RETAINING DEVICE COMPRISING TWO MATERIALS

Abstract

A retaining device (50) comprising a base (52) and a plurality of retaining elements (54), the retaining device (50) comprising a first thermoplastic material having a flexural modulus of between 200 and 4500 MPa and a second material selected from the group consisting of a second thermoplastic material having a flexural modulus different by at least 10% and / or at least 100 MPa from the flexural modulus of the first thermoplastic material, a non-thermoplastic material present at a content strictly greater than 1% by mass of the total composition of the retaining device, a mineral and / or vegetable filler having a content less than or equal to 30% by mass of the total composition of the retaining device, or a combination thereof. Figure for abstract: Fig. 4

Description

Title of the invention: RETAINING DEVICE COMPRISING TWO MATERIALS Technical field

[0001] The present disclosure relates to the field of retaining devices, more particularly retaining devices comprising a plurality of retaining elements, for example intended to cooperate with a hook and / or loop counterpart. Prior art

[0002] Particularly in the field of hygiene, retaining devices, for example with hooks, are used and cooperate with a counterpart with loops forming an application zone of the retaining device.

[0003] A disposable diaper is generally composed of an absorbent central part comprising at each end a front part forming a belt provided with two front ears and a rear part forming a belt provided with two rear ears allowing the diaper to be fixed on the person wearing the disposable diaper. Each rear ear is generally provided with a retaining device, for example with hooks, which cooperates with an application zone arranged on the front belt. This application zone is commonly called in the field of hygiene "comfort band" or identified by the expression in English "landing zone".

[0004] In France, 3.5 billion disposable diapers are consumed each year.

[0005] Disposable diapers take several hundred years to degrade naturally in landfills.

[0006] Incineration is a relatively inefficient method given the quantity of liquid that must be evaporated.

[0007] Recycling can be a possible solution to save materials extracted from the environment, but recycling is also complex. Used disposable diapers must be washed of urine and feces, and then the different materials they are made of must be separated and sorted.

[0008] Composting may be a possible solution. In fact, a used disposable diaper contains approximately 75% by mass of biodegradable materials (urine, fecal matter, cellulose). However, in particular the retaining devices, the front band and the chassis of the disposable diaper are generally made of polypropylene which is not compostable.

[0009] Furthermore, shortages of raw materials on a global scale have resulted in rationalizing the production of raw materials and therefore making them scarce. the availability of very specific material in many areas, particularly that of small products of the order of a few millimeters or less, for example hooks for restraint devices.

[0010] The continued need for retaining devices and the rationalization of materials available on the market have therefore introduced a need to find solutions to continue manufacturing retaining devices without introducing considerable cost increases while taking into account the considerable increases in the cost of energy and raw materials as well as existing manufacturing processes.

[0011] In addition, the materials available, particularly on the market, are increasingly coming from external or internal recycling channels, for example pre-consumer and / or post-consumer, which are in a degraded, or even very degraded, state, not allowing them to be used directly in the manufacture of restraint devices. Such materials being available, there is therefore also a need to revalue these materials. Statement of the invention

[0012] The present disclosure aims to remedy at least in part these drawbacks.

[0013] For this purpose, the present disclosure relates to a retaining device, comprising: - a base extending in a longitudinal direction having an upper face and a lower face, - a plurality of retaining elements extending from the upper face of the base, each retaining element comprising a rod, the retaining device comprising mainly, in mass percentage, in particular consisting of the fact that it is formed from a first thermoplastic material having a flexural modulus greater than or equal to 200 MPa and less than or equal to 4500 MPa and a second material, the second material being chosen from the group consisting of: - a second thermoplastic material having a flexural modulus different by at least 10% and / or at least 100 MPa from the flexural modulus of the first thermoplastic material, - of a non-thermoplastic material present at a content strictly greater than 1% by mass of the total composition of the retaining device, in particular greater than or equal to 1.1%, in particular greater than or equal to 1.2%, - a mineral and / or vegetable filler whose content is less than or equal to 30% by mass of the total composition of the retaining device, or - a combination of these.

[0014] The flexural modulus is measured according to ISO 178:2019.

[0015] Thanks to the composition of the retaining device, the retaining device can be compostable in an industrial environment, for example according to standard EN 13432:2000, or can be based on compostable materials, and / or derived from biomass, for example according to standard EN 16785-1:2016 and / or standard ASTM D 6866:2022, and can be taken care of at the end of its life in industrial composting and / or recycling channels.

[0016] Due to the composition of the retaining device, the retaining device may be made from recycled material, for example pre-consumer and / or post-consumer.

[0017] Thanks to the composition of the retaining device, it is possible to continue the manufacture of retaining elements without radically changing the current manufacturing lines of such retaining devices and / or the manufacturing methods of such retaining devices and / or to obtain retaining devices with performances at least equivalent to those of the prior art or even better.

[0018] Thanks to the composition of the retaining device, surprisingly, it is possible to obtain retaining elements and / or preforms intended to form retaining elements which are easier to shape, in particular to mold and / or to demold and / or to calender while having a shaping temperature range acceptable for current manufacturing lines and / or for current manufacturing methods of such retaining devices.

[0019] It is understood by majority that the mass percentage of the first thermoplastic material is greater than the mass percentages of each material constituting the second material.

[0020] By way of non-limiting examples, the mass percentage of the first thermoplastic material may be greater than or equal to 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95% of the mass percentage of the retaining device.

[0021] A thermoplastic material is a material capable of being repeatedly softened by heating, hardened by cooling within a temperature range characteristic of the plastic material in question and, in the softened state, of being shaped by plasticity in a mold, by extrusion or forming, according to article 2.1177 of standard EN ISO 472:2013.

[0022] It is understood that the first thermoplastic material and / or the second thermoplastic material are materials which exhibit thermoplastic behavior. However, these thermoplastic materials may comprise non-thermoplastic materials in such an amount that the behavior of the material is still thermoplastic behavior.

[0023] A mineral and / or vegetable filler is a relatively inert solid material, added in particular to modify the resistance of the material, in particular the shaping of the material and / or the stability of the material and / or the processing properties, for example shaping, of the material and / or to reduce production costs.

[0024] As non-limiting examples, the filler may be in the form of powder or fibers.

[0025] In some embodiments, the first thermoplastic material may have a flexural modulus greater than or equal to 800 MPa and less than or equal to 4000 MPa.

