WO1999024649A1 - Monofil for and for producing bristles or interdental cleaning elements, bristle products with bristles of this type and interdental cleaning elements - Google Patents

Abstract

The invention relates to a monofil which has reduced secondary bonding forces and which consists of at least two coextruded polymers, for producing bristles or interdental cleaning elements which can be slit in an essentially axial direction by means of mechanical forces. The aim of the invention is to obtain defined slits or flags. To this end, the two polymers contained in the monofil have a geometrically regular arrangement with the boundary layers in which the reduced secondary bonding forces are present running in an essentially axial direction.

Description

 Monofilament for and for the production of bristles or interdental cleaners, as well as bristle goods with such bristles and interdental cleaners

The invention relates to a monofilament with reduced secondary binding forces from at least two co-extruded polymers for the production of bristles or interdental cleaners which can be slit essentially in the axial direction by the action of mechanical forces. Furthermore, the invention is directed to a method for producing bristles or interdental cleaners from such monofilaments and to bristle products with such bristles or to interdental cleaners.

Bristles for bristle products of any kind, for example brushes for personal and dental care, household brushes, technical brushes, brushes and the like, are today predominantly made of polymers by extruding the polymer melt to form endless monofilaments, stretching and possibly stabilizing the monofilaments. Such monofilaments are then turned into the desired length by cutting the bristles receive. As a rule, the monofilaments, like the

Bristles, circular cylindrical cross section. For special purposes, bristles with other, e.g. oval or polygonal cross section known. The monofilament is then extruded with an appropriate profile.

In many cases it is desirable to use bristles in a fibrous, in particular fine-fibrous structure at the end of use. This applies, for example, to those bristle products which are used to apply media to surfaces or the like. are determined, e.g. Brush. Even if a fluffy structure is desired, the bristle must be fine-grained. In recent times, findings have also become established in dental medicine, according to which conventional toothbrush bristles are inadequate in their cleaning action, since they do not penetrate into the fine fissures of the tooth surface, but slide over it. The same applies to the cleaning effect in the interdental area.

In order to obtain highly fibrous structures, it has already been proposed to extrude the monofilament from polymer mixtures. The following effects are used here: during extrusion and subsequent stretching of the monofilament, the polymer molecules are oriented in the longitudinal direction of the monofilament. The primary binding forces acting in the longitudinal direction ensure high tensile strength. The longitudinal orientation of the molecules also brings the desired bending elasticity. In the case of monofilaments made from a single polymer, the so-called secondary binding forces, namely the forces transverse to the molecular extension, are sufficiently large to prevent the monofilament or the bristle from being frayed or fanned out. For monofilaments made from two different, mixed polymers On the other hand, sliding zones arise between the molecular chains of the polymers during stretching, in which the secondary binding forces are reduced. Such a monofilament or a bristle made from it can be shredded by the action of mechanical forces using cutting-like tools. The resulting so-called flags have a very irregular shape, irregular cross sections and frayed outer surfaces. In a larger dressing of such bristles, a fluffy and well-absorbent structure is achieved, but the flags have uncontrolled strength properties. They tear away, break off or lie down. Bristles frayed in this way are consequently unsatisfactory and even unsuitable for many applications. The use of toothbrushes is questionable for hygienic reasons.

The same disadvantages have a known embodiment of a bristle (WO97 / 1 830), which has a core and a jacket, which are produced by coextrusion of two different polymers. At the end of the bristle on the use side, the core material is removed mechanically or chemically to form a recessed pocket which is to hold dentifrices or paint. Furthermore, the formation of flags ("flags") is described, which are obtained by shredding the material of the jacket, insofar as it extends above the core. This shredding is also done in the conventional way by means of knives and therefore leads to the same irregular structures.

