This monomer can solve your new challenges in UV inkjet, coating and 3D printing

Compiler: Du Peng, Runao Chemical

Original author: Nikolas Kaprinidis, Simon Werrel, Elmar Kessenich and Giovanni D'Andola, BASF

Keywords: VMOX, low viscosity, low odor, compliance inkjet 3D printing 

Summary

The use of oxazolidinone-based reactive diluents solves the challenges faced by UV/EB curing applications, such as compliance with toxicological compliance pressure, and improving the performance of UV curing formulations.

Introduction

Vinyl methyl oxazolidinone (VMOX) is a newly launched vinyl monomer.

discuss

Generally speaking, vinyl ether and/or amide monomers, together with other standard monomers in the industry (such as acrylates), together with acrylate oligomers, epoxy resins and unsaturated polyester resins, are initiated by light The copolymerization reaction has been widely used in free radical and cationic UV curing systems.

In recent years, existing products such as N-vinylpyrrolidone (NVP) and N-vinylcaprolactam (NVC) have performed well at the technical level and can meet many needs, but they have been subject to regulatory review issues.

For example, the European Printing Ink Association (EuPIA) has banned the use of mutagenic or carcinogenic products, such as NVP, in all printed formula products, and it is expected that NVC will be banned soon.

Table 1.

VMOX is liquid at room temperature (melting point is 20°C), so melting equipment is no longer needed, thereby reducing cost, processing time and operational complexity.

In addition, VMOX's low viscosity (4mPa·s) makes it have obvious diluting ability, so it can realize the requirement of significantly lowering the viscosity of UV ink (viscosity is less than 10mPa·s), so as to obtain high-performance ink products.

Figure 1.

Figure 1 compares the effects of several reactive diluents on the viscosity of typical inkjet inks, coatings and 3D printing formulations.

Due to its high affinity for traditional acrylate monomers, VMOX has high copolymerization reactivity with all current most commonly used acrylate monomers (such as DPGDA, IBOA, TBCH, POEA, CTFA, etc.
) and N-vinyl lactam It also has high affinity with the traditional acrylate oligomers used in the industry.
In Table 2, the reactivity of VMOX is compared with NVC, NVP and ACMO.

The reactivity is measured based on a standard method, that is, the ink formula is cured on a conveyor belt under LED or mercury lamp at a speed of 15 m/min.
Then compare the curing speed of different monomers based on the number of times the formula can be fully cured on the conveyor belt.
The performance of VMOX is similar to several other test materials (rating of 3).

Table 2.
Reactivity comparison of inkjet formulations: 34% reactive diluent, 60% other monomers and 6% other ingredients (including photoinitiator).
Irradiation and curing with 395nm wavelength and 550mW/cm² power

Adhesion to all common substrates is another key technical performance index for reactive diluents and UV formulations in printing applications.
VMOX can make inks or coatings have excellent adhesion, which may be due to its own high polarity, which can improve adhesion through erosion and swelling.

As shown in Table 3, the adhesion of the formulations containing VMOX, NVC and NVP was compared by a standard peel adhesion test method.
0 is the best and 5 is the worst.
Each sample was subjected to 5 peel tests.
Compared with NVC and NVP, the formulation ink based on VMOX shows similar adhesion, even when the concentration is lower.
The results are listed in Table 3.

Table 3.
Comparison of adhesion of various polymer substrates: 34% reactive diluent, 60% other monomers and 6% other ingredients (including photoinitiators).
After curing for three days, perform manual scratching and tape test: 0 means complete adhesion; 5 means complete peeling

In these applications mentioned, yellowing, color, and strange smells have always been a challenge.
The formulations using NVP or NVC are prone to yellowing due to auto-oxidation and decomposition.
As a result, it is often necessary to use various amines to stabilize NVP or NVC monomers.
This method can slow down the yellowing speed, but it cannot completely eliminate it.

As listed in Table 4, although pure VMOX exhibits the highest APHA color value among the listed monomers, the cured color of the coating is comparable to NVP, NVC and ACMO (see the clear varnish in the second row formula).

In addition, VMOX exhibited a better color response, as indicated by the CIELAB color space measured on a white plastic substrate.
Formulas containing VMOX can produce brighter whites (L*) and more neutral color channels (a*, b*).

Table 4.
Color comparison of sample formulations containing different reactive diluents: 50% reactive diluent, 42% other monomers, and 8% other ingredients (including photoinitiator)

Another unique feature of this monomer is its extremely low odor.
VMOX-based formulations have almost no odor even after printing.
This expands the scope of application of the monomer beyond UV inkjet.
The testing of VMOX proved its successful application in UV coatings (as reactive diluent and monomer), UV adhesives (as reactive diluent and auxiliary), and 3D printing (as photosensitive monomer).

VMOX has registered with EU REACH.
It has also recently been included in the Toxic Substances Control Act (TSCA) list, which can be used for UV printing inks and 3D printing.

Unlike some commonly used reactive diluents (such as NVC, NVP and ACMO), according to the classification of the European Chemicals Agency (ECHA), VMOX is not required to bear the warning labels of "serious health hazard" and "acute toxicity".
Before VMOX, to use materials that were not required to affix such labels, formulation engineers had a very limited range of options, and in fact there was no technically equivalent alternative.

Figure 2 summarizes the comparison of the Global Harmonized Classification and Labeling System (GHS) of the above monomers.
Registrations in countries such as Switzerland and the Philippines have been issued, while registrations in China and Japan are in progress.

Figure 2.
The molecular structure of VMOX and the GHS logo compared with other monomers

in conclusion

VMOX is the latest addition to BASF's vinyl monomer product portfolio.
It provides solutions to help meet technical and regulatory challenges in UV printing ink and coating applications.

In addition, it has been proved that VMOX has excellent diluting ability and can effectively reduce the viscosity to below 10 mPa·s.
It is liquid at room temperature, ensuring easy handling and preventing the formula from yellowing or producing strange odors.

VMOX also provides good toxicological properties, expands the toolbox of formulation engineers who need a unique combination of technical performance, and improves operational and regulatory compliance.