Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B08—CLEANING
  • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
  • B08B17/00—Methods preventing fouling
  • B08B17/02—Preventing deposition of fouling or of dust
  • B08B17/06—Preventing deposition of fouling or of dust by giving articles subject to fouling a special shape or arrangement
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B08—CLEANING
  • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
  • B08B17/00—Methods preventing fouling
  • B08B17/02—Preventing deposition of fouling or of dust
  • B08B17/06—Preventing deposition of fouling or of dust by giving articles subject to fouling a special shape or arrangement
  • B08B17/065—Preventing deposition of fouling or of dust by giving articles subject to fouling a special shape or arrangement the surface having a microscopic surface pattern to achieve the same effect as a lotus flower
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24355—Continuous and nonuniform or irregular surface on layer or component [e.g., roofing, etc.]
  • Y10T428/24372—Particulate matter
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/25—Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles

Definitions

• the present invention relates to a method for producing surfaces with self-cleaning properties by means of a method for flame powder coating.
• the state of the art for self-cleaning surfaces is that an aspect ratio of> 1 and a surface energy of less than 20 mN / m is required for such self-cleaning surfaces.
• the aspect ratio is defined here as the quotient of the medium height to the medium width of the structure.
• the aforementioned criteria are realized in nature, for example in the lotus leaf.
• the surface of a plant formed from a hydrophobic, wax-like material has elevations that are up to a few ⁇ m apart. Water drops essentially only come into contact with the tips of the elevations. Such water-repellent surfaces are widely described in the literature.
• particulate systems which are based on nanoparticles with a very hydrophobic surface, as described, for example, in DE 101 29 116, DE 101 38 036 and DE 101 34477.
• the nanoparticles are bonded to the substrate either a) through a carrier layer or b) through a direct incorporation of the particles into the polymer / substrate.
• Electrostatic powder coating processes were also used in the processes mentioned.
• such methods have been used in the production of self-cleaning surfaces using a carrier layer, the powder particles being applied to the moist adhesive by means of electrostatic coating.
• this method was also used to dust the nanoparticles onto a moistened (usually with alcohol) surface. All these methods have in common that the workpiece is moistened. This makes it necessary that a very complex drying must be followed. This is a problem particularly in the case of textile webs.
• the evaporating solvents (alcohols) represent an environmental problem. The task was therefore to develop a method with which nanoparticles can be applied dry to the workpieces.
• the present invention relates to a method for producing surfaces with self-cleaning properties by applying particles to the surface and fixing the particles in the surface, which results in elevations that do a distance of 20 to 100 ⁇ m and a height of 20 nm to 100 ⁇ m have, are formed, which is characterized in that the application of the particles is carried out by spraying the particles by means of a hot air stream which has a temperature which softens the material of the surface to be treated to such an extent that the circumference of the particles at least partially in the material of the surface can penetrate and that the particles that have at least partially penetrated into the material of the surface are fixed in the surface when the substrate cools.
• the present invention relates to self-cleaning surfaces produced by means of the method according to the invention and objects with a surface according to the invention and the use of the method according to the invention for coating objects which are exposed to high levels of dirt and water, in particular for the outdoor area, skiing, alpine sports , Motorsport, motorcycle sport, motor cross sport, sailing sport, textiles for the leisure area as well as for the coating of technical textiles, selected from tents, awnings, umbrellas, tablecloths, convertible tops, technical textiles or work clothes.
• the method according to the invention has the advantage that particles can be applied to surfaces to produce self-cleaning surfaces without the use of solvents.
• the particles are superbly fixed on or in the surface, since the particles are firmly anchored in the surface when the material solidifies.
• Further advantages of the method according to the invention consist in the fact that it can be easily integrated into existing systems and allows a high web speed especially in textile production and finishing. In particular in the textile industry, flame processes are already established, which is why the process according to the invention can be integrated particularly easily in the textile industry.
• the method according to the invention for producing surfaces with self-cleaning properties and the surfaces according to the invention are described below by way of example, without the invention being restricted to these.
• the process is based on the principle of the flame spray process.
