Plastic filament and method for producing same

Abstract

A plastic filament has a core which extends in the longitudinal direction of the plastic filament and consists of a first plastic material, and a sheath, surrounding the core, made of a second plastic material. The second plastic material of the sheath has a foam structure and a multiplicity of inner chambers and, on its outer surface, a multiplicity of depressions which have a length running in the longitudinal direction of the plastic filament and a width running perpendicularly thereto in the circumferential direction of the plastic filament. The width of at least one of the depressions is in the range of 1% to 10% of a maximum filament diameter and, in particular, in the range of 3% to 6% of the maximum filament diameter.

Description

[0001] Plastic filament and process for its production

[0002] The invention relates to a plastic filament with a core made of a 1. plastic material extending in the longitudinal direction of the plastic filament and with a sheath made of a 2. plastic material surrounding the core, wherein the 2. plastic material of the sheath has a foam structure and a plurality of inner chambers and a plurality of depressions on its outer surface, wherein the depressions each have a length running in the longitudinal direction of the plastic filament and a width running perpendicular thereto in the circumferential direction of the plastic filament.

[0003] Plastic filaments composed of several different plastic materials have been known for a long time. According to the invention, a plastic filament is preferably provided that consists of exactly two plastic materials, namely the first plastic material of the core and the second plastic material of the sheath.

[0004] A corresponding plastic filament is extruded and then cut to filament sections of predetermined length, whereby the filament sections are used, for example, as intermetallic cleaners or as dental floss or as bristles in cleaning brushes and in particular in toothbrushes, the following being used as an example.

[0005] The bristles of a toothbrush must meet various, sometimes contradictory, requirements. On the one hand, the bristles must be soft to avoid injuring the user's gums; on the other hand, the bristles must be sufficiently stable so that they return to their original position after use of the toothbrush, which involves bending the bristles. Core-shell filaments have been developed to meet these requirements. The first plastic material of the core is selected so that the bristle made from the plastic filament has good flexural rigidity and a high level of uprightness. The core is preferably completely covered by a shell, the second plastic material of which is different from the first plastic material of the core and is adapted to the specific use of the brush.It has been shown that although the bristle ends achieve a good cleaning effect, the outer surface of the casing often has only a low cleaning effect and, in particular, only contributes to a small extent to the removal of dissolved dirt or deposit particles.

[0006] In order to obtain a soft sheath in a core-sheath filament, it is known that the second plastic material of the sheath is foamed or formed with a foam structure. During the extrusion and foaming of the second plastic material, some foam bubbles burst on the outer surface of the filament, so that the filament has a multitude of very small depressions on its outer surface. The radial structure thus formed on the outer surface of the plastic filament improves the cleaning effect of the plastic filament in theory, but in practice this effect is very slight. The object of the invention is to create a plastic filament of the type mentioned in which the sheath of the plastic filament also has an improved cleaning effect.

[0007] In addition, a process is to be created with which a corresponding plastic filament can be produced in a simple manner.

[0008] This object is achieved in terms of device technology by a plastic filament having the features of claim 1.

[0009] Also provided according to the invention is a preferably co-extruded plastic filament with a core made of a first plastic material extending in the longitudinal direction of the plastic filament and a sheath made of a second plastic material, preferably completely surrounding the core, wherein the first plastic material is different from the second plastic material. The second plastic material of the sheath has a foam structure and a plurality of internal chambers and a plurality of depressions on its outer surface. The depressions each have a length running in the longitudinal direction of the plastic filament and a width running perpendicular thereto in the circumferential direction of the plastic filament.By a suitable choice of the foaming parameters and / or by a post-treatment and / or by a suitable choice of material, the invention provides that the width of at least one of the depressions is in the range from 1% to 10% of a maximum filament diameter (0.01 x D dbd Q, 1 x D) and in particular in the range from 3% to 6% of the maximum filament diameter (0.03 x D < b < 0.06 x D). In this way, relatively large depressions are formed on the outer surface of the filament which, on the one hand, can take up and retain a sufficiently large quantity of particles to be removed, and on the other hand, the edges of the relatively large depressions form cleaning and scraping edges which increase the cleaning effect. In addition, the depressions on the outside can serve as a reservoir for cleaning agents, for example toothpaste, and so reduce the residence time of the cleaning agent on the tooth orin the mouth, thereby extending the exposure time and increasing the cleaning performance.

