EP1729607B1 - Process for creating adhesion elements on a substrate material - Google Patents

Description

The invention relates to a method for producing adhesive elements on a carrier material by using at least one plastic material which is introduced into at least one shaping element, wherein as plastic materials inorganic and organic elastomers, in particular polyvinylsiloxane, addition-crosslinking silicone elastomers, also in the form of two-component -Systems, as well as acrylates are used.

By the WO 94/23610 A1 For example, there is known a method of making a fastener part in which a backing is made having a plurality of stems preferably integrally connected thereto. As an application of such a type of adhesive closure part produced, in particular the formation of an adhesive closure for baby diapers or for hospital clothing is disclosed. In order to make fastener fasteners that can be used in the adhesive closures of such garments, a relatively high number of entangling means per square centimeter is required, resulting in correspondingly high production costs, since the prior art molding roll used to form the entangling means has the appropriate number of entangling means must have open cavities, which are only consuming inculcate. The adhesive fastener parts thus produced have on a foil-like support material integrally arranged and projecting in the vertical direction stems, which are provided at its free end with a head-side widening, the Making the releasable adhesive closure cooperate with a corresponding loop or loop material which mechanically entangles with the underside of the head-like widening of the stem material. These locking systems are also often advertised in German-speaking countries with the brand name Kletten ^® -Haftverschlüsse. Disadvantage of these known Kletten ^® -Haftverschlußsysteme is that they must work together for effective arrest, so the formation of the actual adhesive closure, always with corresponding closure parts (Velcro or loop fabric), with modern closure systems today also show the possibility of the same head closure parts together connect to form the adhesive closure by the head-side ends of a closure member engage in the distances between the head-side ends and stems of the other closure member and the radially widened against the stems head parts then interlock with their mutually facing edge surfaces mutually, wherein the pertinent Closure systems are designed detachable.

Furthermore, processes for producing fibrillated films of polypropylene or polyethylene are known in the art ( DE 198 37 499 A1 . US Pat. No. 6,432,347 B1 ), in which using the existing plant technology (film extrusion lines for flat film, blown film or the use of chill-roll process) by special measures in the technology and at the plants films without division in ribbons complex stretched, fibrillated and wound up and so on net-like film with different width and long length can be produced. Due to the monoaxial stretching in this known solution, there is an improved molecular fiber orientation and the fabric thus produced find their application as geotextiles or in construction as Reinforcement. Furthermore, in the German patent application 1 175 385 and in the U.S. Patent 6,432,347 described a fibrillation of sheet material by using a vortex nozzle or with a pulsed water jet at high pressure, so as to arrive at an improved filter material or a sheet-like material with improved thermal and acoustic acoustic insulation properties.

To get to new effects in the connection technology related to fastener parts, is in the post-published DE 103 25 372 A1 has been proposed in a fastener part to provide at least a portion of the free ends of the stems of the fastener material with a plurality of individual fibers, wherein the diameter of the respective fiber is selected to be very thin, so that at the free end of each individual fiber only a very small contact surface available is, for example, in the order of 0.2 to 0.5 μ m. In preferred embodiments, the thickness range of this structure in the form of the stems, to which the individual fibers follow, but also in the nanometer range, for example at 100 to 400 nanometers, are. These orders of magnitude are sufficient for an interaction with the corresponding part (surface) on which the adhesive closure part is to be determined to take place via the so-called van der Waals forces.

Van der Waals forces are, according to Van der Waals, named intermolecular forces, which appear as weak binding forces between inert atoms and saturated molecules. While only the so-called dispersion forces are used in the interaction between atoms, the interactions of induced or possibly existing permanent dipole moments (orientation effect) are effective as additional attractive forces in molecules. It should be noted that although some Van der Waals forces are considered to be synonymous with intermolecular forces, but the majority of van der Waals forces are understood to be those very wide-ranging forces of attraction between neutral molecules whose energy decreases with the 6th power of the molar distance , The forces are, for example, effective in host-guest relationships, in molecular lattice crystals, inclusion compounds, molecular compounds and in phenomena of colloid chemistry, interfacial and surface chemistry, etc. (see RÖMPPS CHEMIE LEXIKON, 8th ed., Franckh'sche Verlagshandlung Stuttgart).

