FR3092518A1 - Improved processing method for a tape having gripping elements. - Google Patents

Abstract

Improved processing method for a tape having gripping elements. A method of forming a hook retainer, wherein a molding device (1, 61) comprising a plurality of cavities (13, 64) defining gripping elements is provided, a molding material is dispensed on an outer face of the molding device (1, 61) by a material distribution means (3) arranged opposite said molding device (1), the step of distributing the molding material being carried out so as to fill the cavities (13) ) of molding material in order to form a tape (100) comprising a base (51) and elements or preforms projecting from a first face of said base (51), a surface treatment is applied, for example a plasma treatment , more particularly plasma at atmospheric pressure on a second face of the base (51) opposite the first face of the base (51), said elements being held in the cavities (13, 64). Figure for the abstract: Fig. 1.

Description

Improved processing method for a tape having gripping elements.

This presentation relates to the field of closure devices, and more specifically relates to hook closure systems as well as the associated manufacturing methods and apparatus.

Closing devices with hooks are well known and used in many fields of application, leading in fact to the production of multiple shapes of hooks or more generally to multiple shapes of retaining elements intended to cooperate mutually or with elements complementary such as loops.

A recurring problem concerns the attachment of closure devices to a product. Fixing is commonly achieved by means of glue. On conventional manufacturing lines, corona-type treatments are used on the rear face of the closure devices in order to obtain a surface energy greater than 50 Dyn (measured with an ink pen) one year after the treatment, and thus ensure good adhesion of the glue. Such treatments work for production lines having relatively low running speeds, less than 20 meters per minute or even treatments carried out statically. However, corona treatments are not applicable for manufacturing lines with a high manufacturing speed, for example of the order of 80 to 150 meters per minute, the product running speed then being too high to allow corona treatment. to be effective which the person skilled in the art cannot compensate for by increasing the processing power without obtaining a deformation of the treated product.

This presentation thus aims to answer at least partially to this problem.

This presentation relates to a method of forming a hook retaining device, in which a molding device is provided comprising a plurality of cavities defining shapes or preforms of gripping elements, said molding device being driven in movement, distributes a molding material on an outer face of the molding device by means of distributing the material arranged facing said molding device, the step of distributing the molding material being carried out so as to fill the cavities with molding material in order to form a ribbon comprising a base and elements or preforms protruding from a first face of said base formed by the plastic material in the cavities of the molding device, a surface treatment, for example a plasma treatment, is applied plus particularly an atmospheric pressure plasma, on a second face of the base opposite the first face of the base, said shapes or p reforms of gripping elements being maintained in the cavities of the molding device, then the strip is unmolded.

According to one example, the surface treatment is a plasma treatment at atmospheric pressure, and in which said surface treatment is applied to the second face of the base while the latter has a surface temperature higher than the bending temperature under loads of the molding material, for example above 60°C.

According to one example, the molding material is a thermoplastic material, for example predominantly polypropylene or polyethylene.

According to one example, the surface treatment is a plasma treatment at atmospheric pressure, and in which the application of the plasma at atmospheric pressure is carried out by means of at least one plasma torch, the distance between the plasma torch and the second face of the base being between 2 mm and 20 mm, more particularly between 5 mm and 10 mm.

According to one example, the plasma at atmospheric pressure is generated by means of a source of compressed air at a pressure of between 3 and 10 bars.

According to one example, the step of dispensing the molding material forms a base having a thickness between 10 micrometers and 700 micrometers.

According to one example, the molding device drives the molding material at a speed of movement greater than 20 meters per minute, more particularly a speed of movement greater than 50 meters per minute.

This disclosure also 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, in which the underside of the base has a surface energy whose polar component is greater than 5 mj/m² and/or whose ratio of the polar component to the dispersive component is greater than or equal to 20% with a droplet tensiometer .

According to one example, the underside of the base has a surface tension greater than 50 Dyn measured with a Dynes STTS pen.

