Golden Hair Technology Wins Two Invention Patents, Solving The Problems Of Edge Sealing Strength And Casting Precipitation In Biodegradable Films

Background technology

Biodegradable materials are mainly used for film preparation, typically through the casting process to make biodegradable materials into films. The casting process is an efficient production method that produces unstretched, unoriented flat extruded films by rapidly cooling the melt. This process is characterized by high production speed and output, and it achieves excellent film transparency, glossiness, and thickness uniformity, making it suitable for large-scale production of biodegradable material films.

Among them, biodegradable materials based on polylactic acid (PLA) have a problem: due to the characteristics of PLA itself, during the casting process at high temperatures (200-220°C) and certain pressures (extrusion pressure 3-5 MPa), PLA tends to precipitate oligomers that accumulate on the casting rollers. The accumulation of these precipitates on the rollers not only affects the quality of subsequent products but also requires regular cleaning of the casting rollers, increasing production costs.

The precipitation of polylactic acid in the casting process is difficult to completely avoid, but reducing the precipitation of degradation products during the casting process can greatly enhance the processing stability of the material and the quality of the product, improve terminal production efficiency, reduce production losses, and bring significant economic benefits.

The primary objective of this invention is to overcome the severe issue of precipitate formation in the casting process of biodegradable materials with polylactic acid as the main resin in current technology, and to provide a biodegradable composition with low precipitate formation during casting.

The low migration biodegradable composition includes the following components in parts by weight: 69-91 parts polylactic acid, 0-16 parts flexible biodegradable polyester, 0-11 parts filler, 0.1-3.1 parts anti-migration agent, and 0.1-3.1 parts phosphite antioxidant.

The anti-precipitation agent is a phosphorus compound with a structure shown in formula I or formula II.

Studies have found that during the casting process, under high temperatures (200-220°C) and certain pressure conditions (3-5 MPa), polylactic acid easily generates free radicals, which can lead to the degradation of polylactic acid into oligomers, resulting in precipitation. The invention incorporates phosphite antioxidants, which can react to some extent with the free radicals generated by polylactic acid during the casting process, thereby reducing its decomposition rate and improving the precipitation issue during the casting process of biodegradable compositions to a certain extent. However, the improvement in the precipitation issue of biodegradable compositions by adding only phosphite antioxidants is limited.

Further research has found that the issue of film casting precipitation in biodegradable compositions can be significantly improved by adding specific anti-precipitation agents. The reason is that polylactic acid or other biodegradable polyesters in biodegradable compositions contain trace amounts of tin and/or titanium elements, which not only catalyze the synthesis of polylactic acid or other polyesters but also have a certain catalytic degradation effect on polylactic acid under the high temperature and high pressure of the film casting process. The addition of specific anti-precipitation agents can chelate the metal ions of these metal catalysts, preventing the catalytic degradation of polylactic acid by metal catalysts. The anti-precipitation agents work synergistically with phosphite antioxidants, thereby significantly improving the issue of film casting precipitation in biodegradable compositions.