ES2362723T3 - HYDROENTRAMED MICROFIBER MATERIAL AND METHOD FOR MANUFACTURING. - Google Patents

Abstract

The invention relates to a method for manufacturing a microfibre material and to a microfibre material manufactured by means of hydraulic entanglement. The method comprises to form a fibre web containing microfibres and, thereafter, to subject the fibre web to hydraulic entanglement. At least a majority of the microfibres are provided in the form of microfibres having been streched to orientation and having shell surfaces substantially completely covered by a hydropholic lubricating layer. The method further comprises to disperse the microfibres in a foamed aqueous medium before the forming by means of the hydrophilic lubricating layer in interaction with the foamed aqueous medium in order to form a substantially homogenous fibre dispersion, wherein the microfibres in a straightened condition have a fibre thickness smaller than 0.5 denier and a fibre length larger than 5 mm both in the fibre dispersion and in the microfibre material. In the microfibre material a majority of the microfibres are streched to orientation, exhibit a cross-sectional shape which substantially can be described by an arc or several successive arcs, and are uniformly distributed in a x, y-plane of the microfibre material.

Description

Technical field

The present invention relates to a method for manufacturing a microfiber material, a method that includes forming a fiber band containing microfibers and then subjecting the fiber web to hydraulic framework to obtain the microfiber material.

The invention also relates to a microfiber material manufactured by means of hydraulic framework, a material that includes microfibers that, in a straightened state, have a fiber thickness less than 0.5 denier and a fiber length greater than 5 mm.

Mainly, the microfiber material according to the invention is intended for use as a cleaning material, but can also be used, for example, in absorbent articles for hygiene applications.

Background of the invention

In the field of cleaning materials used in industries, in medical care and by domestic users, the so-called microfiber materials have been adopted.

These microfiber materials consist of textile materials or other fiber materials that contain very fine fibers or filaments. The fine fibers form a structure of the material that has very small pores, which create capillary forces that are considerably stronger than in conventional cleaning materials when it comes to absorbing liquids. This is particularly valuable in applications that require a good cleaning and drying capacity or where liquids with low surface tension must be absorbed.

Microfiber materials work particularly well to clean different surfaces with organic solvents, or to remove oils and greases, for example, from window panes or other surfaces.

The differences in material properties between microfiber materials and conventional fiber materials that contain thicker fibers can be very large. This is particularly the case when it comes to absorption properties, but also for other physical properties such as wear resistance, wet strength and softness / softness.

To provide the properties required by a microfiber material, the fine fibers or filaments must have a thickness not exceeding 1 denier, and preferably below 0.5 denier. Calculated with respect to a circular cross-section, and depending, of course, on the density of the polymer, one (1) denier corresponds to a fiber diameter of the magnitude of 10-11 μm, while 0.5 denier corresponds to approximately 7-8 μm.

A type of microfiber material that is usually produced today comprises so-called melt and extrusion filaments, that is thin and discontinuous filaments of varying dimensions. For example, U.S. Patent No. 4,906,513 describes a nonwoven cleaning cloth having improved absorbency characteristics. The cleaning cloth has a laminated construction with a medium layer of relatively high ream weight consisting of thermoplastic microfibers, manufactured by means of a melting and extrusion process, and additional fibers. On one side, the laminate has a light layer of generally continuous thermoplastic filaments that have a larger diameter and, on the other side, a microfiber layer. The cleaning cloths described claim to be resistant, similar to a fabric, and be useful for industrial use, in the food industry and other applications. According to US 4,906,513, the layers with continuous filaments provide strength and low defibration, while the combination of different layers provides improved cleaning properties. Preferably, the laminate is bonded by the application of heat and pressure, and the individual components are treated with a surfactant to improve wettability. A preferred combination is claimed as a layer of molten and extruded polypropylene microfibers and additional fibers that can be pulp fibers, and layer that, on one side, has a layer of spunbonded non-woven polypropylene filaments and, on the other side, a layer of microfibers that can be filaments of molten and extruded polypropylene.

In addition, U.S. Patent No. 4,775,579 discloses an elastic nonwoven material containing staple fibers intimately intertwined with an elastic band or mesh. According to US 4,775,579, the pulp fibers and the staple fibers may be hydraulically layered with an elastic nonwoven web to form an absorbent elastic nonwoven material, wherein the staple fibers preferably have between 1/4 of inch and 2 inches (0.635 cm and 5.08 cm) long and have a fiber diameter not exceeding 6 denier, and preferably not exceeding 1 or 1.5 denier. However, US 4,775,579 does not describe any specific example with discontinuous fibers, which are thinner than 1.5 denier, which is why the properties of the material that possibly resembles the microfiber material according with the

The present invention originates entirely from the use of filaments formed by melting and extrusion.

EP-A-0 926 288 describes a nonwoven fabric comprising melt and extrusion fibers and pulp fibers that have been mechanically woven. It is claimed that a suspension containing pulp fibers and fibers manufactured by melt and extrusion is prepared. However, it is not written how hydrophobic melt and extrusion fibers, which normally stick together, separate and disperse in the aqueous medium.

