Superficial fibrous formation of three-dimensional structure, exhibiting high fluid absorption properties, method of obtaining same and application thereof

Description of the invention

The subject of the invention is a fiber fabric with a three-dimensional structure and high fluid absorption capacity, a method for its production and its use.

There are many varieties of wiping or washing wipes on the market. Commonly found are papers or nonwovens and are often used as wet wipes or as liquid absorbent wipes. Such wiping wipes, acting as moisturizing wipes or liquid-absorbing wipes, are used, for example, in the care of babies, in cosmetics, for example for skin care, for removing dirt in the household, in bathrooms or for cleaning rooms, for application or removal on skin care or cosmetic substances, medical substances or for intimate hygiene. These are products having a structure that should have a high water or fluid absorption capacity. In addition to water, these structures often contain various types of lotions based on oils or mixtures of oils, water and / or chemicals which, thanks to their fibrous surface, support the cleaning process. Because the products are often used with your hands, they are bulky, fluffy, or folded or squashed when used to make them easier and more enjoyable to use.

Three-dimensional structures used as wiping wipes are known from WO-A-00 / 108,998 and WO-A-99 / 107,273. These are composites of at least one or two nonwovens and extruded, biaxially tensioned meshes, e.g. polypropylene, which, after lamination, for example by partially bonding under pressure and temperature, develop convex structures in the third dimension due to shrinkage, thereby acquiring more volume. These protrusions, due to the contraction in both directions, i.e. along and across the monofilaments of the taut polypropylene mesh, are relatively uneven and have an unattractive appearance. The bonding of the two layers of non-woven fabric takes place through the mesh by spot or pattern welding in a calender under the action of pressure and temperature.

EP-A-814,189 discloses a non-woven fabric consisting of at least one unidirectional stretching non-woven fabric and a short-fiber non-woven fabric mechanically connected thereto. The composite is characterized by high volume and good grip.

Fibrous surface structures with a three-dimensional structure are also known. DE-A-199 00 424 describes three-dimensionally structured combinations of thermally welded together in the form of a regular pattern, layers of filaments and staple fibers. The three-dimensional structure results from the use of fiber layers with different shrinkage properties. As a result of the contraction initiation, the staple fiber layer is given a three-dimensional structure. It has turned out, however, that the resulting three-dimensional structure is irregular, since the sequence of the ridges and depressions follows a rather random pattern.

Examples of such composites are fibrous skin forms of at least one or two nonwovens and extruded biaxially tensioned meshes, for example polypropylene (hereinafter referred to as "PP). After lamination, these composites form convex structures in the third dimension due to shrinkage. These protrusions, inter alia as a result of shrinkage in both directions, i.e. along and across the monofilaments of the taut PP mesh, are relatively uneven and have an unattractive appearance. The bonding of the two layers of non-woven fabric is usually done by means of a mesh by spot or pattern welding in a calender under pressure and temperature.

JP-A-09 / 111,631 describes a combination of nonwovens with different shrink properties. The initiation of the shrinkage process of one layer entails the corrugation of the composite surface. This publication does not mention the use of staple fiber blankets as inner layers.

Based on this state of the art, it is an object of the invention to propose a three-dimensional structured fiber surface which is characterized by increased fluid absorption and at the same time has a regular three-dimensional pattern. The invention is therefore intended to enable the production of fibrous structures with a high liquid absorption capacity, a regular structure and a high volume or fluffiness. By using certain measures according to the invention, a high water absorption should therefore be achieved and a structure with three-dimensional ridges or indentations defined in advance, while at the same time eliminating randomness and the related irregularities in the structure.

A fibrous fabric with a three-dimensional structure, high fluid-absorption capacity of at least 5 g of fluid per g of surface structure, and a thickness of at least 0.8 mm, with regular alternating reliefs and indentations in relation to the surface of the structure,

According to the invention, the at least one nonwoven layer is a staple fiber blanket that forms the outer layer and comprises a mixture of thermoplastic polymer fibers and viscose fibers or fibers from renewable raw materials, the staple fiber cover is connected to the shrunken surface structure by means of welds welded in the form of regularly spaced lines running perpendicular to the direction of the greatest contraction of the surface structure, and spaces are formed between the staple fiber cover and the shrunken surface structure .

Preferably, the non-woven layer is fixed on the shrunken surface body by means of a tie pattern in the form of regularly spaced and uninterrupted lines.

Preferably, the shrunken fabric is made of a material from the group consisting of woven, knitted, mesh, mat, parallel monofilaments, staple or multifilament yarns, non-woven fabric or film.

Preferably, the shrunken face is made of a non-woven or film material.

Preferably, the shrunken surface is made of uniaxially or biaxially stretched film.

Preferably, the fiber fabric comprises a shrunken face and two non-shrunk or low-shrink staple fiber sheaths.

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Preferably, the fiber surface has a basis weight of 40 to 300 g / m2².

Preferably, the fabric surface comprises fluids, in particular water and / or oil-in-water emulsions.

Preferably, the welding pattern of the non-woven layer and the shrunken surface is in the form of regularly spaced, preferably uninterrupted, lines or beams perpendicular to and / or in the machine direction.

Preferably, the welding pattern of the nonwoven layer and the shrunken surface is in the form of lines, regularly spaced on the surface of the nonwoven in hexagonal shape.