According to one example, the lower face of the base has a ratio of chemical elements Oxygen/Carbon greater than 0.010, more particularly greater than 0.015.

The invention and its advantages will be better understood on reading the detailed description given below of various embodiments of the invention given by way of non-limiting examples. This description refers to the pages of appended figures, on which:

FIG. 1 represents an example of apparatus according to one aspect of the invention.

Figure 2 is a graph illustrating the effect of atmospheric pressure plasma treatment according to one aspect of the invention.

Figure 3 is a graph illustrating the effect of atmospheric pressure plasma treatment according to one aspect of the invention.

Figure 4 is a graph illustrating the effect of atmospheric pressure plasma treatment according to one aspect of the invention.

Figure 5 is a graph illustrating the effect of atmospheric pressure plasma treatment according to one aspect of the invention.

FIG. 6 presents another example of apparatus allowing the implementation of the invention.

FIG. 7 presents another example of apparatus allowing the implementation of the invention.

In all the figures, the elements in common are designated by identical reference numerals.

Figure 1 shows an example of apparatus for implementing a method according to one aspect of the invention.

This figure shows an apparatus comprising a molding strip 1 positioned on rotation drive means 2 comprising here two rollers 21 and 22, a material distribution means 3 adapted to carry out an injection of molding material, for example plastic and/or elastic.

The assembly formed by the molding strip 1 and the rotation drive means 2 thus forms a molding device.

The example illustrated comprising two rollers 21 and 22 is not limiting, the number and arrangement of the roller(s) may vary in particular in order to adapt to the length of the molding strip 1 and to the different positions of the equipment. One could for example use three rollers or even just one so that the molding strip is arranged on the periphery of the single roller. In particular, only one of the two rollers can be driven in rotation by motorized means, for example the roller 21, the other roller 22 being free, that is to say without motorized means, and driven in rotation via the molding strip , itself driven by roller 21.

The molding strip 1 as presented comprises an inner face 11 and an outer face 12, the inner face 11 being in contact with the rotation drive means 2.

The material distribution means 3 is arranged so as to inject molding material onto the outer face 12 of the molding strip 1. The molding material is typically a thermoplastic material, for example composed of at least 30% or at least 50% polypropylene (homopolymer, copolymer, Atactic (PPa), Syndiotactic (PPs), Isotactic (PPi)) or polyethylene. The molding material can be, for example, a material from the following list: Polypropylene, Polyethylene, a sequenced or random PP/PE (Polypropylene/Polyethylene) copolymer, a PET (Polyethylene terephthalate)/PBT (Polybutylene terephthalate), a PLA (polylactic acid)/PHA (polyhydroxyalkanoate)/PBAT (polybutylene adipate terephthalate) or else a PA (polyamide), for example of the PA-6.6/PA-6.10/PA-12 type.

More precisely, the material distribution means 3 is arranged opposite the molding strip 1, spaced from the molding strip 1 so as to define an air gap e indicated in FIG. 1. The reference A marks the limit of the material injected on the outer face 12 of the molding strip 1, corresponding to the rear edge of the material injected on the molding strip 1 with respect to the direction of movement of the molding strip 1.

The molding strip 1 is provided with a plurality of cavities 13 allowing the production of hooks of the hook retainer.

More generally, the rollers 21 and 22 as well as the molding strip 1 form a molding device having a plurality of cavities defining shapes or preforms of gripping elements, driven at a displacement speed greater than or equal to 20 meters per minute, typically between 50 and 150 meters per minute. Preferably, the material distribution means 3 is typically arranged so as to continuously inject molding material into the molding strip. In other words, the surface treatment is applied continuously to the face of the base opposite the face of the base comprising the projecting elements or preforms and before the material forming the strip 100 of the retaining device is completely cooled.

