Second-generation new type of photocurable resin "self-curing" (on)

In 2002, a new "family of acrylic resins" was introduced to the photocurable resin that "self-cure" under ultraviolet light irradiation (without or with only a small amount of photoinitiator added).

Recently published papers have discussed new self-initiating resins that can be UV cured without the need or the addition of trace amounts of photoinitiators. These resins are converted to a part of the resin/oligomer structure through the Michael Addition reaction that occurs between normal acrylates and β-diketones, β-ketoesters, and/or β-ketoximes. The molecular characteristic of the new product is a carbonyl group attached to a fully substituted carbon atom. The bond itself is unstable to light, so this type of resin has unique photosensitivity. For example: Michael Addition reaction of acetoacetate and diacrylate on a basic catalyst to form a "functional" photosensitivity oligomer, its structure is as follows:

There have been several "generation" technologies that have used these special functional resins as technical and commercial research for traditional monomer/oligomer replacements. The current established production goal is to achieve application and cure on any substrate (to achieve the necessary performance) without the addition of photoinitiators. This new resin technology is particularly attractive in applications that do not add photoinitiators (eg, food and medical product packaging). This article focuses on the comparison of the benchmark system, the new development of the resin in the application of different substrates and the curing performance of the coating.

The resin chosen for the benchmark was often used as a substitute for similar commercial materials. Those resins that perform well are used frequently in formulations. Table 1 describes the oligomers used and summarizes their minimum viscosity for stickiness and curing to non-stick/scratch-free. Essentially, these are not products, but the starting point for confirming the commercial significance of materials.

Benchmarking of experimental coatings
The most direct way to determine the performance of this new photoinitiated chemical reaction is to detect new materials based on "standard" formulations. The following example is a comparison of different substrates. The purpose of the comparison was to replace the oligomeric resin containing the film forming formulation components with a Michael addition resin, and determine the photoinitiator that was reduced after the replacement.

The second goal is to replace analogous compounds of the oligomers and find the formulations that are as close to the base formulation as possible.

As shown in the example, the cured film was subjected to a 300 W/in or 600 W/in Fusion "H" bulb. All exposures were measured with the IL393 "Light Bug" (International Light), including wavelengths from 250 to 400 nm. Each formula table records the minimum dose of cured "5" (finger dry/no scratch) in the qualitative 1-5 scale. The film was then tested for adhesion, solvent resistance, and brightness or hardness as needed. The Michael addition oligomer formulation and added photoinitiators are listed in the table. The result of the abrasion test is obtained by rubbing the hardened paint film with a cotton swab.

(to be continued)