DE102018000854B4 - Liquid absorption fleece and distribution fleece for hygiene articles - Google Patents

Abstract

Multi-layer nonwoven for absorbing and distributing liquids for hygiene products, which has an upper side, which in hygiene products faces the user, and an underside, which in hygiene products is attached to the absorbent body, the underside consisting of a nonwoven fabric, the fiber mixture of which consists of 50 to 80 percent by weight consists of absorbent fibers and 50 to 20 percent by weight melt fibers and the upper side consists of a non-woven fabric whose fiber mixture consists of 50 to 100 percent by weight melt fibers and 50 to 0 percent by weight matrix fibers, the fiber mixture of the non-woven fabric forming the underside has a lower average fiber titer than the fiber mixture of the upper side forming non-woven fabric, the upper side is exclusively thermally melt-bonded to the lower side and the liquid absorption non-woven fabric and distribution non-woven fabric has a density of 35kg/m3 or less, characterized in that• the upper side has an average denier of the F fiber mixture > 4.0 dtex, a thickness > 0.002m and a weight > 0.04kg/m2,• the underside has an average titer of the fiber mixture <6.0dtex, a thickness < 0.001m and a weight < 0.06kg/m2, • the thickness of the upper side is at least 60% of the total thickness,• the density of the lower side is at least twice the density of the upper side and• the average fiber titre of the upper side is at least 2.0 dtex higher than the average fiber titer of the lower side .

Description

• • Erste Lage: Topsheet (Lochfolie oder Vlies)
• • Zweite Lage: Acquisition and Distribution Layer, „ADL“ ( zumeist aus Vlies)
• • Dritte Lage: Saugkern (bestehend aus Zellstoff und/oder Polyacrylsäure fixiert in einer oder mehreren Fixierlagen (SMS, ..)
• • Abschlusslage: Folie, um ein Austreten der Flüssigkeit auf der Rückseite zu unterbinden

Disposable articles for hygiene applications such as sanitary napkins, diapers and incontinence products have the purpose of conducting body fluids away from the skin as quickly as possible in order to avoid skin irritation and to give the user a safe and comfortable feeling. For this purpose, hygiene products are generally structured as follows:

• • First layer: Topsheet (perforated foil or fleece)
• • Second layer: Acquisition and Distribution Layer, "ADL" (mostly made of fleece)
• • Third layer: absorbent core (consisting of cellulose and/or polyacrylic acid fixed in one or more fixing layers (SMS, ..)
• • Closing layer: film to prevent liquid from escaping on the back

The layers of topsheet, ADL and absorbent core must be coordinated with each other in order to guarantee a function in the hygiene product.
The most important role is played by the ADL as a transfer layer. This must absorb the liquid from the top sheet (drainage of the top sheet), distribute the liquid in the longitudinal direction of the product and temporarily store it. The temporary storage is intended to prevent so-called gel blocking of the polyacrylic acid powder. After the brief interim storage, the liquid is passed on to the absorbent core for final storage.

• • Schnelle Aufnahme und Weiterleitung der Flüssigkeit
• • Zwischenspeicherung zur Pufferung der begrenzten Aufnahmegeschwindigkeit des Absorbermaterials
• • Gerichtete Verteilung der Flüssigkeit zur möglichst großflächigen Aufnahme durch das Absorbermaterial
• • Kontrollierte Abgabe der Flüssigkeit an das Absorbermaterial um lokale Verblockung und Flüssigkeitsstau zu vermeiden.

In order to achieve this goal, acquisition and distribution layers (ADL for short) made of nonwovens are used, which are intended to take on the following functions:

• • Rapid absorption and transfer of the liquid
• • Intermediate storage to buffer the limited absorption speed of the absorber material
• • Directional distribution of the liquid for absorption over the largest possible area by the absorber material
• • Controlled delivery of the liquid to the absorber material to avoid local blockage and liquid accumulation.

The most important properties of an absorption and distribution fleece are thickness, density and the resulting pore sizes as well as capillarity. The absorption and distribution behavior is significantly influenced by these properties.