The material distribution means 3 is typically arranged so as to carry out the injection of molding material into the molding strip 1, so as to carry out a filling of the molding strip 1 in a section of the molding strip 1 where the latter bears against a drive roller, in this case the drive roller 21 in the example shown in Figure 1. The drive roller then forms a bottom for the cavities 13. The material is typically injected at a temperature of the order of 210°C.

In the case where the injection of molding material is carried out while the molding strip 1 is not resting against a drive roller, the material distribution means 3 can then comprise a base arranged on the other side of the molding strip 1, so that the internal face 11 of the molding strip 1 bears against the base when the injection of material is carried out, the base then forming a bottom for the cavities 13 of the molding strip molding 1. An element such as a blade or a squeegee can then remove any excess material protruding from the internal face 11 of the molding strip 1.

The injection of molding material into the molding strip 1 by the material distribution means 3 makes it possible to form a base 51 and a plurality of elements or preforms each comprising a rod 52 and a head 53, the assembly forming thus a ribbon 100.

The elements comprising the rods 52 and the heads 53 are typically first preforms which will then be subjected to a forming step for the production of the hooks.

The base 51 thus formed typically has a thickness comprised between 10 micrometers and 700 micrometers, or more precisely between 40 micrometers and 200 micrometers.

A longitudinal direction is defined relative to the direction of movement of the strip 100, this longitudinal direction being parallel to the direction of movement of the strip 100, symbolized by arrows in FIG. 1. This longitudinal direction is commonly referred to as the "machine direction". or “machine direction” or “MD” according to the name in English.

A transverse direction, or "cross direction" or "CD" as it is called in English, is also defined, corresponding to a direction perpendicular to the longitudinal direction, and extending parallel to a flat face of the tape 100.

The base 51 has an upper face 511 and a lower face 512 which are typically substantially parallel, the upper face 511 being the face provided with the hooks and/or preforms.

In the example shown, the stripping is carried out by means of a stripping roller 6, typically configured so as to separate the base 51 of the strip 100 from the molding strip 1 under the effect of the tension of the strip and its change of direction. The stripping roller can be equipped with a means of suction and/or a surface with a high coefficient of friction, such as a rubber coating, in order to improve traction and limit slippage. This stripping roller 6 can be motorized and have a tangential speed slightly higher than that of the molding strip 1.

The apparatus also comprises an atmospheric pressure plasma source 4, positioned facing the outer face 12 of the molding strip 1. The atmospheric pressure plasma source 4 is positioned between the material distribution means 3 and the roller release 6.

In FIG. 1, the atmospheric pressure plasma source 4 is represented as a plasma torch arranged opposite the roller 22 such that the treated surface of the base 51 has a curvature. In a variant embodiment, the plasma torch can be positioned opposite the base 51 when the latter is not curved or straight, for example, as shown in dotted lines at two locations in FIG. 1. In a variant embodiment, several plasma torches can be used, in particular for high speeds (100, 150, 200 m/min), and in particular on a straight part of the base. In a variant embodiment not shown, the plasma torch can be inclined with respect to the normal to the base 51 so as to facilitate the evacuation of the gases given off, in particular inclined at an angle less than 45° with respect to the normal to the based. As a variant embodiment, only part of the surface of the base 51 can be treated, for example a width less than 90% (or 80%) of the width of the base 51. The treatment can be carried out locally with, for example, the use of a mask.

The atmospheric pressure plasma source 4 is suitable for applying an atmospheric pressure plasma to the lower face 512 of the base 51 of the ribbon 100 formed by the injection of material.

The plasma at atmospheric pressure is applied to the lower face 512 of the base 51 of the strip 100 before its demoulding, that is to say while the elements or preforms are held in the cavities of the molding strip 1.

The application of a plasma at atmospheric pressure on the lower face 512 of the base 51 makes it possible to increase its surface energy due to its oxidation and the formation of chemical species. An advantage of carrying out the plasma treatment upstream of demolding is that the elements or preforms are held in the cavities of the molding strip 1, which prevents or limits the deformation resulting from the plasma treatment, and in particular makes it possible to prevent shrinkage of the material of the base 51, and thus to maintain the flatness of the lower face 512 of the base 51.

