EP1381719A1

EP1381719A1 - Thermoplastic monofilament for bristles

Info

Publication number: EP1381719A1
Application number: EP02732524A
Authority: EP
Inventors: Georg Weihrauch; Hans-Ulrich Pusch
Original assignee: Pedex GmbH
Current assignee: Pedex GmbH
Priority date: 2001-03-28
Filing date: 2002-03-26
Publication date: 2004-01-21
Anticipated expiration: 2022-03-26
Also published as: CA2441408A1; AU2002304781B2; BR0208436A; BR0208436B1; WO2002077334A1; US6872449B2; TW585753B; MXPA03008688A; RU2287030C2; EP1381719B1; KR100891016B1; AR033018A1; EG23215A; JP2004523674A; ES2407133T3; US20040091704A1; CN1500163A; DE10115556A1; RU2003131400A; CN1223711C

Abstract

The invention relates to a thermoplastic filament for bristles, which exhibit increased humidity when used, comprising a polymer mixture consisting of at least one polyamide (PA) and at least one thermoplastic polyester (PE), whose proportion of ingredients is selected in accordance with the technical-functional properties relevant to the use of said bristles and in accordance with the ambient conditions relevant to the function of said bristles in the site of utilization.

Description

Thermoplastic monofilament for bristles

The invention relates to a thermoplastic monofilament for bristles that are exposed to increased moisture when in use.

Bristles made of thermoplastic materials are used for brushes of various types, for brushes and the like. They are exposed to very different physical and chemical stresses, which result from their functional use in brushing,

Brushing, polishing, when applying media or the like, on the other hand, result from the conditions immediately prevailing during use or at the place of use. Regarding the latter, the auxiliary media used during use, such as cleaning agents, cleaning agents, cosmetics, water or the like, should be mentioned in particular. The ambient conditions at the place of use include, in particular, increased air humidity which, in interaction with moist auxiliary media, helps to prevent the moist auxiliary media from drying. Bristles must therefore have a property profile that meets these very different requirements. This is exemplified by a toothbrush, in which the different requirements become particularly clear because the bristles initially have an extremely small diameter, which is approximately between 0.05 and 0.4 mm. Furthermore, the bristles are arranged at a short distance from one another and even packed tightly in bundles. On the other hand, bristles for toothbrushes have to show a good high bending behavior in order to be able to dodge in the purely elastic area and on the other hand to be able to return to the starting position without deformation (straightening ability). Due to the multitude of forms of movement and the pressure depending on the user when brushing the teeth, the bristles must have good flexural fatigue strength and fatigue strength, taking into account an appropriate service life. Furthermore, the plastic must be such that the bristle can be processed in mechanical or thermal manufacturing processes, including in particular the attachment of the bristles to the bristle carrier. Finally, the bristles must be rounded at the end of use in order to produce a gentle, yet sufficient brushing effect on the tooth surfaces and in the interdental spaces, on the one hand, and on the other hand without causing the tooth enamel to become too hard

To damage edges or the like or to injure the gums.

Because of the necessarily dense bristles in a toothbrush, the bristles are due to the used

Auxiliary media, such as dentifrice, water, etc., but also due to the increased air humidity prevailing at the place of use, e.g. in the bathroom, are constantly contaminated with moisture, especially since they dry out due to the thick bristles zes on the one hand and the environmental conditions on the other hand would only be possible over a very long period of time.

The increased moisture is accompanied by a weakening of the bristle, which had already been recognized in the natural bristles previously used. Even then, the failure case was referred to as a "wet breakdown" (US 2 309 021). In the case of natural bristles, this failure is primarily due to the fact that they lose their natural fat during the processing process through washing and cleaning processes, which has a hydrophobic effect on the living animal. In the case of a toothbrush, this process is supported by hydrolytic interactions between dentifrices and bristles and by abrasive particles in the dentifrices. This "wet breakdown" was attempted by chemical surface treatment of the natural bristles.

For the reasons mentioned, natural fibers in toothbrushes could only be replaced to a significant extent by synthetic fibers

Plastics were replaced when high-quality thermoplastics were available. Today, bristles for toothbrushes are made exclusively from high-quality polyamides, such as PA 6.10 or 6.12 in particular. used. These polyamide qualities are correspondingly expensive, not least because these high-quality polyamides cannot be used for other reasons.

