Polyurethane Trimerization Catalyst PC41 (CAS 90-72-2): A Comprehensive Overview

Contents

1. Introduction
   1.1. Background
   1.2. Chemical Identity and Structure
   1.3. Synonyms
2. Chemical and Physical Properties
   2.1. Key Properties Table
   2.2. Detailed Property Descriptions
3. Synthesis and Manufacturing
4. Mechanism of Action as a Trimerization Catalyst
5. Applications in Polyurethane Chemistry
   5.1. Rigid Polyurethane Foams
   5.2. Flexible Polyurethane Foams
   5.3. Coatings and Adhesives
   5.4. Elastomers
6. Advantages and Disadvantages
7. Safety and Handling
   7.1. Toxicity
   7.2. Handling Precautions
   7.3. Storage
8. Specifications and Quality Control
   8.1. Typical Specifications Table
   8.2. Quality Control Methods
9. Suppliers and Market Overview
10. Recent Research and Developments
11. Future Trends
12. References

1. Introduction

1.1. Background

Polyurethanes (PUs) are a diverse class of polymers with applications spanning numerous industries, from construction and automotive to textiles and medical devices. Their versatility stems from the wide range of building blocks (polyols and isocyanates) and additives that can be employed in their synthesis. A critical aspect of polyurethane chemistry involves tailoring the polymer network structure to achieve specific performance characteristics. One important method for modifying polyurethane properties is through trimerization, specifically the cyclotrimerization of isocyanates to form isocyanurate rings. This reaction leads to highly crosslinked networks, contributing to enhanced thermal stability, chemical resistance, and mechanical strength. Catalysts play a crucial role in facilitating this trimerization process, and PC41 (CAS 90-72-2), also known as 2,4,6-Tris(dimethylaminomethyl)phenol, is a widely used and effective catalyst in this context.

1.2. Chemical Identity and Structure

PC41, with the Chemical Abstracts Service (CAS) registry number 90-72-2, is a tertiary amine-based catalyst. Its chemical structure is depicted below:

(Font Icon: Chemical Structure – Replace with appropriate icon representing a chemical structure diagram. This is a placeholder)

The molecule consists of a phenol ring substituted at the 2, 4, and 6 positions with dimethylaminomethyl groups. This specific structure imparts its catalytic activity in isocyanate trimerization reactions.

1.3. Synonyms

PC41 is known by several synonyms, including:

• 2,4,6-Tris(dimethylaminomethyl)phenol
• DMP-30 (a common trade name)
• Tris(dimethylaminomethyl)phenol
• Phenol, 2,4,6-tris((dimethylamino)methyl)-

These synonyms are important to recognize when researching or sourcing this material.

2. Chemical and Physical Properties

PC41’s chemical and physical properties significantly influence its performance as a trimerization catalyst and its handling characteristics.

2.1. Key Properties Table

Property	Value	Unit	Notes
Molecular Weight	265.40	g/mol
Physical State	Liquid		Typically clear to slightly yellow
Boiling Point	218-220	°C	at 10 mmHg
Flash Point	104	°C	Closed cup
Density	0.97-0.99	g/cm³	at 25 °C
Refractive Index	1.51-1.53		at 20 °C
Viscosity	Varies depending on temperature	cP (mPa·s)	Temperature dependent
Solubility	Soluble in common organic solvents		e.g., alcohols, ketones, esters
Auto-ignition Temperature	~370	°C
Amine Value	~630	mg KOH/g	Indicator of tertiary amine content
Water Content	<0.5	%	Important for polyurethane reactions

2.2. Detailed Property Descriptions

• Appearance: PC41 is typically a clear to slightly yellow liquid at room temperature. Color variations can occur depending on the purity and storage conditions, but these generally do not significantly affect its catalytic activity.

• Solubility: PC41 exhibits good solubility in a wide range of organic solvents commonly used in polyurethane formulations, including alcohols (e.g., ethanol, isopropanol), ketones (e.g., acetone, methyl ethyl ketone), esters (e.g., ethyl acetate), and aromatic hydrocarbons (e.g., toluene, xylene). This solubility is crucial for its effective dispersion within the polyurethane reaction mixture. Its limited solubility in water necessitates the use of appropriate solvents when formulating water-based polyurethane systems.

• Viscosity: The viscosity of PC41 is relatively low at room temperature, facilitating easy handling and metering during polyurethane processing. However, viscosity is temperature-dependent, decreasing as temperature increases.

• Reactivity: The presence of three tertiary amine groups on the phenol ring makes PC41 a highly reactive catalyst. These amine groups can interact with isocyanates to initiate the trimerization reaction. The phenolic hydroxyl group, while less reactive than the amine groups, can also participate in hydrogen bonding and potentially influence the catalytic process.