The atmospheric pressure plasma source 4 comprises for example two plasma torches positioned successively according to the movement of the ribbon 100, which can be powered by the same electric generator delivering a power of the order of 1000 W, as well as an air source compressed air, for example a compressed air generator or a connection to a compressed air network at a pressure of 2.5 bar.

Each plasma torch comprises a head whose output end is typically positioned at a distance of between 5 mm and 60 mm relative to the lower face 512 of the base 51, more particularly between 5 mm and 40 mm relative to the lower face 512 of the base 51, between 5 mm and 10 mm with respect to the lower face 512 of the base 51. The head of the plasma torch typically has a rectangular-shaped outlet nozzle whose length is between 8 and 15 mm, or typically equal to 11 mm, and having a width less than 1 mm.

The plasma source can for example be supplied with compressed air (atmospheric composition), or with Argon, possibly mixed with oxygen or nitrogen.

The positioning of the atmospheric pressure plasma source 4 can vary; it is more generally positioned between the material distribution means 3 and the stripping means (here the stripping roller 6).

The atmospheric pressure plasma source 4 can be positioned so as to apply an atmospheric pressure plasma over all or part of the width of the lower face 512 of the base 51 (the width being in the transverse direction with respect to the displacement of the ribbon 100).

Advantageously, the atmospheric pressure plasma source 4 is positioned so as to apply an atmospheric pressure plasma to the lower face 512 of the base 51 while the lower face 512 is still hot, and typically has a higher surface temperature. at the bending temperature under loads, for example greater than 60° C. (for a base 51 formed from a material based on polypropylene), or for example equal to or of the order of 65° C.

The atmospheric pressure plasma source 4 is thus typically positioned according to the injection temperature of the molding material and the cooling rate of the latter.

The atmospheric pressure plasma source is typically configured such that the atmospheric pressure plasma is applied only to a predetermined area of the underside 512 of the base 51, and not to the edges of the base 51 or to the tooling.

The atmospheric pressure plasma source 4 can be associated with an element such as a mask in order to delimit the surface of the lower face 512 of the base 51 which is subjected to the atmospheric pressure plasma treatment. Alternatively, the atmospheric pressure plasma source 4 may have nozzles having a specific shape in order to treat only a predetermined zone of the lower face 512 of the base 51 and/or guarantee a determined distribution of the flux over the width treatment.

In order to quantify the effect of the treatment by application of a plasma at atmospheric pressure, the surface tension is measured on the lower face 512 of the base 51. Under the conditions indicated above (2 successive plasma torches positioned at a distance of 6 mm from the lower surface 512 of the base 51, powered by a single 1000W electric generator and connected to a compressed air network at a pressure of 5 bars), the surface tension measured by means of test inks immediately after application plasma is greater than 69 Dyn (measured with a Dynes STTS pen). The measurements made using the Dynes STTS pen consist of making a stroke with a pen having a predetermined Dyn level, and observing whether the stroke made holds in place for at least 2 seconds without being absorbed into droplets, in which case the Dyn value of the pen is reached. By performing the measurement again on the same sample 5 months after applying the plasma, the measured value remains above 69 Dyn (measured with a Dynes STTS pen), knowing that the desired value is 50 Dyn (measured with a Dynes STTS). The surface tension without the plasma treatment is 32 Dyn (measured with a Dynes STTS pen) or less than 32 Dyn (measured with a Dynes STTS pen).

Such a surface tension, after the application of the plasma, makes it possible to improve the hold of an adhesive on the lower face 512 of the base 51, and thus makes it possible to improve the gluing steps as well as the mechanical strength of the final product.

Other methods of measuring surface tension make it possible to specify the effect of plasma treatment at atmospheric pressure as carried out.