Depending on the product, airlaid, high-loft and spunlace nonwovens are used here. In the registration DE 10 2012 015 219 A1 various designs of spunlace nonwovens are described which have corresponding properties.

The types of fleece described in the prior art are primarily single-layer structures with homogeneously distributed fiber types. Depending on the manufacturing method, only one required property can be achieved at a time. For example, high-loft nonwovens, i.e. nonwovens bonded purely thermally using melt fibers, offer a high thickness and associated good liquid absorption due to their structure. Due to the comparatively high porosity, however, the distribution effect is very low. As a result, only a very limited use of the underlying absorbent core is possible.

The nonwovens produced using the airlaid process have a good distribution effect thanks to the fine capillaries. Due to the high cellulose content, however, the thickness is low and the liquid is released back to the surface, which results in a high rewet.

Two-layer structures that come from a one- or two-stage manufacturing process, such as in the DE 10 2016 005 158 A1 , are also not effective. The layers are connected by means of water jets, so that, for example, hydrophilic agents are washed off, so that the liquid absorption is insufficient. Furthermore, due to the type of consolidation, the resulting final thickness is insufficient, since the ADL side in particular can only absorb little liquid.

A connection of the layers in multi-layer structures by means of adhesives such as hotmelt via spray coating or slot coating results in sufficient adhesion of the layers, but the Hotmelt impedes liquid transfer. Areas blocked with hotmelt that are impermeable to liquid form at the transitions between the layers.

Prior art materials according to the preamble of claim 1 are from the references DE 299 13 054 U1 , U.S. 5,531,727 A and EP 0 521 016 B1 known. They combine the properties of liquid distribution and liquid absorption, although compromises in the respective effect have to be accepted.

the EP 0 521 016 B1 describes the thermal calender bonding of a lightweight first layer to a second layer containing natural hydrophilic fibers. Due to the calendering, the two-layer structure has a low thickness in the range of 0.2-0.3mm. The buffer effect, in "Table 1" of the EP 0 521 016 B1 referred to as surface rewet, is therefore only low.

the U.S. 5,531,727 A describes a multi-layer nonwoven fabric made entirely of non-absorbent fibrous materials. Furthermore, the average fiber titer of the individual layers decreases from layer to layer. The disadvantage here is that the liquid intake is low due to the lack of suction components.

the DE 299 13 054 U1 suggests the use of airlaid materials on the underside. Due to the high cellulose content, the liquid is released back to the surface, which results in a high rewet.

The object of the present invention is therefore to provide a material which avoids the stated disadvantages of the prior art and has improved liquid absorption with simultaneous liquid distribution.

The object is achieved by the features specified in claim 1; useful configurations can be found in claims 2 and 3.

This is achieved in that the nonwoven fabric is produced in its vertical structure, ie perpendicular to the plane of the layer, with the upper side and the lower side having a different fiber composition and possibly also a different type of bonding. As a result, each side can be designed in such a way that the respective function is optimally fulfilled by the fiber mixture and/or the type of bonding.

According to the invention, the layers are bonded exclusively thermally, with the fiber mixture on the upper side having a proportion of more than 50 percent by weight of fusible fibers. This ensures that a sufficient number of binding points are formed between the upper side and the lower side.

The transition between the zones also creates a gradient in the physical properties, so that the upper side has the greatest permeability and mechanical stability, while the lower side facing the absorbent core has the greatest capillarity. Due to the gradient, the liquid is transported quickly and almost completely away from the side of the body and forced by physical forces to the absorbent core.

• Textile Faserstoffe weisen zur Verbesserung der Verarbeitungseigenschaften aber auch zur Gewährleistung bestimmter Effekte im Fertigprodukt sogenannte „Avivagen“ auf der Faseroberfläche auf.

Some of the terms used in the following description are defined in more detail below:

• Textile fiber materials have so-called "finishes" on the fiber surface to improve the processing properties but also to ensure certain effects in the finished product.

