CA2381743A1 - Surfaces which are self-cleaning by hydrophobic structures, and a process for their production - Google Patents
Surfaces which are self-cleaning by hydrophobic structures, and a process for their production Download PDFInfo
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- CA2381743A1 CA2381743A1 CA002381743A CA2381743A CA2381743A1 CA 2381743 A1 CA2381743 A1 CA 2381743A1 CA 002381743 A CA002381743 A CA 002381743A CA 2381743 A CA2381743 A CA 2381743A CA 2381743 A1 CA2381743 A1 CA 2381743A1
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/12—Bonding of a preformed macromolecular material to the same or other solid material such as metal, glass, leather, e.g. using adhesives
- C08J5/122—Bonding of a preformed macromolecular material to the same or other solid material such as metal, glass, leather, e.g. using adhesives using low molecular chemically inert solvents, swelling or softening agents
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
- B05D5/08—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain an anti-friction or anti-adhesive surface
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
- B05D7/02—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to macromolecular substances, e.g. rubber
-
- 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
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C59/00—Surface shaping of articles, e.g. embossing; Apparatus therefor
- B29C59/02—Surface shaping of articles, e.g. embossing; Apparatus therefor by mechanical means, e.g. pressing
- B29C2059/028—Incorporating particles by impact in the surface, e.g. using fluid jets or explosive forces to implant particles
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- 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
Abstract
Disclosed is a process for producing objects having self-cleaning surfaces based on polymer surfaces to which particles have been secured. The polymer surfaces used here are treated with a solvent which comprises the particles. This treatment solvates the polymer surfaces while the particles, which are not solvated, deposit on the solvated polymer surface. Removal/evaporation of the solvent secures at least some part of the particles, since the polymer surface hardens again once the solvent has been removed, and some of the particles remain in the polymer surface. Using the process of the invention it is possible to give a self-cleaning surface to any object which can be provided with a polymer surface.
Description
Surfaces v~rhich are self-cleaning by hydrophobic structures and a process for their production FIELD OF THE INVENTION
The present invention relates to surfaces which obtain an effective self-cleaning action by virtue of the introduction of hydrophobic particulate systems into a carrier material. The surface energy of these surfaces is very low. The invention describes a process for firm bonding of the particulate systems into the bulk material within polymer surfaces.
BACKGROUND
1 o It is known that if effective self-cleaning is to be obtained on an industrial surface, the surface must not only be very hydrophobic but also have a certain roughness. Suitable combinations of structure and hydrophobic properties permit even small amounts of water moving over the surface to entrain adherent dirt particles and thus clean the surface (see WO 96/04123; and U.S. Patent No. 3,354,022).
EP 0 933 388 describes that self-cleaning surfaces of this type require an aspect ratio of at least 1 and a surface energy of less than 20 mN/m. The aspect ratio here is defined as the ~otient of the height of the structure to its width. The above-mentioned criteria are satisfied in the natural world, for example on a lotus leaf. The surface of the plant, formed from a hydrophobic waxy material, has elevations separated from one another by a few ~,m. Water droplets essentially come into contact only with these peaks. There are many descriptions in the literature of water-repellant surfaces of this type.
Swiss Patent 268 258 describes a process which can produce structured surfaces by applying powders, such as kaolin, talc, clay or silica gel. The 3o powders are secured to the surface by oils and resins based on organosilicon compounds (Examples 1 to 6). However, there is no description in that patent specification of the particle size distribution or , the manner of introduction of the particles into the matrix.
EP 0 909 747 A1 teaches a process for producing a self-cleaning surface.
The surface has hydrophobic elevations of height from 5 to 200 Vim. A
surface of this type is produced by applying a dispersion of powder particles and of an inert material in a siloxane solution, followed by curing.
The present invention relates to surfaces which obtain an effective self-cleaning action by virtue of the introduction of hydrophobic particulate systems into a carrier material. The surface energy of these surfaces is very low. The invention describes a process for firm bonding of the particulate systems into the bulk material within polymer surfaces.
BACKGROUND
1 o It is known that if effective self-cleaning is to be obtained on an industrial surface, the surface must not only be very hydrophobic but also have a certain roughness. Suitable combinations of structure and hydrophobic properties permit even small amounts of water moving over the surface to entrain adherent dirt particles and thus clean the surface (see WO 96/04123; and U.S. Patent No. 3,354,022).
EP 0 933 388 describes that self-cleaning surfaces of this type require an aspect ratio of at least 1 and a surface energy of less than 20 mN/m. The aspect ratio here is defined as the ~otient of the height of the structure to its width. The above-mentioned criteria are satisfied in the natural world, for example on a lotus leaf. The surface of the plant, formed from a hydrophobic waxy material, has elevations separated from one another by a few ~,m. Water droplets essentially come into contact only with these peaks. There are many descriptions in the literature of water-repellant surfaces of this type.
Swiss Patent 268 258 describes a process which can produce structured surfaces by applying powders, such as kaolin, talc, clay or silica gel. The 3o powders are secured to the surface by oils and resins based on organosilicon compounds (Examples 1 to 6). However, there is no description in that patent specification of the particle size distribution or , the manner of introduction of the particles into the matrix.
EP 0 909 747 A1 teaches a process for producing a self-cleaning surface.
The surface has hydrophobic elevations of height from 5 to 200 Vim. A
surface of this type is produced by applying a dispersion of powder particles and of an inert material in a siloxane solution, followed by curing.
The structure-forming particles are therefore secured to the substrate by an auxiliary medium.
Processes for producing structured surfaces in polymers are likewise known. Besides the use of a master structure to give precise reproduction of these structures by injection molding or embossing processes, there are other known processes which utilize the application of particles to a surface, e.g. in U.S. Patent No. 5,599,489.
This process, too, again utilizes an adhesion-promoting layer between particles and bulk material. Processes 1 o suitable for developing the structures are etching and coating processes for adhesive application of the structure-forming powders, and also shaping processes using appropriately structured negative molds.