FIGS. 2 to 5 show several graphs representing the values obtained.

Figure 2 shows surface energy measurements (in mN/m) obtained by a droplet tensiometer. For example with a DGD-DS Tensiometer marketed by the company GBX.

The measurement protocol is as follows: contact angles are measured on 5 drops of three test liquids: diiodomethane, ethylene glycol and deionized water (which ensures reproducibility). The measurement of the contact angles is carried out 3 to 5 seconds after the liquid has been deposited on the surface. Measurements are taken on 3 areas of analysis, in order to ensure the homogeneity of the analyzed surface. Surface energies are calculated from the two-component Owens-Wendt model. The measurements are obtained with an accuracy of +/- 0.5°.

A distinction is made between the dispersive component (hatched area) and the polar component (area with dots) on the various measurements. The different measures correspond to the following cases:

II-1: sample not subjected to plasma treatment.

II-2: sample subjected to plasma treatment at atmospheric pressure, 1 week after the treatment.

II-3: sample subjected to plasma treatment at atmospheric pressure, 1 month after the treatment.

II-4: sample subjected to plasma treatment at atmospheric pressure, 3 months after the treatment.

II-5: sample subjected to plasma treatment at atmospheric pressure, 6 months after the treatment.

II-6: sample subjected to plasma treatment at atmospheric pressure, 9 months after the treatment.

II-7: sample subjected to plasma treatment at atmospheric pressure, 12 months after the treatment.

This figure 2 makes it possible to illustrate the fact that the treatment by plasma at atmospheric pressure generates a polar component which is almost zero or negligible in the case of an untreated sample, and also the fact that the surface energy remains substantially constant. over time after plasma application.

FIG. 3 represents measurements of surface tension (or energy) (in mN/m) obtained by a droplet tensiometer after sizing and desizing operations by dissolving the glue and soaking in ethyl acetate.

The protocol for dissolving the glue and soaking in ethyl acetate is as follows:

A beaker is filled with a solvent (ethyl acetate or gasoline C or acetone depending on the glue to be removed), in sufficient quantity for the product to be completely covered.

The sample is placed in the beaker.

Stir the contents of the beaker with a spatula.

Leave to stand for 10 minutes, having carried out several agitations of the contents at 0, 5 and 10 minutes.

If necessary, the adhesive layer is removed by scraping with a spatula,

If glue remains after 10 minutes, the protocol is repeated by renewing the solvent.

A distinction is made between the dispersive component (hatched area) and the polar component (area with dots) on the various measurements. The different measures correspond to the following cases:

III-1: sample according to the state of the art (according to the teachings of document WO2010130886_A1_APLIX SA "MONT"), manufactured on a line having a reduced manufacturing speed, subjected to corona treatment, then to a gluing operation , to an operation of desizing and soaking in ethyl acetate.

III-2: sample (according to the teachings of document WO2017187096_A1 APLIX_ “STaMP”) not subjected to plasma treatment (similar to the sample of measurement II-1).

III-3: sample (according to the teachings of document WO2017187096_A1 APLIX_ “STaMP”) subjected to plasma treatment at atmospheric pressure.

III-4: sample (according to the teachings of document WO2017187096_A1 APLIX_ “STaMP”) subjected to plasma treatment at atmospheric pressure and soaking in ethyl acetate.

III-5: sample (according to the teachings of document WO2017187096_A1 APLIX_ “STaMP”) subjected to a plasma treatment at atmospheric pressure, to a sizing operation, then to desizing and soaking in ethyl acetate.

The graphs in Figure 3 thus illustrate that plasma treatment at atmospheric pressure makes it possible to obtain a higher surface tension than that obtained via corona treatments on low-speed production lines, and that this surface tension is retained after the operations of sizing, desizing and soaking in ethyl acetate.

Figure 4 shows the different samples already analyzed in the context of Figure 2, but here performs an analysis of the chemical elements on the surface by means of an X-ray photoelectron spectrometry process (or XPS process).