Therefore, bristles have been proposed, in particular for toothbrushes, which consist of a large number of thin fibers similar to textile fibers and a sheath enveloping the fibers (DE 94 08 268 Ul). Coat and Fibers can also be co-extruded as filaments. After cutting to the bristle length, the sheath at the end of the bristle on the use side is removed by mechanical processing or cutting, so that the fibers are exposed over a short length. Apart from the complex manufacture of such bristles, they can only be used to a limited extent. The sudden change in the bending behavior at the transition from the fibers to the jacket is particularly disadvantageous. If such bristles are used in applicators, it can be used

Damage to the surface due to the hard transition. The same applies to the use of such bristles in toothbrushes with regard to the effect on the teeth and gums. In addition, the fibers are practically limp, so that they or the like in thicker depressions, interdental spaces. cannot or cannot penetrate sufficiently. The fibers also break off easily at the edge of the jacket during long-term use.

Interdental cleaners can also be formed from bristle-like monofilaments, which, however, should be structured on their surface. This is achieved, for example, by flocking.

The invention is based on the object of proposing a monofilament composed of at least two common extruded polymers which is suitable for producing slotted bristles or interdental cleaners with reproducible strength properties and flags or slots which can be defined in terms of number, shape and dimensions. Furthermore, the invention is intended to propose a method for producing bristles or interdental cleaners from such monofilaments. A monofilament solving this problem is characterized according to the invention in that it has at least two. Polymers in a geometrically regular arrangement with boundary layers running essentially in the axial direction, in which the reduced secondary binding forces prevail.

Extrusion tests have shown that it is possible to extrude the at least two different polymers in such a way that flat interfaces are formed between the polymers in which the secondary binding forces are greatly reduced. The geometry of the boundary layers makes it possible to determine in advance how the monofilament, for example for an interdental cleaner, or the bristle produced from the monofilament by sound is split or split by the action of mechanical forces. The slots or flags are created exactly in the contour specified by the geometry of the extrudate. Since the boundary layers extend in the longitudinal direction of the monofilament, each individual flag has the same shape and cross-section over its entire length. All flags therefore have the same strength properties, in particular the same bending behavior and the same tensile strength. However, it is also possible to generate flags with different cross sections by appropriate design of the geometry. Since the monofilament or the bristle, when subjected to mechanical forces, slits and splits exclusively and exactly at the boundary layers, the flags can form edges with a corresponding cross-sectional shape on the facing surfaces, which support the cleaning effect. A bristle split in this way is consequently also more effective on its outer surface than conventional bristles. The bristle spreads due to the congruent shapes not too much on. In a tightly packed bundle of such bristles, each bristle takes on a monofilament shape again and the flags only come into full effect through axial or radial pressure. This means that media can be easily absorbed and released again when applied by pressure.

In a preferred embodiment it is provided that the monofilament has a matrix of the polymer determining the physical and chemical properties of the bristle or of the interdental cleaner, and that the second polymer is embedded in the matrix in the form of thin layers. The second polymer itself can form the boundary layer with reduced secondary binding forces.

In this way, bristles can be produced whose flags have the favorable properties of conventional bristles. On the other hand, there are no fines or only a small amount during splitting, so that the bristle does not have to be subjected to extensive cleaning processes. Defined flagged bristles or defined slotted monofilaments for interdental cleaners are obtained, in which further splitting or slitting can be avoided.

The polymer of the matrix, as well as the thin layers, can be a copolymer or a polymer mixture. The advantages mentioned above are optimally achieved, in particular, if the thin layers contain a proportion of the polymer of the matrix. In this case, the polymer or the bristle tears open at the weakest point, namely approximately in the middle of the thin layers, but the adhesion of the remaining layers is due to the polymer corresponding to the matrix. proportion of the resulting neighboring flags is large enough to avoid the formation of fine particles.

The thin layers preferably have a thickness of a few μm. Practical extrusion tests have shown that such thin layers can be coextruded with the polymer of the matrix.

The two polymers can be present in approximately equal proportions in the thin layers.

The specific design of the geometry is determined by the desired properties of the bristle or the interdental cleaner. Thus, the thin layers in the matrix can extend to the circumference of the monofilament, so that the monofilament can be slit or split with relatively little force.

