Basically the process is outlined as below:
1.the mixed plastic sheets are collected,crushed into smaller area and washed with detergents to remove contaminants like dust,food scraps and other clinging particles.
2.The cleaned sheets are shredded completely into fine flakes.
3.flakes are separated into PE and PP by selective dissolution methods using a suitable solvent to dissolbe any one polymer ans so the other is separated out.
4.the separated polymers are reprocessed separately in extruders and the extrudates are pelletised and reused for various other applications.
1.comminuting the microcellular polyurethanes
2.admixing a mixture which comprises the comminuted polyurethanes in an amount of from 0.1 to 40 percent by weight, based on the polyaddition mixture, with (a) polyisocyanates, (b) substances reactive toward isocyanates and containing active hydrogens, and optionally, (c) chain extenders and/or crosslinkers, catalysts, blowing agents and customary additives, to prepare a prepolymer.
3.reacting said prepolymer with water, and optionally, additional amounts of (c) to produce a recycled polyurethane.
Chemical processes such as hydrolysis, hydrogenation, pyrolysis and glycolysis are suitable for the recycling of polyurethanes. Furthermore, the polyurethanes can be dissolved in isocyanates and the resulting mixture can, after purification, be reused. Common to these processes is the fact that the polyurethanes can be reintroduced into their production process only at considerable expense and usually not without a loss of quality.
Further processes for recycling comprise the preparation of compact polyurethanes from comminuted elastomers ("flake bonding") or use as filler material in the preparation of new components.Introduction of comminuted polyurethanes into the polyol component for preparing polyisocyanate polyaddition products where air introduced with the polyurethanes caused considerable problems which became apparent in an undesired increase in the viscosity. This problem was solved by wetting the comminuted polyurethanes with volatile hydrocarbons. The addition of these substances may be disadvantageous for systems in which these materials are not used as blowing agents and is to be avoided. A loss in quality of the polyurethane which is prepared using recycled polyurethanes compared with the recycled elastomers can be avoided only with difficulty in the known processes, particularly in the case of microcellular polyurethane elastomers.
ABS is extensively used in the manufacture of inexpensive, durable products. The durability of ABS has made it a primary material in the manufacture of products such as, computer housings, televisions and computer monitor housings, automobile components, etc.
Unfortunately, however, ABS is somewhat expensive when supplied in its purest form. As such, the cost of manufacturing some products with ABS is prohibitively expensive despite the fact that the material characteristics of the ABS are well suited for the manufacture of the products.
Where the recycled goods are composed of a single plastic component (for example, plastic soda and milk containers), recycling is highly cost effective and leads to many useful products. However, the necessity of separating the assortment of plastic components prior to shredding and granulating makes recycling commingled plastic products highly time consuming and prohibitively expensive. Existing recycling techniques are, therefore, not appropriate where the recycled goods include many components composed of various plastics.
For example, where it is desired to recycle the plastic components of a computer housing (which is primarily composed of ABS, PCABS, and other plastics) to take advantage of the recycled ABS, the computer housing must first be separated into various components representing the many plastics used in the construction of the computer housing. This is highly time consuming, and makes recycling computer housings cost prohibitive. Such limitations are commonly found with ABS products one might consider appropriate for recycling.
The lack of an effective recycling process for those products already manufactured from ABS leaves previously used ABS products wasted once the useful life of the manufactured product is reached. Many materials have found a second life through recycling. However, a process for refining the used material must be developed before the material may find a second life in another product. Often, the second life of a product requires that the material be used in an environment where the aesthetic appearance of the material is not as important as when the material was used for its original purpose.
Unfortunately, no process is currently known for effectively and efficiently recycling ABS for subsequent use. The present process for recycling ABS in a manner permitting previously used ABS to obtain a second life. The present process employs shredding, separating and blending to recycle used ABS for subsequent use in other products, for example, substrates of decorative laminates.
1.Shredded ABS blend is separated from metallic impurities by magnetic separator.
