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Bis[2-(N,N-Dimethylaminoethyl)] Ether: A Catalyst for Accelerated Curing in Industrial Coatings

Abstract:

Bis[2-(N,N-Dimethylaminoethyl)] ether (BDMAEE), also known as Jeffcat ZF-20 or Dabco BL-19, is a tertiary amine catalyst widely employed in the formulation of polyurethane, epoxy, and other thermosetting industrial coatings. Its primary function is to accelerate the curing process, leading to enhanced productivity, improved coating properties, and reduced energy consumption. This article delves into the chemical properties, mechanism of action, applications, advantages, disadvantages, safety considerations, and future trends of BDMAEE in the context of industrial coatings, highlighting its critical role in modern coating technology.

Table of Contents:

1. Introduction
2. Chemical Properties
   • 2.1 Chemical Formula and Structure
   • 2.2 Physical Properties
   • 2.3 Reactivity
3. Mechanism of Action in Coating Systems
   • 3.1 Polyurethane Coatings
   • 3.2 Epoxy Coatings
   • 3.3 Other Thermosetting Coatings
4. Applications in Industrial Coatings
   • 4.1 Automotive Coatings
   • 4.2 Coil Coatings
   • 4.3 Wood Coatings
   • 4.4 Marine Coatings
   • 4.5 Protective Coatings
5. Advantages of Using BDMAEE
   • 5.1 Accelerated Curing Time
   • 5.2 Improved Throughput
   • 5.3 Enhanced Coating Properties
   • 5.4 Lower Energy Consumption
6. Disadvantages and Limitations
   • 6.1 Volatility and Odor
   • 6.2 Potential for Yellowing
   • 6.3 Compatibility Issues
   • 6.4 Over-Catalyzation
7. Safety Considerations
   • 7.1 Toxicity
   • 7.2 Handling and Storage
   • 7.3 Environmental Impact
8. Formulation Considerations
   • 8.1 Dosage
   • 8.2 Compatibility with other Additives
   • 8.3 Influence of Temperature and Humidity
9. Alternative Catalysts
   • 9.1 Other Tertiary Amines
   • 9.2 Metal Catalysts
   • 9.3 Amine Blocking Agents
10. Future Trends and Developments
11. Conclusion
12. References

1. Introduction

Industrial coatings play a crucial role in protecting and enhancing the performance of a wide range of materials, from automobiles and buildings to appliances and machinery. The curing process, during which the liquid coating transforms into a solid film, is a critical step in achieving the desired protective and aesthetic properties. The duration of this curing process significantly impacts production efficiency and overall cost-effectiveness. Catalysts are often employed to accelerate the curing reaction, thereby reducing processing time and improving throughput. Bis[2-(N,N-Dimethylaminoethyl)] ether (BDMAEE) has emerged as a prominent catalyst in various industrial coating formulations due to its effectiveness in promoting rapid curing, particularly in polyurethane and epoxy systems. This article provides a comprehensive overview of BDMAEE, exploring its chemical properties, mechanism of action, applications, advantages, disadvantages, safety considerations, and future trends in the industrial coatings sector.

2. Chemical Properties

2.1 Chemical Formula and Structure

BDMAEE is an organic compound belonging to the class of tertiary amines. Its chemical formula is C₁₀H₂₄N₂O, and its structural formula can be represented as:

(CH₃)₂N-CH₂-CH₂-O-CH₂-CH₂-N(CH₃)₂

The molecule contains two dimethylaminoethyl groups linked by an ether linkage. This structure contributes to its strong catalytic activity, particularly in reactions involving isocyanates and epoxides.

2.2 Physical Properties

The physical properties of BDMAEE are summarized in the following table:

2.3 Reactivity

BDMAEE is a highly reactive tertiary amine. The nitrogen atoms in the molecule possess lone pairs of electrons, making it a strong nucleophile and a good base. This reactivity enables it to catalyze various chemical reactions, including:

• Polyurethane formation: BDMAEE accelerates the reaction between isocyanates and alcohols (polyols) to form polyurethanes.
• Epoxy curing: BDMAEE can catalyze the ring-opening polymerization of epoxy resins with curing agents (hardeners) like amines or anhydrides.
• Other reactions: BDMAEE can also catalyze other reactions, such as transesterification and Michael addition.

