DE29723320U1 - Liquid distribution fleece - Google Patents

Description

B/34.778 30/rl

Christian Heinrich Sandler GmbH & Co. KG, Lamitzmühle, 95126 Schwarzenbach / Saale

Liquid distribution fleece

The invention relates to liquid distribution fleeces, such as are used in particular as an intermediate layer between the cover layer and the liquid absorption layer of diapers or layer arrangements with a similar effect, absorbing liquid through the cover layer and storing it in an absorption layer. Such liquid distribution fleeces are used in particular in absorbent hygiene products, which essentially consist of a liquid-permeable cover layer facing the body, a liquid-impermeable surface layer facing the laundry and a layer between these two layers.

arranged absorbent body, whereby the liquid distribution fleece is then arranged between the cover layer and the absorbent body.

In order to be used for these purposes, liquid distribution layers or fleeces must have certain properties. The most important property is good liquid distribution in conjunction with a high liquid absorption rate, as large amounts of liquid would otherwise not be absorbed quickly enough by the absorption layer, which could lead to the hygiene product leaking. Furthermore, good rewetting behavior is required so that liquid that has been absorbed by the absorption layer is not released again and migrate towards the body. The rewetting behavior is influenced by the thickness and pressure stability of the liquid distribution fleece, among other things.

The absorption layers or absorption bodies of modern hygiene products currently contain, in addition to a matrix of mainly hydrophilic cellulose pulp fibers, a large proportion of superabsorbent, hydrogel-forming particles, so that liquid entering the absorbent core of a hygiene product can be bound very intensively. If a hygiene product does not have a liquid distribution fleece, the liquid entering the cover layer penetrates predominantly vertically, whereby a large amount of liquid is distributed over a relatively small area and as a result only the superabsorbent particles located directly under this area can take effect to bind the liquid. The superabsorbent particles located outside this area, on the other hand, remain unused.

A large surge of liquid on a small surface causes the superabsorbent particles wetted by the liquid to swell very quickly, causing a gel layer to form in the outer zone of the absorbent core of the hygiene product, which prevents the liquid from penetrating further into the interior of the absorbent core. This condition is known as "gel blocking". It prevents large amounts of liquid that occur spontaneously from being absorbed properly, which is why efforts are made to distribute a large amount of liquid that occurs spontaneously over as large an area as possible before the liquid penetrates the absorbent core, so that the superabsorbent particles in the absorbent core are used as completely as possible and the amount of liquid per unit area is as small as possible, which is intended to ensure that the so-called "gel blocking" has no or hardly any negative effects.

It is also known that the introduction of liquid into hygiene products generally takes place in a very short time and in large quantities, which is why it is necessary that the relatively large quantity of liquid is absorbed and held by the absorbent body almost immediately. It must therefore be prevented that a build-up of liquid under the cover layer occurs, since liquid that builds up would not be absorbed by the absorbent body and would run out of the hygiene product in undesirable places. In this context, it is already known (EP 0 539 703 Al) to provide the fibres of a liquid distribution layer with a hydrophilic finish. However, this finish can only fulfil its task of transporting liquid as long as it is actually on the fibres. If liquid is transported several times, there is a risk that the finish will be washed off and the hygiene products will no longer be able to absorb liquid after the second, third or even fourth application of liquid.

feel dry, as the then lubricant-free polyolefin outer layer of the fiber has a hydrophobic character and prevents the liquid from passing through to the absorbent body.

Rewetting is when a hygiene product is used to release liquid from the liquid-laden absorbent core back into the body under pressure. The aim of modern hygiene products is to keep the user's skin as dry as possible, i.e. to return as little liquid as possible to the body. A large part of the liquid in the absorbent body is held in place by the super-absorbent particles. However, the absorbent body feels moist. If the absorbent body were to be directly connected to the top layer, there would be a risk that liquid from the absorbent body would be sucked back into the top layer by capillary forces, which could lead to the top layer becoming wet. The purpose of a liquid distribution fleece is therefore also to prevent liquid from the absorbent body from being sucked back into the top layer.

Finally, all modern nonwoven fabrics should of course be able to be processed smoothly in the hygiene industry, for which the mechanical properties of the nonwovens are of great importance.

From the above explanations it is clear that a liquid distribution fleece must meet a number of possibly even contradictory requirements. On the one hand, it should ensure good liquid distribution, on the other hand, it should ensure a short penetration time for the liquid, have good rewetting properties, i.e.

prevent liquid from flowing back from the absorbent body into the cover layer and finally have good stability combined with excellent mechanical properties.