A method for producing a three-dimensional fiber fabric with a high fluid absorption capacity, of at least 5 g of fluid per g of fabric, a thickness of at least 0.8 mm, with regular alternating protrusions and indentations in relation to the surface of the structure, containing at least one layer of non-woven fabric and the shrunken surface structure connected to it, according to the invention, is characterized by: that a combination of a mixture of thermoplastic polymer fibers and viscose fibers or fibers from renewable raw materials is used to form an outer layer, staple fiber blankets and a shrink surface, and then welded, preferably by heat and pressure, and / or by means of a calender. ultrasound, staple fiber blanket with contractile surface structure, creating a linear pattern running at least perpendicular to the direction of the strongest contraction of the contractile surface structure, after which the obtained composite is heated to the contraction temperature of the contractile surface structure

The inventive fiber surface with the three-dimensional structure is used as wiping wipes, moisturizing wipes or as a fluid reservoir for cleaning or applying fluids, for example medical or cosmetic substances.

The composite according to the invention has a high relative and absolute water absorption. A high absolute water absorption can be achieved such that the fibrous structures have a higher basis weight after shrinking into a three-dimensional structure and can therefore absorb more water. This dependence is understandable to a specialist. Surprisingly, such three-dimensional surface structures also show a much higher percentage of water absorption, which is independent of the basis weight used. As a result of the third dimension shrinkage, a higher percentage of fluid absorption is achieved, and at the same time a regular three-dimensional volumetric pattern is produced.

In the water-absorbent structures, viscose fibers are usually used as the main or auxiliary component in order to achieve high water absorption. This solution is known and widespread among specialists. By means of the present invention, it can be shown that the compositions according to the invention make it possible to markedly increase the relative water absorption of viscose-containing products. It even turns out that materials without viscose at all also have a very high relative and absolute water absorption capacity. Therefore, it is possible to create surface structures with a three-dimensional structure, showing a high adsorption capacity, without the use of viscose fibers. Viscose fibers are usually more expensive than na

They are based on polypropylene or polyester and tend to produce an unpleasant odor in the presence of moisture. This can be prevented by using a non-woven structure without viscose or containing the polymers mentioned.

Preferably, the nonwovens used in the composites according to the invention contain, in addition to thermoplastic fibers, such as polyolefins and / or polyesters, also semi-synthetic fibers, such as viscose or viscose-based fibers, such as Lyocell® or fibers from renewable raw materials, or mixtures of these fibers. The composites of the invention may also contain liquids, especially water and / or oil-in-water emulsions.

The composite according to the invention comprises at least one layer of non-woven fabric and at least one layer of another surface structure, which tends to shrink or decrease in surface area when exposed to moist and / or dry heat.

The nonwovens used according to the invention, which do not shrink or do not shrink very much under the process conditions, can consist of any type of fiber with a wide range of titer, for example from 0.5 to 50 dtex. In order to obtain sufficient softness, fibers with a titer of less than 5 dtex, preferably less than 3.5 dtex, in particular less than 3.3 dtex, are preferably used for the outer layers of the composite according to the invention. In addition to homogeneous fibers, it is also possible to use heterogeneous fibers or mixtures of different types of fibers. In addition to nonwovens from under the filament, preferably staple fiber nonwovens, in particular unbonded staple fiber nonwovens, are used.

The three-dimensional fiber fabric preferably comprises three layers, both of which nonwovens covering the three-dimensionally shrunken fabric are staple fiber nonwovens having the same or different fiber orientations and / or having the same or different fiber structure.

Typically, the nonwovens or their unbonded primary products (fleece) have a basis weight of 5 to 100 g / m 2²preferably from 10 to 90 g / m2².

The fabric of the fabric according to the invention typically has a shrinkage fluffiness (as defined hereinafter) of at least 100%, preferably 150-400%.

The use of three-layer fiber composites with low basis weights after welding and before shrinkage, ranging from 20 to 100 g / m2, is particularly advantageous.². Extremely light and highly absorbent composites can be produced from these fiber composites by shrinkage.

The inventive three-dimensional textile fabric preferably comprises three layers and has a basis weight of 40 to 300 g / m2.².

In this case, the contraction can only take place in one privileged direction, but also in two or more directions. The amounts of shrinkage in several directions, for example in two directions, i.e. in the machine running direction and at an angle of 90 ° to this direction, may be the same or different.

In order to fix the binding pattern by which a non-shrink or only slightly shrink under the process conditions the nonwoven fabric is fixed on the contractile surface, the ratio of the pattern lines in the longitudinal direction to the transverse direction should be close, preferably equal. If, for example, the shrinkage material only shrinks in the longitudinal direction, i.e. has no transverse shrinkage at all, then the linear welding pattern of the nonwoven fabric and the shrinkage surface should run perpendicular to the longitudinal direction. The engraving cylinder of the calender is then, for example, a cylinder covered with protuberances which are 100% oriented in the transverse direction, since the welding must take place in the form of continuous lines.

The welding connection between the fiber fleece and / or the non-woven layer and the contracted or shrinkage surface of the composite according to the invention is preferably achieved by means of heat and pressure in the calender gap and / or ultrasound.

It has turned out that the spacing of these lines and the amount of linear shrinkage are responsible for the shape of the protuberances and indentations, meaning that the shape of the portions of the fabric surface protruding from the plane is precisely defined by the line pattern of the welding pattern.

