ES2389370T3 - Nonwoven material entangled hydraulically and method of doing so - Google Patents

Abstract

A hydraulically entangled, nonwoven, non-woven, foam-laid material containing at least 30%, by weight, of pulp fibers and at least 20%, by weight, of artificial fibers or filaments, characterized in that said non-woven material has a weight variation based on a non-random configuration, because it includes a plurality of pads of higher base weight (25) that protrude from a main surface of said material, said pads as a main component include pulp fibers (26) and are surrounded by a certain network lower base (27) containing a relatively higher amount of artificial fibers or filaments (28) pads with the pads (25).

Description

Nonwoven material entangled hydraulically and method of doing so

Technical background

The present invention relates to a hydraulically entangled non-woven foam or wet laid material containing at least 30%, by weight, of pulp fibers and at least 20%, by weight, of artificial fibers. It also refers to a method of making such material.

Hydro entanglement or entanglement is a technique introduced during the 1970s, see, for example, CA patent number 841 938. The method involves forming a sheet of fibers, wet or dry, after which the fibers are entangle by means of very fine jets of water at high pressure. Several rows of water jets are directed against the fiber sheet, which is supported by a moving wire. The tangled fiber sheet is subsequently dried. The fibers used in the material may be natural fibers, especially cellulosic pulp fibers, artificial tuft fibers, which may be synthetic, for example, polyester, polyamide, polyethylene, polypropylene, or regenerated tuft fibers, for example, viscose, rayon, lyocell or the like, and mixtures of pulp fibers and tuft fibers. High quality interlaced materials can be produced at a reasonable cost and have a high absorption capacity. They can be used, for example, as cleaning material for domestic or industrial use, as disposable materials in medical care and hygiene applications, etc.

By EP-B-0 333 211 and EP-B-0 333 228, for example, it is known to hydroentangle a fibrous mixture in which one of the fiber components are continuous filaments in the form of blown and molten fibers.

WO 96/02701 describes the hydro-entanglement of a fibrous sheet formed of foam. The fibers included in the fibrous sheet may be pulp fibers and other natural fibers and artificial fibers.

During hydro-entanglement, the fiber sheet is supported by a wire or a perforated cylindrical metal drum. An example of such a hydro-entanglement unit is described, for example, in EP-A-0 223 614. However, support elements in the form of threads of the type used in connection with paper production is the most frequent type as shown, for example, in EP-A-0 483 816. A disadvantage of using threads of this type is that, during hydro-entanglement, water jets exert a strong action on the fiber sheet and this will penetrate and become trapped. between the wire threads. Then it can be difficult to separate the final product from the wire.

WO 01/88261 describes the use of a molded sieve of closed mesh of thermoplastic material as a support element during hydro-entanglement of a fibrous sheet. The extraction of the final product from said sieve is simplified compared to a wire.

In US Pat. No. 6,163,943 a method of producing a nonwoven nonwoven material is described as a mixture of fibers containing continuous filaments, for example, blown and molten fibers and / or spun fibers, and natural fibers and / or synthetic fibers of tuft. The method is characterized by foaming a fibrous sheet of natural fibers and / or synthetic strand fibers and jointly hydro-entangling the dispersion of foamed fibers with the continuous filaments to form a composite material where the continuous filaments are well integrated with the rest of the fibers.

When making a non-woven material, especially a material that is intended to be used as a cleaning material, there are many properties that are important, such as absorption capacity, absorption rate, wet strength, softness, ability to conform, low glare, high cleaning capacity, etc. However, it is difficult to combine all these properties in one and the same material. For example, it is possible to make hydro-tangled, low-pitched, strong, soft, fabric-like non-woven material using 100% synthetic fibers. However, the absorption properties of said material will be low. Materials containing a high amount of pulp fibers have high absorption capacity, but poor wet strength and high shaving. The wet and dazzle resistance properties can be improved by the addition of chemicals, such as wet strength agents and binders.