An "absorptive fiber" within the meaning of the present invention is a regenerated cellulose fiber which is produced from solutions of cellulose derivatives. This viscose fiber can have a surface modification, e.g. trilobal cross-section, but also be modified overall in such a way that moderate liquid absorption is promoted while at the same time good liquid storage. Representatives according to the invention are, for example, Viscostar viscose fibers or normal viscose fibers from the manufacturer Lenzing, but also the so-called Galaxy fibers from Kehlheim Fibers. In particular, viscose fibers which are produced using the Lyocell process (Tencel from Lenzing) can also be used. Customary fiber finenesses are in the range from 1.0 to 3.3 dtex, preferably 1.3 to 2.2 dtex. If staple fibers are used, the fiber lengths used are in the range of 10-70 mm, preferably between 35-50 mm. The absorbent fibers have standard crimps. However, if the underside is an airlaid, the term absorbent fiber can also refer to short fibers or pulp.

The term “matrix fiber” is used in the context of the present invention for staple fiber materials made from thermoplastic and/or duroplastic polymers contained in the upper side. Fibers made from thermoplastic polymers such as polyester or polypropylene are preferred. The melting temperature must be at least 10°C above the melting fibers used.
However, duroplastic polymers such as polyacrylic fibers are also suitable. The fiber fineness is in the range from 3.3 to 17 dtex, preferably 4.4 to 10.0 dtex; the fiber lengths used are in the range of 10-80 mm, preferably 35-60 mm. The distribution fibers have standard 2D or 3D crimps.

The terms “finish” or “finish” designate a functional finish/coat on fiber surfaces. These finishing agents are used commercially as processing aids, i.e. fibers are treated in such a way that static charging is prevented, particularly in the case of PP or PE fibers. Finishing agents are usually used on the surface of staple fibers. The type of finishing agent selected can affect the hydrophilicity or hydrophobicity, which can have a major impact on the properties of the liquid absorption nonwoven and distribution nonwoven. The finishing agents are present on the surfaces of the melting fibers as well as on the matrix fibers and the absorbent fibers.

• • den Verbund der Oberseite mit der Unterseite den Faserverbund ermöglichen
• • die Struktur der Oberseite stabilisieren, sodass ein weitestgehend dimensionsstabiles Vlies entsteht.

“Fusable fibers” within the meaning of the present invention are fibers that are present in a product constructed according to the invention

• • enable the connection of the upper side with the underside of the fiber structure
• • Stabilize the structure of the upper side so that a largely dimensionally stable fleece is created.

Fusible fibers are homo- or bi-component, thermoplastic polymer fibers that have fusible parts. When temperature is applied, these parts melt and stabilize the fiber composite after cooling. Fibers suitable according to the invention are homopolymeric staple fibers made of copolyester, copolyamide or polypropylene; bicomponent melt fibers in a core-sheath or side-by-side arrangement made from combinations of low-melting copolyester with polyester, polyethylene with polypropylene or polyethylene with polyester are preferred according to the invention . The fiber counts for the melt fibers used in the upper side are in the range from 2.2 to 12 dtex, preferably 4.4 to 6.7 dtex; the fiber lengths used are in the range of 10-8 mm, preferably 35-60 mm.

The fiber counts for the melt fibers used in the underside are in the range from 1.7 to 3.3 dtex, preferably 1.7 to 2.2 dtex; the fiber lengths used are, when using staple fibers in the range of 10-80 mm, preferably 35-60 mm, when using short fibers, the underside should be formed by an airlaid fleece, between 1 and 5 mm, preferably 3 mm. If the fusible fibers are staple fibers that can be carded, they have commercially available crimps.

Nonwovens according to the invention are produced using dry or wet processes; the underlying processes can be found in the book “Vliesstoffe” published in 2000 by Wiley VCH-Verlag, Weinheim.

In particular, the non-woven fabric forming the underside can be an air-laid non-woven fabric, a so-called “airlaid”. Carded staple fiber nonwovens are preferred according to the invention.

