Bis- melamine

Pentaerythritol phosphate has an excellent char-forming ability owing to the presence of the pentaerythritol structure. The bis-melamine salt of the bis acid phosphate of pentaerythritol is also available commercially. This is a high melting solid that acts as an intumescent flame-retardant additive for polyolefins. Synergistic combinations with ammonium polyphosphates have also been developed primarily for urethane elastomers. Self-condensation of tris(2-chloroethyl) phosphate produces oligomeric 2-chloroethylphosphate. It has a low volatility, and is useful in resin-impregnated air filters, in flexible urethane foams and in other structural foams.11... 

Reinhoudt et al. have chosen tetraether derivatives of calix[4]arenes fixed in the cone-conformation as such a molecular skeleton.280 Bis-melamine derivatives 135 are easily prepared in a huge diversity (different residues Y, R1, R2) from 1,3-diamino calix[4]arenes by reaction with cyanurchloride, followed by stepwise substitution of the remaining chlorine atoms by ammonia and an aliphatic amine. 

In order to form such an aggregate, the bis-melamine calix[4]arene 135 may assume either a C2-symmetrical (staggered) conformation, in which the residues R1 are in an identical environment, or a Cs-symmetrical (eclipsed) conformation with two different environments for the residues R1. As illustrated in Figure 35, three different diastereomeric boxes may be formed by combination of three molecules of 135 with six molecules 136.281... 

Figure 35. Three possible diastereomeric boxes and their symmetry. The combination of C2- and Cs-symmetrical bis-melamines is not possible in one aggregate.

Figure 37. Chiral bis-melamine derivatives and chiral cyanurates used in self-assembly studies.

It should be mentioned, that larger assemblies consisting of nine calixarenes are available with the calixarene-monocyanurate 139,208a while the double-calixarene 140 forms a double-box with 136 consisting of 15 molecules (3 x 140 and 9 x 136).283 Polymeric aggregates are formed between bis-melamine and bis-cyanurate calix[4]arenes.284 In all these cases, chiral induction still remains to be explored. 

Figure I. Calix[4]arene-based bis-melamines form well-defined assemblies with DEB when mixed in CHCb (1-...

Upon mixing in solution N different assemblies (X)3 (DEB)6 (X = 1, 2, 3,...N Figure 1) under conditions that allow the reversible exchange of the bis-melamine components X, M heteromeric assemblies should theoretically form, in addition to the N homomeric assemblies (Figure 7). The total number of assemblies P (i.e. N + M) present in such a library rapidly increases with increasing N following equation (1) ... 

Uron Resins. In the textile industry, the term uron resin usually refers to the mixture of a minor amount of melamine resin and so-called uron, which in turn is predorninantly N,]S -bis(methoxymethyl)uron [7388-44-5] plus 15—25% methylated urea—formaldehyde resins, a by-product. 

N,]S7-bis(methoxymethyl)uron was first isolated and described in 1936 (41), but was commercialized only in 1960. It is manufactured (42) by the reaction of 4 mol of formaldehyde with 1 mol of urea at 60°C under highly alkaline conditions to form tetramethylolurea [2787-01-1]. After concentration under reduced pressure to remove water, excess methanol is charged and the reaction continued under acidic conditions at ambient temperatures to close the ring and methylate the hydroxymethyl groups. After filtration to remove the precipitated salts, the methanolic solution is concentrated to recover excess methanol. The product (75—85% pure) is then mixed with a methylated melamine—formaldehyde resin to reduce fabric strength losses in the presence of chlorine, and diluted with water to 50—75% soHds. Uron resins do not find significant use today due to the greater amounts of formaldehyde released from fabric treated with these resins. 

Flame retardants (qv) are incorporated into the formulations in amounts necessary to satisfy existing requirements. Reactive-type diols, such as A/ A/-bis(2-hydroxyethyl)aminomethylphosphonate (Fyrol 6), are preferred, but nonreactive phosphates (Fyrol CEF, Fyrol PCF) are also used. Often, the necessary results are achieved using mineral fillers, such as alumina trihydrate or melamine. Melamine melts away from the flame and forms both a nonflammable gaseous environment and a molten barrier that helps to isolate the combustible polyurethane foam from the flame. Alumina trihydrate releases water of hydration to cool the flame, forming a noncombustible inorganic protective char at the flame front. Flame-resistant upholstery fabric or liners are also used (27). 