3. Mechanism of Action in Coating Systems

The catalytic activity of BDMAEE in coating systems stems from its ability to facilitate the reactions between the key components, leading to the formation of the crosslinked polymer network that constitutes the cured coating.

3.1 Polyurethane Coatings

In polyurethane coatings, BDMAEE primarily acts as a catalyst for two crucial reactions:

1. The reaction between isocyanate and polyol: BDMAEE promotes the nucleophilic attack of the hydroxyl group of the polyol on the electrophilic carbon atom of the isocyanate group, forming a urethane linkage. The proposed mechanism involves the amine nitrogen coordinating with the hydroxyl group, increasing its nucleophilicity.

2. The isocyanate trimerization reaction: BDMAEE can also catalyze the trimerization of isocyanates, leading to the formation of isocyanurate rings. These rings contribute to the crosslink density and thermal stability of the polyurethane coating.

The relative rates of these two reactions are influenced by the concentration of BDMAEE, the reaction temperature, and the specific isocyanate and polyol being used. Optimizing these parameters is crucial for achieving the desired coating properties.

3.2 Epoxy Coatings

In epoxy coatings, BDMAEE functions as an accelerator for the reaction between the epoxy resin and the curing agent (hardener), typically an amine or an anhydride.

1. Amine-cured epoxy systems: BDMAEE enhances the nucleophilic attack of the amine curing agent on the epoxy ring, leading to ring-opening polymerization and crosslinking. The amine group of the curing agent abstracts a proton from the BDMAEE, creating a more reactive nucleophile.

2. Anhydride-cured epoxy systems: While less common, BDMAEE can also promote the reaction between epoxy resins and anhydrides. In this case, BDMAEE facilitates the ring-opening of the anhydride by the hydroxyl groups generated during the epoxy-anhydride reaction.

The choice of curing agent and the concentration of BDMAEE are critical factors in determining the curing rate and final properties of the epoxy coating.

3.3 Other Thermosetting Coatings

BDMAEE can also be used as a catalyst in other thermosetting coating systems, such as those based on acrylic resins, alkyd resins, and unsaturated polyesters. Its catalytic activity in these systems depends on the specific chemistry involved and the presence of reactive functional groups that can interact with the amine nitrogen of BDMAEE.

4. Applications in Industrial Coatings

BDMAEE finds widespread application in various industrial coating sectors due to its effectiveness in accelerating curing and improving coating performance.

4.1 Automotive Coatings

In automotive coatings, BDMAEE is used in both primer and topcoat formulations, particularly in polyurethane-based systems. It helps to reduce the curing time of the coatings, allowing for faster production cycles in automotive assembly plants. The use of BDMAEE also contributes to improved coating hardness, scratch resistance, and gloss.

4.2 Coil Coatings

Coil coatings are applied to continuous metal strips that are subsequently formed into various products, such as appliance panels, roofing sheets, and automotive parts. BDMAEE is used in coil coating formulations to ensure rapid curing during the high-speed coating process. The accelerated curing enables high production rates and minimizes the risk of coating defects.

4.3 Wood Coatings

Wood coatings are used to protect and enhance the aesthetic appeal of wood furniture, flooring, and other wood products. BDMAEE is employed in polyurethane wood coatings to shorten the curing time and improve the coating’s resistance to abrasion, chemicals, and moisture.

4.4 Marine Coatings

Marine coatings are designed to protect ships, offshore platforms, and other marine structures from corrosion and fouling. BDMAEE is used in marine coatings based on epoxy and polyurethane resins to accelerate curing and provide durable protection against harsh marine environments.