[0026] In some embodiments, the first thermoplastic material may have a number average molecular weight greater than or equal to 20,000 g / mol.

[0027] The number-average molecular mass can be measured using high-temperature SEC (in accordance with the acronym for "Size Exclusion Chromatography").

[0028] In some embodiments, the non-thermoplastic material may comprise a plasticizer and / or a fluidizer and / or a lubricant and / or a stabilizer.

[0029] In some embodiments, the non-thermoplastic material may comprise a molding agent and / or a release agent and / or a processing aid.

[0030] A plasticizer is a compound that allows the softening range of a material to be lowered, making it easier to shape.

[0031] A fluidifier is a compound that reduces the viscosity of a material.

[0032] A lubricant is a compound which makes it possible to reduce the friction of the material on itself or on surfaces which the material contacts during its processing, for example its shaping.

[0033] A stabilizer is a compound that increases the stability of the material over time and / or in various environments.

[0034] A processing aid is also identified by the English expression “Processing aids”.

[0035] In some embodiments, the non-thermoplastic material may have several effects simultaneously, for example that of plasticizer and / or fluidizer and / or lubricant and / or processing aid.

[0036] In some embodiments, the second material may comprise a non-thermoplastic material having a molecular weight at least 10% lower than the number average molecular weight of the first thermoplastic material and / or less than or equal to 15000 g / mol.

[0037] In certain embodiments, the second thermoplastic material may have several effects simultaneously, for example that of plasticizer and / or fluidizer and / or lubricant and / or processing aid agent.

[0038] In certain embodiments, the first thermoplastic material may have an MFR greater than or equal to 1 g / 10 min, in particular greater than or equal to 10 g / 10 min, in particular greater than or equal to 15 g / 10 min and / or less than or equal to 300 g / 10 min, in particular less than or equal to 200 g / 10 min, in particular less than or equal to 170 g / 10 min.

[0039] MFR is the melt flow index of thermoplastic materials and is measured according to ISO 1133-1:2022 and / or ISO 1133-2:2011.

[0040] In some embodiments, the second material, especially the second thermoplastic material, may have an MFR different by at least 10% and / or at least 5 g / 10 min from the MFR of the first thermoplastic material.

[0041] In certain embodiments, the second material may comprise the non-thermoplastic material, the non-thermoplastic material being, at a temperature less than or equal to 150°C, in particular less than or equal to 100°C, in particular at room temperature (of the order of 25°C), in the form of a liquid or in an intermediate form between a liquid form and a solid form, in particular in the form of a wax.

[0042] In some embodiments, the non-thermoplastic material may have a kinematic viscosity of less than or equal to 700 mm2 / s, measured according to ASTM D445-21E02, at the processing temperature, for example at the forming temperature.

[0043] The processing temperature, in particular the shaping temperature, may be greater than or equal to 80°C, in particular greater than or equal to 95°C and / or less than or equal to 250°C, in particular less than or equal to 200°C.

[0044] In some embodiments, the non-thermoplastic material may have a dynamic viscosity of less than or equal to 500 mPas.s, measured according to ASTM D445-21E02, at the processing temperature, for example at the forming temperature.

[0045] The processing temperature, in particular the shaping temperature, may be greater than or equal to 80°C, in particular greater than or equal to 95°C and / or less than or equal to 250°C, in particular less than or equal to 200°C.

[0046] By way of non-limiting example, the first and / or the second thermoplastic material comprises: - a polyolefin, in particular a polypropylene (PP) and / or a polyethylene (PE), in particular a bio-sourced polyethylene (Bio-PE) and / or their copolymers, and / or - a polyester, in particular a polyethylene terephthalate (PET), for example a bio-sourced polyethylene terephthalate (Bio-PET), and / or a biodegradable polyester and / or a Polyhydroxyalkanoate (PHA) and / or a poly-lactic acid (PLA) and / or a polybutylene adipate terephthalate (PBAT) and / or a Polybutylene succinate (PBS) and / or a poly(butylene succinate co-butylene adipate) (PBS A) and / or a Poly(Polybutylene succinate) (PES) and / or a poly(trimethylene succinate) (PTS) and / or a poly(tetramethylene adipate-co-terephthalate) (PTAT) and / or a Polycaprolactone (PCL) and / or a Thermoplastic Starch (TPS), and / or - a polyamide (PA) in particular a bio-sourced polyamide (Bio-PA), and / or a casein derivative and / or - a mixture of two or more of these thermoplastic materials.

[0047] In some embodiments, the retainer may be free of a colorant, for example a TiO2-based colorant.

[0048] In certain embodiments, the second material may comprise a mineral and / or vegetable filler, for example a colorant, for example a TiO2-based colorant, in particular at a mass percentage of the composition less than or equal to 1.5%, in particular less than or equal to 1%.

[0049] In some embodiments, the first thermoplastic material may be a material based on a first polyolefin, for example a first material based on a first polypropylene, and the second material may comprise the second thermoplastic material, the second thermoplastic material being based on a second polyolefin, for example a second polypropylene.

[0050] In certain embodiments, the ratio of the mass percentage of the second thermoplastic material to the first thermoplastic material may be greater than or equal to 0.3, in particular greater than or equal to 0.45, and / or less than or equal to 0.7, in particular less than or equal to 0.60.

[0051] In certain embodiments, the MFR of the first thermoplastic material may be greater than or equal to 10 g / 10 min, in particular greater than or equal to 15 g / 10 min, and / or less than or equal to 30 g / 10 min, in particular less than or equal to 25 g / 10 min.

[0052] In certain embodiments, the MFR of the first thermoplastic material may be greater than or equal to 25 g / 10 min, in particular greater than or equal to 35 g / 10 min, and / or less than or equal to 45 g / 10 min, in particular less than or equal to 40 g / 10 min.

[0053] In certain embodiments, the MFR of the second thermoplastic material may be greater than or equal to 50 g / 10 min, in particular greater than or equal to 55 g / 10 min, and / or less than or equal to 70 g / 10 min, in particular less than or equal to 65 g / 10 min.

[0054] In certain embodiments, the MFR of the second thermoplastic material may be greater than or equal to 10 g / 10 min, in particular greater than or equal to 15 g / 10 min, and / or less than or equal to 40 g / 10 min, in particular less than or equal to 35 g / 10 min.