As a result of the functional principle of the melting and extrusion process, the plastic filaments extruded and formed by means of air blowing will not show, unlike the so-called discontinuous fibers, no true "normal dimension", but instead will show values in shape, length and thickness over a relatively wide distribution range. In addition, the filaments that have been formed in a melt and extrusion process are not stretched, and therefore lack the high degree of orientation and strength that can be given to the staple fibers by means of a suitable stretching process before cutting. By means of melting and extrusion techniques, it has been possible to manufacture microfiber materials that have a sufficiently fine pore structure to obtain good absorption properties, but not to achieve the high wear resistance and wet strength that are required for some products, for example industrial cleaning cloths.

Therefore, from a resistance point of view, it would be an advantage to be able to use stretched staple fibers when microfiber materials are manufactured.

US Patent No. 4,902,564 describes a method for manufacturing a highly absorbent nonwoven material, which is substantially made of synthetic pulp and medium length synthetic staple fibers. The method comprises forming an impermeable band containing 50-75 percent by weight of paper pulp and 25 -50 percent by weight of synthetic fibers having a fiber length of about 1/4 inch to about 1 inch (0.635 cm to 2.54 cm), and form a very compacted web of woven fibers by subjecting the fibers in the waterproof web to hydraulic webbing, and drying the web to form said nonwoven material. Without going into details, US 4,902,564 states that the fiber thickness of synthetic staple fibers may be in the range of about 0.5 to about 3 denier. In the practical embodiments listed in the description, synthetic staple fibers are 1.5 and 1.2 denier thick, that is fibers that are too thick to allow the required properties to be achieved in microfiber materials of the type described. in this document.

WO 93/06269 describes how the water dispersibility of polyester fibers and filaments improves by treating the unstretched polyester filaments, when freshly extruded, with a small amount of caustic, in a spinning finish.

Since, so far, it has been impossible to provide discontinuous fibers that are thin enough for microfiber materials, so-called split fibers have been adopted instead. Said split fibers are staple fibers or filaments with internal weak points that allow a split fiber to be divided into a multitude of longitudinal fibers, thinner after the formation of a nonwoven web. The division can be achieved, for example, by means of the supply of chemical products, or by means of the supply of mechanical energy, for example by needle puncturing or hydraulic framework.

The use of split fibers is known, for example, from US Patent No. 4,476,186, which describes a nonwoven web material comprising a first part and a second part. The first part consists of ultrafine fiber bundles of a dimension that does not exceed 0.5 denier, in which the fiber bundles of the first part are interwoven (interwoven) with each other. The second part comprises ultrafine fibers or fiber bundles of ultrafine fibers or both, which branch outwardly from the fiber bundles of the first part and are of a smaller dimension than the beams of the first part.

From US 4,476,186, it is clear that "ultrafine fiber bundle" should be understood as a fiber bundle in which a plurality of fibers in discontinuous or filament form are arranged parallel to each other. In addition, it is clear that the intended application, ie synthetic leather, requires a "grained" sheet that has a non-uniform fiber distribution. In US 4,476,186, it is stated that the ultrafine fibers used cannot be manufactured directly due to stability problems in the spinning process. Instead, split fibers are used that can be modified to ultrafine fibers at a suitable stage of the manufacturing process. The examples of said split fibers are said to be those that have a chrysanthemum-shaped cross section in which one component is interposed radially between another component, multi-layer bicomponent type fibers, multi-layer bicomponent fibers that have a cross section in the form of donut, mixed fibers obtained by mixing and spinning at least two components, split fibers of the "islands-in-a-sea" type (islands in a sea) having a fiber structure with a plurality of fibers ultrafine in the direction of the fiber that are joined together by other components. It is claimed that the split ultrafine fibers are preferably thinner than about 0.2 denier, and even more preferably thinner than about 0.05 denier.

The use of split fibers as a raw material for microfiber materials, however, has a number of disadvantages, such as a complicated and expensive fiber manufacturing process and, as a result of the division process required after the formation process, a greater energy consumption. In addition, it has been found that individual microfibers after splitting tend to remain in bundles or flocs of fibers in the vicinity of the initial position of the split fiber after the formation process. Such uneven fiber distribution in the finished microfiber material alters the resistance properties, particularly when it comes to wet strength, which is often a crucial property of a cleaning material. In addition, the formation of non-uniform fibers of microfiber materials based on split fibers will result in a pore size distribution that has a proportion of pores that are too large to allow a good cleaning and drying capacity.

Summary of the invention

Therefore, a first object of the present invention is to provide a method that eliminates the aforementioned problems, and that makes it possible to manufacture a microfiber material that has excellent absorption and resistance properties, without the need for any complicated and expensive use of filaments formed by melting and extrusion or split fibers.

According to claim 1, this first object is achieved by means of a method that includes forming a fiber band containing microfibers and then subjecting the fiber web to hydraulic fabric to obtain the microfiber material. According to the invention, at least a majority of the microfibers are provided in the form of microfibers that have been stretched to orient them and have substantially enveloped wrap surfaces completely covered by a hydrophilic lubricant layer, in which the method includes dispersing the microfibers in a foamed aqueous medium prior to formation by means of the hydrophilic lubricating layer in interaction with the aqueous medium to form a substantially homogeneous fiber dispersion, and the microfibers in a straightened state have a fiber thickness less than 0.5 denier and a fiber length greater than 5 mm both in the fiber dispersion and in the microfiber material.

