Method for recovering painted plastics

Abstract

The present disclosure relates to a method for recovering painted plastic parts. In order to provide a method for recovering painted plastic materials, which enables the achievement of particles, the physical properties of which almost correspond to the physical properties of new materials, without the addition of chemicals, a method is proposed in the scope of the disclosure, the plastic part is comminuted in one or more steps to a particle size in the range of about 50 to 500 [mu] m, the plastic particles are then fed to an extruder, by means of which a plastic strand is extruded in a melting and kneading phase and after filtration, and the plastic strand is then granulated. In the scope of the present disclosure, it is surprisingly shown that, in this way, plastic pellets are obtained, preferably without the addition of chemicals, with which painted plastic parts can also be produced, the physical properties of which correspond almost to the physical properties of new materials.

Description

Technical Field

[0001] The present invention relates to a method for recycling painted plastic parts. Background Art

[0002] Plastic products are often used for automotive parts. When recycling unpainted plastic bumpers, for example, defectively molded bumpers and bumpers removed from scrapped vehicles are coarsely shredded into cubes approximately 3 mm in size, mixed with pure or new material, and reused for bumper molding. This is possible because the physical properties of recycled plastic material are not significantly inferior to those of new material.

[0003] However, in the case of plastic parts with painted surfaces, the plastic material recovered in this way cannot be reused for identical new parts. In other words, if painted plastic parts are shredded, the paint significantly deteriorates the physical properties of the plastic material, such as impact resistance, ductility, and surface quality, to the point where satisfactory quality can no longer be achieved for new parts.

[0004] Therefore, defectively molded or painted plastic parts taken from scrapped vehicles are disposed of in landfills or incinerated, which is harmful to the environment.

[0005] Methods for removing paint by sandblasting are known from the prior art. Sandblasting material is blown onto the paint of the painted plastic part by compressed air in order to mechanically remove the paint.

[0006] Methods for separating resin melts and varnishes using screening devices are also known. The varnished plastic parts are coarsely comminuted and fed into an extruder, where they are melted. Since the varnish does not melt in the extruder due to its thermal curing, it can be separated using a screening device installed at the outlet of the extruder.

[0007] Furthermore, methods are known for removing coatings from plastics using chemicals.

[0008] EP 1 205 513 A2 describes a method for stripping paint from plastic parts coated with a paint layer. The paint layer is first comminuted into disintegrable portions. A paint stripper is then added to the plastic parts to reduce the adhesion of the paint layer thereon and stirred with the aid of a conveying screw. The paint stripper comprises an emulsion of at least one benzyl-substituted alkanol, alkyl glycol acetate, or N-alkyl pyrrolidone, along with an alkali solution (which are not completely miscible). The mixing ratio of the individual components of the paint stripper is selected so that it falls within the mixing gap. After the paint stripper has acted on the painted plastic parts, a liquid-absorbing solid material is added to the plastic parts to enable further process control to be carried out dry. The plastic parts are then fed to a hammer mill, where the paint layer swollen by the paint stripper is scraped off. Due to the chemicals used, this method is complex, expensive, and environmentally harmful.

[0009] Furthermore, there are methods in which plastic components are comminuted and mixed with new plastic.

[0010] According to DE 197 15 945 A1, comminuted plastic parts are fed into a hammer mill and set in motion there together with plastic granules made of PA66 GF 30. The heating and impacting loosen the paint particles and produce largely de-painted plastic granules.

[0011] Finally, there are purely mechanical methods for recycling painted plastic parts.

[0012] EP 0 575 751 A1 and DE 42 17 005 A1 describe a method in which painted plastic parts are finely comminuted into fragments in multiple stages, but not pulverized. Due to the density difference, the fragments are separated into a sinking part and a floating part in a float-sink device. The floating part, which mainly consists of plastic, is then ground, wherein the material fragments have an average fiber length of 1 to 3 mm. Here, the material fragments are subjected to shearing, wherein the paint particles adhering to the material fragments are removed. In a vibrating screen, the separated paint is screened out and removed. The material fragments from which the paint has been removed are fed into a vacuum granulation extruder for further processing, since recycled material is obtained in the form of granules. Due to the significantly higher proportion of fillers and the better adhesion of the paint of the paint systems developed in the course of the 1990s and the higher filler content of the plastic, this approach is no longer possible in the case of newer painted plastic products. Summary of the Invention

[0013] The object of the present invention is therefore to provide a method for recycling painted plastic materials which makes it possible (preferably without adding chemicals) to obtain particles whose physical properties correspond almost to those of the new material.

