DE2460712B2 - Absorption lectures and processes for their preparation - Google Patents

Description

The invention relates to a thin absorbent sheet of elongated outline, in particular for feminine hygiene, consisting of a liquid-impermeable base layer made of a plastic film, an absorbent layer made of short fibers and a liquid-permeable cover layer made of a nonwoven material, these layers together to form one Laminate are glued and wherein the laminate is provided with a pattern of longitudinal, preferably wavy embossed lines. Also deals the invention with a method for the production of such a thin absorption template.

The required absorption template - also referred to below simply as template - is already known from DE-AS 11 63 491, specifically for the special case of a diaper. The well-known The template thus has the form of a three-layer laminate made of a liquid-impermeable, film-like base layer, one made of cellulose fibers the absorbent layer and a fleece cover layer, wherein the laminate is provided with a preferably wave-shaped embossing, which is in the embossed areas Creates capillaries, which improve the conduction of liquid within the absorbent layer.

In the known template, the absorbent layer consists of flaky wood fiber mass, and the cohesion of the laminate is effected by a thermoplastic adhesive, which extends from the fleece through the

ίο The absorbent layer extends through to the base layer and thereby connects all three layers with one another. In detail, one through the thermoplastic adhesive to use pointwise connected fleece layer and the embossing process there

take advantage of that wherever there is an embossed line hits an adhesive point, the adhesive softens under the influence of temperature and can thus penetrate the laminate. In practice, the structural design of the known template as well as the adhesive penetrating the laminate proved to be unfavorable. On the one hand is used wherever the adhesive has penetrated the laminate - i.e. in the area of the embossed lines - the fluidity aimed at by the embossed lines interrupted because the capillaries are on these Places inevitably clogged. On the other hand, the product cannot be rinsed because of the continuous adhesive, it cannot dissolve into its constituent parts, even in excess of water. the lack of rinsing ability provides for feminine hygiene products a serious disadvantage, since this is in the usual manner to disposable products, for example, ία a toilet to be flushed away.

The invention is based on the object of avoiding the disadvantages described and a thin one Absorbent template with improved fluid conduction and with the property of flushing ability create. Since these are disposable products that have to be cheap, and accordingly not high May require manufacturing effort, the invention is also based on the object of a simple and indicate inexpensive method for the production of a thin absorption template.

The object is achieved when the prerequisite in the preamble of claim 1 is thin Absorption template in that the absorbent layer is a layer consisting of air-laid cellulose fibers, which on their surfaces on the one hand by means of a surface sprayed adhesive with the top layer and on the other hand is glued to a point-like adhesive pattern with the base layer and which in the areas compressed by the embossed lines are closed by hydrogen bonds, the Fibers of the absorbent layer in those edge areas of the template that are between the points of intersection of the Embossed lines extend with the edge of the template, unbound and open to the outside between the Edges of the top layer and the base layer.

In terms of the method, the invention provides that an uncompacted web of air-laid cellulose fibers one of its surfaces is sprayed with an aqueous latex and connected under slight pressure with a liquid-permeable nonwoven web that then the structure consisting of the cellulose fiber web and the nonwoven web under heat, pressure and moisture conditions that result in hydrogen bonds in the cellulose fiber web,

that then the embossed structure on the free surface of the cellulose fiber web under light Print with a dot-like adhesive pattern supporting web of a film material is connected to form a three-layer laminate web, and that Finally, the individual templates are punched out of this three-layer laminate web.

