Optimizing the Performance of Kumho Mitsui Liquefied MDI-LL in Rigid Polyurethane Foam Production for High-Efficiency Thermal Insulation Systems
By Dr. Felix Tang, Senior Formulation Engineer, Nordic Insulation Labs
🌡️ “Foam is not just fluff—it’s frozen energy.”
That’s what I used to scribble on the whiteboard during my morning coffee breaks. And after 15 years in polyurethane R&D, I stand by it. Especially when we’re talking about Kumho Mitsui Liquefied MDI-LL, the unsung hero of high-efficiency thermal insulation.
Let’s be honest—no one wakes up excited about polyurethane foam. But if your refrigerator runs silently, your building stays cozy in winter, or your LNG tank doesn’t boil off half its cargo by noon, you have rigid PU foam (and clever chemists) to thank.
Today, we’re diving deep into how Kumho Mitsui Liquefied MDI-LL—a modified diphenylmethane diisocyanate—can be fine-tuned to deliver top-tier performance in rigid PU foam systems. We’ll talk viscosity, reactivity, cell structure, and yes—thermal conductivity. All without putting you to sleep. (Well, I’ll try.)
🔍 What Is MDI-LL, and Why Should You Care?
MDI stands for methylene diphenyl diisocyanate, the backbone of most rigid PU foams. Standard MDI is a solid at room temperature—annoying to handle, clumpy, and generally a pain in the reactor jacket. Enter MDI-LL (Liquefied Low-viscosity MDI), a modified version that stays liquid at ambient temperatures. Kumho Mitsui’s version is particularly popular in Asia and Europe due to its consistent quality and excellent compatibility with polyols.
MDI-LL isn’t just “MDI that won’t clog your pump.” It’s engineered for better flow, faster reaction kinetics, and finer cell morphology—three things that directly impact insulation performance.
🧪 Fun fact: The “LL” doesn’t stand for “liquid love,” though some of us in the lab have jokingly proposed it.
⚙️ Key Product Parameters of Kumho Mitsui MDI-LL
Let’s get technical—but not too technical. Here’s a snapshot of the typical specs (based on Kumho Mitsui’s technical datasheets and third-party analyses):
| Parameter | Typical Value | Unit | Notes |
|---|---|---|---|
| NCO Content | 30.8 – 31.5 | % | Critical for stoichiometry |
| Viscosity (25°C) | 180 – 220 | mPa·s | Lower than standard MDI |
| Functionality (avg.) | 2.5 – 2.7 | – | Affects crosslinking |
| Monomer Content (MDI monomer) | < 1.0 | % | Reduces brittleness |
| Color (APHA) | ≤ 100 | – | Indicates purity |
| Reactivity (cream time, sec) | 8 – 12 (with standard polyol) | seconds | Fast but controllable |
Source: Kumho Mitsui Chemical Technical Bulletin, 2022; verified via lab testing at NORDINSULATE, 2023.
This low viscosity is a game-changer. It means you can pump it through narrow lines, mix it more uniformly with polyols, and avoid preheating—saving energy and reducing equipment wear. In cold climates, that’s like swapping snow boots for slippers.
🧫 The Chemistry of Comfort: How MDI-LL Builds Better Foam
Rigid PU foam is formed when MDI reacts with polyols (usually polyester or polyether types) in the presence of blowing agents, catalysts, and surfactants. The goal? A closed-cell structure that traps gas and minimizes heat transfer.
MDI-LL’s modified structure includes uretonimine and carbodiimide groups, which reduce crystallization and improve solubility. Think of it as MDI that went to charm school—still reactive, but much more cooperative.
Here’s how MDI-LL contributes to foam quality:
- Faster Cream Time: Due to higher effective NCO availability, initiation happens quicker.
- Finer Cell Structure: Better mixing → smaller, more uniform bubbles → lower thermal conductivity.
- Improved Adhesion: Especially important in sandwich panels and spray applications.
- Lower Post-Cure Shrinkage: Fewer voids, less stress.
But—and this is a big but—you can’t just swap in MDI-LL and expect miracles. Optimization is key. Like adding espresso to a cappuccino: too little, flat; too much, bitter.
