There are various types and shapes of waste plastics. In practice, many recycling methods have been created. Some examples are introduced below for reference.

1. Adding film

Film is a major category of plastic products. It has many types and generally has a short service life. It is one of the main types of recycling and recycling. Below is an introduction to the form according to its use and examples.

（ 1) Agricultural films. Agricultural films mainly include mulch films and shed films. Mulch films are mainly PE films. Shed molds include PE, PE/EVA, and PVC films. When recycling, PE and PVC films should be distinguished. Agricultural films It is generally dirty and often contains soil, sand, grass roots, iron nails, iron wires, etc. Iron impurities need to be removed and cleaned. The main recycling method is granulation. If manual sorting and cleaning conditions are available, often After cleaning and drying, the waste film can be directly used to produce plastic products by hot extrusion, such as basins, barrels, plastic flanges, etc.

The uses of waste agricultural film recycled pellets are as follows

1. PE recycled granules. PE recycled granules can be used to produce agricultural films, fertilizer packaging bags, garbage bags, agricultural recycled water pipes, fences, tree supports, pots, barrels, garbage bins, geotechnical materials, etc.

2. PVC recycled pellets. PVC recycled pellets can be used to produce heavy packaging bags, agricultural water pipes, shoe soles, and other packaging films. The materials of packaging films include cellophane (cellophane), PE, PVC, PP, EVA, PVDC, PA, PET and various composite films. Single-layer packaging films of one material, after sorting and cleaning, can be directly made into plastic products like agricultural films or granulated into various products. Products. Composite films include composite films of different plastics and films made of plastic, paper, aluminum foil, and other materials. The regeneration process after recycling is more complicated, such as: multi-layer plastic composite films. Multi-layer plastic composite films include PE/ PP, PE/EVA/PE, PE/adhesive/PA/adhesive/PE, PP/PVDC, etc., before recycling, different materials must first be separated. Solvent separation method can be used for separation.

Paper-plastic composite film, paper-plastic composite film needs to be separated from paper and plastic before recycling. This is also the method of paper-plastic composite separation. The separation equipment is a chromium-plated hollow barrel with electric heating. The barrel is filled with A hollow cylinder with blades. The barrel and the hollow cylinder rotate in opposite directions. The crushed paper-plastic mixture is added to the barrel. The plastic on the heated mixture in the barrel melts and is discharged from the lower part of the barrel. The hollow cylinder The air in the tube takes away the exhaust gas.

Aluminum-plastic composite films, including BOPP/aluminum, PE/aluminum, etc., are used for various food packaging. The actual use of aluminum-plastic composite flexible packaging bags It is a kind of mixed waste, which is difficult to recycle. The main treatment method abroad is incineration to recover heat. In China, there are methods of incineration to extract aluminum and crushing and adding fillers to make low-grade crude products, but the effect is not ideal. Here we introduce the use of aluminum's conductivity. An example of manufacturing antistatic functional materials. The process is as follows: aluminum-plastic composite waste - cleaning - crushing - sieving - pellet - aluminum powder - additives - extrusion - semi-finished product - extrusion - finished product. Clean the aluminum-plastic composite waste , crushed and screened for 10 days, and then pelletized. This process can use the pelletizer of Beijing Plastic Machinery Factory. The pelletizing process conditions are water spray: 0.8 liters of 95 degree water, feeding time: 3min; air extraction time: 5min, crushing time: 10min. Each processing is 15 kilograms. The pelletized material is then extruded by an extruder to form a semi-finished product. 20% aluminum powder, flame retardant, compatibilizer and other additives are added to this semi-finished product, and then the pellets are extruded and selected. Products can be obtained and used as conductive materials.

3. PET film, in the plastics industry, PET is mainly used as film and bottles, while the film can be used as packaging, decoration, tape base or capacitor insulation, PET sheets are also used as photographic film base, PET is also widely used in fiber, film and fiber The physical viscosity of PET is slightly different than that of PET paper for bottles. Therefore, recycling is also slightly different.

The scraps produced by PET film and fiber production plants can be used to wait for polyester/epoxy resin powder coatings, generally

The relative molecular mass of these scraps is about 20,000, and the melting point is above 260 degrees. They form a single linear PET. By alcoholizing such scraps with polyol at 250 to 260 degrees, the relative molecular weight of about 2,000 to 260 degrees Celsius can be obtained. Low melting point oligomer polyester of 5000. The oligomer polyester is polycondensed by adding dibasic acid anhydride and esterifying agent at 200 to 220 degrees to obtain an acid value of about 3.05 mgKOH/g, a softening point of about 85 to 105 degrees, and a glass transition temperature of less than or equal to 50 degrees. The product is used to make polyester/epoxy resin powder coatings.