However, a common feature of all of these processes is that an adhesion promoter between carrier and particle system is used when applying particulate systems. There are many technical problems with the use of an adhesion promoter of this type. Firstly, the particles frequently become immersed in the adhesion promoter and thus can no longer provide the desired effect. Secondly, there are very few industrial systems available 2 U for the abrasion-resistant bonding of a hydrophobic primary particle into a material.
It was therefore an object of the present invention to describe a process which, without adhesion promoters, can bond particulate systems or particles into the surface of various polymers.
2:. SUMMARY
Surprisingly, it has been found that brief immersion of polymer surfaces into solvents or treatct~nt of the polymer surfaces with solvent which comprise particles of the desired size can solvate an uppermost layer of the polymer surfaces and firmly bond the 3U particles present in the solvent to the surface of the polymers.
Once the solvent has been removed from the surface, for example, by evaporation/drying, the particulate systems (i.e. the particles) have become firmly anchored to the surface of the material.
The present invention therefore provides a process for producing obj acts 3 ~~ having self-cleaning surfaces, in which a suitable, at least to some extent hydrophobic, surtace structure is created by securing particles on a polymer surface, which comprises applying, to the polymer surface, at least one solvent which comprises the particles and which solvates the polymer surface, and securing same part of the particles to the polymer surface by removing the solvent.
The present invention also provides objects having self-cleaning polymer surfaces produced by the process mentioned above and having an artificial, at least to some extent hydrophobic, surface structure made from elevations and depressions, wherein the elevations and depressions are formed by particles secured to the polymer surface.
The process of the invention has the advantage 1Q that the particles can be bonded directly into a polymer surface and do not have to be secured to a surface by way of an auxiliary, e.g. an adhesive. Surfaces with self-cleaning properties can thus be provided without any need to consider the incompatibility of the surface with the auxiliary used.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a scanning electron micrograph (SEM) of the self-cleaning lotus surface created by the process of Example 1; and Fig. 2 is a similar SEM of the self-cleaning lotus surface created by the process of Example 2.
DESCRIPTION OF PREFERRED EMBODIMENTS
The process of the invention for producing self-cleaning surfaces in which a suitable, at least to some extent hydrophobic, surface structure is created by securing particles on a polymer surface is based on applying, to the polymer surface, at least one solvent which comprises the particles and which solvates the polymer surface, and securing some part of the particles to the polymer surface by removing the solvent. The solvation of the polymer surface softens this surface, and at least some part of the particles can sink into the solvated surface. Once the solvent has been removed, the polymer surface hardens again, and the particles, at least some part of which has/have sunk into the polymer surface, have become secured to the polymer surface (i.e., the particles are partially embedded in the polymer surface).
"At least to some extent hydrophobic" may refer to the fact that the whole of the surface need not be covered by hydrophobic structure-forming particles or that the whole of the surface be hydrophobicized. Preferably, greater than 50~ of the surface area has hydrophobic properties.
"At least to some extent hydrophobic" also refers to a surface having an average free surface energy of less than 30 ergs/cm2 and preferably less than 25 ergs/cm2.
By reference to "at least some part" of the particles sinking into the solvated surface or sunk into the solvated surface, it will be clear to a person skilled in the art that the whole of the particles have not been sunk into the surface.
The particles used may be those which comprise at least one material selected from silicates, doped or fumed silicates (e. g., Aerosils*), minerals (e. g. magadiite), metal oxides (e.g. A12O3, Ti02, and Zr02) , silicas, and polymers (e. g. polytetrafluoroethylene (PTFE), perfluorinated copolymers, or copolymers with tetrafluoroethylene). The particles used are preferably those which have a particle diameter of from 0.02 to 100 ~.m, particularly preferably from 0.2 to 50 Vim, and very particularly preferably from 0.3 to ~.m. The separations of the individual particles on the self-cleaning surfaces are from 0 to 10 particle diameters, 30 in particular from 2 to 3 particle diameters.
*Trade-mark - 4a -The particles present may also be in the form of aggregates or agglomerates, where according to DIN 53 206 aggregates have primary particles in edge- or surface-contact, while agglomerates have primary particles in point-s contact. The particles used may also be those composed of primary particles giving agglomerates or aggregates with a size of from 0.2 to 100 ~,m.
Tt can be advantageous for the particles used to have a structured surface. The particles used preferably have an irregular fine structure in the manometer range on the surface. The very fine structure of the particles is preferably a fitted structure with elevations and/or depressions in the manometer range. The average height of the elevations is preferably from 20 to 500 mm, particularly preferably from 50 to 200 mm. The separation of the elevations and, respectively, depressions on the particles is preferably less than 500 mm, very particularly preferably less than 200 mm.
The particles used, in particular the particles which have an irregular fine structure in the manometer range on the surface, are preferably ones which comprise at least one compound selected from fumed silica, aluminum oxide, silicon oxide, fumed silicates, and pulverulent polymers. It can be advantageous for the particles used to have hydrophobic properties. Particles which are very particularly suitable, inter alia, are hydrophobicized fumed silicas, known as Aerosils.
Where the particles used have a structured surface, particularly an irregular fine structure in the manometer range, care must be taken that the solvent is removed to the extent that the particles do not remain wet, - 4b -destroying the structured surface or the irregular fine structure in the manometer range.
The hydrophobic properties of the particles may be inherently present by virtue of the material used for the particles. However, it is also possible to use hydrophobicized particles which have hydrophobic properties by virtue of, for example, treatment with at least one hydrophobicizing compound selected from the group consisting of the alkylsilanes, perfluoroalkylsilanes, paraffins, 1C waxes, fatty esters, functionalized long-chain alkane derivatives, and alkyldisilazanes.
For the process of the present invention it is also possible for the particles to be given hydrophobic properties after securing to the carrier. In this case, too, the particles are preferably given hydrophobic properties by virtue of treatment with at least one compound selected from the group consisting of the alkylsilanes, perfluoroalkylsilanes, paraffins, waxes, fatty esters, functionalized long-chain alkane derivatives, and alkyldisilazanes.