The procedure is therefore carried out in a number of steps that are clearly delimited from one another, the successive method steps ensuring in a simple manner that the desired structure of the template is obtained in any case. This is of particular importance for large-scale operations, since the production effort is low and the template can be produced cheaply \ ->

In contrast to the aforementioned DE-AS 11 63 491, which teaches the use of a continuous adhesive and in which the absorbent layer consists of flaky wood fiber mass, an absorbent layer consisting of air-laid cellulose fibers is provided in the invention and instead of the known one passing through the laminate Adhesive connection, the individual layers are only glued on their surface, in a way that is completely independent of the course of the embossed lines. To bond one surface of the absorbent layer to the fleece layer, a flat adhesive is provided, while the impermeable base layer is glued to the other surface of the absorbent layer via an adhesive applied at points. Thus, the inside of the absorbent layer is completely free of any adhesives. A non-bound to the absorbent layer of course normally no cohesion, which is especially the sufficient cohesion of the fiber layer applies v for air-laid cellulose fibers in the invention> in itself is concerned here by the formation of hydrogen bonds in the crease lines

Overall, the invention thus creates a product in which the liquid line is along the embossed lines is not interrupted by glue dots and with each embossed line along its entire length contributes equally to the inner cohesion of the fiber layer, while the two outer layers are only superficially connected to the fiber layer independently of the embossed lines.

In the template according to the invention, the absorbent material is sandwiched between arranged two further layers, namely a liquid-permeable cover layer facing the body and a liquid-impermeable base layer. All three layers have the same Outline shape, i.e. all three layers end at the circumferential edges in the template without any over the Sheath drawn around the edges of the original or a continuous compression of the entire circumferential area the template is provided. Such a template can be produced with very little effort, i.e. with can be produced at low cost.

It is true that in the template according to the invention a small part of the fibers can be found in the unbound «> Dust out peripheral areas of the original, which is a certain disadvantage. This disadvantage is more than compensated for by the very important advantage that the unbound edge areas of the original are too much Soft and soft edges lead, which with the e> 5 use a previously unattainable high Result in wearing comfort. Another advantage of the invention Vuriage iiegi in that they are in need can easily be flushed away in a toilet system, since with an excess of water the Hydrogen bonds that alone hold the template together in the direction perpendicular to its plane, be lifted and thus the entire absorbent layer or at least the largest part of it in the triggers individual fibers This then also separates the top layer and the base layer from one another.

Any liquid-permeable, z. B. for sanitary napkins common nonwoven material can be used. The best known is a material made of carded rayon fibers of staple length bonded together by a flexible adhesive. The base layer is preferably a thin film of a liquid-impermeable plastic, e.g. B. off Polyethylene.

To connect the cover layer to the absorbent layer by means of a flat flexible adhesive in such a way that the adhesive does not penetrate the absorbent layer, a water-based latex is preferably used, the z. B. is sprayed onto the absorbent layer prior to application of the cover layer. The one contained in the latex sticky solid remains on the surface of the absorbent layer while the water also enters the absorbent layer can penetrate and there, which is very beneficial, for the necessary moisture conditioning for contributes to the formation of hydrogen bonds.

After spraying the adhesive, the absorbent layer is covered with the cover layer and the The superficial fibers of the absorbent layer are then removed by the simultaneous application of heat and pressure flatly connected to the top layer. Only a moderate overall pressure is exerted on the laminate Cover layer and absorbent layer exercised so that there is no areal formation of hydrogen bonds In the area of the embossed lines, however, there is the formation of hydrogen bonds Desired and required in the absorbent layer, d. H. in this area the pressure at Connect the top layer and absorbent layer so that there are hydrogen bonds below the embossed lines form in the absorbent layer. This is best done with the help of an embossing roller, in which the areas of the embossed lines are defined by raised embossing projections.

Many different types of patterns can be used for the embossed lines as are particularly useful wave-shaped embossed lines have been found to mark the ends and edges of the original in intersect spaced intervals. The embossed lines preferably run parallel to each other, their distance is such that the cover layer between the individual Embossed lines are not placed under strong tension and the absorbent layer is thus between the embossed lines their uncompressed structure, which leads to the formation of soft, elastic, pillow-like areas, maintains

The course of the embossed lines in the longitudinal direction of the original is important, so that the largest part in particular the side edges of the template remain free of embossing and thus contains unbound fibers that lead to soft and elastic edges. Otherwise result the longitudinal direction of the embossed lines also has advantages in terms of better distribution of the absorbed liquid.

