DE4311138C2 - Recycling of thermoplastics with thin coatings from melt-inert foreign substances - Google Patents

Description

Wastes from the manufacture of vapor-coated or otherwise thinly coated Plastic parts have been obtained almost exclusively through landfill disposed of. It is desirable to reuse the valuable raw material. The The same also applies to used coated plastic parts that were previously deposited were. Recyclates of such coated plastic parts, especially lamp and Headlight reflectors, can instead be used as secondary raw materials for manufacturing of plastic molded parts of any kind can be used.

The object of the invention is therefore a method, thinly coated with foreign matter Polymers to high quality, one without separating the coating to process equivalent recyclate without coating proportion comparable recyclate. Homo- or copolycarbonates are polymers suitable.

Homo- or copolycarbonates with thin functional coatings, such as z. B. in reflectors, housings electronic devices and glazing can be found through Milling and homogenizing over the melt, either in a separate step or during processing to recycle to high quality materials. Surprisingly the surface of the parts is of a quality that is even theirs re-steaming or sputtering allowed. It is also surprising that the  Material properties of the recyclates differ only slightly from those of the material distinguish from which the molded parts were made. The properties lie at the level of an equivalent recyclate, i.e. H. same thermal history, without coating part incorporated in the melt.

Are foreign substance-coated, for. B. thickly painted or galvanized molded plastic parts then processed again without prior separation of the coating the properties of the resulting molded plastic parts are mostly unsatisfactory. This is also the case when the recyclate is mixed with Primaware, because large particles of the coating in the matrix the new molded part with mechanical Let the load fail. Therefore, in the professional reprocessing molded parts coated in such a way the most gentle removal of the Coating is an essential process step.

Patent application P 41 34 019.1 claims for metal-coated plastics a chemical stripping process. The waste or old parts become Crushed fragments of 0.1 to 5 cm in diameter, then with acid or base treated and filtered off after washing and dried.

The US patent 44 06 411 teaches that the metal content from the regrind cold-milled, metal-coated molded plastic parts by conventional separation processes such as sieving, air separation, hover-sink or magnetic separation leaves.

More sophisticated recycling processes of the prior art for coated Plastic moldings have in common that they are before the actual reprocessing of the plastic material must remove the molded part. On the other hand Inferior recyclate qualities are described.

It has now been found that plastic moldings and production committee made of homo- or copolycarbonates functional or decorative coatings made of foreign substances in a layer thickness up to up to 10 µm, preferably up to 5 µm, even without stripping by mechanical means Crushing and homogenizing via the melt in conventional units high quality materials can be recycled if the components of the Coating is inert, d. H. do not or only slightly degrade the plastic melt. Surprisingly, the surface of those made from such recyclates Molded parts of a quality that require a new high-quality surface finish, e.g. B. allowed by vapor deposition or sputtering. The good material properties mentioned can already be found on pure recyclates, without dilution with Primaware.

The recycling process according to the invention for thinly coated plastic molded parts made of homo- or copolycarbonates is therefore easier and more economical than those who work with decoating. It is also free of solvents and wins the recyclate without a wet step, what protects the environment and energy resources. It is also not necessary to take the recyclate with you Mix Primaware to improve properties.

Coatings which are permissible according to the invention are above all thin and consist of substances which do not degrade the melt of the coated homo- or copolycarbonates or only decompose them in an admissible manner. Particularly suitable layers are therefore those such as are applied to surfaces of plastic molded parts by means of vacuum coating processes of the prior art (see, for example, "Thin-layer technology", ed. H. Frey and G. Kienel, Düsseldorf, VDI-Verlag, 1987, p. 16 ff .). These include vapor deposition and sputtering of metals, alloys and certain compounds as well as the PE-CVD method (p lasma e nhanced c hemical v apour d an exposure of), for example with the man. B. cleans and activates plastic substrates for a coating and finally seals the coated surface transparently against corrosion, aging and other influences. Also suitable for the purposes of the invention are thin layers of lacquer, e.g. B. made of polysiloxane to increase the scratch resistance of plastic surfaces.