Summary of the Invention

The object of the present invention is to provide a hydro-entangled nonwoven material that combines properties such as wet strength, absorption capacity, softness and the ability to conform. This has been achieved with a nonwoven material hydraulically entangled with foam or wet lying containing at least 30%, by weight, of pulp fibers and at least 20%, by weight, of artificial fibers or filaments, said material having no woven a variation of base weight in a non-random configuration in which it includes a plurality of pads of higher base weight that protrude from a main surface of said material, said pads as a main component include pulp fibers and are surrounded by a net of lower base weight containing a relatively higher amount of artificial fibers or filaments compared to

pads

This specific structure is considered to provide:

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an aspect of the cloth-like material;

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high strength due to the network of artificial fibers;

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high absorption capacity provided by the high paste pads and the three-dimensional structure formed by them;

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high softness and ability to conform due to the plurality of bending indications provided by the network configuration.

The opposite main surface of the material is preferably substantially smooth. This will improve the ability of the material to dry a surface by removing the remaining liquid.

The material preferably contains 40%, and more preferably at least 50%, by weight, of pulp fibers. It preferably contains at least 30%, and more preferably at least 40%, by weight, of artificial fibers or filaments. In one embodiment, the artificial fibers are tuft fibers between 6 mm and 25 mm in length.

It is preferred that the material has an absorption capacity of at least 5 g / g of water.

It is also preferred that the material has an absorption rate, WAT, in MD not exceeding 1.5 s / m, preferably not exceeding 1 s / m, and in CD not exceeding 2.5 s / m, preferably not more than 2 s / m.

In a preferred embodiment, the pads have a length and width of between 0.2 and 4 mm, preferably between 0.5 and 2 mm. It is also preferred that the distance between adjacent pads is between 0.2 and 4 mm, preferably between 0.5 and 2 mm.

The present invention also relates to a method of producing a nonwoven material as indicated above, said method includes wet laying or foaming a dispersion of fibers to form a fibrous sheet containing at least 30%, by weight, of fibers of paste and at least 20%, by weight, of artificial fibers or filaments, calculated on the total weight of the fibers in said fibrous sheet, and hydroentangling the fibrous sheet followed by subsequent dehydration and drying, where the fibrous sheet is formed in a wire of formation and is subjected to a first hydro-entanglement while it is supported on said formation wire and is subsequently transferred to a second hydro-entanglement step that is carried out in a foraminous support element in the form of a molded mesh screen of a material thermoplastic, said sieve having holes of the size in transverse dimension of 0.2-4 mm and the distance between the holes being between 0.2-4 mm.

Preferably the holes in said sieve are the size of 0.5-2 mm and the distance between the holes is between 0.5-2 mm.

Preferably, said additional hydro-entanglement is carried out from the opposite side of the fibrous sheet compared to the first hydro-entanglement.

In a preferred embodiment, after dehydration, the sheet is subjected to non-compacting drying, such as air drying, IR drying or the like. In order to maintain the volume and absorbency of the material preferably no pressure of the fibrous sheet takes place during dehydration and drying.

Description of the drawings

The invention will be described below with reference to some embodiments described in the accompanying drawings.

Figure 1 is a schematic view of a device for hydro-entangling a fibrous sheet.

Figure 2 depicts a schematic perspective view, on an enlarged scale, of a sieve used to support the fibrous sheet during hydro-entanglement.

Figure 3 is an image taken of a nonwoven material according to the invention in an approximately 30 times magnification.

Figures 4 and 5 are electron microscope (SEM) images of a nonwoven material according to the invention.

Description of realizations

The device, which is schematically represented in Figure 1, for manufacturing the so-called hydro-entangled or interlaced material, includes a container 10, for example, a pulper, in which a dispersion of wet or foam fibers is prepared, which by means of a container 11 is distributed on a foraminous support element 12. This foraminous support element 12 is preferably a wire of any conventional type used in the papermaking industry and which is suitable for forming and for a first step of hydro-entanglement for weaving the less artificial fibers present in the sheet. The fibrous sheet formed 13 is then subjected to hydro-entanglement from several rows of nozzles 14, from which jets of water are directed at very high pressure towards a fibrous sheet, while being supported by the foraminous support member 12. The fibrous sheet is drained on suction boxes 15. Therefore, the water jets carry out a tangle of the fibrous sheet, that is, an interweave of the fibers. The appropriate pressures in the tangle nozzles are adapted to the fibrous material, the weight of the fibrous sheet, etc. Water from the entanglement nozzles 14 is removed by the suction boxes 15 and is pumped to a water purification plant, and then recirculated to the entanglement stations.