Polyester formula for polyester/epoxy resin powder coatings

Raw material dosage Raw material dosage

723.6g PET scraps, 0.98 mol dibasic acid anhydride

1.71 mol glycol, 0.1 catalyst

PET industrial waste can also be used as an adhesive .Japan's Osaka Municipal Industrial Research Institute and Fuji Photo Film Company react with PET industrial waste and glycerin to make adhesives for metal bonding. PET industrial waste can also be made by modifying adipic acid or ethylene glycol. Hot melt adhesive, used for bonding flexible materials, such as cloth, leather, paper, plastic, aluminum, etc. Performance of polyester/epoxy resin powder coating

Indicator Name Technical Standard Indicator Name Technical Standard

Appearance is flat and smooth, with slight orange peel gloss allowed/gt; 85

Fineness/mesh gt; 180 Flexibility/mn 1

Curing time/ (min/oc) 20/180 Hardness gt; 2H

Horizontal flow/[mm(oc.min)] gt; 25/180—5 Moisture resistance (40 oc -2 oc, RH95 _3)/d 21

Acid leaching resistance of 25H2SO4, the coating film is intact for 90 days at room temperature

Impact strength/kN/cm 50 Alkali leaching resistance of 25NaOH4, the coating film is intact for 90 days at room temperature

Attachment Strength (Grade) 1-2 Resistant to salt water immersion 10NaCL 90 days at room temperature, the coating film is intact

Waste PET film, sheet or fiber plus propylene glycol, styrene, glycerol, phthalic anhydride, cis-butyl Unsaturated polyester can be produced by reacting olefinic anhydride, hydroquinone and a catalyst, which can be used to make artificial marble. For the recycling method of waste PET film, please also refer to the recycling method of PET bottles.

Polyester Bonding properties of ester hot melt adhesive

Material bonding strengthMaterial bonding strength

Shear strength/MPa tear strength (N/25mm) Shear strength/MPa tear Strength/(N/25mm)

Cotton (plain weave) 3.07① 2.10①

Polyester 2.93① 112.0 PET film 3.05① Tear

Leather (haired) 2.27② 100 Aluminum foil 12.90④ 126

Tape (for raincoats) 2.83① ---- 8.83①

Canvas (account cover) (used) 7.60 73.0 Aluminum foil 20.13 133

Kraft paper 1.93③ 12.2 Tinplate 11.85 70.3

① Material breakage value, the bonding part is not Cracking ② The skin layer falls off ③ The paper layer is torn apart ④ The test value of using the board as the sample

2. Recycling of bottles

Bottles include soft drink bottles, mineral water bottles, liquid food bottles, cosmetic bottles, etc. The materials used include polyethylene (PE), polyvinyl chloride (PVC), polyvinyl chloride (PVC), and polyvinyl chloride (PVC). Ethylene phthalate (polyester) (PET), etc. Usually mineral water bottles are made of PVC or PET, carbonated drink bottles are made of PET, refreshing beverage bottles, liquid food bottles are made of PVC, PE, detergent bottles, cosmetic bottles , milk bottles, and lactic acid bacteria drinks are mostly made of PE.

The various recycled bottles are generally sorted manually and then recycled according to different materials. At present, there are many technologies and equipment used Recycling of various bottles

Recycling

(1) Recycling of PET bottles. PET bottles are widely used in carbonated drinks such as Coca-Cola, Pepsi-Cola, and Sprite. Currently, most of them are composed of PET bottles and HDPE bottle bottoms. The bottle cap material is HDPE, and the trademark is Biaxially oriented polypropylene (BOPP) film is adhered to the bottle body using EVA adhesive. The ways to reuse polyester bottles after recycling include regeneration, granulation, alcoholysis and other methods. No matter which method is used, first To separate polyester bottles from other bottles, it is also necessary to separate the polyester bottle body and the bottom of the bottle.

① Separation: The mixed addition bottles enter the crusher through the conveyor belt and are crushed, and then separated by density.

② Regeneration and granulation: An extruder can be used for regeneration and granulation. The separated PET scraps are extruded and granulated by the extruder to form pellets. In order to avoid water absorption during extrusion and a decrease in physical viscosity, the It should be dried before extrusion. The uses of PET pellets are as follows:

a. To re-make PET bottles. Recycled pellets cannot be used in direct contact with food, but can be used in the middle layer of three-layer PET bottles. , and then made into carbonated drink bottles.

b. Spinning to make fiber, recycled PET material can be used to spin to make fiber, which can be used as pillow core, mattress, sleeping bag, felt, etc.

c. Glass fiber reinforced material. Glass fiber reinforced recycled PET has good heat resistance and mechanical strength and can be used to make automobile parts, such as heat-resistant automobile wheel covers. Its thermal distortion temperature can reach 240 degrees. .The bending elastic modulus is 9500MPa, the bending strength is 214 MPa, and the impact strength is 15kf/m2.

d. It is fully mixed and modified, and the recycled PET material can be mixed with other polymers to produce Various modified materials can be obtained. If mixed with PE***, a PET*** mixture with improved impact properties can be obtained. PE:PET is (10~50): (90~50): if a small amount of polypropylene is added , the dimensional stability of the blend can be significantly improved. Since the polarities of PE and PET are quite different, compatibilization treatment is required during blending, usually through graft modification of polyolefin. Improve compatibility.