To the plastic molded parts made of homo- or copolycarbonates, which are suitable for reprocessing according to the invention Recycling processes particularly suitable include reflectors for Headlights and lamps. With these sophisticated technical parts there is Finishing of the plastic surface followed by a thin layer of aluminum of a sealing layer made of polysiloxane.

The subject of the invention according to claim 1 is therefore a method for the recovery of materials made of thin foreign matter-coated molded parts or semi-finished products made of thermoplastic Plastics, which is characterized in that the molded parts or semi-finished products from homo- or Copolycarbonate exist as a thermoplastic and after possible cleaning and drying a melting process for the polymer portion in conventional plasticizing units either before or during the Processing is subjected to the foreign matter coating up to 10 microns, preferably is up to 1 µm thick and the coating components melt the Do not degrade coated polymers or only degrade them in an admissible manner.

Preferred parameters of the plasticization are those for the respective plastic that can be used according to the invention specified processing conditions of the manufacturer.

In most cases, the thin foreign substance-coated thermoplastic can be used according to the invention Plastic melted and granulated before further processing. But he can also shredded or as regrind using the technically customary injection molding or extrusion processes processed again to usable moldings.

For reasons of constant quality, it is advisable to use the coated plastic that can be used according to the invention with Primaware of the respective variety and possibly different types in or to prepare or process as a mixture.  

The reprocessed coated plastic made of homo- or copolycarbonates can be over it mix with other plastics and process into molded parts. in the Polycarbonates coated according to the invention are preferred with acrylonitrile / butadiene / styrene graft polymers (ABS), with styrene-acrylonitrile Copolymers (SAN) or with optionally elastomer-modified polybutylene terephthalate (PBT) processed into usable mixtures.

The invention thus also relates to the use of regrind or Recyclates of suitably coated thermoplastic polycarbonates for the production of Mixtures with new goods of the same type of plastic or with other plastics.

Recyclates from thin foreign substance-coated thermoplastic polycarbonates can finally with common additives, additives, fillers and reinforcing materials be equipped.

Examples

White colored lamp reflectors were used for the following experiments Bisphenol-A polycarbonate (Makrolon 2403, Bayer AG), and white-colored automotive Headlight reflectors made of a bisphenol A copolycarbonate (APEC HT, Bayer AG) used. The reflector surfaces were coated with pure aluminum and sealed to the outside with a transparent polysiloxane layer. The Total layer thickness was 5 µm for the polycarbonate parts and the parts Copolycarbonate 0.15 to 0.2 µm.

According to the invention, some of the reflectors became recyclates I / A and III / A worked up. Another part was used for comparison with dilute NaOH completely stripped, washed and dried and worked up (Recyclate I / B and III / B).

In addition, rectangular sheets of unused polycarbonate and Copolycarbonate, also pigmented white, manufactured and injection molded the recyclates II / B and IV / B processed. Part of the rectangular panels was made with Acrylic protective lacquer (Lensgard II Rn 3600, colorless, from Morton International) coated and worked up to the recyclates II / A and IV / A.

Table 1 lists the names of the examples.  

Table 1

Recyclate I / A (according to the invention)

The Makrolon 2403 reflectors (average wall thickness 2 mm; 5 µm thick Coating made of aluminum and polysiloxane) were in the delivery state a 6 mm round perforated sieve and before the material test for reasons of Material homogeneity and comparability extruded at 280 ° C and then granulated. The co-rotating twin screw extruder used for this a screw diameter of 32 mm was used for a throughput of 10 kg / h set at 100 rpm.  

Recyclate III / A (according to the invention)

The same procedure was followed with the Apec HT reflectors, with the extrusion temperature Was 320 ° C. The average wall thickness of the parts was 2 mm, the thickness of the coating made of aluminum and polysiloxane 0.15 to 0.2 µm.

Recyclate I / B (comparison)

The Makrolon 2403 reflectors were delivered above a 6 mm round perforated sieve ground and the ground material for 15 minutes with stirring at 100 ° C treated with 4% NaOH. The ground material, which had been completely stripped, was filtered, briefly treated with dilute acetic acid, washed and finally under for Dried polycarbonate usual conditions.

Recyclate III / B (comparison)

The same procedure was used with the reflectors made of Apec HT as for the refurbishment to the recyclate I / B.

