC corona electrodes. Corona bars with emitter pins made of metallic wire may be used, with one corona electrode having a positive DC voltage potential of about 20 to 30 kV and the opposite electrode having a negative DC voltage of about 20 to 30 kV.

The second preferred method uses the electrostatic charging techniques described in U.S. Patent No. 5,401,446 (Wadsworth and Tsai, 1995), referred to as Tantret.TM. Technique I and Technique II. Technique II, in which the film is suspended from insulated rollers as the film is passed around the inner periphery of two negatively charged metal cups with a positive corona wire of each cup, has been shown to impart the greatest voltage potentials to the films. In general, positive 1000 to 3000 volts or more can be imparted to one side of the films with Technique II, and similar magnitudes of negative sign to the other side of the charged film.

Technique I _1, in which films are contacted with a metal roller at a DC voltage of -1 to 10 kV and a wire at a DC voltage of +20 to +40 kV is placed about 2.5 to 5 cm (1 to 2 inches) above the negatively biased roller, with each side of the film being successively subjected to this roller/wire loading configuration, results in lower voltage potentials as measured on the surfaces of the films. Technique I typically achieves voltages of 300 to 1500 volts on the film surface with generally equal but opposite polarity on each side. However, it has been found that the higher surface potentials achieved with Technique II do not result in a

better measurable filtration performance of the webs made from split film fibers. For this reason and because it is easier to insert the film and guide it through the technology ! device, this method is mainly used to charge the films before the splitting process.

The cooled and stretched films can be electrostatically charged hot or cold. The film is then simultaneously stretched and slit into narrow widths, typically up to about 50mm. The slit, flat filaments are then collected in a tow which is crimped at a controlled number of crimps per centimeter and then cut to the desired staple length.

In a particularly preferred embodiment, the dry-laid high dust capacity paper comprises a mixture of fluff pulp fibers, biocomponent polymer fibers, and electrostatically charged split film fibers. Preferably, the fluff pulp fibers are present at about 5-85 wt.%, more preferably at about 10-70 wt.%, and most preferably at about 40 wt.%, the bicomponent fibers at about 10-60 wt.%, more preferably at about 10-30 wt.%, and most preferably at about 20 wt.%, and the electrostatically charged split film fibers at about 20-80 wt.%, and more preferably at about 40 wt.%. This dry-laid high dust capacity paper may be thermally bonded, preferably at high temperatures of 90-160 EC, more preferably at a temperature less than 110 EC, and most preferably at about 90 EC.

Other preferred embodiments of the dry laid capacity paper include a thermally bonded paper with 100% "mixed electrostatic fibers", a mixture of 20-80% mixed electrostatic fibers and 20-80% B/C fibers, and a mixture of 20-80% mixed electrostatic fibers, 10-70% fluff pulp and 10-70% B/C fibers. "Mixed electrostatic fiber" filters are made by mixing fibers with very different triboelectric properties and rubbing them against each other or against metal parts of machines such as wires or carding cylinders during carding. This makes one type of fiber more positively or negatively charged with respect to the other type of fiber and improves the Coulomb attraction for dust particles. The manufacture of filters with

·

These types of mixed electrostatic fibers are described in US Patent No. 5,470,485 and EP 0 246 811 A2.

In U.S. Patent No. 5,470,485, the filter material consists of a blend of (I) polyolefin fibers and (II) polyacrylonitrile fibers. The fibers (I) are bicomponent PP/PE fibers of the core/sheath or side-by-side type. The fibers II are "halogen-free." The (I) fibers also have some "halogen-substituted polyolefins," while the acrylonitrile fibers have no halogen. The patent mentions that the fibers must be thoroughly washed with nonionic detergent, alkali or solvent, and then rinsed well before being blended together so that they are free of lubricants or antistatic agents. Although the patent teaches that the nonwoven fabric produced should be needle punched, these fibers could also be cut to lengths of 5-20 mm and blended with thermal bicomponent bonding fibers of similar length and also with the possible addition of fluff pulp so that dry-laid thermally bonded paper can be used in this invention.

EP 0 246 811 describes the triboelectric effect when two different types of fibers are rubbed against each other. It teaches to use similar types of fibers as US Patent No. 5,470,485, except that the -CN groups of the polyacrylonitrile fibers are substituted by halogen (preferably fluorine or chlorine). After sufficient substitution of -CN by -Cl groups, the fibers can be called "modacrylic" if the copolymer comprises 35-85 wt.% acrylonitrile units. EP 0 246 811 teaches that the ratio of polyolefin to substituted acrylonitrile (preferably modacrylic) can range from 30:70 to 80:20 by surface area, and more preferably from 40:60 to 70:30. Similarly, U.S. Patent No. 5,470,485 teaches that the ratio of polyolefin to polyacrylonitrile fibers is in the range of 30:70 to 80:20 with respect to a surface area of the filter material. Thus, these ranges of polyolefin to acrylic or modacrylic fiber ratios can be used in the above proportions in the dry-laid thermally bonded capacity paper.

22

Meltblown fleece

A synthetic polymer fiber meltblown nonwoven fabric may optionally be employed as an intermediate layer between the multipurpose layer and the second filtration layer. The meltblown nonwoven intermediate layer increases the overall filtration performance by trapping particles that have passed through the multipurpose filtration layer. The meltblown nonwoven intermediate layer may also optionally be electrostatically charged to assist in filtering fine dust particles. The inclusion of a meltblown nonwoven intermediate layer results in an increase in pressure drop for a given dust loading compared to compositions that do not include a meltblown nonwoven intermediate layer.

The meltblown fleece preferably has a basis weight of about 10-50 g/m ² and an air permeability of about 100 -1500 l/(m ² s).

High-volume meltblown nonwoven

The development of a high bulk MB web used upstream of the filtration grade MB web as a pre-filter instead of a wet laid capacity paper or dry laid capacity paper provides improved vacuum cleaner bags. The high bulk MB pre-filter can be manufactured in a meltblown process using a cooled quench air or cooling air with a temperature of about 10 EC. In contrast, conventional MB usually uses room air at an ambient temperature of 35 - 45 EC. Also, the collection distance between the MB nozzle exit to the web take-up belt is increased to 400 - 600 mm in the high bulk MB process. For normal MB manufacturing, the distance is usually about 200 mm. In addition, a high bulk MB nonwoven is produced using a lower temperature stretch air temperature of about 215 - 235 EC instead of the normal stretch air temperature of 280 290 EC and a lower MB melt temperature of about 200 - 225 EC ₁ compared to 260 to 280 EC for filtration grade MB production. The colder quenching air, lower stretch air temperature, lower melt temperature and the larger collection distance cools the MB filaments more. The removal of heat results

in a lower stretching of the filaments and thus in larger fibre diameters ....... ........... .. .........

·

·

23

than would be found in typical filtration grade MB nonwovens. The cooler filaments are less likely to thermally melt together when deposited on the collector. This gives the high bulk meltblown nonwoven a more open surface. Even with a basis weight of 120 g/m ² , the air permeability of the high bulk meltblown nonwoven is 806 l/(m ² s). In contrast, a much lighter (e.g. 22 g/m ² ) filtration grade MB PP nonwoven has a maximum air permeability of only 450 l/(m ² s). The filtration performance of the high bulk MB nonwoven, as determined by the DIN 44956-2 test, was 98%. When the two were placed together with the high-bulk MB nonwoven on the inside of the bag, the air permeability was still 295 l/(m ² s) and the filtration efficiency of the pair was 99.8%. The high-bulk meltblown nonwoven can be uncharged or optionally electrostatically charged provided that the nonwoven is made of a material with suitable dielectric properties.

The high bulk MB nonwoven of this invention is different from the "filtration grade MB" also used in the multilayer vacuum filter structure of this disclosure. The filtration grade MB nonwoven is a conventional meltblown nonwoven generally characterized by a low basis weight, typically about 22 g/m ² , and a small pore size. Additional typical characteristics of filtration grade MB nonwoven made of polypropylene are shown in Table I. A preferred high bulk MB nonwoven made of polypropylene optimally comprises about 5-20 wt.% ethylene vinyl acetate. A filtration grade MB nonwoven generally has a high dust removal efficiency, i.e., greater than about 99%.