In addition, a second object of the present invention is to provide a microfiber material having a very high wet strength and a pore size distribution that allows for a good cleaning and drying capacity, without the need to add melt-formed filaments and extrusion or split fibers.

According to claim 9, this second object is achieved by means of the microfiber material that includes microfibers which, in a straightened state, have a fiber thickness less than 0.5 denier and a fiber length greater than 5 mm, in which according to the invention at least a majority of the microfibers have been stretched to orient them, show a cross-sectional shape that can be described substantially by an arc or several successive arcs, and are uniformly distributed in an x-plane, and of the material of microfibers

Additional objects of the present invention will be apparent from the following description, while the features that allow these additional objects to be achieved are listed in the attached dependent claims.

Brief description of the figures

In the following, the invention will be described in more detail, inter alia, with reference to the attached figures, in which:

Figure 1, in the form of a diagram, shows results of a determination of the pore volume distribution in water for a hydro-framed fiber material containing conventional discontinuous fibers (Ref), and for a microfiber material according to the invention (EX 1); Y

The figure. 2 shows the corresponding results of a determination of the pore volume distribution in hexadecane.

Examples

To illustrate the very positive results that can be achieved by means of the present invention, the following Table 1 shows physical test results of a hydro-woven fiber material containing conventional discontinuous fibers (Ref), and the corresponding test results for a material of hydro-framed microfibers according to the invention (EJ 1).

Both non-woven materials were foamed in a hydrodynamic laminator, hydro-woven, pressed and dried, using laboratory equipment intended for that purpose. The person skilled in the art who has read this description can achieve the results by knowing the foaming and lattice techniques described in US Patent No. 5,720,851.

The fiber raw materials in the comparative example (Ref) were 60% by weight of pulp in chemical soft wood flakes, bleached under the product name Vigor Fluff from producer Korsnas AB, Sweden, and 40% by weight of a commercially available discontinuous polyester fiber with the designation EPM 133 and the normal dimension of 1.3 denier x 20 mm fiber from Kuraray Ltd, Japan. Foamed and hydro-framed materials with similar fiber compositions are commercially available.

5 The fiber raw materials for the microfiber material according to the invention (EJ 1) were 60% by weight of Vigor Fluff and 40% by weight of a discontinuous polyester fiber recently developed under the designation EPM 043 and the normal fiber dimension of 0.4 denier x 15 mm, from Kuraray Ltd, Japan.

Both materials were foamed in the hydrodynamic laminator at a foam surfactant concentration of 0.05%, in which it should be mentioned that suitable foam surfactants can be found by the aforementioned document US 5,720,851. Next, both materials were interwoven by means of 3 passes x 120 bars per side of the material by the top of a conventional relatively close humerus forming wire, using a framework nozzle with an opening pattern

15 adapted to the fiber composition in the comparative example (Ref). Accordingly, the framework parameters were left unchanged for the microfiber material in the example according to the invention (EJ 1).

Both materials were lightly pressed in a conventional laboratory pressing device at 1 m / min and a pressure of 2.5 bar. Finally, both materials were dried for 5 minutes at 140 ° C in a laboratory air dryer, and packed at 23 ° C and 55% relative humidity for 4 hours.

The results obtained are evident from the following Table 1.

Table 1 25

Ref (Comparative Example)

EJ 1 (Invention)

Fiber composition

60% by weight of Vigor fluff 40% by weight of PET EPM 133 (1.3 den x 20 mm) 60% by weight of Vigor fluff 40% by weight of PET EPM 043 (0.4 den x 15 mm)

Weight adjustment

80 g / m2 80 g / m2

Specific framing power

302 kWh / ton 288 kWh / ton

Lattice pressure, maximum

120 bars 120 bars

Weight

84.6 g / m2 88.8 g / m2

Specific volume (bulk)

5.1 cm3 / g 5.3 cm3 / g

MD tensile strength, dry

4590 N / m 3939 N / m

Tensile strength CD, dry

1362 N / m 1433 N / m

MD / CD ratio

3.4 2.7

Breaking Stretch √MD * CD

62% 47%

Work up to break rate √MD * CD

11.2 J / g 7.6 J / g

Traction index, dry √MD * CD

29.6 Nm / g 26.8 Nm / g

Traction index, water √MD * CD

14.8 N / m 24.4 Nm / g

Tensile index, surfactant solution √MD * CD

5.9 Nm / g 19.2 Nm / g

Relative resistance, water

fifty% 91%

Relative strength, surfactant solution

twenty% 72%

As is evident from Table 1 above, the microfibre material subjected to foaming and hydro-frameworks according to the invention (EJ 1) obtained a considerably higher wet strength in water and in surfactant solution than the fiber material subjected foamed and hydro-entangled with fibers

30 conventional discontinuous (Ref). A commercially available fatty alcohol ethoxylate (Lutensol AO 7) from BASF GmbH, Ludwigshafen, Germany was used for the wet strength test in surfactant solution.