After joining and preening the top layer

and the absorbent layer to a laminate, the base layer is applied by using each point-like adhesive elements are connected to the adjacent fibers in the surface of the absorbent layer. The distance between the individual adhesive elements is dimensioned so that the entire structure is still sufficient Retains flexibility.

All of the above processing steps are carried out using continuous webs of material executed, d. H. they can be done quickly and easily on automatic machines. To After applying the base layer, the individual templates are then punched out.

The templates are usually worn with tight-fitting underwear so that special measures for fixing the templates are not absolutely necessary, but it is possible and in a number of cases also expediently, a strip of one on the underside of the base layer pressure-sensitive adhesive (which is usually covered with a removable protective layer) to attach the template with the help of this adhesive to the Fasten underwear. Alternatively, the underside of the base layer can also be provided with a friction-increasing material, e.g. B. with a Layer of a polyurethane foam or the like.

In the following, exemplary embodiments of the invention are explained in more detail with reference to the drawings. Included represents

Fig. 1 is a plan view of a template according to the invention with an elliptical outline shape,

2 shows the top view of a template according to the invention with an elongated trapezoidal outline shape,

F i g. 3 shows, on an enlarged scale, a section in the plane 3-3 of FIG. t,

F i g. 4 shows a section analogous to FIG. 3 for a modified embodiment,

F i g. 5 is a perspective view of the underside of the template for a further embodiment.

The in F i g. 1 shown template is a flat structure with an approximately elliptical outline, which composed of a lower base layer 19 in the form of a thin film of z. B. polyethylene and a middle absorbent layer 17 in the form of a layer of cellulose wadding (neither can be seen in FIG. 1) and an upper cover layer 12 made of a fleece material. In the cover layer 12 are each other parallel wave-shaped embossed lines 14 attached These embossed lines extend in the longitudinal direction of the Template and run along their entire length, they cut the ends and edges of the template in Intervals 15, between which areas 16 that are not embossed and thus unbound in the z-direction are located. The z-direction is in the illustration of FIG. 1 the direction perpendicular to the plane of the drawing, the Ar direction and the y direction are than in the Defined in both coordinate directions lying on the drawing plane

The template according to FIG. 2 has the outline shape of an elongated trapezoid, but is otherwise the Submission according to FIG. 1 constructed the same way

The internal structure of the template is shown in FIG. 3, which shows a section in the plane 3-3 of FIG. 1 It can be seen that the wadding layer forming the absorbent layer 17 in the area between the Embossed lines 14 is fluffy, below the embossed lines 14 however, is compressed into highly compressed areas 18. In these compressed areas 18, hydrogen bonds form between the individual pulp fibers, those of the fluffy ones Wadding layer give sufficient integrity and thus a layer-by-layer disintegration in the prevent z-direction. In contrast, the individual fibers are in the areas between the embossed lines 14 Wadding layer practically uncompressed and unbound,

they therefore press against the cover layer 12 from below and give it a rounded, pillow-shaped contour in the areas between the embossed lines.

The base layer 19 is attached to the absorbent layer 17 by means of adhesive, it essentially retains its planar configuration, i.e. it is created by the urikornprirnierien and unbound fibers of the absorbent layer 17 in the area between the embossed lines 14 practically not curved outwards. The adhesive connecting the base layer 19 and the absorbent layer 17 has the form of a pattern consisting of individual adhesive elements and is prior to assembly of the three layers forming the template are applied to the base layer 19. The cover layer 12, too is connected to the absorbent layer 17 by means of adhesive, however, in this case the glue is practical evenly in a thin layer between the contacting surfaces of the cover layer 12 and the absorbent layer 17 attached.