[0010] The cross-section of the plastic filament can be round, in particular circular, or polygonal, in particular rectangular. Alternatively, the plastic filament has the shape of a thin ribbon with a square, in particular rectangular, cross-section.

[0011] The invention is based on the basic idea of ​​increasing the cleaning effect of the jacket by structuring it. The second plastic material of the jacket is made of foam or has a foam structure and has a large number of internal chambers and a large number of depressions on its outer surface. The foaming of the second plastic material of the jacket creates 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 influences, and depressions, troughs or dents are created on the outer surface of the jacket. The inner chambers are formed inside the jacket; the size and / or number of these chambers can be used to adjust the elasticity of the jacket during production of the plastic filament.

[0012] A plastic filament with the aforementioned configuration has edges on the outer surface of the casing which, when bristles made from the plastic filament are used on a toothbrush, serve as cleaning edges and thereby increase the cleaning effect. The outer recesses can absorb the deposit, e.g. plaque, removed from the surface to be cleaned and transport this deposit away. Preferably, the length of the recess in the longitudinal direction of the plastic filament is at least twice the width of the recess in the circumferential direction of the plastic filament running perpendicular thereto, and in particular that the length of the recess is at least 1.1 times to 10 times and in particular 5 times to 10 times the width of the recess.

[0013] It can be provided that the length of the recess is in the range of 0.05 mm to 1.5 mm and in particular in the range of 0.5 mm to 1.0 mm.

[0014] It has been found that it is advantageous if the radial thickness of the sheath is at least 5% of the maximum diameter of the plastic filament. Typically, 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. Thus, there are different diameters, with at least one maximum diameter in each cross-section.

[0015] The sheath should not be too thin to maintain sufficient radial elasticity, but on the other hand, the sheath should not be too thick so that a bristle made from the plastic filament still has sufficient stability and sufficient recovery capacity. In a preferred embodiment of the invention, the radial thickness of the sheath is in the range of 5% to 70%, preferably in the range of 20% to 50%, and in particular in the range of 20% to 30% of the maximum diameter of the plastic filament.

[0016] 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 1.0 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.

[0017] Preferably, a radial depth of the recess is in the range from 5% to 100% of the radial thickness of the shell, i.e. the recess can be formed completely through the shell to the core. Preferably, the radial depth of the recess is in the range from 10% to 30% of the radial thickness of the shell. So far, it has been defined that at least one recess of the aforementioned configuration is formed on the outer surface of the shell. However, it is preferably provided that a plurality of corresponding recesses and in particular a multiplicity of corresponding recesses are formed on the outer surface of the shell. Preferably, it is provided that 10% to 95% of the outer surface of the shell and in particular 20% to 40% of the outer surface of the shell is provided with corresponding recesses.

[0018] The cross-sectional area of ​​the plastic filament is composed of the cross-sectional area of ​​the core and the cross-sectional area of ​​the surrounding sheath. In a further development of the invention, the cross-sectional area of ​​the sheath can be 5% to 80%, preferably 10% to 70%, and particularly preferably 15% to 40% of the total cross-sectional area of ​​the plastic filament.