The improvement of the wet strengths, which can be obtained by means of the invention (EJ 1), is particularly valuable, given that the resistance in water and in aqueous hydrophilic liquids, lubricants and that dissolve hydrogen bridges (for example the solution of surfactant used for the test of the material) is often the weakest point of hydro-framework cleaning materials. This is particularly the case when it comes to

fiber compositions containing pulp fibers.

The fact is that the microfiber material (EJ 1) shows considerably better strength values than those of previously known microfiber materials based on filaments formed by unstretched melt and extrusion.

In the form of a diagram, the attached figure 1 shows results of the determination of the distribution of the pore volume in water (H2O) for the foamed and hydro-spun fiber material in the comparative example (Ref), and corresponding measurement results for the microfiber material in the example according to the invention (EJ 1).

The determination of the pore size distribution (pore volume distribution) was performed within the range of the pore radius of 5-250 μm and through the use of a so-called DVP apparatus (Pore Volume Distribution), which It works by a principle that is well known to the person skilled in the art. For reasons of clarity, Figures 1 and 2 only illustrate the results, which were obtained in the pore radius range of 5 -100 μm.

When the pore volume distribution is determined, a sample of material having a given weight is placed in a pressure chamber, and it is completely moistened. Then, the pressure is increased so that the liquid is gradually expelled by pressure from the pores of the material. The weight of the ejected liquid is measured at each pressure increase by means of a pair of scales connected to the test chamber by means of a communicating vessel. A computer records the signals of the pair of scales and the pressure in the test chamber at each pressure increase. Next, the distribution of the pore volume can be calculated and plotted for evaluation by means of the LaPlace equation, which is well known to the person skilled in the art, and knowledge of the physical properties of the test liquid.

As is evident from Figure 1, the microfiber material according to the invention (EJ 1) shows a narrower pore volume distribution in water than the fiber material in the comparative example (Ref). In addition, the microfiber material according to the invention (EJ 1) shows a much larger number of pores having a pore radius of less than 30 μm than the fiber material in the comparative example (Ref).

The attached figure 2 shows results corresponding to those of figure 1, but for the measurement of DVP in hexadecane. Among other things, it is evident from Figure 2 that the microfiber material according to the invention (EJ 1) showed a considerably larger pore volume having a pore radius of less than 20 μm than the fiber material in the comparative example (Ref).

In fact, the microfiber material according to the invention (EJ 1) shows a pore size distribution of the type, which is particularly advantageous for achieving a good cleaning and drying capacity with both water and non-polar liquids with low viscosity. . Previously, it has been possible to achieve a pore size distribution of this type by means of the use of non-oriented melt and extrusion filaments which, however, gave comparatively low strengths of the material, but it was hardly possible to achieve it by means of use of split fibers that are also expensive and require different stages of division. The pore size distribution according to the invention (EJ 1) makes it possible to achieve a better cleaning and drying capacity than can normally be achieved with split fibers (not shown in the drawings). The reason for this is that, even though the split fibers that are constituted by a plurality of jointly bound potential microfibers may be comparatively uniformly distributed in the fiber web during formation, the splitting of the split fibers into the desired microfibers afterwards of the training process often becomes incomplete. The result is that microfiber materials based on split fibers, in addition to parts with the desired microfiber structure, will also show incompletely split unwanted split fibers or fully or partially aggregated bundles of microfibers. Such parts with incompletely divided split fibers or aggregate microfiber bundles mean that the maximum potential to provide strength and stretch of the microfibers will not be used. In addition, the less dense parts between the incompletely divided parts will create pores in the structure of the material that are larger than desired to obtain a good cleaning and drying capacity, particularly when it comes to the absorption of liquids with a low surface tension. , such as many organic solvents.

As is evident from Figure 1, the microfiber material according to the invention (EJ 1) shows a pore size distribution with a very small pore volume with a pore radius greater than 70 μm. The reason for this is, among other things, that a majority of the added microfibers are evenly distributed in an x-plane, and of the structure of the material.

The low volume of pores that are greater than 70 μm is also a result of the fact that there are no incompletely divided fibers or fiber bundles present in the microfiber material according to the invention, inter alia, given that all microfibers in their fiber manufacturing process they have been coated with a hydrophilic or finished lubricating agent (also called spinning finish), something that makes a uniform formation of microfibers possible in the foam. In addition, the hydrophilic lubricant is capable of facilitating the movements of the microfibers with respect to each other during the framework, something that improves the uniformity of the framework result and contributes to the narrower distribution of the pore size that is desired for the capacity of Cleaning and drying

5 When split fibers are used in accordance with the prior art, however, it is true that "parental fibers" may be provided with a finish, which facilitates uniform formation in the formation process. Such finishing, however, will only be active on the outer surfaces of the split fiber, while the bordering surfaces between the individual microfibers after division will show residues of the material of

10 connection or "adhesive" that held the split fiber together. It is easy to understand that such adhesive residues are more likely, for example in a framework process that intends to divide the split fibers into individual microfibers and entangle or interweave them into a continuous microfiber material, obstruct rather than facilitate the mobility of the fibers. individual microfibers with respect to each other. The comparatively poor mobility of the fiber in the framing process results in a less uniform framing result, and a

15 comparatively wider distribution of pore size that makes it difficult to achieve good cleaning and drying capacity.

