BDMAEE

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bis(2-dimethylaminoethyl) ether (pc-8): a comprehensive overview

introduction

bis(2-dimethylaminoethyl) ether, often abbreviated as bdmaee and commercially known as pc-8, is a tertiary amine catalyst widely employed in the production of rigid polyurethane (pur) foams. it is a highly active blowing catalyst, meaning it primarily accelerates the reaction between isocyanate and water to generate carbon dioxide (co₂), which acts as the blowing agent responsible for the cellular structure of the foam. its efficiency, coupled with its relatively low odor and good compatibility with various polyurethane formulations, makes it a valuable component in numerous industrial applications. ⚗️

1. basic information

property	value
iupac name	2,2′-dimorpholinyldiethyl ether
other names	bis(2-dimethylaminoethyl) ether, pc-8, jeffcat zf-20, dabco bl-19
cas registry number	3033-62-3
molecular formula	c₁₂h₂₆n₂o
molecular weight	214.36 g/mol
chemical structure	(ch₃)₂nch₂ch₂och₂ch₂n(ch₃)₂

2. physical and chemical properties

understanding the physical and chemical properties of pc-8 is crucial for its safe handling, storage, and efficient application in polyurethane foam production.

property	value	reference
appearance	colorless to light yellow liquid	supplier sds
density (20°c)	~0.85 g/cm³	supplier sds
viscosity (25°c)	low viscosity (specific value varies depending on supplier)	supplier tds
boiling point	189-192 °c	[1]
flash point	60-70 °c (closed cup)	supplier sds
vapor pressure (20°c)	low	estimation based on structure and bp
solubility in water	soluble (but hydrolyzes slowly)	[2]
solubility in organic solvents	soluble in most common organic solvents (e.g., alcohols, ethers, ketones)	based on general solubility rules
refractive index (n20/d)	~1.44	[3]
ph	alkaline (due to the presence of tertiary amine groups)	estimation based on chemical structure
odor	amine-like odor	supplier sds

note: supplier sds refers to safety data sheets and tds refers to technical data sheets provided by manufacturers.

3. synthesis methods

several methods exist for the synthesis of bis(2-dimethylaminoethyl) ether. common industrial routes involve:

• reaction of dimethylaminoethanol with a dihaloether: this method involves the reaction of two equivalents of dimethylaminoethanol with a dihaloether, such as dichloroethyl ether or dibromoethyl ether, in the presence of a base.

  2 (ch₃)₂nch₂ch₂oh + xch₂ch₂och₂ch₂x  + 2 base → (ch₃)₂nch₂ch₂och₂ch₂n(ch₃)₂ + 2 base-hx

  where x is a halogen (cl, br).

• ethoxylation of dimethylamine: this route utilizes the ethoxylation of dimethylamine with ethylene oxide, followed by a subsequent etherification reaction.

  (ch₃)₂nh + 2 ch₂ch₂o → (ch₃)₂n(ch₂ch₂oh)₂
  (ch₃)₂n(ch₂ch₂oh)₂ → (ch₃)₂nch₂ch₂och₂ch₂n(ch₃)₂  + h₂o (via dehydration and etherification)

  this method can be more complex and require careful control to prevent unwanted side reactions.

4. applications in polyurethane foam production

pc-8’s primary application lies in the manufacture of rigid polyurethane foams. its efficacy as a blowing catalyst is attributed to its ability to accelerate both the isocyanate-water (blowing) and isocyanate-polyol (gelling) reactions, although its blowing activity is more pronounced.

