Absorbant disposable article.

(42) Date of commencement of the patent: 15. 5. 1993 (45) Date of issue: 27.12.1993

<td>(30) Priority:</td><td>(73) Patent owner:</td>

<td>27.11.1980 DE 3044631 claims.</td><td>CARL FREIBENBERG D-6940 WEINHEIM (DE).</td>

<td>(56) Documents:</td><td></td>

<td>DE-0S2740184</td><td></td>

(54) VOIDABLE DISPOSABLE ARTICLES £ 23

AT 396 867

CTsesrasis

The invention relates to a disposable absorbent article, in particular for use in the field of medicine and hygiene, consisting of a cellulose-containing absorbent layer and a cover layer of synthetic fibers disposed thereon, which is provided to improve the primary transport of the liquid to be absorbed in the direction of the absorbent layer with a wetting agent

Absorbent disposable articles of the aforementioned type are known They are used in various hygienic and medical fields for use. For example, disposable diapers made of an absorbent layer consisting essentially of pulp are covered on the surface with a well covering and strong nonwoven fabric made of synthetic fibers. Similar sanitary napkins and tampons and surgical tampons are similarly constructed. Furthermore, multilayer fabrics (composites) are known in which absorbent layers are covered outwardly with a nonwoven fabric, the multi-layered forms being disposable towels, wipes, etc. be used in the household in industry or in the clinical field. Finally, such nonwovens are also used as materials for the manufacture of disposable clothing for clinical use or else for other purposes

Nonwoven fabrics used as covering materials in such disposable articles must be mechanically hermetic, have sufficient opacity and conformability. In addition, it is essential that the cover nonwovens allow adequate transport of aqueous liquids or vapors into the absorbent layers. Both conditions are fulfilled in the cover layer of the disposable article according to DE-OS 27 40184 described at the outset. However, the wicking of the cover layer is effective both in the direction of the suction layer and in the direction of the surface due to the wetting agent contained. The latter then feels wet through because the absorbent layer is also wet. That is not wanted

Wicking refers to the ability of the cover layer to be wettable by liquid and at the same time to transfer the liquid due to capillary action. If the wicking is not sufficient, the removal of the liquid is not guaranteed and the suction properties of the product are inadequate.

In hygienic and medical multi-layer structures usually a Wicktwiikung, similar to that in the disposable article according to DE-OS 27 40 184 not, because it is necessary that the return transport of the liquid subsequently stored in the absorbent layer is largely prevented to the outside, so that a "dry" impression is created The wicking in the opposite direction must therefore be reduced, if not completely calf. This means that the two requirements - the primary transport and then the savings - are in themselves in stark contrast to each other.

The invention is based on the object to develop a disposable absorbent article that meets both requirements optimally. The liquid should be dissipated very quickly into the absorbent layer, with a return transport is not or only slightly.

This object is achieved according to the invention in a disposable article of the type mentioned above in that the wetting agent is transportable from the liquid to be absorbed out of the cover layer and into the absorbent layer and that the wetting agent of cellulose is chemosorbable in order to achieve a saving effect in the reverse direction after completion of the primary transport. Surprisingly, it has been found that the completely contradictory requirements of a rapid primary transport towards the absorbent pad and a blocking effect in the opposite direction are optimally fulfilled in this way.

For a good wicking, it is necessary that the nonwoven surface or the surface of the nonwoven forming fibers is first wetted by the liquid. As is known, most synthetic polymers have a relatively low surface energy, whereas water and most aqueous liquids are characterized by a relatively high interfacial energy (72.7 × 10 -4 N / m). The interfacial energy of the most important fiber-forming polymers is given in the following table

<td colspan="2"></td><td colspan="2">* 2 Interface magic (10 N / m)</td>

<td>polyethylene terephthalate polyamide polypropylene</td><td>critical 47.3 47.0 33.2</td><td>from that: polar part 4.1 62 0.0</td><td>disperse fraction 43.2 40.8 332</td>

The value of the interfacial energy is given as critical interfacial energy, which a liquid can reach at the most while still moistening the surface. The disperse fraction of the interfacial energy is called the total surface energy. which comes only from dispersion forces, whereas as the polar part the part is mentioned, based solely on polar interactions Water is thought to that there overwhelming part - about 2/3 - on the polar and only about 1/3 on the disperse

-2AT396 867B

Interactions is due

The wicking depends on the capillarity of the porous material and its surface energy in relation to that of the liquid to be transported. A difference in surface energies has the effect of decreasing porosity. For a given porous material can thus be the

Improve wicking by increasing the critical interfacial energy value and adapting it to the value of the aqueous liquid to be transported. This can be z. B. by treatment of the nonwoven or fiber surface with surfactants. As effective Tensinde, which have a sufficient adsorption capacity on the polymer surfaces are known per se nonionic surfactants in question.