Table I

Preferred More preferred Most preferred

Filtrationsqrad-MB-PP

Weight, g/m ² 5-150 10-50 22 Thickness, mm 0.10-2 0.10-1 0.26 Air permeability, l/(m ² s) 100-1500 200 - 800 450 Tensile strength, MD, N 0.5-15 1.0-10 3.7 Tensile strength, CD, N 0.5-15 1.0-10 3.2 Fiber diameter, pm 1-15 1-5 2-3 High-volume MB-PP Weight, g/m ² 30-180 60-120 80 Thickness, mm 0.3-3 0.5-2 1.4 Air permeability, l/(m ² s) 300 - 8000 600 - 3000 2000 Tensile strength, MD, N 1.0-30 2-20 10 Tensile strength, CD, N 1.0-30 2-20 9.2 Fiber diameter, pm 5-20 10-15 10-12

High bulk MB nonwoven is similar in filter performance to the dry-laid and wet-laid capacity papers described above. Therefore, high bulk MB nonwoven is well suited to removing large amounts of large dust particles and retaining large amounts of dust. Accordingly, high bulk MB nonwoven is suitable to be placed upstream and as a pre-filter of the filtration grade MB nonwoven in a vacuum filter structure of this invention.

(Modular) spunblown nonwoven

A new type of melt blow technology as described in G. Ward, Nonwovens World, Summer 1998, pages 37-40 is available to produce a (modular) spunblown nonwoven suitable to be used as the coarse filter layer in the present invention. Optionally, the spunblown nonwoven

as a filtration grade meltblown nonwoven layer as desired in the new vacuum cleaner bag structure. Specifications of the (modular) spunblown nonwoven are shown in Table II.

The process for producing the (modular) spunblown nonwoven is generally a meltblown process with a coarser modular nozzle and using colder stretching air. These conditions produce a coarse meltblown nonwoven with higher strength and air permeability at a comparable basis weight to conventional meltblown nonwovens.

Microdenier spunbond nonwoven

A spunbond ("SB") nonwoven, sometimes referred to herein as a microdenier spunbond, can also be used in this invention as the filtration grade meltblown nonwoven layer. Specifications of microdenier spunbond are listed in Table II. A microdenier spunbond is particularly characterized by filaments having a diameter of less than 12 μηη, which corresponds to 0.10 denier for polypropylene. By comparison, conventional SB nonwovens for disposable items typically have filament diameters averaging 20 pm. A microdenier spunbond can be purchased from Reifenhauser GmbH (Reicofil III), Koby Steel, Ltd., (Kobe-Kodoshi Spunbond Technology) and Ason Engineering, Inc. (Ason Spunbond Technology).

Table II

Preferred More preferred Most preferred

(Modular) Spunblown Weight, g/m ² Thickness, mm

Air permeability, l/(m ² s Tensile strength, MD, N Tensile strength, CD, N Fiber diameter, pm

Microdenier spunbond

(Ason, Kobe-Kodoshi, Reicofil Weight, g/m ² Thickness, mm

Air permeability, l/(m ² s) Tensile strength, MD, N Tensile strength, CD, N Fiber diameter,

Weight, g/m ² 20-150 20-80 40 Thickness, mm 0.20 - 2 0.20-1.5 0.79 Air permeability, l/(m ² s) 200 - 4000 300 - 3000 2000 Tensile strength, MD, N 10-60 15-40 — Tensile strength, CD, N 10-50 12-30 — Fiber diameter, pm 0.6 - 20 2-10 2-4 Microdenier spunbond PP

20-150 20-80 40

0.10-0.6 0.15-0.5 0.25

500-10000 2000-6000 3000

10-100 20-80 50

10-80 10-60 40

4-18 6-12 10

Referring to the drawings and figures, Fig. 1 to Fig. 3 show existing commercial vacuum cleaner bag designs. In Fig. 1, a conventional structure is shown which consists of a wet-laid tissue web 24 on the inside (upstream side) of the bag and a filter paper 25 on the outside (downstream side) of the bag. The tissue web serves as a pre-filter, removing only the largest dust particles. The filter paper typically filters and retains in its porous structure particles larger than 10 - 20 pm.

Fig. 2 shows a two-layer vacuum cleaner bag construction in which a meltblown (MB) fleece 26 serves as both a pre-filter, coarse filter and fine filter by removing particles with a diameter of less than 5 pm. However, MB fleeces have much smaller pores than typical vacuum cleaner filter papers and cannot retain dust as efficiently. In addition, the MB fleece is often electrostatically charged to improve filtration performance. When the MB fibers are covered with dust, the electrostatic field can be greatly reduced. The prior art using this design is the publications 0 375 2.34.B1 and 0 375

234 α1. The spunbond (SB) layer 27 primarily provides support for the MB web and improves the abrasion resistance of the outside of the bag. Other similar prior art is shown in US Patent No. 4,589,894 (3M) and 3M's EP 0 161 790 A1. In the 4,589,894 patent and EP 0 161 790 A1, an SB layer is also used on the inside of the bag and serves to further support and protect the MB web.

Fig. 3 illustrates a three layer vacuum cleaner bag construction in which a wet laid support web 28 is added to act as a pre-filter for only very large dust particles and to protect the MB web from abrasion. The MB web 29 serves to filter small and large particles and thus has a tendency to clog very quickly, thereby increasing the pressure drop more quickly than a conventional filter paper. The outer layer of filter paper 30 is actually redundant with respect to filtration and serves primarily to support the top surface of the MB web, reinforce the bag and improve the abrasion resistance of the outer surface of the bag. Prior art examples illustrating similar designs include EP 0 338 479 A1 (Gessner) and US Patent No. 5,080,702 (Home Care Industries) discussed above. In the latter, no interlayer of tissue web was used.

Fig. 4 illustrates the new three-layer vacuum filter structure in which a wet-laid capacity paper, dry-laid capacity paper, or other suitable type of nonwoven coarse filter 10 is placed upstream of a filtration grade MB nonwoven 11. This upstream layer serves to remove larger dust particles and to hold the dust within its structure. This layer should preferably have a less dense, more lofty structure capable of holding a large amount of dust without increasing pressure drop. A high loft MB nonwoven is shown in the figure as nonwoven 10. It is preferred that the inner MB nonwoven be more lofty ("loftier") and more open than nonwoven 11 so that it can also hold more dust without increasing pressure drop.

Fig. 5 shows the new vacuum cleaner bag construction with a three-layer construction in which a wet-laid capacity paper 31 is arranged in front of the filtration grade MB fleece 32, and a spunbond (SB) nonwoven 33 on the outside of the bag

structure. The inner layer 31 may be a wet laid, dry laid (modular) spunblown, microdenier spunbond or other type of nonwoven filter having the proper porosity and dust holding capacity. It is preferred that it have a higher porosity and dust holding capacity than standard filter paper that has been used in the prior art vacuum cleaner bags. The outer coarse filter layer may be a spunbond, wet laid, dry laid or hydroentangled nonwoven, netting or other type of scrim or nonwoven.

Fig. 6 shows a vacuum cleaner bag with the same construction as shown in Fig. 5, except that a wet laid capacity paper 34 is placed in front of the MB fleece 35, and the spunbond layer 36 is again placed on the outside of the bag. The wet or dry laid filter papers were placed on the inside of the bag structure to help support the MB fleece and to filter and store medium and larger sized dust particles so that the MB fleece could efficiently filter the smaller particles without clogging.

Fig. 7 illustrates the new vacuum cleaner bag construction in which a fleece/carbon combination 214 + 215 of 50 g/m ² and 150 g/m ² respectively, serving as an odor adsorbing layer, has been substituted for the SB 33 of Fig. 5. In this construction, it is important that the fleece 214 downstream of the activated carbon fibers or activated carbon fibers prevents these activated carbon fibers from entering the bag compartment of the vacuum cleaner and therefore this fleece should preferably be electrostatically charged.

Figures 8A through 8AA illustrate numerous possible embodiments of the new vacuum cleaner bag construction. In Figure 8A, an SB layer 37 forms the outer layer of the bag and serves to reinforce the bag and protect the inner filtration grade MB fleece 38. The electrostatically charged MB fleece layer efficiently removes particles smaller than 0.1 pm in diameter. The vacuum cleaner bag filter paper 39 supports the MB fleece and filters and retains medium and larger sized dust particles within its structure. This paper also provides the necessary stiffness for the construction for easy fabrication into vacuum cleaner bags on standard vacuum cleaner bag manufacturing equipment. The layers in Figure 8A are not bonded together.

