On the Mechanism of Polyurethane Formation Catalyzed by Metal Chelates and Organotin Compounds

Lipatova, T.E.; Bakalo, L.A.; Niselsky, Yu. N.; Sirotinskaya, A.L.

doi:10.1080/00222337008059519

Cited by 19 publications

(6 citation statements)

References 8 publications

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“…[6,7] Nowadays, two types of metal-based catalysts are mainly used in the polyurethane industry: tin (e.g. dibutyltin dilaurate, DBTDL) [8][9][10][11][12] and mercury (such as [bis(phenyl mercury) dodecenyl succinate and bis(t-butyl mercury) dodecenyl succinate]) [13,14] compounds. The former present exceptional catalytic activity, and the latter are ideal latent catalysts which allow for more time to handle the formulation.…”

Section: Introductionmentioning

confidence: 99%

Novel nucleophilic/basic and acidic organocatalysts for reaction between poorly reactive diisocyanate and diols

Belmokaddem

Dagonneau

Lhomme

et al. 2016

Designed Monomers and Polymers

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International audienceOriginal basic or acidic organic compounds derived from guanidine or phenyl phosphonic acid were specifically designed and tested as new catalysts for the bulk synthesis of polyurethane prepolymers from a precursor system with particularly low reactivity (secondary alcohol + aliphatic isocyanate at low temperature). Both families showed interesting catalytic activities at 60-80 degrees C, but must nevertheless be used in much higher amounts (1mol%, i.e. between 0.15 and 0.50wt%) than traditional metal-based catalysts. The efficiency of guanidine derivatives seems to be related to their nucleophilicity, whereas that of phosphonic acid derivatives depends on their acidity. However, the solubility of the considered species in the reactive medium also plays a major role. The water/alcohol selectivity of the catalysts, especially at room temperature, was then examined as an additional criterion. Guanidines are not selective and favor the reaction of isocyanate groups with water as much as that with alcohols. Phenyl phosphonic acid derivatives are more selective, and particularly pentafluorophenyl phosphonic acid displays a remarkable catalytic activity together with an acceptable selectivity and could represent an interesting and safer alternative to toxic tin and mercury derivatives for many industrial polyurethanes

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Section: Introductionmentioning

confidence: 99%

Novel nucleophilic/basic and acidic organocatalysts for reaction between poorly reactive diisocyanate and diols

Belmokaddem

Dagonneau

Lhomme

et al. 2016

Designed Monomers and Polymers

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“…It was later found that metals can complex with isocyanate,27, 29–33 with alcohol,27, 32, 34–39 and with both isocyanate and alcohol 27, 28, 31. For example, Reegen and Frisch,32 who were studying isocyanate–DBTDL and 1‐methoxy‐2‐propanol–DBTDL complex formation in benzene solutions, concluded that DBTDL could complex with both isocyanate and alcohol, the fraction of the catalyst involved in the isocyanate complexes being significantly larger (40–50% of the DBTDL molecules being tied up in those complexes) than in complexes with alcohol (13–21% of the DBTDL molecules).…”

Section: Resultsmentioning

confidence: 99%

Brachytherapy in total coronary occlusions: Quidquid agis, prudenter agas, et respice finem