The shrinking or shrunken surface formation can be of any nature. It may be a shrink textile surface, for example a woven, knitted fabric, mesh, mat, parallel-oriented monofilaments, staple or multifilament yarns, a non-woven fabric or a shrink film. The shrink fiber fabric may consist of stretched, in-line

And threads or yarns oriented parallel to each other. These stretched relatively taut threads or monofilaments may cross other, at an angle to the first, stretched or unstretched or less stretched threads / monofilaments or yarns. The intersecting fibers, threads or monofilaments can be bonded to each other by themselves, for example by mechanical bonding or welding at the crossing points. Binding can, however, also take place with the aid of binders, for example aqueous dispersions.

Constructed according to the invention and joined to a laminate, the three-dimensional structured fiber surface opening may consist of a shrunken web and at least one nonwoven layer, not shrunk or shrunk to a lesser extent under the process conditions. The shrunken fabric may, however, also be covered on both sides with a nonwoven fabric, symmetrically or asymmetrically, which means that the two nonwoven fabric layers may have the same or different basis weights. Both layers of the non-woven fabric can undergo, if they show a shrinkage tendency at all, to the same or different shrinkage. However, at least one of the two nonwoven layers must exhibit less shrinkage than the surface structure located in the center of the composite.

The shrink or shrunken surface of the laminate may consist of a uniaxially or biaxially stretched film. The foil can be made by known methods, for example by blowing method, i.e. stretched in a tubular form. However, it can also be made by extrusion through a wide-slot die and elongated by mechanical stressing in the machine running direction or transversely to this direction by means of a tension frame or by passing through a pair of mutually engaging rolls covered with longitudinal grooves.

A typical film stretching ratio is up to 5: 1 in one or both stretching directions. By stretching ratio is meant the ratio of the length of the film after stretching and before stretching.

The extrusion film product may contain known fillers or structurants, for example inorganic particles like chalk, talc or kaolin. Thanks to these substances, during tensioning, a microporous structure can be created, which is characterized by a better ability to "breathe".

However, the foil can also be perforated prior to stretching using known methods, whereby the stretching results in an enlargement of the perforation.

Before stretching, it is also possible to make slit cuts in the foil, from which, during the stretching, in particular at an angle of 90 ° to the longitudinal dimension of the slots, perforations are formed.

Before stretching, the foil can be weakened in the form of a pattern, which, when stretched, widens to form perforations. The pattern weakening of the film can be effected by passing through the calender, that is to say under the action of heat and pressure or by ultrasonic treatment.

Regardless of whether the foil is perforated, provided with a weakening pattern or slotted, it can consist of one layer or several, i.e. at least two, layers obtained by coextrusion. Either or both of the outer layers of the coextruded film may be made of lower melting thermoplastics than the other layer or middle layer. The fibers surrounding the shrink film of the nonwoven layers may only be bonded to the lower melting layer (s) of the coextruded film, not to the middle layer.

When the film is used as a shrink or shrink laminate surface, a certain increase in the strength of the laminate is achieved. At the same time, the foil prevents the migration of the lotion applied from the upper laminate layers to the lower layers thereof when the nonwoven laminate is bundled or commercially available as a moisturizing wipe.

The shrink or shrunken surface of the laminate may consist of a loose fiber fleece of 100% shrink, i.e. highly stretched, fibers made by conventional non-woven laying techniques. The fibers can be arranged isotropically or in a preferential direction, that is, anisotropically. The fiber fleece may be pre-reinforced with at least one non-shrink nonwoven layer prior to lamination, the reinforcement parameters being controlled so as to have little effect on shrinkage at most. The fleece of shrink fibers may contain fibers of the same or different titer. The titer of these fibers is usually in the range of about 0.5 to about 50 dtex, preferably between 0.8 and 20 dtex. The fibers that make up the shrink or shrunken non-woven or fleece can be a wide variety of fibers, e.g. identical to the polymer of homogeneous fibers, for example in a mixture of homogeneous polypropylene fibers with bicomponent polypropylene fibers6

Polyethylene with a side-by-side structure or a core-sheath structure. In the latter case, the casing is made of polyethylene which acts as a binder to fix one or two non-contracting fibrous surface structures on one or both sides of the contractile fiber layer.

The shrinking or shrunken fleece or non-woven layer can be perforated by known methods or have a mesh structure.

Preference is given to methods of perforation or production of a deletion structure that rely on the principle of shifting the fibers to one side and thus creating a pattern. Non-destructive methods are disclosed in EP-A-919,212 and EP-A-789,793.

The perforation methods described above for the film can also be used.

A monoaxially or biaxially stretched, extruded plastic mesh can also be used as the shrink or shrink layer of the composite structure. The degree of stress in both directions may be the same or different.

Preferably, however, a strong stretch is applied in at least one privileged direction. By strong stretching is meant a stretching ratio of at least 3: 1.

The thread thicknesses are preferably in the range 150 to 2000 µm. Extruded plastic meshes are understood to mean surface structures with a mesh structure, which are created in such a way that the first parallel monofilament bundles intersect with second, also parallel monofilament bundles at a defined constant angle and are spontaneously welded at the crossing points. In plastic meshes, both monofilament bundles are usually made of the same polymer. However, the thickness and the degree of stretching of the two filament bundles may be different.