The following Table 2 summarizes additional results of DVP measurements in water in the two nonwoven materials (Ref and EJ 1). In Table 2, the so-called accumulated pore volume distributions of the two materials are compared.

Table 2

DVP WATER

Ref (Comparative Example) EJ 1 (Invention)

Pore radius (μm)

Cumulative volume (mm3 / mg) % of total pore volume Cumulative volume (mm3 / mg) % of total pore volume

5

0 0 0 0

10

0.32 6 0.45 9

twenty

1.22 24 1.70 35

30

2.24 44 2.81 58

40

3.19 63 3.57 74

fifty

3.87 76 4.14 85

60

4.32 85 4.40 91

70

4.53 89 4.52 93

80

4.67 92 4.60 95

90

4.73 93 4.64 96

100

4.78 94 4.67 96

150

4.88 96 4.75 98

200

4.94 98 4.8 99

250

5.06 100 4.85 100

Among other things, it is evident from Table 2 above, that the distribution of the volume of pores accumulated in water increases considerably faster with the pore radius for the microfiber material according to the invention (EJ 1) than for the fiber material in the comparative example (Ref).

The following Table 3 shows the results corresponding to those of Table 2, but obtained from

30 measurements in hexadecane. In said non-polar solvent, the pore structure of the material will change relatively little compared to the pore structure, which occurs in a dry state.

Table 3

HEXADECAN DVP

Ref (Comparative Example) EJ 1 (Invention)

Pore radius (μm)

Cumulative volume (mm3 / mg) % of total pore volume Cumulative volume (mm3 / mg) % of total pore volume

5

0 0 0 0

10

0.17 3 0.25 5

twenty

0.94 19 1.31 28

30

1.64 3. 4 1.92 41

40

2.06 42 2.45 52

fifty

2.68 55 3.02 64

60

3.25 67 3.58 76

70

3.70 76 3.88 83

80

4.01 82 4.06 87

90

4.28 88 4.20

90

100

4.44 91 4.31 92

150

4.75 97 4.58 98

200

4.82 99 4.64 99

250

4.87 100 4.69 100

As is evident from Table 3 above, the accumulated pore volume increases considerably faster also in hexadecane for the microfiber material according to the invention (EJ 1) than for the fiber material in the comparative example (Ref ).

Detailed description of a preferred embodiment

In the following, a preferred embodiment and a series of alternative embodiments of a method for manufacturing a microfiber material according to the invention will be described in more detail.

The method includes forming a fiber band containing microfibers and then subjecting the fiber web to hydraulic fabric to obtain the microfiber material. Suitable pressing and drying stages of

15 a type that is known per se, follow after the hydraulic framework.

In the method according to the invention, at least a majority of the microfibers are provided in the form of microfibers that have been stretched to orient them and have wrapping surfaces substantially completely covered by a hydrophilic lubricating layer. The use of stretched microfibers allows the material

20 microfibers according to the invention obtain a considerably higher strength than was possible, for example, with non-stretched melt and extrusion filaments. In the preferred embodiment, the hydrophilic lubricant layer is constituted by a spinning finish of one type, which is adapted for wet formation. Chemicals suitable for use as a staple fiber spinning finish are well known to those skilled in the art.

In accordance with the invention, the method further comprises dispersing the microfibers in a foamed aqueous medium prior to formation by means of the hydrophilic lubricating layer in interaction with the foamed aqueous medium to form a substantially homogeneous fiber dispersion. According to one theory, the invention not being, however, linked to this theory, it is believed that since an aqueous medium is used

When foamed, the hydrophilic lubricant layer will not be removed by washing the fibers as easily as it would have been if the fibers had been dispersed in water. It is believed, therefore, that the foam helps keep the lubricant layer on the fiber surface for a longer period of time.

In the method according to the invention, when observed in a straightened state, the microfibers have a

35 fiber thickness less than 0.5 denier and a fiber length greater than 5 mm in both the fiber dispersion and the microfiber material. Depending on the intended application, the microfibers used in the present invention may include different polymers, for example polyester, polyamide, polypropylene, polyethylene, cellulose, etc.

As a result that the microfibers in the method according to the invention are microfibers already separated before formation and that all microfibers are coated with a hydrophilic lubricating layer, a considerably more uniform distribution of microfibers in the nonwoven material is obtained. Finishing what was possible with microfibers included in a split fiber that will not separate from each other until after formation. Among other things, the more uniform distribution of microfibers according to the invention makes it possible to achieve

45 very high wet strengths and a narrow pore volume distribution that provides good

cleaning and drying properties and very strong capillarity forces.

Since the microfibers are dispersed in a foamed aqueous medium, the microfibers are guided in a controlled manner by the gas bubbles in the foam, which makes it possible to obtain very uniform fiber formation also with considerably longer microfibers than would be possible. if the aqueous medium had been mainly water. Preferably, the microfibers have a fiber length between 10 and 25 mm.