[0055] In certain embodiments, the flexural modulus of the first thermoplastic material may be greater than or equal to 1900 MPa, in particular greater than or equal to 2000 MPa, and / or less than or equal to or equal to 2500 MPa, in particular less than or equal to 2300 MPa.

[0056] In certain embodiments, the flexural modulus of the first thermoplastic material is greater than or equal to 1300 MPa, in particular greater than or equal to 1500 MPa, and / or less than or equal to 2000 MPa, in particular less than or equal to 1900 MPa.

[0057] In certain embodiments, the flexural modulus of the second thermoplastic material may be greater than or equal to 1500 MPa, in particular greater than or equal to 1700 MPa, and / or less than or equal to 2400 MPa, in particular less than or equal to 2000 MPa, for example strictly less than or equal to 2000 MPa.

[0058] In certain embodiments, the flexural modulus of the second thermoplastic material may be greater than or equal to 1100 MPa, in particular greater than or equal to 1300 MPa, and / or less than or equal to 1800 MPa, in particular less than or equal to 1700 MPa.

[0059] In certain embodiments, the first thermoplastic material may be based on a polyester, and the second material may comprise a non-thermoplastic material present at a content greater than or equal to 1.5% by mass of the total composition of the retaining device, in particular greater than or equal to 2%, in particular greater than or equal to 5%, and / or less than or equal to 25% by mass of the total composition of the retaining device, in particular less than or equal to 20%, in particular less than or equal to 18%, more precisely less than or equal to 15%, in certain cases less than or equal to 13%.

[0060] In certain embodiments, the MFR of the first polyester-based thermoplastic material may be greater than or equal to 10 g / 10 min, in particular greater than or equal to 20 g / 10 min, and / or less than or equal to 50 g / 10 min, in particular less than or equal to 40 g / 10 min.

[0061] In certain embodiments, the non-thermoplastic material may have a molecular mass greater than or equal to 250 g / mol, in particular greater than or equal to 300 g / mol and / or less than or equal to 19000 g / mol, in particular less than or equal to 15000 g / mol, in particular less than or equal to 10000 g / mol, more particularly less than or equal to 800 g / mol and in certain cases less than or equal to 550 g / mol.

[0062] In certain embodiments, the ratio of the mass percentage of the second material to the first thermoplastic material may be greater than or equal to 0.02, in particular greater than or equal to 0.05, in particular greater than or equal to 0.1 and / or less than or equal to 0.30, in particular less than or equal to 0.25, in particular less than or equal to 0.24.

[0063] In certain embodiments, the non-thermoplastic material may be based on fatty acid derivatives, for example a fatty ester and / or a fatty amide, and / or citrate and / or polyalkylene glycol and / or an azelaic acid, in particular being in the form of oil and / or wax and / or flakes.

[0064] In some embodiments, the first thermoplastic material may be based on a first polyester, and the second material may comprise the second thermoplastic material, the second thermoplastic material being based on a second polyester.

[0065] In certain embodiments, the MFR of the first thermoplastic material may be greater than or equal to 15 g / 10 min, in particular greater than or equal to 25 g / 10 min, and / or less than or equal to 55 g / 10 min, in particular less than or equal to 45 g / 10 min.

[0066] In certain embodiments, the MFR of the second thermoplastic material may be less than or equal to 25 g / 10 min, in particular less than or equal to 15 g / 10 min, in particular less than or equal to 10 g / 10 min and / or greater than or equal to 0.5 g / 10 min.

[0067] In certain embodiments, the flexural modulus of the first thermoplastic material may be greater than or equal to 1500 MPa, in particular greater than or equal to 2500 MPa, in particular greater than or equal to 3000 MPa and / or less than or equal to 4500 MPa, in particular less than or equal to 4000 MPa.

[0068] In certain embodiments, the tensile modulus of the second thermoplastic material may be less than or equal to 2500 MPa, in particular less than or equal to 1500 MPa, in particular less than or equal to 1200 MPa, in certain cases less than or equal to 800 MPa and / or greater than or equal to 15 MPa, in particular greater than or equal to 50 MPa, in particular greater than or equal to 100 MPa.

[0069] The tensile modulus is measured according to ISO 527-1:2019 and / or ISO 527-2:2012.

[0070] In certain embodiments, the ratio of the mass percentage of the second thermoplastic material, for example of the second polyester of the second thermoplastic material, to the first thermoplastic material, for example of the first polyester of the first thermoplastic material, may be greater than or equal to 0.20, in particular greater than or equal to 0.30, in particular greater than or equal to 0.35 and / or less than or equal to 0.70, in particular less than or equal to 0.60, in particular less than or equal to 0.55.

[0071] In certain embodiments, the polyester of the first thermoplastic material and the polyester of the second thermoplastic material may have different names, for example one is based on PLA and the other on PB AT or vice versa or again for example one is based on a PET, a Bio-PET, a biodegradable polyester, a PHA and / or a PLA and / or a PB AT and / or a PBS and / or a PBS A and / or a PES and / or a PTS and / or a PTAT and / or a PCL and / or a TPS, and the other is based on a second thermoplastic material of different name and also chosen from this same list.

[0072] In certain embodiments, the second material may comprise a non-thermoplastic material which is present at a content greater than or equal to 1.5% by mass of the total composition of the retaining device, in particular greater than or equal to 2%, in particular greater than or equal to 4% and / or less than or equal to 15%, in particular less than or equal to 12%, in particular less than or equal to 10%.

[0073] In certain embodiments, the second material may comprise a mineral and / or vegetable filler whose content is less than or equal to 25% by mass of the total composition of the retaining device, in particular less than or equal to 20% and / or greater than or equal to 5%, in particular greater than or equal to 10%, in particular greater than or equal to 13%.

[0074] In certain embodiments, the device may have a weight less than or equal to 200 g / m2, in particular less than or equal to 150 g / cm2, in particular less than or equal to 120 g / cm2.

[0075] In some embodiments, the retaining elements may have a height greater than or equal to 120 pm and / or less than or equal to 400 pm.

[0076] In certain embodiments, the base may have a thickness greater than or equal to 25 μm, in particular greater than or equal to 40 μm and / or less than or equal to 150 μm, in particular less than or equal to 100 μm.

[0077] The thickness of the base is measured between the upper face and the lower face in a direction perpendicular to the upper face and the lower face. The upper face of the base may be flat or substantially flat. The lower face of the base may be flat or substantially flat.

[0078] In some embodiments, each retaining member may comprise a rod topped with a head; each rod comprising a lower end connected to the base, and an opposite upper end from which the head extends.