The structure of Fig. 8B is the same as Fig. 8A, except that a wet-laid support tissue web 43 is arranged upstream of the paper 42. The support tissue web filters out only very large dust particles.

The structure of Fig. 8C is the same as in Fig. 8A except that a netting scrim 47 is thermally or adhesively (e.g., with glue) bonded upstream of and to the coarse filter paper 46. That is, the scrim and coarse filter paper are bonded, preferably permanently bonded. At least any two adjacent layers of the bag may be bonded. By "permanently bonded" is meant that the bond is intended to be effective throughout the normal life of the bag. Bonding may be accomplished by any suitable method, such as chemical adhesives, thermal bonding, and ultrasonic bonding.

In Fig. 8D, the outer SB layer 48, the filtration grade MB nonwoven layer 49 and the SB support layer 50 are bonded together. The filter paper layer 41 is located upstream of the SB/MB/SB composite and also increases the stiffness of the bag construction so that it can be easily made into a vacuum cleaner bag on a standard bag making machine.

In Fig. 8E, the SB layer 53, MB layer 55 and filter paper layer 57 are bonded together by a porous hot melt adhesive 54 and 56. Fig. 8F is the same as Fig. _8E1 except that a wet laid support tissue web 64 is bonded to the construction by a hot melt adhesive 63. Fig. 8G is the same as Fig. 8D except that the filter paper 69 is bonded to the bonded SB 65, MB 66 and SB 67 composite by a hot melt adhesive 68. Fig. 8H is the same as Fig. 8G except that the wet laid tissue web 76 has been bonded to the construction by a hot melt adhesive 75. Fig. 81 is the same as Fig. 8E except that the netting 82 has been adhesively bonded to the structure without the use of a hot melt adhesive.

The structures shown in Figures 8J to 8AA all comprise a composite nonwoven/carbon layer that serves as an odor absorbing layer. The composite comprises a carbon fiber layer upstream of a nonwoven support layer. In

Fig. 8J, a fleece/carbon combination 83 + 84 forms the outer most downstream layer of the bag, a filtration grade MB fleece 85 efficiently filters particles with a diameter smaller than 0.1 pm and a coarse filter paper 86 filters and holds dust particles of medium and large size in its structure.

Fig. 8K is the same as Fig. 8J except that a wet laid support web 91 is placed upstream of the coarse filter paper 90. The support web filters out only very large dust particles. Fig. 8L is the same as Fig. 8K except that a netting scrim 96 is adhesively bonded to the coarse filter paper 95. In Fig. 8M, the SB layer 99, MB layer 100 and SB layer 101 are bonded together, increasing the rigidity of the bag construction. In Fig. 8N, a nonwoven/carbon 103+104 is bonded to the filtration grade MB nonwoven 106 by a porous hot melt adhesive 105. The coarse filter paper 108 is bonded to the MB 106 by a hot melt adhesive 107 in the same manner. Fig. 80 shows a similar construction in which the support web 116 is bonded to the filter paper 114 by a porous hot melt adhesive at 115. Fig. 8P is another construction with a hot melt adhesive bond at 119 and 123. The SB layers 120 and 122 are bonded to opposite sides of the filtration grade MB web 121 to increase the stiffness of the construction.

Fig. 8Q is the same as Fig. 8P but with a porous hot melt adhesive at 133 and a support fleece 134 added upstream of the coarse filter paper 132.

The structure of Fig. 8R includes a netting scrim 143 adhesively bonded to the upstream side of the coarse filter paper 142. In Fig. 8S, the carbon fleece 146+147 has been moved downstream of the coarse filter paper 148 and upstream of the filtration grade MB fleece 145. The MB 145 and SB 144 layers have been moved to the outside as seen in many of the embodiments shown. Fig. 8T is the same as Fig. 8S with a support fleece 154 positioned upstream of the coarse filter paper 153. In Fig. 8U, the support fleece of Fig. 8T has been replaced with a netting scrim 160 adhesively bonded to the coarse filter paper 159.

The structure of Fig. 8V has an outer layer of SB 161, the filtration grade MB fleece 162 and SB 163 are adhesively bonded together and the carbon/fleece

&igr; π·· :.-..& vngr; L ^: &eegr;&eegr;;;·=

164+165 between these bonded layers and the coarse filter paper 166. The layers 161,162 and 163 are preferably thermally point bonded with a total bonded area of 5-50%, more preferably 10-20%. Alternatively, these layers may be bonded using an adhesive. The layers 164 and 165 are preferably adhesively bonded together. The three-layer composition 161/162/163 and the two-layer composition 164/165 are preferably not bonded together.

In Fig. 8W, the SB 169 and the filtration grade MB 171 are bonded together with a porous hot melt adhesive 170 and the carbon fleece is bonded to the coarse filter paper and the MB with hot melt adhesive layers 172 and 175. Fig. 8X is the same structure as Fig. _8W1 except that an additional support fleece 186 is bonded to the coarse filter paper 184 with a porous hot melt adhesive 185. Fig. 8Y shows an outer composite layer of SB 187, MB 188 and SB 189 adhesively bonded together. The carbon fleece 191/192 is bonded to this outer bonded layer and the coarse filter paper with a porous hot melt adhesive 190 and 193. Fig. 8Z shows the same structure as Fig. 8Y but with a supporting fleece 204 which is bonded to the coarse filter paper 202 with a porous hot melt adhesive 203.

Finally, Fig. 8AA illustrates a SB 205 and a filtration grade MB fleece 207 bonded with a porous hot melt adhesive 206. The carbon fleece 209 + 210 is bonded to the MB 207 in the same manner. The coarse filter paper 212 is bonded by means of a hot melt adhesive 211 and a netting scrim 213 is adhesively bonded to the coarse filter paper 212.

The activated carbon fiber layer may have the following configurations: carbon granules between layers of nonwoven, paper with activated carbon fibers, paper with activated carbon, activated carbon fabrics (nonwoven), activated carbon fabrics (woven fabric), activated meltblown of pitch and activated carbon fibers blown into a MB layer. The activated carbon layer preferably has a surface area of about 500-3000 g/m ² (BET N ₂ method), a weight in the range of about 25-500 g/m ² and an air permeability of about 500-3000 l/(m ² ?).

In another embodiment, the improved efficiency bag comprises a multipurpose filtration layer disposed upstream of a second filtration layer. The multipurpose filtration layer may be either a dry-laid high dust capacity paper or a wet-laid high dust capacity paper, a high bulk meltblown, or a (modular) spunblown. The second filtration layer should be a wet-laid filter paper, dry-laid filter paper, or a spunbond that is electrostatically charged, preferably prior to making the bag.

The term "multi-purpose filtration layer" is used to mean that the pre-filter layer of dry-laid or wet-laid capacity paper is capable of performing several functions simultaneously. This layer protects the downstream second filtration layer from shock loading by blocking large salvos of dirt particles that can be much larger than 10 mm. In addition, the multi-purpose layer filters particles of about 10 mm in size. Its porosity and thickness are sufficiently large that this layer has the capacity to store within the layer a large amount of dirt and dust particles while allowing the air flow to penetrate the layer at a high rate without dramatically increasing the pressure drop through the composite structure. Therefore, the bag can continue to operate at an optimum air flow for vacuuming for a time long enough for the bag to reach the particle storage capacity. Roughly speaking, the multi-purpose filtration layer cleans the air of most particles except for the fine dust particles, which are removed by the second filtration layer.

The term "second filtration layer" means a filter layer designed to remove from the air passed through the multi-purpose layer a sufficient amount of fine dust particles to give a very high overall filtering efficiency, preferably over 99%. The second filtration layer is less porous than the multi-purpose layer. It may have a medium porosity because the multi-purpose filtration layer performs the overwhelming majority of the filtration load, leaving only a small amount of fine dust particles to be removed by the high efficiency filter layer. This is particularly the case when the multi-

purpose filtration layer comprises electrostatically charged split film fibers or when an electrostatically charged high bulk meltblown, modular spunblown or microdenier spunbond is used. In these cases, the upstream layers are effective in removing at least some of the fine dust particles as well as larger particles. This leaves even less fine dust to be removed by the second filtration layer.