The measurements are taken using a THERMO K-aplha+ system with an Al K source, according to the following protocol:

Detection angle: 90°,

Analysis depth less than 10 nm (about 3 nm),

Analyzable depth of the order of a few tenths of a µm,

Diameter of the analyzed area: 400 µm,

Detectable elements: all, except H and He,

Detection threshold: 0.1% to 0.5% atomic,

The attributions of the chemical forms are then carried out according to the “Handbook of X-ray photoelectron spectroscopy” (PHI, J. Moulder and co.).

We distinguish on the different measurements Carbon (loose hatched area), Oxygen (area with dots), and Nitrogen (tightened hatched area). The different measures correspond to the following cases:

IV-1: sample (according to the teachings of document WO2017187096_A1 APLIX_“STaMP”) not subjected to plasma treatment.

IV -2: sample (according to the teachings of document WO2017187096_A1 APLIX_“STaMP”) subjected to a plasma treatment at atmospheric pressure, 1 week after the treatment.

IV -3: sample (according to the teachings of document WO2017187096_A1 APLIX_ “STaMP”) subjected to a plasma treatment at atmospheric pressure, 1 month after the treatment.

IV -4: sample (according to the teachings of document WO2017187096_A1 APLIX_ “STaMP”) subjected to a plasma treatment at atmospheric pressure, 3 months after the treatment.

IV -5: sample (according to the teachings of document WO2017187096_A1 APLIX_ “STaMP”) subjected to a plasma treatment at atmospheric pressure, 6 months after the treatment.

IV -6: sample (according to the teachings of document WO2017187096_A1 APLIX_ “STaMP”) subjected to plasma treatment at atmospheric pressure, 9 months after the treatment.

IV -7: sample (according to the teachings of the document WO2017187096_A1 APLIX_ “STaMP”) subjected to a plasma treatment at atmospheric pressure, 12 months after the treatment.

It can be seen that the treatment by plasma at atmospheric pressure significantly modifies the distribution of the chemical elements on the surface compared to an untreated sample or compared to a sample subjected to a corona treatment, and that the distribution of the various elements persists over time. Thus, the treated surface has a greater and more stable adhesive adhesion capacity over time. A product treated in this way can be stored longer before coating the treated surface with glue, can more easily withstand the various variations in temperature and/or humidity associated with transport, for example transport by container. Surprisingly, the performance drop is reduced to zero. The heat treatment of the surface of the base 51 constrained in the molding strip 1 makes it possible to limit aging and to reduce the phenomenon of reburial of the functions (oxygen, nitrogen, or other) which are present on the surface.

Figure 5 shows the various samples already analyzed in the context of Figure 3, but an analysis of the chemical elements on the surface is carried out here by means of an X photoelectron spectrometry method (or XPS method) as already detailed previously in reference in Figure 4.

In Figure 5, the different measurements are Carbon (loose hatched area), Oxygen (area with dots), and Nitrogen (tightened hatched area). The different measures correspond to the following cases:

V-1: sample according to the state of the art, manufactured on a line having a reduced manufacturing speed, subjected to a corona treatment, then to a sizing operation, a desizing operation and soaking in water 'ethyl acetate.

V-2: sample (according to the teachings of document WO2017187096_A1 APLIX_“STaMP”) not subjected to plasma treatment.

V-3: sample (according to the teachings of document WO2017187096_A1 APLIX_ “STaMP”) subjected to plasma treatment at atmospheric pressure.

V-4: sample (according to the teachings of document WO2017187096_A1 APLIX_ “STaMP”) subjected to plasma treatment at atmospheric pressure and soaking in ethyl acetate.

V-5: sample (according to the teachings of document WO2017187096_A1 APLIX_ “STaMP”) subjected to plasma treatment at atmospheric pressure, to a sizing operation, then to desizing and soaking in ethyl acetate.