Tyres are a disposal problem as they consume considerable airspace relative to their weight and cannot be compacted.Re-treading tyres is still one of the best ways to obtain maximum use from them while temporarily reducing their contribution to the waste stream. Ultimately, however, tyres still need to be disposed of.It is worth noting they have a calorific value well above that of coal, and therefore lend themselves to uses as a fuel in cement kilns and ordinary furnaces for the production of electricity.
• Use of properties
This type of recovery is not only lower in the waste management hierarchy, but is also ahigher technology requiring sophisticated equipment. The applicability of such technologiesfor small-scale applications in developing countries is very limited. We will therefore lookonly very briefly at a couple of processes. Chemical recovery is the process of heatingwaste rubber reclaim, treating it with chemicals and then processing the rubbermechanically.
One form of thermal recovery is pyrolysis. This involves heating the tyre waste in theabsence of oxygen which causes decomposition into gases and constituent parts. It is atechnology which is still immature in the tyre-reprocessing field.
Recycling of PET Bottles is the activity whereby bottles made out of PET are collected, sorted and processed in order to reuse the material out of which they are made.
In many countries, PET plastics are coded with the number 1 which is found inside the universal recycling symbol, usually located on the bottom of the container.
PET is used as a raw material for making packaging materials such as bottles and containers for packaging a wide range of food products and other consumer goods. Examples include soft drinks, alcoholic beverages, detergents, cosmetics, pharmaceutical products and edible oils. PET is one of the most common consumer plastics used.
The empty PET packaging is discarded by the consumer after use and becomes PET waste. In the recycling industry, this is referred to as "post-consumer PET." Many local governments and waste collection agencies have started to collect post-consumer PET separately from other household waste. The collected post-consumer PET is taken to recycling centres known as materials recovery facilities (MRF) where it is sorted and separated from other materials such as metal, objects made out of other rigid plastics such as PVC, HDPE, polypropylene, flexible plastics such as those used for bags (generally low density polyethylene), drink cartons, and anything else which is not made out of PET.
Post-consumer PET is often sorted into different colour fractions: transparent or uncoloured PET, blue and green coloured PET, and the remainder into a mixed colours fraction. The emergence of new colours (such as amber for plastic beer bottles) further complicates the sorting process for the recycling industry.
This sorted post-consumer PET waste is crushed and pressed into bales, which are offered for sale to recycling companies. Transparent post-consumer PET attracts higher sales prices compared to the blue and green fractions. The mixed colour fraction is the least valuable. Recycling companies will further treat the post-consumer PET by shredding the material into small fragments. These fragments still contain residues of the original content, shredded paper labels and plastic caps. These are removed by different processes, resulting in pure PET fragments, or "PET flakes". PET flakes are used as the raw material for a range of products that would otherwise be made of polyester. Examples include polyester fibres, a base material for the production of clothing, pillows, carpets, etc., polyester sheet, strapping, or back into PET bottles.
PROCESS FLOW CHART
PET containers are identified by a resin identification code imprinted on the side or bottom of the container. PET bottles in the United States, which are usually clear or transparent green, carry the resin identification code " 1 " and the symbol "PETE." They may also be recognised by the dot, or circular gate, centrally located on the bottom.
For any collection program to succeed, consumers must become educated and motivated so that identification and collection of recyclable containers becomes a routine activity. Most consumers readily recognise PET soft drink bottles. However, the use of PET has expanded rapidly into other areas such as containers for water, sports drinks, food products, alcoholic beverages, household products, and cosmetics. Accordingly, it becomes vital that consumers understand and use the codes for proper identification of recyclable containers.
CLEANING AND SEPARATION
Once collected, containers are forwarded to recycling locations where they are run through grinders that reduce them to flake form. The flake then proceeds through a separation and cleaning process that removes all foreign particles such as paper, metal, and other plastic materials. Having been cleaned according to market specifications, the recovered PET is sold to manufacturers who convert t into a variety of useful products such as carpet fibre, strapping, moulding compounds, and non-food containers.
There are about three dozen recycling companies in operation, two-thirds of which are located in North America. These plants have the cleaning and separation technology to convert post-consumer bottles to flake for sale to end users. Their total capacity approaches together 436 thousand tonnes (960 million lb) on a three-shift basis - evidence that there is capacity available to handle the growing demand for recycled PET.The recycler is the vital link between the collection process and the end users having need of the recycled resin. Industry associations also play a valuable role by bringing communities and recycling outlets together.