High-quality polyamides meet the strength requirements in an excellent manner, but are known to absorb moisture to a not inconsiderable extent and thereby partially lose their favorable strength values. This deterioration in the strength properties leads to the failure of the bristle, the smaller its diameter, since the moisture quickly penetrates into the bristle Penetrated core of bristle. Today toothbrushes are often advertised based on the hardness of their bristles, for example as soft (soft), medium (medium) or hard, for which the bristle diameter is primarily responsible. This quality level no longer applies after a period of use due to the moisture load. Moisture absorption and the storage of moisture in the bristle gaps are associated with considerable hygienic problems, since the moisture promotes bacterial growth, which in turn would force longer drying times, but which cannot be observed in practice (US News & World Report 12.10. 87, page 88).

There has therefore been no shortage of attempts to use bristles made of other thermoplastic monofilaments which have already proven themselves in brushes of a different type. Bristles made of thermoplastic polyesters are particularly worth mentioning here, which show comparable bending behavior and alternating bending behavior, but have so far not been able to establish themselves in toothbrushes. One reason for this is the greater hardness and the associated risk of injury to the gums and tooth enamel. They also tend to splice and form burrs during mechanical processing, especially when rounding the ends on the user side. After all, they show a strong binding of dirt, so it is difficult to clean them by rinsing the toothbrush.

Coextruded filaments are known in textile technology (EP 0 763 611 A1), which consist of a polyester core and a polyamide sheath, but the focus here is on other property profiles than is the case with bristles. Furthermore, coextruded monofilaments for toothbrushes are known (WO 97/14830), which consist, among other things, of a polyamide sheath and a polyester core only high-quality polyamides are used in the jacket. In another variant with lower-quality polyamides in the jacket, the core consists of a copolyether ester, which is, however, an elastomer and therefore does not meet the requirements for a bristle for toothbrushes. The same applies to another known composite structure (GB 980 814), in which the core and jacket consist of differently treated polyvinyl chlorides.

The invention is based on the object of proposing a monofilament for bristles, the property profile of which can be optimally adapted to the desired functional and technical requirements and to the ambient conditions during use with reduced material costs.

The object of the invention is achieved on a thermoplastic monofilament forming the starting material for bristles in that the monofilament has a polymer mixture of at least one polyamide (PA) and at least one thermoplastic polyester (PE).

The specific mixing ratio (PA / PE) is selected on the one hand in accordance with the technical and functional properties relevant for the use of the bristle and on the other hand with the environmental conditions relevant for the function of the bristle at the place of use.

With a few exceptions, mixtures of polymers (polymer blend) form multiphase systems, as are also known from metal alloys. They behave differently in a mixture than many low-molecular substances, which, for example, go into solution and form a single-phase system. The cause lies in molecular interactions due to Van der Waals, dipole and hydrogen bridge forces, which are more effective than with similar macromolecules between different polymers in the mixed phase. The degree of entanglement of the macromolecules and the gain in entropy during mixing also play a role, which is also lower in macromoles than in low-molecular substances due to steric effects.

With blends made of thermoplastic polyester and polyamides, polar groups of both polymers have a positive effect on the miscibility. The different segment lengths are the reason for the tendency towards multiphase. This is absolutely desirable if the technical-physical and chemical properties of the components involved in the mixture are retained with sufficiently high binding forces, which is the case with a PA / PE blend. The reason for this is that, in contrast to homogeneous blends, the morphology of the mixed phase PA / PE largely shows the crystallinity inherent in the components, so that the positive properties of the polymers forming the blend are retained. PA / PE blends show a lower stiffness on a filament than pure polyester, but vice versa a better damping behavior, which more closely corresponds to that of nylon. Furthermore, the mixing phase shows a dispersion-like character, which explains better impact resistance compared to the pure mixture components.

The proportions of the polymers in the blend for extrusion of thermoplastic monofilament can be applied to the Anfor ^¬ alteration profile of the bristle optimally adjusted. Thus, the bending behavior and the bend recovery in adjustment can be sung to bristle diameter and length as well as to the specific type of use of the bristle (toothbrushes, massage brushes, hand ^¬ brushes, cosmetic brushes, paints, etc.) to adjust. It can also take into account the physical and chemical conditions prevailing at the place of use due to the media used there (dentifrices, cleaning agents, water etc.) and adapt to the prevailing environmental conditions (dry or humid atmosphere, moisture retention in the bristles, etc.).

The mixing ratio PA / PE can be varied within wide limits without significantly affecting the stability of the mixing phase. For example, the mixing ratio PA / PE can vary between 10/90 mass% and 90/10 mass%, preferably it is between 20/80 mass% and 80/20 mass%.

