Plastic filament and method of manufacturing the same

Abstract

The plastic filament extends in the longitudinal direction of the plastic filament and has a core made of a first plastic material and an outer shell made of a second plastic material surrounding the core. The second plastic material of the outer shell has a foam structure and a plurality of internal chambers, and has a plurality of indentations on its outer surface. The indentations have a length extending in the longitudinal direction of the plastic filament and a filament circumferential width extending perpendicularly in the circumferential direction of the plastic filament. The width of at least one indentation is within the range of 1% to 10% of the maximum filament diameter, and in particular is within the range of 3% to 6% of the maximum filament diameter.

Description

Technology Field

[0001] The present invention relates to a plastic filament having a core extending in the longitudinal direction of the plastic filament and an outer shell surrounding the core, wherein the plastic material of the outer shell has a foam structure and a plurality of internal chambers, and a plurality of concave portions are formed on the outer surface, and each concave portion has a length in the longitudinal direction of the filament and a filament circumferential width extending perpendicularly to the length in the longitudinal direction of the plastic filament. Background Technology

[0002] Plastic filaments composed of various different plastic materials have long been known. According to the present invention, a plastic filament is provided that preferably consists of exactly two plastic materials, namely a first plastic material of the core and a second plastic material of the outer shell.

[0003] After extruding the plastic filament, it is cut into filament portions of a predetermined length, and these filament portions are used, for example, as interdental cleaners or dental floss, or as cleaning brushes, particularly as bristles of a toothbrush, and are exemplified below.

[0004] Toothbrush bristles must satisfy several conflicting requirements. On the one hand, the bristles must be soft to prevent damage to the user's gums, while on the other hand, they must possess sufficient rigidity to allow the bristles, bent during use, to return to their original position after use. Core-shell filaments have been developed to meet these requirements.

[0005] The first plastic material forming the core is selected so that the bristles, manufactured from plastic filaments, possess excellent bending stiffness and high resilience. The core is preferably completely surrounded by an outer sheath, and the second plastic material of the sheath is different from the first plastic material of the core and is tailored to the specific application of the brush. While the bristles must provide an excellent level of cleaning effect, the outer surface of the sheath often has a limited cleaning effect, contributing somewhat to the removal and transport of detached contaminants or captured particles.

[0006] It is known that in order to obtain a soft outer shell from a core-shell filament, a second plastic material of the outer shell is foamed or formed into a foamed foam structure. When the second plastic material is extruded and foamed, some foam bubbles burst on the outer surface of the filament, and as a result, the filament acquires a number of very small indentations on its outer surface. The radial structure on the outer surface of the plastic filament formed by this process theoretically improves the cleaning effect of the plastic filament, but in practice, the effect is very minimal. The problem to be solved

[0007] The objective of the present invention is to provide a plastic filament of the aforementioned type, wherein the outer layer of the plastic filament also has an enhanced cleaning effect. means of solving the problem

[0008] According to the present invention, a co-extruded plastic filament is provided, preferably having 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 that preferably completely surrounds the core. 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 has a plurality of indentations on its outer surface. Each indentation has a length in the longitudinal direction of the filament and a width extending perpendicularly in the circumferential direction of the plastic filament. By appropriate selection of foaming parameters and / or post-processing and / or appropriate material selection, according to the present invention, the width of at least one indentation is in the range of 1% to 10% of the maximum filament diameter (0.01xD <b≤0.1xD) 내, 특히 최대 필라멘트 직경의 3% 내지 6% 범위(0.03xD≤b≤0.06xD) 내에 있도록 된다. Effects of the invention

[0009] As a result, a relatively large concave area is formed on the outer surface of the filament, which, on the one hand, can accommodate and retain a sufficient amount of particles to be removed, and on the other hand, the edge of the relatively large concave area forms a cleaning and scraping edge that enhances the cleaning effect. Furthermore, the concave area on the outer surface functions as a reservoir for a cleaning agent, such as toothpaste, thereby increasing the retention time of the cleaning agent on the teeth or in the oral cavity, which extends the exposure time and improves cleaning performance. Brief explanation of the drawing

[0010] FIG. 1 is a partial perspective view of a plastic filament according to the present invention. FIG. 2 is a cross-sectional view along line II-II of FIG. 1, FIG. 3 is an enlarged view of a concave portion formed on the outer surface of a plastic filament of the present invention. Specific details for implementing the invention

[0011] Further details and features of the present invention can be understood from the description of embodiments with reference to the drawings below.