In order to obtain the respective individual fibers, initially projecting cylindrical stems are produced on a strip-like carrier part, which is obtained from a die-rolling operation by means of a sieve, a calendering process or without forming tools via a droplet application process, and then the stalk ends are chemically, mechanically or electrically divided into individual filaments or single fibers. The thus obtained fastener part or adhesive element finds its equivalent in nature, for example, in the feet of a gecko, which is able to move due to the foot design below a ceiling or along vertically extending glass surfaces. The said stems, which are present in a billion-fold arrangement in a gecko foot, are referred to in the jargon with "Seta" and the adjoining the free end of the stem individual filaments or single filaments as a "spatula".

So was in the WO 01/49776 A1 already proposed to remove the Seta elements from the living object for the construction of adhesive fastener parts and to connect with a support member as a substrate, which as a substitute manufacturing process this already molding with pipetting and modern printing processes are considered. Comparable to this is in the WO 03/095190 A1 The idea is to create the Seta elements using a first shaping template, followed by a second shaping template for the formation of the spatula congruently. In addition to the problems of demoulding in the illustrated stencil technique, this is only in the context of laboratory technical implementation suitable, as well as the other methods mentioned in relation to the artificial empathy of the gecko foot structure. A use of the Van der Waals forces for a fastener part or a bonding part on a large industrial scale is not possible with the said method.

The WO 03/099951 A2 shows microstructured surfaces with increased adhesion. To produce these surfaces, a method is used for producing adhesive elements on a carrier material by using at least one plastic material which is treated with an electrostatic flocking process, wherein the plastic materials used are organic elastomers, in particular polyvinylsiloxane.

Based on this prior art, the present invention seeks to further improve the known manufacturing process for producing adhesive elements, which adhere to the basis of van der Waals forces, that they can be produced inexpensively on a large industrial scale and yet to a great extent develop an adhesive effect. This object is achieved by a method having the features of claim 1 in its entirety.

According to the invention, it is provided that a drum-shaped or band-shaped sieve is used as the respective shaping element, the sieve having more than 10,000, but preferably with 16,000 mold cavities per cm ^{2 is} provided. Very good arrest results have been found, provided that about 16,000 adhesive elements per cm ^{2 of} carrier material are present, the individual adhesive elements then have only one size, in particular height of about 100 μ m and smaller with a diameter of the widening head end of about 60 μ m or smaller.

The fact that with the inventive method adhesive elements can be produced with widened ends whose adhesion is mainly realized by means of said van der Waals forces, the very good adhesion values of a gecko foot are achieved as a biomechanical model, without according to the specifications in Nature has a fuzzification of Haftstiele to do. It is surprising to a person of ordinary skill in the field of closure technology that, turning away from the trodden way of having to simulate nature identically, he arrives at adhesive elements with very good adhesion properties, predominantly produced by the van der Waals forces, in which without fraying widened at the end of the stems end surfaces are provided.

The pertinent adhesion or adhesive part can be produced very inexpensively on a large industrial scale and connect with the reason with each surface (substrate) releasably connected, for example, a provided with the adhesive elements body part with a vehicle frame or such a picture or a screen to the Hang wall without further connection means by the adhesive elements interact with their widened ends directly to the surface on the above Van der Waals forces.

If the adhesive element part produced by the process according to the invention finds its way into the clothing industry, no further modifications are necessary here, in particular no loop or fleece material is to be arranged on parts of the clothing in order to ensure entanglement with the otherwise conventional adhesive closure parts (mushroom or hook) , Rather, here directly the closure member interact with the adhesive elements on the free widened ends with the material of the clothing fabric for making a connection. It has been found that in order to release the adhesive elements from a surface, they are preferably peeled off the surface, preferably at an angle of 90 °, so as to release the adhesion via the van der Waals forces and the closure from the surface to be able to remove any nature again. The pertinent attaching and detaching operations can take place several times, preferably several thousand times, depending on the design of the closure system.