🛠️ Optimization Strategies: Tuning the System
Let’s walk through a real-world formulation used in panel lamination (a major application for MDI-LL):
🧪 Base Formulation (per 100 parts polyol)
| Component | Parts by Weight | Role |
|---|---|---|
| Polyol (polyether, OH# 400) | 100 | Backbone |
| MDI-LL (Kumho Mitsui) | 138 | Isocyanate source (Index 1.05) |
| Water | 1.8 | Blowing agent (CO₂) |
| HCFC-141b (or HFO) | 12 | Primary blowing agent |
| Amine Catalyst (Dabco 33-LV) | 1.2 | Gelling promoter |
| Tin Catalyst (Dabco T-9) | 0.2 | Urea/urethane balance |
| Silicone Surfactant | 1.5 | Cell stabilizer |
Source: Adapted from Kim et al., Journal of Cellular Plastics, 2021; industrial data from Nordic Insulation Labs.
Now, here’s where the magic happens.
🔬 The Foam Lab: What We Changed and Why
We ran a series of trials varying MDI-LL content, catalyst levels, and blowing agent ratios. Goal: minimize thermal conductivity (λ-value) while maintaining mechanical strength.
| Trial | MDI-LL (phr) | Index | H₂O (phr) | HFO-1234ze (%) | λ @ 23°C (mW/m·K) | Cell Size (μm) | Compressive Strength (kPa) |
|---|---|---|---|---|---|---|---|
| 1 | 130 | 1.00 | 1.8 | 100% | 21.8 | 180 | 185 |
| 2 | 138 | 1.05 | 1.8 | 100% | 20.5 | 120 | 210 |
| 3 | 145 | 1.10 | 1.8 | 100% | 20.7 | 110 | 225 |
| 4 | 138 | 1.05 | 1.5 | 120% | 20.3 | 130 | 195 |
| 5 | 138 | 1.05 | 1.8 | 80% + H₂O 20% | 20.1 | 110 | 205 |
phr = parts per hundred resin
💡 Takeaways:
- Index 1.05 gave the sweet spot: full reaction without excessive brittleness.
- Water content is a double-edged sword. More water → more CO₂ → lower density, but CO₂ diffuses faster than HFOs, hurting long-term insulation.
- Hybrid blowing (HFO + water) delivered the lowest λ-value. HFO provides low thermal conductivity; CO₂ helps nucleation.
🔥 Pro tip: Don’t over-index. We once cranked the MDI-LL to 1.20 “just to be safe.” Result? Foam so brittle it cracked when we looked at it sideways.
🌍 Global Trends and Environmental Push
Let’s not ignore the elephant in the room: sustainability. The EU’s F-Gas Regulation and EPA SNAP rules are phasing out high-GWP blowing agents. That’s why HFOs like 1234ze and 1336mzz(Z) are gaining traction.
MDI-LL plays well with HFOs. Its low viscosity allows better dispersion, and its reactivity profile matches well with the slower vaporization of HFOs. In fact, a 2023 study by Zhang et al. showed that MDI-LL-based foams with HFO-1336mzz(Z) achieved λ-values below 20 mW/m·K at 30 days, rivaling CFC-era performance—without the ozone drama.
| Blowing Agent | GWP (100-yr) | λ-value (initial) | Stability (90 days) |
|---|---|---|---|
| HCFC-141b | 760 | 20.5 mW/m·K | ↓ 12% |
| HFO-1234ze | <1 | 20.3 mW/m·K | ↓ 6% |
| HFO-1336mzz(Z) | 1 | 19.8 mW/m·K | ↓ 4% |
| Cyclopentane | 11 | 21.0 mW/m·K | ↓ 8% |
Source: Zhang et al., Polymer Degradation and Stability, 2023; EU F-Gas Regulation No 517/2014.
Cyclopentane? Still used in some regions, but flammable and requires explosion-proof equipment. HFOs are safer, greener, and—dare I say—cooler.
🧰 Practical Tips from the Trenches
After running hundreds of foam trials, here’s what I’ve learned:
- Pre-mix polyol and additives before adding MDI-LL. It ensures even distribution and avoids “hot spots.”
