WO2014180817A1 - Spray-coating method - Google Patents

Abstract

The invention concerns a method for spray-coating substrate surfaces which enables different thermoplastically processable materials to be applied to very different types of surfaces by means of spray technology.

Description

 Method for spray coating

The invention relates to a method for spray coating of substrate surfaces, which makes it possible to apply different thermoplastically processable materials on a variety of surfaces by means of spray technology.

For the production of thin-walled, sheet-like components or, for example, insulation on textiles, a wide variety of methods are known. Depending on the application, these methods differ in the form quality, the material, a thickness distribution over the substrate (component) and the technology itself.

The methods of thermoforming, vacuum thermoforming and pressing for processing films into molded parts or individual layers are known.

In the production of sheet-like components by means of these methods, a local mass distribution is determined by the deformation of the film and can not be set in a defined manner. For this reason, for example, insulation thus produced is heavier than it is made acoustic, functional view needed. This hinders a targeted lightweight construction, especially in vehicles.

For material sealing films are applied to a variety of substrates by gluing or melting.

For partial sound insulation so-called heavy-layer foils are placed on carpet or end wall areas from the acoustic point of view, where they stick or melt.

Other methods are known for producing thin, flat components for motor vehicles, such as heavy-layer components for acoustic insulation components, including end walls, which are produced by injection molding of thermosetting and thermosetting materials.

Injection molding (thermoplastic injection molding, or reaction injection molding (RIM)) allows the production of components with different, defined basis weights. The high investment of the equipment as well as the tools limits these procedures to high quantities.

For the RIM process, there is the additional problem that the material to be used, for example polyurethane, is expensive and can not be recycled. Specifically for insulation components in vehicles, the tool geometry determines the mass distribution for all abutments. This also prevents the targeted acoustic optimization of individual vehicle types (engine variants) within a series that would be desirable from an acoustic point of view. Also known are methods for producing such flat components by sintering powder. The powder is applied to a warm molding tool, where it forms a plastic layer by sintering, then cooled and the component is removed. This technology is time, tool and energy intensive. Thus, this process remains limited to the production of high-quality components, such as slush skins.

Are known methods for coating as well as the production of planar components by spraying. The spraying of thermoplastics either takes place from the melt by means of one or more nozzles or via "cold" plastic powder by heating via a flame during the flight phase and a carrier gas or directly by a hot environment during the flight phase However, these processes have very low throughputs and are In the case of a coating of textiles, the high temperatures would destroy the textile material before something is applied.

The spray process is also used in powder regeneration. DE 10 2005 050 890 A1 describes a method and apparatus for producing a nanocomposite, in which the separation of extraction and, if appropriate, dispersion medium from a polymer melt takes place by means of the high pressure spray method. This solidify the polymer droplets abruptly due to the taking place during the relaxation of the high pressure level to ambient pressure strong cooling. This produces the nanocomposites. As heavy layer for spraying, PUR-based crosslinking systems are in use. Versions can be found in DE 101 61 600 AI and DE 10 2005 058 292 AI. These materials are very expensive and can not be recycled.

Furthermore, methods and devices are known in which a plastic strand is deposited on a mostly pretreated substrate surface. EP 0 524 092 B2 describes a method and apparatus for producing an article having a molded profile strand. Here, the profile strand is produced and deposited by an extrusion head which is connected to the extruder via a heated flexible pressure hose.

DE 30 47 727 C2 describes a process for the preparation of thin protective films by spraying liquefied thermoplastic material. The method described here is intended to enable the use of conventional hot spraying equipment, in which the spray material is melted and thus liquefied, which can then be applied directly to the protective surface. It is further described that the tendency of these materials to form beads after hitting the surface has not heretofore yielded a sufficiently homogeneous film, but according to this description, it is most convenient to address them by a simultaneous or subsequent sintering operation. For the sintering of the thermoplastic material, it has accordingly been found to be advantageous if the sintering is carried out by heating the sprayed-on thermoplastic material so as to obtain a uniform, smooth and nonporous application. The heat required for the sintering can the thermoplastic material from the outside through Heat radiation, hot air or the like can be supplied. It may be expedient to spray the thermoplastic material on a previously heated surface, so that the sintering process takes place simultaneously with spraying and thus a temporally optimal process sequence is obtained. However, the sintering process carried out after the impact of the material on the surface is very complicated and thermally re-stresses the substrate material.