To produce the closure or the preferred connection, it is sufficient to set the adhesive elements with the free widened ends of the otherwise stem-shaped adhesive elements flat on the surface. Preferably, it is provided that the length of the adhesive elements is selected such that they open for each stem on their free ends in a common plane, since the van der Waals forces act only over a very short distance, so preferably provide is that the distance of the free contact ends of the widened ends of the single stem to the intended surface substantially constant. In order to avoid that the adhesive elements can bend away from the surface to be contacted, they have a sufficient inherent rigidity; However, in order to ensure a good separation behavior, it can be provided that the widened ends have a corresponding diameter reduction are connected in the transition region to the stem in such a way. In this way, at the transition point creates a kind of joint, so that the band-like support member with the stems is already peeled off and then adhering surface end of the Abschälbewegung follows in the sense of a rolling movement on the respective joint.

Further advantageous embodiments of the method according to the invention are the subject of the other dependent claims.

Fig.1

eine Seitenansicht auf eine Vorrichtung zur Durchführung des erfindungsgemäßen Verfahrens;

Fig.2

in stark vergrößerter Darstellung einen Längsschnitt durch einen Formhohlraum gemäß der Darstellung nach der Fig.1;

Fig.3

in stark vergrößerter Darstellung die auf einem Trägermaterial angeordneten Haftelemente, hergestellt mit dem erfindungsgemäßen Verfahren.

In the following the method according to the invention will be explained in more detail on the basis of an adhesive element part obtained with it according to the drawing. This show in principle and not to scale representation of the

Fig.1

a side view of an apparatus for performing the method according to the invention;

Fig.2

in a greatly enlarged view, a longitudinal section through a mold cavity as shown in the Fig.1 ;

Figure 3

in a greatly enlarged view arranged on a substrate adhesive elements prepared by the method according to the invention.

The starting material shown in Figure 3 of adhesive elements in the context of this invention can be, for example, by a method as in DE 100 39 937 A1 described, received.

Fig.1 shows a schematic representation of parts of a device for carrying out the method according to the invention with a nozzle head 1 as a feeding device for plastic or liquid and thixotropic plastic, which is supplied as a band whose width corresponds to that of the adhesive element to be produced, the gap between a pressure tool and a mold , As shown by the Fig.1 serves as a pressure tool, a pressure roller 3 and the mold is a designated as a whole with 5 forming roller. Both rollers are in Fig.1 Driven by arrows 7 and 9 indicated directions of rotation, so that between them a conveying gap is formed, through which the plastic strip is conveyed in the transport direction, while the plastic strip is formed in the gap as a shaping zone to the carrier 10 as a carrier material of the fastener elements and the carrier 10 at the the shaping roller 5 adjacent side by the shaping elements of the forming roller 5 is replaced by the necessary to form the adhesive elements shaping.

For this purpose, the forming roller 5 on the periphery of a screen 11 with individual mold cavities 12. A pertinent mold cavity 12 as a shaping element is exemplified in the Fig.2 shown enlarged. The inflow direction of the plastic material takes place in the direction of the Fig.2 seen in the region of the pressure roller 3 from top to bottom. Furthermore, the mold cavities 12, which is not shown in detail, regularly distributed over the forming roller 5 with its sieve 11 on the outer peripheral side, wherein the distribution and the number are selectable; Preferably, however, more than 10,000 of these mold cavities 12 per cm ² are arranged on the wire and particularly favorable for the design of the adhesive elements has a number of 16,000 mold cavities 12 per cm ² proved. The Fig.2 gives a longitudinal section again of each used Mold cavity 12, wherein the longitudinal boundary opposite boundary walls 13 are provided with a continuous convex path 14 throughout. It is understood that the said two boundary walls 13 with respect to the rotationally symmetrical structure of the mold cavity 12 basically part of a final shaping wall 15 which is bounded by the screen material 11 of the forming roller 5. With the pertinent mold cavities 12, it is possible to produce adhesive elements in the form of each one provided with a head part 16 as a widened end stem part 17th

As the Fig.2 shows further, while the curvature of the respective track 14 in the direction of the head part 16 to be formed is designed to be stronger than in the direction of a foot part 18, via which the stem part 17 is connected to the carrier 10. In this case, it has proven to be particularly advantageous if, viewed from the longitudinal direction of the stalk part 17 in the direction of the head part 16, the course of the track 14 with its greater curvature above the middle, preferably beginning in the upper third, is provided.

