Polycarbodiimide

Two-component waterborne urethane dispersions are similar to the one-component PUD s in that a polyurethane dispersion comprises one of the two components. The second component is usually a crosslinker from the following classes of materials (a) polyisocyanates, (b) aziridines, (c) polycarbodiimides, and (d) epoxies. Many of the crosslinkers are not inherently water-soluble or water-dispersible. Therefore, they must be modified with surface active agents themselves, so as to become emulsifiable in water. 

Schollenberger added 2% of a polycarbodiimide additive to the same poly(tetra-methylene adipate) urethane with the high level of acid (AN = 3.66). After 9 weeks of 70°C water immersion, the urethane was reported to retain 84% of its original strength. Carbodiimides react quickly with residual acid to form an acyl urea, removing the acid catalysis contributing to the hydrolysis. New carbodiimides have been developed to prevent hydrolysis of polyester thermoplastics. Carbodiimides are also reported to react with residual water, which may contribute to hydrolysis when the urethane is exposed to high temperatures in an extruder [90]. 

High modulus blends can be developed by mixing TPU with acetal copolymer (trioxane ethylene oxide copolymers) [242-244]. The highly crystalline acetal forms a second continuous phase. Kumar et al. studied behavior of such blends [245]. TPU retains none of its physical properties after immersion in water at 70°C for three weeks. The hydrolysis resistance of TPU can be improved by blending with polycarbodiimides [246]. Two parts of carbodiimide with TPU offer 87% retention of its strength, 93% of elongation, and 75% of modulus under the same... 

Polycarbodiimides are also used as additives to provide long-term hydrolytic stability to polyester components in service in moist and humid environments (e.g. glass-filled PET in dishwasher applications). 

Heitz et al. [35] (BASF) describe the use of polycarbodiimide as an additive to produce hydrolysis-resistant PBT. Further patents describe glass-fiber-reinforced mixtures of PBT with an aromatic polycarbodiimide having improved impact strength [36], and mixtures of PBT with an aromatic polycarbodiimide having improved melt strength and intrinsic viscosity [37],... 

Stabaxol KE 7646 (Rhein Chemie, Mannheim, Germany) is a masterbatch based on PET plus an aromatic polycarbodiimide. 

Thomas, N. W Berardinelli, F. M. and Edelman, R., Polycarbodiimide modification of polyesters for extrusion applications, US Patent 4 071 503 (to Celanese Corporation, New York), 1978. 

Aromatic polycarbodiimides act as very efficient cross-linkers in waterborne emulsion systems and have the added advantage that they are much less toxic than traditional polyaziridines (Brown, 1995). 

To a flask containing 20 gm (0.08 mole) of methylenebis(4-phenyl isocyanate) in 150 ml of xylene is added 0.03 gm of l-ethyl-3-methyl-3-phospholine-l-oxide catalyst. The solution is refluxed for 4 hr, during which time carbon dioxide is being evolved. The xylene solvent is removed under reduced pressure to afford a nearly quantitative yield of the solid polycarbodiimide. The latter polymer was pressed at 250°C to afford a clear, crystalline, orientable film with a tenacity of about 50,000 psi, an initial modulus of 410,000 psi, and a 20 % elongation at 25°C. 

Polycarbodiimide foams from polyisocyanates and 0.001-1% by weight of phospholine or phospholidine [82],... 

Preparation of a Polycarbodiimide from Methylenebis(4-phenyl Isocyanate). 212... 

Imashiro et al. (3) prepared polycarbodiimides using 4,4,-dicyclohexylmethane diisocyanate terminated with moisture-resistant diisocyanates. 

MC MDI MEKP MF MMA MPEG MPF NBR NDI NR OPET OPP OSA PA PAEK PAI PAN PB PBAN PBI PBN PBS PBT PC PCD PCT PCTFE PE PEC PEG PEI PEK PEN PES PET PF PFA PI PIBI PMDI PMMA PMP PO PP PPA PPC PPO PPS PPSU Methyl cellulose Methylene diphenylene diisocyanate Methyl ethyl ketone peroxide Melamine formaldehyde Methyl methacrylate Polyethylene glycol monomethyl ether Melamine-phenol-formaldehyde Nitrile butyl rubber Naphthalene diisocyanate Natural rubber Oriented polyethylene terephthalate Oriented polypropylene Olefin-modified styrene-acrylonitrile Polyamide Poly(aryl ether-ketone) Poly(amide-imide) Polyacrylonitrile Polybutylene Poly(butadiene-acrylonitrile) Polybenzimidazole Polybutylene naphthalate Poly(butadiene-styrene) Poly(butylene terephthalate) Polycarbonate Polycarbodiimide Poly(cyclohexylene-dimethylene terephthalate) Polychlorotrifluoroethylene Polyethylene Chlorinated polyethylene Poly(ethylene glycol) Poly(ether-imide) Poly(ether-ketone) Polyethylene naphthalate Polyether sulfone Polyethylene terephthalate Phenol-formaldehyde copolymer Perfluoroalkoxy resin Polyimide Poly(isobutylene), Butyl rubber Polymeric methylene diphenylene diisocyanate Poly(methyl methacrylate) Poly(methylpentene) Polyolefins Polypropylene Polyphthalamide Chlorinated polypropylene Poly(phenylene oxide) Poly(phenylene sulfide) Poly(phenylene sulfone)... 

