Method for manufacturing a flexible surface-area element and surface-area element manufactured thereby

Abstract

To provide a method for manufacturing a flexible surface element in which the properties of an effective layer are significantly improved, and a manufactured flexible surface element with improved properties of the effective layer.SOLUTION: There is provided a method for manufacturing a flexible surface element (1) with an inner or outer effective layer (3) in which expandable hollow microspheres (4) are introduced, preferably in a uniform distribution, into a functional layer (6). At least one additional pressure-resistant layer (5) is releasably attached to the effective layer (3). The hollow microspheres (4) are heated and expanded, preferably uniformly, by supplying thermal energy to a temperature above an expansion temperature, and expansion of the hollow microspheres (4) is controlled by a pressure-resistant property of the pressure-resistant layer (5). In this case, a material thickness (D) of the effective layer (3) is reduced by expansion and a surface quality is substantially improved. The pressure-resistant layer is finally removed from the effective layer (3).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a flexible surface-mounted element having at least one inner or outer thermoplastic active layer into which expandable hollow microspheres are introduced, preferably with a uniform distribution. Furthermore, the present invention relates to the surface-mounted element thus produced. [Background technology]

[0002] It is generally known to expand thermoplastic plastics using expansion means, for example, expandable hollow microspheres.

[0003] These expandable hollow microspheres, also called microspheres, consist of a thin plastic shell, such as polyacrylonitrile or a copolymer, filled with a gas, usually a hydrocarbon. The applied temperature in thermoplastic processing softens the plastic shell while simultaneously expanding the enclosed gas, thereby expanding the hollow microspheres. A combination of chemical expansion means and expandable hollow microspheres is also used.

[0004] The production and use of expandable thermoplastic hollow microspheres is disclosed, inter alia, in U.S. Patent No. 3,615,972. The unexpanded spheres contain a volatile liquid expansion agent that transitions to a gaseous state upon application of heat. When heat is applied, the polymer shell softens, the expansion agent becomes gaseous, and the spheres expand.

[0005] EP 0 348 372 describes a method in which unexpanded hollow microspheres are expanded using a hot blower and an exhaust system, for example by infrared radiation.

[0006] It is also known to expand thermoplastic polyurethanes by chemical expansion means, which in the case of thermoplastic polyurethanes results in a relatively very coarse foam structure and increases the formation of voids.

[0007] To overcome this drawback, EP-A-0 692 516 describes a method for producing thermoplastic polyurethane-based foams in which a mixture of a chemical expansion agent and hollow microspheres is used as the expansion agent.

[0008] US Patent No. 6,103,152 relates to a method for producing polymer foams in which expandable polymer microspheres are mixed with a molten polymer composition and the polymer microspheres are expanded within the polymer composition before the composition is discharged from a nozzle. After discharge from the nozzle, the microspheres can be further expanded by heating the polymer foam. The polymer foam can have a substantially smooth surface and can also be produced as a film.

[0009] From US Patent Application Publication No. 20060219350, an adhesive composition is known which is arranged between surfaces or layers and contains two types of heat-expandable microspheres, where the first type of microspheres serves for hardening and the second type of microspheres serves for release, the different types of microspheres being activatable at different temperatures.

[0010] U.S. Patent No. 5,783,302 describes a calendering system that can produce in-situ expandable thin films. The films contain a liquid expansion means or agent. The resin matrix can contain hollow glass microspheres.

[0011] EP 2134425 relates to the use of an endless belt as a treadmill belt for running training equipment. The expansion can be achieved by adding expandable microspheres to the thermoplastic material, and the expanded layer thus obtained can then be applied to the tension member by calendering in a second working stage.

[0012] In practice, when manufacturing flexible surface-area elements, the limited or partially different surface quality of the active layer often proves to be a disadvantage. In particular, irregularities, micropores or cavities cannot be reliably eliminated. In addition, the limited dimensional accuracy of such surface-area elements is hindered by the continuous expansion of hollow microspheres, for example after calendering. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] U.S. Patent No. 3,615,972 [Patent Document 2] European Patent No. 0348372 [Patent Document 3] European Patent Application Publication No. 0692516 [Patent Document 4] U.S. Patent No. 6,103,152 [Patent Document 5] US Patent Application Publication No. 20060219350 [Patent Document 6] U.S. Patent No. 5,783,302 [Patent Document 7] European Patent No. 2134425 Summary of the Invention [Problem to be solved by the invention]

[0014] The object of the present invention is to provide a method for producing a surface-area element with significantly improved properties of the active layer, and a flexible surface-area element produced thereby with improved properties of the active layer. [Means for solving the problem]

[0015] The first problem is solved according to the invention by a method for producing a surface-area element according to the features of claim 1. Further embodiments of the invention can be read from the dependent claims.