• powder that is supplied with part of the combustion air is rendered molten in the flame and thrown onto the surface by the combustion gases.
• the method is modified in such a way that nanoparticles or particles are used which only change into a liquid phase at a very high temperature.
• the heat of the flame does not render the powder molten, but the substrate to be treated or the material on the surface of the substrate.
• the nanoparticles are deposited in the surface of the melted substrate and are fixed in it when they cool down.
• the method according to the invention for producing surfaces with self-cleaning properties by applying particles to the surface and fixing the particles in the surface, as a result of which elevations are formed which are at a distance of 20 nm to 100 ⁇ m and a height of 20 nm to 100 ⁇ m , is characterized in that the particles are applied by spraying the particles by means of a hot air stream or a flame.
• the temperature of the air flow or flame must be selected so that the particles used are not thermally damaged, but the flame or air flow acts on the material so strongly that the material surface is heated above its glass transition temperature Tg, and so the material of the surface to be treated is softened to such an extent that the circumference of the particles can at least partially penetrate into the surface material and that the particles that have at least partially penetrated into the surface material are fixed in the surface when the substrate cools.
• the material Depending on the viscosity and material of the substrate, the material must be melted or just be plasticized. The required degree of softening can easily be determined by simple preliminary tests for the respective material.
• surfaces with elevations with an average height of 50 nm to 10 ⁇ m and / or an average distance of 50 nm to 10 ⁇ m and very particularly preferably with an average height of 50 nm to 4 ⁇ m and / or an average distance of 50 nm are preferred down to 4 ⁇ m.
• surfaces produced using the method according to the invention have elevations with an average height of 0.25 to 1 ⁇ m and an average distance of 0.25 to 1 ⁇ m.
• the mean distance between the elevations is understood to mean the distance between the highest elevation of one elevation and the next highest elevation. If an elevation has the shape of a cone, the tip of the cone represents the highest elevation of the elevation. If the elevation is a cuboid, the top surface of the cuboid represents the highest elevation of the elevation.
• the process according to the invention can preferably be used to provide substrates with a self-cleaning surface which, as the surface material, is a material selected from thermoplastics, such as, for example, Polyolefins, vinyl polymers, polyamides, polyesters, polyacetals or polycarbonates or low-melting metals or alloys selected from tin, lead, Wood's metal, gallium or soft solder.
• the substrate itself or the surface can be the surface of a film, a three-dimensional object or a shaped body, flat fabric or a membrane.
• the temperature of the hot air flow required for the respective material can be generated electrically or by combustion (also catalytic) of combustible gases. Suitable devices can work according to the principle of the flame spray gun. However, modified hot air blowers are also suitable, which have a possibility of adding particles to the hot air flow. Typical airflow temperatures range from 35 to 3150 ° C. Air flow temperatures are preferably in the range from 50 to 1250 ° C., preferably 90 to 900 ° C. and very particularly preferably from 90 to 500 ° C. It can be advantageous if the hot air flow generates a near-surface heating that is significantly above the glass transition temperature of the surface material. This heating should preferably be very limited locally in order to prevent deformation of the surface. For generation of locally limited hot air flows, flames from gas burners in particular have proven to be suitable.
• the surface temperature of the particles used can be blown into the flame or the air stream when they are cooled. Such an approach also reduces the airflow or flame temperature.
• the surface temperature of the material to be coated can not only on the air flow or. Flame temperature or the distance of the flame or the air flow to the surface but also via the dwell time of the surface under the air flow or flame.
• the particles can be added to the air stream before or after it is heated.
• the particles are preferably added to the air stream before the air stream is heated.
• the particles can be added using the suction jet principle.
• FIG. 2 The principle of a flame spray gun is shown in FIG. 2.
• the manufacturer of suitable flame spray guns is e.g. the Baumann Plasma Flame Technic AG company in Switzerland.
• the penetration depth can be determined as a function of the viscosity of the material of the surface when the particles strike the surface by means of the flow velocity of the hot air flow and thus the velocity of the particles therein.
• Typical gas velocities are eg 1000 to 5000 m / s.