The various layers of the enhanced performance bag are typically bonded to adjacent layers at the bag inlets and outlets, and sometimes at the bag seams. They may be unbonded to adjacent layers in other areas of the bag structure, or may be bonded using various methods. For example, the layers may be bonded using adhesives, thermal bonding, ultrasonic bonding, or a combination of these methods.

EXAMPLES Method and test procedure

Unless otherwise stated, in the following examples the basis weight was determined using ISO 536, the thickness using DIN 53 105 (0.2 bar), the air permeability using DIN 53 887, the tensile strength in the machine direction (MD) and cross-machine direction (CD) using DIN 53 112, the Mullen burst pressure (MBP) using DIN 53 141 and filtration properties using T.S.I. 8160 filter tester. In the figures, the air flow direction is shown by arrows.

The DIN 44956-2 (April 1980) test was used to characterize the performance of vacuum bag filter compositions with respect to the filtering of fine dust particles. The test essentially involves filtering a 500 mg sample of SAE fine test dust through a circular 200 square centimetre filter medium to be tested using an air flow of 10 litres per second for a period of 30 seconds. The pressure drop through the test filter medium is measured before and after filtration. An absolute filter is used to capture particles passing through the test filter. A retention coefficient, expressed as a percentage, is

calculated from the quotient of the weight of the sample captured by the test filter divided by the sum of the sample weight captured by the test filter and the sample weight captured by the absolute filter.

Air permeability test after fine dust loading: The dust loading part of DIN 44956-2 was carried out in 0.5 gram increments on seven bags of each sample. However, the pressure drop values were not recorded again. The maximum sustained air permeability values were then determined on the bags that had the specific dust loading levels.

A TSI Model 8110 filter tester was used to measure media filtration performance. The Model 8110 tester was used to aerosolize a 2.0% sodium chloride solution (20 g NaCl in 1 liter water) using an aerosol generator. The NaCl water droplets in the aerosol were heated and NaCl crystallites with a diameter of 0.1 μιδ were formed. The mass concentration of NaCl in the air was 101 mg/m ³ . Photometry was used to determine the volume concentration of air in the upstream volume of the media (Cu) by the volume concentration of air in the downstream volume of the media (Cd). The penetration ability of the NaCl particles was calculated as:

Penetration = P = [Cd/Cu] (100 %) Examples 1-7

Samples of various vacuum cleaner bag constructions shown in Figures 1-3 and A- 7 were prepared and tested. Examples 1, 2 and 3 are typical prior art constructions and Examples 4, 5, 6 and 7 are representative of bags according to this invention. The characteristics of the layers of the prior art and the new bag constructions were determined and are shown in Tables III and IV. The weight, thickness, air permeability, pore diameter and filtration grade permeability of the entire compositions are shown in Table V. Table V also shows the pressure drop and air flow through the composition at a particulate loading measured in increments of 0 to 2.5 grams.

using DIN 44956-2. The pressure drop data in Table V are graphically presented in Fig. 9 and 10. The air flow data are graphically presented in Fig. 11.

Figure 9 shows that in the three prior art designs, Examples 1, 2 and 3, the pressure drop increases significantly after only 1.0 gram of dust loading. Prior art Examples 2 and 3, both containing MB products, give substantially smaller increases in pressure drop for dust loading up to 1.5 grams of dust. After this point, the pressure drop in both Examples 2 and 3 increases significantly with increasing dust loading because the relatively small pores in the MB products became clogged with dust particles and cake.

Examples 5, 6 and 7 of this invention showed very little pressure drop increase even after the maximum loading of 2.5 grams of dust. Moreover, the initial filtration efficiencies of Examples 5-7 were at least as high as the prior art samples with MB products at 99.6%. Example 1, which did not contain MB, had a lower filtration efficiencies of 96% and had the highest pressure drop with dust loading. A significant difference between Examples 2 and 3 and Examples 5-7 is that the coarse filter paper was located upstream of the MB mat in the last three examples. This allowed the filter paper to filter and retain the dust particles, especially the larger dust particles, so that the filtration grade MB mat could filter out the smaller size dust particles without clogging the pores, even at a loading of 2.5 g/m ² .

In addition, both the MB and filter paper used in Examples 4, 5, 6 and 7 are much more open than the corresponding materials used in Examples 1, 2 and 3. The special coarse filter paper is much more open as is evident from the high air permeability levels. This allows the special filter paper to hold more dust. Similarly, the air permeability of the MB in Examples 4, 5, 6 and 7 is much higher and the high loft MB nonwoven is much higher in loft and less dense. This is accomplished in various ways in the manufacture of the MB, but often it is done by increasing the distance between the nozzle and the collector to allow greater quenching of the MB film so that the semi-molten filaments have more time to cool.

! Ir " ^:: ":=:; OU zr.\"ii"\ \ H

and fully solidified before being deposited on the collector. Water spray or cool quenching air can also be used to accelerate the cooling of the extruded MB filaments.

The differences in the MB products are further highlighted in Fig. 10. Example 2 from Fig. 9 is again graphically represented in Fig. 10 and labeled "3M". The new example, labeled "Example 4, Airflo" was made by first producing a very porous, very lofty, high bulk MB nonwoven weighing 120g/ ^m2 , which was then used as the outermost upstream layer. This MB nonwoven was more open and porous than the conventional MB products used in Examples 2 and 3. Accordingly, it served to filter out and retain a large amount of dust particles. Exceptionally, the Airflo Example 4, even with the special 120g/m ² inner MB layer and a 22g/m ² middle layer, resulted in a negligible increase in pressure drop at dust loadings up to the maximum dust loading of 2.5g/m ² .

Although Example 1 did not contain any MB fleece at all and had a smaller pressure drop increase than Examples 2 and 3, it still had a significantly larger pressure drop increase with loading than Examples 5 and 6 with MB fleeces. Note that the weight of the MB polypropylene fleece used in three of the examples was 22 g/m ² . Nevertheless, the special placement of the coarse filter paper and the filtration grade MB fleeces in Examples 5 and 6 resulted in dramatically smaller pressure drop increases because this allowed the filter paper to remove and retain the large and medium sized particles and the filtration grade MB fleece only had to filter and retain the finer particles. The difference between Examples 5 and 6 in pressure drop, even at the highest dust loading of 2.5 grams, was small. The pressure drop was slightly larger with the wet-laid paper because the hydrogen bonds between the cellulose molecular chains during wet processing make the wet-laid paper denser with slightly smaller pores at the same weight.

Figure 11 shows the results of examples, further dramatizing the noticeable improvements obtained by placing a coarse filter paper upstream of the filtration grade MB fleece (on the inside of the bag) of this invention.

FiF ν q q ·;:= &igr;., &kgr;&eegr;&eegr; in the

•&ogr; ·

Separate bags of Examples 1-3 and 5-7 were loaded with particulate matter in 0.5 gram increments of 0, 0.5, 1, 0, 1.5, 2.0 and 2.5 grams of dust. Then the six bags with varying levels of dust loading were subjected to an air permeability test in which the maximum sustained amount of air was passed through each bag sample. As can be seen in Figure 11, the new bag design represented by Example 6 had a maximum sustained airflow without dust loading of 445 l/(m ² s) compared to only 225 l/(m ² s) of the prior art Example 3. At 1.5 gram dust loading, Example 6 had a sustained airflow of 265.4 l/(m ² s) compared to only 34.9 l/(m ² s) with the conventional Example 3, and at 2.5 gram loading the performance differences were even more notable -199.8 and 21.9 l/(m ² s). Example 2 had a maximum sustained airflow of 411 l/(m ² s), but already at 1.0 gram dust loading the values dropped to those of conventional bag designs.

A conventional vacuum cleaner bag suffers from relatively low airflow, as can be seen from the 18,14.9 and 21.9 l/(m ² s) of Examples 1,2 and 3 in Fig. 11 after the sixth dust loading. It is almost impossible to add another layer of material to these designs without dramatically reducing the airflow. In Examples 5 and 6 and Fig. 11, due to the excellent performance of the new designs, an opportunity was created to add new functions to the vacuum cleaner bag. In today's vacuum cleaners a number of different filters are used, including activated carbon filters, to absorb odors. Very often 3-5 different filters are used in vacuum cleaners, each of which has its own lifespan.