For a further description of the hydro-entanglement technology or, as it is also called, interlaced, reference is made, for example, to said CA patent number 841 938.

The fibrous sheet 13 is wet or foamed. In a wet laying process, the fibers are dispersed in a liquid, usually water, similar to the papermaking process and the diluted fiber dispersion is deposited on the foraminous support element where it is dehydrated to form a material. continuous sheet mode. The fiber dispersion can be diluted to any consistency used used in a conventional papermaking process. A foaming process is a variant of a wet laying process and a surfactant is added to the fiber dispersion, which is foamed, and the dispersion of foamed fibers is deposited on the foraminous support. A very uniform distribution of fibers is achieved in a foaming process and it is also possible to use longer fibers than in a conventional wet laying process.

The fibers used to form the fiber dispersion is a mixture of cellulosic pulp fibers and artificial fibers of tuft or artificial filaments. The pulp fibers can be selected from any type of pulp and mixtures thereof. The pulp is preferably characterized by being completely natural cellulosic fibers and may include cotton as well as wood fibers. Preferred pulp fibers are soft wood pulp for papermaking, although hardwood pulp and non-wood pulp, such as hemp and sisal, can be used. The length of pulp fibers can vary from less than 1 mm for hardwood pulp and recycled pulp up to 6 mm for certain types of softwood pulp. The fiber dispersion must contain at least 30% by weight of pulp fibers, calculated on the total fiber weight.

The artificial fibers may be any suitable synthetic fibers or regenerated cellulosic fibers. Examples of synthetic fibers in common use are polyester, polyethylene, polypropylene, polyamide, polylactides and / or their copolymers. Examples of regenerated fibers are rayon, viscose, lyocell. Artificial fibers may be in the form of strand length fibers. A preferred length of the tuft fibers used in a wet laying or foaming process is between 6 mm and 25 mm. The fineness of the fibers can vary between 0.3 dtex and 6 dtex. The fiber dispersion must contain at least 20% by weight, calculated on the total fiber weight, of artificial fibers.

Artificial filaments are preferably interlaced or blown and molten filaments of suitable thermoplastic polymers, such as polyethylene, polypropylene, polyamides, polyesters and polylactides. Naturally, copolymers of these polymers can also be used, as well as natural polymers with thermoplastic properties.

The sheet 13 is rotated 180 ° and transferred to a second foraminous support member 16, which in a preferred embodiment is constituted by a closed mesh molded plastic screen, as described in WO 01/88261. The plastic screen according to the invention may consist of one layer, as shown in Figure 2, or two or more layers applied on top of each other. Possibly, the sieve can be reinforced with reinforcing threads 17 extending in the intended direction of the machine of the plastic sieve / tangle wire 16. Reinforcement threads can also be arranged in the transverse direction of the sieve, or both in the longitudinal direction as in the transverse direction. The production of the plastic sieve can take place, for example, in the manner described in US

4,740,409. The plastic sieve is provided with a plurality of holes 18, which will be described in more detail below.

The sheet is hydro-entangled a second time from several rows of nozzles 19 while being supported on the plastic sieve element 16. The second hydro-entanglement takes place from the opposite side of the fibrous sheet 13 compared to the first hydro-entanglement. The fibrous sheet is drained on suction boxes 20.

Additional dehydration of the fibrous sheet can take place on suction boxes 21, while sheet 13 is transferred to a dehydration wire 22. This additional dehydration can optionally take place

while the fibrous sheet is still supported by the plastic sieve element 16.

The tangled material is then taken to a drying station 23 for drying before the finished material is rolled into a reel and converted. Drying can be carried out by blowing hot air through the fibrous sheet, by IR dryers or other non-compacting drying technique. Preferably no pressure of the fibrous sheet takes place during dehydration and drying. Prior to conversion, the material may be subjected to different types of treatment, such as corona or plasma treatment 24, treatment with chemicals of any desired type, etc. The corona or plasma treatment is preferably carried out after drying while chemical substances can be added to the fiber dispersion or after dehydration of the sheet by spraying an impression or the like.