[0016] The present invention thus provides a method for producing a flexible surface-mounted element having an inner and / or outer thermoplastic, thermosetting or elastomeric active layer, characterized in that expandable hollow microspheres are introduced, preferably in a uniform distribution, and at least one additional pressure-resistant layer is releasably attached to the active layer, and then at least one section of the surface-mounted element to be treated is heated, preferably uniformly, by supplying thermal energy to a predetermined temperature within the expansion temperature range of the hollow microspheres, which is lower than the upper temperature limit of the hollow microspheres, thereby at least partially expanding the hollow microspheres contained in the section to be treated and / or the hollow microspheres already expanded, resulting in a balance between the expansion pressure of the pressure-resistant layer and the back pressure, so that the expansion of the hollow microspheres is limited by the pressure-resistant properties of the pressure-resistant layer, the material thickness of the active layer is reduced by the expansion, and then the pressure-resistant layer is at least partially removed from the active layer.

[0017] In this case, a pressure-resistant layer is understood according to the invention to mean a flexible, but tensile-strength, inelastic, at most plastically stretchable layer suitable for withstanding the expansion pressure in order to dimensionally limit the expansion. Based on these properties, the pressure-resistant layer can be said to have tensile strength.

[0018] In a typical application of the method according to the present invention, uniform heating of the planar element, and therefore of the thermoplastic effective layer, occurs. The hollow microspheres expand, compressing the effective layer. The pressure-resistant layer acts as a cover film to counteract the expansion. This evens out even the smallest irregularities on the surface of the effective layer, resulting in a so-called mirror-like surface after removal of the pressure-resistant layer. This opens up entirely new application possibilities for the planar element, for example in the printing industry. Additionally, the material thickness of the planar element can be precisely set by adjusting the temperature with high reproducible precision.

[0019] A particularly advantageous embodiment of the present invention is achieved by completely removing the pressure-resistant layer from the effective layer after the hollow microspheres have expanded. In this case, the surface texture of the effective layer exposed in this way matches the surface texture of the opposite side of the pressure-resistant layer, achieving the highest quality requirements in practice. Naturally, the pressure-resistant layer can also transfer a structuring or pattern to the effective layer as a negative of the corresponding texture of the pressure-resistant layer.

[0020] In this case, it has proven to be particularly advantageous if the pressure-resistant layer comprises a film, in particular made of polyester, as the main material component, preferably with a constant material thickness. Alternatively, it is also possible to provide areas with different material thicknesses in order to allow for limited stretching of the pressure-resistant layer in individual areas, for example, resulting in localized bulges in the active layer.

[0021] Additionally, the pressure-blocking layer may allow certain substances to be transferred onto or into the surface of the effective layer, or to remain in the effective layer when the pressure-blocking layer is removed.

[0022] It is conceivable that the pressure-resistant layer is formed as a metal film that can be used multiple times, and it is particularly preferred that the pressure-resistant layer comprises a biaxially or bidirectionally pre-stretched film that can also be used, for example, as a protective film and that is only removed from the useful layer before the use of the surface-area element.

[0023] Another equally promising variation of the method is to locally or partially vary the energy input during heating of the portion of the planar element to be treated above the expansion temperature. This results in at least one region with a lower energy input and at least one other region with a higher energy input. Depending on the three-dimensional expansion limited by the pressure-resistant layer, different compression occurs in different regions, resulting in regions of the planar element with different densities. This also results in different mechanical properties, such as flexibility within the regions. This can provide flexible zones, which prove advantageous for applications such as conveyor belts in turning areas.

[0024] Another particularly practical embodiment of the invention is achieved by locally or partially removing and / or modifying the pressure-resistant layer before, during or after heating of the useful layer by energy input. For example, the pressure-resistant layer can be cut, perforated or weakened by a mechanical tool or laser radiation, so that in these areas the useful layer becomes protruding or convex. A pressure-resistant layer already applied to the useful layer can then be modified, thereby generating individual properties of the useful layer.

[0025] In this case, the releasable connection of the pressure-resistant layer and the useful layer is realized, for example, by means of an adhesive joint.

[0026] In another advantageous variant of the method according to the invention, several, in particular different, pressure-resisting layers are releasably attached to the useful layer, the different layers in particular also covering different partial areas. The use of several pressure-resisting layers allows the expansion of the useful layer and thus the material thickness of the surface-area element thus produced to be set. For example, this allows local unevenness to be realized, since areas with a smaller number of pressure-resisting layers stand out more than other areas with a larger number of pressure-resisting layers.