[0079] The head typically extends from the upper end of the rod. The head may have at least one portion extending beyond the upper end of the rod, in order to define a gripping portion or lobe adapted to engage fibers and / or loops and / or complementary retaining elements to produce a self-gripping connection. The head thus typically has a maximum section having a surface area strictly greater than the surface area of ​​the upper end of the rod.

[0080] In certain embodiments, the head has a thickness greater than or equal to 20 μm, in particular greater than or equal to 40 μm, and / or less than or equal to 150 μm, in particular less than or equal to 70 μm, more particularly less than or equal to 60 μm.

[0081] In certain embodiments, the head has a thickness greater than or equal to 120 μm, in particular greater than or equal to 150 μm, and / or less than or equal to 550 μm, in particular less than or equal to 500 μm, more particularly less than or equal to 480 μm.

[0082] As a non-limiting example, in a first direction, for example in the MD direction (according to the acronym in English for “Machine Direction”, the rod has a minimum width and the head has a maximum width, the ratio of the minimum width of the rod to the maximum width of the head is greater than or equal to 0.5, in particular greater than or equal to 0.55, in particular greater than or equal to 0.6 and / or less than or equal to 1.0, in particular less than or equal to 0.95, in particular less than or equal to 0.90.

[0083] By way of non-limiting example, in a second direction, in particular perpendicular to the first direction, for example in the CD direction (according to the acronym in English for “Cross Direction”), the rod has a minimum width and the head has a maximum width, the ratio of the minimum width of the rod to the maximum width of the head is greater than or equal to 0.35, in particular greater than or equal to 0.4, in particular greater than or equal to 0.45 and / or less than or equal to 1.0, in particular less than or equal to 0.8, in particular less than or equal to 0.70, in particular less than or equal to 0.65.

[0084] By way of non-limiting example, in a second direction, in particular perpendicular to the first direction, the rod has a minimum width and the head has a maximum width, the ratio of the minimum width of the rod to the maximum width of the head is greater than or equal to 0.90, in particular greater than or equal to 0.95, and / or less than or equal to 1.1, in particular less than or equal to 1.05.

[0085] In certain embodiments, the rod has a height greater than or equal to 150 pm, in particular greater than or equal to 200 pm and / or less than or equal to 330 pm, in particular less than or equal to 300 pm.

[0086] In certain embodiments, the ratio of the thickness of the head and the height of the stem is greater than or equal to 0.05, in particular greater than or equal to 0.1, and / or less than or equal to 0.7, in particular less than or equal to 0.3, in certain cases less than or equal to 0.25.

[0087] In certain embodiments, in a first direction, for example in the MD direction, the rod having a proximal portion arranged on the base side and a distal portion arranged on the head side, the width of the rod at its proximal portion may be greater than the width of the rod at its distal portion.

[0088] In certain embodiments, in a second direction, in particular perpendicular to the first direction, for example in the CD direction, the rod having a proximal portion arranged on the base side and a distal portion arranged on the head side, the width of the rod at its proximal portion may be greater than the width of the rod at its distal portion.

[0089] In some embodiments, the retaining element may have at least one plane of symmetry perpendicular to the plane formed by the base and passing through the center of the rod and / or the center of the head.

[0090] In some embodiments, the retaining element may have a single plane of symmetry perpendicular to the plane formed by the base and passing through the center of the rod and / or the center of the head.

[0091] In certain embodiments, the retaining element may have at least two planes of symmetry perpendicular to the plane formed by the base and passing through the center of the rod and / or the center of the head, in particular the two planes of symmetry of the retaining element being perpendicular to each other.

[0092] In certain embodiments, the retaining elements may typically be made from a preform (not shown) resulting from molding, in particular by continuous or discontinuous injection or by extrusion comprising at least one rod, and optionally a head, the upper end of the rod and / or the head of the preform of which is deformed or are deformed. The deformation is typically carried out by calendering, for example by hot calendering, for example in one or two calendering steps.

[0093] In some embodiments, the retaining elements may typically be formed integrally with the base, in particular, the stem and head of the retaining elements are formed integrally with the base.

[0094] In certain embodiments, the retaining elements and the base may comprise predominantly, in mass percentage, in particular consist of the fact that they are formed, of said first thermoplastic material and of said second material.

[0095] In certain embodiments, the stem and the head of the retaining elements as well as the base may comprise mainly, in mass percentage, in particular consist of the fact that they are formed, of said first thermoplastic material and of said second material.

[0096] In some embodiments, the retaining elements may be arranged in the form of rows and columns which may be aligned, or arranged in a staggered pattern. More specifically, the different retaining elements may be arranged so as to be aligned in the transverse direction CD and / or in the machine direction MD, or be offset so as to form a staggered or honeycomb pattern, two successive rows or two columns then being offset respectively in the transverse direction and / or in the machine direction, by a pitch corresponding to half the transverse interval and / or half the machine interval respectively.

[0097] In some embodiments, each retaining element may have a head thickness which is the distance measured in a direction perpendicular to the base between the upper end of the rod and the upper end of the retaining element.

[0098] In some embodiments, each retaining element may have a hooking height which is the distance measured in a perpendicular direction at the base between the lower end of the head and the upper end of the head, the hanging height of the head is greater than or equal to the thickness of the head.

[0099] In certain embodiments, the retaining elements may typically have a hooking height greater than or equal to 30 μm, in particular greater than or equal to 40 μm and / or less than or equal to 120 μm, in particular less than or equal to 70 μm, in particular less than or equal to 60 μm.

[0100] In certain embodiments, the retaining elements may typically have a hooking height greater than or equal to 150 μm, in particular greater than or equal to 200 μm and / or less than or equal to 650 μm, in particular less than or equal to 550 μm, in particular less than or equal to 500 μm, in particular less than or equal to 370 μm.

[0101] In some embodiments, the retaining elements may typically be adapted or formed such that the retainer may cooperate with loops to provide contact closure.

[0102] Generally speaking, it is possible to distinguish two types of self-gripping connection, those whose retaining elements cooperate with other retaining elements of the same types / natures or in the form of fibers and / or filaments and / or loops to produce mechanical connections and those whose retaining elements cooperate with surfaces to produce adhesive type connections (Gecko) or using Van der Waals forces. Although this second type of connection can be considered in certain cases as a so-called self-gripping connection, such retaining elements using Van der Waals forces have a behavior and properties that are completely different from those using mechanical connections.Indeed, in the case of retaining elements using Van der Waal forces, only the upper faces of the heads ensure the attachment to the receiving surface, whereas in the case of retaining elements for mechanical attachment, the attachment is not ensured by the upper face of the heads but by the lower face of the head and the rod. According to one example, the retaining device according to the invention is only suitable for making mechanical connections.