Mats which differ from plastic nets can also be used as shrink or shrunken surfaces in that the intersecting filament bundles are not intrinsically connected to each other at the crossing points, but by means of a binder, for example aqueous polymer dispersions. In this case, the two parallel monofilament bundles may be of different polymers. As a rule, the mats are only suitable for use in the present invention when at least one of the two filament bundles is under tension. In the case of mats, you can use both stretched monofilament threads and homogeneous filaments. In principle, the angle of intersection of the beams is arbitrary, but an angle of 90 ° is preferred for practical reasons. One filament bundles in the plastic mat or mesh are preferably parallel to the machine running direction, and the other filament bundles are transversely oriented, i.e. from a 90 ° angle, to the machine running direction. The spacing between the first parallel filaments extending in the machine direction is typically in the range of about 05 to about 20 mm, preferably between 2 and 10 mm, and the spacing of the second parallel filament bundles is typically between 3 and 200 mm. The shrinkage of the first filament bundles is usually from more than 50 to 100%, preferably from 70 to 100%, especially 100% of the total area shrinkage. In the latter case, exactly shaped undulations or waves are produced.

The shrinkage of the second filament bundles is usually from 0 to 50%, preferably from 0 to 30%, especially 0% of the total area shrinkage.

Woven or knitted fabrics can also be used in addition to the shrink or shrunken surfaces described above, provided that the contractile or shrunken fibers run in at least one of the two preferred directions, that is, for a fabric in the weft or warp direction.

The nonwoven fabric used for shrinkage may be subjected to an elongation process prior to being laminated to form a composite. Preferably, the non-woven fabric is elongated by means of mechanical forces acting in the machine running direction, where - if the non-woven fabric consists of fully stretched fibers - a corresponding shortening in the transverse direction, i.e. a loss in width, takes place.

These processes called "neck-in-stretch" cause a marked change in the orientation of the fibers in the non-woven fabric in the direction of the applied tension. Such a change of orientation can be facilitated if, during tensioning, the bonds inside the nonwoven fabric are broken or strongly loosened due to the increase in temperature, and the change in fiber orientation is fixed by cooling to room temperature. Such changes in fiber orientation are advantageous if the non-woven fabric was initially isotropic or only a small part of the fibers were oriented in a privileged direction, or if shrinkage is to occur in only one direction and the non-woven fabric is to exhibit a pronounced ripple.

PL 205 539 B1

In order to determine the water-holding capacity of laminates according to the invention, the water-holding capacity is determined in accordance with DIN 53923 by the "basket" method. Appropriate measuring equipment for this purpose is described in more detail in DIN 53923. After 1/100 g (dry matter weight) of the non-woven fabric sample that has been cut out is weighed, it is placed in a wire basket and loaded with a plate 10 × 10 cm. The sample is under load for 30 seconds and unloaded for 30 seconds. After this time has elapsed, the sample is removed from the water with tweezers to drain and suspended, holding it in the corner with a metal clamp. After 120 seconds of dripping, the sample is weighed to 1/100 g (wet weight).

The absolute water absorption is calculated as follows:

Absolute water absorption [g / m²] = (weight of wet substance - weight of dry substance) * 100 [g / m²]

Relative water uptake [%] = (absolute water uptake [g / m²] / grammage [g / m²] * 100%

As an indicator of the volume / fluffiness of the composite according to the invention, i.e. the increase in volume that occurs after shrinkage into the form of alternating protrusions and recesses, the fluffiness (B) of the material in the unshrunken and shrunken state is assumed, and on this basis the shrinkage (SB) is determined. The material thickness is determined with a dial thickness gauge at a pressure of 8 g / cm².

Bulky (B) = material thickness (mm) / grammage (g / m)²)

Shrinkage (SB) = [Shrinkage after shrinkage / Shrinkage before shrinkage] * 100%

The method for producing the above-described three-dimensional structure water-absorbent fiber fabric comprises, according to the invention, the steps of using a combination of at least one fiber fleece and / or non-woven fabric with a shrink fabric, then manufacturing, preferably by heat and pressure, a calender and / or with ultrasound, the welded connection between the fiber fleece and / or the non-woven fabric and the shrinkage surface in the form of a linear pattern extending at least perpendicular to the direction of the strongest contraction of the shrinkage surface structure, and finally on heating the obtained composite to such a temperature that the shrinkage of the contractile surface structure is initiated and a regular occurrence is formed alternately in relation to the surface of the protrusion and the recess, spaces are formed between the non-woven fabric layer and the shrunken surface structure on the alternating protrusions and recesses, which condition the absorption of liquid by the surface structure and thus reduce the density of the non-woven fabric and increase its volume and fluffiness.

The thermal welding of the fiber fleece and / or the non-woven fabric and the shrink surface can be carried out in any way, for example by calendering with an embossing calender, one roller of which has a regular linear pattern, or by welding with ultrasound or infrared rays acting on the non-woven fabric. within a given pattern.

The composite according to the invention is characterized by high thickness in relation to low basis weight, i.e. low density with high water absorption capacity. The alternating protuberances and indentations create a space for low to high viscosity fluids, multi-phase fluid systems such as floating substances, dispersions and emulsions, and other dispersion systems, also containing solids, as well as solid particles and dust from air or gases. These fluids or solid particles may partially or completely fill the spaces between the alternating protrusions and depressions, they may also only cover the surface of the composite according to the invention with a layer.