Very effective are ethoxylated alkylaryl compounds, their effect by appropriate variation of the

Composition adapted to the respective purpose of use is adjustable. By using such

Surfactants can be an improvement in the wettability of the nonwoven surface to achieve and the liquid transport through the nonwoven through is accelerated. This is because the equalization of the surface energies of the nonwoven fabric and the liquid to be transported acts as an effective increase in the porosity Once the complete wetting of the Surface reached, the liquid can be fed through the capillaries of the absorbent layer. The liquid is then stored in the absorbent layer.

Although the wicking of such a treated nonwoven fabric is very good, Serious deficiencies result because of the unhindered return transport of the liquid, The cover nonwoven fabric immediately becomes wetted with the liquid stored in the absorbent pad. It appears wet and there is almost unrestricted liquid return of transport. The improved wettability helped the initial liquid transport in the desired direction towards the absorbent pad. is now disadvantageous and undesirable. Although nonionic surfactants, such as are commonly used as wetting agents industrially, thus allow a wicking effect, but they prove to be unsuitable for the equipment of covering nonwovens, because they remain at the nonwoven or Fiber surface adsorbs and thereby accelerate the liquid transport in both directions.

The object of the invention is thus not solved with conventional nonionic surfactants.

Non-ionic surfactants, if any, then only to a very small extent in the liquid phase.

Here, too, they ensure the maintenance of the wetting effect in both directions to the full extent. If you want to reduce the return transport of the stored liquid, you must aim for a balance by a fine adjustment of the amount of surfactant, in which both the primary transport to the absorbent pad and the return transport must be considered. It is possible at most by a compromise solution to achieve an approximately satisfactory result.

Since the invention is based on the object to develop a nonwoven fabric which largely prevents the return transport of the stored liquid with a very good wicking back to the absorbent pad, nonwoven fabrics equipped with conventional nonionic surfactants for the reasons set out above this

Do not solve the task. However, if one uses surfactants which on the cellulose or the cellulose-containing material of the absorbent pad are chemosorbable and the transportable by the liquid in the absorbent pad, so the problem is solved in an optimal manner. It has been found that the completely contradictory requirements of a rapid primary transport to the absorbent pad and a blocking effect in the opposite direction can be so well reconciled. To a very special extent cationic surfactants of the general formula have proven to be suitable as wetting agents for the cover nonwoven fabric,

<img file="AT396867B_D0001.tif" />

<img file="AT396867B_D0002.tif" />

A 'wherein Rj.R ^ R ^ and R ^ can be alkyl, aryl, alkylaryl, ethoxyl, alkylethoxyl, arylethoxyl and / or alkylarylethoxyl radicals. The radical A is a conventional anion, z. B. a halide.

It has been found that the cationic surfactants have excellent wettability. They significantly improve wicking because, on the one hand, they are only weakly adsorbed by the polymer surface so that a substantial portion passes into the liquid phase during wetting and, on the other hand, they are substantive to cellulose; H. they are chemosorbed on cellulose-containing substrates and thereby removed from the liquid phase again. The liquid phase thus serves as a means of transport of the wetting agent from the per se water-repellent fiber into the absorbent medium. The cover nonwoven fabric can therefore be well wetted to improve primary transport because a sufficient amount of the surfactant can be used. The migration of the cationic surfactant and subsequent bonding to the cellulose-containing substrate acts as a barrier to the undesired return of the liquid. Since the non-woven fabric made of synthetic fibers absorbs only very little water or binds, it appears "dry", even if it is clamped over a damp absorbent pad.

The cationic surfactants proposed according to the invention can be metered in high amounts. Thus, it is possible to achieve a rapid wetting, without thereby the return transport is promoted. Optimum properties of the cover fabric are obtained in view of the very contradictory requirements of the wicking and barrier effect.

The proposed cationic surfactants also have the advantage that they are bacteriostatic or even bactericidal, which is very desirable for many applications, especially in the medical field. Nonwoven cover fabrics which are finished in accordance with the invention are safe to use in the clinical and medical fields as well as in the cosmetically-hygienic field. It is important that the surfactants have no negative side effects on the human organism.

Among the proposed cationic surfactants, the following compounds have been found to be particularly useful:

Steaiyldimethylbenzylammoniumchlorid:

CH.

^C17^H33 " ^CH2 " ^CH2

CH "

CF

Methyldodecylbenzyltrimethylammoniumchlorid:

<img file="AT396867B_D0003.tif" />

25

N - CH ₃ch₃ he

dodecyldimethylbenzylammonium:

CH.

^C12^H25 ^N^CH? (δ) he

CHTetradecyldimethylbenzylammoniumchlorid:

CH.

^ 14 ^ 27 N "CH-,

- &lt;5&gt;

he

hexadecyldimethylbenzylammonium:

^r CH,

- CH "CH.

Diisobutylcresoxyethoxyethyldimethylbenzylammoniumchlorid:

CH₃ ch₃ ch₃ ch₃ - C - CH₂ - C - &lt;&lt;1 ch₃ ch₃ he

CH.

- 0 - CH₂ - CH₂ - 0 - CH₂ - CH₂ - N - CH₂ - (q&gt;

CH.

diisobutyl:

CH₃ ch₃

CH.