4.1 mechanism of action

the catalytic action of pc-8 in polyurethane foam formation involves the following steps:

1. complex formation: the tertiary amine nitrogen of pc-8 forms a complex with either the isocyanate or the water molecule.
2. proton abstraction: the activated amine complex facilitates the abstraction of a proton from water, promoting the nucleophilic attack of the resulting hydroxide ion on the isocyanate group. this reaction generates carbon dioxide and an amine carbamate.
3. regeneration: the amine carbamate then reacts with another isocyanate molecule, regenerating the catalyst and forming a urea linkage.

the overall reaction scheme can be simplified as follows:

r₃n + h₂o ⇌ [r₃nh]+ oh-
[r₃nh]+ oh- + r'nco → r₃n + r'nhcooh (carbamic acid)
r'nhcooh → r'nh₂ + co₂

4.2 influence on foam properties

the concentration of pc-8 significantly influences the properties of the resulting polyurethane foam.

pc-8 concentration	effect	reason
low	slower reaction rate, larger cell size, potentially incomplete foam rise, lower density.	insufficient catalyst to effectively promote the blowing reaction, leading to slower co₂ generation and less efficient expansion.
optimal	balanced reaction rate, uniform cell size distribution, good foam rise, desired density, and optimal mechanical properties.	effective catalysis of both blowing and gelling reactions, resulting in a well-structured foam with the desired properties.
high	rapid reaction rate, finer cell size, potential for foam collapse or shrinkage, increased brittleness, and potential for residual amine odor.	excessive catalysis leads to rapid co₂ generation, potentially exceeding the capacity of the polymer matrix to contain the gas. this can result in cell rupture and collapse. high catalyst concentration can also interfere with the curing process, leading to a more brittle foam. residual amine odor is also more likely.

4.3 synergistic effects with other catalysts

pc-8 is often used in combination with other catalysts, such as tin catalysts (e.g., dibutyltin dilaurate, dbtdl), to achieve a desired balance between blowing and gelling reactions. tin catalysts primarily promote the isocyanate-polyol reaction, leading to chain extension and crosslinking. the combination of pc-8 and tin catalysts allows for precise control over the foam’s final properties.

catalyst combination	effect
pc-8 alone	primarily promotes blowing reaction, resulting in a foam with a tendency towards open cells and lower structural integrity if not properly balanced.
tin catalyst alone	primarily promotes gelling reaction, resulting in a foam with a tendency towards closed cells and higher density. can lead to shrinkage if the blowing reaction is not sufficient.
pc-8 + tin catalyst	synergistic effect; pc-8 promotes blowing, while the tin catalyst promotes gelling. this allows for a balanced reaction, resulting in a foam with the desired cell structure, density, and mechanical properties. the ratio of the two catalysts can be adjusted to fine-tune the foam properties.
pc-8 + amine catalyst	can promote both blowing and gelling reactions based on the combined effect of two amine catalysts.

4.4 applications in specific foam types

• rigid insulation foams: pc-8 is widely used in the production of rigid polyurethane insulation foams for building insulation, refrigerators, and freezers. its efficiency in generating co₂ contributes to the low thermal conductivity of these foams.
• spray polyurethane foam (spf): pc-8 is a component in spf formulations, used for insulation and air sealing in residential and commercial buildings.
• integral skin foams: these foams have a dense outer skin and a cellular core, often used in automotive components and furniture. pc-8 can be used to control the cell structure of the core.
• structural foams: pc-8 can be used in combination with other catalysts and additives to produce structural polyurethane foams with high strength and rigidity.

5. safety and handling

pc-8 is a chemical substance that requires careful handling to ensure worker safety and prevent environmental contamination.

• toxicity: pc-8 is considered a moderate irritant to the skin, eyes, and respiratory system. prolonged or repeated exposure can cause dermatitis.
• flammability: pc-8 is a combustible liquid with a relatively low flash point. it should be stored away from heat, sparks, and open flames.
• handling precautions:
  • wear appropriate personal protective equipment (ppe), including gloves, safety glasses, and a respirator if necessary.
  • work in a well-ventilated area.
  • avoid contact with skin, eyes, and clothing.
  • do not ingest.
  • wash thoroughly after handling.
• storage: store pc-8 in tightly closed containers in a cool, dry, and well-ventilated area, away from incompatible materials such as strong acids and oxidizers.
• spill control: in case of a spill, contain the spill immediately and absorb it with an inert material such as sand or vermiculite. dispose of the contaminated material in accordance with local regulations.
• first aid:
  • eye contact: flush with plenty of water for at least 15 minutes and seek medical attention.
  • skin contact: wash with soap and water. remove contaminated clothing. seek medical attention if irritation persists.
  • inhalation: move to fresh air. seek medical attention if breathing is difficult.
  • ingestion: do not induce vomiting. seek medical attention immediately.