Instead, it is possible that the thin layers in the matrix end at a distance from the circumference of the monofilament. In this case, a somewhat greater force is required, but it is advantageous here that the resulting flags also consist of the matrix material in the edge region, that is to say they have the same wear properties as the coat of the bristle or the flags.

Optionally, the matrix of the monofilament can have a third polymer embedded in the matrix, which primarily serves to influence the strength properties of the flags that are created.

As with bristles, the monofilament can usually have a circular shape, but also a shape that deviates from the circular shape Have cross-section. Polygonal cross-sections are to be mentioned here in particular, which are more effective in cleaning than round cross-sections.

In this case, the thin layers can run out to the corners of the polygonal cross section, so that relatively sharp edges with an edge angle of less than 90 ° arise.

Instead, the thin layers can also run out to the surfaces of the polygonal cross-section, in which case edges with an edge angle in the range of 90 ° can then be realized.

In a preferred embodiment, the matrix consists of polyamide and the thin layers consist of a polyolefin, in particular polypropylene or polyethylene. This material pairing has sufficient secondary binding forces at the interfaces to prevent untimely tearing or slitting during processing and use of the bristles. However, the polymer composite breaks when there is a strong and targeted application of force.

The process according to the invention for producing bristles from the monofilament described above is distinguished according to the invention in that the at least two polymers are coextruded to form the monofilament, the monofilament is stretched and optionally stabilized, the monofilament is cut to the desired length of the bristles and the Bristle is split at its use end by the action of mechanical forces across the bristle axis over a limited length along the boundary layers. Instead, both bristle and interdental cleaners can be manufactured in such a way that the at least two polymers are coextruded to form the monofilament, and that the monofilament after extrusion, ner stretching and, if appropriate, stabilization by the action of mechanical forces transverse to the monofilament axis _. locally limited length is slit along the boundary layers. By means of the method according to the invention, fisure-like slots can be formed on the jacket of the monofilament, which slots can be used to hold media. In the case of toothbrushes or interdental cleaners, dental care products or dental medicine or antibacterial preparations are particularly suitable. In addition, the monofilament interdental cleaner on the jacket gets an increased roughness due to the slitting.

Interdental cleaners of any length can be produced from the aforementioned monofilament. The same measure can of course also be carried out on the bristle cut to length from the monofilament. The location of the slit and the extent of the slit can be matched to the length of the bristle in order to either avoid splitting the bristle end or to promote it in a targeted manner. For example, only the bristle end can be split. After the flags have been worn, the slots on the jacket can be used to further split the bristle. Depending on the type and number of layers stored, there is a corresponding number of flags at the end of use of the bristle.

In the case of processing the monofilament into an interdental cleaner of any length, it is provided according to a variant of the method that the monofilament is compressed in the axial direction during or after the action of the mechanical forces. As a result, the longitudinally slotted areas or the webs delimiting the slits on Monofilament jacket bulged outwards.

The mechanical forces are preferably applied to most of the circumference of the monofilament or bristle to ensure that all boundary layers of the polymers are acted upon.

The monofilament is split or the bristles split preferably by impact forces. Instead, squeezing or torsional forces can also be brought into effect. These forces can be applied to the cut bristle or simultaneously to groups of bristles, e.g. on bristle bundles, before or after their attachment to the bristle carrier of the brush.

The bristles are preferably rounded at their ends on the use side. This can happen before and / or after splitting. In a further preferred embodiment of the method, the multiple ends resulting after the splitting are provided with a marking which visually indicates the usable length. This signals to the user that the wear properties change abruptly after the bristle has worn down to the mark, that is to say after the split ends have worn, since the substantially more rigid cross-section of the entire bristle then comes into effect. The split ends are also getting shorter and thus mechanically more aggressive. Such a display is particularly advisable when it comes to toothbrushes, body care brushes or the like. acts.

The invention is described below with reference to exemplary embodiments shown in the drawing. The drawing shows: Fig. 1 to Fig. 5 different cross sections of a

Monofilaments;

6 is a view of a bristle with a split end on the usage side,

7 is a view of a bristle or a

Interdental cleaner with slotted jacket;

Fig. 8 shows another variant of a

Monofilament cross section and

9 is a view of an interdental cleaner in a modified version.