DT 16 46 051 B2 describes a process for applying polymeric coatings to solid surfaces by spraying a molten thermoplastic polymer. Thereafter, the melting of the polymer and the supply of the melt in a compressed gas stream is carried out by the injection pressure method and subjected to the sprayed gas / polymer beam during its path to the surface to be coated, a heat radiation treatment. It is described to convert the thermoplastic polymer of any particle size in extruders or piston-cylinder devices in the molten state and sprayed by means of compressed air by means of a compressed air injection nozzle in the form of a heated by a heat flow gas / polymer jet on the surface to be coated, which previously heated becomes.

DE 32 25 844 A1 describes a method and a device for applying layers of thermoplastics or hot melt adhesives. A method is described for applying layers of thermoplastic materials or hot-melt adhesives, in which the plastic or hot-melt adhesive used is melted, then atomized and sprayed. Preferably, here the temperature of the molten Plastic or hot melt adhesive held constant until the moment of spraying. The apparatus for carrying out the method comprises a heatable melting device for a plastic or hot-melt adhesive, a nozzle having a heated spray device, a heatable feeder of the molten material in the spray device, a Temperaturmessund temperature control system and control systems for the supply and delivery of a molten material and possibly of the heated spray gas. As a result, two- or three-dimensional objects of any type and shape can be provided with an arbitrarily strong uniform or patterned layer from the outside and / or inside.

DE 42 31 074 AI describes the use of plastic powders as a filler in sprayable and sprayable coating compositions, paints and sealants. Described is the use of powders of the density range 0.1 to 2.0 g / cm ^{3 of} a mean particle size of not more than 0.2 mm, which have been obtained by mechanical comminution of optionally containing mineral fillers, solid plastics, as a filler, optionally in addition other fillers in sprayable and sprayable paints, coating and sealing compounds based on one- or two-component polyurethane binders.

DE 101 61 600 A1 describes a method for spraying plastic layers. Disclosed is a method and apparatus for applying a filler-containing plastic layer to a shaped surface, wherein a mixture containing binder mixture, solids promoter and filler is applied to the molded article Is sprayed surface, in which one first of a mixture containing binder mixture and solids conveyors, a free jet for spray application generated and then added the filler in the free jet of not yet polymerized binder mixture. The method is particularly suitable for the spray application of heavy layers, as sin are used in conventional mass-spring systems.

DE 10 2005 058 292 A1 describes a method and a device for the production of coated molded parts. Here, a method and an apparatus for producing molded parts, comprising a layer of polyurethane in the weft operation, in which the reactive components are mixed with a cylindrical mixing chamber and the reactive mixture produced then flows through a flow channel and is sprayed onto the surfaces of a substrate and cured and then the flow channel is cleaned by a gas stream.

The present invention is therefore based on the object to provide a method by which a variety of thermoplastically processable materials can be applied in a desired, defined manner on various substrate surfaces in the form of a film.

According to the invention, the aforementioned object is achieved by a method for spray-coating substrate surfaces, wherein (a) a thermoplastic processable material is melted in an extruder in a first step and liquefied therewith, (b) pressurizing the molten material with a carrier gas or vapor,

 (c) pressing a mixture of the molten material and the carrier gas or vapor through one or more nozzles, wherein possibly in the region of the outlet opening of the nozzle the spray jet, a spray gas having a temperature which is at least as high as the melt temperature, supplies and

 (D) the resulting spray with the molten material directed to the substrate surface, wherein the material drops droplet-shaped in the flowable state impinges on the substrate surface, forms a continuous coating on the substrate surface and then solidifies.

The essence of the invention consists essentially in that a thermoplastically processable material alone or as a compound in a mixture with other thermoplastically processable materials, with or without fillers is melted in an extruder, with an inorganic carrier gas or vapor under defined pressure set by pressed one or more hole nozzles as a mixture, relaxed to atmospheric pressure and cooled only on the substrate surface.