[0014] According to the invention, this object is achieved by a method in which

[0015] comminuting the plastic parts in one or more steps to a particle size in the range of approximately 50 to 500 μm,

[0016] wherein the plastic granules are subsequently fed to an extruder, with which plastic strands are extruded after a melting and kneading phase and filtration, and

[0017] • The plastic strands are subsequently pelletized.

[0018] The stated particle sizes are respectively average particle sizes.

[0019] The present invention surprisingly demonstrated that, in this way, plastic granules can be obtained from pure plastic parts, which can also be used to produce painted plastic parts with physical properties that almost correspond to those of new materials. The method according to the invention can be carried out without the addition of chemicals. In contrast to the methods of EP 0 575 751 A1 or DE 42 17 005 A1, the plastic is not de-lacquered before extrusion (which is no longer possible with current painted plastics using the methods described there). Instead, the plastic is extruded with the paint still attached.

[0020] In a preferred embodiment of the invention, it is provided that the plastic component is comminuted in one or more steps to a particle size of approximately 100 to 400 μm and particularly preferably approximately 200 to 300 μm.

[0021] It is possible to reuse only the recycled plastic granules as raw material for producing new plastic components for the original or new application.

[0022] However, it is preferred to mix the obtained recycled plastic granules and / or recycled plastic granules consisting of unpainted raw materials with new plastic in order to produce new plastic components for the original or new application.

[0023] Pure plastic granules made of coated raw materials, recycled according to the invention, can be mixed with virgin plastic. Furthermore, recycled plastic granules made of coated raw materials can be mixed with recycled plastic granules made of uncoated raw materials, and this mixture can be mixed with virgin plastic. The type and composition of the mixture depends on the specific product requirements.

[0024] In this case, the mixture contains, for example, between 10% and 90% by weight, preferably between 20% and 80% by weight, and particularly preferably between 30% and 50% by weight of recycled plastic particles and / or recycled plastic particles consisting of unpainted plastic parts.

[0025] An advantageous embodiment of the invention provides that the plastic components are comminuted in several steps, wherein first a pre-comminution takes place, for example by means of a comminuting machine, then optionally an intermediate comminution takes place, for example in a cutting mill, and finally the plastic components are ground, for example in a disc mill or a vibration mill.

[0026] It is preferred within the scope of the invention that after the comminution of the plastic parts an electrostatic separation is carried out, wherein paint portions detached from the plastic parts during the comminution are removed.

[0027] This electrostatic separation is preferably carried out after the comminution of the plastic parts and before the grinding.

[0028] After the pre-comminution, plastic parts with a size of approximately 20 to 80 mm are preferably present, and after the intermediate comminution, plastic parts with a size of approximately 4 to 20 mm are present. Depending on the starting product and the selected comminution method, other plastic part sizes may also be present after the individual method steps, and it is also possible to omit the intermediate comminution step and pass directly from the pre-comminution to the grinding.

[0029] Furthermore, it is preferred that the grinding material is cooled during the grinding of the plastic component. By cooling the grinding material, better grinding results are achieved.

[0030] Plastic particles with a particle size of approximately 50 to 500 μm (hereinafter referred to as “grind material”) are now present, which are subsequently subjected to extrusion.

[0031] According to the invention, the extruder is a single-screw extruder or a twin-screw extruder, the latter being preferred. In a twin-screw extruder, the plastic is subjected to higher shear forces, which is advantageous for the present application. Filtration is preferably carried out using a melt filter.

[0032] Preferably, additives containing stabilizers and impact modifiers are added to the ground stock before or during extrusion. Here, between 0.5% and 3% by weight of additives are added, based on the amount of ground stock. This further improves the quality of the final product.

[0033] If necessary, the additives may also contain odor absorbers. This is particularly relevant when the end product is used in indoor spaces.

[0034] A preferred embodiment of the invention is that the plastic strands are pelletized by means of strand pelletizing or underwater pelletizing, the former being preferred.

[0035] Of course, other granulation methods can also be used.

[0036] Within the scope of the present invention, the plastic component is a painted plastic component of a motor vehicle.

[0037] This can be, for example, a painted bumper. Of course, the method according to the invention can also be used to recycle other painted plastic parts from motor vehicles and from other areas.

