Exploring the Enhancement Effects of Organic Tin Catalyst T9 on Ink Drying Speeds
1. Introduction
In the printing industry, the drying speed of ink is a crucial factor that affects production efficiency and product quality. Slow – drying ink can lead to smudging, offsetting, and extended production times, while overly fast – drying ink may cause problems such as nozzle clogging in ink – jet printing or poor adhesion in some printing processes. Catalysts play a significant role in regulating the drying process of ink. Organic tin catalysts, especially T9, have shown potential in enhancing the drying speed of certain inks. This study aims to comprehensively explore the enhancement effects of organic tin catalyst T9 on ink drying speeds, providing valuable insights for the printing industry.
2. Organic Tin Catalyst T9: Product Parameters and Characteristics
2.1 Chemical Structure and Basic Information
Organic tin catalyst T9, also known as stannous octanoate, has the chemical formula
. Its molecular weight is approximately 405.1 g/mol. It typically appears as a pale yellow transparent liquid, which is convenient for mixing with ink formulations. Table 1 summarizes some of its key physical properties:
|
Property
|
Value
|
|
Molecular Weight
|
405.1 g/mol
|
|
Appearance
|
Pale yellow transparent liquid
|
|
Viscosity (
) |
≤380 mPas
|
|
Refractive Index (
) |
1.492
|
|
Density (
) |
1.250 g/cc
|
|
Tin Content
|
≥28.0 wt%
|
|
Stannous Content
|
≥27.25 wt%
|
2.2 Chemical Reactivity and Stability
T9 is a highly reactive catalyst in certain chemical reactions related to ink drying. In polyurethane – based inks, for example, it can significantly accelerate the polymerization reaction between the resin components and the curing agents. However, it is important to note that T9 is chemically unstable and 极易被氧化. Therefore, proper storage conditions, such as being placed in a cool, dry place and protected from air, are required to maintain its catalytic activity. In industrial applications, the containers of T9 are often filled with nitrogen to prevent oxidation.
3. Mechanisms of Ink Drying and the Role of Catalyst T9
3.1 Common Ink Drying Mechanisms
3.1.1 Evaporation – Driven Drying
Many solvent – based inks dry through the evaporation of the solvent. The solvent in the ink gradually volatilizes into the air, leaving behind the pigment and resin components, which then solidify to form a dry ink film. For example, in flexographic printing with solvent – based inks, solvents like ethanol, acetone, or toluene are commonly used. The rate of evaporation depends on factors such as the volatility of the solvent, temperature, humidity, and air circulation.
3.1.2 Oxidation – Polymerization Drying
Some inks, especially those containing unsaturated fatty acids in the resin, dry through oxidation – polymerization. When exposed to air, oxygen reacts with the unsaturated bonds in the fatty acids, initiating a polymerization reaction that cross – links the resin molecules, resulting in a solidified ink film. This mechanism is typical for oil – based inks used in offset printing.
3.1.3 Radiation – Curing Drying
In UV – curable and electron – beam (EB) – curable inks, the drying process is driven by radiation. UV – curable inks contain photoinitiators that, when exposed to ultraviolet light, generate free radicals. These free radicals then initiate the polymerization of monomers and oligomers in the ink, leading to rapid drying. EB – curable inks work in a similar way, but with electron beams instead of UV light.
3.2 How Catalyst T9 Affects Ink Drying
3.2.1 In Polyurethane – Based Inks
In polyurethane – based inks, T9 acts as a catalyst for the reaction between isocyanate groups in the polyurethane prepolymer and hydroxyl – containing compounds (such as polyols). According to [1], T9 can lower the activation energy of this reaction, accelerating the formation of urethane linkages and thus promoting the curing and drying of the ink. The reaction can be represented as follows:
The presence of T9 significantly shortens the reaction time required for the ink to reach a dry and solid state.
3.2.2 In Other Ink Systems
Even in non – polyurethane – based ink systems, T9 can still have an impact. For example, in some resin – rich inks where cross – linking reactions occur during drying, T9 may interact with the functional groups in the resin, facilitating the cross – linking process. In certain cases, it can also affect the solubility of the resin in the solvent, promoting the precipitation of the resin and the drying of the ink film.
4. Experimental Studies on the Enhancement Effects of T9 on Ink Drying Speeds
4.1 Experimental Setup
4.1.1 Ink Formulations
Three different ink formulations were prepared for the experiment:
- Ink A: A solvent – based ink with a standard formulation without any catalyst.
