REACTIVE PLASTIC POWDER, METHOD FOR ITS PREPARATION AND USE OF THE SAME

Description

[0001] The present invention relates to a reactive plastic powder, a method for its production, and the use of the reactive plastic powder.

[0002] On snowboards and other snow sports equipment, accidental contact with stones or other hard objects in the snow can cause scratches or gouges in the base. The base is a plastic coating on the running surface of the snowboard or snow sports equipment. The plastic used for the base is usually polyolefin, particularly extruded or sintered polyethylene, most often HDPE (high-density polyethylene). A damaged base can negatively affect the performance of such equipment and also creates a point of entry for further potential damage to the underside of the snowboard or snow sports equipment. Therefore, repair is always necessary when the plastic base is damaged in this way.

[0003] In a common repair method, after cleaning the damaged area, a so-called "repair candle" (a thin polyethylene rod) is lit at the tip. The lit candle is then held over the area to be repaired, and the damaged area in the pavement is filled with dripping liquid polyethylene. After it cools, excess material is removed with a metal scraper. However, areas repaired with the "repair candle" tend to become brittle and sometimes crumble out again. Furthermore, deeper damage often results in depressions, partly due to shrinkage and partly because it is difficult to completely fill a damaged area by dripping the material.

[0004] Patent US 3,457,129 describes a method for repairing ski bases. First, a powder of high-density polyethylene (HDPE) is poured into the damaged area of ​​the base, extending slightly above the edge of the damaged area, and pressed down. Then, a heat-resistant, non-adherent polytetrafluoroethylene (PTFE, known as Teflon®) film is placed over the repair. A hot iron is then pressed down on top, causing the HDPE powder to melt beneath the PTFE film and bond with the molten polyethylene material of the base surrounding the damaged area. After removing the iron and allowing the repair to cool, the PTFE film is peeled off.

[0005] In addition to the methods described, which require fire or external heat to melt polyethylene, fillers have also been used in conjunction with adhesives, such as cyanoacrylate adhesives, to repair damaged plastic coatings. However, cyanoacrylate adhesives (also called cyanoacrylate and known as "superglue") only work with mineral filler powders because the latter, with their polar and moisture-attracting surface, can trigger the anionic polymerization of the cyanoacrylate monomers to cure the adhesive. The disadvantage of such repairs is that, due to the mineral filler, their properties differ from those of the original plastic coating material, and the lack of homogeneity is disruptive. Furthermore, if the plastic coating is a sliding coating, its sliding properties are impaired.

[0006] Since nonpolar polyolefins such as polyethylene (PE) and polypropylene (PP) are difficult to bond with cyanoacrylate, attempts have been made to overcome this deficiency through modifications. Patent EP 0 900 252 B1 describes polyolefin compounds with improved bondability, particularly with cyanoacrylate adhesives. EP 0 900 252 B1 proposes a solution by adding certain additives to the polyolefin during processing in the melt, for example, during extrusion before final shaping. These additives are capable of initiating the polymerization and curing of cyanoacrylate adhesives. These polymerization initiators should be readily miscible with the polyolefin while also possessing polar groups that, when a molded part made from this modified polyolefin is bonded, initiate the polymerization of the cyanoacrylate monomers.Suitable polymerization initiators include 2-phenylimidazoline, 1,8-diazabicyclo(5,4,0)undec-7-ene (DBU), and 1,5-diazabicyclo(4,3,0)non-5-ene (DBN). However, the production of such modified polyolefin masses in melt extruders is technically complex, and the required chemical additives are relatively intricate.

[0007] The object of the present invention is to avoid the disadvantages known from the prior art and to provide a reactive plastic powder that can be produced without melting and that is suitable for repairing plastic parts without the use of fire, external heat, or electricity. Plastic parts are understood to mean any parts made of plastic, in particular plastic coatings and plastic coverings.

[0008] This problem is solved by a reactive plastic powder having the features of claim 1.

[0009] The present invention also relates to a method according to claim 6 for producing a reactive plastic powder according to the invention.