The monofilament 1 according to FIG. 1 has a circular cross section and is produced by coextruding at least two polymers. It consists of a matrix 2 made of a polymer that determines the properties of the bristle and in geometric form — in this case in the form of a cross — embedded thin layers 3, which consist of another polymer or a mixture with the polymer of matrix 2. In the area of the thin layers 3 or the interfaces to the matrix 2, the secondary binding forces, that is to say the binding forces transverse to the longitudinal extent of the monofilament, are greatly reduced. In the embodiment shown, the thin ones run

Layers 3 on the outer surface 4 of the monofilament. However, they can also end with a small distance from them.

In particular, polymers for the matrix 2 include amides (PA) in question, while the thin layers 3 consist, for example, of a polymer mixture PA / PP or PA / PE.

In the exemplary embodiment according to FIG. 2, the thin layers 3 are embedded in the matrix 2 in the form of a three-armed star, while FIG. 3 shows a monofilament 1 with a polygonal, namely triangular cross section. In this embodiment, the embedded thin layers, which also extend outwards from the center, run out in the corners of the polygon. Instead, they can of course end up on the areas between the corners.

In the exemplary embodiment according to FIG. 4, the matrix 2 of the monofilament 1 is a further one of several possible polymers extruded in such a way that it is completely embedded in the matrix. For example, it can be thread-like structures 5 which, after the bristle has been produced and split or slotted, influence the bending behavior or the strength of the flags which are formed.

Fig. 5 shows a flat rectangular monofilament 1, in which the thin layers 3 are laid out in a grid, so that a plurality of essentially rectangular flags can be generated from the monofilament. 8 finally shows a monofilament cross-section, in which the matrix 2 consists of four identical outer parts with the cross-section of circular sectors and a central core, which are delimited by correspondingly extending thin layers 3.

In Fig. 6, a bristle 6 is shown schematically, which consists of a monofilament, for example according to FIG. 2, is produced by cutting to length and is split by the action of mechanical forces on its end on the usage side, so that individual flags 7 are formed, the shape of which corresponds to the shape of the regions of the monofilament forming the matrix 2. There are as many flags as the matrix 2 is broken down by thin layers 3. The length of use of the flags can be optically marked, for example, by the cross line shown in FIG. 6.

In the exemplary embodiment according to FIG. 7, the mechanical forces on the outer surface of a monofilament are brought into effect at regular intervals or in the case of a cut bristle at a distance from the end on the use side. Due to the thickness of the layers and the size of the force and / or the frequency / frequency of their application, it can be achieved that the jacket of the monofilament or the bristle 6 tears open only to a locally limited length and slots 8, 9 and 10 are formed. These slots are approximately in alignment, namely in the areas formed by the thin layers 3. In this version, the slots at the bristle end tear open to form flags. As the bristle wears down, the flags constantly replicate.

A monofilament according to FIG. 7 can also serve as an interdental cleaner ("floss") in any length, the slots being able to accommodate dentifrices, antiseptics or antibactericides. For an interdental cleaner, it is also advisable to compress the monofilament axially, as shown in FIG. 9, so that the webs 10 delimiting the slots from the matrix polymer bulge outwards.

The matrix 2 or the polymer forming it can in the individual cross-sectional parts delimited by the thin layers may be of different colors.