Recyclate II / A (comparison)

Makrolon 2403 became rectangular plates (155 mm × 75 mm × 2.5 mm) produced by injection molding, on which a layer is then applied on one side Acrylic protective lacquer in a thickness of 20 to 30 µm was applied (Lensgard II marg 3600, colorless, from Morton International). The coated and hardened Plates were ground over a 6 mm round screen and in front of the Material testing for reasons of material homogeneity and comparability Extruded at 280 ° C and then granulated. The one used in the same direction  rotating twin screw extruder with a screw diameter of 32 mm was set to 10 kg / h throughput at 100 rpm.

Recycled IV / A (comparison)

This reference recyclate was made from Apec HT KU 1-9351, where the same procedure was followed in the production of recyclate II / A. The processing and extrusion temperatures were 340 ° C and 320 ° C, respectively.

Recyclate II / B (comparison)

Uncoated rectangular sheets made of Makrolon 2403 were used in the manufacture of recyclate II / A ground and granulated at 280 ° C.

Recyclate IV / B (comparison)

Uncoated rectangular panels made of Apec HT KU 1-9351 were made as in the manufacture of recycled IV / A and granulated at 320 ° C.

Comparison of material properties

The recyclates from Makrolon (I / A, I / B, II / A, II / B) were at 300 ° C, the recyclates from Apec HT (III / A, III / B, IV / A, IV / B) at 340 ° C to test bars for the following Hosed tests:

• - tensile test according to DIN 53 455 and 53 457
• - Impact resistance at room temperature according to ISO 180
• - Melt index MVI according to DIN 53 735 at 300 ° C / 5 kg (Makrolon) or 320 ° C / 2.16 kg (Apec HT)  
• - Heat resistance HDT A according to ISO 75

All test values determined in accordance with the standard were in Tables 2 and 3 summarized.

Table 2

Test values on recyclates made from reflector material

The comparison in Table 2 shows that the recyclates worked up according to the invention I / A and III / A within the error ranges of the test methods almost identical material parameters  have like the completely stripped recyclates I / B and III / B. Recyclates B are equivalent to recyclates A in the criteria listed.

Another comparison in Table 3 shows the negative influence of thick Foreign matter coatings (<10 µm). Rectangular plates (155 mm × 75 mm × 2.5 mm) made of Makrolon 2403 and Apec HT each with the same Acrylic protective lacquer (Lensgard II Rn 3600, colorless, from Morton International) coated in a thickness of 20 to 30 µm and coated with this lacquer after Process A worked up to the recyclates II / A and IV / A. Likewise, with Move rectangular panels without paint coating (Recyclate II / B and IV / B). Melt-inert foreign matter coatings with a layer thickness of <10 µm (Examples II / A and IV / A) set the Material properties of recyclates compared to recyclates produced according to the invention (Examples I / A and III / A with foreign substance coatings <10 µm) or recyclates of the same Processing without coating (Examples II / B and IV / B) significantly reduced.  

Table 3

Influence of thick inert coatings on the recyclate properties

Claims (5)

1. Process for the processing of moldings and semi-finished products made of thermoplastic materials with thin coatings of largely inert for the plastic melt, characterized in that the moldings and semi-finished products consist of homo- or copolycarbonate as thermoplastic and as whole parts, if necessary after cleaning and drying , processed over the melt under conditions customary for the homo- or copolycarbonate to granules or molded parts that the components of the coating do not degrade the melt of the coated homo- or copolycarbonate or only to the extent that the material properties of the recyclate are not influenced by this polymer degradation and that the coating is less than 10 microns thick. 2. The method according to claim 1, characterized in that the Coating is less than 5 µm thick. 3. The method according to claim 1 or 2, characterized characterized in that the moldings and Semi-finished products processed as shredded or ground parts become. 4. Use of recyclates according to claims 1 to 3 for Production of mixtures with the same type of plastic or with different ones Plastics. 5. Equipment of recyclates according to claims 1 to 3 with conventional Plastic additives such as stabilizers, flame retardants and pigments as well as with reinforcement and fillers such as glass fibers, mica and chalk.