③ Alcoholysis: PET waste is alcoholyzed in the presence of an alkaline catalyst, and then dibasic acid anhydride and other polycondensation are added to obtain a product with an acid value greater than 12. After dilution, filtering, and adding With an appropriate amount of catalyst, alkyd resin paint can be produced. The formula is shown in the table below. The reaction temperature is 80 to 85 degrees, and the reaction is 4 to 5 hours.

PET waste alcoholysis paint formula

Material addition Amount/material addition amount/

PET material 25 N-hydroxymethylacrylamide 2

Triethylene glycol 23 nonionic emulsifier 0.9

Dibutyl phthalate 18 anionic emulsifier 1.1

Vinyl acetate 24 persulfate initiator 1.4~1.6

a-methylbenzene Ethylene 7 Water 130

Methacrylic acid 1

Another example is to react PET waste with polyol at 220~250oc, and then solvate it to obtain a three-dimensional network structure. Insulating paint, the quality meets the requirements of GB6109③ In addition, PET bottles can also be used to make plasticizer: 2-ethylhexyl terephthalate (DOTP), whose plasticizing effect is similar to dioctyl phthalate (DOP) , slightly better than DOP in terms of electrical properties and low-temperature flexibility. Waste PET bottles can also be made into adhesives and unsaturated polyester using methods similar to waste PET films

(2) Collection of PVC bottles , the recycling process of PVC is as follows.

PVC bottles are cleaned, sorted, crushed, finely pulverized and regenerated

First, the PVC bottles are cleaned with steam and alkali solution to remove the trademark, and then mechanically and manually After sorting, the sorted PVC bottles are crushed twice, and finally a powdery regenerated product with a fineness of 500~1200μm is obtained, with a purity of up to 99.98

(3) For the collection of PE bottles, use The PE used as bottle material is mainly HDPE, including dairy product bottles, food bottles, cosmetic bottles, etc. After sorting and cleaning, the HDPE recycled bottles can be crushed and selected for the following uses:

p>① Use a colored Coke bottle base

② Use it to extrude the middle core layer of the pipe

③ Fill it with talcum powder or glass fiber to make floral tea cups or injection molded products.

④ Composite with this fiber and used as artificial wood. Because wood fiber has poor compatibility with HDPE, it is necessary to add appropriate coupling agent or use activated wood fiber.

⑤ To make artificial gravel, HDPE bottles are crushed into fine pieces or granules, and then the gravel shape made of yarn, metal, etc. is adhered to the surface, and then mixed with concrete or asphalt for civil construction materials.

3. Recycling of polystyrene foam

Polystyrene foam can be effectively molded into polystyrene beads. Foam plastics are used for packaging of household appliances or frozen food packaging; there are also A small number of instant noodle bowls are injection molded from expandable polystyrene beads. These plastic products are bulky and require a large amount of tuition and fees, and their recycling has received special attention in China.

Polystyrene foam recycling The main ways are: granulation after volume reduction, crushing and use as various filling materials, cracking to produce oil or recycling styrene and others.

(1) Granulation after volume reduction, polystyrene foam Regenerated pellets can be made by melt extrusion and granulation, but they are bulky and difficult to transport. Usually, the volume needs to be reduced before recycling. Methods include mechanical method, solvent method and heating method.

(2) After crushing, it can be used as filler. After crushing, polystyrene foam plastic products can be used as filler to make various products. For example, ① re-molded into foam plastic products

② concrete composite panel products

③ Gypsum sandwich bricks

④ Used as asphalt enhancer

⑤ Used as soil modifier

(3) Cracking to produce oil or The device for recycling styrene and the method of cracking waste polystyrene foam plastic to produce oil is as follows

Pretreatment of waste polystyrene foam plastic, heat treatment, volume reduction, catalytic cracking, distillation of styrene

( 4) Others, waste polystyrene foam can be used to make coatings and adhesives

① Coating, expandable polystyrene foam can be made into paint by crushing it and adding appropriate solvents, process flow As follows

Fillers, colorants

PS, ethyl acetate, back-grind and over-grind

Ethanol, dibutyl ester, cyclic grinding, filtration, reaction kettle grinding Filter product

Oxygen resin, nitrile rubber kettle

② Adhesive, mixed solvent of esters and benzene, add waste polystyrene foam, anti-sedimentant, and Plasticizers, phenolic resins and other additives can be made into coatings for cement, steel, and wood.

③ Bromination to produce brominated polystyrene flame retardants, using aluminum dichloride as a catalyst Brominated polystyrene is produced by electrophilic substitution reaction between waste polystyrene and bromine. The bromine content can reach 60 to 70. It is used as a flame retardant for thermoplastics such as PET, ABS, and nylon. Brominated polystyrene Ethylene is cheap, has good flame retardant effect and thermal stability. A dosage of 5 parts (mass) can have obvious flame retardant effect. When used together with antimony trioxide, it has a good flame retardant synergistic effect.

4. Recycling of plastic footwear

Plastic footwear includes foamed and non-foamed sandals, as well as various plastic soles. The materials are mainly PVC, PE, PE/EVA, etc. They are being recycled and reused. Before starting the process, we must first sort, usually manually. After sorting, the various waste footwear will be regenerated and utilized according to the type of material.