The absorbent layer 17 is in the unembossed edge

Jo areas 16 in which no embossed lines 14 end in arched in the same way as in the area between two embossed lines. This gives the Template the desired soft and gently conformable edges.

y> The in the F i g. The template shown in FIG. 4 corresponds to the template according to FIG. 3, but with the difference that beneath the base layer 19 there is also a layer 20 made of a soft synthetic foam, e.g. B. made of polyurethane foam, this foam layer 20 is arranged is flatly connected to the base layer 19 and gives the template a lower surface with a high coefficient of friction. This makes it easier to attach the template to your Hold space when worn in tight-fitting underwear

«Another possibility the submission in relation to the Holding underwear in place is shown in FIG. 5 shown in perspective There it is shown that on the Underside of the base layer 19 (in the illustration of FIG. 5 above) a narrow adhesive tape 22 made of a

so self-adhesive pressure-sensitive adhesive is arranged which is provided with an easily peelable protective strip 24 from a facing the adhesive adhesive paper or the like is covered. When using the template, the Protective strip 24 is peeled off, and then the original with the exposed adhesive tape 22 on the crotch area (usually in the area with the gusset) the underwear laid on This type of attachment of a template is known per se, it has a number of Advantages and is therefore preferred to other ways of attaching the template

The template does not necessarily have to be elliptical or an elongated trapezoid, they can be any other, in general have elongated geometric shape. For example it can be rectangular or flattened or hexagonal or diamond-shaped or whatever elongated.

The embossed lines 14 are shown in FIGS. 1 and 2 as undulating parallel embossed lines with uniform Distance shown Instead, others can also extend in the longitudinal direction of the original Patterns can be used for the embossed lines. However, the following points are important:

(1) The embossed lines must be spaced a sufficient distance from one another to be in the area the absorbent layer 17 is not impermissibly compressed between two adjacent embossed lines;

(2) for the same reason, the areas of the absorbent layer 17 compressed by the embossed lines must be as narrow as possible;

(3) the embossed lines must extend essentially in the longitudinal direction of the original;

(4) The embossed lines must intersect the edges of the original at a sufficient distance from one another to allow compression of the edge areas is reduced to a minimum.

Typical dimensions for the embossed lines include an embossed line width of about 0.8 mm and one Distance between two embossed lines of about 6 to 10 mm.

In addition to creating a hydrogen bond, which primarily ensures the integrity of the template in the z-direction is effected, the purpose of the embossing lines is to represent the template including its edges and To provide wheels with a soft, cushion-like structure. Furthermore, the embossed lines also have the purpose of the migration of the absorbed liquid within the template in its longitudinal direction judge. This latter point is especially important because the page margins of the original are not are sealed and therefore the absorbed liquid should be kept away from the side edges for as long as possible. The lengthways of the original Extending embossed lines act as guide channels, as they are very much due to their compressed state have small pores, through which the capillary suction pressure is favored in the longitudinal direction of the template.

In addition, a wave-shaped design of the embossed lines 14 is the preferred design. It was namely found that with the bending of the template required for use in the curved Shape wavy lines are much more flexible than straight lines. In particular, wavy lines form only very small creases when the template is bent, which is important for the wearing comfort of the template are much cheaper than the coarse and big gimmicks that have often been observed so far.

The main purpose of the embossing lines is, as before mentioned the creation of a bond between the short cellulose fibers of the absorbent layer by means of a Hydrogen bond. In the paper industry, hydrogen bonds are generally bonds that are form between the hydroxyl groups of adjacent fibrils in the cellulose fibers when one Paper web is dried. In the present case, such hydrogen bonds are created by the Embossing creates these hydrogen bonds are the only means of maintaining strength and Integrity of the suction duct in the z-direction of the original. The strength and integrity of the template in the χ-direction and also in the y-direction are effected through the adhesive attachment of the top layer and the base layer to the top layer

