TMO - The best alternative to TPO

The bands of UV LED are concentrated in 365nm, 385nm, 395nm and 405nm, and the absorption of phosphine oxide photoinitiators in these bands is relatively strong, so they are widely used in the application of UV LED.

One of the most representative photoinitiators is TPO, which not only causes high efficiency but also does not yellowing. In 2018-2019, due to the vigorous rise of UV LED curing and China's " Blue-Sky Scheme’, the supply of global TPO was very tight, and the price had been soaring, with the highest unit price exceeding 50USD/KG. The revenue and profits of photoinitiator manufacturers were in record highs because of the skyrocketing price of TPO. In recent years, the continuous expansion of domestic mainstream photoinitiator manufacturers, as well as the entry of new manufacturers, has eased the supply of TPO, even oversupply, and the price has fallen to the level of 12-13USD/KG.

 With the wide application, TPO is facing more and more regulatory supervision.

A 2020 German study on TPO found that histological changes (changes in tissue and cells) in male rat testicles in all test subjects were “massive” and led to a “substantial reduction of fertility.” “Testicular atrophy and reduced number of sperm in the epididymis were observed for all males,” noted the authors. For females, three out of nine rats reported “irregular cycling during the mating period.”

Furthermore, a French study concluded that “a consistent reproductive toxicity was found among studies in male rats, leading to infertility.”

In June 2020, the Nordic country Sweden proposed to amend the classification to 1B(H360DF) and add it as a skin irritant (H317). 1B stands for "Presumed human reproductive toxicant" and is a conclusion based on evidence from numerous animal experiments.

In 2021, the European Union's Risk Assessment Committee (RAC) agreed to update the classification of TPO. The European Commission (EC) is currently reviewing the classification, which takes 0.5-1.5 years according to the stipulated time. In June 2023, ECHA announced the inclusion of TPO as a candidate for SVHC. The ECHA list of SVHC is updated every 6 months. If all member States agree to include TPO in the SVHC list, the work is expected to be completed by January 2024. As a result, TPO is at risk of being completely banned in the EU soon. Relevant TPO users need to plan ahead, adjust the formula, and avoid business loss.

 

Conventional alternatives to TPO

Among phosphine oxide photoinitiators with better absorption in UVA band, in addition to TPO, there are two other commonly used photoinitiators, ECure TPO-L and ECure 819.

ECure TPO-L has a similar structure to TPO, but one of the benzene rings in the molecule is replaced by ethoxy, so it is less toxic. But the initiation efficiency of ECure TPO-L is much lower than that of TPO.

ECure 819 can be seen as a TPO in which a benzene ring is replaced by a 2,4, 6-trimethylbenzoyl group, which has two 2,4, 6-trimethylbenzoyl groups. The initiation efficiency of ECure 819 is higher than that of TPO, but there is a serious yellowing problem, which cannot be used for formulations where the color is required.

In other words, ECure TPO-L and ECure 819 can only replace TPO in some application scenarios, but they cannot completely replace it.

 

TMO - The best alternative to TPO

In this scenario, Phichem successfully developed a new photoinitiator TMO, which fundamentally solved all the problems faced by TPO.

The full name of ECure TMO is (2,4, 6-trimethylbenzoyl) bis (p-Tolyl) phosphine oxide, CAS 270586-78-2. From a structural perspective, TMO introduces a methyl group on each of the two benzene rings on the basis of TPO, which greatly reduces the biological toxicity of TPO. Experiments have found that the initiation efficiency of TMO is even slightly better than that of TPO, while no yellowing and lower migration.

TMO is a perfect alternative to TPO and has already been mass-produced. At the same time, TMO has also obtained the EU REACH registration certificate, which can be sold to the most stringent chemical control in Europe. LIFTCHEM is the authorized distributor of TMO, welcome all of the customers to consult and purchase.