Acrylate resins cross-linking

Acrylic resins (Perspex, PMMA, Paraloid) -1930 Varnishes, adhesives, glazing, sculptures, paint media Sensitivity to sunlight. Methacrylates are subjected to bond cleavage. Acrylates undergo cross linking reactions... 

The traditional cross-linking technologies utilized in the coatings market range from hydroxyl functional binders (acrylics or polyesters) cross-linked with melamines (IK) or isocyanates (2K) to drying oils that cure through oxidation of unsaturation in the backbone, to epoxy resins cross-linked with amino resins (amido amines, amines, etc.). 

Epoxy-amino and epoxyacrylate High molecular weight epoxy resins cross-linked with amino or acrylate resins Water reducible for reduced environmental impact Good Limited Universal lacquer for beer and beverage cans (water reducible) Side seam stripes Some food systems... 

The variability in the pyrolysis profiles of the different classes of coatings is self-evident. The interpretation of the composition revealed is as follows The acrylic lacquer (General Motors) is a methyl methacrylate/methacrylic acid copolymer plasticized with dibutyl-, butyl cyclohexyl-, and butyl benzyl phthalates. The acrylic enamel (Ford) is a styrene/ethylhexyl acrylale/methyl methacrylate terpolymer. The alkyd enamel (Honda) pyrolysis profile indicates that the paint resin is an orthoph-thaUc alkyd containing a butylated-amino resin cross-linking component. 

It can be concluded that the beverage can coating is a methyl melhacrylate/eth-ylhexyl acrylate copolymer modified polyester. The polyester is an adipic acid-modified neopentyl glycol iso-/orthophthalic acid type. The electrical appliance coating is a butylated amino resin cross-linked pentaerythritol-orlhophthalic thermosetting alkyd enamel. 

Listed below are the major European resins manufacturers who offer hydroxy functional acrylics for cross linking with isocyanate adducts. 

Esters. Most acryhc acid is used in the form of its methyl, ethyl, and butyl esters. Specialty monomeric esters with a hydroxyl, amino, or other functional group are used to provide adhesion, latent cross-linking capabihty, or different solubihty characteristics. The principal routes to esters are direct esterification with alcohols in the presence of a strong acid catalyst such as sulfuric acid, a soluble sulfonic acid, or sulfonic acid resins addition to alkylene oxides to give hydroxyalkyl acryhc esters and addition to the double bond of olefins in the presence of strong acid catalyst (19,20) to give ethyl or secondary alkyl acrylates. 

The thermoplastic or thermoset nature of the resin in the colorant—resin matrix is also important. For thermoplastics, the polymerisation reaction is completed, the materials are processed at or close to their melting points, and scrap may be reground and remolded, eg, polyethylene, propjiene, poly(vinyl chloride), acetal resins (qv), acryhcs, ABS, nylons, ceUulosics, and polystyrene (see Olefin polymers Vinyl polymers Acrylic ester polymers Polyamides Cellulose ESTERS Styrene polymers). In the case of thermoset resins, the chemical reaction is only partially complete when the colorants are added and is concluded when the resin is molded. The result is a nonmeltable cross-linked resin that caimot be reworked, eg, epoxy resins (qv), urea—formaldehyde, melamine—formaldehyde, phenoHcs, and thermoset polyesters (qv) (see Amino resins and plastics Phenolic resins). 

Resin bead polymer composition Either acrylic resins or, more generally, styrene (vinylbenzene, VB) are cross-linked with typically 4 to 20% divinylbenzene (DVB) in a copolymer network or matrix. 

NR, styrene-butadiene mbber (SBR), polybutadiene rubber, nitrile mbber, acrylic copolymer, ethylene-vinyl acetate (EVA) copolymer, and A-B-A type block copolymer with conjugated dienes have been used to prepare pressure-sensitive adhesives by EB radiation [116-126]. It is not necessary to heat up the sample to join the elastomeric joints. This has only been possible due to cross-linking procedure by EB irradiation [127]. Polyfunctional acrylates, tackifier resin, and other additives have also been used to improve adhesive properties. Sasaki et al. [128] have studied the EB radiation-curable pressure-sensitive adhesives from dimer acid-based polyester urethane diacrylate with various methacrylate monomers. Acrylamide has been polymerized in the intercalation space of montmorillonite using an EB. The polymerization condition has been studied using a statistical method. The product shows a good water adsorption and retention capacity [129]. 

The process described is referred to as ion-exclusion as discussed by Asher and Simpson 9. The resins used are normal and the non-ionic molecules are assumed to be small enough to enter the pores. When large non-ionic molecules are involved, an alternative process called ion-retardation may be used, as discussed by Hatch et al. W]. This requires a special resin of an amphoteric type known as a snake cage poly electrolyte. The polyelectrolyte consists of a cross-linked polymer physically entrapping a tangle of linear polymers. For example, an anion exchange resin which is soaked in acrylic acid becomes entrapped when the acrylic acid is polymerised. The intricacy of the interweaving is such that counter-ions cannot be easily displaced by other counter-ions. On the other hand, ionic mobility within the resin maintains the electro-neutrality. The ionic molecule as a... 

Figure 13. Tan 5 as function of temperature for cross-linked films of three different acrylate resins with either hydroxyl (HI 3), benzoate (HI 2), or propionate (H11) terminal groups.

Under UV-laser irradiation, photosensitive multifunctional acrylate resins become rapidly cross-linked and completely insoluble. The extent of the reaction was followed continuously by both UV and IR spectroscopy in order to evaluate the rate and quantum yield of the laser-induced polymerization of these photoresist systems. Two basic types of lasers emitting in the UV range were employed, either a continuous wave (C.W.) argon-ion laser, or a pulsed nitrogen laser. 

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