Due to the high air flow of the present invention, it is possible to increase the functionality, such as by adding an additional layer of activated carbon fibers in the bag constructions, without requiring a separate filter element. The construction has a number of advantages, namely:

1. Easy to use vacuum cleaner for the end user, the separate odor filters do not need to be replaced.

2. Carbon filters in their current form have a negative impact on airflow and sometimes dramatically reduce the overall performance of the vacuum cleaner.

3. The carbon filter is housed in a separate plastic molded housing, which can be eliminated by the carbon layer in the vacuum cleaner bag.

4. Due to the lifespan of a vacuum cleaner bag, the optimal function of the active carbon fibers can be expected during the usage time of the vacuum cleaner bag.

5. Since the separate plastic housing is no longer needed, the construction of the vacuum cleaner becomes simpler and therefore cheaper.

6. The amount of activated carbon fibers can be optimized for the life of the vacuum cleaner bag.

7. Due to the space limitations in a vacuum cleaner, the activated carbon fiber filters are relatively small and very often do not have a large enough surface area to absorb the odors properly.

8. By adding an additional layer of activated carbon fibers to the new bag design, the problem of limited filter surface was solved.

RF -X ₁ C ₁ vi,. &kgr; Γ=··

39 Table III

.::::F\q. No. /Shift No.

'Weight ISO 536 g/m ²

·

:**«TThickness DIN 53 105 0.2 bar mm

·

/;::*Air permeability DIN 53 887 l/(m ² s)

. . Tensile strenght

* ;*·· Machine direction DIN 53 112 N . ... Cross direction DIN 53 112 N

.••••.Pore diameter pm :*"': Mullen burst pressure DIN 53 141 bar

_m Filtration properties DIN 44956-2

:...:. Filtration degree permeability %

¹ Min 121.91, Max 64

² min 16,52, Max >300

example 1 3/30 Example 3 3/28 1/25 1/24 45 3/29 13 45 13 0.2 22 0.05 0.2 0.05 400 0.26 2100 400 2100 37 480 >6 37 >6 20 2.8 >1.5 20 >1.5 2.9 MFP 39,57 ² MFP 23.43 ¹ 1.2 MFP 23.43 ¹ 0.3 1.2 0.3 0.5

Fig. No. /Layer No. •"Poison weight ISO 536 g/m ² Thickness DIN 53 105 0.2 bar mm . Air permeability DIN 53 887 l/(m ² s)

rTensile strength

^-ÜMachine direction DIN 53 112 N \[Cross direction DIN 53 112 N *:Pore diameter μ&igr;&tgr;&igr;

Table IV

Example 4 Example 5 Examples Example 7

4/(12+11) ¹ 4/10 5/(33+32) ¹ 5/31 6(36+35) 6/34 7/(214+215) ³ * 7/216

39 120 39 50 39 77 200 0.33 1.4 0.33 0.32 0.33 0.94 0.9 510 510 2900 510 1850 2000 11.6 11.6 16 11.6 6.1 7.8 7.8 7 7.8 5.4 MFP
17.67 ² MFP
17.67 ² MFP
17.67 ²

0.7

70.5 94

87

::JVftjllen burst pressure DIN 53 141 bar

'"£ ijtration properties DIN 44956-2

Filtration degree permeability %

—^Spunbond (17 g/m ² ) plus meltblown (22 g/m ² ) composite
"'toin 10.86, Max 40.25

³ Fleece (50 g/m ² ) plus carbon (150 g/m ² ) composite, inner surface BET N ₂ method 1050-1400 m ² /g, microporous 2 nm pore size

⁴ Min 10.75, Max 40.27

⁵ min 17.67, Max >300

7/216 7/217 50 50 0.4 0.32 470 2900 2.9 16 3 7 MFP
7.69 ²
0.5 MFP
53.39 ²
0.007

Table V

•"Flg. No.

PSiweight ISO 536 g/m ²

:. Thickness DIN 53 105 0.2 bar mm

::[Ajft permeability DIN 53 887 l/(m ² s)
^: .:R©ren diameter pm
i'.FÖtration properties DIN 44956-2
•*:"Filtration degree permeability%
^: ..i_tiftstrom at 2 mbar I

'•••Filter resistance pressure drop 1 mbar

"Tilter resistance pressure drop 2 mbar

^: ...filter resistance pressure drop 3 mbar

^: "'Filter resistance pressure drop 4 mbar

Filter resistance pressure drop 5 mbar

Filter resistance pressure drop 6 mbar

Flow with fine dust 0.0 grams l/(m ² s)*

Ex. 1 Ex.

1 2

58 80

0.25 0.95

330 450

MFP 16.53 ¹

96 99.6

6.4 8.19

3.21 2.26

8.9 4.44

24.19 10.42

51.64 30.14

79.58 85.7

110 120

411 420

Example 3 Example 4 Example 5 Example 6 Example

3 4 5 6 7

80 159 89 116 300

0.51 1.73 0.65 1.27 1.62

225 465 420 400

13.37 4.48

99.8 99.7 99.8 99.7

8.6 8 7.3

3.46 2.34 2.53 2.8

3.93 3.18 4.44 3.5

25.87 5.19

4.35 10.42 4.91 6.54 30.14 7.02

53.05 6.15 10.34 85.7 11.03 100.32 7.53 16.39 120 16.98

455

445 410

Flow with fine dust 0.5 grams l/(m ² s)* Flow with fine dust 1.0 grams l/(m ² s)* Flow with fine dust 1.5 grams l/(m ² s)*

..Flow with fine dust 2.0 grams l/(m ² s)*

·

with fine dust 2.5 grams l/(m s)*

200.6 226 150 320 361 301 130.1 1365 101 258 310 235 71 62.4 34.9 183.7 265.4 162 44 27.4 27 149.6 224.1 135 18 14.9 21.9 109.7 199.8 105

r-.Win 8.45, Max 49.42
^: .f.tfei 2 mbar

Comparison example 1

Fig. 12 shows a cross-section of a commercially available vacuum cleaner bag structure 51' consisting of a wet-laid tissue nonwoven layer 52' on the inside (upstream air side) of the bag and a wet-laid standard filter paper 53' on the outside (downstream air side) of the bag. The properties of the individual layers and the composite structure are shown in Table IV. The liner primarily protects the wet-laid filter paper from abrasion but also pre-filters out some of the largest particles. The wet-laid filter paper typically filters out particles larger than about 10 pm and some smaller particles.

Comparison example 2

Fig. 13 shows a cross-section of a conventional three-layer vacuum cleaner bag structure 54" in which a wet-laid tissue support web 55' with very low dust holding capacity has been added upstream of an MB web 56' to protect against abrasion, and a wet-laid filter paper 57' is placed on the outside (downstream) to protect the bag from abrasion, to improve rigidity for bag manufacture, and to provide additional air filtration. The properties of the individual layers and the composite structure are shown in Table VI.

Examples 8-10

Fig. 14 illustrates a new three-layer composite vacuum cleaner bag structure 58' of Example 8 having a high dust capacity wet-laid paper layer 59' on the inside (upstream air side) in front of a meltblown filter layer 60'. A highly air permeable wet-laid filter paper layer 61' is on the outside (downstream air side).

Fig. 15 illustrates a new inventive composite vacuum cleaner bag structure 62' of Example 9 in which a dry laid high dust capacity paper 63' consisting of 100% fluff pulp fibers held together by 20% by weight latex binder

medium, is arranged as the inner layer, and a conventional wet-laid filter paper 64' is the outer layer.

Fig. 16 illustrates a new vacuum cleaner bag construction 65' of Example 10 consisting of a thermally bonded, dry laid, high dust capacity paper 66' at the upstream position inside the bag with a high permeability, wet laid filter paper 67' on the outside of the bag. The fiber content of the dry laid, high dust capacity paper 66" consists of a blend of 40% fluff pulp fibers, 40% split film fibers and 20% bicomponent polymer fibers. The properties of the individual layers and the composite structures are shown in Table VI, which compares the filtration properties of various composite structures at a flow of 100 l/min. The data in Table VI show that the structures of Examples 8 and 10 produce dramatically increased filtration performance compared to Comparative Example 1 with only a slight increase in pressure drop. Example 8 also produces slightly better filtration performance at the same pressure drop as Comparative Example 2. Example 9 compares well with the structure of the commercially available comparative example 1.