[0012] The cross-section of the plastic filament can be circular, particularly circular, or polygonal, particularly rectangular. Alternatively, the plastic filament can be in the form of a thin strip having a quadrilateral, particularly rectangular cross-section.

[0013] According to the present invention, it is based on the basic concept of enhancing the cleaning effect of the outer shell through the structuring of the outer shell. At this time, the second plastic material of the outer shell is formed by foaming or has a foam structure, and is intended to have a plurality of internal chambers and a plurality of concave parts on its outer surface. Bubbles or cavities are formed by the foaming of the plastic material of the outer shell. The structure of the outer shell may be a closed pore structure or an open pore structure. Bubbles placed on the outer surface of the outer shell are primarily ruptured by mechanical action, or are caused to rupture, thereby forming concave parts, hollow parts, or scratches on the outer surface of the outer shell. Internal chambers are formed inside the outer shell, and by adjusting their size and / or number, the elasticity of the outer shell can be controlled during the manufacture of plastic filaments.

[0014] A plastic filament having the above structure has a concave portion on the outer surface of the outer shell, and when a toothbrush bristles made from the plastic filament are used in a toothbrush, this concave portion functions as a cleaning edge to enhance the cleaning effect. The outer concave portion can receive and transport and remove deposits, such as plaque, removed from the surface to be cleaned. Preferably, the length of the concave portion in the longitudinal direction of the plastic filament is at least twice the width of the concave portion in the circumferential direction of the plastic filament that extends perpendicularly thereto, and in particular, the length of the concave portion is at least 1.1 to 10 times, and particularly 5 to 10 times, the width of the concave portion.

[0015] Accordingly, the length of the concave portion can be configured within the range of 0.05 mm to 1.5 mm, particularly within the range of 0.5 mm to 1.0 mm.

[0016] It was found that it is advantageous when the radial thickness of the outer layer is at least 5% of the maximum diameter of the plastic filament. Typically, plastic filaments have a circular cross-section.

[0017] However, due to the foam structure of the outer shell and the structuring formed on the outer surface of the shell, the cross-sectional shape of the plastic filament deviates from an ideal circle. Consequently, different diameters exist, and each cross-section has at least one maximum diameter.

[0018] The sheath should not be too thin to maintain sufficient radial elasticity, and at the same time should not be too thick so that the brush made from the plastic filament has sufficient stability and resilience. In a preferred embodiment, the radial sheath thickness is within the range of 5% to 70% of the maximum diameter of the plastic filament, preferably within the range of 20% to 50%, and particularly within the range of 20% to 30%.

[0019] In a preferred embodiment, the maximum diameter of the plastic filament is in the range of 0.05 mm to 1.0 mm, preferably in the range of 0.1 mm to 0.3 mm, and particularly preferably in the range of 0.15 mm to 0.25 mm.

[0020] Preferably, the radial depth of the concave portion is within the range of 5% to 100% of the radial thickness of the outer shell, that is, the concave portion can completely penetrate the outer shell and reach the core. Preferably, the radial depth of the concave portion is within the range of 10% to 30% of the radial thickness of the outer shell.

[0021] Up until now, it has been defined that at least one concave portion of the above structure is formed on the outer surface of the outer shell. However, preferably, a plurality of concave portions, particularly a plurality of concave portions, are formed on the outer surface of the outer shell. Preferably, the corresponding concave portions are formed on 10% to 95% of the outer surface of the outer shell, particularly on 20% to 40% of the outer surface of the outer shell.

[0022] The cross-sectional area of ​​the plastic filament consists of the cross-sectional area of ​​the core and the outer shell surrounding it. In a further embodiment of the present invention, the cross-sectional area of ​​the outer shell may be configured to be 5% to 80%, preferably 10% to 70%, and particularly preferably 15% to 40% of the total cross-sectional area of ​​the plastic filament.