As for FIG. 4, it can be seen that the treatment by plasma at atmospheric pressure significantly modifies the distribution of the chemical elements on the surface compared to an untreated sample or compared to a sample subjected to a corona treatment. The sizing, desizing and quenching operations in ethyl acetate significantly modify the distribution of the chemical elements, which however remains distinct compared to an untreated sample and compared to a sample subjected to corona treatment. The properties resulting from the surface treatment according to the invention are thus retained even after the operations of sizing, desizing and then quenching in ethyl acetate. It can be seen from the results listed in Tables 1 that for the products treated according to the invention, the ratio of the chemical elements Oxygen / Carbon is greater than 0.010, more particularly greater than 0.015, whereas for the products of the In the prior art, ratios of the chemical elements Oxygen/Carbon equal to respectively 0.0040, 0.0037 or 0.0653 have been obtained. In addition, the ratios of the chemical elements Oxygen / Carbon obtained for the invention are stable over time, in particular at 1 month, 2 months, 3 months, 6 months and 9 months.

The substrates are as follows:

I-1: sample according to the teachings of document WO2017187096_A1 APLIX_ “STaMP” not subjected to plasma treatment.

I-2: sample according to the teachings of document WO2017187096_A1 APLIX_ "STaMP" not subjected to plasma treatment and soaked in ethyl acetate.

I-3 to I-7 and I-11: samples according to the teachings of document WO2017187096_A1 APLIX_ “STaMP” subjected to plasma treatment at atmospheric pressure.

I-8: sample according to the teachings of document WO2017187096_A1 APLIX_ "STaMP" subjected to plasma treatment and soaked in ethyl acetate.

I-9: sample according to the teachings of document WO2010130886_A1_APLIX SA "MONT", manufactured on a line having a reduced manufacturing speed, not subjected to plasma treatment at atmospheric pressure but subjected to corona treatment and to a gluing operation , then desizing by soaking in ethyl acetate.

I-10: sample according to the teachings of document WO2017187096_A1 APLIX_ "STaMP" subjected to plasma treatment at atmospheric pressure, to a sizing operation, then to desizing by soaking in ethyl acetate.

Note that for samples I-1, I-2 and I-9 the aging time is not mentioned insofar as this data is not significant in the absence of plasma treatment.

Figures 6 and 7 show two other examples of apparatus for implementing a method according to one aspect of the invention.

Figure 6 shows an apparatus comprising a forming roller 61 forming a molding device, positioned between a molding roller 62 and a stripping roller 6.

The forming roller 61 has a plurality of cavities 64 opening onto its outer periphery, and defining shapes or preforms of retaining elements such as hooks. The forming roller 61 here forms the molding device 1 and the drive device 2 as presented above with reference to Figure 1.

The molding roller 62 is positioned opposite the forming roller 61, so as to define an air gap in which a material distribution means 3 injects molding material, which thus makes it possible to form a ribbon 100 comprising a base 51 and forms or preforms of retaining elements, as already described previously with reference to the apparatus presented in FIG. cavities 64 of the forming roll 61, in a manner similar to the stripping roll 6 described with reference to FIG. 1. In the example shown, the molding roll 62 and the stripping roll 6 are positioned on either side other of the forming roller 61, and are therefore diametrically opposed, and the ribbon 100 is held on the forming roller 61 for approximately a half-turn of this forming roller 61. It is however understood that this configuration is not limiting , and that the relative positioning of the various rollers can be modified.

The atmospheric pressure plasma source 4 is here positioned facing the central roller 61, between the injection of the molding material and the stripping of the strip 100 by the stripping roller 6.

Figure 7 shows another variant of such an apparatus.

In this variant, the stripping roller 6 is positioned so that the strip 100 travels around a quarter turn between its molding and its stripping. The atmospheric pressure plasma source 4 is here positioned substantially halfway between the molding roll 62 and the stripping roll 6.

