As a resource, waste bottle chips have been widely used in spinning, packing and blowing PET bottles, and the amount is increasing. We know that no matter what kind of products are made, in addition to the strict requirements for the characteristic viscosity, melting point and carboxyl end group of polyester, there are also strict requirements for the impurity content (PVC content, ash content, impurity and moisture) of polyester, so the cleaning of waste bottle pieces has become the content that many factories gradually pay attention to.

The quality of bottle pieces washed out by the factory is uneven. Is it just a question of whether the production equipment is advanced or not? Let's basically analyze:

1. Plastic bottle recycling process

First of all, the beverage factory or water plant, through the links of consumers, scavengers, waste recycling stations and cleaning plants, gradually processed into bottles that can be made into various products. In this process, the turnover cycle of bottles also has a certain impact on the later quality of bottles. The fast turnover bottles, such as caramel, label gum and fructose, do not attach strongly, especially oil Pot, the oil pot with a short recovery cycle is easier to clean than that of the cycle plant, which is one reason why downstream chemical fiber plants or other factories using bottle chips quote higher prices for bottle chips in first tier cities than those in other cities.

2. Bottle attachment

In addition to the caramel, label gum, fructose, etc. necessary for the production of beverages, the impurities contained in the waste bottles may also have vegetable oil, animal oil, dust, soil, pigment, pigment, etc. attached to the beverage bottles. Among them, caramel, fructose, floating oil, dust, soil, etc. belong to non structural dirt, while label glue, old grease, pigment, etc. belong to structural dirt.

In alkaline environment, nonstructural dirt can be removed by general surfactants. However, at a certain temperature, waste bottle pieces are easy to saponify with alkali liquor, forming macromolecular branched chains, affecting the spinnability and fiber feel.

3. Cleaning of attachments

It is difficult to remove structural dirt only by general cleaning agent in alkaline environment. In order to remove structural dirt from the waste bottle, it is necessary to have a surface carrier penetrating agent, so that the surface agent can penetrate into the substrate of the waste bottle in alkaline environment, so that the structural dirt can be removed.

That's why some big cleaning factories or chemical fiber factories use caustic soda and cleaning powder, not the same.

However, excessive caustic soda will produce saponification reaction on the surface of pet (the reaction is not obvious in cold state, and the reaction speed increases with the rise of temperature above 70 ℃), resulting in saponification, which will affect the flexibility and spinnability of pet macromolecules.

In order to achieve the ideal cleaning effect, the usual method is: reduce the amount of caustic soda properly, through the heating method, make the cleaning agent get enough to remove oil, make the label adhesive in a loose state.

4. Action principle of cleaning agent

The excellent cleaning agent can clean the dirt through hkqxo carrier resin to remove all kinds of dirt such as oil dirt and inorganic matters attached to the surface of the waste bottle piece. At the same time, it can infiltrate the agent under the carrier resin and disperse the dirt into the water in small groups on the surface, so that the cleaning solution is easy to sink and filter.

Note: because the cleaning agent needs to play its role in alkaline environment, and the strong alkali is conducive to the removal of label adhesive, but the strong alkali will cause damage to pet, it is necessary to introduce strong alkali inhibitor into the cleaning agent to reduce the damage to the polyester surface and strengthen the alkali when cleaning the waste bottle pieces.

Suggestion: because the glass transition temperature of pet is 270 ℃, and above the glass transition temperature of pet, dyes are very easy to be embedded between PET molecular chains, resulting in the yellowing of waste bottle pieces. To ensure that the bottle pieces do not turn yellow, it is an ideal method to clean the waste bottle pieces with detergent in the alkaline environment in the cold state. When the soaking time reaches, the structural dirt on the surface of the waste bottle pieces will Loose, cleaning agent in the hot state of the waste bottle hot cleaning, you can easily clean the non structural dirt and structural dirt. Moreover, the waste bottle pieces are not easy to be dyed and discolored.

Summary

1. In order to make the water-based detergent achieve the ideal effect of removing oil stain, disintegrating label adhesive and other structural dirt, it is necessary to ensure the three basic elements of cleaning temperature and cleaning time above the critical concentration (the cleaner manufacturer will give some guidance), so as to remove the dirt on the waste bottle.

2. When using cleaning agent, it should be equipped with pet corrosion inhibitor in alkaline environment, strong carrier penetrating agent (included in some cleaning agent formulas).

Note: Although the dirt is peeled off from the substrate of the waste bottle sheet, it does not mean that the waste bottle sheet has been cleaned, because the cleaned dirt has a certain settling speed in the water, and the dirt is easy to attach to the waste bottle sheet twice, forming van der Waals force with the sheet base, which is more difficult to rinse off. It is necessary to add a dirt suspending agent into the cleaning agent to reduce the settling speed of the dirt in the cleaning and rinsing process, so as to reduce the secondary adhesion.