[0019] Plastic materials from the group PA6.12, PA11, PA10.10, PA6.10 and PBT (polybutylene terephthalate) or a blend of these materials, preferably polyester or PBT, are used as the first plastic material of the core. It can be provided that the first plastic material of the core comprises at least 90 mass% and in particular at least 95 mass% PA 6.12 or even consists entirely of PA 6.12. The second plastic material of the sheath should be a soft, highly elastic material. It is preferably provided that the second plastic material of the sheath comprises at least 80 mass% and in particular at least 95 mass% an elastomer and in particular a thermoplastic elastomer or an elastomer blend or even consists entirely of a thermoplastic elastomer or an elastomer blend. A method for producing a corresponding plastic filament to solve the above-mentioned problem is characterized in that the 2ndThe plastic material of the jacket is foamed before or during extrusion so that a large number of internal chambers are formed inside the jacket and a large number of depressions are formed on the outside of the jacket.

[0020] The dimensions of at least one of the depressions and preferably of a plurality of depressions are enlarged in at least one subsequent method step to such an extent that the width of the depression is in the range from 1% to 10% of the maximum filament diameter (0.01 x DK < bd 0.10 x D) and in particular in the range from 3% to 6% of the maximum filament diameter (0.03 x D < bd 0.06 x D). The first plastic material for forming the core and the second plastic material for forming the shell surrounding the core are co-extruded. Preferably immediately before and / or during extrusion, i.e. the exit of the plastic mass from the extruder, the second plastic material of the shell is foamed to form a foam structure. The foam structure can be open-pore or closed-pore foam. The foaming creates internal chambers inside the shell.Bubbles form on the outer surface of the casing and either burst open of their own accord or are opened. As the bubbles burst or open, depressions or indentations form on the outer surface of the casing. The indentations formed on the outer surface of the plastic filament as a result of the bursting and / or opening are enlarged in a subsequent process step, preferably by connecting several adjacent indentations to one another to form a larger new indentation. For this purpose, it can be provided, for example, that the bubbles formed on the outer surface of the plastic filament as a result of foaming are opened and connected in at least one subsequent process step by applying external force.The opening of the bubbles and the enlargement and interconnection of the depressions can be achieved by stretching the plastic filament and / or by applying an external force in a mechanical, pneumatic, or hydraulic manner. Alternatively or additionally, the plastic filament can be guided or rubbed over a friction surface, thereby opening the bubbles.

[0021] Another way to open the bubbles and connect the depressions on the outer surface of the plastic filament is to pass the plastic filament through a heating section. The increased temperature leads to increased gas pressure inside the bubbles, causing them to burst.

[0022] Preferably, the plastic filament is stretched after extrusion, i.e., a tensile force is applied to the plastic filament, resulting in an elongation of the plastic filament while simultaneously reducing its diameter. Stretching the plastic filament causes even more bubbles to form on the outer surface, and the depressions or troughs formed on the outside are extended in the longitudinal direction of the plastic filament, increasing their volume and making them even better suited to absorbing deposits that are scraped off a surface to be cleaned, such as the tooth surface.

[0023] Preferably, the stretching of the plastic filament in the subsequent process step is carried out in such a way that the length of the plastic filament increases by at least 10%, i.e. to 110% of its original length.

[0024] A corresponding plastic filament can be used as a toothbrush bristle, as an interdental cleaner, or as dental floss. In particular, a plastic filament produced by the aforementioned method can be used as a toothbrush bristle, as an interdental cleaner, or as dental floss.

[0025] The following is an example of how a plastic filament can be used as dental floss.

[0026] Dental floss should be very strong and hardly stretchable.

[0027] The plastic material of the dental floss in single-component design (IK filament) can be based on a polymer from the following group:

[0028] - Polyesters - Polyolefins

[0029] - Polyamides

[0030] - polyurethanes or on a block polymer from the following group:

[0031] - modified polyesters

[0032] - modified polyamides

[0033] - modified polyurethanes

[0034] - thermoplastic polyolefins (TPO)

[0035] - thermoplastic vulcanizates (TPV)

[0036] It is also conceivable to mix / blend the above-mentioned components and / or vulcanizates made from these components.

[0037] In the case of a two-component design of the dental floss (2K filament) with a core and a sheath, the core material is preferably selected from the aforementioned components.

[0038] The sheath material can also be selected from the aforementioned components.

