EP1126065B1 - Single-layered double side abrasive web and method of manufacture - Google Patents

Abstract

Single-layer non-woven fabric which is abrasive on both sides has a basis weight of 15-150 g/m<2> and contains a uniform mixture of: (A) micro-fibres with a diameter of 1-10 microns; and (B) macro-fibres with a diameter of 15-50 microns. An Independent claim is also included for a melt-blown process for the production of abrasive non-woven fabric by feeding a mixture of polymers with different properties and optional additives into an extruder, extruding the mixture at an outlet temperature of 180-300 degrees C, spinning the extrudate through dies and laying down the spun fibres on a collector.

Description

The invention relates to a single-layer abrasive nonwoven fabric, a process for producing the same and the use of such a single-layer abrasive nonwoven fabric. The nonwoven according to the invention exhibits improved properties in terms of abrasiveness, memory behavior and the variation of its properties in comparison to the nonwovens of the prior art with simple production.

State of the art

The meltblown technology is deposited in the Naval Research Report (NRL 4364 and 5265). The application of the results and extension to applications in the nonwovens sector are described in various patent specifications (cf., for example US-A-3 615 995 . 3,676,242 . 3,849,241 . 4 000 967 . 3 704198 and 3,841,953 ).

In the meltblown process (cf. FIG. 1 ), the dried polymer granules are transported from the storage container (12) into an extruder (13) in which it is heated and melted to the required temperature, which is necessary for fiber formation and depends on the particular polymer. The molten polymer then reaches the meltblown nozzle (14). This has a large number of small openings. Through these openings, the polymer flows and is thereby formed depending on the hole diameter into fibers. The fibers (15) are detected directly below the nozzle of a strong air flow, torn into different lengths and placed on a suction roll (17). The diameter of the fibers is about 0.3 to 20.0 microns depending on the polymer used and other polymer and process parameters. The still warm fibers merge into a fleece. The filing takes place in different statistically distributed lengths, thicknesses and directions. Subsequently, the now cooled material is rolled up on a winder (18).

Nonwovens produced by this technology can be characterized by their softness, high absorbency, good air permeability and low resistance to abrasion. Typical fields of application of such meltblown nonwovens are, for example, filter media, wipes or oil absorption materials.

Lamers et al. describe in the US-A-4,659,609 an abrasive fabric and a method of making the same. The abrasive fabric described in this patent is a two-ply nonwoven consisting of a backing layer and an abrasive meltblown layer which have been thermally bonded together. The basis weight of the abrasive meltblown layer is reported as being between 5 and 25 g / m ² , the average fiber diameter of the meltblown layer forming fibers being at least 40 μm. As a carrier layer, a spunbonded polypropylene is normally used. In this case, the strength and elongation necessary for the use of the fabric produced and, moreover, the absorption capacity for a tanning solution are provided by the carrier layer. The function of the meltblown layer of the web described in this patent is limited only to the provision of rough fibers. A particular embodiment of this invention is a three-layer abrasive cloth (meltblown layer / spunbond / meltblown layer) in which both outer surfaces consist of an abrasive meltblown layer.

To improve the particularly important for wipes Tränkespeicherungsvermögens is in the US-A-4 833 003 each a meltblown layer of microfibers and macrofibers thermally connected. The disadvantage of this method is the production costs for the production of two layers and their connection, for example via hot calendering. For the on-line production of such articles either a second nozzle bar with extruder or a second extruder with a special nozzle bar is necessary, wherein the nozzle bar has two separate feeders which feed separate nozzles.

The in the US-A-4,833,003 (Win et al. ) described possibility of drinking intake is in the US-A-5,817,585 and EP-A-0 615 720 extended. In both patents special fluids are added to such nonwovens and their use for hand cleaning and color cleaning described.

The WO 97/21865 (Annis et al. ) describes a wet mat which has in a single layer a surface abrasive layer produced by thermal coagulation of thermoplastic fibers. Disadvantage of this method is the insufficient strength in the Stress, as well as the observed gradient of the melt fibers. Therefore, this wet fleece shows only on one side an abrasive effect.

The DE 24 38 918 A1 describes a process for making nonwoven fibrous webs from thermoplastic polymers by meltblowing the polymer to form fibers and combining the fibers into a mat characterized by introducing into the mat fibrous elements of relatively fine dimension and fibrous elements of relatively large size.

