Company News

Fluorescent Brighteners for Recycled Plastics

2020-06-17

The main raw material of plastic woven bag is PP (polypropylene), and its auxiliary raw materials usually include modifier, lubricant and Fluorescent Brighteners  Generally speaking, polypropylene has abundant sources and low price. Woven bags made of polypropylene are almost the same as woven bags made of high density polyethylene.

The damage rate of plastic woven bags is very high, so a large number of discarded woven bags are discarded every year. However, PP plastic woven bags have extremely high recycling rate. Plastic particles made by recycling extrusion molding can be pulled into woven bags. In order to ensure the quality of unordered parts processed in flexible flat cable, some additives are usually added to improve the appearance quality of products, such as  Fluorescent Brighteners .

Principle of Fluorescent Brighteners in Recycled Woven Bag

 

We can see that the woven bags produced with recycled materials have poor appearance, mainly because the recycled materials contain colored impurities, which can absorb blue or blue-purple visible light with a wavelength of about 450nm.

The reason why the Fluorescent Brighteners can improve the appearance of the recycled material woven bag and whiten and brighten it is because the  Fluorescent Brighteners can absorb ultraviolet light with a wavelength of about 350nm and emit blue or blue-purple visible light with a wavelength of about 450nm after being adsorbed on the recycled material.

The light it emits compensates for the light absorbed by the recycled materials. According to the physical principle, two groups of complementary colors of light are superposed to form white light, so if we look at woven bags made of recycled materials, they will be white and bright.

 

Application method of  Fluorescent Brighteners in recycled material woven bag

 

In the first step, various additives such as recycled materials, fluorescent whitening agents and activated calcium carbonate are poured into a high-speed mixer in sequence according to a certain proportion (the dosage of whitening agent is about 2/5, i.e. 200g of  Fluorescent Brighteners  is added into each ton of materials) to be stirred, melted and plasticized by a barrel and a screw, continuously extruded into strips, cooled and shaped by water, and then fed into a pelletizer to be pelletized.

 

In the second step, the cut particles are put into a wire drawing machine for wire drawing at a temperature of 30 to 40 degrees to ensure the toughness and tensile force of the woven bag, and then the pulled wires are individually fed to a winding machine for wire splitting.

 

 

The third step is flat silk. The flat silk is woven into cloth with circular weaving machine, then coated with film, followed by bag making, which includes printing, cutting, sewing and packaging. The flat silk is further circularly woven. Finally, the circularly woven woven bag is rolled and put into storage. At this moment, we can see that the regenerated woven bag with whitening agent will be white and bright.

 

Although the woven bags made from recycled materials are inferior in physical properties and quality to the woven bags made from new materials, they can also meet the specified standards as long as they are reasonably selected.