[0103] In certain embodiments, the retaining device may comprise a number of retaining elements per cm2 greater than or equal to 10, in particular greater than or equal to 50, in particular greater than or equal to 125, in particular greater than or equal to 200 and / or less than or equal to 700, in particular less than or equal to 550, in particular less than or equal to 450, in certain cases less than or equal to 315.

[0104] In certain embodiments, the retaining device may have a peel strength greater than or equal to 2 N, in particular greater than or equal to 3 N, measured according to the method described in the remainder of the description.

[0105] Method for measuring peel resistance.

[0106] To measure the peeling performance as a function of overfeeding, a measurement of the resistance to opening at 180° of an assembled hook / comfort strip pair is used. A strip of hooks, for example 15 mm wide and 25.4 mm long, assembled on an 80 g / m2 paper support and 25.4 mm wide, is pressed onto a comfort strip sample measuring 50 mmx50 mm using a single 2 kg roll, the relative orientations of the products being identical to those used on the diaper. A pull of 1 kg is then applied for 10 seconds to the hook support so as to simulate the closure of a diaper, in particular a diaper with elastic ears. The paper supporting the hook is then inserted into the movable upper jaw of a traction frame, for example type 1 / M from MTS System equipped with a 100 N load cell, and the comfort band is inserted into the lower jaw.The distance between the two jaws is 50 mm. To measure the opening force, the upper part of the frame then moves from bottom to top at a speed of 305 mm / min. The value of the maximum force supplied by the machine is then recorded, as well as the energy value corresponding to the force under the surface of the test curve taken over the first 13 millimeters of travel of the traction frame. When the width of the product is different from 15 mm, the value obtained is recalculated proportionally to 15 mm.

[0107] In certain embodiments, the retaining device may have a shear strength greater than or equal to 35 N, in particular greater than or equal to 45 N, measured according to the method described in the remainder of the description.

[0108] Method for measuring shear strength.

[0109] To measure shear performance as a function of supercharging, a 50 mmx50 mm sample of comfort strip is taken and glued to a rigid plate, for example metal, with double-sided adhesive.

[0110] A strip of hooks, for example 15 mm wide and 25.4 mm long, assembled on a 250 g / m2 paper support, is engaged by the operator on the comfort strip, respecting the relative orientations of the products on the layer, and pressure is exerted for 3 seconds by the operator with the thumb.

[0111] A pull of 1 kg is then applied for 5 seconds to the hook support so as to simulate the closing of a diaper, in particular a diaper with elastic ears.

[0112] The metal plate supporting the comfort band is inserted into the movable upper jaw, for example of a traction frame of the type 1 / M from MTS System equipped with a 100N dynamometric cell.

[0113] The paper supporting the hook is then inserted into the fixed lower jaw.

[0114] The movement of the frame will be in the same direction as the 1 kg pull. The distance between the two jaws is 76 mm. To measure the opening force, the upper part of the frame then performs a translation from bottom to top at a constant speed of 305 mm / min. The test is carried out until the loop and the hook are completely disengaged. The maximum force value is then recorded on the curve obtained. When the width of the product is different from 15 mm, the value obtained is recalculated proportionally to 15 mm.

[0115] The present disclosure also relates to a laminated assembly comprising the retaining device as defined above and a non-woven sheet.

[0116] By way of non-limiting examples, the non-woven sheet may be produced using Dry-laid (dry process), Wet-laid (wet process), or Spun-laid (melted / extruded process) technology and consolidated by mechanical, thermal, chemical and / or adhesive bonding.

[0117] According to one example, the sheet is made of a consolidated carded type nonwoven, in particular a Spunlace type nonwoven, i.e. consolidated by hydro-bonding.

[0118] The nonwoven web may be made from various synthetic and / or natural materials. Exemplary natural materials are cellulose fibers, such as cotton, jute, linen and the like and may also include re-processed cellulose fibers, such as rayon or viscose. Natural fibers for a nonwoven material may be prepared using various processes such as carding. Exemplary synthetic materials include, but are not limited to, synthetic plastic polymers, which are known to form fibers that include, but are not limited to, polyolefins, e.g., polyethylene, polypropylene, polybutylene and the like; polyamide, e.g., polyamide 6, polyamide 6.6, polyamide 10, polyamide 12 and the like; polyesters, for example polyethylene terephthalates, polybutylene terephthalates, polylactic acids and the like, polycarbonates, polystyrenes, thermoplastic elastomers, polymeric vinyls, polyurethanes and blends and copolymers thereof. For example, the nonwoven may be a nonwoven of the Spunbond, Spunmelt, carded thermally bonded, SMS, SMMS, SS, SSS, SSMMS, SSMMMS, Air through or other type. For example, the nonwoven may be a nonwoven comprising a different combination of Spunbond “S” and Meltblown “M” layers. These examples are given without limitation.

[0119] The present disclosure also relates to a method of manufacturing a retaining device as defined previously comprising the following steps: - the first thermoplastic material having a flexural modulus greater than or equal to 200 MPa and less than or equal to 4500 MPa and the second material are provided, the second material being chosen from the group consisting of: - a second thermoplastic material having a flexural modulus different by at least 10% and / or at least 100 MPa from the flexural modulus of the first thermoplastic material, - of a non-thermoplastic material present at a content strictly greater than 1% by mass of the total composition of the retaining device, - a mineral and / or vegetable filler whose content is less than or equal to 30% by mass of the total composition of the retaining device, or - a combination of these. - the first thermoplastic material and the second material are mixed - the retaining device is formed from the mixture of the first thermoplastic material and the second material.

[0120] In certain embodiments, the step of mixing the first thermoplastic material and the second material is carried out in line, for example in the extruder and / or in a dosing device arranged at the inlet of the extruder.

[0121] In some embodiments, after the step of mixing the first thermoplastic material and the second material, the method comprises the steps of: - the mixture of the first thermoplastic material and the second material is packaged for transport, then - the mixture of the first thermoplastic material and the second material is deconditioned to form the retaining device.