In an embodiment of the method according to the invention, also a proportion of pulp fibers are dispersed in the foamed aqueous medium together with the microfibers. The pulp fibers may be, for example, softwood or bleached softwood fibers in applications where a high specific volume and total absorption are required, and unbleached or bleached hardwood fibers in applications where a particularly dense pore structure and high cleaning and drying capacity. When pulp fibers are added, counted for a total amount of dry fibers, advantageously 10-100% by weight of the microfibers and 0-90% by weight of the pulp fibers are dispersed in the foamed aqueous medium.

Embodiments involving the addition of pulp fibers are advantageous, inter alia, for economic reasons, since pulp fibers are a considerably less expensive raw material than microfibers. In some cases, however, the mixture of pulp fibers can also provide improved absorption properties, particularly when it comes to the absorption of polar solvents such as water.

According to the invention, particularly advantageously, the hydrophilic lubricant layer is applied as a spinning finish before short cutting said microfibers. However, embodiments are also conceivable in which the lubricating layer is applied in another suitable manner, for example by means of short-cut microfibers that are impregnated with a suitable chemical agent, after fiber cutting but before the stage dispersion.

As a result of their greater flexibility, lower friction of the fibers, and greater number of fiber ends, the microfibers used in the method according to the invention are easier to enter than the thicker and stiffer split fibers used previously, and do not consume lattice energy to divide the split fibers into individual microfibers. Therefore, in a particularly advantageous embodiment of the method according to the invention, less than 300 kWh / ton of frame energy is consumed in the hydraulic framework.

In another advantageous embodiment, as a result that the microfibers in the method according to the invention are so easy to enter, a hydraulic pressure not exceeding 120 bars can be used in the hydraulic framework. This embodiment is, of course, advantageous for both technical and process and economic reasons.

In a particularly advantageous embodiment, the microfiber material is subjected to a corona or plasma treatment after the hydraulic framework to modify a possible residue of the hydrophilic lubricant layer to provide greater fiber-fiber friction. Modification of the hydrophilic lubricant layer preferably takes place after drying of the microfiber material, and particularly advantageously includes oxidation with oxygen in the air, but other chemical reactions can also occur. The basic technique for the treatment of plasma and corona of nonwoven hydro-woven materials is described in European Patent No. 0 833 877 B1.

Next, a preferred embodiment and a series of alternative embodiments of a microfiber material according to the invention will be described in more detail, in which reference is made to the accompanying tables and figures.

The microfiber material according to the invention has been manufactured by means of hydraulic framework and includes microfibers, which in a straightened state have a fiber thickness less than 0.5 denier, that is 0.56 dtex, and a fiber length greater than 5 mm. Naturally, these fiber dimensions refer to average dimensions, and it should be apparent to the person skilled in the art that some variation will occur around the average values.

In the microfiber material according to the invention, at least a majority of the microfibers are stretched to orient them. This makes it possible to give the microfiber material according to the invention a greater resistance than is possible, for example, by means of filaments formed by melt and extrusion not stretched.

According to the invention, the microfibers of the material also show a cross-sectional shape that can be described by an arc or several successive arcs, in which the microfibers are uniformly distributed in an x-plane, and of the microfiber material.

Accordingly, the microfibers in the material according to the invention advantageously show a circular, elliptical or ribbon-shaped cross section, which provides high fiber mobility during the framework and makes it possible to achieve a well defined pore volume distribution. . Furthermore, according to the invention, the microfibers are uniformly distributed in an x-plane, and of the microfiber material. Therefore, "uniformly distributed" should be understood as a uniform formation at least after the formation stage, and a formation that is as uniform as possible after a possible opening process or the like in relation to the hydraulic framework.

The uniform distribution in the x-plane, and according to the invention differs greatly from previously known microfiber materials in which comparatively thick cleft fibers had first formed in a band and then, in relation to the fabric or other subsequent stage of the process, they had been divided into microfibers. In the previously known materials that are based on split fibers, after dividing the individual microfibers they will remain in the vicinity of the position that a split fiber had in the material after the formation stage, and produce "islands" or "flocs" in the finished material with a high concentration of microfibers surrounded by regions with a lower microfiber content. Said non-uniform distribution of microfibers in the x-plane, and will give a wider distribution of pore volume and a cleaning and drying capacity that is lower compared to the capacity that can be achieved in the microfiber material according to the invention.

Preferably, the microfiber material according to the invention is characterized in that substantially all of the wrap surfaces of most microfibers show equivalent surface roughness. This should be understood as if the wrapping surfaces of the fibers show substantially the same surface properties along the entire length of the fiber and around the entire circumference of the fiber, and that these surface properties have been adapted both to allow formation of uniform fibers in the formation stage as a high fiber-fiber mobility in the fabric stage. This characteristic distinguishes the microfiber material according to the invention from nonwoven materials based on split fibers in which the microfibers formed in the splitting process will show parts that have been oriented outwardly of the split fiber, and parts that before of the division have been oriented inwards, inwards of the split fiber and that have surface properties that are unfavorable for fiber-fiber mobility and uniformity of the formation.