Description of the invention

The methods described so far are expensive to produce, either as a result of the multiple layers, although they are constructed solely from polypropylene (homopolymers), or they have serious disadvantages due to poor physical strengths.

It is therefore an object of the present invention to provide a single-layer nonwoven which combines good abrasive properties on both sides, good retention behavior, good strength and elongation properties with simple production.

This object is achieved by a single-layer abrasive nonwoven according to claim 1. Further preferred embodiments are described in the dependent claims 2 to 7.

The present invention furthermore relates to a process for producing such a single-layer, abrasive nonwoven according to claim 8. Preferred embodiments of this process are described in subclaim 9.

Description of the figures

• Fig. 1 shows in a schematic description the components of a meltblown process;
• Fig. 2 shows the pore size distribution in an inventive abrasive fleece, which was prepared according to Example 2; and
• Fig. 3 shows the Tränkespeichervermögen an inventive abrasive fleece, which was prepared according to Example 2.

According to the invention, it has surprisingly been found that it is possible by production in the context of a meltblown process in one step with only one extruder for the polymers used and with only one nozzle bar having only spinnerets one size, by using a mixture of polymers of different melt indices a single-layer, both sides abrasive nonwoven, which has a uniform mixture of microfibers of a fiber diameter of 1 to 10 microns and macrofibres of a fiber diameter of 15 to 50 microns to get.

For example, it has been found according to the invention that by using a suitable mixture of polymers of different melt indices it is possible to produce a single-layer abrasive nonwoven having abrasions defined in a wide range and defined impregnation and retention behavior.

The same applies when mixtures of polymers of different molecular structure (i.e., linear, branched, crosslinked, random copolymer, block polymer, etc.), different molecular weight and / or molecular weight distribution, and at least two polymers that are immiscible with each other are used.

According to a preferred embodiment, according to the invention, single-ply abrasive nonwovens can be produced in which the phenomenon of subsequent embrittlement of thick meltblown fibers is further improved by using further polymers and, if appropriate, additives and, if desired, higher strength and elongation values are achieved.

These other polymers may be, for example, polyethylene, polyethylene / polypropylene copolymer or a polypropylene block polymer in a proportion (usually 30% or less, based on the polypropylene block polymer) of a rubbery phase consisting of equal parts of ethylene and propylene ,

These polymers are usually added to the mixtures in amounts of from 0.1 to 20% by weight, preferably from 0.2 to 10% by weight, in particular from 0.5 to 8% by weight, based in each case on the weight of the entire mixture, added.

As additives in these cases, surfactants, such as alkylbenzenesulfonates, alkanesulfonates, fatty alcohol sulfonates, fatty alcohol ether sulfates, α-olefin sulfonates, α-ester sulfonates, Alkyl phosphates, alkyl ether phosphates, fur alcohol ethoxylates, alkyl phenol ethoxylates, fatty amine ethoxylates, fatty acid ethoxylates, fatty acid ester ethoxylates, alkoxylates, alkanolamides, sugar surfactants, amine oxides, cationic surfactants and amphoteric surfactants, especially nonionic fluorocarbon surfactants, and / or primary and secondary antioxidants such as hindered phenols, sulfides, polysulfides, dithiocarbamates , Phosphites, phosphonites, diphosphonites, and phosphonates.

The additives are usually added to the mixtures in amounts of from 0.01 to 15% by weight, preferably from 0.01 to 10% by weight, in particular in amounts of from 0.1 to 5% by weight, based in each case on the weight of entire mixture, added.

The additives and / or polymers may be blended into the blends prior to entry into the extruder or the individual ingredients (i.e., the various polymers) may be added to the extruder as individual ingredients along with the additives. The additives can also be sprayed onto the fibers after the spinning process.

It is known to the person skilled in the art that, by suitable selection and adjustment of the determining production parameters in the meltblown process, it is possible to intentionally spin out thick or thin fibers.

Important process parameters in this context are the following: extruder temperature, melt temperature, jet bar temperature, melt flow rate and pressure, air temperature, air flow, nozzle bar design, collector bar spacing, collector negative pressure, collector speed, basis weight of the resulting bar Fleece and treatment with aerosolized water, optionally containing additives.

