Jiangsu Tetra New Material Technology Co., Ltd.
Jiangsu Tetra New Material Technology Co., Ltd.

A New Option for Cycloaliphatic Epoxy Resin in UV-LED Cationic Inkjet Printing?

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    Research Background


    Ink is one of the largest pollutants in the printing industry with a large amount of VOCs endangering the atmospheric environment. Therefore, green printing technology and eco-friendly ink are imperative.UV-LED inkjet, as one type of eco-friendly ink, can be divided into free radical systems and cationic systems. Compared to the former, the cationic system has advantages such as oxygen inhibition resistance, low shrinkage, dark cure, and is more suitable for UV-LED inkjet. Currently, in the cationic system,cycloaliphatic epoxy resins are primarily TTA21, with a viscosity above 200mPa·s (25℃), requiring a large amount of reactive diluting monomers during use to meet the inkjet viscosity requirement of<30mPa·s, resulting in thecycloaliphatic epoxy resins not fully exerting their properties, leading to unsatisfactory curing speed, adhesion, solvent resistance, and heat resistance for inkjet. To meet the application needs for UV-LED cationic inkjet, Tetra, one of the leading cycloaliphatic epoxy resin manufacturers, developed a series of cycloaliphatic epoxy resins with lower viscosity and faster curing speed compared to TTA21.



    TTA20

    TTA22

    TTA28

    TTA800

    Viscosity

    mPa·s(25℃)

    4-20

    5-30

    10-30

    50-70

    Epoxy Equivalent

    80-100

    70-80

    70-100

    100-110

    Features

    Bio-based

    Ultra low viscosity

    Low viscosity

    Fast curing

    Low viscosity

    Fast curing, highTg

    Ultra-fast curing,

    HighTg, high hardness, low viscosity

    Structural Formula

    cycloaliphatic-epoxy-resin-20240528-1.jpg

    cycloaliphatic-epoxy-resin-20240528-2.jpg

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    Materials and Methods


    Taking TTA28 as an example, its performance in UV-LED cationic inkjet applications is examined, including formula viscosity, storage stability, curing speed, adhesion (304  stainless steel), solvent resistance, and heat resistance.


    Formula composition: (TTA21/28+TTA201+TTA101): pigment paste: initiator: photosensitizer: additive=100:15:4:1:2


    Results


    cycloaliphatic-epoxy-resin-20240528-3.jpg

    Figure 1: amount and formula of oxetane


    cycloaliphatic-epoxy-resin-20240528-4.jpg

    Figure 2: Storage Stability


    cycloaliphatic-epoxy-resin-20240528-5.jpg

    Figure 3: Curing Speed (395nm LED Light Source)


    Experiment No.Ratio of Cycloaliphatic Epoxy Resin to OxetaneAdhesion Grade (0: Best, 5: Worst)
    24h7 Days
    Control Sample (a)TTA21/TTA201/TTA101=40/50/1055
    Control Sample1(b)TTA28/TTA201/TTA101=80/10/1000
    Control Sample2(c)TTA28/TTA201/TTA101=70/20/1000
    Control Sample3(d)TTA28/TTA201/TTA101=60/30/1015
    Control Sample4(e)TTA28/TTA201/TTA101=40/50/1055
    Control Sample5(f)TTA28/TTA201/TTA101=20/70/1055


    Table 4: Cross-Cut Adhesion Test Grades


    Conditions: 304 stainless steel substrate, 10μm film thickness, 395nm LED light exposure (5000mJ/cm²), tested according to GB/T 9279-2007.


    cycloaliphatic-epoxy-resin-20240528-6.jpg

    Figure 5: Cross-Cut Adhesion Analysis (7 Days)


    cycloaliphatic-epoxy-resin-20240528-7.jpg

    Figure 6: Tg (DMA Thin Film Tensile Method)


    Experiment No.Solvents
    EthanolMEK
    Control Sample>100 wipes50 wipes
    Test Sample 2>100 wipes50 wipes

    Table 7: Solvent Wipe Resistance


    Conditions: 304 stainless steel substrate, 10μm film thickness, 395nm LED light exposure (5000mJ/cm²), tested according to GB/T 23989-2009 (1kg load, 60rpm).


    Conclusion


    TTA28, as an ultra-low viscosity cycloaliphatic epoxy resin, serves both as a film-forming resin and a diluent in UV-LED cationic inkjet printing. This specialty resin chemical features fast curing speed, excellent adhesion, good solvent resistance, high-temperature resistance, and good storage stability. Additionally, TTA20, TTA22, and TTA800 also exhibit similar properties, making them valuable for cationic inkjet printing applications.

    References