If the bending strength and its constancy over the period of use, even under extremely humid conditions, is at the forefront of the requirement profile, the PE portion will be increased to the disadvantage of the PA portion. A proportion of PA that is nevertheless adequate ensures improved re-erection ability in the dry state ("bend recovery"). Conversely, the ability to straighten up in extremely humid environmental conditions is adversely affected by a high proportion of PA, which can be explained by the greater water absorption of PA. If the gliding ability of the bristle and the effectiveness of cleaning (abrasion behavior) are in the foreground, the PA portion will be increased at the expense of the PE portion, which also means a gentler treatment of the surface to be cleaned and its surroundings (e.g. the enamel, the gums) accompanied. An optimized mixing ratio PA / PE, which at least most closely corresponds to the requirement profile usual for toothbrushes, is with a PA proportion between 10 and 30 mass% or a PE proportion between 70 and 90 mass%.

Furthermore, the mixing ratio can be adapted to the bristle geometry, taking into account the ambient conditions at the place of use. Thus, the lower the cross-section, the higher the proportion of PE in the mixture ratio. The bristle is cut to prevent moisture penetration into the thin cross section and the associated impairment of the bending behavior and the ability to straighten up.

Regardless of the geometry of the bristle, it is advisable to increase the PE proportion at the expense of the PA proportion, the stronger and / or the longer the exposure to moisture at the place of use of the bristle. However, this recommendation is not mandatory, since in certain applications the moisture absorption of the bristle is desirable in order to better bind liquid active media to the bristle.

The thermoplastic polyester is preferably a polyalkylene terephthalate (PAT), in particular polyethylene terephthalate (PET) or polybutylene terephthalate (PBT) or a mixture thereof.

These thermoplastic polyesters are not only interesting - their technological properties make them particularly suitable for bristles, they are also much cheaper than the high-quality polyamides previously used for toothbrush bristles, such as PA 6.12.

A high proportion of PAT also gives the opportunity to replace high-quality PA, at least in part, with low-value and inexpensive PA such as PA 6.

For example, the polyamide component of the mixture can be selected from the group of higher-quality polyamides, such as PA 6.10, PA 6.12, PA 11, PA 12, on the one hand, and the group of lower-quality polyamides, such as PA 6, PA 6.6, on the other hand, taking into account the requirement that the mixed phase must have sufficient stability. The invention further relates to a thermoplastic monofilament in the form of an at least two-layer coextrudate for bristles which are exposed to increased moisture when in use. In the case of such a coextrudate, at least one layer consists of a polymer mixture of the composition described above.

The coextrudate can have the two layers in concentric form, ie in the form of a core and a jacket. Instead, the coextrudate can also have a plurality of monofilaments which are embedded in a second layer which determines the outer cross section of the monofilament. Furthermore, the coextrudate can consist of a core that defines only a part of the circumference, while the second layer forms segments that complete the circumference, for example have a substantially rectangular cross section, which is predominantly from one layer and only in the corners from the other layer is formed.

Regardless of the specific geometry of which a layer is formed from the polymeric blend of the type according to the inventiveness of the coextrudate, the second layer and the second layer may consist nem single polyamide or mixture of polyamides from egg ^¬, conversely, of a thermoplastic polyester or a mixture of such polyesters can be formed.

If the coextrudate consists of a core and a jacket, it is preferably provided that the core consists of a PAT or a mixture of polyalkylene esters, while the jacket is formed from a polyamide or a polyamide mixture. In the case of a bristle for toothbrushes, the core essentially determines the bending behavior and the ability to straighten up, while the jacket is essentially responsible for the brushing effect, for the distribution of application media or cleaning media. Such a bristle has an increased water absorption in the jacket, but this has no or only an insignificant effect on the strength property, since this is largely determined by the core with its considerably reduced moisture absorption.

The core can also consist only of a thermoplastic polyester or a polyester mixture, since it is not directly involved in the brushing effect, while the jacket consists of the polymer mixture according to the invention. Furthermore, the polymer mixture according to the invention can be present both in the core and in the jacket, the mixing ratio in favor of the PE or PAT component being increased in the core, in the jacket in favor of the PA component.

The excellent strength properties of the polymer mixture according to the invention furthermore make it possible to provide a shell made of any polymer, in particular a PA or a PA mixture, in the case of a core consisting of this mixture. This in turn makes it possible to color the jacket optically differentially, which is only possible to a very limited extent with PE and PE mixtures, while polyamides, for example, can be colored particularly well. This combination of materials also enables the jacket to be made extremely thin. Depending on the intended use, the bristle diameter varies from 5.0 mm for coarse brushes, such as street brushes, to 0.1 mm for toothbrushes, cosmetic brushes etc. For bristles with a diameter of 0.5 to 5.0 mm, the sheath can have a thickness of 0. 01 to 0.5mm. For bristles for toothbrushes with a diameter range of 0.1 to 0.3mm, the thickness of the Coat lie in the range between 10 and 50μ. In this way, a wear indicator can be realized by removing the colored coat with increasing service life and exposing the non-colored, at least differently colored core, so that the user is made aware of the degree of wear visually.