SIMPLIFIED METHANOLYSIS PROCESS-SCHEMATIC
USES OF RECLAIMED PET
About three-fourhts of reclaimed PET is used to make products such as fibres for carpets, fibrefill, apparel and geotextiles. Much of the remainder is extruded into sheet for thermo-forming, stretch blow-moulded into non-food containers, or compounded for moulding applications. The chemical process for producing PET can be reversed by two commercially available depolymerisation methods - methanolysis and glycolosis.
These processes subject clean flake to a chemical reaction that reduces it to either a monomer or the original raw materials. These materials can then be purified and subsequently re-reacted into "new" PET for use in food-contact applications.
In some countries, reclaimed PET is used for food packaging by incorporating it into the core layer of a three-layer sandwich structure or by subjecting it to special cleaning processes.
Many communities send their trash to state-of-the-art, waste-to-energy incineration facilities, reducing the volume of waste going to landflls by as much as 90%. As stated earlier, incineration for energy recovery accounts for 17% of all solid waste disposal in the United States.
In Europe, the percentage is 30%, with Switzerland burning about 80%. As shown below, plastics have an inherent energy value higher than any other material commonly found in the waste stream.
While a growing number of PET containers are being recycled and others are being incinerated, some inevitably find their way into landfills. What happens to these containers? Virtually nothing. They contain no noxious components that might leach into underground water supplies, nor do they decompose. Landfill digs, conducted by noted professor of archeology Dr. William Rathje, indicate that many landfilled items, including some foods and paper, remain virtually unchanged for decades.
Since very little decomposition takes place in a modern landfill, such sites are, in effect, solid waste repositorios. Consequently, landfills simply fill up, with little or no decomposition taking place. Hopeftilly, fewer and fewer PET containers will go into landfills. However, those that do will be crushed to their minimum size, and their inert nature will not negatively impact the landfill.
The objective is to to provide a recycling process for carpeting material containing nylon polymers and/or nylon fibers.
Another specific objective is to recover Nylon 6 and Nylon 6,6 from nylon containing carpet scraps and used carpeting.
A further object is to separate and recover nylon polymer from carpeting containing other polymers such as polyesters, polyamides, P.E.T. (poly-ethylene terepthtalate) and other polymers as well as natural fibers.
This process and the steps thereof relate to the recovery of nylon, particularly Nylon 6,6 both from home and commercial carpets. Carpet containing Nylon 6,6 is dissolved in a hot, highly pure glycerol at elevated temperatures. At high temperatures, nylon oxidizes with oxygen and/or hydrolysis with water. To prevent oxidation various stabilizers may be added to the solvent. Alternatively, working under a nitrogen environment renders an effective protection against nylon degradation from both oxidation and hydrolysis.
Upon dissolution, the solution is quickly withdrawn to a dry vessel where it is quickly cooled to 40 degrees Celsius or lower. The solution is washed with water to remove traces of glycerol, then filtered, and lastly dried under vacuum at 40 to 60 degrees Celsius to recover the nylon polymer. The following is an example of the method used in practicing this recovery and recycling process:
1. 1200 ml of pure glycerol is heated to and maintained at 205 C. and 1 ATM. of pressure in a stirrer equipped vessel where it is uniformly stirred at a moderate speed.
2. Meanwhile, a constant stream of nitrogen gas is applied to the solvent as it heats up to purge out any residual oxygen.
3. 100 grams of Dupont Stainmaster carpet is added to the hot solvent.
DUPONT STAINMASTER-NYLON CARPETS
4. The initial carpet fiber is sample and found to be Nylon 6 with a relative viscosity of 1.7.
5. 15 minutes after all the nylon is dissolved, the solution is pumped out of the heating vessel via a heated 0.25 inch diameter stainless steel pipe into a dry flask that is sitting in an ice bath.
6. When the solution cools down to 40 C. or below it is washed with water at a ratio of 20:1 by volume and filtered, for the final wash.