The solvent which comprises the particles preferably comprises these in suspended form. The solvents used may be any of the solvents which are capable of solvating the appropriate polymer present in the polymer surface. Suitable solvents for these applications are in principle any of the solvents for the polymers concerned. An example of a finite, but not comprehensive, list is in Polymer Handbook, Second Edition; J. Bandrup, E.H. Immergut; in Chapter IV, Solvents and Non-Solvents for Polymers, for example. This list includes other polymers not listed below and their solvents, which would be suitable for use in the present invention.
The solvent used is preferably at least one compound suitable as a solvent 1 U for the appropriate polymer and selected from the group consisting of the alcohols, the glycols, the ethers, the glycol ethers, the ketones, the esters, the amides, the aliphatic hydrocarbons, the aromatic hydrocarbons, the vitro compounds, the organic nitrogen compounds, the organic sulfur compounds, and/or the halogenated hydrocarbons, or a mixture of two or more of these compounds. The solvent used is very particularly 15. preferably at feast one compound suitable as a solvent for the appropriate polymer 2nd selected from methanol, ethanol, propanol, butanol, octanol, cyclohexanol, phenol, cresol, ethylene glycol, diethylene glycol, diethyl ether, dibutyl ether, anisole, dioxane, dioxolane, tetrahydrofuran, monoethylene glycol ether, diethylene glycol ether, triethylene glycol 2U ether, polyethylene glycol ether, acetone, butanone, cyclohexanone, ethyl acetate, butyl acetate, isoamyl acetate, ethylhexyl acetate, glycol esters, dimethylformamide, pyridine, N-methylpyrrolidone, N-methylcaprolactone, acetonitrile, carbon disulfide, dimethyl sulfoxide, suifolane, nitrobenzene, dichloromethane, chloroform, tetrachloromethane, trichloroethene, 25 tetrachloroethene, 1,2-dichloroethane, chlorophenol, chlorofluorohydrocarbons, petroleum spirits, petroleum ethers, cyclohexane, methylcyclohexane, decalin, tetralin, terpenes, benzene, toluene, andlor xylene, or a mixture made from two or more of these compounds suitable as solvents.
Use of the various solvents permits the use of almost any polymer as polymer surface. The decisive factor in selecting the solvent is that the particulate system is not attacked by the solvent whereas the polymer system is solvated.
A very wide variety of common polymers may form the polymer surface.
The polymer forming the polymer surface is preferably at least one polymer selected from polycarbonates, polyacrylonitriles, poly(meth)-- 6 - O.Z. 5751 acrylates, polyamides, PVC, polyethylenes, polyalkyiene terephthalates, polypropylenes, polystyrenes, polyesters, and polyether sulfones, and also mixtures and copolymers of these, where the monomers for the copolymers may also come from other classes of monomer.
The solvent which comprises the particles may be applied at room temperature to the polymer surface. In one particularly preferred embodiment of the process of the invention, the solvent which comprises the particles is heated, prior to application to the polymer surface, to a 1 o temperature of from -30 to 300°C, preferably from 25 to 100°C, preferably to a temperature of from 50 to 85°C.
The application of the solvent comprising the particles to the polymer surface may be by spray-application, doctor-application, drop-application, or by dipping the polymer surface into the solvent comprising the particles, for example.
The number of particles introduced onto the surface can be regulated via the concentration of particles in the solvent and the temperature of the 2 o solvent, and also via the immersion time. The rule here is that the longer the contact time and the more suitable the solvent, the greater the number of particles introduced into the polymer. However, the disadvantage of a long contact time is that not only does the uppermost layer of the polymer become solvated but other more deep-lying polymer layers become 2 5 solvated or swollen. This can lead to undesirable complete destruction of the polymer. Dimensional change in polymeric moldings can also occur.
The following parameters have proven particularly suitable. The concentration of the primary particles in the solvent is preferably from 0.1 to 20% by weight, particularly preferably from 1 to 12% by weight, and very 3 o particularly preferably from 1 to 7% by weight. The contact times are highly dependent on the solvent and the temperature. The contact time is preferably from 1 sec to 75 min, particularly preferably from 1 sec to 1 min, and very particularly preferably from 1 sec to 10 sec. However, short contact times and, where appropriate, repeated dipping of the specimen 35 has proven successful for avoiding distortion of the external shape of the polymeric molding. An ultrasound bath may be used to deagglomerate the agglomerated particles, and the particles can be kept suspended by continuous stirring.
_ 7 _ The process of the invention can produce a self-cleaning polymer surface which has an artificial, at least to some extent hydrophobic, surface structure made from elevations and depressions, where the elevations and depressions are formed by particles secured to the polymer surf ace .
The self-cleaning polymer surfaces of the invention have particles of a material selected from silicates, doped silicates, minerals, metal oxides, silicas, 1C fumed silicas, precipitated silicas, metal powders, and polymers. The polymer surfaces also comprise at least one polymer selected from polycarbonates, poly(meth)acrylates, polyamides, PVC, polyethylenes, polypropylenes, polystyrenes, polyesters, and polyether sulfones, and their mixtures and copolymers. The particles secured to the polymer surface preferably have an average particle diameter of from 0.02 to 100 ~,m, preferably from 0.2 to 50 ~cm, and particularly preferably from 0.3 to 30 Vim. The particles may also be present in the form of aggregates or agglomerates, where in accordance with DIN 53 206 aggregates have primary particles in edge- or surface-contact, while agglomerates have primary particles in point-contact. The separations of the individual particles on the self-cleaning surfaces are from 0 to 10 particle diameters, in particular from 2 to 3 particle diameters.
In one very particularly preferred embodiment, the self-cleaning polymer surface of the invention comprises particles which have an irregular fine structure in the nanometer range on the surface. The presence of a fine structure in the nanometer range on the surface of the particles achieves particularly effective self-cleaning action, since the separation of the elevations and - 7a -depressions is not purely a function of the separation of the particles, and therefore of the particle size, but is also a function of the separation between the elevations and depressions on the particles. The average height of the elevations is preferably from 20 to 500 nm, particularly preferably from 50 to 200 nm. The separation of the elevations and, respectively, depressions on the particles is preferably less than 500 nm, very particularly preferably less than 200 nm.