[0039] Any combination of the above-mentioned components is conceivable.

[0040] Preferably, the IK filament is made from a matrix material based on a biologically based polyamide such as PA11 or PA10.10.

[0041] The dental 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.

[0042] The strip can be rectangular with 90° angles on the sides or with various curves. However, a rectangular profile poses a risk of injury due to sharp corners. In these cases, a rounding with an appropriate radius should always be provided. However, other profiles are also possible.

[0043] Typically, dental flosses have a smooth surface. To increase the cleaning effect of dental floss, a non-smooth surface can be used. According to the invention, this can be achieved in three possible ways:

[0044] 1. The dental floss may have "dents" on its surface, which can be caused by foaming the plastic material. Foaming creates bubbles that burst on the surface, creating "dents." Stretching causes even more bubbles to appear on the surfaces. With an IK filament, the entire cross-section is foamed; with a 2K filament, only the material in the sheath is foamed.

[0045] 2. Grooves can usually be mechanically created in the surfaces. The grooves can have different shapes. The depth of the grooves can vary between 5% and 35% of the thickness of the dental floss, preferably between 10% and 20%. The number of grooves per side can be between 1 and 6.

[0046] 3. Both options can also be combined. The floss may contain "dents" and grooves.

[0047] Further details and features of the invention will become apparent from the following description of an embodiment with reference to the drawings. They show:

[0048] Fig. 1 A section of a plastic filament according to the invention,

[0049] Fig. 2 shows section II-II in Fig. 1 and

[0050] Fig. 3 shows an enlarged view of a depression on the outer surface of the plastic filament.

[0051] A plastic filament 10 shown in Figs. 1 and 2 has a core 11 made of a first plastic material extending in the longitudinal direction LR of the plastic filament 10 and a sheath 12 made of a second plastic material completely surrounding the core 11. The second plastic material of the sheath 12 has a foam structure with a plurality of internal chambers 14 and a plurality of recesses 15 formed on the outer surface 13 of the sheath 12.

[0052] A radial thickness dn 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 second plastic material of the sheath 12 is foamed before and / or during extrusion such that the inner chambers 14 are formed inside the sheath 12 and the depressions 15 are formed on its outer surface.

[0053] Fig. 3 shows a depression 15 on the outer surface of the plastic filament 10. The depression 15 is formed by bringing together a plurality of bubbles and / or depressions which form when the second plastic material of the casing 12 is foamed. The depression 15 is so large that a length 1 running in the longitudinal direction LR of the plastic filament 10 is significantly greater than a width B running perpendicular thereto in the circumferential direction of the plastic filament 10. Preferably, the length 1 of the depression 15 is at least twice as large as the width b of the depression 15. The length 1 of the depression 15 can be 5 times to 10 times the width b of the depression 15.

Claims

Patent claims 1. Plastic filament (10) with a core (11) extending in the longitudinal direction (LR) of the plastic filament (10) made of a 1. plastic material and with a sheath (12) surrounding the core (11) made of a 2. plastic material, wherein the 2. plastic material of the sheath (12) has a foam structure and a plurality of inner chambers (14) and on its outer surface (13) a plurality of depressions (15), wherein the depressions (15) each have a length (1) running in the longitudinal direction of the plastic filament (10) and a width (b) running perpendicular thereto in the circumferential direction of the plastic filament (10), characterized in that the width (b) of at least one of the depressions (15) is in the range from 1% to 10% of a maximum filament diameter (D) (0.01 x D < bd Q,l x D) and in particular in the range from 3% to 6% of the maximum filament diameter (D) (0.03 x D < bd 0.06 x D).

2. Plastic filament according to claim 1, characterized in that the length (1) of the depression (15) is at least 1.1 times the width (b) of the depression (15) (1 > 1.1 x b).

3. Plastic filament according to claim 2, characterized in that the length (1) of the recess (15) is at least 2 times to 5 times the width (b) of the recess (15) (2 xbdl < 5 xb).

