Copper–amine complexes as new catalysts for rigid polyurethane foam preparations

Abstract

A new class of catalyst for the preparation of rigid polyurethane (RPUR) foams was developed. Metal(II)-amine complexes [M(en) 2 and M(trien), where M ¼ Cu or Ni, en ¼ ethylenediamine, and trien ¼ triethylenetetramine] were synthesized and used as catalysts in the preparation of RPUR foams. The catalytic activity of the metal(II)-amine complexes and properties of the RPUR foams were investigated and compared to those prepared by N,N-dimethylcyclohexylamine (DMCHA), which is a common commercial tertiary amine catalyst used in the preparation of RPUR foams. The use of M(en) 2 and M(trien) can improve the working environment in RPUR foam processing because DMCHA and other commercial tertiary amine catalysts have a strong odor, whereas M(en) 2 and M(trien) do not have any odor. The reaction times in RPUR foam preparation, namely, cream time, gel time, tack-free time, and rise time, were investigated. These data indicated that the copper-ethylenediamine complex [Cu(en) 2 ] and copper-triethylenetetramine complex [Cu(trien)] had comparable catalytic activity to DMCHA, whereas the catalytic activity of the nickel complexes was not good. Attenuated total reflection-IR spectroscopy of the RPUR foams prepared with Cu(en) 2 and Cu(trien) showed quantitative isocyanate (NCO) conversion. The density and compressive strength of the RPUR foams prepared from Cu(en) 2 and Cu(trien) were comparable to those prepared from DMCHA.

Copper-amine complex solution as a low-emission catalyst for flexible polyurethane foam preparation

“…The foaming reaction was done at room temperature. At the start of the foaming reaction, the metal complex did not dissociate and Cu(OAc) 2 (en) 2 -EG catalyzed the reaction according to the proposed mechanism reported in our previous work as follows (14): Copper atom in Cu(OAc) 2 (en) 2 acts as a Lewis acid and coordinates with the oxygen atom of the NCO group, which causes the NCO carbon to be more electrophilic. The nitrogen atom in Cu(OAc) 2 (en) 2 interacts with the proton of the hydroxyl group and causes the hydroxyl oxygen to be more nucleophilic, which then reacts with the isocyanate group to give a urethane linkage.…”

“…Therefore, Cu(OAc) 2 (en) 2 -EG and Cu(OAc) 2 (trien)-EG were characterized in the form of solution ethylene glycol. Like in our previous work (14), Cu(OAc) 2 (en) 2 and Cu(OAc) 2 (trien) were synthesized using acetone as a solvent. After the removal of acetone, the purified Cu(OAc) 2 (en) 2 and Cu(OAc) 2 (trien) were obtained as a solid and a liquid, respectively.…”

“…Our research group synthesized new catalysts with good catalytic activity for the preparation of water-blown rigid polyurethane (RPUR) foams (14). These catalysts were copper-amine complexes, Cu(OAc) 2 (en) 2 and Cu(OAc) 2 (trien) (where en indicates ethylenediamine; trien, triethylenetetramine).…”

Smoke and toxicity suppression by zinc salts in flame‐retardant polyurethane‐polyisocyanurate foams filled with phosphonate and chlorinated phosphate

“…Generally speaking, these factors promote char formation and reduce the release of -NCO containing compounds. 33 ZF is excellent for delaying the release time of PO 2 -which may be attributed to the fact than iron as a transition element has higher catalytic activity in char formation at the initial stage of thermal degradation. 15 In addition, ZA is excellent for delaying the release of HCN, possibly indicating that the stability of FPUR-PIR-ZA char, which delayed the release of nitrogen- containing compounds at higher temperature, is better than other systems.…”

Metal acetylacetonate–amine and metal nitrate–amine complexes as low‐emission catalysts for rigid polyurethane foam preparation

“…From the previous work in our group, copper acetate–ethylenediamine complex [Cu(OAc) 2 (en) 2 ] was synthesized from the reaction between copper acetate [Cu(OAc) 2 ] and ethylenediamine (en) . Cu(OAc) 2 (en) 2 can be used as a catalyst in RPUR foam preparation and shows comparable catalytic activity with the commercial catalyst (DMCHA).…”