Plastic filament and process for its production

Abstract

A plastic filament has a core made of a first plastic material extending longitudinally along the filament and a sheath made of a second plastic material surrounding the core. The second plastic material of the sheath has a foam structure and a plurality of internal chambers, as well as a plurality of recesses on its outer surface. The plastic filament is produced by foaming the second plastic material of the sheath before and / or during extrusion, forming the foam structure with the internal chambers and the external recesses.

Description

The invention relates to a plastic filament having a core of a 1st plastic material extending in the longitudinal direction of the plastic filament and a sheath of a 2nd plastic material surrounding the core.A corresponding plastic filament is known and is cut to length into filament sections of predetermined length, wherein the filament sections are used, for example, as interdental cleaners or as floss or as bristles in cleaning brushes and, in particular, in tooth brushes, which will be assumed below by way of example.The bristle of a toothbrush must meet various requirements which are partially conflicting. On the one hand, the bristle must be soft in order to avoid injury to the user's gum, and on the other hand, the bristle must be sufficiently stable so that it can be restored to its initial position after use of the toothbrush, in which the bristles are bent. To meet these requirements, core-sheath filaments have been developed. The 1st plastic material of the core is selected so that the bristle made of the plastic filament has good bending rigidity and high raising ability. The core is preferably completely sheathed by a sheath, the 2ndplastic material of which, which is different from the 1stplastic material of the core, is adapted to the respective uses of the brush. It has been found that although a good cleaning effect is achieved with the bristle ends, the outer surface of the casing frequently has only a low cleaning effect.The object of the invention is to provide a plastic filament of the type mentioned, in which the sheath of the filament also has a good cleaning effect.Furthermore, a method is to be provided with which a corresponding plastic filament can be produced in a simple manner.This object is achieved in terms of device technology by a plastic filament having the features of claim 1.According to the invention, a preferably coextruded plastic filament is also provided with a core of a 1stplastic material extending in the longitudinal direction of the plastic filament and with a jacket of a 2ndplastic material preferably completely surrounding the core, wherein the 1stplastic material is different from the 2ndplastic material.The cross section of the plastic filament can be round, in particular circular, or polygonal and in particular rectangular. Preferably, the plastic filament is in the form of a thin ribbon having a square and in particular a rectangular cross-section.According to the invention, the basic consideration is taken to increase the cleaning effect of the jacket by structuring it. It is provided that the 2nd plastic material of the jacket consists of foam or has a foam structure and has a plurality of inner chambers and a plurality of depressions on its outer surface. Foaming of the 2nd plastic material of the jacket produces bubbles or cavities. The structure of the jacket can be a closed-pore structure or an open-pore structure. The bubbles arranged on the outer surface of the jacket burst or are preferably caused to burst by mechanical action and depressions, depressions or dimples are formed on the outer surface of the jacket. The inner chambers are formed in the interior of the sheath, the size and / or number of which can be used to adjust the elasticity of the sheath during the production of the plastic filament.A plastic filament having the above-mentioned configuration has edges on the outer surface of the sheath, which edges serve as scraping or cleaning edges when using bristles made of the plastic filament in a toothbrush, thereby enhancing the cleaning effect. The outer depressions can pick up the coating, for example plaque, removed from the surface to be cleaned and transport this coating away well.Plastic materials from the group PA6.12, PA11, PA10.10, PA6.10 and PBT (polybutylene terephthalate) or a blend of these materials, preferably a polyamide (PA) and in particular polyamide 6.12 (PA6.12), are used as the 1st plastic material of the core. It can be provided here that the 1st plastic material of the core comprises at least 90 mas % and in particular at least 95 mas % of PA 6.12 or even completely consists of PA 6.12. The 2nd plastic material of the jacket should be a soft, highly elastic material. Preferably, it is provided that the 2nd plastic material of the jacket comprises at least 90 mas % and in particular at least 95 mas % of an elastomer and in particular a thermoplastic elastomer or an elastomer blend or even completely consists of a thermoplastic elastomer or an elastomer blend.It has been found that it is advantageous if a radial cover of the sheath is at least 5% of a maximum diameter of the plastic filament. Usually, plastic filament has a circular cross section. Due to the foam structure of the sheath and the structuring on the outer surface of the sheath, the cross-sectional shape of the plastic filament deviates from an ideal circle. There are thus different diameters, wherein there is at least one maximum diameter in each cross section.The sheath should not be too thin to maintain sufficient radial elasticity, but the sheath should not be too thick to allow a bristle made from the plastic filament to still have sufficient stability and recovery. In a preferred embodiment of the invention, it is provided that the radial thickness of the sheath is in the range from 5% to 70%, preferably in the range from 20% to 50%, and in particular in the range from 20% to 30%, of the maximum diameter of the plastic filament.In a preferred embodiment of the invention, it is provided that the maximum diameter of the plastic filament is in the range from 0.05 mm to 0.5 mm, preferably in the range from 0.1 mm to 0.3 mm and particularly preferably in the range from 0.15 mm to 0.25 mm.A method for producing a corresponding plastic filament