• the particle speed is usually much slower and can be, for example, from 20 m / s to 600 m / s.
• the speed of the particles before they hit the surface to be treated is preferably from 30 m / s to 200 m / s.
• the temperature of the air flow and the speed of the air flow or the particles are preferably adjusted such that the particles are 10 to 90%, preferably 20 to 50% and very particularly preferably penetrate from 30 to 40% of their average particle diameter into the surface and are thus firmly anchored in the surface after the material has cooled.
• the particles used can be those which have at least one material selected from silicates, minerals, metal oxides, metal powders, silicas, pigments or high-temperature-resistant (HT) polymers.
• the particles can particularly preferably contain silicates, doped silicates, minerals, metal oxides, aluminum oxide, silicas or aerosils or powdery polymers, such as e.g. spray-dried and agglomerated emulsions or cryomilled PTFE.
• Particles which have hydrophobic properties are preferably used.
• Silicas are particularly preferably used as hydrophobic particles.
• Particles are preferably used which have an average particle diameter of 0.02 to 100 ⁇ m, particularly preferably from 0.01 to 50 ⁇ m and very particularly preferably from 0.1 to 30 ⁇ m. However, particles which are composed of primary particles to form agglomerates or aggregates with a size of 0.2 to 100 ⁇ m are also suitable.
• the particles used have a structured surface.
• Particles which have an irregular fine structure in the nanometer range that is to say in the range from 1 to 1000 nm, preferably from 2 to 750 nm and very particularly preferably from 10 to 100 nm, are preferably used on the surface.
• Fine structure is understood to mean structures which have heights, widths and distances in the areas mentioned.
• Such particles preferably have at least one compound selected from pyrogenic silica, precipitated silica, aluminum oxide, silicon dioxide, pyrogenic and / or doped silicates or powdery high-temperature-resistant polymers.
• the particles with the irregular, airy, fissured fine structure in the nanometer range preferably have elevations with an aspect ratio in the fine structures of greater than 1, particularly preferably greater than 1.5.
• the aspect ratio is defined as the quotient from the maximum height to the maximum width of the survey.
• FIG. 1 The difference between the elevations formed by the particles and the elevations formed by the fine structure is illustrated schematically in FIG. 1.
• the figure shows the surface of a substrate X which has particles P (to simplify the illustration there is only one particle ) Displayed.
• the elevation formed by the particle itself has an aspect ratio of approx.
• a selected elevation of the elevations E, which are present on the particles due to the fine structure of the particles has an aspect ratio of 2.5, calculated as a quotient from the maximum height of the elevation mH ′, which is 2.5 and the maximum width mB ', which is 1 in proportion.
• the hydrophobic properties of the particles may be inherent due to the material used for the particles, such as, for example, in the case of polytetrafluoroethylene (PTFE).
• PTFE polytetrafluoroethylene
• hydrophobic particles which, after suitable treatment, have hydrophobic properties, such as particles treated with at least one compound from the group of the alkylsilanes, the fluoroalkylsilanes or the disilazanes.
• Particularly suitable particles are hydrophobicized pyrogenic silicas, so-called aerosils. Examples of hydrophobic particles are e.g. Aerosil VPR 411 or Aerosil R 8200.
• particles which can be rendered hydrophobic by treatment with perfluoroalkylsilane and subsequent heat treatment are, for example Aeroperl 90/30, Sipernat silica 350, aluminum oxide C, zirconium silicate, vanadium-doped or VP Aeroperl 25/20.
• the use of such hydrophobized particles is usually possible without problems up to a temperature of 350 ° C. without the hydrophobicity being significantly impaired.
• particles, in particular as particles, which have an irregular fine structure in the nanometer range on the surface those particles are preferably used which have at least one compound selected from pyrogenic silica, aluminum oxide, silicon oxide or powdered HT polymers or metals. It can be advantageous if the particles used have hydrophobic properties.
• Particularly suitable particles are, inter alia, hydrophobicized pyrogenic silicas, so-called aerosils.
• particles which have hydrophobic properties.
• the hydrophobic properties of the particles may be inherent due to the material used for the particles.