4. Plastic filament according to one of claims 1 to d, characterized in that the length (1) of the recess is in the range from 0.05 mm to 1.5 mm and in particular in the range from 0.5 mm to 1.0 mm.

5. Plastic filament according to one of claims 1 to 4, characterized in that a radial thickness (dn) of the sheath (12) is at least 5% of a maximum diameter (D) of the plastic filament (10).

6. Plastic filament according to claim 5, characterized in that the radial thickness (dn) of the sheath (12) is 5% to 70% and in particular 20% to 30% of the maximum diameter (D) of the plastic filament (10).

7. Plastic filament according to one of claims 1 to 6, characterized in that the maximum diameter (D) of the plastic filament (10) is in the range from 0.05 mm to 1.0 mm and in particular in the range from 0.1 mm to 0.3 mm.

8. Plastic filament according to one of claims 5 to 7, characterized in that a radial depth of the recess (15) is in the range of 5% to 100% of the radial thickness (dn) of the sheath (12).

9. Plastic filament according to claim 8, characterized in that the radial depth of the recess (15) is in the range of 10% to 30% of the radial thickness (dn) of the sheath (12).

10. Plastic filament according to one of claims 1 to 9, characterized in that 10% to 95% of the outer surface of the sheath (12) is provided with depressions (15).

11. Plastic filament according to claim 10, characterized in that 20% to 40% of the outer surface of the sheath (12) is provided with depressions (15).

12. Plastic filament according to one of claims 1 to 11, characterized in that the cross-sectional area of the sheath (12) is 5% to 80%, preferably 10% to 70% and particularly preferably 15% to 40% of the total cross-sectional area of the plastic filament (10).

13. Plastic filament according to one of claims 1 to 12, characterized in that the first plastic material of the core (11) consists of at least 90 mass% PA6.12, PA11, PA10.10, PA6.10 and PBT (polybutylene terephthalate) or a blend of these materials.

14. Plastic filament according to one of claims 1 to 13, characterized in that the second plastic material of the sheath (12) comprises at least 80 mass% of an elastomer or an elastomer blend or consists entirely of an elastomer or an elastomer blend.

15. A method for producing a plastic filament according to any one of claims 1 to 14, wherein the first plastic material for forming the core (11) and the second plastic material for forming the sheath (12) are co-extruded, wherein the second plastic material of the casing (12) is foamed before and / or during extrusion in such a way that a plurality of inner chambers (14) are formed inside the casing (12) and a plurality of depressions (15) are formed on the outer surface (13) of the casing (12), wherein the dimensions of at least one of the depressions (15) are enlarged in at least one subsequent process step to such an extent that the width (b) of the depression (15) is in the range from 1% to 10% of the maximum filament diameter (D) (0.01 x D < bd 0.10 x D) and in particular in the range from 3% to 6% of the maximum filament diameter (D) (0.03 x D < bd 0.06 x D).

16. The method according to claim 15, characterized in that a plurality of adjacently arranged depressions are connected to one another by the at least one subsequent method step to form a larger new depression.

17. The method according to claim 15 or 16, characterized in that bubbles formed on the outer surface of the plastic filament (10) as a result of the foaming are opened in the at least one subsequent method step by applying external force.

18. Method according to one of claims 15 to 17, characterized in that the subsequent method step comprises stretching the plastic filament (10) and / or applying an external force to the outer surface of the plastic filament (10) and / or rubbing the plastic filament over a friction surface and / or passing the plastic fabric filament through a heating section.

19. Method according to one of claims 15 to 17, characterized in that the plastic filament (10) is stretched in its length by at least 10% in the subsequent method step.

20. Use of a plastic filament (10) according to one of claims 1 to 14 as a bristle of a toothbrush or as an interdental cleaner or as dental floss.

21. Use of a plastic filament (10), produced by a process according to one of claims 15 to 19, as a bristle of a toothbrush or as an interdental cleaner or as dental floss.

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