How to deal with the waste plastics of Shandong Jingyuan Plastic Products Co., Ltd.

Hello, I'm glad to answer your question. The treatment method of plastic products is determined according to the type of plastic. Common treatment methods are:

The recycling of waste plastics is beneficial to environmental protection and resource conservation. Thermoplastic waste is very valuable.

Renewable resources can be recycled and granulated, or modified and granulated, and can be used to produce plastic products again.

First, the characteristics of waste plastics

Waste plastics can be divided into three types according to the occasion: one is the corner waste produced in the production process, which

The waste is cleaner, less polluted and contains impurities, such as unqualified film, trimming and flat PP in film production.

Waste silk in silk production, imported parts or unqualified products in pipe and profile production, and underfilled parts in injection molding production.

Wait; One is to use plastic waste from a single material system, such as removing pipes, doors and windows, which is strict.

Classify packaging materials or other waste plastic products according to resin types; There is another kind that is difficult to distinguish or impossible.

Separation and mixing of waste plastics, such as multi-layer coextruded composite films, coated plastic products, and compounding of plastics and other materials.

Synthetic products, etc.

Different kinds of waste plastics have different characteristics. As far as impurity content is concerned, the impurities in the corner waste in factory production are as follows

The content is less than 0. 1%, and the impurity content of leftover materials and other used products piled for a certain time is 0. 1% ~

0.5%, the impurity content of composite waste plastics mixed with aluminum, cloth and paper is often greater than 10%. For used waste plastics,

According to the different use conditions, it will include ultraviolet radiation, the influence of thermal oxidation aging and the influence of pollutants.

The ring. For different shapes of waste plastics, the bulk density of crushed materials varies greatly, such as film, sheet and flat.

The volume density of shredded silk is small, which is a factor that must be considered in the process of granulation and feeding in plastic recycling.

Second, the pretreatment of waste plastics

Waste plastics from waste packaging materials, such as packaging bags, shopping bags, bottles, cans, boxes and waste agricultural films, are used for

Pretreatment is needed before granulation. The pretreatment process mainly includes sorting, cleaning, crushing and drying.

The work of classification is to classify all kinds of waste plastic products according to the types of raw materials and the shapes of products. According to the kinds of raw materials

Classification and sorting require operators to have skilled knowledge of identifying plastic varieties, and the purpose of sorting is to avoid different kinds of plastics.

The recycled materials caused by the mixing of similar polymers are incompatible and have poor properties; Classification by product shape is for the convenience of waste plastics.

The crushing process can be carried out smoothly, because the crushing equipment used for films, flat yarns and their fabrics is similar to some thick-walled and hard products.

Crushing equipment is usually not interchangeable with each other.

For cleaning and crushing before granulation, there are the following three processes.

1. Cleaning before crushing process

Large-scale waste plastic products with less pollution and uncomplicated structure should be cleaned first and then broken, such as cars.

Bumper, dashboard, turnover box, plate etc. Soak the detergent in water first, then rinse it with clear water and take it out.

After air drying. Larger parts that cannot be put into the crusher hopper due to their large size should be coarsely crushed first, and then finely crushed for extrusion.

Feed from granulator. In order to ensure the quality of recycled aggregate, it should be dried after fine crushing, which is often used in conjunction with heating interlayer.

The rotary dryer has high drying efficiency because superheated steam is introduced into the interlayer and rotates while being heated.

2. Rough washing-crushing-fine washing-drying process

For polluted profiles, waste agricultural films and packaging bags, rough washing should be carried out first to remove sand, stone and gold.

It is a foreign object to prevent it from damaging the crusher. After rough washing, the waste plastic products are centrifugally dehydrated and then sent to a crusher for crushing.

It's broken Further cleaning after crushing to remove impurities contained therein. If waste plastics contain oil, they can be properly used.

Soak in a certain concentration of alkaline water or warm washing liquid, and then stir to generate friction between waste plastic blocks (sheets).

Collision, decontamination, dehydration and drying after rinsing.

3. Mechanized cleaning

Figure 4-5 1 is a set of mechanized cleaning equipment with high production efficiency.

Before the waste plastics enter the cleaning equipment, they are crushed in dry or wet crushing equipment and blown away after drying.

People have storage bins, and then the crushed materials are quantitatively input into the cleaning tank by the screw feeder.

Two counter-rotating paddle shafts slowly transport the materials through the cleaning tank, and the generated vortex washes away the dirt on the plastic.

Things. Dirt sinks to clean the bottom of the water tank and is removed from the bottom of the water tank within a specified time interval. After cleaning, the waste floats.

From the screw conveyor. Most of the water was removed. The screw feeder quantitatively feeds the crushed materials into the drying system. male

The drying system consists of rotary dryer and hot air dryer. The residual moisture content of the output material of the drying system accounts for 1% ~ 2%.

The cleaned materials are sent to the storage bin, and then from this storage bin they are sent to the extrusion granulator to produce granular materials.

3. Extrusion granulation technology and equipment for waste plastics

The properties of waste plastics are different from those of new resins because they have gone through the thermal process of molding.

And experienced the influence of heat, oxygen, light, climate and various media in the process of use, so again,

The mechanical properties of green materials, including tensile strength and impact properties, are lower than the original resin, and cracks cause changes in surface structure.

The appearance quality is not as good as before, the color is yellow and the transparency is reduced.

The performance changes of various materials are different. The change of polyolefin materials is relatively small. Due to processing, especially repeated addition

The artificial decrease of relative molecular weight can be compensated by crosslinking reaction, so the processability is improved to some extent.

Stay the same. Figures 4-52 and 4-53 illustrate this effect.

