Acid functional acrylic resin

The alternative route of preparing water reducible resins using emulsion polymerisation of an acid functional acrylic resin has already been considered under emulsion example 7 - preparation of a water soluble acrylic copolymer. 

Electro deposition systems (which are considered later) are the only main exception to acid functional acrylic resins, where cathodic deposition which is increasingly favoured requires amine functional acrylics. 

Epoxy resins have been made water reducible by the use of acid functional acrylic resins. They find widespread application as internal lacquers for DWI beer and beverage cans (see Chapter 7- Waterborne Applications). They are often made in solution in butyl glycol and butanol and are then neutralised and dispersed into water under agitation. A full discussion of this technology and all of its variants is given in the Epoxy volume of this series of books. A brief outline of some of the chemistry will be given here. 

Not every molecule of epoxy present during the polymerisation is modified by reaction with the acrylic, as shown in Figure 2-22. Some epoxy is left unmodified and some acid functional acrylic resin is formed, which is not grafted onto an epoxy backbone. The molecules of epoxy which are grafted with acrylic perform an important function as they contain both hydrophobic and hydrophilic parts on them, which when neutralised with amine, give them the classical features of an emulsion stabiliser. They can be drawn with the ionised carboxylic acid groups on pendant side chains attached to the main epoxy backbone as shown in Figure 2-23. 

Vegetable oil-based poly(ester amide) resin has also been synthesised at a lower temperature in the absence of an organic solvent through a condensation polymerisation reaction of V,V-bis(2-hydroxyethyl) oil fatty amide and phthalic anhydride at a temperature lower than the onset of their melting points. By-products such as water were removed by a vacuum technique. Poly(ester amide) resins may also be prepared using an acid functional acrylic copolymer (butyl methacrylate and maleic anhydride) and hydroxy ethyl fatty amide of dehydrated castor oil in a 3 1 molar ratio. 

Acid functionalized epoxy resins are generally prepared by esterification of epoxy resin with an excess of acid equivalents, or by grafting of acrylic copolymers containing methacrylic acid or acrylic acid onto the epoxy backbone. They are generally cured by an aminoplast at elevated temperature. 

While selecting a particular type of functional acrylic resin, the paint properties are also affected by the nature of the monomer used to impart functionality to the resin. For example, in the case of acid-functional acrylics, itaconic acid has been shown to be preferable to acrylic acid. This is due to the fact that the former imparts better low-bake humidity resistance and adhesion. This has been assigned to the better distribution of itaconic acid units in the copolymer due to their low solubility in most organic solvents as compared to acrylic and methacrylic acid. 

Direct, acid catalyzed esterification of acryhc acid is the main route for the manufacture of higher alkyl esters. The most important higher alkyl acrylate is 2-ethyIhexyi acrylate prepared from the available 0x0 alcohol 2-ethyl-1-hexanol (see Alcohols, higher aliphatic). The most common catalysts are sulfuric or toluenesulfonic acid and sulfonic acid functional cation-exchange resins. Solvents are used as entraining agents for the removal of water of reaction. The product is washed with base to remove unreacted acryhc acid and catalyst and then purified by distillation. The esters are obtained in 80—90% yield and in exceUent purity. 

The acrylic weak base resins are synthesized from copolymers similar to those used for the manufacture of weak acid cation-exchange resins. For example, under appropriate temperature and pressure conditions, a weak acid resin reacts with a polyfunctional amine, such as dimethylaminopropylamine [109-55-7] (7) to give a weak base resin with a tertiary amine functionality. 

Thermosetting acrylics can be produced from a variety of monomers in varying percentage compositions the systems utilize a variety of cross-linking mechanisms (Table IV). A typical thermosetting acrylic can be prepared from 15-80% styrene, 15-18% alkyl acrylate, and 5-10% acrylic acid (27). Acrylic acid provides the functionality for cross-linking with epoxy resins. 

Comparing the phase diagrams of AC 540 modified DGEBA epoxy resin and hardener HHPA showed that the oxidized homopolymer with an acid functionality of 2.0 (AC 5120) was more miscible in epoxy resin and the RVP grafted AC 5120 had comparable miscibility as that of AC 5120. Similarly, ethylene acrylic acid-vinyl acetate terpolymer (AC 1450) was less miscible in epoxy resin compared to AC 5120 due to less chemical interaction with epoxy resin. Thus, the miscibility of the blends was reduced by the addition of HHPA to various blend systems. 

In chemical development, the matrix resin of the resist system dissolves in the developer through a chemical reaction. Examples of resists that use chemical development include positive resists composed of novolac resins and DNQs, as well as positive chemical amplification resists based on phenolic, acrylate, and ali-cyclic polymers. These resists are developed with a 0.26-N aqueous solution of tetramethylammonium hydroxide. The exposed resins with phenolic and acidic functional groups dissolve in the developer via the chemical reactions... 

Chemical reactions with alkyd resins can take place via their hydroxyl or carboxyl groups as well as via the double bonds of the unsaturated fatty acids. Isocyanates, epoxy resins, or colophony, for example, may be reacted with the hydroxyl groups. The carboxyl groups can be reacted with polyamidoamines (reaction products formed from dimerized linoleic acid and ethylenediamine) to form thixotropic resins, or can react with hydroxy-functional silicone precondensates. The double bonds of the unsaturated fatty acids permit copolymerization with vinyl compounds [e.g., styrene or (meth)acrylic acid derivatives]. 

Chem. Descrip. Acrylic resin (60%) in butyl acetate Uses Acrylic for air-drying and forced-drying two-pack coatings for industrial lacquers, car repair coatings Features Hydroxy-functional crosslinkable with polyisocyanales Prqretties Hazen < 50 color dilutable with toluene, xylene, acetone, MEK, MIBK, methot propyl acetate, ethyl acetate, butyl acetate dens. = 1.01 g/cm (20 C) dynamic vise. 1150-2200 mPa s acid no. 5-10 hyd. no. = 90 flash pt. = 25 C 58-62% NV Storage 12 mos min. shelf life when stored in original containers below 25 C... 

Thermosetting acrylic resins are used widely in surface coatings. Both acrylic and methacrylic esters are utilized and the term is applied to both of them. Often, such resins are terpolymers or even tetrapolymers, where each monomer is chosen for a special function. One is selected for rigidity, surface hardness, and scratch resistance another for ability to flexibilize the film, and the third for crosslinking it. In addition, not all comonomers are necessarily acrylic or methacrylic esters or acids. For instance, among the monomers that may be chosen for rigidity may be methyl methacrylate. On the other hand, it may be styrene instead, or vinyl toluene, etc. The same is true of the other components. Table 5.12 illustrates some common components that can be found in thermoset acrylic resins. 

Shell Oil Co. EB/UV radiation cure of composition comprising a monoalkenyl arene/conjugated diene block copolymer, tackifying resin, and a di-tetra functional acrylate or methacrylate selected from the group consisting of acrylic and methacrylic acid esters of polyols. Improved high-temperature properties and solvent resistance. PSA properties,... 

Following the synthetic concept described for carboxylic acid functionalized resins [2], dipyridyl amide functionalized resins have been prepared[3]. Synthesis of the starting monomer was achieved by reaction of cyclopentadiene with acrylic acid chloride at 0°C. A... 

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