The fibers used are homogeneously mixed with one another to create a fiber mixture. The basic techniques for this are also shown in the book "Vliesstoffe".

According to the invention, the “top side” is the side that faces the user in the hygiene product and on which the liquid first impinges.

The "underside" is the side of the nonwoven fabric according to the invention that is attached to the absorbent body in the hygiene product.

"Precursor" refers to a prefabricated fleece that has already gone through the process steps of fiber mixing, fleece formation and fleece consolidation. According to the invention, the underside is formed by a precursor.

The examples below relate to, but are not limited to, staple fiber nonwoven fabrics made by dry processes using the carding process.

• • Flächengewicht gemäß WSP 130.1., Angabe in kg/m²
• • Dicke gemäß WSP 120.6, Abschnitt 7.2, Messdruck 1 bis 5 mm, bevorzugt 3 mm., Angabe in m
• • Trennfestigkeit gemäß NWSP401.0.RO(15), Angabe in N
• • Dicke der Oberseite wird gemäß folgender Formel ermittelt: $$\text{Dicke Oberseite}\left(\text{m}\right)=\text{Gesamtdicke}\left(\text{m}\right)-\text{Dicke Precursor}\left(\text{m}\right)$$
  
• • Dichte gemäß folgender Formel: $$\text{Dichte}\left(\text{kg}/{\text{m}}^3\right)=\frac{\text{Fl}\ddot{\text{a}}\text{chengewicht}\left(\text{kg}/{\text{m}}^3\right)}{\text{Trockendicke}\left(\text{m}\right)}$$
  
• • Strike Through gemäß WSP 70.3, Angabe in s
• • Rewet gemäß WSP 80.10, Angabe in g
• • Mittlerer Fasertiter innerhalb einer Lage: errechnet sich nach folgender Formel $$\text{Mittlerer Fasertiter}\left(\text{dtex}\right)=\frac{\text{A}*\text{Titer 1}+\text{B}*\text{Titer 2}+\text{C}*\text{Titer}3}{100}$$
  

A,B,C = Prozentanteil einer Faserkomponente in der Mischung, wobei die Summe aus A, B, und C = 100 ist.
Titer 1,2,3 = nominaler Titer der jeweiligen Faserkomponente in dtexIn addition, Table 1 lists the test results obtained in each case. The parameters determined were determined according to the test methods listed below:

• • Weight per unit area according to WSP 130.1., information in kg/m ²
• • Thickness in accordance with WSP 120.6, section 7.2, measuring pressure 1 to 5 mm, preferably 3 mm. In m
• • Separation strength according to NWSP401.0.RO(15), specified in N
• • Thickness of the top side is determined according to the following formula: $$\text{thick top}\left(\text{m}\right)=\text{overall thickness}\left(\text{m}\right)-\text{thick precursors}\left(\text{m}\right)$$
  
• • Density according to the following formula: $$\text{density}\left(\text{kg}/{\text{m}}^3\right)=\frac{\text{bottle}\ddot{\text{a}}\text{little weight}\left(\text{kg}/{\text{m}}^3\right)}{\text{dry thickness}\left(\text{m}\right)}$$
  
• • Strike Through according to WSP 70.3, information in s
• • Rewet according to WSP 80.10, given in g
• • Mean fiber titre within a layer: calculated using the following formula $$\text{Mean fiber count}\left(\text{dtex}\right)=\frac{\text{A}*\text{titer 1}+\text{B}*\text{Titer 2}+\text{C}*\text{titer}3}{100}$$
  

A,B,C = Percentage of a fiber component in the blend, where the sum of A, B, and C = 100.
Titer 1,2,3=nominal titer of the respective fiber component in dtex

The required properties, i.e. rapid liquid absorption, good distribution with short-term intermediate storage and transfer to the absorbent core, are achieved according to the invention by a structure of two bonded fleece layers.