[0010] The invention also includes the use of a reactive plastic powder according to the invention for repairs of plastic parts, in particular plastic coatings.

[0011] The scope of protection of the present invention also includes plastic parts and objects repaired according to the invention, with correspondingly repaired plastic coverings or coatings. The terms "plastic covering" and "plastic coating" can be understood synonymously.

[0012] Preferred embodiments and variants according to the invention are set out in the respective dependent claims.

[0013] A reactive plastic powder according to the present invention is surface-treated and thereby has at least one alkaline substance on its surface. Surface-treated means that the surface properties have been altered by a treatment acting externally on the surface of the plastic powder particles.

[0014] The at least one alkaline substance on the surface of the reactive plastic powder is selected from the group comprising sodium hydroxide and potassium hydroxide, with sodium hydroxide being particularly preferred.

[0015] The reactive plastic powder according to the invention is based on a polymer, which is preferably a polyolefin. The polyolefin is preferably selected from the group comprising polyethylene and polypropylene, with polyethylene being particularly preferred. Most preferably, the polyethylene is HDPE, i.e., high-density polyethylene.

[0016] The reactive plastic powder according to the invention preferably has a particle size between 0 µm and 400 µm, particularly preferably between 0 µm and 300 µm, and most preferably between 0 µm and 200 µm.

[0017] In the process according to the present invention for producing a reactive plastic powder according to the invention, an untreated plastic powder of a certain particle size is mixed with a compatible liquid to form a suspension. An alkaline solution containing at least one alkaline substance is added to this liquid before or after mixing with the untreated plastic powder. After mixing the components, the suspension is evaporated and the evaporation residue is dried, thus yielding a surface-treated, free-flowing, and reactive plastic powder with substantially the original particle size, which has the at least one alkaline substance on its surface. The deposition of the alkaline substance on the surface of the plastic powder during evaporation and drying corresponds to the surface treatment.

[0018] The polymer of the untreated plastic powder is preferably a polyolefin, particularly preferably HDPE, and the compatible liquid is preferably ethanol with a purity of at least 95 vol.% or petroleum.

[0019] In this context, "compatible" means that the plastic powder can be dispersed and mixed into a suspension in such a liquid. Conversely, water would be incompatible with PE powder because PE powder would clump together in water and could not be dispersed as individual particles.

[0020] The ethanol, with a purity of at least 95% by volume, is preferably 96% ethanol or bioethanol with a purity of at least 99% by volume. Denatured alcohol, i.e., ethanol denatured for technical purposes, can also be used as ethanol.

[0021] In the process according to the invention, the untreated plastic powder is preferably stirred into the compatible liquid to form the suspension, and the mixing of the components, including the added alkaline solution, preferably takes place in a stirring vessel at room temperature. The alkaline solution is sodium hydroxide or potassium hydroxide, with sodium hydroxide being particularly preferred.

[0022] In the process according to the invention, the evaporation of the suspension and the drying of the evaporation residue are preferably carried out in a vessel equipped with an agitator at a preferred temperature in the range of 70 °C to 85 °C, wherein the agitator preferably provides continuous circulation until a dry, free-flowing plastic powder is obtained. The vessel can be a metal vessel into which the suspension is poured. The vessel can be heated by various heating sources known to those skilled in the art. This process step typically takes a few hours.

[0023] However, evaporation and drying can also be carried out in a different temperature range and / or with other equipment, e.g. on a tray in an oven or in a drying cabinet, which would also be within the scope of the manufacturing process according to the invention.

[0024] When using a reactive plastic powder according to the invention, preferably produced according to the inventive method, for repairing plastic parts, in particular damaged areas in plastic coatings, according to the present invention, a damaged, cleaned area in a plastic part is filled tightly with the reactive plastic powder and pressed flat, and then a cyanoacrylate is dripped onto it until the reactive plastic powder is saturated, wherein the alkaline substance present on the surface of the reactive plastic powder initiates the anionic polymerization of the cyanoacrylate and this exothermic chemical reaction leads to a rapid and permanent bond and hardening of the repaired area in the plastic part.

