Amalchem shares photoinitiator selection to advance the UVcuring industry in an uncertain world

According to Amalchem: A number of photoinitiators and associated amine synergists (co-initiators) have recentlycome under close regulatory scrutiny, principally in Europe, under the oversight of ECHA andthe member states of the EU. Here are the principal actors involved. They are not "rogues" inthe conventional sense, but have been shown to have toxicological properties in non-human lifeforms that cause one or more regulatory authorities to classify and, ofen, restrict their use. Thislist will almost certainly only continue to grow.

TPO(CAS# 75980-60-8)

TPO has been self-reclassified by the Lead Registrant under REACh, following extensiveadditional toxicological testing. Harmonized reclassification to 1B Reprotoxin wvill be a decisionfor the Swedish Authority when they undertake the dossier evaluation in 2021 (this was going tobe during 2020, but was put back a year). It is likely to eventually become an $VHC (n.b. this isspeculation, not fact!), but the classification is not the only consideration. The uses andeffectiveness of RIMlM (rapid microbiological methods) are taken into consideration and. ifshowwn to be controlled and effective, could avoid regulatory action for some time as other. morenazardous,substances are targeted.

Omnirad 369 (2-dimethylamino-2-benzy1-1-(4-morpholin-4-yl-phenyl)-butan-1- one CAS #119313-12-1) and Omnirad 907 (2-Methyl-1-[4-(methylthio) phenyl]-2-morpholinopropan-1-one CAS # 71868-10-5)

These have recently (January 16t, 2020) been added to the Candidates List for SVHCs(substances f Very High Concern) by ECHA on account of their reprotoxicity. Restrictionand /or Authorization, with the Austrian authority leading, are likely to follow. The SVHCclassification applies only in Europe, although it is expected, as with all reclassified or restricted substances, that other regulatory authorities will follow suit. With regard to specific marketsectors where one or other of these photoinitiators are used, currently the case would be thatoutside the EU it would strongly depend on customer or end use policies.

Given the current reclassifications and expected trajectory of regulatory investigation intoother chemicals, including photoinitiators, consider how innovating in photoinitiators canallow the industry to stay ethically at least one step ahead of the regulatory authorities and their influencers.

Alternates to TPO

The industry has been quick to evaluate alternates to TPO. Principal substitutes areOmnirad 819 (BAPO)- which can be used at approximately 50% the concentration of TPOand TPO-L - which can be used at approximately 14096 ofthe concentration of TPO, both on awv basis. Omnipol TP(C4S #1834525-17-5) offers a futher alternative, with the advantagesof very high solubility and low migration potential. It can be used at approximately the samew' concentration as TPO. APO blended with difunctional alpha hydroxy ketones like EsacureONE, Omnirad 127 or Esacure KIP 160 also offer possibilities, especially for LED cure, as doesAPOs blended with Esacure 1001M.

Alternates to Omnirad 369 and 907

Alternates to Omnirad 369, like difunctional alpha hydroxy ketones (e.g. Esacure KIP160, Omnirad 127. Esacure ONE) and acyl phosphine oxides, as well as blends comprising oneor both of these groupings, were discussed at RadTech 2016' None is a “drop in" based eitheron absorption wavelength or cost Omnirad 379(2-dimethvlamino-2-(4-methvl-benivl)-1-(4-morpholin-4-pl-phenvl)butan-1-one C4S # 119344-86-4) is, of course, the closest match to Omnirad 369, but its future is thought uncertain by some. It is a workhorse for ink jet.where one photoinitiator to cover all end uses from signage throught food packaging is desirable.

Omnirad 389 (2-Benxv-2-dimethvlamino-1-(4-piperidinvlphenvl)-1-butanone CAS #119312-76-4), another alpha amino ketone, is available as an alternate to Omnirad 907.especially for the Asian electronics industry.

For sensitive packaging applications, polymeric alpha amino ketones, such as Omnipol910 (Polyethylene glvcol dibeta-4-[4-(2-dimethvlamino-2benzv)butanovlphenvljpiperazine)propionate CAS # 886463-10-1) are available.PolymericPIs display very low migration tendencies, but are not usable in all formulatory applications, onaccount of their impact on formulation rheology

Silvlated Alpha Hvdroxy Ketones

This is a new class of photoinitiators, stil at the laboratory level, based on silylated alphahydroxy ketones. Certain materials in this class show properties very close to alpha aminoketones, unlike their parent alpha hydroxy ketones".

Two evident trends within the printing and coating market sectors are the conversionfrom medium-pressure mercury lamps to uv-LEDs (principally 38/395 nm, but also 365nm) andthe continued growth of specialty and sensitive packaging systems. So, it is appropriate to look at the new photoiitiator classes being developed, patented and commercialized to see howv thelwill assist in safeguarding and growing the uv curing industry.

A few of the challenges facing photoinitiators, both from a compliancestandpoint and a performance one as both the regulatory authorities expand their oversight of ourindustry, how we may compensate for photoinitiators receiving Reprotoxin 1B and/or SVHCclassifications, and how increased performance is required- and will be met through ongoinginnovation at the molecular and formulation levels - for the firther growth of the technology. Insummary, in 2025 (or 2030?), we might expect to see the resolution of some ofthe existingchallenges, the resolution of some and the incursion of new ones, as we continue to develop andoptimize photoinitiator performance in an uncertain world.