[0023] As the first plastic material of the core, a plastic material comprising PA6.12, PA11, PA10.10, PA6.10, and PBT, or a blend of these materials, is used, preferably polyester or PBT. In this case, the first plastic material of the core may be configured to contain at least 90 mass%, particularly at least 95 mass%, of PA6.12, and may even be composed entirely of PA6.12. The second plastic material of the outer shell is preferably a soft material having strong elasticity. Preferably, the second plastic material of the outer shell contains at least 80 mass%, particularly at least 95 mass%, of an elastomer, particularly a thermoplastic elastomer or an elastomer blend, or is even composed entirely of a thermoplastic elastomer or an elastomer blend.

[0024] The method for manufacturing the plastic filament to solve the above problem is characterized by foaming the second plastic material of the outer shell before or during extrusion to form a plurality of inner chambers inside the outer shell and a plurality of concave portions on the outer side of the outer shell.

[0025] The dimensions of at least one indentation, preferably a plurality of indentations, are such that in at least one subsequent process step, the width of the indentation is in the range of 1% to 10% of the maximum filament diameter (0.01xD <b≤0.1xD) 내, 특히 최대 필라멘트 직경의 3% 내지 6% 범위(0.03xD≤b≤0.06xD) 내에 있도록 된다.

[0026] A first plastic material for forming the core and a second plastic material for forming the outer shell surrounding the core are co-extruded. Preferably, a foam structure is formed by foaming the plastic material of the outer shell immediately before and / or during extrusion, for example, when the molten plastic exits the extruder. This foam structure may be an open-pore or closed-pore foam. An internal chamber is formed inside the outer shell by foaming. Bubbles are generated on the outer surface of the outer shell, and these bubbles burst or open on their own. Concave or hollow areas are formed on the outer surface of the outer shell by the rupture or opening of the bubbles.

[0027] Indentations formed on the outer surface of a plastic filament due to rupture and / or opening are enlarged in a subsequent process step, preferably by connecting multiple adjacent indentations to form a new, larger indentation. To this end, bubbles formed on the outer surface of the plastic filament, for example by foaming, may be configured to be opened and connected by applying an external force in at least one subsequent process step. The opening of bubbles and the enlargement and connection of indentations may be performed 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 may be configured to be opened by passing or rubbing it over a friction surface.

[0028] Another method to open the bubbles and connect the concave areas on the outer surface of the plastic filament is to pass the plastic filament through a heating section. The elevated temperature increases the gas pressure inside the bubble, ultimately causing it to burst.

[0029] Preferably, the plastic filament is stretched after extrusion. That is, tensile force is applied to the plastic filament, causing its diameter to decrease while simultaneously elongating it. By stretching the plastic filament, more air bubbles are formed on the outer surface, and the concave or hollow areas formed on the outer side extend along the length of the plastic filament, increasing in volume and becoming more suitable for accommodating scraped deposits from surfaces to be cleaned, such as tooth surfaces.

[0030] Preferably, the stretching of the plastic filament is performed in a subsequent process step so that the length of the plastic filament increases by at least 10%, i.e., 110% of the original length.

[0031] The above plastic filament can be used as a toothbrush bristles, an interdental cleaner, or dental floss. In particular, the plastic filament manufactured according to the method described above can be used as a toothbrush bristles, an interdental cleaner, or dental floss.

[0032] Below, a form implemented using plastic filaments as dental floss is explained as an example.

[0033] Dental floss must have high strength and hardly stretch.

[0034] Plastic materials for dental floss with a one-component structure (1K-filament) can be based on polymers from the following groups:

[0035] -Polyester

[0036] - Polyolefin

[0037] - Polyamide

[0038] - Polyurethane

[0039] Or it may be based on the following group of block copolymers:

[0040] - Modified polyester

[0041] - Modified polyamide

[0042] - Modified polyurethane

[0043] - Thermoplastic polyolefin (TPO)

[0044] - Thermoplastic vulcanizates (TPV)

[0045] In addition, a mixture / blend of the above components and / or a vulcanized product obtained from these components are also possible.

[0046] When the dental floss has a two-component structure (2K-filament) having a core and a sheath, the core material is preferably selected from the above components.

[0047] The outer shell material can also be selected from the above components.