The composite according to the invention is used, in particular, as moisturizing wipes, e.g. for infant care, in cosmetics, for skin care, for removing dust or dirt in the household or industry, as a fluid reservoir for cleaning or applying liquids, e.g. medical or cosmetic substances. These uses are also an object of the present invention.

The subject matter of the invention is illustrated in the drawings in which Fig. 1 shows an example of undulations (hillocks / corrugations), Figs. 2a, 2b and 2c - details in Fig. 1, Figs. 3 and 4 - the surface of a calender roll, Fig. 5a and 5b - case of shrinkage amounting to 50% in the machine running direction and in the transverse direction, Fig. 6a and 6b - composite with linear shrinkage in the transverse direction of the machine operation, Fig. 7a and 7b - composite with linear shrinkage in the machine running direction, Figs. 8a and 8b - composite with linear shrinkage in and transverse to the machine running direction, and Fig. 9 - composite of Fig. 8b in perspective view.

PL 205 539 B1

One of the numerous variants of the fiber fabric according to the invention is shown schematically in Fig. 1. In this case, the composite consists of a total of three nonwoven layers.

The nonwoven fabric layers 1 and 2 are non-contracted fleece or nonwoven layers which have been welded in the form of unbroken lines by pressure and temperature or by ultrasonic welding to the fiber fleece of the third nonwoven layer 7 located in the center of the composite before shrinkage. The three layers of non-woven fabric are integrally connected to each other on rib- or line-shaped, mutually parallel welding areas 5.

In the composite shown in Fig. 1, both the fiber mixtures and the basis weight of both non-woven layers 1 and 2 are identical, so that after shrinkage of the non-woven layer 7, a double wave is formed, the cross-section of which shows a precise mirror symmetry and which has the same height on both sides. 10 and 11. The term wave height is understood to mean the maximum distance of the wave from the center of the composite. In the area of ​​the peaks 3 and 4 of the mirror symmetrical waves, the fibers of the layers 1 and 2 of the nonwoven fabric are least compressed. The degree of compression increases from the peaks 3 or 4 to the welding area 5 and reaches its absolute maximum there. The shrunken non-woven layer 7 is bound weakest in the center 7a between the welding rib regions 5, and most strongly within the welding regions 5.

Of course, the nonwoven fabric layers 1 and 2 may also have different structures and different grammages. In the case of Fig. 1, the shrinkage occurred only in the direction of line 9-9, this direction being identical to the machine running direction (longitudinal direction). The wavy reliefs of the nonwoven layers 1 and 2 give rise to voids 12 and 13 also arranged in a mirror symmetry pattern.

In Figures 2a, 2b and 2c, the upper half of the mirror fold is shown in a section along line 9-9. The fold extends, as can be seen in FIG. 2a, from one welding area 5 through the apex 3 to the other welding area 5. The inflection points c1 and d1 of the fold, i.e. "the fluffiness of the fold, are strongly dependent on the drape or deformability of the nonwoven layers 1 and 2. Fig. 2a shows a non-woven fabric with greater stiffness (lower drape) than in Fig. 2b. With very low weights of nonwovens with very little or only point bonding within the nonwoven layer, the crease tip 14 may collapse due to insufficient stiffness, as shown in FIG. 2c. Two new vertices 13 then arise, which are ideally situated symmetrically with respect to the axis of symmetry g and have the same shape.

The height ratio a / 0.5b and the folds to half the distance b / 2 between two adjacent welding areas 5 and the drapeability of the two fleece layers 1 and 2 essentially determine the shape of the fold. The height a with respect to b / 2 is determined by the ratio of the spacing of the welding areas 5 before and after shrinkage. The greater this ratio (b before) to (b after), the greater the ratio a / 0.5 (b after). The proportion of the surface area in the composite, occupied by the corrugations or the waves, in relation to the total area after shrinkage also depends on the proportion of areas unbound with the layer 7 before shrinkage, i.e. after strengthening to the composite form, and the degree of surface reduction as a result of shrinkage. The number of folds or waves per m² also depends on the amount of surface shrinkage. The size of the folds or waves or the distance b after shrinkage is also determined by the size of the areas not bound by the welding areas 5 and the ratio of the areas after and before shrinkage.

The shape of the convexities or bulges in the shrunken composite or their deformation after shrinkage depend on the shape of the surfaces not connected to the middle layer 7 in the bonding areas or welding areas 5, the shrinkage of the entire surface and the shrinkage ratio in the machine running direction and in the transverse direction. In the case of highly stretched mono- or multifilaments arranged in the composite parallel to the machine running direction (or generally in the privileged direction), there is a so-called linear shrinkage, which means a shrinkage in this privileged direction only.

In various embodiments of the invention, the fibers, or portions of the mixture of non-shrink fibers, the outer nonwoven layers of the three-layer composite must more or less follow the shrinking middle layer. The softness or the stiffness of these three-dimensional structured outer layers can be varied within wide limits by appropriately selecting the fibers. The design of these three-dimensional nonwoven layers depends to a large extent on the properties required or the intended use of the composite.