[0122] In some embodiments, the step of forming the retainer comprises a sub-step of deforming preforms of the retaining elements.

[0123] The present disclosure further relates to an absorbent article, for example of the baby diaper type or an adult incontinence diaper, comprising a top sheet, a bottom sheet and an absorbent core, arranged between the two top and bottom sheets, and at least one retaining device as defined previously.

[0124] In certain embodiments, the absorbent article comprises at least complementary retaining elements, arranged and configured to cooperate with the retaining elements of the retaining device to achieve the closure of the absorbent article and / or to achieve the assembly, in particular the temporary assembly, of one or more sub-assemblies of the absorbent article. Brief description of the drawings

[0125] Other characteristics and advantages of the subject of the present disclosure will emerge from the following description of embodiments, given as non-limiting examples, with reference to the appended figures.

[0126] [Fig.l] [Fig.l] is a schematic sectional view of a molding apparatus for forming a retainer.

[0127] [Fig.2] [Fig.2] is a flowchart representing the steps of a method of manufacturing a retaining device.

[0128] [Fig.3] [Fig.3] is a schematic perspective view of a retaining element according to a first embodiment.

[0129] [Fig.4] [Fig.4] is a schematic perspective view of a retaining element according to a second embodiment. Detailed description

[0130] The invention will be illustrated by examples (Ex 1 to Ex 5) and comparative examples (Comp 1 to Comp 3).

[0131] Example 1 (Ex 1)

[0132] Example 1 is a mixture of two polypropylenes and a mineral filler.

[0133] The first thermoplastic material is a first polypropylene having an MFR (230°C / 2.16 kg) of 20 g / 10 min and a flexural modulus of 2200 MPa.

[0134] The second material is a mixture of the second thermoplastic material, i.e. a second polypropylene having an MFR (230°C / 2.16 kg) of 60 g / 10 min and a flexural modulus of 1800 MPa, and the mineral filler, i.e. a TiO2-based colorant.

[0135] The mass composition is as follows: 64.2% of the first polypropylene, 35% of the second polypropylene and 0.8% of the dye.

[0136] Example 2 (Ex 2)

[0137] Example 2 is a mixture of two polypropylenes and a mineral filler.

[0138] The first thermoplastic material is a first polypropylene having an MFR (230°C / 2.16 kg) of 40 g / 10 min and a flexural modulus of 1700 MPa.

[0139] The second material is a mixture of the second thermoplastic material, i.e. a second polypropylene having an MFR (230°C / 2.16 kg) of 25 g / 10 min and a flexural modulus of 1500 MPa, and the mineral filler, i.e. a TiO2-based colorant.

[0140] The mass composition is as follows: 65% of the first polypropylene, 34% of the second polypropylene and 1% of the dye.

[0141] Example 3 (Ex 3)

[0142] Example 3 is a mixture of a PLA and a plasticizer.

[0143] The first thermoplastic material is a PLA having an MFR (190°C / 2.16 kg) of 30 g / 10 min and a flexural modulus of 3400 MPa.

[0144] The second material is a non-thermoplastic material: a plasticizer based on a citric acid ester having a molecular mass of less than 600 g / mol. The plasticizer also has a lubricating and fluidifying effect.

[0145] The mass composition is as follows: between 85% and 90% PLA and between 15% and 10% plasticizer.

[0146] Example 4 (Ex 4)

[0147] Example 4 is a mixture of a PLA and a plasticizer.

[0148] The first thermoplastic material is a PLA having an MFR (190°C / 2.16 kg) of 30 g / 10 min and a flexural modulus of 3400 MPa.

[0149] The second material is a non-thermoplastic material: a plasticizer based on a citric acid ester having a molecular mass of less than 600 g / mol. The plasticizer also has a lubricating and fluidifying effect.

[0150] The mass composition is as follows: between 80% and 85% PLA and between 20% and 15% plasticizer.

[0151] Example 5 (Ex 5)

[0152] Example 5 is a mixture of a PLA and a plasticizer.

[0153] The first thermoplastic material is a PLA having an MFR (190°C / 2.16 kg) of 35 g / 10 min, a flexural modulus of 3600 MPa and a number average molecular weight of approximately 44000 g / mol.

[0154] The second material is a mixture of a second thermoplastic material, non-thermoplastic materials and a mineral filler.

[0155] The second thermoplastic material is a blend of PLA and PBAT having an MFR (190°C / 2.16 kg) of 3-5 g / 10 min and a tensile modulus of 185-420 MPa.

[0156] The non-thermoplastic material is a mixture of a lubricant and a fluidizer each having a molecular mass less than or equal to 1100 g / mol. According to one example, the lubricant comprises a processing aid and a slip agent, the slip agent being in particular based on fatty acid derivatives, for example a fatty amide.

[0157] The mineral filler is talc.

[0158] The mass composition is as follows: 52% (+ / - 2%) of PLA, 23 (+ / - 2%) of the second thermoplastic material, around 2.5% of lubricant, around 6% of fluidizer and around 16% of talc.

[0159] Comparative Example 1 (Comp 1)

[0160] Comparative Example 1 consists of a polypropylene having an MFR (230°C / 2.16 kg) of 35 g / 10 min and a flexural modulus of 1600 MPa.

[0161] Comparative Example 2 (Comp 2)

[0162] Comparative Example 2 consists of a polypropylene having an MFR (230°C / 2.16 kg) of 100 g / 10 min and a flexural modulus of 1500 MPa.

[0163] Comparative Example 3 (Comp 3)

[0164] Comparative example 3 consists of a PLA having an MFR (190°C / 2.16 kg) of 30 g / 10 min and a flexural modulus of 3400 MPa.

[0165] Formation of the retaining device

[0166] [Fig.l] shows a schematic sectional view of a molding apparatus 10 for forming a retaining device. The molding apparatus 10 comprises a molding strip 12 closed on itself and comprising an internal face 14, an external face 16, a plurality of through cavities 18 extending from the external face 16 to the internal face 14.

[0167] The molding strip 12 is stretched over means for driving the molding strip 12 in rotation, for example two rotation drive rollers 20, 22. One of the rotation drive rollers 20 of the molding strip 12 can act as a molding support 24.

[0168] The molding support 24 comprises a molding face 26 intended to come into contact with the internal face 14 of the molding strip 12. The internal face 14 of the molding strip 12 is in contact with the rotational drive rollers 20 of the molding strip 12.