The particles on the polymer surface of the invention preferably have hydrophobic properties. The hydrophobic properties of the polymer surface and of the particles achieves a surface structure which is at least to some extent hydrophobic and by way of which the self-15~ cleaning action of the surfaces can be increased as desired, since contamination on the surface can be removed by using small amounts of water, or automatically by rain (self-cleaning effect).
_ g _ The process of the invention can produce objects with a self-cleaning surface. These objects can be obtained by coating the object with at least one polymer in order to obtain a polymer surface where the object itself is not made of a polymer, and then securing particles to this polymer surface by means of a process of the invention.
Example 1: Self-cleaning surface based on a polypropylene surface Decalin is heated to a temperature of 80°C. The decalin comprises 3% by weight of fumed silica (Aerosil R 8200, Degussa AG). Aerosil R 8200 is a hydrophobicized fumed silica with a primary particle size distribution of from about 5 to 50 um. An ultrasound bath is used to deagglomerate agglomerated particles. The solution is kept continuously-stirred. A polypropylene sheet of dimensions 5 x 5 cm is dipped in the suspension for about 3 sec. Once the solvent has been dried off, the sheet is dipped for a second time in the suspension for 3 sec. Fig. 1 shows the resultant self-cleaning lotus surface. The scanning electron micrograph (SEM) clearly shows that the particles have been bonded into the polymer matrix. The resultant surface has the same chemical stability as the polypropylene and exhibits a very 2 o good lotus effect. Water droplets roll off at an angle of as little as 4°, and if the surface is soiled using carbon black, even very small amounts of water are sufficient to render the surface again completely free from carbon black.
Example 2: Self-cleaning surtace based on a polyester surface 3°~ by weight of fumed silica (Aerosil R 8200, Degussa AG) are suspended in hot dimethyl sulfoxide (DMSO). A commercially available polyester sheet of dimensions 5 x 5 cm is dipped in this solution for 5 sec.
3o Fig. 2 shows the primary particles bonded into the polyester. Here again, a very good self-cleaning effect (lotus effect) is observed. Water droplets roll off spontaneously at an angle as small as 14° and if the surface is soiled with carbon black even very small amounts of water are sufficient to render the surface again completely free from carbon black.
Figures 1 and 2 show the surfaces from the examples, produced according to the invention.
- 9 - O.Z. 5751 Fig. 1: SEM of a polypropylene sheet produced as in Example 1 with Aerosil R 8200.
Fig. 2: SEM of a polyester sheet comprising particles of fumed silica and produced by dipping the sheet into a DMSO solution comprising the particles.
Processes for producing structured surfaces in polymers are likewise known. Besides the use of a master structure to give precise reproduction of these structures by injection molding or embossing processes, there are other known processes which utilize the application of particles to a surface, e.g. in U.S. Patent No. 5,599,489.
This process, too, again utilizes an adhesion-promoting layer between particles and bulk material. Processes 1 o suitable for developing the structures are etching and coating processes for adhesive application of the structure-forming powders, and also shaping processes using appropriately structured negative molds.
However, a common feature of all of these processes is that an adhesion promoter between carrier and particle system is used when applying particulate systems. There are many technical problems with the use of an adhesion promoter of this type. Firstly, the particles frequently become immersed in the adhesion promoter and thus can no longer provide the desired effect. Secondly, there are very few industrial systems available 2 U for the abrasion-resistant bonding of a hydrophobic primary particle into a material.
It was therefore an object of the present invention to describe a process which, without adhesion promoters, can bond particulate systems or particles into the surface of various polymers.
2:. SUMMARY
Surprisingly, it has been found that brief immersion of polymer surfaces into solvents or treatct~nt of the polymer surfaces with solvent which comprise particles of the desired size can solvate an uppermost layer of the polymer surfaces and firmly bond the 3U particles present in the solvent to the surface of the polymers.
Once the solvent has been removed from the surface, for example, by evaporation/drying, the particulate systems (i.e. the particles) have become firmly anchored to the surface of the material.
The present invention therefore provides a process for producing obj acts 3 ~~ having self-cleaning surfaces, in which a suitable, at least to some extent hydrophobic, surtace structure is created by securing particles on a polymer surface, which comprises applying, to the polymer surface, at least one solvent which comprises the particles and which solvates the polymer surface, and securing same part of the particles to the polymer surface by removing the solvent.
The present invention also provides objects having self-cleaning polymer surfaces produced by the process mentioned above and having an artificial, at least to some extent hydrophobic, surface structure made from elevations and depressions, wherein the elevations and depressions are formed by particles secured to the polymer surface.
The process of the invention has the advantage 1Q that the particles can be bonded directly into a polymer surface and do not have to be secured to a surface by way of an auxiliary, e.g. an adhesive. Surfaces with self-cleaning properties can thus be provided without any need to consider the incompatibility of the surface with the auxiliary used.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a scanning electron micrograph (SEM) of the self-cleaning lotus surface created by the process of Example 1; and Fig. 2 is a similar SEM of the self-cleaning lotus surface created by the process of Example 2.
DESCRIPTION OF PREFERRED EMBODIMENTS
The process of the invention for producing self-cleaning surfaces in which a suitable, at least to some extent hydrophobic, surface structure is created by securing particles on a polymer surface is based on applying, to the polymer surface, at least one solvent which comprises the particles and which solvates the polymer surface, and securing some part of the particles to the polymer surface by removing the solvent. The solvation of the polymer surface softens this surface, and at least some part of the particles can sink into the solvated surface. Once the solvent has been removed, the polymer surface hardens again, and the particles, at least some part of which has/have sunk into the polymer surface, have become secured to the polymer surface (i.e., the particles are partially embedded in the polymer surface).
"At least to some extent hydrophobic" may refer to the fact that the whole of the surface need not be covered by hydrophobic structure-forming particles or that the whole of the surface be hydrophobicized. Preferably, greater than 50~ of the surface area has hydrophobic properties.
"At least to some extent hydrophobic" also refers to a surface having an average free surface energy of less than 30 ergs/cm2 and preferably less than 25 ergs/cm2.