In the embodiments shown in Figure 2, the holes 15 in the screen 16 exhibit a rectangular shape, but it is clear that this shape can be varied to any geometric shape. Screen meshes adequately exhibit a hole size within the range of 0.2-4 mm, preferably 0.5-2 mm. Hole size is defined here as the size between opposite side edges or corners. The holes are substantially the same size or different sizes, and are evenly distributed through the screen or arranged to form configurations with alternate groups of holes of different sizes. Also the cross-sectional shape of the holes in the z direction can be varied, and can be, for example, substantially rectangular, alternately convex or concave. The distance between the holes may vary between 0.2-4 mm, preferably between 0.5 and 2 mm. The distance between the holes is defined as the shortest distance between adjacent holes.

In case the sieve consists of two or several layers arranged on top of each other, the different layers can exhibit different hole sizes with each other, for example, with larger holes in an upper layer and smaller holes in a lower layer. This is shown in WO 01/88261. In this way, the fibers can penetrate the larger holes in the upper layer, but be retained by the lower layer during entanglement.

The surface, intended to support the fibrous sheet, can be substantially smooth, or exhibit a three-dimensional structure in order to impart a three-dimensional structure corresponding to the hydro-entangled material.

Other foraminous supports such as threads and other types of sieves, having holes of the size indicated above can also be used.

By hydro-entangling the fiber dispersion through the perforated sieve 16, the shorter pulp fibers, which are more easily mobile, will follow the water that drains through the holes 18 and will accumulate in said holes, while longer artificial fibers that are less mobile and more easily crosslinked by water jets, will remain more in position in sieve 16 and will create a strong fibrous network.

This will result in a non-woven material having a plurality of pads 25 protruding from a main surface of the material, said pads as a main component include pulp fibers 26 which during drainage have accumulated in the holes 18 of the screen 16. The term "main component" in this regard means that more than 50% by weight, preferably more than 60% by weight and more preferably more than 70% by weight of the fibers present in said pads are pulp fibers 26. A smaller proportion Of the fibers in the pads 16 will naturally be artificial fibers.

The pulp fiber pads 25 are surrounded by a net 27, which contains a relatively higher amount of artificial fibers 28 compared to the pads 25. In a preferred embodiment more than 50% by weight, preferably more than 60% by weight and more preferably more than 70% by weight of the fibers present in said network are artificial fibers 28. The longer artificial fibers 28 are more easily entangled and will be interwoven with each other to form a strong continuous network 27 that will impart high resistance to the material. . Pasta fiber pads contribute to the absorbency of the material. This is shown in Figures 4 and 5 representing SEM images of a material according to the invention, and in which the accumulation of pulp fibers 26 to form the pads 25 can be seen. It is also seen how these pads 25 are surrounded by a network. This is also seen in the light microscope image in Figure 3.

In order to provide a pronounced damping effect, at least 30% by weight and preferably at least 40% of the fibers in the material must be pulp fibers, and in order to provide a strong network of artificial fibers crosslinked at least 20% by weight and preferably at least 30% by weight of the fibers in the material should be artificial fibers.

The length and width dimensions of the pads 25 will correspond to the size of the holes 18 of the screen 16, and the width of the net wires 27 between the pads 25 will correspond to the distance between adjacent holes 18 of the screen 16.

The opposite main surface of the material is preferably substantially smooth compared to the first surface having a pronounced three-dimensional structure provided by the plurality of protruding pads. This gives the material a two-sided property, one side being the "rougher" side and being adapted to remove and capture liquids, viscous fluids and solid particles from a surface. The opposite smooth surface is adapted to clean a dry liquid surface.

5 Tests have been performed on materials produced as described below.

A foam fiber dispersion was made from water, surfactant and a mixture of paste fibers and artificial fibers of tuft length. A surfactant was added to the water in an amount of 0.03% by weight. The dispersion of foamed fibers was placed on a wire, and the formation was carried out at a foam air content of 30-50% by volume. The fibrous sheet was hydrogenated on the same wire used for formation. The sheet was subsequently transferred to a closed mesh molded plastic sieve as described above, which has holes of the size of 0.89 x 0.84 mm and a distance between the holes of 0.46 mm. Then the sheet was hydroenvented from the opposite side. The main part of the hydroenredo was carried out in the first

15 wire in order to give maximum strength to the material. The total energy supply in the hydroenredo was approximately 200 kWh / ton of material.