In order to be able to produce the abrasive nonwoven according to the invention, it is additionally necessary to simultaneously spin out thick and thin fibers by the choice of suitable polymer parameters, by the selection of suitable polymer types and optionally the polymer blend and optionally by the use of certain additives.

Important parameters in this context are e.g. the melt index of the polymer, the molecular structure (i.e., linear, branched, crosslinked, random copolymer, block polymer, etc.), molecular weight, and / or molecular weight distribution.

The so-called melt index (MFI or MFR) is a measure of the melt viscosity at a specified temperature of thermoplastic polymers and indicates the amount of material that passes through a defined nozzle in 10 minutes under the action of a given force at a specified temperature. Thus, MFI is also a rough indicator of molecular weight and molecular weight distribution. However, Bugada points in her Review "Optimizing polymer properties for process and product performance", published in Nonwovens World, August-September 1999, p. 89ff suggest that at nearly the same MFIs, the molecular weight can vary significantly and vice versa.

It has been found that fiber properties can be additionally controlled individually by mixing polymers of different melt indices. In order to produce a mixture of microfibers and macrofibres according to the above definition simultaneously with an extruder and a die bar, it is therefore necessary to melt polymers of, for example, different melt indices, different molecular structure, different molecular weight and optionally different molecular weight distribution in the extruder, without a resulting uniform viscosity sets. It must be ensured that the two viscosities remain substantially without equalization.

In one embodiment of the present invention, the starting materials used are polymers which are already predegraded. When polymers containing peroxide compounds are used as constituents of the mixture to be used in the present invention, in some cases, a tendency for viscosity adjustment can be observed.

In principle, the polymers which can be used according to the invention are the various types of polyolefins, polyesters, polyamides, polyesteramides and copolymers thereof, for example polyethylene, polypropylene, polybutylene, nylon, ethylene / vinyl acetate copolymers, ethylene / propylene copolymers or polyvinyl chloride. The polymers mentioned can be extruded either as a homopolymer or as a mixture of different polymers (copolymers).

• eine Mischung mindestens zweier Homopolymere z.B. aus Polyolefinen wie Polypropylen (PP) oder Polyethylen (PE) oder Gemische zweier Polyethylen- oder Polypropylenhomopolymere unterschiedlicher Schmelzindizes,
• eine Mischung aus mindestens einem Homopolymer und mindestens einem Copolymer bzw.
  Terpolymer, z.B. ein Gemisch aus Polypropylen und einem Polypropylen/Polyethylen-Copolymer.
• eine Mischung aus mindestens zwei Copolymeren bzw. Terpolymeren, z.B. ein Gemisch aus einem Polypropylen/Polyethylen-Copolymer und einem Ethylent/Vinylacetat-Copolymer oder ein Gemisch aus zwei Polypropylen/Polyethylen-Copolymeren unterschiedlicher Schmelzindizes.

For example, the polymers which can be used to produce the abrasive nonwoven fabric according to the invention may be, for example, the following:

• a mixture of at least two homopolymers, for example of polyolefins such as polypropylene (PP) or polyethylene (PE) or mixtures of two polyethylene or polypropylene homopolymers of different melt indices,
• a mixture of at least one homopolymer and at least one copolymer or
  Terpolymer, for example a mixture of polypropylene and a polypropylene / polyethylene copolymer.
• a mixture of at least two copolymers or terpolymers, for example a mixture of a polypropylene / polyethylene copolymer and an ethylene / vinyl acetate copolymer or a mixture of two polypropylene / polyethylene copolymers of different melt indices.

Examples of mixtures preferably used according to the invention are a mixture of polypropylene having a melt index of 450 and a polypropylene block polymer having a melt index of 100 and a mixture of peroxidically degraded polypropylene having a melt index of 1400 and a polypropylene block polymer having a melt index of 100.

According to the invention, polymers having a melt flow rate (MFR) in a range between 50 and 1600 g / 10 min, preferably in a range of 100 to 1400 g / 10 min, are used, the mixing ratios of the polymers being in a range of 5-40% / 95-60%, each may be varied based on a mixture of lower melt index polymer / higher melt index polymer.

The melt indices of the polymers used according to the invention, when the parameter melt index is selected to simultaneously spin thick and thin fibers by the meltblown process, according to the invention have a difference of at least 50 units (g / 10 min), preferably 100 units and especially 300 Units.

