Introduction of additives for biodegradable plastic products (4)

Reactive functional polymer chain extender
Because PLA, polyhydroxyfatty acid ester (PHA), poly (butylene adipate/butylene terephthalate) (PBAT), polyethylene terephthalate (PET), polybutylene terephthalate (PBT) and other biodegradable polymers contain rich carboxyl, hydroxyl and other reactive functional groups, Therefore, thermal degradation will inevitably occur in processing and application, which will lead to the reduction of melt strength and mechanical properties of products.
Therefore, the development and application of reactive functional polymer chain extender is an important way to improve the processing performance of biodegradable polycondensation polymers. At present, the research hotspots of reactive functional polymer chain extender at home and abroad are mainly concentrated in the following aspects:
(1) epoxy functional chain extender
Epoxy functional chain extender contains a certain amount of epoxy functional groups, with high activity, and can react with the end hydroxyl group, end carboxyl group, end amino group, etc. in the processing of polycondensation polymers, which can not only improve the molar mass of the resin, but also make the broken chain rejoin, improve the melt viscosity, and improve the performance of the product.
The German company BASF completed the acquisition of Johnson Polymers in 2006 and launched the Joncryl chain extender series. Clariant, in collaboration with Johnson Polymer, introduced the CESA-extend series of chain extenders at the end of 2005 SPE Global Plastics Environment Conference (GPEC) to address the issue of feed port accumulation caused by the low glass transition temperature of such chain extenders.
Shanxi Institute of Chemical Engineering completed the pilot project of KL-E series of epoxy functional polymer chain extender in 2012. The success of the research and development of the project has greatly promoted and promoted the technological development of China's biodegradable plastics industry and recycled plastics industry.
(2) oxazoline chain extender
Haplotype oxazoline is a molecule that contains two oxazoline groups. The representative variety is the 1, 3-PBO dioxazoline compound. The main domestic production enterprises are Wuhan Hezhong Biochemical Manufacturing Co., LTD and Zhonghao (Dalian) Chemical Research and Design Institute Co., LTD., while the main foreign production enterprises are Evonik AG, Adeka Palmarole and Takemoto Oil&Fat Co., LTD.
Polymerized oxazoline refers to the introduction of a certain amount of oxazoline groups into the polymer molecular chain by physical and chemical methods. The United States DOW company as early as the 1980s successfully launched the polystyrene containing oxazoline group (RPS), and then, under the license of Dow Chemical Company, the Japanese catalyst launched the industrial product EPOCROS RPS 1005.
(3) isocyanate chain extender
Isocyanate chain extenders are mainly divided into polymerization type and haplotype. Isocyanates can easily react with active hydrogen on the chain of biodegradable polymers, resulting in chain extension or cross-linking effect. The commonly used chain extender is diphenylmethane diisocyanate (MDI). MDI is one of the important raw materials in polyurethane industry, and can also be used as chain extender for polyester biodegradable plastics. The main manufacturers of MDI are BASF, Bayer, Huntsmann-ICI, DOW, Mitsui Takeda and Yantai Wanhua.
(4) anti-hydrolysis stabilizer
Polycondensation biodegradable plastics (such as PLA, PHA, PBAT, PET, PBT, etc.) are easy to hydrolyze, and the addition of anti-hydrolysis stabilizer is a common method. The antihydrolysis stabilizer can react with the terminal carboxyl group, terminal amine group and terminal hydroxyl group produced during the hydrolysis of the polymer to produce stable and harmless products, effectively preventing further degradation and chain breaking. There are many kinds of substances that can be used as hydrolysis stabilizers, such as haomorphic (polymeric) carbonized diimines, isocyanates, oxazolines, epoxides, and other substances that can terminate hydrolysis. At present, the research at home and abroad mainly focuses on the following aspects:
(5) carbonized diimide type anti-hydrolysis stabilizer
Carbonized diimide is a compound containing a functional group - N=C=N - in the molecule, which can generally be divided into haomorphic carbonized diimide and polymerized carbonized diimide. Haplotype carbonized diimide has the advantages of high activity and quick effect, while polymerized carbonized diimide has good compatibility with plastics and can play a long-term stable effect. At present, the main varieties on the market are Rhine Staboxol-1 and Staboxol-P. The success of the 100t annual production of hydrolysis stabilizer BIO SW-100 pilot project of Shanxi Institute of Chemical Engineering marks a great breakthrough in the industrialization of polyester hydrolysis stabilizer in China, and the anti-hydrolysis stabilizer BIO SW-500 developed by the institute is also under development and will be available soon.
(7) isocyanate, epoxy, oxazoline and acid anhydride
Isocyanate compounds can easily react with the active hydrogen on the molecular chain of biodegradable polymers, play an end-sealing role, and inhibit the catalytic hydrolysis of the active hydrogen on the polymer. Epoxides, oxazolines, and anhydrides can also react with the carboxyl and hydroxyl end of the polymer chain, thereby improving the hydrolysis resistance of the polymer. In addition to the end-sealing effect, some of these compounds can also produce chain extension, branching and cross-linking effects on the polymer molecular chain, and appropriate addition can improve the strength of the polymer melt, thereby improving the processing and mechanical properties of the polymer.
The advantages of anti-hydrolysis stabilizer are high efficiency and small addition amount, which can be widely used in polyester biodegradable plastics. However, it should be noted that the thermal stability of the anti-hydrolysis stabilizer in the polymer processing process, as well as the processing hygiene and safety.