For the production of the templates a thin one is used uniform layer of air-laid cellulose fibers went out. There are already numerous methods for Manufacture of air-laid webs from cellulose fibers known, these methods are consistently for the can be used in the present case and do not need to be explained in detail here. At airlaid In webs of cellulose fibers, the individual fibers are practically oriented statistically and thus up to one networked with one another to a certain extent Despite this certain network, however, such railways have practically no integrity of its own because, first of all, the individual fibers are so short that despite the cross-linking the mechanical cohesion between the fibers is only slight, and secondly because of the Air laying method practically no chemical bond is generated between the individual fibers. So air-laid webs are inherently very weak, they become very light by applying even low tensile forces destroyed and they must therefore be additionally stiffened in some form for handling. this applies especially for very thin webs of z. B. 1.5 to 6.5 mm Starch as used in the present case. Because of the inevitable structural weakness an air-laid unbound web of cellulose fibers, it is therefore necessary for the further Process steps for the production of a template to support the web with any support means. The screen fabric on which the web was placed during its manufacture can be used as such a support means. be used. Alternatively, the fibrous web but also from a wide-meshed gauze-like one Carrying fabric or a corresponding fleece-like carrier material can be deposited, whereby the carrying fabric or the viies-like support material then remains as an integral part of the web and with in the end product arrives. This latter modification, however, increases the cost of the end product, and because the templates are preferred should be disposable cheap templates, the incorporation of an additional supporting fabric or

to carrier material can be quite undesirable from a cost point of view.

The airlaid web, after molding, is lightly sprayed with a water-based flexible adhesive in amounts of about 5 to 18 g / m ² have proven to be sufficient. As such an adhesive, an acrylic latex is generally preferred desirable to use latices or other water based adhesives because it is anyway necessary to use the cellulose fibers during manufacture ment to moisten the template to the already to generate mentioned hydrogen bonds. By the use of a water-based adhesive such humidification is achieved at the same time

After the glue on the air-laid fibrous web

has been sprayed on, the top layer (a liquid-permeable fleece-like material) that surface of the web is placed on which the Adhesive has been sprayed on. The laminate produced in this way is then lightly between two rollers pressed together to ensure that the cover sheets adhere well to the wadding sheet. To As it passes through the rollers, the laminate is placed under a bank of infrared lamps or one other heat source passed what the purpose has to set the adhesive and at the same time the from the To distribute moisture from the adhesive as evenly as possible in the wadding. Through the Adhesive generally becomes an amount of moisture

from about 10 to 20% by weight incorporated into the web. Around The final conditioning of the laminate for the application of the embossed lines can then still be done further moisture can be introduced by spraying water on the cotton wool layer.

The laminate is then passed through a pair of rollers lying on top of one another at high pressure, in which one roller (namely the roller facing the cover layer) is an embossing roller provided with the intended embossing pattern, while the other roller is a heating roller. When passing through this pair of rollers, the embossing pressure, which is exerted by the embossing projections of the embossing roller on the moisture-conditioned wadding web, creates the desired hydrogen bonds between the fibers, in such a way that these hydrogen bonds only in the embossed areas and not in occur in the areas between the embossed lines. For this purpose, pressures in the nip of about 4.9 to 6.0 kg / cm ² and temperatures of about 150-180 ° C. are sufficient. As a result of the temperatures used, the remaining moisture is driven out of the wadding and the applied adhesive is further set. The density of the wadding web in the compressed and hydrogen bonded areas is preferably about 0.4 to 1.0 g / cm ³ , while in the uncompressed areas it is preferably about 0.03 to 0.15 g / cm ³ cherishes

After passing through the embossing roller arrangement, the laminate runs through another pair of rollers in which it is bonded to the film-shaped base layer under slight pressure. On the Base layer an adhesive pattern is applied beforehand, which connects the base layer with the wadding web

The three-layer laminate produced in this way then runs to further processing stages in which the individual templates with the The desired shape can be punched out of the laminate, and in which, if necessary, the pressure-sensitive adhesive or other friction-increasing adhesive Agent can be applied to the underside of the base layer.

It has been found that the hydrogen bonds formed in the area of the embossed lines are sufficiently strong to ensure the integrity of the wadding layer thus ensuring the cohesion of the overall structure during normal use. if the Submission, on the other hand, should be flushed in a toilet after normal use (or possibly unintentionally comes in contact with a large excess of water) the hydrogen bonds break instantly destroyed as soon as the water penetrates the wadding layer In this way the wadding layer is delaminated, the majority of cellulosic fibers dispersing into individual fibers during rinsing Of course, neither the top layer nor the base layer are broken down into their individual components, but it can be assumed that these two layers are so flexible that they can be reached without difficulty a normally functioning toilet system can happen.