The weight-average molecular weight Mw of the polymers usable in the present invention is preferably in a range of 50,000 and 200,000 g / mol, more preferably in a range of 70,000 to 150,000 g / mol.

In addition to roughness and retention capacity, the physical properties such as breaking strength and elongation at break are particularly important for an abrasive nonwoven. By appropriate selection of the polymer mixture, e.g. by using a polyethylene / polypropylene copolymer, especially one having a polyethylene content of not more than 20%, the ethylene being in a rubbery phase, these properties of the polypropylene can be greatly improved.

Widely known and applicable for such cases are mixtures of polypropylene with its related polymers from the family of polyolefins and especially with polyethylene. Noel and Carley describe in theirs Essay "Properties of Polypropylene-Polyethylene Blends", Polymer Engineering, Science, February 1975, Vol. 2, p. 117ff the breaking force-increasing addition of up to 10% polyethylene to a polypropylene. However, such fibers typically become very soft, counteracting the desired abrasive effect of the web. Such soft fibers also occur when using polypropylene / polyethylene copolymers which are polymerized from ethylene and propylene (cf., for example, US Pat PCT / WO 98/39384 ).

Surprisingly, embrittlement of the nonwovens according to the invention combined with excellent abrasiveness in a preferred embodiment can be suppressed by using a copolymer in which the polyethylene is present only in a rubber phase as the one polymer constituent of the mixture the elongation at break is greatly increased (greater than 20%). A copolymer which can be used in this context is, for example, a commercially available polypropylene block polymer with a low rubber phase, which consists of about 50% each of ethylene and propylene.

The fiber thickness of the microfibers is according to the invention in a range of 1 to 10 microns, preferably in a range of 2 to 8 microns, and in particular in a range of 3 to 7 microns. The fiber thickness of the macrofibers is according to the invention in a range of 15 to 80 microns, preferably in a range of 20 to 60 microns, and in particular in a range of 30 to 50 microns.

At present we assume that the numerical proportion of the macrofibers in the nonwoven according to the invention, based on an areal unit of the nonwoven, is desirably less than 50%, in particular less than 40%.

When spinning out the polymer mixture, a part of the sticky micro- or macrofibers formed on the collector in the web formation may also stick together with adjacent fibers, so that in addition to the micro and macrofibres also thicker fiber bundles may be present in the nonwoven fabric according to the invention. Without wishing to be bound by any theory, we believe that the formation of fiber bundles can be achieved by using polymers with more similar properties, i. For example, polymers with low different melt indices, is favored. Further, we believe that the formation of fiber bundles is promoted by the co-use of a copolymer, for example, the above-mentioned copolymer in which the ethylene is present only in the rubber phase. The thickness of these fiber bundles may in such cases usually be between 50 and 300 μm, preferably between 70 and 200 μm, in particular between 80 and 150 μm.

At present we assume that in order to improve the abrasive properties of the web according to the invention a quantitative proportion of more than 10% of the total fibers on fiber bundles is desirable.

For example, such a process can be observed particularly in cases where a blend of a higher melt index polypropylene and a copolymer with a lower melt index, for example, less than 25% of the melt index of the polypropylene used is used.

When using polymer blends with very different melt indices, both of which usually contain little or no residual peroxide, it does not come to the adjustment of the viscosities, but two differently viscous, slightly mixed melts, so that the formation of fiber bundles occurs to a lesser extent and statistically distributed over the entire nozzle bar takes place. Thick fiber bundles as well as macro and microfibers are thus distributed randomly in the x, y and z directions in the nonwoven.

• Hydrophilierungsmittel, beispielsweise die oben genannten nichtionischen Tenside, insbesondere Sulfobernsteinsäureesterderivate oder fluorchemische-Tenside;
• Stabilisatoren gegen oxidative Degradation (bspw. durch Restperoxid, (Luft-)Sauerstoff, (Sonnen-)Licht, Wasser etc.), wie Amine, Phenole, Phosphite, Phosphonite, Diphosphonite oder Thioester, und
• Farbstoffe zur Färbung der Fasern, wie sie besipielsweise von der Fa. Clariant unter der Bezeichnung Sanylene® vertrieben werden.