• • Herstellen einer Fasermischung für den Precursor, bestehend aus Saugfaser unter Zumischung von Schmelzfaser
• • Herstellen einer unverfestigten Materialbahn aus der Fasermischung des Precursors
• • Thermisches und/oder mechanisches Verfestigen der Materialbahn, sodass der Precursor mit einer Dichte von 50 bis 200 kg/m³ und einer Dicke von 0,4 bis 1,0 mm entsteht.
• • Optional: Aufwickeln des Precursors
• • Herstellen einer Fasermischung für die Oberseite, bestehend aus Matrixfaser und Schmelzfaser
• • Herstellen einer unverfestigten Materialbahn aus der Fasermischung der Oberseite
• • Ablegen der unverfestigten Materialbahn auf dem Precursor
• • Verfestigung der Oberseite und Verbindung der Oberseite mit dem Precursor mittels einer Heißluft-Behandlung.
• • Optional: Zusätzliche Passage eines Kalanders zur Stabilisierung des Verbundes. Die Verfestigungsfläche soll weniger als 10%, bevorzugt weniger als 7% betragen.
• • Wickeln des erfindungsgemäßen Flüssigkeitsaufnahmevlies und - verteilervlieses

A liquid absorption fleece and distribution fleece produced according to the invention goes through the following process steps:

• • Production of a fiber mixture for the precursor, consisting of absorbent fibers with the admixture of melting fibers
• • Production of a non-solid material web from the fiber mixture of the precursor
• • Thermal and/or mechanical hardening of the web of material so that the precursor is produced with a density of 50 to 200 kg/m ³ and a thickness of 0.4 to 1.0 mm.
• • Optional: Winding up the precursor
• • Making a fiber mix for the top, consisting of matrix fiber and fusible fiber
• • Production of an unconsolidated material web from the fiber mixture of the upper side
• • Depositing the unconsolidated web of material on the precursor
• • Solidification of the upper side and connection of the upper side to the precursor by means of a hot air treatment.
• • Optional: Additional passage through a calender to stabilize the composite. The solidification area should be less than 10%, preferably less than 7%.
• • Winding of the liquid absorption fleece and - distribution fleece according to the invention

According to the invention, the nonwoven fabric forming the underside consists of a precursor which has a content of 50 to 100% by mass of absorbent fibers. Fiber mixtures are used in the precursor, which have a difference in the average fiber titre of the precursor and the upper side. According to the invention, the difference must be at least 2 dtex, with the mean fiber titre of the fiber mixture of the precursor having to be lower than that of the upper side.

The average fiber titre of the fiber mixture of the precursor is in the range from 1.0 to 6.0 dtex, with this preferably being less than 4 dtex and most preferably less than 2.0 dtex.

If the precursor is produced, as is preferred according to the invention, as a carded staple fiber fleece, the fibers are oriented in the manufacturing direction of the fleece. This orientation is advantageous for later use, since the fiber orientation then also runs in the longitudinal direction of the finished hygiene product. This improves the utilization of the available suction surface in the hygiene product.

During the solidification of the precursor, which according to the invention preferably, but without being limited to this, occurs by means of water jets, the precursor is simultaneously compacted, so that the density of the precursor is higher than that of the final absorption and distribution nonwoven. Precursor densities of 50 to 200 kg/m³, preferably 80 to 120 kg/m³, are provided, with the thickness range of the precursor being between 0.4 and 1 mm and a weight per unit area of 0.025 to 0.120 kg/m² being aimed for.

The capillary effect and thus the ability to transport liquid within the precursor is positively influenced due to the selected average fiber titer of the precursor in connection with the compaction during the solidification of the precursor.

According to the invention, an unconsolidated, carded fibrous web is then laid down on this precursor. After a subsequent strengthening and bonding step, this fibrous web forms the upper side of the nonwoven fabric according to the invention.

According to the invention, the fibrous web of the upper side is bonded and the bond between the upper side and the precursor is carried out by means of thermal treatment, i.e. by means of hot-air bonding and an optional subsequent calender bonding. The basic techniques can be found in the book "Vliesstoffe", published by Wiley-VCH in 2012, pages 375-395.