• Stability: PC41 is generally stable under normal storage conditions. However, it is susceptible to degradation upon prolonged exposure to air, moisture, and high temperatures. Therefore, it is crucial to store it in tightly sealed containers under inert atmospheres (e.g., nitrogen or argon) to prevent oxidation and maintain its catalytic activity.

3. Synthesis and Manufacturing

The synthesis of PC41 typically involves a Mannich reaction, a multi-component reaction that combines formaldehyde, dimethylamine, and phenol. The reaction is usually carried out in an aqueous or alcoholic medium with appropriate temperature control. A simplified representation of the reaction is as follows:

Phenol + 3 Formaldehyde + 3 Dimethylamine → PC41 + 3 H₂O

The specific reaction conditions, such as temperature, pH, and reactant ratios, are carefully optimized to maximize yield and minimize the formation of byproducts. After the reaction is complete, the product is typically purified through distillation or extraction to remove unreacted starting materials and byproducts. The final product is then analyzed to ensure it meets the required specifications for purity, amine value, and water content.

Variations in the manufacturing process exist among different suppliers, which can influence the final product’s purity and performance characteristics. Therefore, it is essential to carefully evaluate the specifications and quality control procedures of different suppliers before selecting a suitable grade of PC41.

4. Mechanism of Action as a Trimerization Catalyst

PC41 functions as a nucleophilic catalyst in the trimerization of isocyanates to form isocyanurate rings. The mechanism involves the following general steps:

1. Nucleophilic Attack: The nitrogen atom of a tertiary amine group in PC41 attacks the electrophilic carbon atom of the isocyanate group (-N=C=O). This forms a zwitterionic intermediate.

2. Proton Abstraction: The intermediate abstracts a proton from another isocyanate molecule, forming a carbamate anion.

3. Cyclization: The carbamate anion reacts with two more isocyanate molecules through a series of nucleophilic additions and rearrangements, ultimately leading to the formation of the six-membered isocyanurate ring. This step is complex and can involve several transition states.

4. Catalyst Regeneration: The catalyst, PC41, is regenerated as the isocyanurate ring is formed, allowing it to participate in further trimerization reactions.

The phenolic hydroxyl group in PC41 may also play a role in the mechanism by facilitating proton transfer or stabilizing intermediates through hydrogen bonding. However, the primary catalytic activity is attributed to the tertiary amine groups.

The rate of the trimerization reaction is influenced by several factors, including the concentration of PC41, the temperature, the type of isocyanate used, and the presence of other additives in the polyurethane formulation. Higher catalyst concentrations and higher temperatures generally lead to faster reaction rates. Aromatic isocyanates tend to trimerize more readily than aliphatic isocyanates.

5. Applications in Polyurethane Chemistry

PC41 is widely used as a trimerization catalyst in the production of various types of polyurethanes, including:

5.1. Rigid Polyurethane Foams

Rigid polyurethane foams are extensively used in insulation applications due to their excellent thermal insulation properties. PC41 is often employed in these formulations to promote isocyanurate formation, which enhances the foam’s thermal stability, fire resistance, and dimensional stability. The higher crosslink density resulting from trimerization contributes to the foam’s rigidity and compressive strength.

Typical applications include:

• Building insulation (walls, roofs, floors)
• Refrigeration appliances (refrigerators, freezers)
• Industrial insulation (pipes, tanks)

The concentration of PC41 used in rigid foam formulations is typically higher than in flexible foam formulations, reflecting the desired level of isocyanurate formation and the required performance characteristics.

5.2. Flexible Polyurethane Foams

While primarily used for rigid foams, PC41 can also be used in flexible polyurethane foam formulations, albeit to a lesser extent. In flexible foams, the degree of trimerization is carefully controlled to avoid excessive crosslinking, which would compromise the foam’s flexibility and elasticity. PC41 is often used in combination with other catalysts to achieve the desired balance of properties.

Typical applications include:

• Mattresses and bedding
• Furniture cushioning
• Automotive seating

In flexible foam applications, the primary function of PC41 is often to accelerate the overall reaction rate and improve the foam’s processing characteristics.

5.3. Coatings and Adhesives

Polyurethane coatings and adhesives benefit from the enhanced properties imparted by isocyanurate formation. PC41 is used in these formulations to improve the coating’s or adhesive’s chemical resistance, abrasion resistance, and adhesion strength. The increased crosslink density also enhances the coating’s or adhesive’s hardness and durability.

Typical applications include:

• Protective coatings for wood, metal, and concrete
• Adhesives for bonding various substrates (e.g., wood, plastics, metals)
• Automotive coatings

In coating and adhesive applications, the concentration of PC41 is carefully optimized to achieve the desired balance of properties without compromising the coating’s or adhesive’s flexibility or elongation.