[0169] The molding apparatus 10 also comprises a device 28 for dispensing the plastic material 30 into the cavities 18 of the molding strip 12. In [Fig.l], the device 28 for dispensing a material, for example a plastic material 30 (namely the mixture of the first thermoplastic material and the second material), is arranged on the side of the external face 16 of the molding strip 12, opposite the molding support 26, that is to say that the plastic material 30 is dispensed into the cavities 18 of the molding strip when the internal face 14 of the molding strip 12 is in abutment against the molding face 26 of the molding support 24.

[0170] For example, the dispensing device 28 may be a plastic injection head. The plastic injection head comprises an opening whose width in the transverse direction is less than or equal to the width in the transverse direction of the molding strip 12.

[0171] In [Fig.l], the distribution device 28 is arranged at a certain distance from the external face 16 of the molding strip 12 so as to form an air gap 32 between the molding strip 12 and the distribution device 28.

[0172] When dispensing the plastic material 30 into the cavities 18 of the molding strip 12, a base 34 is also formed on the outer face 16 of the molding strip 12, so as to form, once demolded, a ribbon 36 comprising a base 34 on which a plurality of retaining elements 38 or a plurality of retaining element preforms is formed.

[0173] The molding apparatus 10 also includes a stripping roller 40. The stripping roller 40 may, for example, be configured to separate the base 34 of the ribbon 36 from the molding strip 12 under the effect of the tension of the ribbon 36 and its change of direction. The stripping roller 40 may be a suction roller or include a rubber coating.

[0174] It will be noted that the molding apparatus 10 may also comprise a device for removing excess plastic material, such as a scraper 42 arranged, in the example of [Fig. 1], on the side of the internal face 14 of the molding strip 12 and after the molding support 24, in the direction of travel of the molding strip 12. It is therefore understood that this scraper 42 is arranged after the distribution device 28.

[0175] The compositions of Examples 1 to 5 and Comparative Examples 1 to 3 were made and the retainers were formed in the molding apparatus 10.

[0176] It is understood that the molding apparatus 10 is given by way of example. Other apparatus may be used to form retainers from the compositions of Examples 1 to 5 and Comparative Examples 1 to 3.

[0177] By way of non-limiting example, [Fig. 2] shows the method 100 for manufacturing the retaining device. The method 100 comprises a step 130 of providing the first thermoplastic material 110 and the second material 120, a step 140 of mixing the first thermoplastic material 110 and the second material 120 and a step 150 of forming the retaining device from the mixture of the first thermoplastic material and the second material.

[0178] The mixture of the first thermoplastic material and the second material is represented in [Fig.l] by the plastic material 30 coming out of the dispensing device 28.

[0179] Between the mixing step 140 and the forming step 150, the mixture of the first thermoplastic material and the second material can be conditioned 160 to transport the mixture and, once the mixture of the first thermoplastic material and the second material has arrived at its destination, the mixture of the first thermoplastic material and the second material can be unconditioned 170 and the forming step 150 can be carried out.

[0180] Alternatively, the mixing of the first thermoplastic material and the second material can be done in-line, that is to say that the step 130 of supplying the first thermoplastic material 110 and the second material 120, and the step 140 of mixing the first thermoplastic material 110 and the second material 120 is carried out in equipment directly connected to the dispensing device 28, for example.

[0181] Figures 3 and 4 are partial perspective views of two retaining devices 50.

[0182] In Figures 3 and 4, the elements in common are identified by identical numerical references.

[0183] Also shown, by way of non-limiting example, are the directions MD and CD.

[0184] The retaining device 50 comprises a base 52 having an upper face and a lower face and a plurality of retaining elements 54 extending from the upper face of the base 52. In Figures 3 and 4, a single retaining element 54 has been shown.

[0185] The retaining element comprises a rod 56, extending from the upper face of the base 52, surmounted by a head 58. The rod comprises a lower end connected to the base 52, and an opposite upper end from which the head 58 extends.

[0186] The head 58 may have at least one portion extending beyond the upper end of the rod, in order to define a gripping portion or lobe adapted to engage fibers and / or loops and / or complementary retaining elements to produce a self-gripping connection. The head 58 thus typically has a maximum section having a surface strictly greater than the surface of the upper end of the rod 56.

[0187] The thicknesses and heights are measured in a direction perpendicular to the upper face and / or the lower face of the base, for example perpendicular to the plane formed by the MD and CD directions and the widths are measured in a plane parallel to the upper face and / or the lower face, for example in a plane parallel to the plane formed by the MD and CD directions.

[0188] The base 52 has a thickness E52 measured between the upper face and the lower face of the base 52; the retaining element 54 has a height H54; the rod 56 has a height H56 and a width L56; the head has a thickness E58 and two widths L58 and 158. The width L58 is the maximum width of the head 58.

[0189] In [Fig.4], the hanging height Ha has been shown.

[0190] Table 1 presents the results of the peel resistance measurements and shear strength values ​​for hook retainers. Peel strength and shear strength values ​​are reported for retainers with a width of 15 mm.

[0191] [Tables 1] Shaping of preforms and / or retaining elements Peel strength (N) Shear strength (N) Ex 1 Yes 5.1 + / - 0.7 72 + / - 7 Ex 2 Yes 3.7 + / - 0.6 Not available Ex 3 Yes 2.8 + / - 1.2 60 + / - 16 Ex 4 Yes 2.1 + / - 1.0 47 + / - 16 Ex 5 Yes 2.2 + / - 1.0 63 + / - 9 Comp 1 Yes 3.5 + / - 0.5 68 + / - 4 Comp 2 Yes 3.9 + / - 0.7 63 + / - 6 Comp 3 No - -

[0192] The peel strength and shear strength values ​​for Comparative Example 3 could not be measured. This is because this mixture cannot be molded. The molding of the retainer is partial so that the molding cavities are not completely filled and / or the demolding of the retainers and / or preforms is very difficult. It is therefore not possible to obtain satisfactory retainers and / or preforms.

[0193] The values ​​of Examples 1 and 2 are to be compared with the values ​​of Comparative Examples 1 and 2. The values ​​of Examples 3-5 are to be compared with the values ​​of Comparative Example 3.

[0194] For Examples 1 and 2 and Comparative Examples 1 and 2, the peel strength and shear strength measurements were carried out on retainers having a width of 15 mm.