Template condensation reactions of the nickel(II) complex of 3,7-bis(2-aminoethyl)-l,3,5,7-tetraazabicyclo[3.3.1]nonane with formaldehyde and the appropriate primary diamines such as ethylenediamine, 1,4-butanediamine, and p-xylenediamine yield dinickel(II) complexes of bis-heptaazamacrocyclic ligands (716)-(718). Similarly, the dinuclear Ni11 complexes (719) and (720) were prepared by using [Ni(2,3,2-tet)](C104)2, formaldehyde, and NH2—(CH2)ra—NH2 ( = 2, 3, 4, 5, 6, 10) or melamine, respectively. 

All wet strength agents are bi- or multi-functional molecules with the capability to cross-link with each other or with cellulose. The choice of chemistry depends to a large extent on pH. In acid systems, the main wet strength agents are urea-formaldehyde (U/F) and melamine-formaldehyde (M/F) resins, whereas in neutral and alkaline systems polyamine-polyamide-epichlorohydrin resins are more effective. However, these are not the only systems in use, and a summary of these and other available methods is provided in Figure 7.22. 

Unlike the urea- and melamine-formaldehyde resins, these wet strength agents are suitable for both neutral and alkaline pH. They are prepared by condensation of a dicarboxylic acid and bis (2-aminoethyl) amine, the free amino group is then alkylated with epichlorohydrin to give an aminochlorohydrin which exists in equilibrium with a 3-hydroxyazetidinium group (Figure 7.28). 

These are usually formed from bi-functional and tri-functional monomers and eontaln strong covalent bonds between various linear polymer chains, e.g. bakellte, melamine, etc. These polymers are depicted as follows ... 

Biogenic amines, such as histamine [131], adenine [132], dopamine [133] and melamine [134], have been determined using chemosensors combining MIP recognition and PM transduction at QCM. Electronically conducting MIPs have been used in these chemosensors as recognition materials. Initially, functional electroactive bis(bithiophene)methane monomers, substituted either with the benzo-18-crown-6 or 3,4-dihydroxyphenyl, or dioxaborinane moiety, were allowed to form complexes, in ACN solutions, with these amines as templates. Subsequently, these complexes were oxidatively electropolymerized under potentiodynamic conditions. The resulting MIP films deposited onto electrodes of quartz resonators were washed with aqueous base solutions to extract the templates. 

Fig. 4 Resonant frequency changes with time due to repetitive FIA melamine injections, for the MIP-QCM chemosensor. Melamine concentration is indicated with number at each curve. Inset shows FIA calibration plots for (1) melamine and its interfering compounds, such as (2) ammeline, (3) cyanuric acid, and (4) cyromazine. Volume of the injected sample solution was 100 pL. The flow rate of the 1 mM FIC1 carrier solution was 35 pL min-1. The MIP film was prepared by electropolymerization of 0.3 mM bis(2,2 -bithienyl)-benzo-[18-crown-6]methane functional monomer and 0.3 mM 3,3 -bis[2,2 -bis(2,2 -bithiophene-5-yl)]thianaphthene cross-linking monomer, in the presence of 0.1 mM melamine, in the trihexyl(tetradecyl)phosphonium tris(pentafluor-oethy 1)-trifluorophosphate ionic liquid ACN (1 1 v/v) solution, which was 0.9 mM in trifluoroacetic acid (pH = 3.0). The melamine template was extracted from the MIP film with 0.01 M NaOH before the determinations (adapted from [134])...

The use of polyols such as pentaerythritol, mannitol, or sorbitol as classical char formers in intumescent formulations for thermoplastics is associated with migration and water solubility problems. Moreover, these additives are often not compatible with the polymeric matrix and the mechanical properties of the formulations are then very poor. Those problems can be solved (at least partially) by the synthesis of additives that concentrate the three intumescent FR elements in one material, as suggested by the pioneering work of Halpern.29 b-MAP (4) (melamine salt of 3,9-dihydroxy-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5,5]-undecane-3,9-dioxide) and Melabis (5) (melamine salt of bis(l-oxo-2,6,7-trioxa-l-phosphabicyclo[2.2.2]octan-4-ylmethanol)phosphate) were synthesized from pentaerythritol (2), melamine (3), and phosphoryl trichloride (1) (Figure 6.4). They were found to be more effective to fire retard PP than standard halogen-antimony FR. 