The polymer mixtures according to the invention may further be admixed with additives which may contribute to providing or maintaining specific nonwoven properties. Examples of additives which can be used according to the invention are the following:

• Hydrophilizing agents, for example the abovementioned nonionic surfactants, in particular sulfosuccinic ester derivatives or fluorochemical surfactants;
• Stabilizers against oxidative degradation (for example by residual peroxide, (air) oxygen, (sun) light, water, etc.), such as amines, phenols, phosphites, phosphonites, diphosphonites or thioesters, and
• Dyes for dyeing the fibers, as sold, for example, by Clariant under the name Sanylene®.

These additives may contain the polymer mixtures used according to the invention in amounts of from 0.01 to 15% by weight, preferably in amounts of from 0.01 to 10% by weight, in particular from 0.1 to 5% by weight, based in each case on Weight of the polymer mixture to be added.

• Flächengewicht (EDANA-Norm 403 89),
• Bruchkraft und Bruchdehnung (EDANA-Norm 20289),
• Möglichst niedrige Versprödungsneigung,
• Abrasivität,
• Widerstand gegen Fusseln und Abrasion,
• Tränkehaltevermögen,
• Tränkeaufnahme,
• Faserdurchmesser,
• Porengröße und Porengrößenverteilung,
• Kontaktwinkel.

The monolayer abrasive webs produced according to the invention can be described by the following parameters:

• Basis weight (EDANA standard 403 89),
• Breaking strength and elongation at break (EDANA standard 20289),
• Lowest embrittlement tendency,
• abrasiveness,
• Resistance to lint and abrasion,
• Potions perseverance,
• Potions Up,
• Fiber diameter,
• Pore size and pore size distribution,
• Contact angle.

The abrasive web of the invention usually has a basis weight of 15 to 150 g / m ² , preferably a basis weight of 25 to 80 g / m ² .

Surprisingly, breaking strength and elongation at break of pure polyolefin products deteriorate significantly after production. This behavior has been improved by the use of the polymer mixtures according to the invention to the extent that the ultimate breaking strength of the abrasive web of the invention is usually at least 10 N / 50 mm, preferably at least 15 N / 50 mm, and cross-machine direction (CD) in the machine direction (MD). usually at least 5 N / 50mm, preferably 10 N / 50 mm.

The elongation at break of the abrasive web of the invention is usually over 10%, preferably over 20% in both MD and CD. The elongation at break improves when the fleece is moistened with the potion.

The water retention capacity as well as the water absorption are strongly determined by the fiber diameter, the resulting pore size distribution, the fleece density and the surface chemical properties of the nonwoven.

To determine the intake of drinking water, usually a defined area is dry-weighed, then soaked with a test pot, lightly expressed and weighed wet. The weight of the taken potions, which is calculated from the difference between the two measured values, is set in relation to the weight per unit area and indicates the drinking intake in percent. The impregnation receptacle of the abrasive nonwoven according to the invention is usually between 100 and 700 dry weight percent, preferably between 100 and 500 dry weight percent.

The fiber diameter of the fibers occurring in the abrasive nonwoven fabric according to the invention can be determined by scanning electron microscopic (SEM) examination.

The pore size can be determined by means of a Porosimerters, which presses mercury with increasing pressure in the nonwoven pores. From the pressure curve, the number of pores, pore size distribution and the total pore volume can be derived. Good impregnation storage has been achieved in nonwovens according to the invention, in which the pore volume fraction of pores smaller than 60 μm in diameter is usually more than 50%, preferably more than 70%. FIG. 2 shows a pore size distribution of an inventive abrasive nonwoven according to the following Example 2.

The water retention capacity is confirmed by a storage test. In this case, several stacks of 30 individual sheets of an abrasive nonwoven according to the invention are moistened according to the following example 2 with a certain amount of a defined potions. Then, from the leaves of a stack, the absorbed potion quantity is determined, which leads to a potion profile within the stack. Further, further stacks of the like of the invention are stored in a sealed package for one month at room temperature and at 40 ° C. Subsequently, as in the first stack, the drinking profile is measured in the stacks (cf. FIG. 3 ).