CH ^CH3 ^CH3

C &lt;E&gt; - 0 - CH₂ - CH₂ - 0 - CH₂ - CH₂ - N - CH₂ - (g&gt;

'I

Clk

CI

Methyldodecylxylylen-bis (trimethylammonium chloride):

CiL CH.

CH.

2+

<img file="AT396867B_D0004.tif" />

CH, - N - CH "-&gt; - CH" - N - CH ^CH3 ^C12^H25

CH, he

Although arbitrarily high proportions of cationic surfactants can be used, order quantities of 0.05 to 1.0% by weight, based on the weight of the nonwoven fabric, have generally proven suitable for finishing cover webs. In many cases amounts of up to 0.5% by weight suffice.

The equipment of the nonwoven fabric can be carried out in a manner known per se by padding, patting or spraying on the aqueous solutions or dispersions and subsequent drying, optionally under pressure. Nonwovens of any composition can be treated this way. The cationic surfactants can also be added to conventional lubricants and used in a particularly simple manner. A particularly advantageous equipment option is to blend the cationic surfactants in appropriate dosages of the polymer melt during the spinning process. The cationic surfactants represent a foreign to the polymer melt and immiscible phase with it, which is transported to the fiber surface due to their low viscosity.

example 1

A 22 dtex filament titer polypropylene filament spunbonded fabric having a basis weight of 15 mg / m bound by the calendering technique having a thickness of 0.16 mm is prepared by impregnation with an aqueous solution of diisobutylphenoxyethoxyethyldimethylbenzylammonium chloride as a cationic surfactant. The application amount is adjusted by the concentration of the solution and by the amount of liquid applied, as shown in the table. Subsequently, at 100 ° C in a

-5AT396867B

Air dryer dried

The finished nonwoven fabric is tested for wicking (run-off) and rewet according to the following procedure. The results are given in the table.

Dochtwifknng (run-off) test:

A 300 g / m² heavy pulp absorbent pad of at least 250 mm length is straddled on a smooth impervious base with the cover fleece to be tested and placed at a 45 ° angle to the vertical. At the top of the absorbent pad thus produced, a discharge nozzle is formed at a distance of 200 mm from the lower end attached, which is connected to an automatic pipette with a volume of 30 ml. The outlet nozzle is designed to ensure a flow rate of 0.5 ml / sec in the described arrangement. Under the lower edge of the absorbent pad, several layers of filter paper are arranged to cushion the excess amount. Thereafter, from the pipette, the 30 ml of the test liquid is allowed to stand for 60 sec poured on the absorbent pad. The test liquid is distilled water whose interfacial tension is increased to 42 x 10 'by addition of the cationic surfactant.² N / m at 23 ° C is used The liquid flow initially flows down the surface of the cover fabric until it wets Then the remainder of the pud liquid is absorbed by the absorbent pad and stored The excess of test liquid reaching the bottom edge of the absorbent pad is absorbed by the underlying filter paper and detected by differential weighing. A good cover fleece should lead to an excess of at most 0.5 g. The wicking effect is better, the lower the excess isL trapped at the lower edge

Rewetting freewet) test A pulp absorbent pad having a basis weight of 300 g / m² will have a smooth, horizontal plate-clamped and covered with the non-woven fabric to be tested. The absorbent pad is replaced by a 20 mm long tube of 20 mm diameter, on the underside of which there is a sieve for distributing the liquid, Then, 30 ml of the test liquid indicated in the above-described run-off test are filled in. After the liquid is sucked up by the absorbent pad, the wetted spot becomes a cylindrical metal body having a weight of 30 N and a contact area of ​​100 cm² Pressed for 3 minutes. Then a filter paper folded several times is placed under the metal body and the wetted area is subjected to a further 2 minutes. The liquid permeating through the cover fleece is absorbed by the filter paper and detected by differential weighing. The result is designated as rewet still as "dry" to be designated nonwoven fabric be less than 1.0 g.

Example 2

Under the conditions of Example 1, the cation-active surfactant used is a mixture of 80% by weight of methyldodecylbenzyltrimethylammonium chloride and 20% by weight of methyldodecylxylylene bis (trimethylammonium chloride). The results are again shown in the table

Comparative example

Under the conditions of Examples 1 and 2, instead of the cationic surfactant of the invention, a commercial nonionic surfactant, namely isooctylphenoxypolyethoxyethanol, is used. The result is also shown in the table.

3 ^ Bellei

<td></td><td>Surfactant application in mg of surfactant / m²</td><td>wicking (run-off) in g</td><td>Rewetting (rewet) in g</td>

<td>Example 1 a b</td><td>25 50</td><td>0.17 0.12</td><td>0.18 0.22</td>

<td>Example 2 a b</td><td>25 50</td><td>0.21 0.02</td><td>0.17 026</td>

<td>Comparative example a</td><td>25</td><td>0.65</td><td>0.70</td>

-6AT396867B

Table 1 continued

<td>b</td><td>50</td><td>0.20</td><td>1.80</td>

<td>c</td><td>75</td><td>0.14</td><td>2.20</td>