7. For the final wash potassium iodine (KI) is added to the water as a heat stabilizer for future processing.
8. The final solution is filtered and the cake is dried in an oven purged with nitrogen then under vacuum allowed to dry at 45 C. for three days.
9. The final material is checked for its purity and relative viscosity (RV). The final material exhibited an increase in relative viscosity to 2.21.
The primary criterion for plastic recycling is the purity of the end product. Minute contamination of the recovered plastic can greatly reduce the value of the recovered plastic. Previous plastic recycling technology relies on "float-sink" technology, according to which the target plastic was separated from waste of different specific gravities by grinding the feed material and choosing a liquid of appropriate specific gravity to float off the waste and allow the target plastic to sink, or vice versa. However, this method did not produce an end product of sufficient purity. Recently, hydrocyclones, previously used in mineral separation and other industries, have been applied to plastic separation, and these devices have produced a good improvement over the old technology.
This recycling plastic containers comprising the steps of:
a) grinding said containers into flake-size plastic pieces approximately 3/8-inch or less in maximum dimension.
b) removing light materials from said plastic pieces by air classification
c) introducing said plastic pieces into a wash bin containing turbulent water at ambient temperature and cold water detergent
d) drying said plastic pieces
e) introducing said plastic pieces into a wash bin containing turbulent water at a temperature between 180 and 210 degrees F. and hot water detergent
f) dewatering said plastic pieces
g) separating said plastic pieces from other residue by hydrocylone and
h) drying said separated plastic pieces.
Fast food restaurant and cafeteria waste in addition to containing large amounts of PSF also commonly comprises a large proportion of paper products (such as bags, cups and napkins), wax-coated paper products, condiment containers, plastic eating utensils and food morsels.
Recycled polystyrene foam can be used to manufacture a wide variety of products such as plant pots, plastic desk organizers, foam construction insulation etc. and is therefore, a valuable product. Further, polystyrene foam, like most plastic, takes a very long time to degrade when placed in landfills. Therefore, it is desirable to recycle polystyrene foam to reduce the amount of such plastic in municipal landfills.
FLAIL MILL(Helylpatterson Inc.)
The waste is then continuously fed into an air classifier. In a preferred embodiment, the air classifier is a large rotating cylinder which uses an air stream to carry lighter materials, such as napkins and PSF through the cylinder, while the heavier waste, primarily wax coated containers and remaining food, drops out of one end of the classifier and is removed from the primary stream of waste. The light fraction output of the air classifier, which comprises primarily PSF and paper, is fed into a plenum chamber where the air velocity is reduced allowing the light fraction waste to settle to the bottom of the chamber.
The light fraction waste is then continuously delivered to a reversible conveyor which can bring the waste either to a batch pulper or a continuous pulper. Either of the pulpers essentially mixes the waste with water and vigorously agitates the mixture so as to break down the paper waste to paper pulp. The water and paper pulp is then separated from the PSF by passing the mixture through a screen which allows the water and paper pulp to pass through but retains the larger PSF waste particles. The PSF is air conveyed from the screen to a granulator. The particle size is further reduced in the granulator.
The PSF is then dried and prepared for shipment. The paper pulp and water which passes through the screen is pumped to a static sieve where the water and paper are partially separated. The water is then recovered and recycled back into the apparatus. The paper pulp is further fed through a de-watering screw where additional water is removed and recycled.
The de-watered paper pulp is then collected in containers and can be sold for recycling. The undersized waste removed in the rotating trommel and the "heavy" waste removed in the air classifier is combined and delivered to a shredder where the size of the waste is further reduced. The output of the shredder is sent to a pellet mill, which compresses the waste and extrudes it into small pellets. To ensure that the pellets do not readily crumble, they are air cooled in a pellet cooler before storage.
Production residues: these arise mostly in the form of off-cuts, in the factory or plant, as the product is made. For many years such valuable `waste' has been recycled as a matter of good housekeeping and only a small proportion needs to be disposed of as waste to landfill or by combustion.