By reference to "at least some part" of the particles sinking into the solvated surface or sunk into the solvated surface, it will be clear to a person skilled in the art that the whole of the particles have not been sunk into the surface.
The particles used may be those which comprise at least one material selected from silicates, doped or fumed silicates (e. g., Aerosils*), minerals (e. g. magadiite), metal oxides (e.g. A12O3, Ti02, and Zr02) , silicas, and polymers (e. g. polytetrafluoroethylene (PTFE), perfluorinated copolymers, or copolymers with tetrafluoroethylene). The particles used are preferably those which have a particle diameter of from 0.02 to 100 ~.m, particularly preferably from 0.2 to 50 Vim, and very particularly preferably from 0.3 to ~.m. The separations of the individual particles on the self-cleaning surfaces are from 0 to 10 particle diameters, 30 in particular from 2 to 3 particle diameters.
*Trade-mark - 4a -The particles present may also be in the form of aggregates or agglomerates, where according to DIN 53 206 aggregates have primary particles in edge- or surface-contact, while agglomerates have primary particles in point-s contact. The particles used may also be those composed of primary particles giving agglomerates or aggregates with a size of from 0.2 to 100 ~,m.
Tt can be advantageous for the particles used to have a structured surface. The particles used preferably have an irregular fine structure in the manometer range on the surface. The very fine structure of the particles is preferably a fitted structure with elevations and/or depressions in the manometer range. The average height of the elevations is preferably from 20 to 500 mm, particularly preferably from 50 to 200 mm. The separation of the elevations and, respectively, depressions on the particles is preferably less than 500 mm, very particularly preferably less than 200 mm.
The particles used, in particular the particles which have an irregular fine structure in the manometer range on the surface, are preferably ones which comprise at least one compound selected from fumed silica, aluminum oxide, silicon oxide, fumed silicates, and pulverulent polymers. It can be advantageous for the particles used to have hydrophobic properties. Particles which are very particularly suitable, inter alia, are hydrophobicized fumed silicas, known as Aerosils.
Where the particles used have a structured surface, particularly an irregular fine structure in the manometer range, care must be taken that the solvent is removed to the extent that the particles do not remain wet, - 4b -destroying the structured surface or the irregular fine structure in the manometer range.
The hydrophobic properties of the particles may be inherently present by virtue of the material used for the particles. However, it is also possible to use hydrophobicized particles which have hydrophobic properties by virtue of, for example, treatment with at least one hydrophobicizing compound selected from the group consisting of the alkylsilanes, perfluoroalkylsilanes, paraffins, 1C waxes, fatty esters, functionalized long-chain alkane derivatives, and alkyldisilazanes.
For the process of the present invention it is also possible for the particles to be given hydrophobic properties after securing to the carrier. In this case, too, the particles are preferably given hydrophobic properties by virtue of treatment with at least one compound selected from the group consisting of the alkylsilanes, perfluoroalkylsilanes, paraffins, waxes, fatty esters, functionalized long-chain alkane derivatives, and alkyldisilazanes.
The solvent which comprises the particles preferably comprises these in suspended form. The solvents used may be any of the solvents which are capable of solvating the appropriate polymer present in the polymer surface. Suitable solvents for these applications are in principle any of the solvents for the polymers concerned. An example of a finite, but not comprehensive, list is in Polymer Handbook, Second Edition; J. Bandrup, E.H. Immergut; in Chapter IV, Solvents and Non-Solvents for Polymers, for example. This list includes other polymers not listed below and their solvents, which would be suitable for use in the present invention.
The solvent used is preferably at least one compound suitable as a solvent 1 U for the appropriate polymer and selected from the group consisting of the alcohols, the glycols, the ethers, the glycol ethers, the ketones, the esters, the amides, the aliphatic hydrocarbons, the aromatic hydrocarbons, the vitro compounds, the organic nitrogen compounds, the organic sulfur compounds, and/or the halogenated hydrocarbons, or a mixture of two or more of these compounds. The solvent used is very particularly 15. preferably at feast one compound suitable as a solvent for the appropriate polymer 2nd selected from methanol, ethanol, propanol, butanol, octanol, cyclohexanol, phenol, cresol, ethylene glycol, diethylene glycol, diethyl ether, dibutyl ether, anisole, dioxane, dioxolane, tetrahydrofuran, monoethylene glycol ether, diethylene glycol ether, triethylene glycol 2U ether, polyethylene glycol ether, acetone, butanone, cyclohexanone, ethyl acetate, butyl acetate, isoamyl acetate, ethylhexyl acetate, glycol esters, dimethylformamide, pyridine, N-methylpyrrolidone, N-methylcaprolactone, acetonitrile, carbon disulfide, dimethyl sulfoxide, suifolane, nitrobenzene, dichloromethane, chloroform, tetrachloromethane, trichloroethene, 25 tetrachloroethene, 1,2-dichloroethane, chlorophenol, chlorofluorohydrocarbons, petroleum spirits, petroleum ethers, cyclohexane, methylcyclohexane, decalin, tetralin, terpenes, benzene, toluene, andlor xylene, or a mixture made from two or more of these compounds suitable as solvents.
Use of the various solvents permits the use of almost any polymer as polymer surface. The decisive factor in selecting the solvent is that the particulate system is not attacked by the solvent whereas the polymer system is solvated.
A very wide variety of common polymers may form the polymer surface.
The polymer forming the polymer surface is preferably at least one polymer selected from polycarbonates, polyacrylonitriles, poly(meth)-- 6 - O.Z. 5751 acrylates, polyamides, PVC, polyethylenes, polyalkyiene terephthalates, polypropylenes, polystyrenes, polyesters, and polyether sulfones, and also mixtures and copolymers of these, where the monomers for the copolymers may also come from other classes of monomer.
The solvent which comprises the particles may be applied at room temperature to the polymer surface. In one particularly preferred embodiment of the process of the invention, the solvent which comprises the particles is heated, prior to application to the polymer surface, to a 1 o temperature of from -30 to 300°C, preferably from 25 to 100°C, preferably to a temperature of from 50 to 85°C.