The polymer mixture according to the invention with its stability-determining properties also gives the possibility of also providing three-layer coextrudates, for example by the core consisting of a PAT or a PAT mixture, an intermediate layer made of the polymer mixture according to the invention and an outer layer made of an elastomer or an elastomer. Blend exists. A copolyether ester is particularly recommended because of its affinity for the polyester portion of the middle layer. Again, the outer wear layer fulfills optimal requirements for fulfilling the requirement profile when brushing, cleaning, massaging or applying media.

Finally, the core can also be designed as a hollow core in order to receive media and deliver it to the free end of the bristle.

Finally, it should also be pointed out that if the sheath consists of the polymer mixture according to the invention or of PA or a PA mixture, a bristle consisting of a core and a sheath results in better machining of the bristle ends, in particular a perfect rounding enables without edge formation.

Claims

claims

1. Thermoplastic monofilament for bristles that are exposed to increased moisture when in use, characterized in that the monofilament has a polymer mixture of at least one polyamide (PA) and at least one thermoplastic polyester (PE).

2. Monofilament according to claim 1, characterized in that the mixing ratio PA / PE is selected on the one hand in accordance with the technical and functional properties relevant for the use of the bristle and on the other hand the ambient conditions relevant for the function of the bristle at the place of use.

3. Monofilament according to claim 1 or 2, characterized in that the mixing ratio PA / PE is between 10/90 mass% and 90/10 mass%.

4. Monofilament according to one of claims 1 to 3, characterized in that the mixing ratio PA / PE is between 20/80 mass% and 80/20 mass%.

5. Monofilament according to one of claims 1 to 4, characterized in that the proportion of PE in the mixing ratio PA / PE is higher, the smaller the cross section of the bristle.

6. Monofilament according to one of claims 1 to 5, characterized in that the proportion of PE in the mixing ratio PA / PE is higher, the stronger and / or more permanent the moisture at the place of use of the bristle.

7. Monofilament according to one of claims 1 to 6, characterized in that the thermoplastic polyester is a polyalkylene terephthalate (PAT).

Monofilament according to claim 1, characterized in that the thermoplastic polyester is a polyethylene terephthalate (PET) or a polybutylene terephthalate (PBT) or a mixture thereof.

Monofilament according to one of claims 1 to 8, characterized in that the polyamide (PA) is a mixture of high-quality polyamide and low-value polyamide.

10. Monofilament according to one of claims 1 to 9, characterized in that the polyamide components of the mixture from the group PA 6.10, PA 6.12, PA 11, PA 12 on the one hand and the group PA 6, PA 6.6 on the other hand are selected.

11. Thermoplastic monofilament in the form of an at least two-layer coextrudate for bristles which are exposed to increased moisture when in use, characterized in that at least one layer of Coextrudates consist of a polymer mixture according to one of claims 1 to 10.

12. Monofilament according to claim 11, characterized in that the second layer made of a polyamide or

Mixture of polyamides according to claim 9 or 10.

13. Monofilament according to claim 11, characterized in that the second layer consists of a thermoplastic polyester or a mixture of such polyesters according to claim 7 or 8.

14. Monofilament according to one of claims 11 to 13, wherein the coextrudate consists of a core and a jacket, characterized in that the core consists of a pure PAT or a mixture of polyalkylene esters.

15. Monofilament according to one of claims 11 to 13, characterized in that the core also consists of a polymer mixture according to one of claims 1 to 10.

16. Monofilament according to claim 15, characterized in that the core consists of a polymer mixture PA / PAT with a mixing ratio of 50/50 mass% to 10/90 mass%.

17. Monofilament according to claim 7 and 9, characterized in that PA / PAT is present in the jacket with a ratio of 80/20 mass%, in the core with a ratio of 20/80 mass%.

18. Monofilament according to one of claims 11 to 17, characterized in that at least one layer of the two-layer coextrudate compared to the other Layer is colored optically differentiating.

19. Monofilament according to one of claims 11 to 18, characterized in that the core has a diameter between 0.1 and 5.0 mm and the sheath has a thickness between 0.001 and 0.5 mm.

20. Monofilament according to one of claims 11 to 19, characterized in that for bristles for toothbrushes or cosmetic brushes the core has a diameter between 0.1 and 0.3mm and the sheath has a thickness of 0.001 to 0.005mm.

21. Monofilament according to one of claims 11 to 20, characterized in that it consists of a three-layer

Coextrudate with the core and the shell and an outer layer consists of an elastomer.

22. Monofilament according to one of claims 11 to 21, characterized in that the core is designed as a hollow core.