[0038] The method according to the invention is suitable in principle for all painted plastics, in particular PA, PE, PP, PC, PET, wherein preference is given to using non-fiber-reinforced plastics. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0040] in:

[0041] Figure 1 A schematic flow chart of the method according to the invention for recycling painted plastic parts is shown. DETAILED DESCRIPTION

[0042] First, if necessary, the plastic component is pre-processed manually or mechanically, so that a plastic component of pure quality is present.

[0043] In a first step, the plastic parts are pre-shredded in a shredder to a size of approximately 20 to 80 mm. Before or after this step, the metal parts are sorted and / or removed.

[0044] The pre-shredded plastic parts are conveyed by means of a conveyor belt to a cutting mill (1), where they are shredded to a size of approximately 4 to 20 mm.

[0045] The lacquer parts that have been detached are subsequently removed by means of an electrostatic separation system (not shown).

[0046] The plastic parts are then conveyed via a conveyor belt or screw conveyor system to a disc mill (2). In the disc mill (2), the plastic parts are then comminuted to a particle size of approximately 300 μm and subsequently fed to a screening device (3), which ensures the desired particle size.

[0047] Plastic particles with a particle size of approximately 50 to 500 μm (hereinafter referred to as “grind material”) are now present, which are subsequently subjected to extrusion.

[0048] Before or during extrusion, 1% by weight, based on the amount of plastic granules, of additives are added, which comprise stabilizers and impact modifiers and, if appropriate, also odor absorbers.

[0049] The sieved plastic granules are fed via a metering unit to an extruder (4), which, depending on the material, is a single-screw extruder or a twin-screw extruder, the latter being preferred. Extrusion comprises a melting and kneading phase.

[0050] After extrusion, the plastic is pelletized, preferably in a water bath (5) by means of strand pelletization (6), although alternative pelletization methods can also be used.

[0051] Granules having a size of approximately 3 to 8 mm, for example, are sieved by means of a glass sieve and fed to a packaging unit (7).

[0052] If necessary, the intermediate products of the process and the particles can also be homogenized.

Claims

1. A method for recycling painted plastic parts, characterized in that The following steps: comminuting the plastic component in one or more steps into plastic particles having a particle size in the range of 50 to 500 μm, conveying the plastic granules to an extruder, with which plastic strands are extruded after a melting and kneading phase and filtering, and The plastic strands are then pelletized.

2. The method according to claim 1, characterized in that The plastic parts are comminuted to a particle size of approximately 100 to 400 μm and particularly preferably approximately 200 to 300 μm.

3. The method according to claim 1 or 2, characterized in that Only recycled plastic granules are reused as raw material for the manufacture of new plastic components for original or new applications.

4. The method according to claim 1 or 2, characterized in that Recycled plastic granules obtained from painted raw materials and / or recycled plastic granules obtained from unpainted raw materials are mixed with new plastic to produce new plastic parts for original or new applications, wherein the mixture contains between 10% and 90% by weight, preferably between 20% and 80% by weight and particularly preferably between 30% and 50% by weight of recycled plastic granules and / or recycled plastic granules consisting of unpainted plastic parts.

5. The method according to any one of claims 1 to 4, characterized in that The plastic components are comminuted in several steps, wherein first a pre-comminution takes place, then optionally an intermediate comminution takes place, and finally the plastic components are ground, for example in a disc mill or a vibration mill.

6. The method according to claim 5, characterized in that After the pre-comminution, plastic parts with a size of approximately 20 to 80 mm are present, and after the intermediate comminution, plastic parts with a size of approximately 4 to 20 mm are present.

7. The method according to any one of claims 1 to 6, characterized in that After the comminution of the plastic components, an electrostatic separation is carried out, in which the paint fractions that were detached from the plastic particles during the grinding process are removed.

8. The method according to any one of claims 1 to 7, characterized in that The ground material is cooled during the grinding of the plastic parts.

9. The method according to any one of claims 1 to 8, characterized in that As the extruder, a single-screw extruder or a twin-screw extruder is used, and among them, a twin-screw extruder is preferred.

10. The method according to claim 1, wherein: Prior to the extrusion, additives are added to the plastic granules in an amount of between 0.5% by weight and 3% by weight, relative to the plastic granules, the additives comprising a stabilizer and an impact modifier.

11. The method according to claim 10, characterized in that The additive comprises an odor absorber.

12. The method according to any one of claims 1 to 11, characterized in that The plastic strands are pelletized by means of strand pelletizing or underwater pelletizing.

13. The method according to any one of claims 1 to 12, characterized in that The plastic component is a painted component of a motor vehicle.

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