The situation of styrene copolymer is different, and the tensile properties decrease once every processing. draw

As shown in Figure 4-54, after about four processing procedures, the toughness decreases very seriously. In addition, the role of rubber phase impact modifier

Due to crosslinking, the dosage is also reduced. Although it is high impact polystyrene, its impact toughness is not better than that of ordinary polystyrene.

The properties of waste plastics can be improved by mixing new materials or adding specific stabilizers and additives, such as adding anti-aging agents.

Oxygen agent and heat stabilizer can reduce the adverse effects of heat and oxygen in the granulation process of waste plastics. In some mixed

Compatibilizers can also be added to various waste plastics, such as polyethylene and polypropylene mixed waste plastics.

EP D M or ev a can also be filled and modified in plastic recycling granulation, such as adding it to waste PP film at the same time.

10% ~ 35% filler, 3% ~ 6% lubricant and 2% ~ 4% masterbatch. The filler is made of CaC O 3.

The recycled materials used in injection molding products can effectively shorten the molding cycle, improve the rigidity of the products, increase the thermal deformation temperature and reduce the thermal deformation temperature.

Shrinkage is small Lubricant improves the fluidity of melt. Some engineering plastics can also be filled in recycling.

Filling, strengthening and alloying. For some materials that absorb moisture easily, such as PA, PET, etc. In the process of processing, moisture will cause

Degradation reduces the relative molecular weight, melt viscosity and physical properties. Waste plastics should be removed before processing.

Moisture-proof, fully dry, to ensure the quality of recycled materials.

There are many kinds of recycling systems for different types and shapes of waste. As shown in figure 4-55, it is used for pre-.

Extrusion granulation equipment is first used to cut short films, fiber wastes and various broken materials.

Compared with the general extrusion granulation production, the extrusion granulation equipment for recycling waste plastics has the following characteristics.

1. Feeding

The bulk density of the broken waste plastic products is small, especially the broken materials of waste films and fibers. To make sure

This material can be accurately and fully transported to the melting zone and the granulator head, and the design of increasing the size of the feeding section can be adopted.

Form, as shown in figure 4-56. In figure (a), the feeding section of the screw is conical, while the melting and metering section is cylindrical.

The feeding section of (b) is cylindrical with larger diameter, followed by a conical transition section, and the metering section is cylindrical.

When the bulk density of waste plastics is less than 200 g/L, it needs to be forced to feed, and when it is more than 200 g/L, it does not need to be forced to feed.

Settings. Adding the design of feeding section can also fill up the materials that are difficult to transport, such as PP, PA and PET fiber waste.

Land recycling in Italy. For PA and PET, screw heating in the feeding section can be used to improve the conveying efficiency, and PP can also be added.

Slotting the barrel in the material section and fully cooling the hopper seat will greatly improve the feeding and conveying performance. If the added material

It's leftover material of film filament, and the inlet can be opened a little wider to facilitate feeding.

The second step is plastic refining

For the plasticization of waste plastics, it should be considered that the recycled materials are composed of different melt flow rates, different lubricant components,

In fact, different fillers or different types of polymers constitute a mixture, so the plasticization of waste plastics should be sufficient.

It is enough to homogenize various components in the material with uniform quality.

Generally speaking, the single-screw extruder is used when the granulation process of waste plastics is only regenerated without filling or strengthening. if

In the process of granulation, filling, strengthening and alloying are needed, so it is necessary to use twin screws with good mixing effect.

In terms of output, twin-screw extruder is higher than single-screw extruder.

vent

Most polyolefins do not need exhaust regeneration, while hygroscopic polymers such as PA and PET need exhaust. have

Some pollutants that are not cleaned on waste plastics may also be volatile substances, which will produce gas during heating. unleash

The second part should ensure that the molten material has long residence time, high melt temperature, strong shear deformation and large melt surface area.

Product, in order to make the gas in the melt fully discharged.

4. Melt filtration

The function of melt filtration is to filter out impurities in waste plastics. These impurities will greatly reduce the quality of recycled materials.

Put it down. Impurities will cause bubbles to burst during film blowing, filaments to break during spinning, and nozzles to block during injection molding, which will eventually lead to manufacturing.

The product quality drops or all products are unqualified.

The allowable degree of pollution depends on the required level and quality of the final product.

If recycled materials are used to produce films, the impurity particles should be less than 20μm, so that the film with a thickness of 30μm will not break.

Bubble. For injection molding, even if the impurity size is larger than 100μm, it is acceptable. Therefore, the fineness of the filter screen is selected.

Choose must meet the quality requirements or use secondary raw materials.

Too coarse filtration is not good for quality, and too fine filtration affects economic benefits. Fine screen not only has low output, but also changes the screen frequency.

Numerous. Otherwise, productivity will decrease and energy consumption will increase. The time interval for replacing the filter should be greater than 30 minutes. Used for slimming

One layer of coarse mesh and two layers of fine mesh are suitable for granulation of recycled plastics produced by membrane method; Used for injection molding and extrusion of pipes and profiles.

One or two coarse screens should be used. The so-called coarse mesh refers to the mesh spacing of 500μm and the mesh diameter of 0.37 mm

Filter screen; Fine mesh refers to the screen with a screen spacing of 70μm and a screen hole diameter of 0.05mm..

shake the elbows

Because recycled materials are often processed with a certain proportion of new materials, if the particle size difference is too large, the shape

Irregular shape will lead to uneven feeding of new and old materials, and ultimately lead to uneven product performance. Therefore, recycled materials are used.

The shape and size of particles obtained by water-cooling die cutting are the least different from those of new materials, and they are most easily mixed with new materials.

I hope my answer will help you later.