The application of the solvent comprising the particles to the polymer surface may be by spray-application, doctor-application, drop-application, or by dipping the polymer surface into the solvent comprising the particles, for example.
The number of particles introduced onto the surface can be regulated via the concentration of particles in the solvent and the temperature of the 2 o solvent, and also via the immersion time. The rule here is that the longer the contact time and the more suitable the solvent, the greater the number of particles introduced into the polymer. However, the disadvantage of a long contact time is that not only does the uppermost layer of the polymer become solvated but other more deep-lying polymer layers become 2 5 solvated or swollen. This can lead to undesirable complete destruction of the polymer. Dimensional change in polymeric moldings can also occur.
The following parameters have proven particularly suitable. The concentration of the primary particles in the solvent is preferably from 0.1 to 20% by weight, particularly preferably from 1 to 12% by weight, and very 3 o particularly preferably from 1 to 7% by weight. The contact times are highly dependent on the solvent and the temperature. The contact time is preferably from 1 sec to 75 min, particularly preferably from 1 sec to 1 min, and very particularly preferably from 1 sec to 10 sec. However, short contact times and, where appropriate, repeated dipping of the specimen 35 has proven successful for avoiding distortion of the external shape of the polymeric molding. An ultrasound bath may be used to deagglomerate the agglomerated particles, and the particles can be kept suspended by continuous stirring.
_ 7 _ The process of the invention can produce a self-cleaning polymer surface which has an artificial, at least to some extent hydrophobic, surface structure made from elevations and depressions, where the elevations and depressions are formed by particles secured to the polymer surf ace .
The self-cleaning polymer surfaces of the invention have particles of a material selected from silicates, doped silicates, minerals, metal oxides, silicas, 1C fumed silicas, precipitated silicas, metal powders, and polymers. The polymer surfaces also comprise at least one polymer selected from polycarbonates, poly(meth)acrylates, polyamides, PVC, polyethylenes, polypropylenes, polystyrenes, polyesters, and polyether sulfones, and their mixtures and copolymers. The particles secured to the polymer surface preferably have an average particle diameter of from 0.02 to 100 ~,m, preferably from 0.2 to 50 ~cm, and particularly preferably from 0.3 to 30 Vim. The particles may also be present in the form of aggregates or agglomerates, where in accordance with DIN 53 206 aggregates have primary particles in edge- or surface-contact, while agglomerates have primary particles in point-contact. The separations of the individual particles on the self-cleaning surfaces are from 0 to 10 particle diameters, in particular from 2 to 3 particle diameters.
In one very particularly preferred embodiment, the self-cleaning polymer surface of the invention comprises particles which have an irregular fine structure in the nanometer range on the surface. The presence of a fine structure in the nanometer range on the surface of the particles achieves particularly effective self-cleaning action, since the separation of the elevations and - 7a -depressions is not purely a function of the separation of the particles, and therefore of the particle size, but is also a function of the separation between the elevations and depressions on the particles. The average height of the elevations is preferably from 20 to 500 nm, particularly preferably from 50 to 200 nm. The separation of the elevations and, respectively, depressions on the particles is preferably less than 500 nm, very particularly preferably less than 200 nm.
The particles on the polymer surface of the invention preferably have hydrophobic properties. The hydrophobic properties of the polymer surface and of the particles achieves a surface structure which is at least to some extent hydrophobic and by way of which the self-15~ cleaning action of the surfaces can be increased as desired, since contamination on the surface can be removed by using small amounts of water, or automatically by rain (self-cleaning effect).
_ g _ The process of the invention can produce objects with a self-cleaning surface. These objects can be obtained by coating the object with at least one polymer in order to obtain a polymer surface where the object itself is not made of a polymer, and then securing particles to this polymer surface by means of a process of the invention.
Example 1: Self-cleaning surface based on a polypropylene surface Decalin is heated to a temperature of 80°C. The decalin comprises 3% by weight of fumed silica (Aerosil R 8200, Degussa AG). Aerosil R 8200 is a hydrophobicized fumed silica with a primary particle size distribution of from about 5 to 50 um. An ultrasound bath is used to deagglomerate agglomerated particles. The solution is kept continuously-stirred. A polypropylene sheet of dimensions 5 x 5 cm is dipped in the suspension for about 3 sec. Once the solvent has been dried off, the sheet is dipped for a second time in the suspension for 3 sec. Fig. 1 shows the resultant self-cleaning lotus surface. The scanning electron micrograph (SEM) clearly shows that the particles have been bonded into the polymer matrix. The resultant surface has the same chemical stability as the polypropylene and exhibits a very 2 o good lotus effect. Water droplets roll off at an angle of as little as 4°, and if the surface is soiled using carbon black, even very small amounts of water are sufficient to render the surface again completely free from carbon black.
Example 2: Self-cleaning surtace based on a polyester surface 3°~ by weight of fumed silica (Aerosil R 8200, Degussa AG) are suspended in hot dimethyl sulfoxide (DMSO). A commercially available polyester sheet of dimensions 5 x 5 cm is dipped in this solution for 5 sec.
3o Fig. 2 shows the primary particles bonded into the polyester. Here again, a very good self-cleaning effect (lotus effect) is observed. Water droplets roll off spontaneously at an angle as small as 14° and if the surface is soiled with carbon black even very small amounts of water are sufficient to render the surface again completely free from carbon black.
Figures 1 and 2 show the surfaces from the examples, produced according to the invention.
- 9 - O.Z. 5751 Fig. 1: SEM of a polypropylene sheet produced as in Example 1 with Aerosil R 8200.
Fig. 2: SEM of a polyester sheet comprising particles of fumed silica and produced by dipping the sheet into a DMSO solution comprising the particles.
Claims (32)
1. A process for producing an object having a self-cleaning surface, in which a surface structure, that is at least to some extent hydrophobic, is created by securing particles on a polymer surface, which process comprises:
(1) applying, to the polymer surface, at least one solvent which comprises the particles and which solvates the polymer surface, and (2) removing the solvent to secure the particles to the polymer surface.
(1) applying, to the polymer surface, at least one solvent which comprises the particles and which solvates the polymer surface, and (2) removing the solvent to secure the particles to the polymer surface.