For the shaping of the two outer layers of the composite, which are given a three-dimensional structure, as well as for the integrity of their structure, it is important that the shrinkage is

The middle layer has a porous structure, or is airtight or impermeable, that is, whether it consists of fibers, meshes, mats or impermeable films.

When using a film, the force required to separate the three-dimensional layers of nonwoven and film is solely determined by the bond quality of the fibers and the film at the interface between these materials. The foil acts as a separating layer for the upper and lower three-dimensional nonwoven layers. In order to achieve sufficient separation / bonding forces between the film and the three-dimensional nonwoven layer, it is preferred that the film and the fibers (at least part of the fiber mixture) adhere to each other. This is achieved in a known manner so that the films and the fibers or the component of the bicomponent fibers or parts of the fiber mixture are of chemically similar or identical polymers. If, for example, a biaxially blown PPO film is used as the shrink film, it is advantageous for good adhesion if at least a high percentage of at least 20-30% by weight) of the three-dimensional nonwoven fabric layer also consists of homogeneous polyolefin fibers or made of polyolefin copolymer, and in the case of bicomponent fibers, binding, the lower melting component is polyolefin.

Examples of such fibers with good adhesion to the PP sheath are PP, PP copolymer, PE or PE copolymer fibers or bicomponent fibers, the core of which is, for example, polyester and the fabric PP, PE or their copolymers. The fibrous polymer, which acts as a binder component, can also be replaced with a tackiness enhancer or with a plasticizer. In order to avoid damage or destruction during ultrasonic welding or under the influence of temperature and pressure of the fiber fleece on the foil, the melting or softening point of the lower melting fiber components should not be higher than the corresponding temperature of the stretched foil, and preferably it should be at least 5 to 10 ° C. C lower than the melting or softening point of the film.

Another possibility of securing the foil or the foil core against mechanical damage or weakening is to use a coextruded, on both sides or on one side, stretched foil. Within the scope of the present description, this is understood to mean a 2-layer to 3-layer film, the core of which is made of a polymer with a higher thermal resistance than the polymer that forms one or both of the outer layers. As an example, there may be mentioned a three-layer stretched PPO film as the core and two (usually lighter) outer layers of polyethylene, polyolefin copolymers or EVA ethylene vinyl acetate compolymer).

If, according to the invention, stretched meshes or mats are used for the shrink layer, matching the polymer composition of the three-dimensional nonwoven fibers to the shrinking middle layer for adhesion between the nonwoven and the net plays little or no role. The area occupied by the oriented monofilaments in the longitudinal and transverse directions in the mat / mesh is negligible compared to the total area. The bonding of the two layers of non-woven fabric above and below the mat / net occurs essentially through open surfaces not occupied by filaments. The adhesion of the fibers to the mat / mesh monofilaments is generally negligible. For a sufficient bonding of the composite, it is advantageous if the upper three-dimensional nonwoven layer consists of the same or chemically similar, i.e. compatible, binder fibers as the mat / mesh fibers, and their function in the two nonwoven layers may be the same or different.

The tensioned net can be coextruded similar to the film, and for the reasons mentioned above, the use of the coextruded net does not contribute significantly to the bonding of the entire composite.

It has proven advantageous to carry out the production of the 2-layer or 3-layer composite and shrink it to obtain the three-dimensional composite in separate steps. In addition, it is preferable to select the binder fibers which provide greater structural integrity to the composite such that their softening or hot-tacking interval is at least 10 ° C, preferably at least 15 ° C, below the corresponding interval for the shrink layer. It has proven advantageous to produce three-dimensional structures by shrinkage according to the invention in terms of process control, uniformity of surface shrinkage, and quality of the three-dimensional structure, by operating the process in two separate steps. Combining the two process steps in the case of heat and pressure lamination is possible in the calender gap or by looping around the heated calender roll to increase the residence time of the product, but is less preferred due to the drastic reduction in production speed.

PL 205 539 B1

Fig. 3a shows a top view of the surface of a calender roll with recesses in the form of equilateral hexagons. An equilateral hexagon is in fact precisely defined already by its area 17 and length 19 sides. In order to define the hexagon more precisely, Fig. 3a also shows the length 20 from the top to the bottom apex, i.e. in the machine running direction 27, and the width in the transverse direction of the machine running direction. The two shortest distances 16 and 18 between equilateral hexagons are identical and define the frames of the hexagon and therefore the uninterrupted welding lines or the honeycomb welding pattern in an unshrunken composite welded by heat and pressure or by ultrasound.

Fig. 3b shows a case of a composite shrunk solely in the machine direction 27, the shrinkage being linear and amounting to 50%. This is the case, for example, when an extruded mesh is used as the shrink fabric, which has only been tensioned in advance in the direction of the machine.

As a result, 50% shrinkage in only one privileged direction (e.g. machine direction) in the composite shortens the distance 20 to the distance 26 and also halves the length of 19 sides to the length 25, while the distance 21 before and after shrinkage is left without changes. The area 17 of the equilateral hexagon decreases to the area 23, and the equilateral hexagon before contraction is a non-equilateral hexagon compressed by 50% in the machine direction. Hence, the equal gaps 16 and 18 transform into unequal gaps 22 and 24 after contraction, with 24> 22.

Fig. 4a shows the same surface of the calender roll as in Fig. 3a.