Zinc borate in PC/ABS and polyamide—when zinc borate is used in conjunction with bisphenol-A-bis-diphenyl phosphate in PC/ABS, it was reported that borophosphate and zinc phosphate were generated during polymer combustion.111 The formation of these materials could be beneficial for passing the more stringent Are tests, such as UL-95 5 V. When Firebrake 500 is used in conjunction with aluminum diethylphosphinate and melamine polyphosphate in polyamide, Schartel et al. reported the formation of boron aluminum phosphate in the condensed phase.112... 

Theory This method confirms the presence of TMS derivatives of cyromazine and melamine residues extracted from poultry and red meat tissues from the determinative method. The TMS derivatives are formed by heating the residue with BSTFA (N,0-bis (trimethylsilyl) trifluoroacetamide) in the presence of TMCS (trimethylchlorosilane). 

The complex between melamine and cyanuric acid (1 1) was reported in the literature in the late 1970s, but it was only in the early 1990s that the contributions from Whitesides and the concept of self-assembly popularized these systems [45]. Whitesides and co-workers reported the formation of tapes (Fig. 11.11), crinkled tapes and cyclic hexamers (rosettes) formed between barbituric acid and N,N -bis(p-substituted phenyl)melamine [46], In this they effectively blocked one face of melamine and, by manipulating substituents at the para position, different structures were obtained. Whiteside s putative suggestion that melamine/cyanuric acid formed an extended array (Fig. 11.12) was confirmed recently by Rao et al. with the crystal structure [47]. Hamilton and coworkers reported the crystal structure of a 5-substituted isophthalic acid derivative, which forms a cyclic aggregate held together with six pairs of hydrogen bonds, which in a way resembles the trimesic acid (Fig. 11.13) [48]. 

This approach mimics familiar biological self-assembly phenomena such as protein folding [ 192], protein aggregation [ 192] and nucleotide pairing [ 188]. It incorporates features described in each of the above strategies (i.e., I—III), to give specialized nanoscopic structures, that can be precisely designed, usually with excellent control over CMDPs. Recent examples include so called structure directed synthesis by Stoddart [3a] (see Chapter 1 of this book) to produce toroidal bis-bipyridinium cyclophanes that are reminiscent of a molecular abacus , melamine-cyanuric acid lattices by Whitesides [193] and unique helical structures based on coordination of bipyridyl units to copper (II) ions by Lehn [194],... 

The chemical name of this reagent is l,3-bis(hydroxymethyl)-4,5-dihydroxy-imidazolidinone-2 but it is usually called DMDHEU or the glyoxal reactant because it is prepared from glyoxal, urea, and formaldehyde. Other methylolamide agents that have been used for producing wrinkle resistance in cotton include the aforementioned urea formaldehyde, dimethylolurea, dimethylolethyleneurea, and formaldehyde adducts of melamines (triazines), acetylenediurea, propyleneurea, uron, triazones, and alkyl carbamates. Reactions between methylolamides and cellulose occur in the presence of acid (or Lewis acid) catalysts and are very fast at elevated temperatures—sufficiently so that they are adaptable to the requirements of rapid, commercial processing of cotton fabrics. 

Polyacetal resin compositions having excellent wear resistance were prepared by Kim [4], These resins consisted of polyoxymethylene polymer, ethylene vinylacetate, melamine, triethyleneglycol-bis-3-(3-t-butyl-4-hydroxy-5-methylphenyl)-propionate, and hydroxyl pentaerythritol fatty acid ester. 

Amines, (see also Alkanolamines, Aminoacids, Aminoalcohols, Diamines, Melamine, Methylene-bi.s-amines), /2. 170, 200, 236... 

Figure 13 Single crystal X-ray structures of two polymorphic forms of the 1 1 cocrystal between diethylbarbital and bis-(p-bromophenyl)melamine...

HEXAKIS(HYDROXYMETHYL)MELAMINE HEXAKIS-(HYDROXYMETHYL)- ,3,5-TRIAZINE-2,4,6-TRIAMINE HEXAMETHYLOLMELAMIN (CZECH) HEXAMETH-YLOLMELAMINE RESLOOM M 75 (1,3,5-TRIAZINE-2,4,6-TRIYLTRINITRILO)HEXAKIS METHANOL (s-TRLAZINE-2,4,6-TRIYLTRINITRlLO)HEXAMETHANOL 2,4,6-TRIS(BIS(HYDROXYMETHYL)AMINO)-s-TRlAZ-... 

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