2. The process as claimed in claim 1, wherein the particles used comprise at least one material selected from silicates, doped silicates, minerals, metal oxides, silicas, and polymers.
3. The process as claimed in claim 1 or 2, wherein the particles are of at least one material selected from fumed silica, aluminum oxide, silicon oxide, fumed silicates and pulverulent polymers.
4. The process as claimed in any one of claims 1 to 3, wherein the particles have an average particle diameter of from 0.02 to 100 µm.
5. The process as claimed in any one of claims 1 to 4, wherein the particles have an average particle diameter of from 0.3 to 30 µm.
6. The process as claimed in any one of claims 1 to 5, wherein the particles have an irregular fine structure in the nanometer range on their surface.
7. The process as claimed in any one of claims 1 to 6, wherein the particles have been suspended in the solvent.
8. The process as claimed in any one of claims 1 to 7, wherein the polymers forming the polymer surface comprise at least one polymer selected from polycarbonates, polyacrylonitriles, poly(meth)acrylates, polyamides, PVC, polyalkylene terephthalates, polyethylenes, polypropylenes, polystyrenes, polyesters, and polyether sulfones, and also their mixtures and copolymers.
9. The process as claimed in any one of claims 1 to 8, wherein the solvent, suitable for the selected polymer used, comprises at least one compound selected from the group consisting of alcohols, glycols, ethers, glycol ethers, ketones, esters, amides, organic nitrogen compounds, organic sulfur compounds, nitro compounds, halogenated hydrocarbons, and hydrocarbons, or a mixture of two or more of these compounds.
10. The process as claimed in any one of claims 1 to 9, wherein the solvent, suitable for the selected polymer used, comprises at least one compound selected from the group consisting of methanol, ethanol, propanol, butanol, octanol, cyclohexanol, phenol, cresol, ethylene glycol, diethylene glycol, diethyl ether, dibutyl ether, anisole, dioxane, dioxolane, tetrahydrofuran, monoethylene glycol ether, diethylene glycol ether, triethylene glycol ether, polyethylene glycol ether, acetone, butanone, cyclohexanone, ethyl acetate, butyl acetate, isoamyl acetate, ethylhexyl acetate, glycol esters, dimethylformamide, pyridine, N-methylpyrrolidone, N-methylcaprolactone, acetonitrile, carbon disulfide, dimethyl sulfoxide, sulfolane, nitrobenzene, dichloromethane, chloroform, tetrachloromethane, trichloroethene, tetrachloroethene, 1,2-dichloroethane, chlorophenol, chlorofluorohydrocarbons, petroleum spirits, petroleum ethers, cyclohexane, methylcyclohexane, decalin, tetralin, terpenes, benzene, toluene, and xylene, or a suitable mixture made from two or more of these compounds.
11. The process as claimed in any one of claims 1 to 10, wherein the solvent which comprises the particles is heated, prior to application to the polymer surface, to a temperature of from -30 to 300°C.
12. The process as claimed in any one of claims 1 to 11, wherein the solvent which comprises the particles is heated, prior to application to the polymer surface, to a temperature of from 25 to 100°C.
13. The process as claimed in any one of claims 1 to 12, wherein the solvent which comprises the particles is heated, prior to application to the polymer surface, to a temperature of from 50 to 85°C.
14. The process as claimed in at least one of claims 1 to 13, wherein the particles are hydrophobic.
15. The process as claimed in at least one of claims 1 to 14, wherein the particles which have been made hydrophobic by virtue of treatment with at least one compound selected from the group consisting of an alkylsilane, a perfluoroalkylsilane, a paraffin, a wax, a fatty ester, a functionalized long-chain alkane derivative and an alkyldisilazane.
16. The process as claimed in at least one of claims 1 to 12, wherein the particles are made hydrophobic after securing to the polymer surface.
17. The process as claimed in claim 16, wherein the particles are made hydrophobic by virtue of treatment with at least one compound selected from the group consisting of an alkylsilane, a perfluoroalkylsilane, a paraffin, a wax, a fatty ester, a functionalized long-chain alkane derivative and an alkyldisilazane.
18. The process as claimed in any one of claims 1 to 17, wherein an ultrasound bath is used to deagglomerate agglomerated particles having a size greater than 100 µm.
19. The process as claimed in any one of claims 1 to 18, wherein the particles are contained in the solvent at a concentration of from 0.1 to 20% by weight.
20. The process as claimed in any one of claims 1 to 19, wherein the solvent is applied to the polymer surface for a contact time between 1 second and 75 minutes and where the contact time is such that there is not a complete destruction of polymer or a dimensional change in the polymer surface.
21. The process as claimed in claim 20, wherein the contact time is the total contact time based on repeated application of the solvent to the polymer surface.
22. The process as claimed in any one of claims 1 to 21, wherein the solvent is removed by evaporation.
23. An object having a self-cleaning polymer surface produced by a process as claimed in claim 1 and having an artificial surface structure which is, at least to some extent hydrophobic, and is made from elevations and depressions, wherein the elevations and depressions are formed by the particles directly secured to the polymer surface.
24. The object having the self-cleaning polymer surface as claimed in claim 23, wherein the particles are of a material selected from silicates, doped silicates, minerals, metal oxides, silicas, and polymers.
25. The object having the self-cleaning polymer surface as claimed in claim 23 or 24, wherein the polymer surface is made of at least one polymer selected from the group consisting of polycarbonate, poly(meth)acrylate, polyamide, PVC, polyethylene, polyalkylene terephthalate, polypropylene, polystyrene, polyester, and polyether sulfone, and their mixtures and copolymers.
26. The object having the self-cleaning polymer surface as claimed in any one of claims 23 to 25, wherein the particles have an average particle diameter of from 0.02 to 100 µm.
27. The object having the self-cleaning polymer surface as claimed in any one of claims 23 to 26, wherein the particles have an average particle diameter of from 0.1 to 30 µm.
28. The object having the self-cleaning polymer surface as claimed in any one of claims 23 to 27, wherein the particles have an irregular fine structure in the nanometer range on their surface.