Installation waste: this results from sold products, such as flooring, cables and pipes, being cut to size during installation. In recent years, the PVC industry has become active in organising collection systems and in recycling these `waste' products back into new products.
Post-consumer waste: products which have fulfilled their service life and end up in waste streams from different domestic and industry sectors.
Incineration with Energy Recovery
Oil used in PVC production can be utilised at least twice, making positive use of its high heat value, through incineration with energy recovery. Incorporating PVC consumer products at the end of their useful life in controlled municipal incinerators reduces the need for additional fuel and reduces the amount of PVC going to landfill. A number of independent studies have demonstrated that PVC in addition to the natural presence of chlorine in waste, does not increase the generation of potentially harmful emissions. Modern incinerators are operated to the highest standards and equipped with pollution control equipment that minimises the release of emissions to the environment.
Vinyloop is a process of recovering PVC plastic from composite materials through dissolution and precipitation.
The technical process of Vinyloop can be described fairly simply; it includes only 6 main steps. To begin the cycle, composite waste is collected and brought to the plant. Much of the material is preprocessed but some of this step takes place in the factory. Some operations that may be performed are, “a cleaning step (washing, etc.) reducing the size for fast dissolution (by cutting, grinding, milling, etc.) and a homogenization step.”
After pre-treatment, the material is sent to a dissolution chamber where the solvent, methyl ethyl ketone, dissolves the PVC and its additives. While these factors are dissolved or suspended, the insoluble materials of the original composite remain out of solution and can thus be removed in subsequent steps.
The separation of the insoluble materials occurs in the next tank. There are many techniques to filter the solid from the solution such as, “centrifuging, decanting, or cycloning,”, the particular method used is mandated by each individual situation. “After separation, the secondary material is: washed with pure hot solvent to eliminate virtually all of the dissolved PVC compound, stripped with steam to recover all the solvent, then discharged.”1 In this way all material is removed from the PVC. This is a very important step to yield pure PVC material for reuse.
The next stage in the process is the precipitation of the dissolved PVC. At the onset of this stage, it is possible to integrate more additives into the dissolved PVC to achieve a variety of characteristics. At the Ferrara Plant, a plasticizer is added to the PVC in order to generate a more flexible and less brittle product. Steam is then injected into the solution, evaporating the solvent completely, leaving an aqueous slurry of PVC and additives. The unwanted material from the composite as well as the solvent are thus removed. The evaporated solvent condenses in its original chamber, ready to dissolve another batch of composite material. This closed loop cycle has an effective retention rate of 99.9%, rendering the solvent a technical nutrient in this process.
The final stage in the Vinyloop is the drying phase. The aqueous solution of PVC is dried and the effluent water filtered to remove impurities. The dry R-PVC forms pellets (a significant occurrence due to that form’s ease of use in the plastics industry). Dry pellets are easy to package and ship out to be molded into other products. Many times these pellets can comprise 100% of the material for a new product, but when not, any percentage of R-PVC can be added to virgin PVC in product formation.
APPLICATION OF PROCESS
The Vinyloop process was developed by Solvay SA’s
The materials suited to the Vinyloop process are composites, such as PVC coated wire, coated fabrics, flooring, or automotive products. While in the past it was not possible or feasible to separate plastic from other materials in composites such as these, the Vinyloop process allows for such separation through its dissolution and precipitation system. It allows for the retention of the PVC’s original character by preserving its stabilizers, plasticizers, colorizers, etc. This elicits a 100% direct reuse of R-PVC produced by Vinyloop.
HOW USEFUL IS IT TO PLASTIC INDUSTRY?
Vinyloop is one of few processes which can effectively separate PVC from a composite material. It is also a recycler of post consumer waste. This is therefore a significant diverter of plastic from the waste stream. While other cruder plastic recycling processes cannot reclaim a pure form of PVC from a material, leading to subsequent lifescycles of lower quality, Vinyloop yields a very pure product which is of comparable quality to virgin material.
Further research will determine the viability of these ideas concerning the Vinyloop process, specifically the test of whether the R-PVC can be reintegrated into the composite products it originated from and be continually processed by Vinyloop at the end of each of its lifecycles.