In another advantageous embodiment, the microfiber material according to the invention is characterized in that substantially all adjacent microfibers, of most of the aforementioned microfibers, show different extensions in said plane x, y. This is an advantage, inter alia, from the point of view of the durability of the material, and is made possible since the microfibers are separated and can be distributed in a comparatively anisotropic manner in the formation stage (i.e. without being oriented in a direction of the particular sheet). This differs from split fiber-based materials in that, as mentioned above, microfibers after division tend to remain close to the initial positions of the split fibers, and in that adjacent microfibers easily form bundles along its entire length or parts of its length.

In a preferred embodiment of the invention, the microfiber material shows a formation of fibers created by foaming. In a further preferred embodiment, most microfibers have a fiber length between 10 and 25 mm. Normally, by means of a visual inspection or a microscope, a person skilled in the art is able to determine if a material has foamed.

In an advantageous embodiment of the invention, the microfiber material includes a part of pulp fibers together with the microfibers. Counted with respect to a total amount of dry fibers, the microfiber material advantageously includes 10 -100% by weight of the microfibers and 0 -90% by weight of pulp fibers.

Advantageously, the microfiber material according to the invention is characterized in that some microfiber wrap surfaces show a residue of a hydrophilic lubricating agent.

In a particularly preferred embodiment, some microfiber wrap surfaces show an oxidized residue of a hydrophilic lubricating agent, in which oxidation in a particularly advantageous manner has been achieved by means of plasma or corona treatment in the presence of oxygen.

In the preferred embodiment, the microfiber material according to the invention shows a tensile index √MD * CD that is greater than 20 Nm / g both in the dry state and in water, and preferably also a tensile index √MD * CD which is greater than 15 Nm / g in a solution of lubricating surfactant that dissolves hydrogen bonds, such as a solution in fatty alcohol ethoxylate water or a solution with corresponding properties.

In addition, the microfiber material according to the invention preferably shows a pore volume distribution, measured by DVP in the pore radius range of 5-250 µm, which has a maximum volume in a pore radius of less than 20 μm. This is the case when measured in water or hexadecane, but most preferably in both cases. When it comes to this embodiment and the embodiments described in the following description, particular reference is made to the results shown in Tables 2 and 3, and in Figures 1 and 2.

In an advantageous embodiment, the microfiber material shows a distribution of the pore volume, measured by DVP in water, which has a cumulative pore volume that is at least 30% of the total pore volume of the microfiber material for pore radii. between 5 and 20 μm and at least 90% of the total pore volume for pore radii between 5 and 60 μm. This embodiment provides properties that are particularly advantageous for the absorption of aqueous liquids.

For the absorption of non-polar liquids, such as many organic solvents, the microfiber material particularly advantageously shows a pore size distribution, measured by DVP in hexadecane, which has a cumulative pore volume that is at least 25% of the total pore volume of the microfiber material for pore radii between 5 and 20 μm and at least 70% of the total pore volume for pore radii between 5 and 60 μm,

Particularly advantageously, the microfiber material shows a pore size distribution, measured by DVP in water, in which less than 20% of the total pore volume of the microfiber material is located in pores that have a pore radius that exceeds 40 μm, and particularly advantageously also a pore size distribution, measured by DVP in hexadecane, in which less than 20% of the total pore volume of the microfiber material is located in pores that have a pore radius that exceeds 70 μm. This ensures sufficiently strong capillary forces when the microfiber material according to the invention is used as a cleaning material.

In a particularly preferred embodiment, the microfiber material shows a pore volume distribution, measured by DVP, in which less than 2.5% of the total pore volume of the microfiber material, when measured in both water and hexadecane , is located in pores that have a pore radius that exceeds 150 μm. This embodiment ensures that the microfiber material according to the invention, when used as a cleaning material, does not absorb any large amount of liquid in pores that have capillary forces that are too weak to hold the liquid safely. Therefore, the particularly preferred embodiment provides good cleaning and drying characteristics when it absorbs both aqueous and non-polar liquids with low surface tension.

A fundamental advantage of the present invention is that the hydro-framed microfiber material with high strength can be manufactured with low energy consumption, since the microfibers used in accordance with the invention can be distributed very uniformly on the sheet in the process of formation and have good framework properties, and since no dividing energy is required to make the fibers finer, something that is required when using conventional split fibers.

In the foregoing, the present invention has been described by way of examples and a number of different embodiments. However, the invention should not be contemplated as being limited exclusively to these examples and embodiments, but its scope is defined in the following claims.

Therefore, it is also conceivable that the microfiber material according to the invention is used for purposes other than a cleaning material, for example that the microfiber material is used as part of an absorbent article for hygiene purposes.

Claims (26)

one.

A method for manufacturing a microfiber material, which includes forming a fiber band containing microfibers and then subjecting said fiber web to hydraulic fabric to obtain said microfiber material, characterized in that at least a majority of said microfibers are they provide in the form of microfibers that have been stretched to orient them and have substantially enveloped wrap surfaces completely covered by a hydrophilic lubricant layer, and because the method includes dispersing said microfibers in a foamed aqueous medium before said formation by means of said hydrophilic lubricating layer in interaction with said foamed aqueous medium to form a substantially homogeneous fiber dispersion, wherein said microfibers in a straightened state have a fiber thickness less than 0.5 denier and a fiber length greater than 5 mm both in said fiber dispersion as in said microfiber material.