The operation remains identical to the operation already described with reference to the preceding figures.

The process as proposed makes it possible to obtain a product having a high surface tension on its underside, while maintaining a high manufacturing speed.

Note that the central roller 61 shown in Figures 6 and / or 7 is a roller in which molding cavities are machined for inverted J-shaped hooks. It is understood that this example is not limiting, and that the hooks and/or preforms and/or heads formed can be of any shape, for example with a rod and/or a head of square, rectangle, hexagonal, cylindrical, hyperboloid or as described with reference to Figure 1. In combination or alternatively to the different shapes of rods and / or head of the hooks, and Figures 6 and / or 7, the central roller 61 can be a roller formed of an assembly of discs cut out in such a way as to form molding cavities or else may be a roll having an outer surface on which is attached a molding strip forming a sleeve.

Although the present invention has been described with reference to specific embodiments, it is obvious that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the different illustrated/mentioned embodiments can be combined in additional embodiments. Accordingly, the description and the drawings should be considered in an illustrative rather than restrictive sense.

It is also obvious that all the characteristics described with reference to a method can be transposed, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device can be transposed, alone or in combination, to a method. .

Claims (10)

A method of forming a hook retainer, wherein:
- a molding device (1, 61) is provided comprising a plurality of cavities (13, 64) defining shapes or preforms of gripping elements, said molding device (1, 61) being driven in motion,
- a molding material is distributed on an external face of the molding device (1, 61) by a means of distributing the material (3) arranged facing said molding device (1), the step of distributing the material of molding being carried out so as to fill the cavities (13) with molding material in order to form a strip (100) comprising a base (51) and elements or preforms protruding from a first face of said base (51) formed by the plastic material in the cavities (13, 64) of the molding device (1, 61),
- a surface treatment, for example a plasma treatment, more particularly a plasma at atmospheric pressure, is applied to a second face of the base (51) opposite the first face of the base (51), said shapes or preforms of gripping elements being held in the cavities (13, 64) of the molding device (1, 61),
- the ribbon (100) is unmolded. Method according to claim 1, in which the surface treatment is a plasma treatment at atmospheric pressure, and in which the said surface treatment is applied to the second face of the base (51) while the latter has a surface temperature higher than the bending temperature under loads of the molding material, for example greater than 60°C. Process according to one of Claims 1 or 2, in which the molding material is a thermoplastic material, for example mainly polypropylene or polyethylene. Process according to one of Claims 1 to 3, in which the surface treatment is a plasma treatment at atmospheric pressure, and in which the application of the plasma at atmospheric pressure is carried out by means of at least one plasma torch, the distance between the plasma torch and the second face of the base being between 2 mm and 20 mm, more particularly between 5 mm and 10 mm. Method according to one of Claims 1 to 4, in which the plasma at atmospheric pressure is generated by means of a source of compressed air at a pressure of between 3 and 10 bars. A method according to any of claims 1 to 5, wherein the step of dispensing the molding material forms a base (51) having a thickness between 10 micrometers and 700 micrometers. Method according to one of Claims 1 to 6, in which the molding device drives the molding material at a speed of movement greater than 20 meters per minute, more particularly a speed of movement greater than 50 meters per minute. Restraint device, comprising
- a base (51) extending in a longitudinal direction having an upper face (511) and a lower face (512),
- a plurality of retaining elements extending from the upper face (511) of the base (51),
wherein the underside (512) of the base (51) has a surface energy whose polar component is greater than 5 mj/m² and/or whose ratio of polar component to dispersive component is greater than or equal to 20% with a set-drop tensiometer. Device according to Claim 8, in which the lower face (512) of the base (51) has a surface tension greater than 50 Dyn measured with a Dynes STTS pen. Device according to one of Claims 8 and 9, in which the lower face (512) of the base (51) has a ratio of the chemical elements Oxygen / Carbon greater than 0.010, more particularly greater than 0.015.