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Alkylated amino resins

Paraformaldehyde [30525-89-4] is a mixture of polyoxymethylene glycols, H0(CH20) H, with n from 8 to as much as 100. It is commercially available as a powder (95%) and as flake (91%). The remainder is a mixture of water and methanol. Paraformaldehyde is an unstable polymer that easily regenerates formaldehyde in solution. Under alkaline conditions, the chains depolymerize from the ends, whereas in acid solution the chains are randomly cleaved (17). Paraformaldehyde is often used when the presence of a large amount of water should be avoided as in the preparation of alkylated amino resins for coatings. Formaldehyde may also exist in the form of the cycHc trimer trioxane [110-88-3]. This is a fairly stable compound that does not easily release formaldehyde, hence it is not used as a source of formaldehyde for making amino resins. [Pg.323]

On curing, amino resins not only react with the nucleophilic sites (hydroxyl, carboxyl, amide) on the other film formers in the formulation, but also self-condense to some extent. Highly alkylated amino resins have less tendency to self-condense (33,34) and are therefore effective cross-linking agents, but may require the addition of a strong acid catalyst to obtain acceptable cure even at bake temperatures of 120—177°C. [Pg.328]

In general, conditions for the first part of the reaction are selected to favor the formation of methylol compounds. After addition of the reactants, the conditions may be adjusted to control the polymerization. The reaction may be stopped to give a stable symp. This could be an adhesive or laminating resin and might be blended with filler to make a molding compound (see also Laminates Reinforced PLASTICS). It might also be an intermediate for the manufacture of a more complicated product, such as an alkylated amino resin, for use with other polymers in coatings. [Pg.325]

Properties. Alkylated amino resins can be classified into two general classes (1) polymeric, partially alkylated resins which have a lower solids content and (2) the more monomeric, fully and partially alkylated products which have a higher solids content. [Pg.81]

Typical polymeric, partially alkylated amino resins are butylated or isobutylated condensates with an average degree of polymerization between 3 and 8 and a combined formaldehyde content of 1.4-1.8 per amino group [2.147]-[2.149]. The hydroxymethyl (methylol) groups are partially alkylated (degree of alkylation 40-80%). [Pg.81]

Fully alkylated amino resins require strong acid catalysis for fast and/or low-temperature cross-linking. Their catalysis mechanism is different from that of partially alkylated resins which respond to weak acid catalysts or general acid catalysis. A fully alkylated melamine resin catalyzed by a strong acid catalyst is a faster curing (cross-linking) agent than a partially butylated amino resin. [Pg.81]

The catalysts which are predominately used are p-toluenesulfonic acid, dodecyl-benzenesulfonic acid, dinonylnaphthalenedisulfonic acid, and their amine salts [2.152]. Compared to partially alkylated amino resins, fully alkylated resins have a lower tendency to undergo self-condensation and produce films which are hard and still more flexible. [Pg.82]

Monomeric partially and fully alkylated amino resins are prepared in two separate reaction steps. Hydroxymethylation is carried out under basic conditions to minimize self-condensation of the amino resin. The pH is then lowered by addition of a mineral acid and alkylation with methanol is carried out. To obtain monomeric amino resins, an excess of formaldehyde has to be used to assure a high level of hydroxymethylation and a low level of residual amide groups that would otherwise lead to polymer formation during the alkylation step. Since water removal by azeotropic distillation is not possible with methanol, a large excess of alcohol is required to achieve complete alkylation. After completion of alkylation the resin solution is neutralized water, alcohol, and residual formaldehyde are removed by vacuum distillation. The salt formed during neutralization is removed by filtration [2.154]. [Pg.82]

The fully alkylated amino resin is characterized by its degree of alkylation and polymerization, and its residual hydroxymethyl and amino content, all of which can significantly affect physical and chemical properties. [Pg.82]

Some other polymers such as aromatic and aliphatic hydrocarbon resins, high MW alkylated amino resins, polyvinyl ethers and polyvinyl butyrals are utilized for the purpose of enhancing leveling. They are not marketed as leveling agents but are used in specialty products. [Pg.252]