[0048] Any combination of the above components is possible.

[0049] Preferably, IK-filaments are manufactured from a matrix material based on a bio-based polyamide such as PA11 or PA10.10.

[0050] Dental floss can be in the form of small strips. The thickness of the strips is preferably between 0.03 mm and 0.20 mm, and particularly between 0.06 mm and 0.15 mm.

[0051] The width of the strip is preferably between 0.5 mm and 4 mm, and particularly between 0.9 mm and 2.5 mm.

[0052] The strip can be implemented in a rectangular shape with sides forming a 90° angle or in a shape with rounding of different curvatures. In the case of a rectangular profile, since there is a risk of injury due to sharp corners, rounded edges with an appropriate radius must be provided. However, other profiles are also possible.

[0053] Typically, dental floss has a smooth surface. To enhance the cleaning effect of dental floss, a non-smooth surface may be used. According to the present invention, this can be implemented in the following three ways:

[0054] 1. "Scratches" formed by the foaming of the plastic material may exist on the surface of the dental floss. During the foaming process, bubbles are generated, and these bubbles rupture on the surface, forming "scratches." More bubbles are moved to the surface by stretching. In the case of 1K-filaments, the entire cross-section is foamed, whereas in the case of 2K-filaments, only the outer shell material is foamed.

[0055] 2. Typically, concave areas can be machined on the surface.

[0056] The grooves can be formed in various shapes. The depth of the indentations varies between 5% and 35% of the floss thickness, preferably between 10% and 20%. The number of grooves per side can be 1 to 6.

[0057] 3. The two options may be combined. Dental floss can cover "scratches" and concave areas.

[0058] The plastic filament (10) illustrated in FIGS. 1 and 2 comprises a core (11) made of a first plastic material extending in the longitudinal direction (LR) of the plastic filament (10), and an outer shell (12) made of a second plastic material that completely surrounds the core (11). The plastic material of the outer shell (12) has a foam structure having a plurality of internal chambers (14) and a plurality of concave portions (15) formed on the outer surface (13) of the outer shell (12).

[0059] The radial thickness (dM) of the outer shell (12) is in the range of 5% to 70% of the maximum diameter (D) of the plastic filament (10), and the maximum diameter (D) of the plastic filament (10) is preferably in the range of 0.1 mm to 0.3 mm.

[0060] A plastic filament (10) is manufactured by co-extruding a core (11) and a shell (12), wherein a second plastic material of the shell (12) is foamed before and / or during extrusion to form an inner chamber (14) inside the shell and a concave portion (15) on the outer surface.

[0061] FIG. 3 shows a concave portion (15) on the outer surface of a plastic filament (10). The concave portion (15) is formed by combining several bubbles and / or concave portions formed when the second plastic material of the outer shell (12) is foamed. The concave portion (15) is formed to be sufficiently large such that the filament length (l) extending along the longitudinal direction (LR) of the plastic filament is significantly larger than the filament circumferential width (b) extending perpendicularly along the circumferential direction of the plastic filament. Preferably, the length (l) of the concave portion (15) is at least twice the width (b) of the concave portion (15). The length (l) of the concave portion (15) may be 5 to 10 times the width (b) of the concave portion (15).