Coupling reactions Coupling of PBT with diisocyanate and polyepoxide or polycarbodiimide, coupling of PET with bis(2-oxalzoline)... 

Imashiro [3] converted p-diphenylmethane diisocyanate, (IV), into the corresponding polycarbodiimide, (V), and then postreacted with dibutyl amine forming the corresponding polyguanidine derivative, (VI). 

I would like to acknowledge the contributions of my former co-workers at the Donald S. Gilmore Research Laboratories of the Upjohn Company, especially Dr R.H. Richter and B. Tucker who were involved in the synthesis and cycloaddition reactions of carbodiimides Dr L.M. Alberino who participated in the synthesis of polycarbodiimides Dr K. Onder and Dr WJ. Farrissey, Jr, who played a major role in the development of thermoplastic polyamides based on carbodiimide chemistry Dr H.W. Temme and Dr C.P. Smith, who developed novel polymeric catalysts for the conversion of isocyanates into carbodiimides and A. Odinak, who developed the liquid MDI process. 1 would especially like to acknowledge the encouragement of the late Dr A.A.R. Sayigh. 

Review articles on carbodiimides were published by Khorana in 1953, by Kurzer and Douraghi-Zadeh in 1967, byMikolajczykandKielbasinski in 1981 and by Williams and Ibrahim in 1981. Carbodiimides containing silicon, germanium, tin and lead substituents were reviewed by Gordetsov and coworkers in 1982, N-functionalized carbodiimides by Vovk and Samarai in 1992 and polycarbodiimides by Pankratov in 1993. A review on the synthesis of heterocycles by the aza-Wittig reaction appeared in 1991. ... 

Polyhexamethylenecarbodiimide, an insoluble condensation reagent for the synthesis of peptides, is obtained in the reaction of hexamethylene diisocyanate with a phospholene oxide catalyst in NMP. The isocyanate end groups are reacted with ethanol. Linear polycarbodiimides, upon reaction with adipic acid, form polyureides. For example, reaction of the 2,4-TDI derived carbodiimide with adipic acid in DMF produces the polymer, mp295°C.222... 

Melt processable linear polycarbodiimides cannot be obtained in the polymerization of aromatic diisocyanates with a phospholene oxide catalyst.However, some of the high molecular weight polymers can be molded into clear tough films, but the tensile properties of these films decrease with increasing temperature. ... 

A 16 membered ring carbodiimide is obtained in the reaction of Me2SiCl2 with cyanamide." In addition to the tetramer, oligomers with n = 2 to 7 are detected. Also, higher oligomeric carbodiimides are formed in the reaction of alkyl- and dialkyl silicon chlorides with cyanamide in the presence of pyridine." Also, from bis(trimethylsilyl)carbodiimide and silicon tetrachloride in the presence of pyridine, the silicon polycarbodiimide 34 is obtained." ... 

The polycarbodiimide 34 can be thermally decomposed at 1100 °C under argon to form amorphous Si/C/N solids. 

Trichloroborazene reacts with bis(trimethylsilyl)carbodiimide to form non-oxide B/C7N gels. These gels consist of three-dimensional polymeric networks linked by carbodiimide groups." Similar polycarbodiimide hydrid gels are prepared from tris-s-triazines and bis(trimethylsilyl)carbodiimide." The viscoelastic properties of a gel system based on methyltrichlorosilane and bis(trimethylsilyl)carbodiimide have been reported." ... 

The thermoset polymers are usually obtained in quantitative yields. They are tough and can be molded into clear, tough films. Reaction of the polycarbodiimides with mono amines gives rise to the formation of polyguanidines. Also, conversion into polyureas with water, polythioureas with hydrogen sulfide and poly(O-alkylisoureas) with alcohols is known. ... 

The polycarbodiimides, having isocyanate end groups, are living polymers, because chain scission can occur by a reversible cycloaddition process. 

A negative working photoresist system is obtained using a oligocarbodiimide derived from 2,4-TDI and a phospholene oxide catalyst. m-Tolylisocyanate is used as the chain stopper. To this soluble linear polycarbodiimide a photoamine is added, which generates... 

Polymers with pendant carbodiimide groups 27 are also synthesized from crossUnked polystyrene. In this synthetic route crossUnked polystyrene beads are chloromethylated and converted to the amines. Reaction with isopropyl isocyanate gives the corresponding ureas, which are treated with tosyl chloride and triethylamine to produce the crossUnked polycarbodiimides. This polymer is used in the polymer supported Moffatt oxidation of alcohols into aldehydes or ketones using benzene/DMSO. ... 

Also, reaction of the aminomethyl polystyrene with cyclohexylisocyanate affords a polymer bound urea, which is converted into the carbodiimide using Ph3PBr2. Reaction of the polycarbodiimide with methanol affords an 0-alkylisourea which is used in the 0-alkylation of carboxylic acids. ... 

Polycarbodiimide methacrylates are obtained from the corresponding urea methacrylates. These polymers are utilized in the reaction with waterborne carboxylic acid containing acrylic polymers to produce waterborne polymers with methacrylic functonality." ... 

Linear carbodiimides with pendant carbodiimide groups are obtained by reacting polymeric azides derived from vinyl azide 33 with triphenylphosphine to form poly(phosphine imines) 34, which are subsequently converted to polycarbodiimides 35." ... 

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