Acrylic latices are the preferred adhesives for both to connect the top layer to the wadding layer as well as to connect the base layer to the Cotton wool layer. However, other flexible adhesives of the same nature can also be used just as well, for example in the group of acrylic adhesives, ethyl and methyl acrylates and theirs

ίο copolymers, and copolymers of ethyl acrylates, Ayrylamides and acrylic acid. Other suitable adhesives are vinyl latices such as vinyl acetates and Vinyl chlorides and combinations of these two, other synthetic latices such as butadiene, acrylonitrile and styrene and copolymers of these natural rubbers. Strengths and the like. As already mentioned, the adhesives are used in a water-based form so that the wadding is already through the Adhesive application at least partially for the creation the hydrogen bonds is conditioned

In order to increase the absorbency of the wadding web for the latex, surfactants can be added to the latex in an amount of about 4 to 5% by weight, based on the latex solids. For

All suitable surface-active agents can be used for this purpose, sulfated ones being preferred or sulfonated organic compounds of the type for which sodium diamyl or sodium dioctyl sulfosuccinates, sodium lauryl sulfates, sodium sulfoethyl methyloleylamides and sodium sulfonates of alkylated

Phenols or benzenes are representative. If those

surface-active agents must be used they are of course non-toxic in nature.

In principle, the template in its from the

three-layer sheet punched shape can be used, but it is also preferred with Provide means by which it is better kept in the underwear. In this regard, an adhesive tape made of one is particularly useful pressure sensitive adhesive as shown in Figure 5 Instead, a thin layer of foam z. B. used from polyurethane as shown in FIG. 4 represents Furthermore, fleece or nonwovens can also be applied to the underside of the base layer Patches of friction-increasing heat-meltable material or the like are applied.

The cover layer can also be made of different materials without fulfilling its function lose. The cover layer is preferably of a fleece type gen web of staple length rayon fibers. It can however, other fibers including absorbent and non-absorbent synthetic fibers can be used. Likewise, are also spunbond Sheets of long threads, e.g. B. made of polyethylene, Polypropylene, polyesters, nylon and the like usable. These latter webs have a hydrophobic nature, so that the original with normal Use maintains a much drier surface. This is the reason why such webs are sometimes

β "preferred

For this purpose 2 sheets of drawings

Claims (2)

Patent claims: 1.Thin absorption template with an elongated outline, especially for feminine hygiene, consisting of a liquid-impermeable base layer made of a plastic film, an absorbent layer made of short fibers and a liquid-permeable cover layer made of a non-woven material, wherein these layers are glued together to form a laminate and the laminate with a pattern of longitudinal, preferably wavy embossed lines is provided, d u r c h characterized in that the absorbent layer (17) is a layer consisting of air-laid cellulose fibers is, which on their surfaces on the one hand by means of a surface sprayed adhesive with the Cover layer (12) and on the other hand in a punctiform adhesive pattern with the base layer (19) is glued and which in the areas (18) compressed by the embossed lines (14) is bound by hydrogen bonds, the Fibers of the absorbent layer (17) in those edge areas (16) of the template that are between the Intersections (15) of the embossed lines (14) extend with the edge of the template, unbound and after are open on the outside between the edges of the cover layer (12) and the base layer (19). 2. A method for producing an absorption template according to claim 1, characterized in that that an undrawn web of air-laid cellulose fibers on its one surface with a Aqueous latex is sprayed and connected under slight pressure with a liquid-permeable nonwoven web, that then the structure consisting of the cellulose fiber web and the nonwoven web under Heat, pressure and moisture conditions that create hydrogen bonds in the cellulose fiber web result, is embossed that then the embossed structure on the free surface of the Cellulose fiber web under light pressure with a web bearing a point-like adhesive pattern is joined from a film material to form a three-layer laminate web, and that finally the individual templates are punched out of this three-layer laminate sheet.