• hydrophobized particles can also be used which, for example by treatment with at least one compound from the group of the alkylsilanes, perfluoroalkylsilanes, paraffins, waxes, fatty acid esters, functionalized long-chain alkane derivatives or alkyldisilazanes, have hydrophobic properties.
• the method according to the invention can be used to produce self-cleaning surfaces which preferably have elevations formed from particles, the elevations being at a distance of 20 nm to 100 ⁇ m and a height of 20 nm to 100 ⁇ m.
• the surfaces according to the invention preferably have at least one layer with elevations with an average height of 20 nm to 25 ⁇ m and an average distance of
• the surfaces according to the invention very particularly preferably have elevations with an average height of 0.25 to 1 ⁇ m and an average distance of 0.25 to 1 ⁇ m.
• the mean distance between the elevations is understood to mean the distance between the highest elevation of one elevation and the next highest elevation.
• Elevation If the elevation is a cuboid, the top surface of the cuboid represents the highest elevation of the elevation.
• a layer of elevations or particles is understood to mean a collection of particles on the surface which form elevations.
• the layer can be formed in such a way that the surface has only particles, almost exclusively particles or else particles at a distance of 0 to 10, in particular 0 to 3, particle diameters from one another.
• the surfaces according to the invention with self-cleaning properties preferably have an aspect ratio of the elevations of greater than 0.15.
• the elevations which are formed by the particles themselves themselves preferably have an aspect ratio of 0.3 to 0.9, particularly preferably 0.5 to 0.8. The aspect ratio is defined as the quotient from the maximum height to the maximum width of the structure of the surveys.
• the surfaces according to the invention which have self-cleaning properties and surface structures with elevations, are characterized in that the surfaces are materials which can be softened or melted by heat and solidify on cooling, into which the particles are directly integrated or anchored and are not connected via carrier systems or the like are.
• the particles are bound or anchored to the surface by at least partially pressing the particles into the softened or melted material when the air stream hits it.
• the particles preferably more than 50% of the particles, preferably only up to 90% of their diameter, are pressed into the surface of the material.
• the surface therefore preferably has particles which are anchored in the surface with 10 to 90%, preferably 20 to 50% and very particularly preferably 30 to 40% of their mean particle diameter and thus still protrude from the surface with parts of their inherently fissured surface ,
• the aspect ratio is defined here as the ratio of the maximum height to the maximum width of the elevations.
• a particle assumed to be ideally spherical, which projects 70% from the surface of the injection molded body has an aspect ratio of 0.7. It should be explicitly pointed out that the particles according to the invention need not have a spherical shape.
• the wetting of bodies and thus the self-cleaning property can be described by the contact angle that a drop of water forms with the surface. A contact angle of 0 degrees means complete wetting of the surface.
• the static contact angle is generally measured using devices in which the contact angle is optically determined. Static contact angles of less than 125 ° are usually measured on smooth hydrophobic surfaces.
• the present self-cleaning surfaces have static contact angles of preferably greater than 130 °, preferably greater than 140 ° and very particularly preferably greater than 145 °. It was also found that a surface only has good self-cleaning properties if it has a difference between the advancing and retreating angles of at most 10 °, which is why surfaces according to the invention preferably have a difference between the advancing and retracting angles of less than 10 °, preferably less than 5 ° and very particularly preferably have less than 4 °.
• a drop of water is placed on the surface by means of a cannula and the drops on the surface are enlarged by adding water through the cannula.
• the edge of the drop glides over the surface and the contact angle is determined.
• the retraction angle is measured on the same drop, only the water is withdrawn from the drop through the cannula and the contact angle is measured while the drop is being reduced.
• the difference between the two angles is called hysteresis. The smaller the difference, the less the interaction of the water drop with the surface of the surface and the better the lotus effect.
• the surface according to the invention can be a surface of a textile, a film, a three-dimensional object, a truck tarpaulin or a membrane.
• the method according to the invention can be selected, for example, for the coating of objects which are exposed to high levels of dirt and water, in particular for the outdoor area, skiing, alpine sports, motor sports, motorcycle sports, motor cross sports, sailing, textiles for the leisure sector and for coating technical textiles Tents, awnings, umbrellas, tablecloths, convertible tops, technical textiles or work clothes can be used.