In a special version, a compound is mixed directly in a twin-screw extruder. In a further embodiment, for example, this single-screw extruder is followed by a single-screw extruder or a melt pump. As materials for spraying virtually all thermoplastically processable materials are used, regardless of whether they are present as a homopolymer or as a compound, unfilled or filled with non-melting substances. Particularly preferred for the purposes of the present invention are thermoplastically processable materials, such as single-component polymers, copolymers and terpolymers, as well as thermoplastically processable elastomers, in particular selected from acrylonitrile-butadiene-styrene (ABS), polyamide (PA), polylactate (PLA), Polymethyl methacrylate (PMMA), polycarbonate (PC),

Polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polystyrene (PS), polyetheretherketone (PEEK) and polyvinyl chloride (PVC), including their copolymers and compounds, which optionally contain further constituents, in particular fillers. In a specific embodiment, high-performance materials such as PEEK can be sprayed with a high proportion of gas and a concomitant reduction in viscosity. The amount of fillers can be varied freely within wide ranges, wherein the amount of fillers should preferably not exceed 80% by weight, based on the material, since the cohesion of the coating can not otherwise be guaranteed.

The fillers may be inorganic in nature or polymers themselves which do not melt at the processing temperature, such as rubber, the fillers having no preferred direction. In addition, fillers may be inorganic short fibers, polymeric fibers having a higher melting temperature than the processing temperature of the material or compound, and natural fibers. By changing the mixture over the spraying process, the thermoplastically processable material and / or the filler itself, as well as the ratio of thermoplastically processable material to filler, a layered different material structure can be produced.

As a carrier gas are inert, in particular inorganic gases or gas mixtures as well as steam. For the purposes of the invention, nitrogen, carbon dioxide, air or water, for example, is used in gaseous form at this temperature.

The carrier gas or vapor is preferably used in a weight ratio of thermoplastically processable material to carrier gas or vapor in the range of 100 to 0.1 parts by weight to 100 to 30 parts by weight, in particular 100 to 0.3 to 100 to 15 parts by weight. Preferably, a spray is sprayed at a pressure of 10 to 500 bar, in particular 20 to 400 bar.

As the pressure increases, the droplet size decreases; The material application is thus more homogeneous. As the pressure increases, however, the material cools down more during expansion and relaxation. Depending on the material, this means that no bond with the substrate surface is achieved any more. In this case, then a pressurized heated gas (spray gas), preferably air must be supplied, which provides in an advantageous case to an additional atomization.

The nozzles are located, for example, on a flexible pressure tube and can be moved over the substrate surface by means of a robot be that a complete order with material is possible. The nozzle (s) themselves is (are), for example, as a hole nozzle (s) formed with 1 to 50 openings, preferably 5 to 20 openings, with a diameter of 0.1 mm - 10 mm, but preferably 0.5 mm - 2 mm or openings with an equivalent cross-sectional area defined hole geometry of said opening diameter. For additional heating hot air (spray gas) can be introduced.

Slot nozzles can also be used, with the dimensions 0.1 - 3.0 x 3 - 30 mm, preferably 0.5 - 2.0 x 5 - 10 mm; In this case too, several slot nozzles can be arranged in the spray head.

The term carrier gas in the sense of the present invention comprises, in addition to the abovementioned substances and elements which are gaseous at room temperature (normal pressure) or the processing temperature, substances which form gaseous substances by a chemical or thermal reaction or are converted into the gaseous state , Particularly preferred in this sense is hot air.

The chemical composition of the spray gas, which is preferably guided in the form of an annular nozzle around the outlet opening of the thermoplastic, may be the same or different from the carrier gas. Hot air is particularly preferred as the spray gas, which causes a further expansion of the carrier gas in the thermoplastic and a surface heating of the particles.

The invention will be explained below with reference to two examples. EXEMPLARY EMBODIMENTS:

Example 1 :

Commercial extruders KraussMaffei Bernstorff ZE40 Ax29D and KE90x30D were used in series; each equipped with specially designed screws. The tool was a single tube head with 24 hole nozzles, each with a 1.1 mm hole diameter, arranged in two rows.

The thermoplastically processable material used was a compound of 75% by weight of inorganic filler (barite) and 25% by weight of a commercially available plastic mixture of PE / EVA, white oil, flow additive and temperature stabilizer in granular form.