29. The object having the self-cleaning polymer surface as claimed in any one of claims 23 to 28, wherein the particles are hydrophobic.
30. The object having the self-cleaning polymer surface as claimed in any one of claims 23 to 29, wherein the individual particles on the surface are separated from each other by from 0 to 10 particle diameters.
31. The object having polymer surface as claimed in any one of claims 23 to 30, wherein the elevations have an average height of from 20 to 500 nm.
32. A process for producing an object having a self-cleaning structured surface, which process comprises:
providing an object having a surface, at least an outermost layer of which is made of a polymer;
applying, to the surface of the object, a dispersion of particles in a solvent, wherein the particles are inherently hydrophobic or have been hydrophobicized and have a particle diameter of from 0.2 to 100 µm and the solvent solvates the surface made of the polymer but does not attack the particles, whereby at least a part of the particles sink into the solvated surface of the object; and removing the solvent from the object, whereby the solvated surface of the object hardens again and the particles sunk into the surface of the object become secured to the surface, wherein the individual particles so secured to the surface are separated from each other at a distance of 0 to times the particle diameter of the particles.
providing an object having a surface, at least an outermost layer of which is made of a polymer;
applying, to the surface of the object, a dispersion of particles in a solvent, wherein the particles are inherently hydrophobic or have been hydrophobicized and have a particle diameter of from 0.2 to 100 µm and the solvent solvates the surface made of the polymer but does not attack the particles, whereby at least a part of the particles sink into the solvated surface of the object; and removing the solvent from the object, whereby the solvated surface of the object hardens again and the particles sunk into the surface of the object become secured to the surface, wherein the individual particles so secured to the surface are separated from each other at a distance of 0 to times the particle diameter of the particles.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE10118349A DE10118349A1 (en) | 2001-04-12 | 2001-04-12 | Self-cleaning surfaces through hydrophobic structures and processes for their production |
| DE10118349.6 | 2001-04-12 |
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| CA2381743A1 true CA2381743A1 (en) | 2002-10-12 |
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| CA002381743A Abandoned CA2381743A1 (en) | 2001-04-12 | 2002-04-10 | Surfaces which are self-cleaning by hydrophobic structures, and a process for their production |
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| EP (1) | EP1249468A3 (en) |
| JP (1) | JP2002322299A (en) |
| CA (1) | CA2381743A1 (en) |
| DE (1) | DE10118349A1 (en) |
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| DE102016012001A1 (en) | 2016-10-06 | 2018-04-12 | Karlsruher Institut für Technologie | Highly fluorinated nanostructured polymer foams for the production of super-repellent surfaces |
| JP6885863B2 (en) * | 2017-12-28 | 2021-06-16 | 富士フイルム株式会社 | Pattern formation method, film formation method and sheet-like material |
| FR3078540B1 (en) * | 2018-03-02 | 2020-12-25 | Centre Nat Rech Scient | PROCESS FOR DEPOSITING NANOOBJETS ON THE SURFACE OF A POLYMERIC GEL INCLUDING ZONES OF DISTINCT RIGIDITIES |
| EP3794080B1 (en) | 2018-05-18 | 2024-04-10 | The University of North Carolina at Chapel Hill | Compositions, devices, and methods for improving a surface property of a substrate |
| CN111234287A (en) * | 2018-11-29 | 2020-06-05 | 无锡小天鹅电器有限公司 | Method for treating the surface of a polymer article, hydrophobic polymer article and use thereof |
| CN109468648A (en) * | 2018-12-29 | 2019-03-15 | 哈尔滨工业大学 | The large-scale producing method on aluminum or aluminum alloy antifrost surface |
| CN110240855B (en) * | 2019-05-30 | 2021-08-03 | 江苏大学 | Porous super-slip anti-icing coating and preparation method thereof |
| CN111468372A (en) * | 2020-03-11 | 2020-07-31 | 西北师范大学 | Preparation method of super-wetting silicone oil type liquid perfusion surface |
| CN111777782B (en) * | 2020-07-09 | 2023-05-12 | 台州蓝天企业服务有限公司 | Hydrophobic self-cleaning polyvinyl chloride film and preparation method thereof |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3354022A (en) * | 1964-03-31 | 1967-11-21 | Du Pont | Water-repellant surface |
| US4264140A (en) * | 1977-02-14 | 1981-04-28 | Halm Instrument Co., Inc. | Low reflection coatings for windows |
| US5432000A (en) * | 1989-03-20 | 1995-07-11 | Weyerhaeuser Company | Binder coated discontinuous fibers with adhered particulate materials |
| US5607768A (en) * | 1995-05-15 | 1997-03-04 | General Motors Corporation | Lubricous polymer-encapsulated ferromagnetic particles and method of making |
| PL191143B1 (en) * | 1999-03-25 | 2006-03-31 | Wilhelm Barthlott | Method of producing self-cleaning removable surface finish |
| DE19952383A1 (en) * | 1999-10-30 | 2001-05-17 | Henkel Kgaa | Detergents and cleaning agents |
| JP2001191025A (en) * | 1999-11-04 | 2001-07-17 | Dainippon Printing Co Ltd | Method for manufacturing high molecular fine particle composite body |
| US6569494B1 (en) * | 2000-05-09 | 2003-05-27 | 3M Innovative Properties Company | Method and apparatus for making particle-embedded webs |
-
2001
- 2001-04-12 DE DE10118349A patent/DE10118349A1/en not_active Withdrawn
-
2002
- 2002-03-01 EP EP02004729A patent/EP1249468A3/en not_active Withdrawn
- 2002-04-09 US US10/118,257 patent/US20020150723A1/en not_active Abandoned
- 2002-04-09 JP JP2002106523A patent/JP2002322299A/en active Pending
- 2002-04-10 CA CA002381743A patent/CA2381743A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| DE10118349A1 (en) | 2002-10-17 |
| EP1249468A2 (en) | 2002-10-16 |
| US20020150723A1 (en) | 2002-10-17 |
| EP1249468A3 (en) | 2003-11-26 |
| JP2002322299A (en) | 2002-11-08 |
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