Chemistry acrylates

Uses Pigment for water-based paints/coatings, industrial maintenance, marine, wood, plastic, coil, and protective coatings, office furniture finishes, DIY decorative and special effect paints, leather finishes Features High pigment loading forexc. color control compat. with water-based chemistries (acrylic, latex, epoxy, urethane, hybrid systems) contain no VOC s glycol-free... 

By relying on the no-mix surface chemistry, acrylics are susceptible to inconsistent performance due to surface contamination by polymerization inhibitors. 

Chemistry. Acrylic coatings are usually suppUed as dissolved pre-polymerized acrylic chains. The acrylic chemistry does not cure by polymerization and cross-linking as the other coating materials do, but instead hardens gradually as the solvent evaporates. AcryUcs are also available in heat-curable and UV-cured formulations. 

Acetylene-Based Routes. Walter Reppe, the father of modem acetylene chemistry, discovered the reaction of nickel carbonyl with acetylene and water or alcohols to give acryUc acid or esters (75,76). This discovery led to several processes which have been in commercial use. The original Reppe reaction requires a stoichiometric ratio of nickel carbonyl to acetylene. The Rohm and Haas modified or semicatalytic process provides 60—80% of the carbon monoxide from a separate carbon monoxide feed and the remainder from nickel carbonyl (77—78). The reactions for the synthesis of ethyl acrylate are... 

Other Syntheses. Acryhc acid and other unsaturated compounds can also be made by a number of classical elimination reactions. Acrylates have been obtained from the thermal dehydration of hydracryhc acid (3-hydroxypropanoic acid [503-66-2]) (84), from the dehydrohalogenation of 3-halopropionic acid derivatives (85), and from the reduction of dihalopropionates (2). These studies, together with the related characterization and chemical investigations, contributed significantly to the development of commercial organic chemistry. 

A second type of uv curing chemistry is used, employing cationic curing as opposed to free-radical polymerization. This technology uses vinyl ethers and epoxy resins for the oligomers, reactive resins, and monomers. The initiators form Lewis acids upon absorption of the uv energy and the acid causes cationic polymerization. Although this chemistry has improved adhesion and flexibility and offers lower viscosity compared to the typical acrylate system, the cationic chemistry is very sensitive to humidity conditions and amine contamination. Both chemistries are used commercially. 

Group-Transfer Polymerization. Living polymerization of acrylic monomers has been carried out using ketene silyl acetals as initiators. This chemistry can be used to make random, block, or graft copolymers of polar monomers. The following scheme demonstrates the synthesis of a methyl methacrylate—lauryl methacrylate (MMA—LMA) AB block copolymer (38). LMA is CH2=C(CH2)COO(CH2) CH2. 

These are all examples of soluble polymers. Combinations of soluble with insoluble polymers have also been reported. Polychloroprene or chlorosulfonated polyethylene was eombined with core-shell polymer particles to give an adhesive with improved cold impact resistance [33]. The fascinating chemistry of chlorosulfonated polyethylene in acrylic adhesives will be further discussed in the section on initiators. In many cases chlorosulfonated polyethylene is chemically attached to the acrylic matrix. 

Liquid organic rubbers with reactive functionality can be prepared by several methods. End-functional oligomers are preferred. Chains attached to the network at only one end do not contribute as much strength to the network as those attached at both ends [34], Urethane chemistry is a handy route to such molecules. A hydroxy-terminated oligomer (commonly a polyester or a polyether) can be reacted with excess diisocyanate, and then with a hydroxy methacrylate to form a reactive toughener [35]. The methacrylate ends undergo copolymerization with the rest of the acrylic monomers. The resulting adhesive is especially effective on poIy(vinyl chloride) shown in Scheme 2. 

Chemistry St-DVB Acrylic OH-acrylic (ionic) Si02 C j Si02-diol SiO ... 