The object of the invention is now to propose a liquid distribution fleece which meets the corresponding requirements for a liquid distribution fleece explained above in as comprehensive a manner as possible.

To solve this problem, the invention proposes a liquid distribution fleece which is characterized by the following properties:

a) Fibre mixture of

- 30 to 70% polyester/copolyester biocomponent fibers and

- 7 0 to 30 % non-polyolefin staple fibres;

b) fibre titre between 3 and 20 dtex, preferably between and 14 dtex;

c) hydrophilic finishing of the fibres;

d) basis weight between 20 and 80 g/m ² , preferably between 25 and 50 g/m ² ;

e) thermal bonding by means of hot air sucked or blown through the fleece;

f) Compressibility of the fleece of less than 2.

A nonwoven fabric with the properties mentioned above has a pore size that is favorable for good liquid distribution due to the selected fiber diameter and the resulting nonwoven density taking into account the basis weight, whereby the liquid distribution can be further supported if, as is further preferred according to the invention, the fibers of the fiber mixture are predominantly oriented in the longitudinal direction of the nonwoven corresponding to the manufacturing and processing direction. It is particularly important in the fiber composition of the liquid distribution nonwoven according to the invention that no polyolefin fibers are used. Liquid transport is generally favored by the hydrophilic finish of the fibers. However, even if, which cannot be ruled out, the hydrophilic finish is largely washed away after the first or possibly second liquid exposure, at least the polyester fibers themselves still have a slight hydrophilicity, which in any case leads to a considerable acceleration of liquid transport. The liquid-repellent properties of polyolefin fibers, which are often present in such hygiene products, including in liquid distribution layers, do not have a negative effect on the fleece according to the invention because there are no polyolefin fibers present. The liquid distribution fleece according to the invention therefore still has good liquid transport properties even after several, for example even four, liquid exposures, even if the lubricant has already been rinsed off.

The use of relatively coarse and wiry fibres, also hollow fibres, as well as the type of consolidation of the fleece using polyester/copolyester bicomponent fibres in a sufficiently high proportion and the not too low

Thickness of the liquid distribution fleece means that it has good stability against compression, which results in good rewetting properties. Thermal hot air consolidation is also important here, which ensures a voluminous character of the fleece. For example, calender consolidation with a usual consolidation area of 10 to 30% would result in a lower fleece thickness, which would undesirably increase the capillarity of the product and thus increase rewetting. Overall, in order to achieve sufficient rewetting properties, the compressibility of the fleece must not be more than 2, i.e. the fleece must not be able to be compressed more than half its size under corresponding load.

Due to the corresponding proportion of polyester/copolyester bicomponent fibers, the type of thermal bonding and the other structure of the liquid distribution fleece, the nonwoven fabric also has correspondingly good mechanical properties, which ensure its smooth processing in the hygiene industry. The long running length of the nonwoven fabric rolls is also advantageous, which is obtained when the liquid distribution fleece according to the invention has a thickness of 0.3 to 3 mm, preferably 1.0 to 2.5 mm. Surprisingly, such small thicknesses are sufficient for the liquid distribution fleece according to the invention in view of its excellent properties with regard to liquid distribution, penetration time and rewetting properties.

It has proven to be advantageous if the fibres of the fibre mixture have a length of 30 to 100 mm. Such fibres can be easily processed during production and

On the other hand, they lead to excellent mechanical properties as well as good liquid distribution, whereby, as already mentioned, it is advantageous if the fibers of the fiber mixture are predominantly oriented in the longitudinal direction of the fleece, which corresponds to the manufacturing and processing direction. In any case, the individual fibers each run over a comparatively large distance in the fleece and therefore distribute the liquid well.

As bicomponent fibers, it is advantageous to use sheath/core type fibers because their use leads to a particularly good bonding of the fleece and thus corresponding mechanical strength.

In order to positively influence the mechanical strength and processing of the liquid distribution fleece in the hygiene industry, it can be useful for at least one surface of the liquid distribution fleece to be additionally thermally strengthened by the action of a heated calender roller or by a sieve drum covered with a fine covering grid. The thermal, but only superficial, strengthening understandably results in increased resistance to mechanical influences, without, however, simultaneously impairing the liquid absorption and transfer properties of the fleece.

In this context, it is particularly advantageous if the surface of the liquid distribution fleece facing the absorption layer (suction layer) during use is additionally smoothed by means of the heated calender roller or the screen drum. The compaction of the surface of the liquid distribution fleece facing the suction body caused by the smoothing particularly benefits the liquid distribution properties.