Each of the example structures described above was tested for particulate matter loading and the results are shown in Table VI. Figure 17 is a graphical representation of the pressure drop of the bag structures as a function of particulate matter loading in grams, where curves AE represent Comparative Examples 1 and 2 (A and B) ₁ and Examples 8-10 (C, D and E). The graph shows that conventional bag structures quickly achieve high pressure drops at very low loadings (i.e., about 100 mbar at less than 2.5 g). Example 8 achieved a correspondingly high pressure drop after 3.5 g of dust loading, an improvement of about 40%. Examples 9 and 10 provided remarkably superior particulate loading results by achieving about 100 mbar pressure drop at about 10 g and about 12.5 g loading and with a pressure drop not exceeding about 30 mbar at a particulate loading of 6.5 g and about 40 mbar until after about 7.5 g. These results demonstrate an improvement of about 300-400% compared to conventional filter designs. In particular, Examples 9 and 10 do not include an MB filter interlayer between the upstream multipurpose high dust capacity layer and the downstream second filtration layer.

Additional examples of contemplated composite vacuum cleaner bag structures having improved efficiency and intended to fall within the definition of the present invention are illustrated in Figures 18-20. In particular, Figure 18A shows a two-layer structure in which the upstream multipurpose layer is a dry-laid filter composition of only fluff pulp fibers held together with a dried latex binder or a blend of bicomponent polymer fibers and fluff pulp fibers thermally bonded. The multipurpose layer has high air permeability and dust holding capacity.

Fig. 18B also shows a two-layer structure in which the multipurpose layer is a three-component blend of fluff pulp fibers, bicomponent polymer fibers, and electrostatically charged split film fibers. Again, the blend is held together by thermal bonding, particularly of the low melting bicomponent polymer fiber composition.

Fig. 18C shows another two-layer structure with specially developed wet-laid filter paper with high dust holding capacity at the upstream position. The fibers in the wet-laid paper are a mixture of synthetic fibers and natural, i.e. wood pulp, fibers. Preferably, the synthetic fibers are polyester and more preferably polyethylene terephthalate. The fibers are bonded together by means of a latex binder at about 20-30 wt% dry binder solids based on the fiber weight.

Figure 18D illustrates a two-layer structure in which the upstream multipurpose layer comprises polyolefin and preferably polypropylene fibers. This layer is electrostatically charged, preferably using the Tantret (TM) technique.

Fig. 18E - 18H show structures which are the same as in Fig. 18A - 18D, except that an optional meltblown nonwoven intermediate layer is inserted between the multipurpose filter layer and the second filtration layer.

Fig. 18I - 18P show structures corresponding to Fig. 18A - 18H, respectively, except that an optional nonwoven scrim is added to the side of the vacuum filter bag facing the

exposed to airflow to protect the next layer from abrasion and filter out some of the largest dust particles.

Fig. 19Q-19AF show structures corresponding to Fig. 18A-18P, respectively, except that an optional spunbond nonwoven fabric is disposed at the most downstream layer position and is thus on the outside of the vacuum cleaner bag.

Fig. 20AG -20BL show structures corresponding to Fig. 18A-19AF, respectively, except that additional layers of the composition are bonded by a hot melt adhesive. The hot melt adhesive may be replaced by or used in conjunction with any known bonding methods, including glues and thermal and ultrasonic bonding. Although the figures only illustrate embodiments in which an adhesive is present between all adjacent layers, it is contemplated that not all layers need to be bonded in this manner, i.e., some layers of the composition will be bonded with adhesive and others will not.

47
Table Via

Example Comparison example 1 52 53 54 Comparison example 2 56 57 58 example 1 60 61 Layer/Composition 51 13 45 80 55 22 45 117 59 22 45 •"[Brain weight g/m ² 58 0.05 0.2 0.51 13 0.26 0.2 0.78 50 0.26 0.2 • ^: Quick mm 0.25 2100 400 225 0.05 480 400 255 0.32 480 400 :. _# Air permeability l/(m ² s) 330 >6.0 37 — 2100 2.8 37 — 2900 2.8 37 ::]2lignity MD N — >1.5 20 — >6.0 2.9 20 — 16 2.9 20 ^: .:.Tensile strength CD N — — 11,91- — >1.5 — 11,91- — 7 11,91- — ':'·. Pore diameter \sm — 64 16,52- 64 — 64 ..V." — 23.43 >300 23.43 23.43 ' ^: ..W ^p — 0.3 1.2 — 39.57 0.5 1.2 — 0.5 1.2 ^: ...M*BP bar — 0.3 0.7 "••■Filtration properties — — 100 — — 100 — — :***Flow l/min.
·· · ·* 100.0 — — 17.5 — — — 17.1 — — — !•"Pressure drop mmH20 10.4 — — 23.1 — — — 20.9 — — — Penetration % 72.7 — 76.9 — — 79.1 — ... ... Perfomance % 27.3

62 Example 2 64 Table VIb 67 Example 122 63 45 45 : * * Layer/Composition 1.14 77 0.2 65 Example 3 0.2 : Basis weight g/m ² 420 0.94 400 110 66 400 :. Thickness mm
► · · — 1850 37 1.11 65 37 _{: :} Air permeability l/(m ² s) — 6.1 20 330 0.91 20 :.:Tensile strength MD N — 5.4 11.91 -64 — 3000 11,91-64 ••.Tensile strength CD N — 23.43 — 5.8 23.43 •••Pore diameter μ&pgr;&eegr; — 1.2 — 5.2 1.2 :..MFP — — — ^: ..MBP cash 100 — — — — '"Pi'ltration properties 12.90 — — — — ^: ..Bjjss l/min. 66.90 — — 100 — !"Pressure drop mmH20 33.10 — — 10.20 — Penetration % 27,30 — Perfomance % 27.70 —

TableVll

Compare example 1 Compare Example 2 Example 1

Perfomance (%) 96.0 99.6 99.6 Air flow at 7.00 4.15 4.4 2 mbar (I) Dust load Pressure drop ( (G) 0 3.21 5.14 4.86 0.5 8.90 7.70 6.02 1.0 24.19 13.37 7.87 1.5 51.64 25.87 11.80 2.0 79.58 53.06 19.03 2.5 110,00 100.32 33.22 3.0 56.56 3.5 96.30 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.00

Example 2 Example 3 99.7 99.8 5.90 6.40

3.44 3.20 4.05 4.48 5.79 6.25 7.20 8.45 8.61 11.30 10.14 13.70 11.98 16,16 13.87 18.33 16.07 20.62 18.26 22.62 20.81 24.61 23.46 26.83 27.23 29.19 31.21 31.09 35.68 32.99 42.74 36,00 50.70 39.60 62.02 43.95 74.20 48.28 89.20 53.20 106.36 58.68

10.5 11.0 11.5 12.0 12.5 65.57 73.80 81.75 93.04 106.11

•34

G5006-06533/DM

List of reference symbols

1 clean page 2 Side exposed to airflow 3 Spunbond + meltblown, 80 g/m', 450 l/m'/s 10 Meltblown Bulky 120 g/m ² , 300-8000 l/m'/s 11 Meltblown 10-50 g/m', 100-1500 l/m'/s 12 Spunbond 10-40 g/m', 500-10000 l/m'/s 24 wet-laid support fleece, 10-30 g/m', 1000-2500 l/m'/s 25 wet filter paper 30-80 g/m', 200-500 l/m'/s 26 Meltblown 27 Spunbond 28 wet-laid support fleece 10-30 g/m', 1000-2500 l/m'/s 29 Meltblown 10-50 g/m', 100-1500 l/m'/s 30 wet filter paper 30-80 g/m', 200-500 l/m'/s 31 wet laid special filter paper 30-200 g/m', 500-8000 l/m'/s 32 Meltblown 10-50 g/m', 100-1500 l/m'/s 33 Spunbond 10-40 g/m', 500-10000 l/m'/s 34 dried special filter paper 30-200 g/m', 500-8000 l/m'/s 35 Meltblown 10-50 g/m', 100-1500 l/m'/s 36 Spunbond 10-40 g/m', 500-10000 l/m'/s 37 Spunbond 38 Meltblown 39 special filter paper, wet or dry laid 40 Spunbond 41 Meltblown 42 special filter paper, wet or dry laid 43 Support fleece 44 Spunbond 45 Meltblown 46 special filter paper, wet or dry laid