Claims

Claim 1 A plastic filament (10) is extended in the longitudinal direction (LR) and comprises a core (11) made of a first plastic material and an outer shell (12) made of a second plastic material surrounding the core (11), wherein the second plastic material of the outer shell (12) has a foam structure and comprises a plurality of inner chambers (14) and a plurality of concave portions (15) on the outer surface (13) thereof, wherein each of the concave portions (15) has a filament longitudinal length (l) extending along the longitudinal direction of the plastic filament (10) and a width (b) extending perpendicularly in the circumferential direction of the plastic filament (10), wherein at least one of the widths (b) of the concave portions (15) is within the range of 1% to 10% (0.01xD≤b≤0.1xD) of the maximum filament diameter (D), particularly 3% to 6% of the maximum filament diameter Plastic filament (10) characterized by being within a range (0.03xD≤b≤0.06xD). Claim 2 In claim 1, the length (l) of the concave portion (15) is at least 1.1 times (l) the width (b) of the concave portion (15). A plastic filament (10) characterized by being 1.1 xb). Claim 3 A plastic filament (10) according to claim 2, characterized in that the length (l) of the concave portion (15) is at least 2 to 5 times the width of the concave portion (15) (2xb≤l≤5xb). Claim 4 A plastic filament (10) characterized in that, in any one of claims 1 to d, the length (1) of the concave portion 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. Claim 5 A plastic filament (10) characterized in that, in any one of claims 1 to 4, the radial thickness (dM) of the outer shell (12) is at least 5% of the maximum diameter (D) of the plastic filament (10). Claim 6 A plastic filament (10) according to claim 5, characterized in that the radial thickness (dM) of the outer shell (12) is 5% to 70%, particularly 20% to 30% of the maximum diameter (D) of the plastic filament (10). Claim 7 A plastic filament (10) characterized in that, in any one of claims 1 to 6, the maximum diameter (D) of the plastic filament (10) is in the range of 0.05 mm to 1.0 mm, and in particular in the range of 0.1 mm to 0.3 mm. Claim 8 A plastic filament (10) characterized in that, in any one of claims 5 to 7, the radial depth of the concave portion (15) is within the range of 5% to 100% of the radial thickness (dM) of the outer shell (12). Claim 9 A plastic filament (10) according to claim 8, characterized in that the radial depth of the concave portion (15) is within the range of 10% to 30% of the radial thickness (dM) of the outer shell (12). Claim 10 A plastic filament (10) characterized in that, in any one of claims 1 to 9, the concave portion (15) is formed on 10% to 95% of the outer surface (12) of the outer shell. Claim 11 A plastic filament (10) characterized in that, in claim 10, the concave portion (15) is formed on 20% to 40% of the outer surface (12) of the outer shell. Claim 12 A plastic filament (10) characterized in that, in any one of claims 1 to 11, the cross-sectional area of ​​the outer shell (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). Claim 13 A plastic filament (10) characterized in that, in any one of claims 1 to 12, the first plastic material of the core (11) is selected from the group consisting of at least 90% by mass of PA6.12, PA11, PA10.10, PA6.10, PBT (polybutylene terephthalate) and blends of these materials. Claim 14 A plastic filament (10) characterized in that, in any one of claims 1 to 13, the second plastic material of the outer shell (12) comprises at least 80 mass% of an elastomer or an elastomer blend, or is composed entirely of an elastomer or an elastomer blend. Claim 15 A method for manufacturing a plastic filament according to any one of claims 1 to 14, wherein a first plastic material for forming a core (11) and a second plastic material for forming a shell (12) are co-extruded, and the second plastic material of the shell (12) is foamed before and / or during extrusion to form a plurality of inner chambers (14) inside the shell and a plurality of concave portions (15) on the outer surface (13) of the shell (12), and in at least one subsequent process step, the dimensions of at least one of the concave portions (15) are increased such that the width (b) of the concave portion (15) is within the range of 1% to 10% (0.01xD ≤ b ≤ 0.10xD) of the maximum filament diameter (D), particularly within the range of 3% to 6% (0.03xD ≤ b ≤ 0.06xD). Claim 16 A method for manufacturing a plastic filament according to claim 15, characterized in that a plurality of adjacently arranged concave portions are connected to each other through at least one subsequent process step to form a larger new concave portion. Claim 17 A method for manufacturing a plastic filament according to claim 15 or 16, wherein a bubble formed by foaming on the outer surface of the plastic filament (10) is opened by applying an external force in at least one subsequent process step. Claim 18 A method for manufacturing a plastic filament according to any one of claims 15 to 17, wherein the subsequent process 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 filament through a heating section. Claim 19 A method for manufacturing a plastic filament according to any one of claims 15 to 17, characterized in that the plastic filament (10) is stretched in the subsequent process step such that its length increases by at least 10%. Claim 20 Any one use of a plastic filament (10) according to any one of claims 1 to 14, selected from the group consisting of bristles, internal cleaning agents and dental floss. Claim 21 Any one use of the plastic filament (10) manufactured by the method according to any one of claims 15 to 19, selected from the group consisting of toothbrush bristles, internal cleaning agents, and dental floss.

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