The replacement of the hydrogen of the methylo1 compound with an alkyl group renders the compound much more soluble in organic solvents and more stable. This reaction is also cataly2ed by acids and usually carried out in the presence of considerable excess alcohol to suppress the competing self-condensation reaction. After neutrali2ation of the acid catalyst, the excess alcohol may be stripped or left as a solvent for the amino resin. [Pg.324]

A wide selection of amino resin compositions is commercially available. They are all alkylated to some extent in order to provide compatibiUty with the other film formers, and formulation stabiUty. They vary not only in the type of amine (melamine, urea, ben2oguanamine, and glycolutil) used, but also in the concentration of combined formaldehyde, and the type and concentration of alkylation alcohol (/ -butanol, isobutyl alcohol, methanol). [Pg.328]

Fmoc-Rink-Nle-pMeBHA-resin (1 g, 0.55 mmol g ) was swollen for 1.5 h in NMP in a reaction vessel equipped with a sintered glass bottom, and placed on a shaker. The Fmoc group was removed with 20% piperidine in NMP (8mL, 2 x 15 min) and after washing with NMP (8mL, 5 x 2 min), the Fmoc removal was monitored by the ninhydrin Kaiser test. Coupling of building blocks such as iV -Fmoc-/Va>-carb-oxyalkyl(OAl)Xaa-OH or /V -Fmoc-/V" -aminoalkyl(Aloc)Xaa-OH, or N -alkylated amino acids such as... [Pg.503]

Peptides that contain amidated Pro or other Af-alkyl amino acids at their C-terminus are less prone to formation of piperazine-2,5-diones in SPPS. Apparently, the use of a benzhy-drylamine-type resin exerts enough steric hindrance to slow down piperazine-2,5-dione formation. In some cases, e.g., the synthesis of peptide amides that have -D-Pro-Pro-NH2 or -Aib-Pro-NH2 sequences, the use of the 4-benzyloxy-4 -4"-dimethoxytrityl amine resin (BDMTA resin, Scheme 34) 187 is recommended. [Pg.251]

To overcome the chain fragmentation of sensitive peptides that contain /V-alkyl amino acids caused by acids as described vide supra, the following measures are recommended (1) in solution synthesis the exploitation of protecting groups removed by acids should be minimized (e.g., apply Fmoc chemistry, use acid-labile side-chain protection as little as possible) (2) if the peptides must be subjected to acid use low temperatures (—20 °C) for the shortest time possible (monitor the reaction by HPLC ) (3) in SPPS if the peptide does not contain functionalized side chains, prepare the peptide by Fmoc chemistry on Trt resin and remove the peptide from the resin with HFIP (see Section 10.1.1.2.2). If the peptides have functionalized side chains see point (1). [Pg.259]

Successive Amide Alkylation of Resin-Bound Amino Acids or Peptides ""]... [Pg.849]

A variety of heterocyclic compounds have been derived from the condensation of aldehydes with a-amino acids. Imines 1 (Fig. 3) are often used as intermediates in organic synthesis and are the starting point for chemical reactions such as cycloadditions, condensation reactions, and nucleophilic additions. The formation of imines via condensation of amines with aldehydes was first adopted for the reductive alkylation of resin-bound amino acids [29-31]. Imines have now been used as synthetic intermediates in the generation of a range of heterocyclic combinatorial libraries. [Pg.622]


See other pages where Alkylated amino resins is mentioned: [Pg.81]    [Pg.81]    [Pg.84]    [Pg.926]    [Pg.81]    [Pg.81]    [Pg.84]    [Pg.926]    [Pg.328]    [Pg.203]    [Pg.187]    [Pg.433]    [Pg.188]    [Pg.104]    [Pg.55]    [Pg.504]    [Pg.203]    [Pg.221]    [Pg.243]    [Pg.251]    [Pg.251]    [Pg.252]    [Pg.257]    [Pg.414]    [Pg.115]    [Pg.636]    [Pg.328]    [Pg.105]   


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