··

·

♦· · • · ♦ ·

47 Netting bonded with the special paper 48 Spunbond 49 Meltblown 50 Spunbond 51 special filter paper, wet or dry laid 52' wet-laid support fleece 10-30 g/m", 1000-2500 l/m"/s 53 Spunbond 53' wet filter paper 30-80 g/m", 200-500 l/m"/s 54 Hot melt 55 Meltblown 55' wet-laid support fleece 10-30 g/m", 1000-2500 l/m"/s 56 Hot melt 56' Meltblown 10-50 g/m", 100-1500 l/m"/s 57 special filter paper, wet or dry laid 57' wet filter paper 30-80 g/m", 200-500 l/m"/s 58 Spunbond 58" Vacuum cleaner bag structure 59 Hot melt 59' wet laid "capacity paper"; range: 30-150 g/m", 500-8000 l/m"/s,
preferred range: 50-80 g/m ² , 2000-4000 l/m ² /s 60 Meltblown 60' Meltblown; range: 10-50 g/m", 100-1500 l/m"/s 61 Hot melt 61' wet laid filter paper; range: 30-100 g/m", 100-3000 l/m"/s, before
Recommended range: 40-60 g/m ² , 500-1000 l/m ² /s 62 special filter paper, wet or dry laid 62' Vacuum cleaner bag structure 63 Hot melt 63' Latex bonded fluff pulp paper; range: 30-150 g/m", 500-8000
l/m ² /s, preferred range: 50-80 g/m ² , 2000-4000 l/m ² /s 64 Support fleece 64' wet laid filter paper; range: 30-100 g/m", 100-3000 l/m"/s, before
Recommended range: 40-60 g/m ² , 500-1000 l/m ² /s

· i· ·

65 Spunbond 65' Vacuum cleaner bag construction 66 Meltblown 66' thermally bonded split film fiber pulp filter paper; range: 30-150 g/m'',
500-8000 l/m ² /s, preferred range: 50-80 g/m ² , 2000-4000 l/m ² /s 67 Spunbond 67' wet laid filter paper; range: 30-100 g/m'', 100-3000 l/m^/s, before
Recommended range: 40-60 g/m ² , 500-1000 l/m ² /s 68 Hot melt 69 special filter paper, wet or dry laid 70 Spunbond 70' wet laid filter paper 71 Meltblown 71' special dried filter paper 72 Spunbond 72' wet laid filter paper 73 Hot melt 73' special electrostatic dried paper 74 special filter paper, wet or dry laid 74' wet laid filter paper 75 Hot melt 75' wet laid capacity filter paper 76 Support fleece 76' wet laid filter paper 77 Spunbond IT wet laid Tantret (TM) charged capacity filter paper 78 Meltblown 78' wet laid filter paper 79 Spunbond 79' Meltblown 80 Hot melt 80' special dried filter paper 81 special filter paper, wet or dry laid

81' wet laid filter paper 82 Netting adhesively bonded to the special filter paper 82" Meltblown 83 fleece 83' special electrostatic dried paper 84 carbon 84' wet laid filter paper 85 Meltblown 85" Meltblown 86 special filter paper, wet or dry laid 86' wet laid capacity filter paper 87 fleece 87' wet laid filter paper 88 carbon 88' Meltblown 89 Meltblown 89" wet laid Tantret (TM) charged capacity filter paper 90 special filter paper, wet or dry laid 90' wet laid filter paper 91 Support fleece 91' special dried filter paper 92 fleece 92' wet laid tantret loaded capacity paper 93 carbon 93' wet laid filter paper 94 Meltblown 94' special electrostatic dried paper 95 special filter paper, wet or dry laid 95' fleece 96 Netting adhesively bonded to the special filter paper 96' wet laid filter paper 97 fleece 97' wet laid capacity filter paper

98 carbon 98' fleece 99 Spunbond 99' wet laid filter paper 100 Meltblown 100' wet laid Tantret (TM) charged capacity filter paper 101 Spunbond 101' fleece 102 special filter paper, wet or dry laid 102' wet laid filter paper 103 fleece 103' Meltblown 104 carbon 104' special dried filter paper 105 Hot melt 105' fleece 106 Meltblown 106' wet laid filter paper 107 Hot melt 107' Meltblown 108 special filter paper, wet or dry laid 108' special electrostatic dried paper 109 fleece 109' fleece 110 carbon 110' wet laid filter paper 111 Hot melt 111' Meltblown 112 Meltblown 112' wet laid capacity filter paper 113 Hot melt 113' fleece 114 special filter paper, wet or dry laid

'..59

114" wet laid filter paper 115 Hot melt 115' Meltblown 116 Support fleece 116' wet laid Tantret (TM) charged capacity filter paper 117 fleece 117" fleece 118 carbon 118' Spunbond 119 Hot melt 119' special dried filter paper 120 Spunbond 120' Spunbond 121 Meltblown 121' special electrostatic dried filter paper 122 Spunbond 122' Spunbond 123 Hot melt 123' wet laid capacity filter paper 124 special filter paper, wet or dry laid 124' Spunbond 125 fleece 125' wet laid Tantret (TM) charged capacity filter paper 126 carbon 126' Spunbond 127 Hot melt 127' Meltblown 128 Spunbond 128' special dried filter paper 129 Meltblown 129' Spunbond 130 Spunbond 130' Meltblown

131 Hot melt 131' special electrostatic dried paper 132 special filter paper, wet or dry laid 132" Spunbond 133 Hot melt 133' Meltblown 134 Support fleece 134" wet laid capacity filter paper 135 fleece 135' Spunbond 136 carbon 136' Meltblown 137 Hot melt 137' wet laid Tantret (TM) charged capacity filter paper 138 Spunbond 138' Spunbond 139 Hot melt 139' special dried filter paper 140 Meltblown 140' fleece 141 Hot melt 141' Spunbond 142 special filter paper, wet or dry laid 142' special electrostatic dried paper 143 Netting adhesively bonded to the special filter paper 143' fleece 144 Spunbond 144' Spunbond 145 Meltblown 145' wet laid capacity filter paper 146 carbon 146' fleece 147 fleece

• ?·? φφφ

?·? φ φφ φ«

• · φ · φ · φ

• φ φ φφφ # · ·

• φ · · φ φ

147" Spunbond 148 special filter paper, wet or dry laid 148' wet laid Tantret (TM) charged capacity filter paper 149 Spunbond 149' special dried filter paper 150 Meltblown 150' Spunbond 151 carbon 151' Meltblown 152 fleece 152" special dried filter paper 153 special filter paper, wet or dry laid 153' fleece 154 Support fleece 154' Spunbond 155 Spunbond 155' Meltblown 156 Meltblown 156' special electrostatic dried paper 157 carbon 157' fleece 158 fleece 158" Spunbond 159 special filter paper, wet or dry laid 159' Meltblown 160 Netting adhesively bonded to the special filter paper 160' wet laid capacity filter paper 161 Spunbond 161' fleece 162 Meltblown 162' Spunbond 163 Spunbond 163' Meltblown

164 carbon 164' wet laid Tantret (TM) charged capacity filter paper 165 fleece 165' fleece 166 special filter paper, wet or dry laid 166' wet laid filter paper 167' Hot melt 168' special dried filter paper 169 Spunbond 169' wet laid filter paper 170 Hot melt 170' Hot melt 171 Meltblown 171' special electrostatic dried paper 172 Hot melt 172' wet laid filter paper 173 carbon 173' Meltblown 174 fleece 174' special dried filter paper 175 Hot melt 175' wet laid filter paper 176 special filter paper, wet or dry laid 176' Hot melt 177 Spunbond 177' Hot melt 178 Hot melt 178' wet laid filter paper 179 Meltblown 179' Meltblown 180 Hot melt 180' Hot melt 181 carbon