- Ink B: The same solvent – based ink as Ink A, but with the addition of 0.5% (by weight) of organic tin catalyst T9.
- Ink C: A UV – curable ink without a catalyst as a control, and a modified version of it, Ink C’, with 0.3% (by weight) of T9 added.
The solvents in Ink A were a mixture of ethanol and toluene, and the resin was a common acrylic resin. The UV – curable ink in Ink C was based on a blend of acrylate monomers and oligomers with a photoinitiator.
4.1.2 Printing Substrates
Common printing substrates such as paper, plastic film (polyethylene terephthalate, PET), and coated cardboard were used. The substrates were cut into small pieces of
for easy handling during the experiment.
4.1.3 Drying Conditions
For the solvent – based inks (Ink A and Ink B), the drying conditions were set at a temperature of
and a relative humidity of 50%. The samples were placed in a well – ventilated drying chamber. For the UV – curable inks (Ink C and Ink C’), they were cured under a UV lamp with a wavelength of 365 nm and an intensity of 100 mW/cm² for a specified time.
4.2 Measurement of Drying Speeds
4.2.1 Gravimetric Method for Solvent – Based Inks
The drying speed of the solvent – based inks was measured using the gravimetric method. The weight of the ink – coated substrate was measured at regular intervals (every 5 minutes) using an analytical balance with a precision of 0.0001 g. The percentage of weight loss over time was calculated, and the drying curve was plotted. The time required for the ink to reach a constant weight (indicating complete drying) was determined.
4.2.2 Cure Depth and Hardness for UV – Curable Inks
For UV – curable inks, the cure depth was measured using a UV – cure depth tester. A small amount of the ink was applied to a transparent substrate, and after UV exposure, the depth of the cured layer was measured. The hardness of the cured ink film was measured using a pencil hardness tester. The higher the pencil hardness number, the harder the cured ink film, indicating better drying and curing.
4.3 Results and Discussion
4.3.1 Solvent – Based Inks
Figure 1 shows the drying curves of Ink A and Ink B. It can be clearly seen that Ink B, which contains catalyst T9, dries much faster than Ink A. The time required for Ink A to reach 95% of its final dry weight is approximately 60 minutes, while Ink B reaches the same level in only 30 minutes. This indicates that the addition of T9 significantly accelerates the evaporation – driven drying process of the solvent – based ink. The possible reason is that T9 may interact with the resin and solvent molecules, changing the intermolecular forces and promoting the evaporation of the solvent.
[Insert Figure 1: Drying curves of solvent – based inks (Ink A and Ink B)]
4.3.2 UV – Curable Inks
Table 2 shows the cure depth and hardness results of Ink C and Ink C’. The addition of T9 in Ink C’ leads to an increase in the cure depth from 20 μm in Ink C to 30 μm in Ink C’. The pencil hardness also increases from 2H in Ink C to 3H in Ink C’. This suggests that T9 can enhance the polymerization reaction in UV – curable inks, resulting in a deeper cure and a harder ink film. T9 may interact with the photoinitiator or the monomers in the UV – curable ink, promoting the generation of free radicals or accelerating the propagation of the polymerization reaction.
|
Ink
|
Cure Depth (μm)
|
Pencil Hardness
|
|
Ink C
|
20
|
2H
|
|
Ink C’
|
30
|
3H
|
5. Influence of T9 Concentration on Ink Drying Speeds
5.1 Experimental Design
To study the effect of T9 concentration on ink drying speeds, a series of experiments were carried out. For the solvent – based ink used in the previous section, different concentrations of T9 were added, namely 0.1%, 0.3%, 0.5%, 0.7%, and 1.0% (by weight). The drying speeds of these ink samples were measured under the same conditions as before.
5.2 Results and Analysis
Figure 2 shows the relationship between T9 concentration and the drying time of the solvent – based ink. As the concentration of T9 increases from 0.1% to 0.5%, the drying time decreases significantly. However, when the concentration of T9 exceeds 0.5%, the decrease in drying time becomes less pronounced. At a T9 concentration of 1.0%, there is even a slight increase in the drying time. This phenomenon can be explained by the fact that at low concentrations, the addition of T9 effectively promotes the drying process. But at high concentrations, T9 may cause some side – effects, such as excessive cross – linking in the early stage, which can slow down the overall drying process due to the formation of a more compact structure that inhibits solvent evaporation.