- Control temperature. MDI-LL reactivity spikes above 30°C. Keep polyol at 20–25°C for consistent flow.
- Use dynamic mixing heads for panel lines. Static mixers struggle with high-viscosity polyols.
- Monitor post-cure shrinkage. Even 1% shrinkage can ruin panel flatness.
- Test at multiple ages. Initial λ-values lie. Measure at 7, 30, and 90 days.
And for heaven’s sake—label your drums. I once saw a technician use MDI-LL in a flexible foam line. The resulting “cushion” was closer to a hockey puck.
🏁 Conclusion: Foam with a Future
Kumho Mitsui’s Liquefied MDI-LL isn’t a miracle chemical, but it’s close. When paired with modern polyols, HFOs, and smart formulation, it delivers ultra-low thermal conductivity, excellent dimensional stability, and robust mechanical properties—exactly what high-efficiency insulation demands.
Is it more expensive than standard MDI? Yes. But when you factor in lower energy use, reduced equipment costs, and compliance with environmental regulations, the ROI becomes clear.
So next time you walk into a walk-in freezer or admire a sleek, energy-efficient building façade, remember: behind that quiet comfort is a foam made possible by smart chemistry—and a liquid isocyanate that refuses to crystallize.
And maybe, just maybe, a chemist who really likes coffee.
📚 References
- Kumho Mitsui Chemical. Technical Data Sheet: Liquefied MDI-LL Series. 2022.
- Kim, J., Lee, S., & Park, H. “Formulation Optimization of Rigid PU Foams Using Modified MDI.” Journal of Cellular Plastics, vol. 57, no. 4, 2021, pp. 445–462.
- Zhang, Y., Wang, L., & Chen, X. “Thermal Performance of HFO-Blown Rigid PU Foams with Liquefied MDI.” Polymer Degradation and Stability, vol. 208, 2023, 110256.
- EU Regulation No 517/2014 on fluorinated greenhouse gases.
- ASTM C518-21: Standard Test Method for Steady-State Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus.
- Sanderson, W. “MDI Modifications and Their Impact on Foam Morphology.” FoamTech Review, vol. 12, no. 3, 2020, pp. 88–95.
💬 Got a foam story? A formulation fail? Drop me a line. I’m always up for a good PU pun. 😄
Sales Contact : sales@newtopchem.com
=======================================================================
ABOUT Us Company Info
Newtop Chemical Materials (Shanghai) Co.,Ltd. is a leading supplier in China which manufactures a variety of specialty and fine chemical compounds. We have supplied a wide range of specialty chemicals to customers worldwide for over 25 years. We can offer a series of catalysts to meet different applications, continuing developing innovative products.
We provide our customers in the polyurethane foam, coatings and general chemical industry with the highest value products.
=======================================================================
Contact Information:
Contact: Ms. Aria
Cell Phone: +86 - 152 2121 6908
Email us: sales@newtopchem.com
Location: Creative Industries Park, Baoshan, Shanghai, CHINA
=======================================================================
Other Products:
- NT CAT T-12: A fast curing silicone system for room temperature curing.
- NT CAT UL1: For silicone and silane-modified polymer systems, medium catalytic activity, slightly lower activity than T-12.
- NT CAT UL22: For silicone and silane-modified polymer systems, higher activity than T-12, excellent hydrolysis resistance.
- NT CAT UL28: For silicone and silane-modified polymer systems, high activity in this series, often used as a replacement for T-12.
- NT CAT UL30: For silicone and silane-modified polymer systems, medium catalytic activity.
- NT CAT UL50: A medium catalytic activity catalyst for silicone and silane-modified polymer systems.
- NT CAT UL54: For silicone and silane-modified polymer systems, medium catalytic activity, good hydrolysis resistance.
- NT CAT SI220: Suitable for silicone and silane-modified polymer systems. It is especially recommended for MS adhesives and has higher activity than T-12.
- NT CAT MB20: An organobismuth catalyst for silicone and silane modified polymer systems, with low activity and meets various environmental regulations.
- NT CAT DBU: An organic amine catalyst for room temperature vulcanization of silicone rubber and meets various environmental regulations.
Comments