Bottles include refreshing beverage bottles, mineral water bottles, liquid food bottles, cosmetic bottles, etc. The materials used are polyethylene (PE), polyvinyl chloride (PVC), polyethylene terephthalate (polyester) ( PET) etc. Usually mineral water bottles are made of PVC or PET, carbonated beverage 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 beverages are mostly made of PE.
The recycled bottles are generally sorted manually first, and then recycled according to different materials. At present, there are many technologies and equipment used in the recycling of various bottles.
(1) Recycling of PET bottles. PET bottles are widely used in Coca-Cola, Pepsi, Sprite and other carbonated beverages. At present, 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). The film is adhered to the bottle body with an EVA adhesive, and the way to reuse the polyester bottle after recycling is regeneration granulation. Alcoholysis and other methods. Regardless of the method used, the polyester bottle must first be separated from other bottles, and the polyester bottle body must be separated from the bottle bottom.
① Separation: The mixed collection bottle enters the pulverizer through the conveyor belt to be crushed, and then is separated by density.
② Regeneration granulation: Extruder can be used for regeneration granulation. The separated PET scraps are extruded and pelletized by an extruder to make pellets. In order to avoid water absorption during extrusion, the physical properties and viscosity should be reduced, and it should be dried before extrusion. The uses of PET pellets are as follows:
a. Re-manufacture 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 to make carbonated beverage bottles.
b. Spinning to make fibers. Recycled PET materials can be used to spin into fibers for pillow cores, mattresses, sleeping bags, felts, etc.
c. Glass fiber reinforced material. Recycled PET reinforced by glass fiber has good heat resistance and mechanical strength. It can be used to make auto parts, such as heat-resistant car wheel covers, and its thermal distortion temperature can reach 240 degrees. The flexural modulus of elasticity is 9500MPa, the bending strength is 214 MPa, and the impact strength is 15kf/m2.
d. Blending modification. Recycled PET materials can be blended with other polymers to obtain various modified materials. For example, blending with PE can obtain PET blends with improved impact performance. 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. Because the polarity of PE and PET is quite different, it is necessary to carry out compatibility treatment during blending, and the compatibility is generally improved by graft modification of polyolefin.
③Alcoholysis, PET waste is alcoholyzed in the presence of an alkaline catalyst, and then polycondensation such as dibasic acid anhydride is added to obtain a product with an acid value greater than 12, which is diluted, filtered, and an appropriate amount of catalyst is added to obtain alkyd resin paint. The formula is shown in the table below. Reaction temperature 80~85 degrees, reaction 4~5h
(2) The additional collection of PVC bottles and the recycling process of PVC are as follows. PVC bottles are cleaned, sorted, crushed, and finely crushed. The recycled products are first cleaned with steam and lye to remove the trademark, and then mechanically and manually sorted. The sorted PVC bottles are crushed for the second time, and the final fineness is 500. ~1200μm powdered regenerated product, the purity can reach 99.98%
(3) The additional collection of PE bottles. The PE used as bottle material is mainly HDPE, including milk product bottles, food bottles, cosmetic bottles, etc. After sorting, the cleaned HDPE bottles can be crushed and selected. The uses are as follows :
① Use the colored cola bottle base
② Used for pipe coextrusion middle core layer
③ Filled with talcum powder or glass fiber to make tea cups or injection molded products
④ It is combined 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, crush HDPE bottles into fine flakes or granules, then glue yarn, metal and other gravel on the surface, and then mix it with concrete or asphalt for use in civil construction materials.
Useful polystyrene beads can be molded. Foam plastic used for packaging of household appliances or frozen food; there are also a few instant noodle bowls made of expandable polystyrene beads. These plastic products are bulky and large in tuition and fees, and their recycling is particularly valued in China. The main ways to recycle polystyrene foam are: granulation after volume reduction, use as various filling materials after pulverization, cracking to make oil, or recovery of styrene and others.
(1) After volume reduction, it can be pelletized. Polystyrene foam can be melt-extruded and pelletized to make recycled pellets. However, it is bulky and transports feces, so volume reduction is usually required for recycling. Methods include mechanical method, solvent method and heating method.
(2) After being crushed, it is used as a filler, and polystyrene foam products can be used as a filler after being crushed to make various products. Such as ① remolding into foamed plastic products ② concrete composite board products ③ gypsum sandwich brick ④ used as asphalt intensifier ⑤ used as soil modifier
(3) Pyrolysis for oil production or recovery of styrene, waste polystyrene foamed plastic cracking for oil production equipment is as follows: Waste polystyrene foam pretreatment heat treatment, volume reduction, catalytic cracking rectified styrene (4) Others, waste polystyrene Vinyl foam can be used to make paints and adhesives. ① Paint, expandable polystyrene foam is crushed and added with appropriate solvent to make paint. The process flow is as follows: filler, colorant PS, ethyl acetate Over-production of ethanol, dibutyl ester, ring should grind filter reaction kettle to grind filter product oxygen resin, nitrile rubber kettle ② Adhesive, ester and benzene mixed solvent, add waste polystyrene foam, anti-precipitation agent, Plasticizers, phenolic resins and other additives can be made into coatings for cement, steel, and woodware. ③ Brominated to prepare brominated polystyrene flame retardant, using aluminum dichloride as a catalyst to make the waste polystyrene and bromine undergo an electrophilic substitution reaction to prepare brominated polystyrene, the bromine content can reach 60% to 70 %, used as a flame retardant for thermoplastics such as PET, ABS, and nylon. Brominated polystyrene is inexpensive, has good flame retardant effect and thermal stability, and the amount of 5 parts (mass) can have obvious flame retardant effect. Used together with antimony trioxide, it has a good flame-retardant synergistic effect.
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