The two profiles of the stored stack run almost horizontally only with a very small pitch and remain parallel. The downward shift of the curves indicates the evaporation of the potions through the sealed packing, especially at 40 ° C. The topmost leaves in the stack slightly lose potions and give them to the bottom leaves. These can save the extra amount easily, the pack remains dry. The potions stably shifts to the observed state, since the slightest change is observed already at the first measurement, which was carried out a few days after production.

The abrasive nonwoven according to the invention can therefore be stored evenly over a long period in a package moist throughout the stack without the overhead wipes dry out while accumulated at the bottom of the pack out of the wipes drained potions. This could be achieved by the abrasive nonwoven according to the invention.

The nonwoven according to the invention can, as stated above, according to the meltblown process, be produced in one step with only one extruder for the polymers used and with only one nozzle beam having only spinnerets of one size, by using a mixture of polymers of different properties.

In this case, the polymers used and optionally used additives in the desired mixing ratio from a metering device can be entered into the extruder. There, the mixture becomes a suitable temperature profile (this is known to those skilled in the art or readily determined by routine experimentation) and typically exits the extruder at a temperature between 180 and 300 ° C. A pump transports the melt to the nozzle bar at a rate that is typically at least 50 kg / hr. The distance between collector and nozzle bar is usually between 25 and 50 cm. The speed of the collector depends on the desired weight per unit area of the fleece for a given throughput of the melt and given width of the nozzle bar used. The temperature of the commonly used hot compressed air is usually between 270 and 320 ° C depending on the polymer mixture used and optionally added additives. The air flow rate varies as well as the air temperature, depending on the polymer mixture used and optionally added additives between 250 and 500m ³ / h.

Due to the properties described here, the abrasive nonwoven according to the invention is particularly suitable for

Cleaning of soiled surfaces e.g. for hand cleaning, for cleaning baths and toilets, for cleaning surfaces that are dirty with graffiti etc.

For the following examples, a meltblown line with only one extruder was used, so that all polymers and optionally used additives were melted together in an extruder and spun through a die bar.

example 1

An abrasive non-woven with a basis weight of 45 g / m ² was prepared from a mixture of 80% isotactic polypropylene, containing no residual peroxide and has a melt index of 450 g / 10 min, and 20% polypropylene block polymer with a 10% rubbery phase from Polyethylene / polypropylene = 50/50 with a melt index of 100 g / 10 min at 233 ° C melt temperature. The resulting breaking force is 22 N / 50mm in the machine direction and 12 N / 50mm across the machine direction. The elongation at break is almost 50% in the machine direction and just over 50% across the machine direction.

Example 2

An abrasive web having a basis weight of 45 g / m ² was made from a blend of 80% isotactic polypropylene containing no residual peroxide and having a melt index of 450 g / 10 min and 20% polypropylene block polymer as in Example 1 was used, at 233 ° C temperature of the melt prepared (see Example 1). A hydrophilizing agent (a commercial nonionic fluorochemical surfactant) was sprayed onto the fibers in an amount of ... after the spinning process. The achieved breaking force is 17 N / 50mm in the machine direction and 13 N / 50mm across the machine direction. The elongation at break is just under 45% in the machine direction and over 70% across the machine direction.

Example 3

An abrasive web having a basis weight of 45 g / m ² was made from a blend of 79% isotactic polypropylene containing no residual peroxide and having a melt index of 450 g / 10 min, 20% polypropylene block polymer having a 10% rubber phase and a melt index of 100 g / 10 min (as described in Example 1) and 1% of a hydrophilizing agent consisting of a commercial nonionic fluorochemical surfactant, prepared at 233 ° C melt temperature. The achieved breaking force is 18 N / 50 mm in the machine direction and 13 N / 50 mm across the machine direction. The elongation at break is almost 80% in the machine direction and over 90% across the machine direction.

Examples 1 to 3 show that the addition of hydrophilizing agents positively affects the elongation at break. At the same time, they lower the surface energy of the nonwoven and allow improved water retention.

Example 4

An abrasive web having a basis weight of 47.5 g / m ² was made from a blend of 80% isotactic polypropylene containing peroxide and having a melt index of 1400 g / 10 min and 20% polypropylene block polymer having a 10% rubber phase a melt index of 100 g / 10 min (see Example 1) at 233 ° C temperature of the melt produced. A commercially available nonionic fluorochemical surfactant was sprayed onto the fibers in an amount of ... after the spinning process. The achieved breaking force is 17 N / 50mm in the machine direction and 14 N / 50mm across the machine direction. The elongation at break is just under 45% in the machine direction and over 35% across the machine direction.