The facile formation of cyclobutane products is indeed another important contribution of enamine chemistry (302-306). The formation of cyclobutanes has also been found in the closely related reactions of amino acetal derivatives of ketenes with acrylic esters (307). 

Free radical polymerization is a key method used by the polymer industry to produce a wide range of polymers [37]. It is used for the addition polymerization of vinyl monomers including styrene, vinyl acetate, tetrafluoroethylene, methacrylates, acrylates, (meth)acrylonitrile, (meth)acrylamides, etc. in bulk, solution, and aqueous processes. The chemistry is easy to exploit and is tolerant to many functional groups and impurities. 

Sanding is carried out at this stage and, after clean-up, the final colour or top-coat is applied. There is some variation in the resin chemistry used. Alkyds crosslinked with melamine-formaldehyde are widely used for non-metallic pigmentation. Metallics are usually based on acrylics for better durability. The acrylic may be thermoset with melamine-formaldehyde or a thermoplastic lacquer (plasticised copolymer of methyl methacrylate). A thickness of about 50ftm is applied and stoved for 20 min at 130°C (lacquers receive a bake-sand-bake process for a smoother appearance). 

The most important side reactions are disproportionation between the cobalt(ll) complex and the propagating species and/or -elimination of an alkcnc from the cobalt(III) intermediate. Both pathways appear unimportant in the case of acrylate ester polymerizations mediated by ConTMP but are of major importance with methacrylate esters and S. This chemistry, while precluding living polymerization, has led to the development of cobalt complexes for use in catalytic chain transfer (Section 6.2.5). 

Some acrylic acid copolymers are promoted as having a very wide range of functions that permit them to act as calcium phosphate DCAs, barium sulfate antiprecipitants, particulate iron oxides dispersants, and colloidal iron stabilizers. One such popular copolymer is acrylic acid/sulfonic acid (or acrylic acid/ 2-acrylamido-methylpropane sulfonic acid, AA/SA, AA/AMPS). Examples of this chemistry include Acumer 2000 (4,500 MW) 2100 (11,000 MW) Belclene 400, Acrysol QR-1086, TRC -233, and Polycol 43. 

Other chemistries include acrylic acid/sodium 3-allyloxy-2-hydroxypropane sulfonate (AA/COPS), such as Aquatreat AR-540 and its newer derivative, having a higher degree of sulfonation, acrylic acid/non-ionic aromatic and linear sulfonate (AA/NI-AS-LS), Aquatreat AR-550. 

K. B. Wagener and T. A. Davidson, Non-Conjugated and Conjugated Dienes in Acrylic Diene Metathesis (ADMET) Chemistry, in New Macromolecular Architecture and Functions. Proceedings OUMS 95, M. Kamachi and A. Nakamura (Eds.), Springer Verlag, New York, 1996. 

The imidazole ring is a privileged structure in medicinal chemistry since it is found in the core structure of a wide range of pharmaceutically active compounds efficient methods for the preparation of substituted imidazole libraries are therefore of great interest. Recently, a rapid synthetic route to imidazole-4-carboxylic acids using Wang resin was reported by Henkel (Fig. 17) [64]. An excess aliphatic or aromatic amine was added to the commercially available Wang-resin-bound 3-Ar,M-(dimethylamino)isocyano-acrylate, and the mixture was heated in a sealed vial with microwave irradi-... 

Partial oxidation of propylene results in acrolein, H2C=CHCHO, an important intermediate for acrylic acid, H2C=CHCOOH, or in the presence of NH3, in acrylonitrile, H2C=CHCN, the monomer for acrylic fibers. Mixed metal oxides are used as the catalysts [B.C. Gates, Catalytic Chemistry (1992), Wiley, New York]. 

Yokoyama, T. Hiraoko, K. (1979). Hydration and thermal transition of poly(acrylic acid) salts. Polymer Preprints of the American Chemical Society, Division of Polymer Chemistry, 20, 511-13. 

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