Hehrlein¹

2003

Cathet Cardio Intervent

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In the study by Jain et al. presented in this issue, vascular brachytherapy was performed, applying a betaradiation source (BetaCath TM) to reduce restenosis rates after PTCA of chronic total occlusions (CTOs). The outcome of radiotherapy after percutaneous revascularization of 82 CTOs were analyzed from the RENO registry database, which contains 1,098 consecutive patients undergoing brachytherapy. The results were comparable with those known for brachytherapy of nonocclusive in-stent restenosis with respect to prevention of new restenosis. Why is this finding remarkable?It has become general knowledge that treating chronic coronary occlusions by conventional PTCA is a "different animal" compared with PTCA of plain coronary artery stenosis [1]. Many studies have shown that restenosis rates are extremely high in patients with CTO, even when stenting is performed [2]. Some institutions leave treatment of symptomatic CTOs primarily to the cardiac surgeon. Revascularization of CTO is favorable over medical treatment at least when treated surgically [3]. Therefore, it is important to realize from the report by Jain et al. that restenosis rates of PTCA in CTO have been reduced dramatically using vascular brachytherapy. However, there is the problem of thrombotic vessel occlusion increasing MACE rates, which needs to be understood and acted on. Brachytherapy was plagued from the beginning with the occurrence of late and "late late" thrombosis [4]. Yet only half of all patients of the RENO registry were kept on the combined antiplatelet therapy of aspirin and clopidogrel for a period of 6 months. In addition, new stents were implanted, which tended to reocclude the coronary arteries. What are the lessons we learn from this report? In the words of Gesta Romanorum: "Quidquid agis, prudenter agas, et respice finem." Whatever you do, do it thoughtfully, and kept in mind the goal.Brachytherapy of chronic coronary occlusions requires special attention to the increased risk of thrombotic vessel occlusion. Potential means for reducing the risks of MACE are as follows: apply aspirin and clopidogrel for a minimum period of 12 months (perhaps as lifelong addition of clopidogrel to aspirin medication); use a minimum of new stents to reduce foreign-body activation of platelets; study an increased loading and maintenance dose of clopidogrel in a randomized fashion in the setting of CTO; and, most importantly, remember that CTO patents only benefit from revascularization if viable myocardium is present [5].Mixed results were obtained by other investigators in two recent studies applying brachytherapy in CTO. One group reported similar efficacy and complication rates with intracoronary brachytherapy of occluded in-stent restenosis using a gamma-emitter (Ir-192) compared with irradiation for nonocclusive in-stent restenosis [6]. The other group, however, clearly pointed out that radiotherapy of total occlusions from in-stent restenosis causes increased MACE rates compared with brachytherapy of plain in-stent restenosis [7]. In summary, m...

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“…The molecular size distribution of the different oligomers was directly related to the stoichiometric ratio [OH]/[NCO] and the difference in reactivity between the two NCO functions carried by the diisocyanate: the smaller the difference was, the higher the probability was to give long chains and, in parallel, unreacted diisocyanate during the polycondensation process. The reactivity‐constant ratio for a given diisocyanate molecule toward hydroxyl compounds depended on the structure of the diisocyanate and the synthesis conditions (e.g., the temperature and the use of a catalyst) 10–20. For symmetric diisocyanates, such as H 12 MDI and 2,6‐TDI, the initial reactivity of both NCO functions toward hydroxyl compounds was identical a priori.…”

Section: Resultsmentioning

confidence: 99%

Effect of the diisocyanate on the structure and properties of polyurethane acrylate prepolymers

Barbeau

Gérard

Magny

et al. 2000

J. Polym. Sci. B Polym. Phys.

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In this study, we investigated the role of diisocyanate on the properties of polyurethane acrylate (PUA) prepolymers based on polypropylene oxide (M̄n = 2000 g · mol−1). The diisocyanates studied were isophorone diisocyanate, 4‐4′dicyclohexylmethane diisocyanate, and toluene diisocyanate (pure 2,4‐TDI, pure 2,6‐TDI, and a TDI mixture, TDItech). The molecular structure of the diisocyanate had a major role on the course of the polycondensation and, more precisely, on the sequence length distribution of the final prepolymer. Moreover, the structural organization of the prepolymer also strongly depended on the nature of the diisocyanate. Two types of behaviors were particularly emphasized. On the one hand, the PUA synthesized from 2,4‐TDI displayed an enhanced intermixing between soft polyether segments and hard urethane groups, as revealed by the analysis of hydrogen bonding in Fourier transform infrared. Consecutively, the glass transition shifted to higher temperatures for these polymers. On the other hand, strong hard–hard inter‐urethane associations were observed in 2,6‐TDI‐based prepolymers; these led to microphase segregation between polyether chains and urethane groups, as revealed by optical microscopy. This inhomogeneous structure was thought to be responsible for the unusual rheological behavior of these PUA prepolymers. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2750–2768, 2000

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On the Mechanism of Polyurethane Formation Catalyzed by Metal Chelates and Organotin Compounds

Cited by 19 publications

References 8 publications

Novel nucleophilic/basic and acidic organocatalysts for reaction between poorly reactive diisocyanate and diols

Novel nucleophilic/basic and acidic organocatalysts for reaction between poorly reactive diisocyanate and diols

Brachytherapy in total coronary occlusions: Quidquid agis, prudenter agas, et respice finem

Effect of the diisocyanate on the structure and properties of polyurethane acrylate prepolymers

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