[0027] Similarly, the individual pressure-resistant layers may, for example, be provided with cutouts or perforations having a pattern that can be correspondingly transferred to the payload layer.

[0028] Thermal energy can be selectively introduced at different wavelengths or intensities to different delimited regions of the planar element, in particular to longitudinally extending tracks, laterally extending portions and / or planes extending within different cross-sectional levels, causing the hollow microspheres to expand differently in the different regions.

[0029] That is, hollow microspheres bonded within the material of the surface-area element, which constitutes a matrix for the hollow microspheres, can be selectively activated after the completion of the surface-area element, which may also comprise additional decorative or functional layers in addition to the active layer, thereby causing the hollow microspheres to expand depending on the energy input. In this way, material properties such as damping or dimensional stability can be set with high precision in relation to the pressure-resistant layer, and the external contour of the surface-area element, particularly its thickness, is limited by the pressure-resistant layer, thus ensuring high dimensional precision of the surface-area element. In this context, the term "area" should be understood to mean a surface area within a plane parallel to the outer surface and / or a plane within the material thickness, and should include the full activation of the inventive concept. Selective activation of different areas with different radiation energies can retain unexpanded hollow microspheres in other partial areas. In this context, the invention is not limited to hollow microspheres with predetermined properties. Rather, hollow microspheres with different properties can be introduced into the surface element.

[0030] In this case, it has proven particularly expedient if the hollow microspheres are introduced into the carrier material in different spatially separated regions in different quantitative ratios relative to the volume or mass of the hollow microspheres, in order to provide a sufficient amount of hollow microspheres in the region where activation of the hollow microspheres is intended.

[0031] Another, equally particularly effective embodiment of the method according to the invention is realized by introducing electromagnetic radiation in the infrared spectrum (IR) into the surface element as high-energy radiation, and simultaneously setting the level that can be reached in the layer structure, for example by selecting the wavelength of the radiation, so that the high-energy radiation can be selectively limited to relatively small, possibly individual point-like areas, in order to generate any desired structure.

[0032] In this case, it has proven particularly promising if, by selecting a predetermined wavelength range, the hollow microspheres are expanded and / or activated in different planes spaced apart differently relative to the treadmill side and / or in different longitudinal sections, for example peripheral sections, in order to optimize the properties of the surface-area element in appropriate, predetermined partial regions.

[0033] Furthermore, it is particularly advantageous if additional fillers, especially fibrous or strand-like fillers, are introduced into the working layer. This allows for further reinforcement of the working layer, if necessary, in order to further improve the dimensional stability of the planar element to be produced. It has already been found that by using multi-layer fillers, in which hollow microspheres are introduced, a significant improvement in strength can be achieved, taking into account the total mass of the composite thus produced.

[0034] It is also advantageous if the hollow microspheres contain an active or reactive substance that is released by high-energy radiation and reacts with components of the adjacent material of the planar element. To this end, the hollow microspheres are expanded until they burst or their respective shells become permeable, allowing the filler to escape. The filler then reaches the adjacent areas of the strip material as a gaseous or liquid fluid and reacts with the material present at the bottom of the planar element. For example, a hardener that irreversibly reacts with the material of the effective layer to harden the effective layer is conceivable. Optionally, the expansion of the hollow microspheres can also weaken the shell so that the closure that occurs during use of the planar element renders the shell permeable. In this way, the hollow microspheres can also be used as carriers for wear indicator substances. The color change achievable in this way can be nearly visual and can therefore be used as a wear indicator.

[0035] Of course, the dye can also be characterized so that it is invisible under ambient conditions and only becomes detectable with light of a certain wavelength (UV).

[0036] In the case of materials used as contamination indicators, the hollow microspheres contain microorganisms that react with, for example, moisture or air, so that upon abrasion, the microorganisms initiate a biological reaction on contact. Naturally, the reaction partners of the microorganisms can also originate from the transported material, for example, food or chemicals. Conversely, the released material can also release decontaminating, disinfecting, biocidal or other agents to protect the transported material.

[0037] Of course, the hollow microspheres can be mixed with other additives, such as color or conductivity additives, to achieve certain desired properties.

[0038] The energy for expanding the hollow microspheres can be introduced by any heat source, for example, by a heat transfer fluid. In this case, it is particularly advantageous to introduce high-energy radiation by a radiation source with a specifically settable wavelength adapted to the region to be activated, whereby the radiation source introduces, for example, a wavelength in the infrared range, into each region of the surface-area element at a freely selectable layer level, leaving other regions unaffected by the high-energy radiation and thereby eliminating heating there.