The fibrous web on the upper side consists of 50 to 0 percent by weight matrix fibers and 50 to 100 percent by mass melt fibers.

According to the invention, a proportion of more than 50% fusible fibers is necessary in the fiber mixture that forms the upper side. This proportion is significant compared to the prior art and ensures a sufficient number of possible binding points between the top and bottom.

If the unconsolidated fibrous web, which forms the upper side after solidification, is placed on the underside, there are only a few points of contact at the boundary layer between the upper and lower side, which can fuse or form bonding points after hot air treatment.

It is therefore necessary and preferred according to the invention, but without being restricted thereto, for the hot-air bonding to provide a system which works according to the through-flow principle. Hot air hits the initially unconsolidated fibrous web on the upper side and flows through the upper side, followed by the underside. Depending on the amount of hot air flowing through and the flow rate, the fibrous web on the upper side experiences less or greater compression compared to the thickness of the unconsolidated fibrous web.

By means of this compaction, a significantly larger number of contact points and therefore possible binding points of melt fibers are formed on the boundary layer from top to bottom compared to simply "placing" the fiber web and solidifying it by means of jets or radiant heat.

Fusible fibers are used in the fiber blend of the bottom to ensure top-to-bottom adhesion. This is because the connection between fusible fibers is facilitated and such binding points of fusible fibers from the top to the bottom are mechanically more stable.

The hot-air consolidation and connection has proven to be particularly advantageous with regard to the finishing of the fibers on the upper side. If a composite is created by means of water jet turbulence, the finishing agent present on the fibers is almost completely washed off by the water jets. The fiber or fleece properties achieved by means of finishes are changed as a result, so that requirement profiles are not met can become. The finishes remain on the fiber surfaces due to the hot-air bonding and connection and the properties are not affected.

For the precursor, the upper limit for the content of melt fibers is 50 percent by weight, since the storage of liquid suffers with proportions greater than 50 percent by weight and, on the other hand, the precursor becomes too stiff.

According to the invention, it is also possible with preference to use similar melt fibers, i.e. made from the same polymers, so that the adhesion from top to bottom is improved.

In another preferred embodiment, particularly in the event that only absorbent fibers are contained in the precursor, a melt fiber type can be used which has a particular affinity for cellulosic polymers.

The average linear density of the fiber mixture on the upper side is greater than 3.3 dtex, preferably in the range from 4.4 to 12 dtex and particularly preferably in the range from 6.7 to 12 dtex. Due to this average fiber titer, the fleece forming the upper side is open enough to absorb liquid quickly and store it temporarily until it is passed on to the underside. The higher the mean fiber diameter of the blend, the better the surface's resistance to compressive loads. With increasing proportions of fusible fibers, the upper side also becomes mechanically more stable, i.e. has improved resistance to compression such as high packing densities of diapers or to point loads during use. The rewet is positively influenced with higher average fiber titres and with a melt fiber content of more than 75 percent by weight.

The stability of the upper side in particular is ensured by thermal activation of the melting fibers. This ensures improved resistance to the aforementioned compression in the product application.

According to the invention, the solidification conditions in combination with the fiber mixture of the upper side are selected in such a way that the liquid absorption fleece and liquid distribution fleece according to the invention has a thickness of more than 3 mm, preferably more than 5 mm.

In the event that the proportion of fusible fibers in the fiber mixture that forms the underside is less than 30 percent by weight, an optional thermal calender treatment can be provided to improve the adhesion from the top to the underside. Adhesion is determined via the separation strength.

In order not to influence the thickness of the liquid absorption fleece and distribution fleece, the arrangement of the calender and the calender engraving must be selected accordingly.

The gravure roller must be arranged in such a way that the embossing occurs on the upper side. On the one hand, the engraved roller must have a pressing surface of less than 10%, preferably less than 7%, and on the other hand the web height, ie the distance from the base of the engraving to the pressing plateau, must be greater than 2 mm. According to the invention engravings are used, which if not formed as lines having less than 10 points per cm ² engraving are particularly preferred engravings with engraving 7 or less dots per cm ^2.