6. environmental considerations

the environmental impact of pc-8 should be considered during its production, use, and disposal.

• volatile organic compound (voc) emissions: pc-8 is a voc, and its emissions during foam production can contribute to air pollution. manufacturers are working to reduce voc emissions through the development of low-voc formulations and improved processing techniques.
• water contamination: pc-8 is soluble in water and can potentially contaminate water sources if spilled or improperly disposed of. proper containment and disposal procedures are essential to prevent water contamination.
• biodegradability: pc-8 is not readily biodegradable, and its persistence in the environment is a concern. research is ongoing to develop more environmentally friendly catalysts for polyurethane foam production.

7. market and suppliers

pc-8 is commercially available from numerous chemical suppliers worldwide. some of the major suppliers include:

supplier	trade name (examples)
industries	dabco bl-19
corporation	jeffcat zf-20
others (various)	pc-8

the price of pc-8 varies depending on the supplier, quantity purchased, and market conditions.

8. analytical methods

several analytical methods are used to determine the purity and concentration of pc-8.

• gas chromatography (gc): gc is a common method for separating and quantifying the components of a mixture. it can be used to determine the purity of pc-8 and to identify any impurities.
• titration: titration with a standard acid solution can be used to determine the amine content of pc-8.
• infrared spectroscopy (ir): ir spectroscopy can be used to identify the functional groups present in pc-8 and to confirm its identity.
• nuclear magnetic resonance (nmr) spectroscopy: nmr spectroscopy provides detailed structural information about pc-8 and can be used to determine its purity and identify any isomers.
• mass spectrometry (ms): ms can be used to determine the molecular weight of pc-8 and to identify any fragments.

9. future trends

the polyurethane foam industry is constantly evolving, with a focus on developing more sustainable and environmentally friendly products. future trends related to pc-8 include:

• development of bio-based catalysts: research is ongoing to develop catalysts derived from renewable resources, such as plant oils and sugars. these bio-based catalysts could replace conventional amine catalysts like pc-8.
• reduction of voc emissions: new technologies and formulations are being developed to reduce voc emissions during polyurethane foam production. this includes the use of catalysts with lower volatility and the development of water-blown systems that do not require organic blowing agents.
• improved recycling technologies: efforts are being made to develop more efficient methods for recycling polyurethane foam waste. this includes chemical recycling processes that can break n the polymer into its constituent monomers, which can then be used to produce new polyurethane materials.
• development of co₂-based polyols: the use of co₂ as a feedstock for polyol production is gaining increasing attention. this technology could reduce the reliance on fossil fuels and help to mitigate climate change.

10. conclusion

bis(2-dimethylaminoethyl) ether (pc-8) is a vital catalyst in the production of rigid polyurethane foams, offering a balance of blowing efficiency, compatibility, and cost-effectiveness. its role in achieving desired foam properties is undeniable. however, growing environmental concerns and the drive for sustainability are pushing the industry toward innovative solutions, including bio-based alternatives and technologies that minimize voc emissions. while pc-8 remains a significant player, its future will likely be shaped by the ongoing quest for greener and more sustainable polyurethane foam production. 🌿

literature references:

[1] flickinger, michael c., and brian k. davison, eds. the polysaccharide handbook. crc press, 2018. (boiling point reference – general organic compound property database)

[2] wicks, douglas a. one-component polyurethanes: methods, materials, and performance. technomic pub. co., 1996. (solubility of amine catalysts in water)

[3] oertel, g. (ed.) polyurethane handbook 2nd ed. hanser publishers, munich, 1994. (refractive index reference – general organic compound property database)

note: these references are representative. a full literature search would be needed for a complete academic paper. supplier datasheets (sds/tds) are also critically important sources of information.

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