Fig. 4b shows a case of a composite that is shrunk only in the transverse direction 27, this shrinkage is linear and amounts to 50%. This is the case, for example, when an extruded mesh is used as the shrinkage surface, which has only been previously tensioned in a direction perpendicular to the running direction of the machine.

As a result, a 50% shrinkage in only one privileged direction in the composite shortens the distance 21 to the distance 28 by half, while the distance 20 before and after shrinkage remains unchanged. The area 17 of the equilateral hexagon decreases to the area 29, and the equilateral hexagon before contraction is a non-equilateral hexagon, compressed in the direction perpendicular to the machine running direction by 50%. Hence, the equal gaps 16 and 18 transform into unequal gaps 30 and 31 after contraction, with 31> 30.

Figures 5a and 5b show a case of shrinkage of 50% in the machine running direction and in the transverse direction. The total shrinkage is 75%. In this case, the equilateral hexagons shrink accordingly, maintaining equilateral. The shortest distances between the sides are reduced by 50%.

Fig. 6a shows a highly enlarged top view of the composite before shrinkage. The composite is bonded across the entire width 34 of the product in parallel lines or beams with a thickness of 33, an area 32 and a gap 35 under the action of heat and pressure or by means of ultrasound. This pressure bond is referred to herein as LS (linear seal).

The condition shown in Fig. 6b is created after about 25% shrinkage in the direction transverse to the machine running direction only. Thus, the product width 34 in Fig. 6a is reduced by 25% to the product width 38 in Fig. 6b. Due to the fact that there is no shrinkage in the machine running direction, the thickness of the beams remains the same, i.e. the dimension 33 corresponds to 37, and the distance between the beams and each other also remains constant, i.e. 35 corresponds to 39.

Figures 7a and 7b also show a greatly enlarged top view of the LS bonded composite before shrinkage. In this case, 23% shrinkage occurs only in the machine running direction 48. The width of the product remains correspondingly unchanged (assuming there are no snags), as does the length of the beams, i.e. 42 corresponds to 46. The area of ​​the 40 beams before shrinkage decreased by 23% to the area 44 after shrinkage, similarly, the spacing of 43 beams before shrinkage decreased by 23% to the spacing 47 after shrinkage and accordingly, the width of the beams 41 before shrinkage decreased to the width 45 after shrinkage.

The top view of the three-layer composite shown in Fig. 7b with a purely linear shrinkage in the machine direction gives a perspective view similar to that in Fig. 1, with clearly shaped waves, the height of the 11 waves at their peak point 3 along line 49. is constant across the width of the product.

PL 205 539 B1

A case of shrinkage of a three-layer composite having for example a non-woven / shrink film / non-woven structure is shown in Figures 8a and 8b, i.e. both the beam bonding area 52 and the beam spacing 53 decrease correspondingly to the shrinkage in the machine direction and in the direction of the machine. transverse to dimensions 54 or 55, respectively.

Fig. 9 is a perspective view of the composite of Fig. 8b, with a sectional view taken along line 57 and a condition along line 56.

It can be seen that the height of the folds along the line 56 is not always the same over the entire width of the product, but that microflows 58 are formed on them as a result of the transverse contraction.

The subject matter of the invention is elucidated on the basis of the following examples, which, however, are not intended to limit it.

Example 1

A carding machine with a cross-folding machine (marked K1), a carding machine over the fiber-laying belt (marked K2) with the staple fiber laying in the direction of the machine operation was used for laying the fleece, and again a carding machine with a cross-folding machine (marked K3). In this way, it was possible to implement a three-dimensional composite non-woven structure. The fiber fleece layers laid with K1, K2 and K3 are designated F1, F2 and F3, respectively.

Both the composition of the fibers, their orientation as well as the basis weight of F1 and F3 were identical. Details on basis weight and fiber types are provided in Table 1 (Examples 1a, 1b). Constructed of the three webs F1, F2 and F3, the three layer composite was lightly pressed at 80 ° C by passing through two steel press rolls heated to 80 ° C before being fed to a pair of calender rolls.

The calender pair consisted of a smooth steel roller and an engraved steel roller. The engraved steel roller was covered with straight lines or stripes 1.0 mm wide, parallel to each other and transverse to the machine direction. The welding area was 25%. The convexities of the stripes were conical in shape. The engraving depth was 0.9 mm. The distance of the parallel strips was 4.0 mm, measured from the center of one strip to the center of the other.

Both rollers were heated to a temperature of 130 ° C. The linear pressure was 65 N / mm. Due to the symmetrical structure of the three-layer composite, i.e., due to the fact that F1 was identical to F3, it did not matter which of the two runs touched the engraved roll as they passed through the calender.

The product, strengthened in this way under the action of heat and pressure, was subjected to thermal treatment. After shrinkage of the middle layer F2 of the three-layer nonwoven composite in an oven at 160 ° C for 90 seconds, the resulting corrugations shown in FIG. 1 directed on both sides into the third dimension of corrugation were formed. Despite the completely symmetrical structure of the composite composed of F1, F2 and F3, the peaks of the corrugations on the side of the engraved cylinder were slightly higher than those facing the smooth steel cylinder during calendering. The differences in the height of the tops on both sides of the shrunken layer F2 turned out to be smaller, the greater the engraving depth.