for achieving the above-mentioned object is characterized in that the 2nd plastic material of the sheath is foamed before and / or during the extrusion in such a way that a plurality of inner chambers are formed in the interior of the sheath and a plurality of depressions are formed on the outer surface of the sheath.The 1st plastic material for forming the core and the 2nd plastic material for forming the jacket surrounding the core are co-extruded. Preferably, immediately before and / or during the extrusion, i.e. the emergence of the plastic composition from an extruder, the 2nd plastic material of the jacket is foamed to form a foam structure. The foam structure can be open-pore or a closed-pore foam. By foaming, inner chambers are formed in the interior of the jacket. Bubbles are formed on the outer surface of the jacket, which bubbles are either burst open or opened by themselves. As a result of the bursting or opening of the bubbles, depressions or depressions are formed on the outer surface of the jacket.The bubbles formed on the outer surface of the plastic filament as a result of foaming can be opened by applying external force in a subsequent process step. The opening of the bladders can be opened by stretching the plastic filament and / or by applying an external force in a mechanical, pneumatic or hydraulic manner.Another way of opening the bubbles on the outer surface of the plastic filament is to pass the plastic filament through a heating path. The elevated temperature leads to an increased gas pressure in the interior of the bubbles and to their burst.It is preferably provided that the plastic filament is stretched after the extrusion, i.e. that a tensile force is applied to the plastic filament, which results in an elongation of the plastic filament with a simultaneous diameter reduction. As a result of the stretching of the plastic filament, even more bubbles form on the outer surface and the depressions or depressions formed on the outside receive an extension in the longitudinal direction of the plastic filament, as a result of which their volume is increased and they are even more suitable for receiving coatings which are scraped off a surface to be cleaned, for example the tooth surface.A corresponding plastic filament can be used as bristle of a toothbrush or as interdental cleaner or as dental floss. In particular, a plastic filament produced by the aforementioned method can be used as bristle of a toothbrush or as interdental cleaner or as floss.In the following, the configuration of a plastic filament as a dental floss will be discussed by way of example.Floss should have high strength and be hardly stretchable.The plastic material of the dental floss in a one-component configuration (1K filament) can be based on a polymer of the following group:polyesterspolyolefinspolyamidespolyurethanes or on a block polymer from the following group:modified polyestersmodified polyamidesmodified polyurethanesthermoplastic polyolefins (TPO)thermoplastic vulcanisates (TPV)It is likewise conceivable to mix / blend the aforementioned components and / or vulcanisates of these components.In the case of a two-component configuration of the dental floss (2K filament) having a core and a sheath, the core material is preferably selected from the aforementioned components.The jacket material can likewise be selected from the aforementioned components.Any combinations of the aforementioned components are conceivable.Preferably, the 1K filament is made of a matrix material based on a biologically based polyamide such as PA11 or PA10.10.The floss may be in the form of a ribbon. The thickness of the ribbon is preferably between 0.03 mm and 0.20 mm. In particular, between 0.06 mm and 0.15 mm.The width of the ribbon is preferably between 0.5 mm and 4 mm and in particular between 0.9 mm and 2.5 mm.The ribbon can be designed in the form of a rectangle with 90° angles on the sides or with different curvatures. However, with a rectangular profile there is the risk of injuries due to sharp corners. In any case, a rounding with a corresponding radius should be provided here. However, other profiles are also possible.Usually, flosses are smooth on the surface. To increase the cleaning effect of floss, a non-smooth surface may be used. According to the invention, this can be done in 3 possible ways:1. The floss may have "dimples" on the surfaces which may be achieved by foaming the plastic material. Foaming produces bubbles which burst on the surface and cause "denting". The stretching conveys even more bubbles to the surfaces. In the case of a 1K filament, the complete cross section is foamed, and in the case of a 2K filament, only the material in the sheath is foamed.2. Grooves can generally be introduced mechanically into the surfaces. The grooves may have different shapes. The depth of the grooves may vary between 5% and 35% of the thickness of the floss, preferably between 10% and 20%. The number of grooves per side may be between 1 and 6 grooves.3. Both possibilities can also be combined. The floss may contain "denting" and grooves.Further details and features of the invention can be seen from the following description of an exemplary embodiment with reference to the drawing. The following are shown: FIG. 1 shows a section of a plastic filament according to the invention, and FIG. 2 is a sectional view taken along line II--II of FIG. 1.A plastic filament 10 illustrated in FIGS. 1 and 2 has a core 11 of a 1st plastic material extending in the longitudinal direction of the plastic filament 10 and a sheath 12 of a 2nd plastic material completely surrounding the core 11. The 2nd plastic material of the jacket 12 has a foam structure with a plurality of internal chambers 14 and a plurality of depressions 15 formed on the outer surface 13 of the jacket 12.A radial ceiling d M of the sheath 12 is between 5% and 70% of the maximum diameter D of the plastic filament 10, wherein the maximum diameter D of the plastic filament 10 is preferably in a range from 0.1 mm to 0.3 mm.The plastic filament 10 is produced by co-extrusion of the core 11 and the sheath 12, wherein the 2nd plastic material of the sheath 12 is foamed before and / or during the extrusion in such a way that the inner chambers 14 are formed in the interior of the sheath 12 and the depressions 15 are formed on the outer surface thereof.