2.

A method according to claim 1, characterized in that said microfibers are provided with a fiber length that is between 10 and 25 mm.

3.

A method according to any one of the preceding claims, characterized in that also a proportion of pulp fibers is dispersed in said foamed aqueous medium together with said microfibers.

Four.

A method according to any one of the preceding claims, characterized in that, counted for a total amount of fibers, 10 -100% by weight of said microfibers and 0 -90% by weight of pulp fibers are dispersed in said foamed aqueous medium.

5.

A method according to any one of the preceding claims, characterized in that said hydrophilic lubricant layer is applied as a spinning finish before short cutting said microfibers.

6.

A method according to any one of the preceding claims, characterized in that less than 300 kWh / ton of frame energy is consumed in said hydraulic framework.

7.

A method according to any one of the preceding claims, characterized in that a hydraulic pressure not exceeding 120 bar is used in said hydraulic framework.

8.

A method according to any one of the preceding claims, characterized in that the microfiber material is subjected to a corona or plasma treatment after said hydraulic framework to modify a possible residue of said hydrophilic lubricant layer, to provide greater friction fiber-fiber

9.

A microfiber material manufactured by means of hydraulic framework, including said microfiber material, microfibers that in a straightened state have a fiber thickness less than 0.5 denier and a fiber length greater than 5 mm, characterized in that at least one Most of these microfibers have been stretched to guide them.

10.

A microfiber material according to claim 9, characterized in that substantially all of the wrap surfaces of said majority of microfibers show equivalent surface roughness.

eleven.

A microfiber material according to claim 9 or 10, characterized in that substantially all adjacent microfibers, of said majority of microfibers, show different extensions in said plane x, y.

12.

A microfiber material according to any one of claims 9 to 11, characterized in that the microfiber material shows a formation created by foaming, and that said majority of microfibers have a fiber length between 10 and 25 mm.

13.

A microfiber material according to any one of claims 9 to 12, characterized in that the microfiber material includes a proportion of pulp fibers together with said microfibers.

14.

A microfiber material according to any one of claims 9 to 13, characterized in that the microfiber material, counted with respect to a total amount of dry fibers, includes 10 -100% by weight of said microfibers and 0 -90 % by weight of pulp fibers.

fifteen.

A microfiber material according to any one of claims 9 to 14, characterized in that some wrapping surfaces of said microfibers show a residue of a hydrophilic lubricating agent.

16.

A microfiber material according to any one of claims 9 to 15, characterized in that some wrapping surfaces of said microfibers show an oxidized residue of a hydrophilic lubricating agent.

17.

A microfiber material according to any one of claims 9 to 16, characterized in that

The microfiber material shows a tensile index √MD * CD that is greater than 20 Nm / g both in the dry state and in water.

18.

A microfiber material according to any one of claims 9 to 17, characterized in that the microfiber material shows a tensile index √MD * CD that is greater than 15 Nm / g in a lubricating surfactant solution that dissolves bridges of hydrogen.

19.

A microfiber material according to any one of claims 9 to 18, characterized in that the microfiber material shows a pore size distribution, measured by DVP in water in the pore radius range of 5-250 μm, which It has a maximum volume in a pore radius of less than 15 μm.

twenty.

A microfiber material according to any one of claims 9 to 19, characterized in that the microfiber material shows a pore size distribution, measured by DVP in hexadecane in the pore radius range of 5-250 μm, which It has a maximum volume in a pore radius of less than 15 μm.

twenty-one.

A microfiber material according to any one of claims 9 to 20, characterized in that the microfiber material shows a pore size distribution, measured by DVP in water, having an accumulated pore volume that is at least 30 % of the total pore volume of the microfiber material for pore radii between 5 and 20 μm and at least 90% of said total pore volume for pore radii between 5 and 60 μm.

22

A microfiber material according to any one of claims 10 to 21, characterized in that the microfiber material shows a pore size distribution, measured by DVP in hexadecane, which has a cumulative pore volume that is at least 25 % of the total pore volume of the microfiber material for pore radii between 5 and 20 μm and at least 70% of said total pore volume for pore radii between 5 and 60 μm.

2. 3.

A microfiber material according to any one of claims 9 to 22, characterized in that the microfiber material shows a pore size distribution, measured by DVP in water, in which less than 20% of the total pore volume of the Microfiber material is placed in pores that have a pore radius that exceeds 40 μm.

24.

A microfiber material according to any one of claims 9 to 23, characterized in that the microfiber material shows a pore size distribution, measured by DVP in hexadecane, in which less than 20% of the total pore volume of the Microfiber material is placed in pores that have a pore radius that exceeds 70 μm.

25.

A microfiber material according to any one of claims 9 to 24, characterized in that the microfiber material shows a pore size distribution, measured by DVP, in which less than 2.5% of the total pore volume of the Microfiber material, when measured in both water and hexadecane, is located in pores that have a pore radius that exceeds 150 μm.

26.

A microfiber material according to any one of claims 9 to 24, characterized in that the microfibers have a circular or elliptical cross-section.