The fibrous sheet was then dehydrated by vacuum aspiration boxes and dried by so-called air drying (TAD). The fibers used to form the fibrous sheet had the following composition:

Example 1: 25% by weight polyester (PET) of KoSa, 1,7dtex / 19mm;

25 17% by weight of Polypropylene (PP) from Fibervisions, 1,7dtex / 18mm;

58% by weight of bleached sulfate pulp fibers from Korsnäs, Vigor Fluff.

Example 2: 40% by weight Polypropylene (PP) of Fibervisions, 1.7dtex / 18mm; 30 50% by weight of bleached sulfate pulp fibers from Korsnäs, Vigor Fluff.

A non-woven cleaning material produced by SCA Hygiene Products AB under the trademark E-Tork StrongTM was used as reference material. It is made by wet forming a mixture of fibers and by means of its hydro-entanglement.

35 However, no closed mesh molded plastic sieve is used, but the hydro-entanglement process is carried out in a conventional paper-making wire. The material does not have the configured three-dimensional structure claimed by the present invention, but a more uniform fiber distribution. The composition of the fibers in the reference material was as follows:

40 Ref .: 25% by weight of KoSa polyester (PET), 1,7dtex / 19mm;

17% by weight of Steen polypropylene (PP), 1,7dtex / 18mm;

58% by weight of bleached sulfate pulp fibers from Korsnäs, Vigor Fluff. Thus, the fiber composition is the same as in Ex. 1 except that PP fibers are from another manufacturer.

Evaluations were carried out in relation to the resistance properties in both dry and wet conditions, absorbency, wick rate, and the results presented in the following table 1 were obtained: 50 Table 1

Ex. 1

Ex 2 Ref.

Weight

g / m2 76.4 88.0 83.0

Thickness

 µm 623 641 357

2kPa volume

cm3 / g 8.2 7.3 4.3

MD tensile stiffness

N / m 30230 38385 57518

CD tensile stiffness

N / m 2096 6488 6689

Tensile stiffness index

 Nm / g 104 179 236

MD tensile strength, dry

N / m 3126 3061 1499

Tensile strength CD, dry

N / m 672 745 630

Traction index, dry

Nm / g 19 17 12

MD Stretch

% 28 33 13

CD stretch

% 71 Four. Five 44

Square Root Stretch (MDCD)

% Four. Five 39 24

MD breakage work

J / m2 647 714 251

CD break work

J / m2 347 238 261

Index of work at break

J / g 6 5 3

Tensile strength MD, water

N / m 2066 3028 568

Tensile strength CD, water

N / m 330 619 185

Traction index, water

Nm / g 10.8 15.6 3.9

Relative resistance, water

% 57 91 33

Tensile strength MD, surfactant

N / m 1536 3002 407

Tensile strength CD, surfactant

N / m 330 647 122

Tensile index, surfactant

Nm / g 9.3 18.2 2.5

Relative resistance, surfactant

% 49 96 fifteen

DIN absorption, water

g / g 6.0 5.1 3.9

WAT absorption rate, dir. x (CD)

Ye 0.4 0.7 1.7

WAT absorption rate, dir. Y (MD)

Ye 0.8 1.3 2.7

Dazzled damp

Part / m2 397 228 259

Tensile stiffness, tensile strength, breakage and stretching were measured according to the SCAN-P44: 81 test method.

5 DIN absorption was measured according to test method DIN 54 540, part 4, with the modification that the sample was suspended vertically during impregnation and not horizontally as in the standard method.

The WAT absorption rate was measured according to the test method SCAN-P 62:88. However, the following modification of the sample was made: instead of the objective being a total weight of between 100 and 150 g / m2 of the 10 sample sheet, the objective was a total thickness of 1 mm. No absorption speed measurements were made in the z direction.

