DE4309427A1 - Process for the recycling and disposal of thermoplastic waste - Google Patents

Abstract

In the process described, individual constituents are specifically dissolved out of the mixtures of thermoplastic waste (scrap), the solution is freed from insoluble substances, purified and then converted back into high-molecular-weight, fresh, thermoplastic materials by a graft polymerisation or copolymerisation when the solvent employed is a monomeric component in which one constituent of the polymeric waste mixture is soluble.

Description

Annually fall in the countries of the European Ge community over 100,000 tons of thermoplastic Plastic waste. The reprocessing and Disposing of this waste is an urgent matter become world problem. Although there are quite a number of Refurbishment procedures and possibilities exist intensive improvement and improvement in many areas Optimization of "recycling processes" worked. At the Thermoplastic waste is the most common milled and re-extruded melted.

The melt is pressed through screening devices to remove the contaminants. Such rain rate can be in certain percentages of a new product added or ver to less demanding parts be working. Are such thermoplastic art waste from a single material, but consist of a mixture of different ones Plastic grades, so is a reuse in the  Usually not possible. Because with every makeover the melt undergoes thermal damage, associated with a decrease in the physical egg after all, you no longer get property values recoverable waste.

Processes by depolymerization are also known the polymeric thermoplastics or by hydrolysis Polycondensates, the monomeric starting materials to win. For pyrolytic and other highs temperature processes result in cracked and tar-retaining residues, their disposal difficult and partial is very expensive. Also known are gentle methods in which certain polymers by specific solvents are extracted. Because of the poor solubility of high polymer substances you need large amounts of solvents that energy and costly can be recovered must and are therefore not economically feasible.

According to the method according to the invention, it is possible to avoid the disadvantages mentioned and in inn scientifically a variety of new organic Get materials if you look at the thermoplastic Plastic waste in a solution or melt one introduces monomeric starting component, the insoluble Shares removed by filtration  and those dissolved in the monomeric component polymeric fabrics from thermoplastic art polymerized waste. You can graft polymers are formed, but also high molecular ones and long chain homopolymers when the polymer melt a building block of the in the monomeric component contains dissolved poly- or oligomeric thermoplastics. So you can, for example, low molecular weight and as Material unusable 6-polyamide waste, dissolved in Caprolactam, in high molecular and therefore high quality Convert polyamide 6 materials.

The reprocessing after is particularly interesting the method of filled or Metal inserts containing injection molded parts that have been retired due to inoperability. Fill substances such as kaolin, chalk, glass balls, glass fibers, inorganic pigments and metal parts settle on Bottom of the melting pot after the thermopla material dissolves from the monomeric component has been. In certain cases, it is also possible to fei ne, only very slowly settling particles through Addition of precipitants, such as. B. diatomaceous earth, precipitated silica, activated carbon, aluminum silicates, Aluminum hydroxide, precipitated chalk, bentonite or Fill in or decolour kaolin varieties, especially when using inorganic pigments  were colored. Thermoplastic plastic wastes with a defined composition ver Different polymers can be made into plastic rework alloys or hot melt adhesives. The organic materials thus obtained are much cheaper to win because the thermoplastic waste used are available much cheaper than the monomers produced synthetically Raw materials. When using 40-90% thermoplastic waste is reduced accordingly the polymerization costs, and doubt without can large amounts of existing thermopla wastes to relieve the environment such as which can be worked up without residual portions of difficult to dispose of waste that one require special final storage, as is the case with a A number of other recycling processes are the case.

In the following the invention is illustrated by a number explained in more detail by examples.

example 1

Be in a heated stirred tank

421.5 kg of caprolactam
81.8 kg adipic acid
39.8 kg AH salt (adipic acid hexamethylenediamide)
87.9 kg of trimethylene hexamethylene diamine

added and then heated to 90-95 ° C.  

485.1 kg of PA-12 powder (undersize from the sinter powder production) are added to the melt. The temperature of 90 ° C. is maintained with stirring until a homogeneous melt has formed, which is pumped over a sieve filter into a 2 m ³ autoclave. The autoclave was previously purged with nitrogen. After the entire melt has been pumped into the autoclave, 5.65 kg of phosphoric acid, dissolved in 28.4 kg of water, are added. The autoclave is then flushed again with nitrogen by pressing 5 bar of nitrogen, releasing the pressure and repeating the process two or three times. Finally, 5 bar of nitrogen are specified and the reaction mixture is heated to 250 ° C. As soon as the pressure has risen to 18 bar, the pressure is carefully released and an excess pressure of 16 to 18 bar is maintained. After a reaction time of 5 hours, the autoclave is expanded to 0.5-1 bar and the temperature is reduced to 190-200 °. By repressing nitrogen, the melt is extruded in the form of a strand within half an hour, the strands are cooled to about 25 ° C. in ice water and comminuted. The co-polyamide thus obtained has a melting range of 105-112 ° C, a solution viscosity of 1.7-1.75 measured in a 1% solution in formic acid, the melt viscosity at 160 ° C is 4500 mPa · s, the melt flow index (MFI) 30-40, ie at 1600 G and 2.16 kg / cm ² pressure, 30-40 g of melt were pressed out in 10 minutes. After grinding with cooling with liquid nitrogen to a powder with a grain size of 1-200 µm, a hot melt adhesive is obtained which is used in the textile industry.