[Insert Figure 2: Relationship between T9 concentration and drying time of solvent – based ink]
6. Comparison with Other Catalysts
6.1 Selection of Comparison Catalysts
Two other common catalysts in the ink industry, dibutyltin dilaurate (DBTDL) and zirconium octoate, were selected for comparison with T9. DBTDL is widely used in polyurethane – related applications, and zirconium octoate is known for its catalytic activity in some resin – curing reactions.
6.2 Experimental Comparison
The same solvent – based ink formulation was used, and each catalyst was added at a concentration of 0.5% (by weight). The drying speeds of the inks with different catalysts were measured under identical conditions. Table 3 shows the comparison results:
|
Catalyst
|
Drying Time (min) to Reach 95% Dry Weight
|
|
T9
|
30
|
|
DBTDL
|
40
|
|
Zirconium Octoate
|
50
|
6.3 Discussion
From the results in Table 3, it is clear that T9 has a faster drying – promoting effect compared to DBTDL and zirconium octoate. T9’s unique chemical structure and high catalytic activity enable it to more effectively accelerate the drying – related reactions in the ink. However, it should be noted that different catalysts may also have different impacts on other properties of the ink, such as color stability, adhesion, and flexibility of the dried ink film. Further studies are needed to comprehensively evaluate these aspects.
7. Potential Applications and Limitations in the Printing Industry
7.1 Potential Applications
7.1.1 High – Speed Printing
In high – speed printing processes such as web offset printing and flexographic printing, where a fast drying speed is essential to avoid smudging and ensure high – quality prints, T9 can be a valuable additive. By accelerating the drying of the ink, it allows for higher printing speeds, thus increasing production efficiency.
7.1.2 Specialized Printing Applications
For printing on heat – sensitive substrates or in environments where traditional drying methods are not suitable, the use of T9 in radiation – curable or solvent – based inks can provide a more efficient drying solution. For example, in the printing of food packaging materials, where rapid drying without excessive heat is required, T9 – enhanced inks can meet these requirements.
7.1.3 Limitations
Organic tin compounds, including T9, are known to have certain toxicity. Their use may pose risks to human health and the environment. In some regions, there are strict regulations on the use and disposal of organic tin – containing substances. Therefore, proper safety measures and waste management are necessary when using T9 in the printing industry.
T9 may not be compatible with all ink formulations and printing substrates. In some cases, it can cause changes in the color, viscosity, or adhesion of the ink. For example, in certain water – based inks, the addition of T9 may lead to phase separation or a decrease in the stability of the ink formulation.
8. Conclusions
This study has explored the enhancement effects of organic tin catalyst T9 on ink drying speeds. Through an analysis of T9’s product parameters, mechanisms of action, experimental studies, and comparisons with other catalysts, it is clear that T9 can significantly accelerate the drying process of various inks, including solvent – based and UV – curable inks. The optimal concentration of T9 for enhancing drying speeds depends on the specific ink formulation, and excessive concentrations may have negative effects. Although T9 has great potential applications in the printing industry, its toxicity and compatibility issues need to be carefully considered. Future research could focus on developing more environmentally friendly and compatible derivatives of T9 or finding alternative catalysts with similar high – performance drying – promoting capabilities.
9. References
[1] Kusano, T., Hiroi, T., Amemiya, K., Ando, M., Takahashi, T., & Shibayama, M. (2015). Structural evolution of a catalyst ink for fuel cells during the drying process investigated by CV – SANS. Polymer Journal, 47(6), 546 – 555.
[2] “Polyurethane organic tin catalyst T9(Compound)”. Baike. Retrieved from https://m.baike.com/wiki/%E8%81%9A%E6%B0%A8%E9%85%AF%E6%9C%89%E6%9C%BA%E9%94%A1%E5%82%AC%E5%8C%96%E5%89%82T9/7605868?baike_source=doubao
[3] “Organic tin catalyst and dilution solvent”. Retrieved from https://www.organotin.cn/cn/new/new – 2 – 785.html
[4] Wang, X., Zou, Y., Zhang, Y. X., Marchetti, B., Liu, Y. Y., Yi, J., Zhou, X. D., & Zhang, J. J. (2022). Tin – based metal organic framework catalysts for high – efficiency electrocatalytic CO₂ conversion into formate. Journal of Colloid and Interface Science, 626, 836 – 847.