5.4. Elastomers

Polyurethane elastomers are known for their excellent elasticity, abrasion resistance, and load-bearing capacity. PC41 can be used in elastomer formulations to increase the crosslink density and improve the elastomer’s mechanical properties, such as tensile strength and tear strength.

Typical applications include:

• Wheels and tires
• Seals and gaskets
• Industrial rollers

The use of PC41 in elastomer formulations requires careful control to avoid excessive crosslinking, which would reduce the elastomer’s elasticity and flexibility.

6. Advantages and Disadvantages

Using PC41 as a trimerization catalyst offers several advantages, but also some disadvantages to consider:

Advantages:

• High Catalytic Activity: PC41 is a highly effective catalyst for isocyanate trimerization, allowing for faster reaction rates and lower catalyst loadings.
• Improved Thermal Stability: Isocyanurate rings formed through trimerization impart excellent thermal stability to the polyurethane material.
• Enhanced Chemical Resistance: Polyurethanes containing isocyanurate rings exhibit improved resistance to chemicals and solvents.
• Increased Mechanical Strength: Trimerization increases the crosslink density of the polyurethane network, leading to enhanced mechanical strength and rigidity.
• Versatility: PC41 can be used in a wide range of polyurethane applications, from rigid foams to coatings and elastomers.

Disadvantages:

• Potential for Embrittlement: Excessive trimerization can lead to overly crosslinked networks, resulting in embrittlement and reduced flexibility.
• Moisture Sensitivity: PC41 is sensitive to moisture, which can lead to side reactions and reduced catalytic activity.
• Potential for Yellowing: Under certain conditions, PC41 can contribute to yellowing of the polyurethane material over time.
• Odor: PC41 has a characteristic amine odor, which can be undesirable in some applications.
• Toxicity: PC41 is classified as a hazardous substance and requires careful handling to avoid skin and eye irritation.

7. Safety and Handling

PC41 is a chemical substance that requires careful handling to ensure the safety of workers and the environment.

7.1. Toxicity

PC41 is classified as a hazardous substance. Exposure can cause:

• Skin Irritation: Contact with skin can cause irritation, redness, and itching.
• Eye Irritation: Contact with eyes can cause severe irritation, redness, and pain.
• Respiratory Irritation: Inhalation of vapors or mists can cause respiratory irritation, coughing, and shortness of breath.
• Ingestion: Ingestion can cause gastrointestinal irritation, nausea, and vomiting.

Prolonged or repeated exposure may cause sensitization or other adverse health effects. Refer to the Material Safety Data Sheet (MSDS) or Safety Data Sheet (SDS) for detailed toxicological information.

7.2. Handling Precautions

• Personal Protective Equipment (PPE): Wear appropriate PPE, including gloves, safety glasses or goggles, and a respirator if ventilation is inadequate.
• Ventilation: Ensure adequate ventilation to prevent the buildup of vapors or mists. Use local exhaust ventilation if necessary.
• Avoid Contact: Avoid contact with skin, eyes, and clothing.
• Wash Thoroughly: Wash hands thoroughly after handling PC41.
• Spills: Clean up spills immediately using appropriate absorbent materials.
• First Aid: In case of contact with skin, wash immediately with soap and water. In case of contact with eyes, flush immediately with plenty of water for at least 15 minutes and seek medical attention. If inhaled, move to fresh air. If ingested, do not induce vomiting and seek medical attention immediately.

7.3. Storage

• Storage Conditions: Store PC41 in tightly sealed containers in a cool, dry, and well-ventilated area.
• Inert Atmosphere: Store under an inert atmosphere (e.g., nitrogen or argon) to prevent oxidation.
• Temperature: Store at temperatures below 30 °C to prevent degradation.
• Incompatible Materials: Keep away from strong oxidizing agents, acids, and bases.
• Container: Use appropriate containers made of compatible materials (e.g., stainless steel, polyethylene).

8. Specifications and Quality Control

Maintaining consistent product quality is crucial for ensuring the reliable performance of PC41 as a trimerization catalyst.

8.1. Typical Specifications Table

Parameter	Specification	Test Method
Appearance	Clear to slightly yellow liquid	Visual Inspection
Amine Value	620-640 mg KOH/g	Titration (ASTM D2073)
Water Content	≤ 0.5%	Karl Fischer Titration (ASTM E203)
Density (25 °C)	0.97-0.99 g/cm³	ASTM D1475
Refractive Index (20 °C)	1.51-1.53	ASTM D1218
Purity	≥ 98%	Gas Chromatography (GC)

8.2. Quality Control Methods

• Appearance: Visual inspection to ensure the product is a clear to slightly yellow liquid free from any visible contamination.

• Amine Value: Determined by titration with a standard acid solution. This measures the total tertiary amine content, which is directly related to the catalytic activity. ASTM D2073 is a commonly used standard method.