·

·

·

181' special dried filter paper 182 fleece 183 Hot melt 183' wet laid filter paper 184 special filter paper, wet or dry laid 184' Hot melt 185 Hot melt 185' Meltblown 186 Support fleece 186' Hot melt 187 Spunbond 187' special electrostatic dry gelled paper 188 Hot melt 188' wet laid filter paper 189 Meltblown 189' Hot melt 190 Hot melt 190' Meltblown 191 carbon 191' Hot melt 192 fleece 192' wet laid capacity filter paper 193 Hot melt 193" wet laid filter paper 194 special filter paper, wet or dry laid 194' Hot melt 195 Spunbond 195' Meltblown 196 Meltblown 196' Hot melt 197 Spunbond 197" wet laid Tantret (TM) charged capacity filter paper 198 Hot melt

198' wet laid filter paper 199 carbon 199' Hot melt 200 fleece 200' special dried filter paper 201 Hot melt 201' Hot melt 202 special filter paper, wet or dry laid 202" fleece 203 Hot melt 203' wet laid filter paper 204 Support fleece 204' Hot melt 205 Spunbond 205' special electrostatic dried paper 206 Meltblown 206' Hot melt 207 Spunbond 207' fleece 208 Hot melt 208' wet laid filter paper 209 carbon 209" Hot melt 210 fleece 210' wet laid capacity filter paper 211 Hot melt 211' Hot melt 212 special filter paper, wet or dry laid 212' fleece 213 Netting adhesively bonded to the special filter paper 213' wet laid filter paper 214 Fleece 15-100 g/m", 200-5000 l/m^/s 214' Hot melt

215 Carbon 25-400 g/m', 500-3000 l/m'/s 215' wet laid Tantret (TM) charged capacity filter paper 216 Meltblown 10-50 g/m', 100-1500 l/m'/s 216' Hot melt 217 wet laid special filter paper 30-200 g/m', 500-8000 l/m'/s 217' fleece 218" wet laid filter paper 219' Hot melt 220' Meltblown 221' Hot melt 222' special dried filter paper 223' Hot melt 224' fleece 225' wet laid filter paper 226' Hot melt 227' Meltblown 228' Hot melt 229' special electrostatic dried paper 230' Hot melt 231' fleece 232' wet laid filter paper 233' Hot melt 234' Meltblown 235' Hot melt 236' wet laid capacity filter paper 237' Hot melt 238' fleece 239' wet laid filter paper 240' Hot melt 241' Meltblown 242' Hot melt 243' wet laid Tantret (TM) charged capacity filter paper 244' Hot melt

*66*

245' fleece 246" Spunbond 247" Hot melt 248' special dried filter paper 249" Spunbond 250' Hot melt 251' special electrostatic dried paper 252' Spunbond 253' Meltblown 254" wet laid capacity filter paper 255' Spunbond 256" Hot melt 257' wet laid Tantret (TM) charged capacity filter paper 258' Spunbond 259' Hot melt 260' Meltblown 261' Hot melt 262' special dried filter paper 263' Spunbond 264' Hot melt 265' Meltblown 266' Hot melt 267' special electrostatic dried paper 268' Spunbond 269' Hot melt 270' Meltblown 271' Hot melt 272' wet laid capacity filter paper 273' Spunbond 274' Hot melt 275' Meltblown 276' Hot melt TlT wet laid Tantret (TM) charged capacity filter paper

278" Spunbond 279' Hot melt 280' special dried filter paper 281' Hot melt 282' fleece 283' Spunbond 284' Hot melt 285' special electrostatic dried paper 286' Hot melt 287' fleece 288' Spunbond 289' Hot melt 290' wet laid capacity filter paper 291' Hot melt 292' fleece 293' Spunbond 294" Hot melt 295' wet laid Tantret (TM) charged capacity filter paper 296' Hot melt 297' fleece 298' Spunbond 299' Hot melt 300' Meltblown 301' Hot melt 302' special dried filter paper 303' Hot melt 304' fleece 305' Spunbond 306' Hot melt 307' Meltblown 308' Hot melt 309' special electrostatic dried paper 310' Hot melt

■ ····&igr;

•68 '

311' fleece 312" Spunbond 313' Hot melt 314' Meltblown 315" Hot melt 316' wet laid capacity filter paper 317' Hot melt 318' fleece 319' Spunbond 320' Hot melt 321' Meltblown 322' Hot melt 323' wet laid Tantret (TM) charged capacity filter paper 324' Hot melt 325' fleece 326" wet laid Tantret (TM) charged capacity filter paper

Claims (22)

1. A filter for removing particles entrained by a gas, comprising a multi-purpose filtration capacity layer arranged upstream in the direction of the air flow of a second filtration layer,
wherein the second filtration layer is selected from: a) a wet-laid or dry-laid filter with a surface weight of approximately 30-100 g/m ² and an air permeability of approximately 100-3000 l/(m ² s) and b) a thermally bonded nonwoven with a basis weight of approximately 10-100 g/m ² and an air permeability of approximately 100-3000 l/(m ² s), and wherein the multi-purpose filtration capacity layer is selected from: (a) a wet-laid or dry-laid paper with high dust capacity with a basis weight of approximately 30-150 g/m ² and an air permeability of approximately 500-8000 l/(m ² s); b) a high-volume meltblown nonwoven with a basis weight of approximately 30-180 g/m ² and an air permeability of approximately 300-1500 l/(m ² s); and c) a (modular) spunblown nonwoven with a basis weight of approximately 20-150 g/m ² and an air permeability of approximately 200-3000 l/(m ² s). 2. A filter according to claim 1, wherein the multi-purpose filtration layer is effective to provide a pressure drop for the filter of at most 30 mbar at a fine dust particle loading of at least 6.5 g, determined according to DIN 44956-2. 3. A filter according to claim 1, wherein the wet-laid high dust capacity paper comprises fibers having at least 15% chargeable or non-chargeable synthetic fibers and a complementary amount of wood pulp fibers and a binder. 4. A filter according to claim 3, wherein the synthetic fibers are polyester. 5. The filter of claim 3, wherein the synthetic fibers are polyolefin fibers. 6. The filter of claim 5, wherein the polyolefin fibers are electrostatically charged polypropylene. 7. The filter of claim 1, wherein the multipurpose filtration layer comprises a high dust capacity dry laid paper of a composition selected from (a) latex bonded fluff pulp fibers, (b) thermally bondable melt fibers, (c) a thermally bonded blend of thermally bondable polymer melt fibers and fluff pulp fibers, (d) a thermally bonded blend of thermally bondable melt fibers, fluff pulp fibers and split film fibers, (e) a thermally bonded blend of mixed electrostatic fibers. 8. The filter of claim 7, wherein the thermally bondable melt fibers are bicomponent polymer fibers. 9. The filter of claim 8, wherein the bicomponent polymer fibers are polyolefin. 10. The filter of claim 9, wherein the bicomponent polymer fibers have a core of polypropylene and a sheath of polyethylene. 11. The filter of claim 8, wherein the bicomponent polymer fibers have a core disposed eccentrically with respect to a sheath. 12. A filter according to claim 11, wherein the core is arranged alongside the shell. 13. The filter of claim 7, wherein the split film fibers are electrostatically charged. 14. The filter of claim 1, further comprising a meltblown nonwoven layer having a basis weight of about 10-50 g/m ² and an air permeability of about 100-1500 l/(m ² s) disposed between the multipurpose filtration layer and the second filtration layer. 15. The filter of claim 14, wherein the meltblown nonwoven layer is electrostatically charged. 16. The filter of claim 1, wherein the thermally bonded nonwoven is the downstream most layer of the structure. 17. The filter of claim 1, wherein at least two adjacent layers of the structure are bonded. 18. The filter of claim 17, wherein the two bonded adjacent layers are the multipurpose filtration layer and the second filtration layer. 19. The filter of claim 17, wherein all adjacent layers of the structure are bonded. 20. The filter of claim 1, wherein the high-bulk meltblown nonwoven is electrostatically charged. 21. The filter of claim 1, wherein at least one of the layers is made of a chargeable material and the chargeable layer is electrostatically charged. 22. Disposable vacuum cleaner bag comprising a filter according to any one of claims 1 to 21.