• Objects with a surface according to the invention can include, for example, foils, articles of daily use, sports articles, textiles, clothing and roofing underlay.
• FIG. 1 The difference between the elevations formed by the particles and the elevations formed by the fine structure is illustrated schematically in FIG. 1.
• the figure shows the surface of a substrate X which has particles P (only one particle is shown to simplify the illustration).
• the elevation formed by the particle itself has an aspect ratio of approx. 0.71, calculated as the quotient from the maximum height of the particle mH, which is 5, since only the part of the particle that contributes to the elevation protrudes from the surface of the injection molded body X, and the maximum width mB, which is 7 in relation to this.
• a selected elevation of the elevations E, which are present on the particles due to the fine structure of the particles has an aspect ratio of 2.5, calculated as a quotient from the maximum height of the elevation mH ′, which is 2.5 and the maximum width mB ', which is 1 in proportion.
• Fig. 2 shows schematically a flame spray head. This has a bromine gas supply BZ, a combustion chamber BK and a particle supply PZ.
• the flame FI which contains the particles, emerges from the combustion chamber. The particles present in the flame are carried by the air flow of the flame onto the surface of the material WS and fixed there after cooling.
• FIG. 3 and 4 show scanning electron microscope (SEM) images of a coated polypropylene plate produced according to Example 1 in different magnifications.
• the reference bar shown in the picture has a length of 100 ⁇ m in FIG. 3 and a length of 5 ⁇ m in FIG. 4.
• a polypropylene plate measuring 0.1 mx 0.1 mx 0.005 m was treated with a propane flame. Aerosil R 8200 from Degussa AG was used as the particle. The flame temperature was 500 - 1200 ° C. The air flow speed for the particle transport was approx. 120 m / s. The treatment was carried out by first directing the flame onto the polypropylene plate for about 5 seconds. After these 5 seconds, particles (10 g / s) were added to the flame for 2 seconds. After this treatment, the flame was turned off and the plate was cooled to room temperature and examined.
• FIGS. 3 and 4 show SEM images of the polypropylene sheet treated in this way in different resolutions. The behavior of the treated polypropylene was then characterized. The treated plate showed a very good lotus effect. Water droplets dripped off very well.
• the roll-off angle i.e. the angle to the horizontal at which a drop rolls off independently, was 5 ° for a 60 ⁇ l water drop and the angle of progression of a water drop pipetted onto the surface was 131.3 °, the retraction angle was 120.6 °.

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• Application Of Or Painting With Fluid Materials (AREA)
• Chemical Or Physical Treatment Of Fibers (AREA)
• Laminated Bodies (AREA)
• Materials Applied To Surfaces To Minimize Adherence Of Mist Or Water (AREA)
• Soil Working Implements (AREA)
• Coating By Spraying Or Casting (AREA)
• Paints Or Removers (AREA)

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• 2002
  • 2002-07-25 DE DE10233830A patent/DE10233830A1/de not_active Withdrawn
• 2003
  • 2003-06-25 WO PCT/EP2003/006681 patent/WO2004015022A1/fr not_active Ceased
  • 2003-06-25 AT AT03783985T patent/ATE348866T1/de not_active IP Right Cessation
  • 2003-06-25 ES ES03783985T patent/ES2279207T3/es not_active Expired - Lifetime
  • 2003-06-25 JP JP2004526699A patent/JP4273076B2/ja not_active Expired - Fee Related
  • 2003-06-25 AU AU2003249873A patent/AU2003249873A1/en not_active Abandoned
  • 2003-06-25 DE DE50306053T patent/DE50306053D1/de not_active Expired - Fee Related
  • 2003-06-25 US US10/519,951 patent/US20050227045A1/en not_active Abandoned
  • 2003-06-25 EP EP03783985A patent/EP1525285B1/fr not_active Expired - Lifetime
• 2008
  • 2008-11-25 US US12/277,658 patent/US20090123659A1/en not_active Abandoned

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