The liquid absorption nonwoven and distribution nonwoven according to the invention has an open, mechanically stable nonwoven structure on the upper side to ensure liquid absorption and a compressed lower side for distribution in order to absorb liquids and distribute them due to capillarity.

• • Mittleren Titer der Fasermischung > 4,0 dtex
• • Dicke der Oberseite > 0,002 m
• • Gewicht der Oberseite > 0,04 kg/m²

The requirements on the upper side are achieved by:

• • Average titer of the fiber mixture > 4.0 dtex
• • Thickness of top > 0.002 m
• • Top weight > 0.04 kg/m²

• • Mittleren Titer der Fasermischung < 6,0 dtex
• • Dicke der Unterseite < 0,001 m
• • Gewicht der Unterseite < 0,06 kg/m²

The requirements for the underside are achieved by:

• • Average titer of the fiber mixture < 6.0 dtex
• • Underside thickness < 0.001 m
• • Underside weight < 0.06 kg/m²

• • Anteil der Schmelzfasern > 50 Gewichtsprozent in der Fasermischung der Oberseite
• • Anteil der Schmelzfasern von 20- 50 Gewichtsprozent in der Fasermischung der Unterseite
• • Anwendung von Heißluftbehandlung mit Luftströmung von Oberseite durch Unterseite.
• • Optionale Anwendung einer nach der Heißluftbehandlung sich anschließenden Kalanderbehandlung.

The requirements for top-to-bottom bonding, where top-side thickness is not significantly affected, are met by providing

• • Percentage of fusible fibers > 50% by weight in the fiber mixture of the upper side
• • A proportion of melt fibers of 20-50% by weight in the fiber mixture on the underside
• • Use of hot air treatment with top through bottom air flow.
• • Optional application of a calender treatment following the hot air treatment.

• • Die Dicke der Oberseite hat einen Anteil von mindestens 60% der Gesamtdicke
• • Die Dichte der Unterseite ist mindestens doppelt so hoch wie die Dichte der Oberseite
• • Der mittlere Fasertiter der Oberseite muss mindestens 2,0 dtex größer sein als der mittlere Fasertiter der Unterseite.
• • Die Dichte des Flüssigkeitsaufnahmevlies und -verteilervlies beträgt maximal 35kg/m³

The combination of the features of the upper side with the lower side results in a liquid absorption fleece and liquid distribution fleece designed according to the invention having the following features:

• • The thickness of the top is at least 60% of the total thickness
• • The density of the bottom is at least twice the density of the top
• • The average fiber titer on the upper side must be at least 2.0 dtex greater than the average fiber titer on the underside.
• • The density of the liquid absorption fleece and distribution fleece is a maximum of 35kg/m ³

If you look at Table 1, you can see the following:

The pattern 1 represents a according to the DE 10 2016 005 158 A1 manufactured prior art liquid acquisition nonwoven and distribution nonwoven. The connection of the top with the bottom is done by water jets. Although an average fiber titer of 6.2 dtex on the upper side and an average fiber titer of 2.2 dtex on the underside, the thickness is 0.00178 m due to the compression of the water jets. The strike-through is 9.4 s.

Samples 2 to 5 were treated by means of hot air bonding in a belt dryer. For the underside, a fleece that had already been solidified by means of water jets was used as a precursor. According to the invention, the unconsolidated fibrous web was then placed on this fleece forming the underside and the fibrous web was consolidated, so that the upper side was formed. The bond from top to bottom was done by directing the hot air from the top towards the bottom. The dryer temperatures used depend on the type of polymer and melt viscosity. Samples 2 through 5 used temperatures ranging from, but not limited to, 120 to 140°C.