4.5 Protective Coatings

Protective coatings are applied to a wide range of industrial equipment and infrastructure to prevent corrosion, abrasion, and chemical attack. BDMAEE is used in these coatings to enhance the curing speed and provide long-lasting protection in demanding environments. Examples include coatings for pipelines, storage tanks, and bridges.

5. Advantages of Using BDMAEE

The use of BDMAEE in industrial coating formulations offers several significant advantages:

5.1 Accelerated Curing Time

The primary advantage of BDMAEE is its ability to significantly reduce the curing time of coatings. This acceleration is crucial for improving production efficiency and minimizing downtime.

5.2 Improved Throughput

By reducing the curing time, BDMAEE enables higher throughput in coating operations. This increased throughput translates into higher productivity and reduced manufacturing costs.

5.3 Enhanced Coating Properties

In many cases, the use of BDMAEE can also lead to improved coating properties, such as hardness, gloss, chemical resistance, and adhesion. These improvements are often attributed to the more complete and uniform curing achieved with the catalyst.

5.4 Lower Energy Consumption

In some coating processes, the curing step requires elevated temperatures. By accelerating the curing process, BDMAEE can reduce the energy required to heat the coatings, leading to lower energy consumption and reduced environmental impact.

6. Disadvantages and Limitations

Despite its numerous advantages, BDMAEE also has some disadvantages and limitations that need to be considered when formulating industrial coatings:

6.1 Volatility and Odor

BDMAEE is a volatile compound with a characteristic amine odor. This odor can be unpleasant and may require the use of ventilation systems to maintain acceptable air quality in the workplace. The volatility of BDMAEE can also lead to its gradual loss from the coating formulation, potentially affecting the long-term performance of the coating.

6.2 Potential for Yellowing

In some cases, the use of BDMAEE can contribute to yellowing of the coating, particularly upon exposure to UV light. This yellowing can be undesirable, especially in coatings that are intended to be clear or white.

6.3 Compatibility Issues

BDMAEE may not be compatible with all coating formulations. It can react with certain components or interfere with other additives, leading to undesirable effects such as gelling, precipitation, or reduced coating performance.

6.4 Over-Catalyzation

Using too much BDMAEE can lead to over-catalyzation, which can result in rapid and uncontrolled curing, leading to defects such as blistering, cracking, or poor adhesion.

7. Safety Considerations

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

7.1 Toxicity

BDMAEE is considered to be moderately toxic. It can cause skin and eye irritation upon contact. Inhalation of vapors can cause respiratory irritation. Ingestion can cause gastrointestinal distress. Appropriate personal protective equipment (PPE), such as gloves, goggles, and respirators, should be used when handling BDMAEE.

7.2 Handling and Storage

BDMAEE should be handled in a well-ventilated area. It should be stored in tightly closed containers in a cool, dry place away from heat, sparks, and open flames. Contact with incompatible materials, such as strong acids and oxidizing agents, should be avoided.

7.3 Environmental Impact

BDMAEE can be harmful to aquatic organisms. Spills should be contained and cleaned up immediately. Waste containing BDMAEE should be disposed of in accordance with local regulations.

8. Formulation Considerations

Effective use of BDMAEE in coating formulations requires careful consideration of several factors:

8.1 Dosage

The optimal dosage of BDMAEE depends on the specific coating formulation, the desired curing rate, and the desired coating properties. Typically, BDMAEE is used at concentrations ranging from 0.1% to 2% by weight of the resin solids. Excessive use can lead to the disadvantages mentioned earlier.

8.2 Compatibility with other Additives

It is essential to ensure that BDMAEE is compatible with all other additives in the coating formulation, such as pigments, fillers, stabilizers, and flow control agents. Incompatibility can lead to phase separation, sedimentation, or other undesirable effects.

8.3 Influence of Temperature and Humidity

The curing rate of coatings catalyzed by BDMAEE is influenced by temperature and humidity. Higher temperatures generally accelerate the curing process, while high humidity can sometimes inhibit the curing reaction, particularly in polyurethane systems.

9. Alternative Catalysts

While BDMAEE is a widely used catalyst, alternative catalysts are available for industrial coating applications.