A liquid-absorbing article is already known from EP 0 539 703 A1, which contains a liquid distribution layer in which polyester-polyethylene bicomponent fibers of the sheath/core type are present. In the known material, these bicomponent fibers have a titer of less than 3 denier (3.3 dtex). PET fibers can be present as a further fiber component in the known liquid distribution fleece. However, these fibers are very difficult to bond with polyester-polyethylene bicomponent fibers, since the plastics polyethylene and polyester only form a very weak thermal bond. Due to both the low fiber strength and the poor bond, pressure-stable liquid distribution fleeces cannot be produced using a procedure according to EP 0 539 703 A1, so it can be assumed that the liquid distribution layer has only relatively poor rewetting properties in the state of the art. Furthermore, the bicomponent fibers mentioned in EP 0 539 703 Al have a polyethylene sheath, which can also be hydrophilically finished. However, there is a risk that the hydrophilic finish will wash off after the first exposure to liquid, leaving behind the bare, hydrophobic polyethylene plastic. This means that the liquid penetration times are comparatively poor after a second, third or even fourth exposure to liquid. The liquid distribution fleece described in EP 0 539 703 Al can therefore only be used as such to a relatively limited extent.

An embodiment of a liquid distribution fleece according to the invention is explained in more detail below.

·· I

10

From example

A fiber mixture of 50% polyester/copolyester bicomponent fibers of the sheath/core type with a thickness of 5.3 dtex was mixed with 50% polyester hollow fibers with a thickness of dtex and carded to a fiber web with a weight of g/m ² . The fibers were largely oriented in the machine direction. The fiber web was then fed into a screen drum dryer, which had an open drum area of 7%. The drum of the screen drum dryer was covered with a screen grid with 70% open area. Hot air with a temperature of 160 ⁰ C was used for thermal consolidation, with the fan used to move the air generating a pressure difference ρ of 25 mm WS with the fiber web present. The nonwoven fabric consolidated in this way was cooled and wound over cooling rollers and can then be fed to a manufacturing machine for hygiene articles.

To investigate the properties, the nonwoven fabric thus obtained was installed as a liquid distribution fleece between the cover layer and the absorption layer or absorbent body of a baby diaper and the properties of the nonwoven fabric were then determined as follows:

Thickness 1.2 mm

Compressibility 1.2 Penetration time

first liquid exposure 10 see.

second liquid application 23 see.

third liquid application 40 see.

In this context, compressibility is a measure of good rewetting properties. The penetration time is a measure of the liquid distribution, since the penetration time is shorter the faster the liquid applied to the hygiene product in the area of the top layer is absorbed by the absorption layer. However, the better the liquid is distributed over as large an area as possible, the faster the absorption takes place.

To illustrate the effectiveness of the liquid distribution fleece according to the invention, the penetration time was measured for a baby diaper that otherwise corresponded to the baby diaper of the embodiment, but without a liquid distribution layer.

The following values were obtained for the penetration time:

first liquid application 38 see. second liquid application 165 see. third liquid application 287 see.

From this it can be seen that the liquid distribution fleece according to the invention results in the liquid being distributed or absorbed by the absorption layer much more quickly.

The following measuring and testing methods were used to measure the properties:

Thickness:

Measurement according to DIN 53855 Tl

Compressibility:

According to the invention, this is to be understood as the ratio of the thickness measured according to DIN 53855 T2 to the thickness measured according to DIN 53855 Tl, i.e.

Compressibility =

Thickness (DIN 53855 T2) / Thickness (DIN 53855 Tl)

The thickness according to DIN 53855 T2 is measured with a preload of 0.2 cN/cm ² , the thickness according to 53855 Tl with a preload of 5 cN/cm ² . The fleece is compressed more strongly with a higher preload (DIN 53855 Tl) and consequently has a lower measured thickness. The ratio of the thickness according to DIN 53855 T2 to the thickness according to DIN 53855 Tl thus provides a measure of the stability of the fleece when force is applied to the surface.

Penetration time :

The so-called "Kanga" test from Chemische Fabrik Stockhausen, Krefeld, was used here, which is explained below using Figures 1 to 3.

The Kanga test method is used, among other things, to assess the penetration time of a hygiene product, in the example of a baby diaper.

A test body (diaper) is prepared as follows.