Despite an increase in the basis weight and despite the positive effect of the hydrophilizing agent on the elongation at break, a somewhat lower elongation at break is obtained transversely to the machine direction.

Comparative Example 1

An abrasive web having a basis weight of 39 g / m ² was prepared according to the prior art from an isotactic polypropylene having a melt index of 450 g / 10 min at 253 ° C melt temperature. A commercially available nonionic fluorochemical surfactant was sprayed onto the fibers in an amount of ... after the spinning process. The achieved breaking force is 13.5 N / 50 mm in the machine direction and 10 N / 50 mm in the cross-machine direction. The elongation at break is just under 20% in the machine direction and over 30% across the machine direction.

The following table summarizes the examples: Table 1 Ex. Or Comp. Ex. Basic wt. hydrophilic breaking force elongation composition MD CD MD CD Example 1 80% PP 450 MFR + 45 22 12 50 50 20% PP block polymer 100 MFR Ex. 2 80% PP 450 MFR + 45 X 17 13 45 70 20% PP block polymer 100 MFR Example 3 79% PP 450 MFR + 45 X 18 13 80 90 20% PP block polymer 100 MFR + 1% fluorochemical Hydrophilic EX4 80% PP 1,400 MFR (Peroxidic Degradation) + 47.5 X 17 14 45 35 20% PP block polymer 100 MFR Comparative Ex. 1 100% PP 450 MFR 39 X 13.5 1 20 30

Claims (10)

1. Single-layered double sided abrasive nonwoven fabric made by a meltblown process, comprising a uniform mixture of microfibres of a fibre diameter of from 1 to 10 µm and macrofibres of a fibre diameter of from 15 to 50 µm and having a basis weight between 15 and 150 g/m², wherein the polymers consist of a mixture of a homopolymer and at least one copolymer or terpolymer or a mixture of at least two copolymers or terpolymers and the difference of the melt indices of the polymers is at least 50 units (g/10 min), characterized in that the mixture of polymers contains between 5% and 40% of a block polymer having a melt index between 50 and 200 g/10 min based on the total weight of the mixture of polymers.
2. Abrasive nonwoven fabric according to claim 1, characterized in that the polymers used are selected from polyolefins, polyesters, polyamides, polyester amides and copolymers thereof.
3. Abrasive nonwoven fabric according to any one of claims 1 or 2, characterized in that the basis weight of the nonwoven fabric is between 25 and 80 g/m².
4. Abrasive nonwoven fabric according to any one of claims 1 to 3, characterized in that the melt indices of the polymers used are between 50 and 1,600 g/10 min.
5. Abrasive nonwoven fabric according to any one of claims 1 to 4, characterized in that it further contains additives in an amount of from 0.01 to 15 wt% based on the total weight of the mixture of polymers.
6. Abrasive nonwoven fabric according to any one of claims 1 to 5, characterized in that as an additive one or more ingredients are used which are selected from hydrophilizing agents, pigments and dyes, stabilisators to oxidative decomposition and disinfectants.
7. Abrasive nonwoven fabric according to any one of claims 1 to 6, characterized in that the breaking load is at least 10 N/50 mm in machine direction and across the machine direction and simultaneously the breaking elongation is at least 15% in machine direction and across the machine direction.
8. Process for producing an abrasive nonwoven fabric according to any of the preceding claims in a meltblown process comprising the following steps of:

   - charging a mixture of polymers having different melt indices wherein the difference of the melt indices is at least 50 units (g/10 min), and optionally added additives into an extruder, wherein the mixture of polymers contains between 5% and 40% of a block polymer having a melt index between 50 and 200 g/10 min based on the total weight of the mixture of polymers;

   - extruding the mixture wherein the extruder outlet temperature is in a range between 180 and 300°C,

   - taking the extrudate to dies,

   - spinning the extrudate and

   - depositing the spun fibres on a collector.
9. Process according to claim 8, characterized in that the mixture of polymers further contains additives in an amount of from 0.01 to 15 wt% based on the total weight of the mixture of polymers.
10. Use of an abrasive nonwoven fabric according to any one of claims 1 to 7 for purifying spoilt surfaces.

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