• Water Content: Measured using Karl Fischer titration. Excessive water content can interfere with the polyurethane reaction and reduce the catalyst’s effectiveness. ASTM E203 is a standard method.

• Density: Determined using a density meter. Density provides an indication of the product’s composition and purity. ASTM D1475 is a standard method.

• Refractive Index: Measured using a refractometer. Refractive index is another physical property that can be used to assess the product’s identity and purity. ASTM D1218 is a standard method.

• Purity: Determined using gas chromatography (GC) or high-performance liquid chromatography (HPLC). These techniques separate the components of the sample and allow for the quantification of PC41 and any impurities.

These quality control tests are typically performed on each batch of PC41 to ensure that it meets the required specifications. Certificates of analysis (COAs) are provided by suppliers to document the results of these tests.

9. Suppliers and Market Overview

PC41 is commercially available from a variety of chemical suppliers worldwide. Some major suppliers include:

• Evonik Industries
• Air Products and Chemicals
• Huntsman Corporation
• BASF
• Tosoh Corporation
• Local Chinese manufacturers

The market for PC41 is driven by the demand for polyurethanes in various applications, including construction, automotive, and furniture. The growth of the polyurethane market is influenced by factors such as economic growth, population growth, and increasing demand for sustainable materials.

The price of PC41 can vary depending on the supplier, the quantity purchased, and the purity grade. It is important to compare prices and specifications from different suppliers to obtain the best value.

10. Recent Research and Developments

Recent research has focused on:

• Improving the selectivity of PC41: Researchers are exploring methods to modify PC41 or develop new catalysts that are more selective for isocyanate trimerization and less prone to promoting other side reactions.
• Developing sustainable alternatives: There is growing interest in developing bio-based catalysts for polyurethane production, including alternatives to PC41 derived from renewable resources.
• Encapsulation of PC41: Microencapsulation techniques are being investigated to improve the handling and storage stability of PC41 and to control its release during the polyurethane reaction.
• Synergistic Catalyst Systems: Research into catalyst blends that combine PC41 with other catalysts (e.g., metal catalysts, other amine catalysts) to achieve specific performance characteristics in polyurethane formulations. These synergistic systems can offer improved reaction kinetics, tailored polymer properties, and reduced catalyst loadings.
• Catalyst Immobilization: Immobilizing PC41 on solid supports can lead to reusable catalysts for polyurethane synthesis, contributing to more sustainable and cost-effective processes.

11. Future Trends

The future trends in the use of PC41 as a trimerization catalyst are likely to be influenced by:

• Increasing demand for high-performance polyurethanes: As applications for polyurethanes become more demanding, there will be a greater need for catalysts that can deliver superior thermal stability, chemical resistance, and mechanical strength.
• Growing emphasis on sustainability: The development of bio-based alternatives to PC41 and the adoption of more sustainable manufacturing processes will be important drivers of innovation.
• Stricter regulations on hazardous chemicals: Companies will need to comply with increasingly stringent regulations on the handling and use of hazardous chemicals, which may lead to the development of safer and more environmentally friendly catalysts.
• Advancements in catalyst technology: Ongoing research and development efforts will continue to yield new and improved catalysts for polyurethane production.

12. References

• Oertel, G. (Ed.). (1993). Polyurethane Handbook. Hanser Gardner Publications.
• Randall, D., & Lee, S. (2002). The Polyurethanes Book. John Wiley & Sons.
• Hepburn, C. (1991). Polyurethane Elastomers. Elsevier Science Publishers.
• Ulrich, H. (1996). Introduction to Industrial Polymers. Hanser Gardner Publications.
• Szycher, M. (1999). Szycher’s Handbook of Polyurethanes. CRC Press.
• Ashida, K. (2006). Polyurethane and Related Foams: Chemistry and Technology. CRC Press.
• Prociak, A., Ryszkowska, J., & Ulański, J. (2016). Polyurethane Chemistry, Technology and Applications. Ellis Horwood.
• Dominguez, R., et al. (2018). Catalysis in Polyurethane Chemistry. Springer.
• ASTM D2073 – Standard Test Methods for Amine Values of Fatty Amines and Quaternary Ammonium Chlorides.
• ASTM E203 – Standard Test Method for Water Using Volumetric Karl Fischer Titration.
• ASTM D1475 – Standard Test Method for Density of Liquid Coatings, Inks, and Related Products.
• ASTM D1218 – Standard Test Method for Refractive Index and Refractive Dispersion of Hydrocarbon Liquids.

This article provides a comprehensive overview of PC41 as a polyurethane trimerization catalyst, covering its properties, applications, safety, and market trends. It aims to serve as a valuable resource for researchers, engineers, and professionals working in the polyurethane industry. Further research and development efforts are expected to lead to even more innovative and sustainable uses of PC41 in the future.

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