1. The background of the popularity of biodegradable plastics

Plastics are accumulated after they are discarded in the natural environment. Combustion will become a cause of global warming. Biodegradable plastics that have been gradually decomposed by the action of microorganisms into the natural circulation system after being discarded have attracted attention in recent years and have entered the popularization stage. Among them, biodegradable plastics made from plant materials are very attractive as alternatives to limited chemical resources. .

2. The mechanism of biodegradation

The gravure ink used in printing has a variety of uses. Its basic composition includes three parts: colorant (pigment), binder (resin, solvent) and additive. In such a composition, an ink using a biodegradable resin is defined as a biodegradable gravure ink. That is, in addition to biodegradable resins, non-biodegradable materials are used in the ink. The mechanism of biodegradation is decomposed by the fermentation of microorganisms. The biodegradable polymer (matrix) is not a microorganism that can be decomposed, but it requires specific microorganisms to complete it. Prints made with non-biodegradable gravure inks cannot be found to lose weight even when placed in environmental conditions that are degraded, and cannot be naturally decomposed when placed in a fermentation apparatus under natural conditions.

Pigments used as colorants consist of particles smaller than one micron, but are completely non-biodegradable materials. It has been determined that this raw material tends to hinder the biodegradation of the ink resin. The ink layer after printing is an ink film composed of a dry resin with a pigment as the core, which will hinder the action of microorganisms of several micrometers in size. It can be inferred that this is due to pigments. With antibacterial effect. A Japanese company used a home-use fermentation equipment to perform a biodegradable gravure ink degradation test. The test environment consisted of a soil moisture content of 50%, a temperature of 40±3°C, an ink layer thickness of 10 μm (dry state), and a base film of 50 μm polyester. Films, pigments use titanium oxide pigments (weight ratio of resin to pigment 1:3).

Source: 21st Century Fine Chemicals Network