Claims

A plastic filament (10) having a core (11) of a 1st plastic material extending in the longitudinal direction of the plastic filament (10) and having a sheath (12) of a 2nd plastic material surrounding the core (11), characterized in that the 2nd plastic material of the sheath (12) has a foam structure and has a plurality of inner chambers (14) and a plurality of depressions (15) on its outer surface (13).The plastic filament according to claim 1, characterized in that the 1st plastic material of the core (11) consists of at least 90 mas% of PA6.12, PA11, PA10.10, PA6.10 and PBT (polybutylene terephthalate) or a blend of these materials.The plastic filament according to claim 1 or 2, characterized in that the 2nd plastic material of the sheath (12) comprises at least 90 mas % of an elastomer or an elastomer blend or consists entirely of an elastomer or an elastomer blend.The plastic filament according to any one of claims 1 to 3, characterized in that a radial thickness (d M) of the sheath (12) is at least 5% of a maximum diameter (D) of the plastic filament (10).The plastic filament according to claim 4, characterized in that the radial thickness (d M) of the sheath (12) is 5% to 70%, and in particular 20% to 30%, of the maximum diameter (D) of the plastic filament (10).The plastic filament according to any one of claims 1 to 5, characterized in that the maximum diameter (D) of the plastic filament (10) is in the range of 0.1 mm to 0.3 mm.Method for producing a plastic filament according to one of Claims 1 to 6, wherein the 1st plastic material for forming the core (11) and the 2nd plastic material for forming the sheath (12) are co-extruded, characterized in that the 2nd plastic material of the sheath (12) is foamed before and / or during the extrusion in such a way that a plurality of inner chambers (14) are formed in the interior of the sheath (12) and a plurality of depressions (15) are formed on the outer surface (13) of the sheath (12).Method according to claim 7, characterised in that bubbles formed on the outer surface of the plastic filament (10) as a result of foaming are opened in a subsequent method section by applying external force.Method according to claim 8, characterised in that the opening of the bladders is effected by stretching the plastic filament (10) and / or by applying an external force and / or by rubbing over a friction surface and / or by passing through a heating path.Use of a plastic filament (10) according to one of claims 1 to 6 as bristle of a toothbrush or as interdental cleaner or as floss.Use of a plastic filament (10) produced by a method according to one of Claims 7 to 9, as bristle of a toothbrush or as interdental cleaner or as floss

Images