In order to obtain the mentioned mold cavities 12 with their rotationally symmetrical structure in the form of a hyperboloid, galvanic coating processes, in particular electroplating processes, have proven in which first a cylindrical mold cavity (not shown) is coated or platinized with a coating material until the convex Trajectory 14 sets. In addition, it would also be possible, if appropriate, to produce the convex path 14 from a sieve or lattice solid material by means of a laser process or an etching process.

The adhesive elements shown in Figure 3 can be obtained with the method and apparatus described above. The symmetrical Construction results directly from the production in a mold cavity 12 after the Fig.2 , Instead of the device shown in the Fig.1 Instead of the pressure roller 3, a doctoring tool (not shown) can also be used which directly spends the plastic material into the mold cavities 12 in the sense of a doctoring process. Also, the cylindrical screen structure may form a belt that circulates between two cylindrical drive rollers (not shown), in which case the plastic material is again preferably doctored onto the belt surface. In addition, if it is crosslinkable plastic materials, a heat source or UV light (not shown) may allow post-crosslinking as soon as the adhesive elements are removed from the mold cavities 12. This post-crosslinking is common, so that will not be discussed here at this point. Preferably, however, in a forming process by means of a screen belt, crosslinking with the mentioned means is provided, at least on one side, directly in the mold cavities 12.

In order to obtain an optimum with respect to the van der Waals forces, preferably the free widened head ends should run as a head part 16 outwardly flat. Since the individual mold cavities 12 are closed inwardly by the forming roller 5, it would not be possible to the extent that the air trapped there during the molding operation presses a concave air cushion into the free head end. To counter this, it may be provided to provide within the forming roller 5 a means which allows the air to escape or which allows the air in the mold cavity 12 to be sucked off, for example via a vacuum device or the like. In the latter case, however, a corresponding drive device is then necessary in order to purposefully initiate the vacuumization and to prevent the flat head ends from buckling in the direction of the forming roller 5, but a slight convex curvature of the free head end is harmless. As in the cross section, the stem and head design looks like results from the representation of the Fig.2 , The plastic material is displaced into the mold cavity 12 and then comes to rest there and then forms the flat head outside. In that regard, the plastic material solidifies in the mold itself and is then removed in the pre-solidified state from the mold cavity 12 or already largely cured in this; but only insofar as a demolding process is not affected. The average constriction, due to the shape of the Rotationshyperboloids can still continue in such a way that at a further constricted point a kind of joint between the stem part 17 and the head part 16 is formed. The pertinent joint is, as already stated, favorable for the operation of the van der Waals closure system.

Suitable plastic materials are inorganic and organic elastomers, in particular polyvinyl siloxane, as well as addition-crosslinking silicone elastomers, also in the form of two-component systems and acrylates. The use of rubber materials is also possible.

aufweist. Im Sinne einer sich selbst abreinigenden Oberfläche hat es sich darüber hinaus als günstig erwiesen, Kunststoffmaterialien zu verwenden, deren Kontaktwinkel aufgrund ihrer Oberflächenenergie für die Benetzung mit Wasser mindestens einen Wert von größer 60 grd aufweist. Unter Umständen läßt sich die dahingehende Oberflächenenergie auch durch nachträgliche Beschichtungsverfahren noch weiter verändern.The process can be particularly favorable if the plastic material used in each case is thixotropic. Thixotropic behavior in the context of the invention is intended to mean the reduction of the structural strength during the shear stress phase and its more or less rapid but complete reconstruction during the subsequent rest phase. This degradation / recovery cycle is a fully reversible process and thixotropic behavior is definable as a time dependent behavior. Furthermore, plastic materials have proven to be favorable, in which the viscosity measured with a rotational viscometer ranges from 7,000 to 15,000 mPas, but preferably a value of about 10,000 mPas at one Shear rate of ${10}^{\frac{1}{\sec }}$

having. In terms of a self-cleaning surface, it has also proven to be beneficial to use plastic materials whose contact angle due to their surface energy for wetting with water has at least a value of greater than 60 grd. Under certain circumstances, the surface energy can also be further modified by subsequent coating processes.