[0025] In the repair of plastic coatings, the repair of damaged areas in the sliding surfaces of snowboards using the reactive plastic powder according to the invention together with cyanoacrylate is particularly preferred.

[0026] Cyanoacrylates are polymerizable liquid monomers. The selected cyanoacrylate is preferably an alkyl cyanoacrylate, particularly preferably selected from the group comprising methyl 2-cyanoacrylate, ethyl 2-cyanoacrylate, n-propyl 2-cyanoacrylate, and n-butyl 2-cyanoacrylate, with ethyl 2-cyanoacrylate being especially preferred. The exothermic polymerization heats the repair area. The softening temperature of polyethylene can even be reached briefly, which would further increase the strength of such a repair area through partial melting.

[0027] Depending on the color of the plastic part to be repaired, a color matching the color of the plastic part is preferably chosen for the reactive plastic powder or even for the initially untreated plastic powder. For example, the gliding surface of snowboards or snowboards is often black. Accordingly, to achieve a uniform color result, a black-colored plastic powder would be selected. At the end of the repair process, excess material is preferably removed with a metal scraper.

[0028] It should be emphasized here that the use of the reactive plastic powder according to the invention is by no means limited to the preferred repair of damaged areas in the sliding surfaces of snowboards, but that any plastic parts can be repaired with the powder according to the invention, and it can be used for a wide variety of repairs of plastic parts. The repairs primarily involve fixing nicks, scratches, dents, indentations, or, more generally, depressions caused by mechanical impact. The material of the plastic part to be repaired can be based on polymers such as polyolefins, PVC, polyurethane, polyesters, polycarbonate, polystyrene, ABS, or polyamides.The plastic parts can be any items from the following areas: sports and leisure, household, electrical and electronics, construction and industry, vehicle manufacturing (for land, water, and air vehicles), medical technology, toys, packaging, etc. Specific examples include: computer and mobile phone casings, automotive components (e.g., a plastic bumper or rearview mirror housing), safety helmets, sprinkler heads for watering cans, garden hoses, or showers, children's toys, plastic clothes hangers, and other plastic household items. The plastic parts can also include plastic floor coverings or coatings for wood (e.g., furniture) or metal.

[0029] The present invention also claims a repaired plastic part or an object with a repaired plastic coating, wherein the plastic part or the plastic coating was repaired using a reactive plastic powder according to the invention, preferably produced according to the inventive method, together with cyanoacrylate, wherein the object with the plastic coating is in particular a snowboard with a sliding surface.

[0030] The following example of the production of a reactive plastic powder serves to illustrate the present invention without limiting its scope: 100 g of HDPE Black polyethylene plastic powder with a particle size between 0 µm and 180 µm were stirred into approximately 100 ml of ethanol, and 2.5 ml of 1 M sodium hydroxide solution (NaOH content approximately 4 wt%) were added. This suspension was stirred for 5 minutes, then evaporated and dried. A reactive polyethylene plastic powder according to the invention was thus obtained.

[0031] It should be noted that any combination of the described features falls within the scope of the present invention, as long as the combinations are not inconsistent.

[0032] As can be seen from the description, the present invention provides an advantageous alternative solution for a reactive plastic powder. This reactive plastic powder can be produced without expensive melt processing machines and can be easily used without an external energy supply to repair any plastic parts, e.g., plastic coatings, especially the sliding surfaces of snowboards, together with cyanoacrylate as an adhesive. Compared to prior art methods, a repair according to the invention can be carried out significantly faster thanks to the rapid chemical reaction. There is no shrinkage, no sagging, and no material crumbling. In addition, unlike prior art, a repair according to the invention also adheres very well to the metal edges (where most deep scratches occur) and to the core material not belonging to the coating, e.g.,on the wood, carbon fiber reinforced plastic, or metal of a ski, and creates a perfect bond to all these materials. The invention results in high-quality, durable, highly adhesive, and permanently resistant plastic repairs with material properties homogeneous to the original plastic material and very high durability. This applies to plastic bases and coatings as well as plastic parts of any shape and type.