9.1 Other Tertiary Amines

Other tertiary amines, such as triethylamine (TEA), triethylenediamine (TEDA), and N,N-dimethylcyclohexylamine (DMCHA), can also be used as catalysts in coating formulations. However, these amines may have different catalytic activities and may affect the coating properties differently.

9.2 Metal Catalysts

Metal catalysts, such as tin compounds (e.g., dibutyltin dilaurate, DBTDL), zinc compounds, and bismuth compounds, are also commonly used in polyurethane coatings. Metal catalysts are generally more active than tertiary amines, but they can also be more toxic and can contribute to yellowing.

9.3 Amine Blocking Agents

Amine blocking agents can be used to temporarily deactivate BDMAEE or other amine catalysts, allowing for longer pot life of the coating formulation. The blocking agent is typically a compound that reacts with the amine nitrogen, rendering it unreactive. The blocking agent can be removed by heating or by reaction with another component of the coating formulation, thereby reactivating the amine catalyst.

10. Future Trends and Developments

The future of BDMAEE in industrial coatings is likely to be shaped by several trends and developments:

• Development of Low-Odor BDMAEE Derivatives: Research efforts are focused on developing BDMAEE derivatives with lower volatility and reduced odor, addressing a major drawback of the current product.
• Combination with other Catalysts: Synergistic catalyst systems combining BDMAEE with other catalysts, such as metal catalysts or enzymes, are being explored to achieve optimal curing performance and coating properties.
• Microencapsulation of BDMAEE: Encapsulating BDMAEE in microcapsules can provide controlled release of the catalyst, allowing for improved control over the curing process and extended pot life of the coating formulation.
• Bio-based Alternatives: There is growing interest in developing bio-based alternatives to BDMAEE, derived from renewable resources. This would contribute to more sustainable coating formulations.
• Further Optimization of Dosage & Compatibility: Research continues to optimize the dosage of BDMAEE for specific applications and to improve its compatibility with a wider range of coating components.

11. Conclusion

Bis[2-(N,N-Dimethylaminoethyl)] ether (BDMAEE) remains a vital catalyst in the industrial coatings industry, particularly in polyurethane and epoxy systems. Its ability to accelerate curing, improve throughput, and enhance coating properties makes it a valuable tool for formulators. While its volatility, odor, and potential for yellowing pose challenges, ongoing research and development efforts are focused on mitigating these drawbacks and exploring new applications. The future of BDMAEE in industrial coatings is likely to involve the development of lower-odor derivatives, synergistic catalyst systems, microencapsulation techniques, and bio-based alternatives, contributing to more sustainable and high-performance coating solutions.

12. References

1. Wicks, D. A., Jones, F. N., & Pappas, S. P. (2007). Organic Coatings: Science and Technology. John Wiley & Sons.
2. Lambourne, R., & Strivens, T. A. (1999). Paint and Surface Coatings: Theory and Practice. Woodhead Publishing.
3. Ashby, J., & Goode, R. J. (2001). High Solids Alkyd Resins. John Wiley & Sons.
4. Ulrich, H. (1996). Introduction to Industrial Polymers. Hanser Gardner Publications.
5. Römpp Online, Georg Thieme Verlag. (Chemical database; search for "Bis(2-dimethylaminoethyl) ether").
6. Database of REACH registered substances, European Chemicals Agency. (Search for "Bis(2-dimethylaminoethyl) ether").
7. Randall, D., & Lee, S. (2002). The Polyurethanes Book. John Wiley & Sons.
8. Primeaux, D. J., & Lindsly, C. (1996). US Patent 5508344. Method of reducing odor in amine catalysts.
9. Blank, W.J. (1982). Progress in Organic Coatings, 10(3), 255-271. The Chemistry of Amine Catalyzed Epoxy Resins.
10. Bauer, D. R., & Dickie, R. A. (1980). Journal of Coatings Technology, 52(660), 63-67. Amine-epoxy cure kinetics.

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