Table 1 shows the results of the measurements carried out in Example 1 and the shrinkage in the longitudinal and transverse directions of the product as well as the shrinkage in the area. The basis weight, absolute and relative water absorption were measured on the basis of the "basket test according to DIN 53923, before and after the shrinkage process, as well as the shrinkage (SB) and the thickness of the material.

To make the composite described in example 2, two carding machines were needed to place a layer of fibers F1 in the machine direction (md), and one additional card to lay the fleece F3. Both runes had the same structure in the example. Between the two fleece a fully tensioned, only in the md direction, a PP mesh with a mesh size of 3.3 * 8.5 mm and a grammage of about 30.0 g / m was introduced.². The three layers S1, S2 and S3 were fed, as in Example 1, after hot pre-pressing for further densification, into a calender gap consisting of the rolls already mentioned in Example 1. Calendering was carried out with a linear pressure of 65 N / mm. The sample was then left for 30 seconds in a drying cabinet at 150 ° C. Table 2 shows the results of the measurements from example 2. The basis weight, absolute and relative water absorption were measured on the basis of the "basket test according to DIN 53923, before and after the shrinkage process, as well as the shrinkage (SB) and the thickness of the material.

PL 205 539 B1

Example 3

Example 3 differs from Example 2 only in that a uniaxially stretched film is interposed between the two fiber webs F1 and F2. Table 2 shows the results of the measurements of Example 3. The basis weight, absolute and relative water cooling were measured using the "basket test according to DIN 53923, before and after the shrinkage process, as well as shrinkage (SB) and material thickness).

Table 1

<td></td><td>Example 1a</td><td>Example 1 b</td>

<td>Fiber fleece F1</td><td>65% dtex viscose 1.4 fiber length 40 mm 35% single-component fibers polypropylene / copolypropylene dtex 2.2 fiber length 51 mm</td><td>80% dtex viscose 1.4, fiber length 40 mm 20% polypropylene / polyethylene bi-component fibers 4.8 dtex 1.7 fiber length 51 mm</td>

<td>Fiber fleece F2</td><td>100% dtex 6.7 polypropylene fibers fiber length 90 mm</td><td>100% polypropylene fibers dtex 6.7 fiber length 90 mm</td>

<td>Fiber fleece F3</td><td>65% dtex viscose 1.4 fiber length 40 mm 35% single-component fibers polypropylene / copolypropylene dtex 2.2 fiber length 51 mm</td><td>80% dtex viscose 1.4, fiber length 40 mm 20% bicomponent fibers polypropylene / polyethylene dtex 1.7 fiber length 51 mm</td>

<td>Grammage before shrinkage</td><td>38 gsm²</td><td>55 g / m²</td>

<td>Weight after shrinkage</td><td>90 g / m²</td><td>124 g / m²</td>

<td>Absolute water absorption before shrinkage</td><td>340 g / m²</td><td>810 g / m²</td>

<td>Absolute water absorption after shrinkage</td><td>980 gsm²</td><td>1254 g / m²</td>

<td>Relative water absorption before shrinkage</td><td> 895%</td><td> 810%</td>

<td>Relative water absorption after shrinkage</td><td> 1090%</td><td> 1254%</td>

<td>Shrinkage (SB)</td><td> 208%</td><td> 175%</td>

<td>Thickness after shrinkage (mm)</td><td> 2,2</td><td> 1,5</td>

Table 2

<td></td><td>Example 2</td><td>Example 3</td>

<td> 1</td><td> 2</td><td> 3</td>

<td>Textile fleece F1 = S1</td><td>80% dtex viscose 1.4, fiber length 40 mm 20% bicomponent fibers polypropylene / polyethylene dtex 1.7 fiber length 51 mm</td><td>80% dtex viscose 1.4, fiber length 40 mm 20% bicomponent fibers polypropylene / polyethylene dtex 1.7 fiber length 51 mm</td>

<td>Intermediate tier = S2</td><td>PP mesh mat, uniaxially tensioned</td><td>PPO foil 15 μιτι under uniaxial tension</td>

PL 205 539 B1 cont. table 2

<td> 1</td><td> 2</td><td> 3</td>

<td>Fiber fleece F3 = S3</td><td>80% dtex viscose 1.4, fiber length 40 mm 20% bi-component fibers polypropylene / polyethylene dtex 1.7 fiber length 51 mm</td><td>80% dtex viscose 1.4, fiber length 40 mm 35% bicomponent fibers polypropylene / polyethylene dtex 1.7 fiber length 51 mm</td>

<td>Grammage before shrinkage</td><td>45 g / m2²</td><td>55 g / m²</td>

<td>Weight after shrinkage</td><td>94 gsm²</td><td>124 g / m²</td>

<td>Absolute water absorption before shrinkage</td><td>272 gsm²</td><td>810 g / m²</td>

<td>Absolute water absorption after shrinkage</td><td>1034 g / m²</td><td>1254 g / m²</td>

<td>Relative water absorption before shrinkage</td><td> 605%</td><td> 810%</td>

<td>Relative water absorption after shrinkage</td><td> 1100%</td><td> 1254%</td>

<td>Shrinkage (SB)</td><td> 185%</td><td> 362%</td>

<td>Thickness after shrinkage (mm)</td><td> 1,7</td><td> 2,0</td>

Patent claims