Claims

1. Reactive plastic powder for repairing plastic parts, characterized in that it is surface-treated and thereby has on its surface at least one alkaline substance selected from the group consisting of sodium hydroxide and potassium hydroxide.

2. Reactive plastic powder according to claim 1, characterized in that the at least one alkaline substance is sodium hydroxide.

3. Reactive plastic powder according to claim 1 or 2, characterized in that it is based on a polymer which is a polyolefin.

4. Reactive plastic powder according to claim 3, characterized in that the polyolefin is selected from the group comprising polyethylene and polypropylene, wherein polyethylene is preferred, and wherein the polyethylene is preferably an HDPE.

5. Reactive plastic powder according to one of the preceding claims, characterized in that the reactive plastic powder has a grain size between 0 µm and 400 µm, preferably between 0 µm and 300 µm, and particularly preferably between 0 µm and 200 µm.

6. Process for producing a reactive plastic powder according to one of claims 1 to 5, characterized in that an untreated plastic powder of a certain grain size is mixed with a liquid compatible therewith to a suspension, in that an alkaline solution containing at least one alkaline substance is added to this liquid before or after mixing with the untreated plastic powder, in that after mixing the said components the suspension is evaporated and the evaporation residue is dried, and in this way a surface-treated, granulated and reactive plastic powder with substantially the original grain size is obtained, which has on its surface the at least one alkaline substance.

7. Process according to claim 6, characterized in that the polymer of the untreated plastic powder is a polyolefin, preferably HDPE, and the liquid compatible therewith is ethanol with a degree of purity of at least 95% by volume or petroleum.

8. Process according to claim 7, characterized in that the ethanol with a degree of purity of at least 95% by volume is ethanol 96% or bioethanol with a degree of purity of at least 99% by volume.

9. Process according to one of claims 6 to 8, characterized in that, to form the suspension, the untreated plastic powder is stirred into the liquid compatible therewith, and in that the mixing of the components including the added alkaline solution takes place in a stirring vessel at room temperature.

10. Process according to one of claims 6 to 9, characterized in that the alkaline solution is a sodium hydroxide solution or potassium hydroxide solution, wherein a sodium hydroxide solution is preferred.

11. Process according to one of claims 6 to 10, characterized in that the evaporation of the suspension and the drying of the evaporation residue is carried out in a vessel with a stirrer at a preferred temperature in the range from 70°C to 85°C, wherein a permanent circulation preferably takes place by means of the stirrer until a dry granulated plastic powder results.

12. Use of a reactive plastic powder according to one of claims 1 to 5, preferably produced according to one of claims 6 to 11, for repairing defective sites in plastic parts, in particular in sliding liners of snow sliding boards, characterized in that a defective, cleaned site in a plastic part is filled up fully with the reactive plastic powder and the latter is pressed flat, and then a cyanoacrylate is dripped on until the reactive plastic powder is soaked, wherein the alkaline substance present on the surface of the reactive plastic powder initiates the anionic polymerization of the cyanoacrylate and this exothermic chemical reaction leads to a rapid and permanent bonding and curing of the repaired site in the plastic part.

13. Use according to claim 12, characterized in that the cyanoacrylate is an alkyl cyanoacrylate, preferably selected from the group comprising methyl 2-cyanoacrylate, ethyl 2-cyanoacrylate, n-propyl 2-cyanoacrylate and n-butyl 2-cyanoacrylate, wherein ethyl 2-cyanoacrylate is particularly preferred.

14. Use according to claim 12 or 13, characterized in that at the end of the repair of a defective site in a plastic part excess material is removed with a metal stripping blade.

15. Plastic part or object with a plastic lining, characterized in that the plastic part or the plastic lining was repaired using a reactive plastic powder according to one of claims 1 to 5, which had preferably been produced according to one of claims 6 to 11, according to one of claims 12 to 14 together with cyanoacrylate, wherein the object with the plastic lining is in particular a snow sliding board with a sliding lining.