If you look at sample 2 designed according to the invention, which was produced with identical fiber mixtures on the top side according to sample 1, with the top and bottom being joined according to the invention by means of hot air on a flat belt dryer, you can see that the total thickness is 3 times higher compared to the sample 1 lies. The lower compression of the upper side and also the presence of hydrophilic finish on all fibers of the upper side result in an improved strike through compared to the prior art. The separation strength is on an acceptable level, ie the connection from top to bottom is maintained during processing. The difference in the average fiber titer from the top to the bottom is 4.5 dtex. Sample 1 has the same difference in denier, but the top side has a significantly lower thickness compared to the top side of sample 2.
The use of matrix fibers with a very high titre, ie 10 dtex, ensures the high thickness of the upper side of sample 2. This ensures a very high porosity. The density of sample 2 according to the invention is 17 kg/m ³ , which is 3.8 kg/m ³ lower than sample 1.

In the case of the sample 3 produced according to the invention, the use of matrix fibers is dispensed with. The proportion of fusible fibers is 100 percent by weight. The porosity of the upper side results from the difference in the average fiber titre of the mixture from the upper side to the lower side of 3.1 dtex. Due to the melt fiber content of 100 percent by weight, the separation strength is on a higher level compared to sample 2. The difference in the average fiber titre top to bottom is 33.1 dtex in sample . StrikeThrough and also Rewet are in a pattern 2 range. The density is 29 kg/m³, which is almost twice as high as sample 2. This higher density requires a slightly higher intake.

Sample 4 provides for the use of only 20% by weight fusible fibers in the underside compared to Samples 2 and 3. The layer adhesion is therefore significantly lower compared to samples 2 and 3, so that this proportion of melt fibers on the underside defines the lower limit.

In sample 5, a calender treatment subsequent to hot air bonding was carried out. A calender engraving was used, which has a pressing area of 5% and 9 figures/cm ² with a web height of 2 mm. The pressure was 75 daN/cm, the roller temperature 125°C. The gravure roller presses on the top.

In addition to a positive influence on layer adhesion, there is also a slight increase in capillary action on the top surface. This favors a directed transfer of liquid.

If you look at sample 5, where the average fiber titre of the upper side is 4.4 dtex, there is a higher density compared to samples 2 to 4 designed according to the invention, but the strikethrough and also the rewet are in the range of samples 2 to 4 .

In further embodiments of the invention, calender engravings in the form of lines can be similar to that DE 101 03 627 A1 come into use. Here, too, it should be noted that the web height is 2mm and higher and the pressing area is less than 10%.

Claims (3)

Multi-layer nonwoven for absorbing and distributing liquids for hygiene products, which has an upper side, which in hygiene products faces the user, and an underside, which in hygiene products is attached to the absorbent body, the underside consisting of a nonwoven fabric, the fiber mixture of which consists of 50 to 80 percent by weight consists of absorbent fibers and 50 to 20 percent by weight melt fibers and the upper side consists of a non-woven fabric whose fiber mixture consists of 50 to 100 percent by weight melt fibers and 50 to 0 percent by weight matrix fibers, the fiber mixture of the non-woven fabric forming the underside has a lower average fiber titer than the fiber mixture of the upper side forming nonwoven, the upper side is exclusively thermally melt-bonded to the underside and the liquid absorption nonwoven and distribution nonwoven has a density of 35kg/m ³ or less, characterized in that • the upper side has a medium denier d he fiber blend > 4.0 dtex, a thickness > 0.002m and a weight > 0.04kg/m ² , • the underside has an average titre of the fiber blend <6.0dtex, a thickness < 0.001m and a weight < 0.06kg /m ² , • the thickness of the upper side is at least 60% of the total thickness, • the density of the lower side is at least twice as high as the density of the upper side and • the average fiber titer of the upper side is at least 2.0 dtex higher than the mean fiber titer of the underside is. Multi-layer liquid absorption fleece and distribution fleece claim 1 , characterized in that - the upper side is thermally fused to the lower side by a hot air treatment or - the upper side is thermally fused to the lower side by a hot air treatment and with a downstream calender treatment. Multi-layer nonwoven for absorbing and distributing liquid according to one of the preceding claims, characterized in that - the melt component of the melt fibers in the upper side and the lower side consist of the same polymers.