Claims

claims 1. Monofil with reduced secondary binding forces from at least two co-extruded polymers for the production of bristles or interdental cleaners which can be slit essentially in the axial direction by the action of mechanical forces, characterized in that the monofilament has the at least two co-extruded polymers in a geometrically regular arrangement with boundary layers running essentially in the axial direction, in which the reduced secondary binding forces prevail. 2. Monofilament according to .Anspruch 1, characterized in that the monofilament has a matrix of the polymer determining the physical and chemical properties of the bristle or the interdental cleaner, and that the second polymer in the form of thin layers is stored in the matrix. 3. Monofilament according to .Anspruch 2, characterized in that the polymer of the matrix is a copolymer or a polymer mixture. 4. Monofilament according to claim 2 or 3, characterized in that the polymer of the thin layers is a copolymer or a polymer mixture. 5. Monofilament according to .Anspruch 2, characterized in that the polymer of the thin layers reduces the secondary binding forces. 6. Monofilament according to claim 1 or 2, characterized in that the thin layers contain a proportion of the polymer of the matrix. 7. Monofilament according to .Anspruch 6, characterized in that the two polymers are present in approximately equal parts in the thin layers. 8. Monofilament according to one of claims 1 to 7, characterized in that the thin layers have a thickness of a few microns. 9. Monofilament according to one of claims 1 to 8, characterized in that the thin layers in the matrix extend to the circumference of the monofilament. 10. Monofilament according to one of claims 1 to 8, characterized in that the thin layers in the matrix end at a distance from the circumference of the monofilament. 11. Monofilament according to one of claims 1 to 10, characterized in that the matrix of the monofilament eJn has third polymer embedded in the matrix. 12. Monofilament according to one of claims 1 to 11, characterized in that the polymer of the matrix and that of the thin layers are of different colors. 13. Monofilament according to one of claims 1 to 12, characterized in that the monofilament has a cross-section deviating from the circular shape. 14. Monofilament according to claim 13, characterized in that the monofilament has a polygonal cross section. 15. Monofilament according to claim 14, characterized in that the thin layers run out to the corners of the polygonal cross-section. 16. Monofilament according to claim 14, characterized in that the thin layers run out to the surfaces of the polygonal cross section. 17. Monofilament according to one of claims 1 to 16, characterized in that the matrix consists of polyamide and the thin layers contain a polyolefin. 18. Process for the production of bristles from monofilaments according to one of claims 1 to 17, characterized in that the at least two polymers are co-extruded to form the monofilament, that the monofilament is stretched, optionally stabilized and is then cut to the desired length of the bristles and finally the bristles are split at their use end by the action of mechanical forces across the bristle axis to a limited length along the boundary layers. 19. A process for the production of bristles or interdental cleaners from monofilaments according to one of claims 1 to 17, characterized in that the at least two polymers are coextruded to form the monofilament, that the monofilament is stretched, optionally stabilized, and locally by the action of mechanical forces transverse to the monofilament axis of limited length is slit along the boundary layers. 20. The method according to .Anspruch 19, characterized in that the monofilament is compressed in the axial direction during or after the action of the mechanical forces. 21. The method according to any one of claims 18 to 20, characterized in that the mechanical forces are brought into effect at least on a substantial part of the circumference of the monofilament or the bristle. 22. The method according to any one of .Znsprüche 18 to 21, characterized in that the monofilament or the bristle is slit or split by impact forces. 23. The method according to any one of .Z ^ nsprüche 18 to 21, characterized in that the monofilament or the bristle slit or split by squeezing forces L will. 24. The method according to any one of claims 18 to 21, characterized in that the monofilament or the bristle is slit or split by torsional forces. 25. The method according to any one of claims 18 to 24, characterized in that the bristle is rounded at its end on the use side before splitting. 26. The method according to any one of claims 18 to 25, characterized in that the bristle is rounded after splitting at the end on the use side. 27. The method according to any one of claims 18 to 26, characterized in that the bristle is provided with a marking which visually indicates the usable length of the several bristle flags obtained after splitting. 28. Bristle goods, consisting of a bristle carrier and bristles attached thereto, characterized in that at least some of the bristles consist of a monofilament according to one of the claims 1 to 17 according to the Method according to one of .Claims 18 to 27 is produced. 29. Bristle goods according to claim 28, characterized in that the plurality of ends of the split bristles have a marking indicating their usable length. 30. Bristle goods in the form of an interdental cleaner, the is produced from a monofilament according to one of claims 1 to 17 according to the method according to claim 19 or 20, characterized in that the interdental cleaner is slotted on its circumference at uniform intervals. 31. Bristle goods according to .Ansp.ruch 30, characterized in that the interdental cleaner is bulged in the area of the slots by upsetting.