The cover fleece (top layer) on the diaper b is carefully removed from the absorbent body, whereby when measuring the

A commercially available diaper from Carter Holt, Harvey, NZ, brand "Treasures", type "Trim Care", size: "X-large" was used to determine the penetration time mentioned above. The liquid distribution fleece to be tested is then placed on the absorbent body in the appropriate size. A reference cover fleece (in this case type Sawabond [registered trademark of the applicant] 4302 g/m ² ) is then placed over the liquid distribution fleece and fixed to the entire diaper with adhesive tape at the edge.

The test body (diaper) b prepared in this way is now placed in the so-called "Kanga" tester c, whereby details of the test body c can be seen from the attached sketch according to Figures 1 to .

The weight load on the test apparatus is determined according to the weight class assigned to the respective diaper size (see table below):

mini diaper 4.5 kg

midi diaper 6.5 kg

maxi diaper 12.5 kg

X-large diaper 15.0 kg

Junior diaper 18.5 kg

As mentioned above, an "X-Large" diaper was used in each of the tests and a corresponding weight load of 15.0 kg.

After inserting the test diaper b into the apparatus c and applying weight, a defined liquid exposure with urine substitute fluid (0.9 %

NaCl solution), whereby the amount of liquid should be selected according to the diaper size.

mini diaper 40g midi diaper 60g maxi diaper 80g X-large diaper 100 g Junior Diaper 120g

According to the selected "X-large" diaper, a liquid quantity of 100 g was used for the test series.

The amount of liquid to be applied is added using a measuring cylinder through the filling nozzle a of the test apparatus c. The infiltration time of the liquid is measured using a stop watch from the start of addition until the test liquid has completely infiltrated the absorbent body. This time corresponds to the first penetration time.

After a waiting period of 30 minutes, a second addition of the same amount of liquid is made. The time from the start of the addition of this second amount of liquid until it has completely seeped in corresponds to the second penetration time.

After a waiting period of another 30 minutes, the third addition of the corresponding amount of liquid is finally carried out, whereby the time from the start of the addition of the third amount of liquid until it has completely seeped in corresponds to the third penetration time.

Since the test apparatus c is made of a transparent material, e.g. Plexiglas, it is possible to observe exactly how long it takes until the urine substitute fluid is completely drained from the

Filling nozzle a has disappeared, i.e. has been taken up by the diaper b or its absorbent body.

Claims (11)

B/34.788/rl Christian Heinrich Sandler GmbH & Co. KG, Lamitzmühle, 95126 Schwarzenbach / Saale Claims 1. Liquid distribution fleece, in particular for use as an intermediate layer between the cover layer and the liquid absorption layer of diapers or layer arrangements with a similar effect, absorbing liquid through the cover layer and storing it in the absorption layer, characterized by the following properties: a) Fibre blends of - 30 to 70 % polyester/copolyester biocomponent fibres and - 70 to 30 % non-polyolefinic staple fibres, b) Fiber titre between 3 and 20 dtex c) hydrophilic finishing of the fibres b) Basis weight between 20 and 80 g/m ² e) Hot air consolidation f) Compressibility of the fleece of less than 2. Liquid distribution fleece according to claim 1, characterized in that the fibers of the fiber mixture have a length of 30 to 100 mm. 3. Liquid distribution fleece according to claim 1 or 2, characterized in that the bicomponent fibers are of the sheath/core type. 4. Liquid distribution fleece according to one of the preceding claims, characterized in that the non-polyolefin staple fibers are polyester fibers. 5. Liquid distribution fleece according to one of the preceding claims, characterized in that the non-polyolefinic staple fibers are hollow fibers. 6. Liquid distribution fleece according to one of the preceding claims, IQ characterized in that the fiber titer of the fiber mixture is between 5 and dtex. 7. Liquid distribution fleece according to one of the preceding claims, characterized in that the basis weight is between 25 and 50 g/m ² . 8. Liquid distribution fleece according to one of the preceding claims, characterized in that at least one surface of the liquid distribution fleece is thermally consolidated as a result of the action of a heated calender roller or a sieve drum covered with a fine covering grid. 9. Liquid distribution fleece according to claim 8, characterized in that the surface of the liquid distribution fleece facing the absorption layer during use is smoothed by means of the heated calender roller or the sieve drum. 10. Liquid distribution fleece according to one of the preceding claims, characterized by a thickness of 0.3 to 3 mm, preferably 1 to 2.5 mm. 11. Liquid distribution fleece according to one of the preceding claims, characterized in that the fibers of the fiber mixture are predominantly oriented in the longitudinal direction of the fleece corresponding to the manufacturing and processing direction.