Example 1a

Instead of PA-12 powder for sintering purposes is no longer suitable, can alternatively be used put: Pa-12 regrind, crushed Petrol hoses from decommissioned motor vehicles, finally you can coat with PA-12 powder Parts made of Me or coated with PA-12 tall, mainly from unusable dishwashers or washing machines be taken, whereby one encased with PA-12 Metal parts in a strainer basket in the monomers melt dips and waits for the PA-12 Layer is detached and the bare metal is visible cash.

Example 1b

Hot melt adhesive with analog properties is obtained if you have combined film waste from PA-6 / PA-12, PE / PA-12 or PA-12 / PA-66. When reprocessing of combination film waste consisting of 60% PA-6 and 40% PA-12 become 313.5 kg caprolactam, 81.8 kg Adipic acid, 39.8 kg AH salt, 87.9 kg trimethylene  hexamethylenediamine in the described in Example 1 melted in the same way. In the melt 184 kg of combined film waste entered, one Have a water content of 2.1%. Then 413 kg PA-12 powder (undersize from the sinter powder plant). After everything has resolved, it will be the same Proceed as described in Example 1. Again you get a hot melt adhesive with the previously described properties.

Example 2

Polyhexamethylene adipamide (66-polyamide), which by repeated grinding and remelting the associated thermal damage in the Molecular weight was reduced very much, so it for the production of inferior thermoplastic ischer moldings was no longer suitable, can follows to a high-quality adhesive raw material be:

800 kg of molten and 800 hot caprolactam is pumped into a stirred autoclave. To do this 940 kg 66-polyamide regrind with a water content of 2.1% and a relative solution viscosity of 2.00-2.05. Dissolve with stirring and nitrogen flush the 66-polyamide particles in the caprolactam melt. Then 0.02% phosphorous acid set, 5 bar of nitrogen and the reaction  mix to 260-265 ° C within 3-4 hours heated up, the pressure rises to 12-18 bar at. Pressure and temperature then become two Maintain hours. Then the pressure is through relax slowly within three hours Reduced 1 bar and the product temperature to 220- Lowered 230 ° C. After a polymerization time of 8 hours you get a polymer melt that is pumped into an intermediate boiler, the under a vacuum of 15-50 hPa. In this vacuum About 3-5% caprolactam are converted in vacuo distilled off, which is fed back to the process. The one largely exempted from volatile components Melt is extruded or extruded through a discharge pump squeezed into a band, quenched in water and crushed. A 6/66 mixed polyamide is obtained which dissolved in alcohol as an adhesive for gluing Le the and polyamide fittings is suitable.

Example 2a

You get the same adhesive raw material when you put on place of dismantled 66-polyamide waste filled 66-polyamide waste containing 35-50% of inorganic fillers and / or Glass fibers or glass balls are used. The insoluble residues of inorganic fillers are separated over sieve filters, so that one Mixed polyamide with a share of 53-54%  6-polyamide and 46-47% of 66-polyamide.

Example 2b

Inoperative will become the starting material Ball bearings used, the inner rings are made of 66-polyamide reinforced with 35% glass fibers. The thoroughly degreased and cleaned ball bearings are in a 150-160 ° C hot caprolactam melt dipped, expediently the ball in sieve baskets in the caprolactam melt dives. By pumping the lactam melt over Easy-change filter devices become the glass fibers severed. After the complete dissolution of the The steel balls and Outer rings high-gloss and clean from the melt be taken. At a ratio of Caprolac tam to hexamethylene adipamide in mixed polyamide as 1: 1, you get an adhesive raw material that works well in dissolves polar solvents and in this form as Liquid glue in the leather industry and especially here which is needed in shoe manufacturing.