[0039] Another object of providing a flexible surface-area element with improved properties of the active layer is achieved according to the invention in that the flexible surface-area element comprises at least one expanded thermoplastic active layer, which is produced by expanding hollow microspheres of the surface-area element against a pressure-resistant layer and then locally removing at least the pressure-resistant layer.

[0040] The surface-area element according to the invention is not limited thereto. It is therefore also suitable as a process or printing belt for transferring printable substances, such as dyes. The compressibility required in this case, which is set within narrow tolerance limits, can be optimally set by the pressure-resistant layer.

[0041] According to a particularly advantageous embodiment of the invention, the surface-area element comprises at least one thermoplastic active layer and at least one tension element, so that the active layer containing hollow microspheres absorbs no or only little tensile forces during operation.

[0042] The invention is susceptible to different embodiments, one of which is shown in the drawings and described below in order to make its basic principles clearer, each of which is shown in cross section. [Brief explanation of the drawings]

[0043] [Figure 1] Planar element according to the invention having a heated active layer of hollow microspheres contained within the active layer [Figure 2] Planar elements after expansion of hollow microspheres with the effective layer compressed against the pressure-bearing layer [Figure 3] Plane element after removing the pressure-resistance layer DETAILED DESCRIPTION OF THE INVENTION

[0044] The method according to the invention for producing a flexible 2D element 1 is explained in more detail below with reference to Figures 1 to 3. The 2D element 1 shown is designed for use in printed products, so the highest demands are placed on the surface quality of the thermoplastic effective layer 3 made of TPU, which is present on the tensile element 2. Expandable hollow microspheres 4 are introduced into the functional layer 6 with the effective layer 3 in a uniform distribution; these hollow microspheres are shown exaggeratedly and not to scale in order to clarify the inventive concept. A pressure-resistant layer 5, which does not contain hollow microspheres 4, is attached to the effective layer 3. Of course, the hollow microspheres 4 can also be introduced in a non-uniform distribution.

[0045] The key idea according to the present invention is based on the planar or localized activation of hollow microspheres 4 by thermal energy supply of high-energy radiation 7, in particular electromagnetic radiation in the infrared spectrum, in order to heat the shells (not shown) of the hollow microspheres 4 above their softening temperature. Thus, the radiation 7 penetrates the pressure-resistant layer 5 as well as the effective layer 3 and is focused or concentrated within the desired cross-sectional level of the functional layer 6, with no or only minimal heating of the pressure-resistant layer 5 and the effective layer 3. This results in the expansion of the relevant hollow microspheres 4, as can be seen in FIG. 2.

[0046] The expansion of the hollow microspheres 4 firstly causes a change in the mechanical properties of the surface element 1, so that the surface paper can only now be properly adapted to the respective application.

[0047] However, a further important aspect according to the invention is the compression of the useful layer 3 against the pressure-resistant layer 5, which acts as a barrier or abutment, so that its thickness D is reduced to a reduced thickness d. At the same time, the compact useful layer 3 thus generated obtains excellent surface properties, in particular an optimally smooth surface with a mirror-like quality. In particular, this compensates for or eliminates all surface defects.

[0048] As shown in FIG. 3, the pressure-resistant layer is removed last, so that the surface of the effective layer 3 is available. The present application relates to the invention described in the claims, but may also include the following as other aspects. 1. A method for producing a flexible surface-area element (1) having at least one effective layer (3) of a thermoplastic, thermosetting and / or elastomer, characterized in that expandable hollow microspheres (4) are introduced into the effective layer (3) and / or into the functional layer (6), preferably in a uniform distribution, and at least one additional pressure-resistant layer (5) is releasably attached to the effective layer (3), and then at least one part to be treated of the surface-area element (1) is heated, preferably uniformly, by supplying thermal energy to a temperature within the expansion temperature range of the hollow microspheres (4), whereby at least the hollow microspheres (4) contained in the part to be treated are at least partially expanded and / or the already partially expanded hollow microspheres (4) are further expanded, the expansion of which is limited by the pressure-resistant properties of the pressure-resistant layer (5), which is then at least partially removed from the effective layer (3). 2. The method according to claim 1, characterized in that the pressure-resistant layer (5) comprises a film made of, in particular, polyester as the main material component. 3. The method according to claim 1 or 2, characterized in that the pressure-resistant layer (5) comprises a film that is particularly biaxially pre-stretched. 4. The method according to at least one of the above items 1 to 3, characterized in that the pressure-resistant layer (5) is locally or partially removed and / or modified before and / or during heating. 5. The method according to at least one of the above items 1 to 4, characterized in that a plurality of, in particular different, pressure-resistant layers (5) are applied onto the effective layer (3). 6. The method according to at least one of the above items 1 to 5, characterized in that the material thickness (D) of the effective layer (3) is reduced to a material thickness (d) by the expansion of the hollow microspheres (4). 7. A method according to at least one of items 1 to 6 above, characterized in that the energy of the radiation (7) passing through the pressure-resistant layer (5) acts selectively and differently, in particular with different parameters, on different separated regions and / or different cross-sectional levels of the effective layer (3) and / or functional layer (6) of the surface-area element (1), so that the hollow microspheres (4) are expanded differently in different regions and cross-sectional levels of the surface-area element (1). 8. The method according to at least one of claims 1 to 7, characterized in that the energy input is achieved by electromagnetic radiation (7), in particular in the infrared spectrum (IR), and is set in such a way that at least individual areas and / or cross-sectional levels of the effective layer (3) are heated and the pressure-resistant layer (5) is penetrated by the radiation (7) at least substantially without heating. 9. A flexible planar element (1) having at least one expanded active layer (3) produced by expanding hollow microspheres of the planar element (1) against a pressure-resistant layer (5) and then locally removing at least the pressure-resistant layer (5). 10. A planar element (1) according to claim 9, characterized in that at least one pressure-resistant layer (5) comprises cutouts or perforations. [Explanation of symbols]