In order to clarify the size (height) ratios of the obtained adhesive element material, in FIG. 3, X denotes a length which corresponds to the size of approximately 100 μm . In the following, the geometric dimensions of the adhesive elements are given, the specified magnitudes of the better representation because of their direct precipitation in Figure 3 find that reflects only the structure of the adhesive element material in principle. In the preferred embodiment of the adhesive element material according to the invention are more than 16,000 adhesive elements on a cm ² substrate 10. From the top of the carrier 10 calculated until the completion of the adhesive element on the flat top top, each adhesive element has a height of about 100 μ m, which is the Size scale X according to the Fig.3 corresponds. The planar top surfaces have a diameter of about 50 μ m and reduce towards the upper end of the stem part 17 (joint) to a size of about 30 μ m. In that regard, an undercut is formed between the head part 16 and stem part 17 at the point of transition. The height of the head portion 16 is about 10 μ m and the size of the radial overhang of the head part 16 to the upper end of stem portion 17 is approximately 10 μ m. The distances between the boundaries of mutually adjacent opposite head portions 16 are 30 .mu.m to 40 .mu.m . The diameter of the stem portion 17 is about 20 μ m to 35 μ m. The pertinent proportions are only exemplary and can be changed in said size frame, in any case it must be ensured that compared to the stem parts 17, the head part 16 has a flat or slightly convex surface, which allows the effect of van der Waals forces, provided the adhesive element part a surface of any kind comes into contact. Due to the nanostructure of the adhesive elements, the adhesive element part which can be produced here on an industrial scale can no longer be seen with the naked eye and it is surprising that due to the adhesive element structure, a very secure releasable attachment takes place via the van der Waals forces.

Both the cross-sections of the head and the cross-sections of the cross-sections may be angular, in particular provided with a hexagonal cross-sectional shape, and the aspect ratio of each adhesive element is preferably between 1: 3 and 1: 5. With the method according to the invention, adhesive elements can be provided on the closure characteristic by means of van der Waals forces in a cost-effective and reliable manner on a large-scale industrial scale.

Claims (7)

1. A process for producing adhesion elements on a substrate material (10) by using at least one plastic material which is introduced into at least one shaping element (12), adhesion elements with widened ends thus being produced, the adhesion of which is accomplished predominantly by means of van-der-Waals forces, inorganic and organic elastomers, in particular polyvinyl siloxane, addition-crosslinking silicone elastomers, also in the form of two-component systems, and acrylates being used as plastic materials, characterised in that a drum- or strip-shaped screen (11), which is provided with more than 10,000, but preferably with 16,000 moulded cavities (12) per cm², is used as the respective shaping element.
2. The process according to Claim 1, characterised in that the respectively used plastic material is thixotropic and has a viscosity of 7,000 to 15,000 mPas measured with a rotary viscosimeter, but preferably has a value of approximately 10,000 mPas at a shear rate of 10 l/sec.
3. The process according to Claim 1 or 2, characterised in that the respective moulded cavity (12) is configured in the manner of a hyperboloid.
4. The process according to any of Claims 1 to 3, characterised in that the plastic material used is one with a contact angle which has at least a value of greater than 60 degrees, preferably greater than 70 degrees due to the surface energy for the crosslinking with water.
5. The process according to any of Claims 1 to 4, characterised in that the widened ends of the adhesion elements are made substantially flat or slightly convex.
6. The process according to any of Claims 1 to 5, characterised in that the respective adhesion element is formed from a stem part (17) with a height of 50 µm to 150 µm, preferably approximately 90 µm, and a diameter of from 10 µm to 40 µm, preferably of approximately 30 µm, and that the widened ends have as head parts (18) on the stem parts (17) a diameter of 15 µm to 70 µm, preferably of approximately 50 µm.
7. The process according to any of Claims 1 to 6, characterised in that for crosslinkable plastic materials they are re-crosslinked with or after preparation of the adhesion elements, for example with UV light.

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