[0195] For Example 3, the peel strength and shear strength measurements were carried out on retainers having a width of 19 mm. The peel strength value is 3.6 + / - 1.5 N, i.e. a value of 2.8 + / - 1.2 N relative to a width of 15 mm and the shear strength value is 76 + / - 20 N, i.e. a value of 60 + / - 16 N relative to a width of 15 mm.

[0196] For Example 4, the peel strength and shear strength measurements were carried out on retainers having a width of 19 mm. The peel strength value is 2.6 + / - 1.2 N, i.e. a value of 2.1 + / - 1.0 N relative to a width of 15 mm and the shear strength value is 60 + / - 20 N, i.e. a value of 47 + / - 16 N relative to a width of 15 mm.

[0197] For Example 5, the peel strength and shear strength measurements were carried out on retainers having a width of 22 mm. The peel strength value is 3.2 + / - 1.4 N, i.e. a value of 2.2 + / - 1.0 N relative to a width of 15 mm and the shear strength value is 93 + / - 13 N, i.e. a value of 63 + / - 9 N ​​relative to a width of 15 mm.

[0198] As can be seen, the peel strength values ​​of Examples 1 and 2 are similar to, or even higher than, the values ​​of Comparative Examples 1 and 2. The same is true of the shear strength values.

[0199] It will be noted that Examples 3 to 5 should be compared with Comparative Example 3. However, the peel strength values ​​of Examples 3 to 5, although lower than the values ​​of Comparative Examples 1 and 2, are satisfactory, particularly for the intended application. The shear strength values ​​are lower, or even similar, to the values ​​of Comparative Examples 1 and 2.

[0200] Examples 1 to 5 make it possible to obtain satisfactory retaining devices which are compostable in an industrial environment, for example according to standard EN 13432:2000, or which are based on compostable materials, and / or derived from biomass, for example according to standard EN 16785-1:2016 and / or standard ASTM D 6866:2022, and which can always be taken into account at the end of their life in industrial composting and / or recycling channels.

[0201] Although the present disclosure has been described with reference to a specific exemplary embodiment, it is obvious that various modifications and changes may be made to these examples without departing from the general scope of the invention as defined by the claims. Furthermore, individual features of the various embodiments recited may be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

Claims

Claims

1. Retaining device (50), comprising: - a base (52) extending in a longitudinal direction having an upper face and a lower face, - a plurality of retaining elements (54) extending from the upper face of the base (52), each retaining element (54) comprising a rod (56), the retaining device (50) comprising predominantly, in mass percentage, in particular consisting of being formed from, a first thermoplastic material based on a first polyester having a flexural modulus greater than or equal to 200 MPa and less than or equal to 4500 MPa and a second material comprising a second thermoplastic material based on a second polyester having a flexural modulus different by at least 10% and / or at least 100 MPa from the flexural modulus of the first thermoplastic material.

2. Retaining device (50) according to claim 1, in which the second material comprises a non-thermoplastic material present at a content strictly greater than 1% by mass of the total composition of the retaining device, in particular greater than or equal to 1.1%, in particular greater than or equal to 1.2%.

3. A retaining device (50) according to any one of claims 1 or 2, wherein the second material comprises a mineral and / or vegetable filler whose content is less than or equal to 30% by mass of the total composition of the retaining device.

4. A retaining device (50) according to any one of claims 1 to 3, wherein the first thermoplastic material has a flexural modulus greater than or equal to 800 MPa and less than or equal to 4000 MPa.

5. A retaining device (50) according to any one of claims 1 to 4, wherein the first thermoplastic material has a number average molecular weight greater than or equal to 20,000 g / mol.

6. The retaining device (50) of claim 5, wherein the second material comprises a non-thermoplastic material having a molecular weight at least 10% lower than the number average molecular weight of the first thermoplastic material and / or less than or equal to 15000 g / mol.

7. A retaining device (50) according to any one of claims 1 to 6, wherein the first thermoplastic material has an MFR greater than or equal to 1 g / 10 min, in particular greater than or equal to 10 g / 10 min, in particular greater than or equal to 15 g / 10 min and / or less than or equal to 300 g / 10 min, in particular less than or equal to 200 g / 10 min, in particular less than or equal to 170 g / 10 min.

8. A retaining device (50) according to claim 7, wherein the second material, in particular the second thermoplastic material, has an MFR different by at least 10% and / or at least 5 g / 10 min from the MFR of the first thermoplastic material.

9. A retaining device (50) according to any one of claims 2 to 8, wherein the non-thermoplastic material has a molecular weight greater than or equal to 250 g / mol, in particular greater than or equal to 300 g / mol and / or less than or equal to 19000 g / mol, in particular less than or equal to 15000 g / mol, in particular less than or equal to 10000 g / mol, more particularly less than or equal to 800 g / mol and in certain cases less than or equal to 550 g / mol.

10. A retaining device (50) according to any one of claims 2 to 9, wherein the second material comprises a non-thermoplastic material present at a content greater than or equal to 1.5% by mass of the total composition of the retaining device, in particular greater than or equal to 2%, in particular greater than or equal to 5%, and / or less than 2 or equal to 5% by mass of the total composition of the retaining device, in particular less than or equal to 20%, in particular less than or equal to 18%, more precisely less than or equal to 15%, in certain cases less than or equal to 13%.

11. Retaining device (50) according to any one of claims 1 to 10, wherein the ratio of the mass percentage of the second material to the first thermoplastic material is greater than or equal to 0.02, in particular greater than or equal to 0.05, in particular greater than or equal to 0.1 and / or less than or equal to 0.30, in particular less than or equal to 0.25, in particular less than or equal to 0.

24.

12. A retaining device (50) according to any one of claims 1 to 11, the ratio of the mass percentage of the second thermoplastic material, for example of the second polyester of the second thermoplastic material, to the first thermoplastic material, for example of the first polyester of the first thermoplastic material, may be greater than or equal to 0.20, in particular greater than or equal to 0.30, in particular greater than or equal to 0.35 and / or less than or equal to 0.70, in particular less than or equal to 0.60, in particular less than or equal to 0.

55.

13. Retaining device (50) according to any one of claims 1 to 12, in which each retaining element (54) comprises a rod (56) surmounted by a head (58), in a first direction, for example in the MD direction, the rod (56) having a proximal portion arranged on the side of the base (52) and a distal portion arranged on the side of the head (58), the width of the rod at its proximal portion may be greater than the width of the rod at its distal portion.

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