These results show excellent resistance properties both in dry and wet conditions for nonwoven materials according to the invention. This is considered to be due to the strong network created by the artificial fibers present in the material, said network being more or less continuous. The choice of artificial fibers also plays an important role for the strength of the material, and from the test results it is seen that Example 2, which contains 40% by weight of polypropylene fibers (1.7dtex / 18mm), has better Strength properties compared to Example 1 containing a mixture of polyester and polypropylene, 25% polyester (1.7dtex / 19mm) and 17% polypropylene fibers (1.7dtex / 18mm). However, both materials have resistance

20 considerably higher, that is, tensile strength (dry, water, surfactant), stretching and breakage, compared to the reference material.

The materials according to the invention are less rigid than the reference material.

The materials according to the invention also have better absorption properties, both total absorbency and absorption rate or wick (WAT), compared to the reference material. This is considered to be due to a combination of the high concentration of pulp fibers present in the plurality of pads protruding from one side of the material, said pulp fibers pads being capable of absorbing and retaining liquid, and the fiber network predominantly artificial, said network being adapted to distribute the liquid in the

30 material

Claims (13)

1. A hydraulically entangled, non-woven, foamed or wet-lying nonwoven material containing at least 30%, by weight, of pulp fibers and at least 20%, by weight, of artificial fibers or filaments, 5 characterized in that said nonwoven material has a base weight variation in a non-random configuration, because it includes a plurality of higher base weight pads (25) protruding from a main surface of said material, said pads as a main component include pulp fibers (26) and are surrounded by a lower base weight network (27) containing a relatively higher amount of artificial fibers or filaments (28) in 10 comparison with the pads (25). 2. A nonwoven material according to claim 1, characterized because The opposite main surface of the material is substantially smooth. 3. A nonwoven material according to claim 1 or 2, characterized because it contains at least 40%, preferably at least 50%, by weight, of pulp fibers. A nonwoven material according to any one of claims 1-3, characterized in that it contains at least 30%, preferably at least 40%, by weight, of artificial fibers or filaments. 5. A nonwoven material according to any of the preceding claims, 25 characterized in that said artificial fibers are tuft fibers of a length between 6 mm and 25 mm. 6. A nonwoven material according to any of the preceding claims, characterized in that 30 has an absorption capacity of at least 5 g / g of water. 7. A nonwoven material according to any of the preceding claims, characterized in that it has an absorption rate, WAT, measured as described in the description, in MD not exceeding 1.5 s / m and 35 on CD not exceeding 2.5 s / m. A nonwoven material according to claim 7, characterized in that it has an absorption rate, WAT, measured as described in the description, in MD not exceeding 1 s / m and in 40 CD not exceeding 2 s / m. 9. A nonwoven material according to any of the preceding claims, characterized because said pads (25) have a length and width of between 0.2 and 4 mm, preferably between 0.5 and 2 mm. 10. A nonwoven material according to any of the preceding claims, characterized because the width of the net wires (27) between adjacent pads (25) is between 0.2 and 4 mm, preferably between 0.5 and 2 mm. 11. A method of producing a nonwoven material according to claim 1, including wet laying or foaming a fiber dispersion to form a fibrous sheet containing at least 30%, by weight, of pulp fibers and at least 20%, in weight, of artificial fibers or filaments, calculated on the total weight of the fibers in said fibrous sheet, and hydroentangling the fibrous sheet followed by subsequent dehydration and drying, 55 characterized in that the fibrous sheet (13) is formed in a formation wire (12) and is subjected to a first hydro-entanglement while being supported in said formation wire, and subsequently transferred to a second hydro-entanglement step that is carried out in a foraminous support element in the form of a molded closed mesh screen (16) of a thermoplastic material, said sieve holes (18) having a size in transverse dimension of 0.2-4 mm and the distance between the holes between 0.2-4 mm. 12. The method according to claim 11, characterized because the holes (18) in said sieve (16) are 0.5-2 mm in size and the distance between the holes is between 0.2-5 mm The method according to claim 11 or 12, characterized in that said additional hydro-entanglement is carried out from the opposite side of the fibrous sheet (13) in comparison with the first hydro-entanglement. 14. The method according to any of claims 11-13 characterized in that the sheet after dehydration is subjected to non-compacting drying, such as air drying, IR drying or the like. 15. The method according to claim 14, characterized because there is no pressing of the fibrous sheet during dehydration and drying.