The output was 90 kg / h and the amount of gas (carrier gas) was 1.1 kg / h CO ₂ . The substrate surface used was a commercial compressed mixed fiber fleece.

With these settings, a good spraying behavior was achieved and a flexible plastic layer was produced on the textile surface.

Example 2:

In principle, in this example in a second application substantially the same structure as in Example 1 was used. The nozzle was changed. Here was a round jet nozzle Fa. BETE used in the heated air as a spray gas in an outer ring around the outlet nozzle around the mixture of carrier gas and compound heated. The amount of carrier gas was reduced to 400 g / h. In the material used, the filler was reduced to 25 wt .-% and the amount of compound increased accordingly.

The output was 60 kg / h. The amount of air used (spray gas) was 30 Nm ³ / h and was heated to 300 ⁰ C. The spray result was improved over Example 1.

Claims

claims: 1. A method for spray coating substrate surfaces, wherein  (a) melts a thermoplastic processable material in an extruder in a first step and liquefies it,  (b) pressurizing the molten material with a carrier gas or vapor,  (c) pressing a mixture of the molten material and the carrier gas or vapor through one or more nozzles, wherein possibly in the region of the outlet opening of the nozzle the spray jet, a spray gas having a temperature which is at least as high as the melt temperature, supplies and  (D) the resulting spray with the molten thermoplastically processable material directed to the substrate surface, wherein the material drops droplet-shaped in the flowable state impinges on the substrate surface, forms a continuous coating on the substrate surface and then solidifies. 2. The method according to claim 1, characterized in that the thermoplastically processable material is selected from single-material polymers, copolymers and terpolymers or thermoplastically processable elastomers in particular acrylonitrile-butadiene-styrene (ABS), polyamide (PA), polylactate (PLA) , Polymethyl methacrylate (PMMA), polycarbonate (PC), polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polystyrene (PS), polyetheretherketone (PEEK) and polyvinylchloride (PVC) including their copolymers and compounds, which optionally contains further constituents, in particular fillers. 3. The method according to claim 1 or 2, characterized in that one uses a quantity of fillers of 0 to 80 wt.%, Based on the thermoplastically processable material. 4. The method according to claim 3, characterized in that the filler is inorganic in nature. 5. The method according to claim 3 or 4, characterized in that the filler is present as inorganic short fiber. 6. The method according to any one of claims 3 to 5, characterized in that the filler comprises polymeric fibers having a higher melting temperature than the processing temperature of the compound. 7. The method according to any one of claims 3 to 6, characterized in that the filler comprises natural fibers. 8. The method according to any one of claims 1 to 7, characterized in that in the course of the spraying process, the mixture, the thermoplastically processable material and / or the filler itself, as well as the weight ratio of thermoplastically processable material to filler varies. 9. The method according to any one of claims 1 to 8, characterized in that one uses as the carrier gas and / or spray gas nitrogen, carbon dioxide or air. 10. The method according to any one of claims 1 to 9, characterized in that a spray jet with a weight ratio of thermoplastically processable material to carrier gas in the range of 100 to 0.1 parts by weight to 100 to 30 parts by weight, in particular 100 to 0.3 to 100 to 15 parts by weight. 11. The method according to any one of claims 1 to 10, characterized in that one uses a spray with a pressure of 10 to 500 bar, in particular 20 to 400 bar. 12. The method according to any one of claims 1 to 11, characterized in that one uses 1 to 50, in particular 5 to 20 nozzles with different outlet cross-sectional areas. 13. The method according to any one of claims 1 to 12, characterized in that the mixture is pressed through perforated and / or slot nozzles. 14. The method according to any one of claims 1 to 13, characterized in that one uses hole nozzles with the same of different diameters in the range of 0.1 to 10 mm, in particular 0.5 to 2 mm or outlet openings with a comparable cross-sectional area. 15. The method according to any one of claims 1 to 14, characterized in that one uses slot nozzles with the same of the different cross sections of 0.1 to 3 mm x 3 to 30 mm, in particular 0.5 to 2 mm x 5 to 10 mm. 16. The method according to any one of claims 1 to 15, characterized in that one produces a continuous coating which is porous or self-contained. 17. The method according to any one of claims 1 to 16, characterized in that one uses a substrate which is selected from textiles or a Werkzeugkavität with or without surface structure.