[0049] 1 Planar element 2 Tensile members 3. Effective layer 4 Hollow microspheres 5 Pressure-resistant layer 6 Functional Layers 7. Radiation D Thickness d Thickness

Claims

1. 1. A method for producing a flexible surface-area element (1) having at least one effective layer (3) of thermoplastic, thermosetting and / or elastomer, characterized in that expandable hollow microspheres (4) are introduced into the effective layer (3) and / or into the functional layer (6), preferably in a uniform distribution, and at least one additional pressure-resistant layer (5) is releasably attached to the effective layer (3), and then at least one section to be treated of the surface-area element (1) is heated, preferably uniformly, by a supply of thermal energy by focused or concentrated radiation (7) to a temperature within the expansion temperature range of the hollow microspheres (4), so that at least only those hollow microspheres (4) contained in the section to be treated are at least partially expanded and / or only those hollow microspheres (4) already partially expanded contained in the section to be treated are further expanded, the expansion of the hollow microspheres (4) being limited by the pressure-resistant properties of the pressure-resistant layer (5), which is then at least partially removed from the effective layer (3).

2. 2. The method according to claim 1, characterized in that the pressure-resistant layer (5) comprises a film, in particular made of polyester, as the main material component.

3. 3. The method according to claim 1 or 2, characterized in that the pressure-resistant layer (5) comprises a film that is in particular biaxially pre-stretched.

4. 3. The method according to claim 1 or 2, characterized in that the pressure-resistant layer (5) is locally or partially removed and / or modified before and / or during heating.

5. 3. A method according to claim 1 or 2, characterized in that a plurality of, in particular different, pressure-resistant layers (5) are applied onto the useful layer (3).

6. 3. A method according to claim 1 or 2, characterized in that the material thickness (D) of the effective layer (3) is reduced to a material thickness (d) by expansion of the hollow microspheres (4).

7. 3. The method according to claim 1 or 2, characterized in that the energy of the radiation (7) passing through the pressure-resistant layer (5) acts selectively differently, in particular with different parameters, on different, mutually delimited regions and / or different cross-sectional levels of the useful layer (3) and / or the functional layer (6) of the surface-area element (1), so that the hollow microspheres (4) are expanded differently in different regions and cross-sectional levels of the surface-area element (1).

8. 3. The method according to claim 1 or 2, characterized in that the energy input is achieved by electromagnetic radiation (7), in particular in the infrared spectrum (IR), and is configured in such a way that at least individual regions and / or cross-sectional levels of the effective layer (3) are heated and the pressure-resistant layer (5) is penetrated at least substantially without heating by the radiation (7).

9. A flexible surface-area element (1) with at least one effective layer (3) produced by the method of claim 1, by expanding hollow microspheres of the surface-area element (1) against a pressure-resistant layer (5) and then locally removing at least the pressure-resistant layer (5), The surface-area element (1) is characterized in that, in addition to at least one thermoplastic effective layer, the surface-area element comprises a functional layer and at least one tension element, so that the effective layer containing hollow microspheres absorbs no or only little tension forces during operation.

10. 10. The surface-area element (1) according to claim 9, characterized in that at least one pressure-resistant layer (5) comprises cutouts or perforations.

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