Example 3

Housing parts from household appliances or removed Fan blades from motor vehicles that are scrapped should be, consisting of colored 6-polyamide with a glass fiber content of 30%, are 150 ° C hot caprolactam dissolved, the melt  is continuously pumped around and filtered. After the polyamide parts have completely dissolved and removal of the glass fibers and the insoluble, inorganic pigments are 0.02- 0.03% acetic acid added and then in one Stirred autoclave pumped over, the ge with nitrogen was rinsed. After injecting 4-5 bar nitrogen the reaction mixture is heated to 260 ° C, thereby the pressure rises to 10-15 bar. Pressure and tem temperature is maintained for two hours, after that the pressure by slowly relaxing within three hours to 1 bar and the product temperature lowered to 230 ° C. The viscosity of the Polymer melt is due to the current consumption of the An drive motor of the stirrer monitored. After a butt The melt becomes lymerisation time of eight hours in a tubular, under vacuum Pumped over boiler. At a vacuum of 10-60 hPa about 5% of the unreacted caprolactam distilled off in vacuo, the process again leads. The most volatile freed melt is then over a Thursday sierpump fed to an extrusion system in the the remaining monomeric caprolactam from the melt aspirated, condensed and also like the process which is fed. The dealaced polyamide melts are over in this extrusion plant  a synchronized dosing belt scale all necessary other additives such as lubricants, heat stabilizers, pigments and / or fillers, such as Glass fibers, glass balls, mineral fillers or other polymers added.

The homogenized melt is stranded out presses, quenched in water, granulated and that Granules to a residual moisture of less than Dried down 0.1% and moisture-proof packed up.

The polyamide-6 obtained by this process Injection molding compounds have physical properties that are composed of the same Products made from pure, waste-free Preproducts, practically no differentiate.

Example 4

Packaging waste made of polystyrene foam (Styropor®) are at room temperature in monostyrene, the 12 Gew. Percent contains unleaded petrol, dissolved until that Solution contains 50-55% polystyrene.

For this, 0.05 mol of dibenzoyl peroxide (BPO initiator) stirred in. The solution is canned (canned) or metal containers with a content of up to 5 l. a filled, whereby the vessels are only about 80% full become. Then close the vessels tightly  with clamping ring covers and store them for 2-3 weeks in a water basin with 35-40 ° C warm water. The water is, if possible, a solar heating heated.

By taking samples from individual doses, through Measurement of the solution viscosity checks whether that Mixture is polymerized. As soon as it does is cooling the vessels with the polystyrene that contains about 5-6% petrol as propellant, on 20- 25 °, opens the vessels, removes the glass like blocks, crushed them until you get fragments contains up to a size of about 5 mm. Out of it can be cooked by stirring in the fragments of the water in turn produce polystyrene foam.

Example 4a

Polystyrene foam waste is stirred into pure styrene at room temperature until saturation occurs. 500 ltr. the viscous solution is pressed through a sieve filled with precipitated and dried chalk into a nitrogen purged 2.5 m ³ polymerization kettle into which 1000 l. demineralized water with 1.22 kg of potassium peroxodisulfate and 0.5 kg of sodium dihydrogen sulfate and 10 kg of sodium oleate or sodium lauryl sulfate were introduced as an emulsifier. The emulsion polymerization is carried out in a known manner.

Example 5

In a dissolving kettle with 740 kg styrene, 360 kg Housing parts made of a styrene / acrylonitrile copolymer sat (SAN 26), the 6 percent by weight threaded bushings Metal included in a strainer basket in the mono immersed in styrene. By pumping over the pump for several hours 30-35 ° C warm, stabilized styrene dissolves the styrene / acrylonitrile copolymer in styrene and the metal bushings remain in the sieve baskets back. The viscous solution is about what Serfree calcium carbonate filled sieve filter in a nitrogen purged polymerization boiler pressed. To remove the stabilizer Phenol becomes the granulated, anhydrous calcium carbonate a little quicklime (CaO) added. Then 260 kg of acrylonitrile are pumped in and that entire reaction mixture in a known manner poly merized. A styrene / acrylonitrile copoly is obtained merisat with physical properties that the a SAN 26 made from 74% pure styrene and 26% acrylonitrile. That from 30 parts Copolymer and 70 parts of monomers SAN can again produce new parts  can be used in the injection molding process.

Example 5a

A solution obtained according to Example 5 from 30 Tei len SAN 26 in 74 parts styrene and 26 parts acrylic 30 parts of a styrene / butadiene copoly become nitrile merisates, consisting of 30 parts styrene and 70 Share butadiene, added and in a known manner polymerized. You get a high impact ABS Polymer that is injection molded, but also in the deep drawing process into new workpieces can be.

Instead of adding 30% of the styrene / butadiene Copolymers can as a soft component 30-40% of a butadiene / acrylonitrile copolymer 72% butadiene and 28% acrylic contains nitrile or the same amount of a poly butadiene rubber (BUNA).

Claims (3)

1. Process for the reprocessing of thermoplastic plastic waste, characterized in that the waste is dissolved in a liquid, monomeric component, freed from insoluble foreign matter, cleaned and then by graft or mixed polymerization again in high molecular weight, new, thermoplastic materials be transformed. 2. The method according to claim 1, characterized in that that at least one thermoplastic component in the plastic waste in the submitted monomer Solution or melt is soluble. 3. Claim according to 1 and 2, characterized in that the insoluble components of the used Plastic waste are completely separated, so that the subsequent polymerization and Regeneration process is not blocked.