Acrylic resins

The range of products [unclear: g] by the acrylic monomers building blocks is very [unclear: la] They give:

(a) Resins in solution appliance and automet uses.

(b) Resins in an emuls form for decorative [unclear: pa] and

(c) 100% reactive material the transparent sheet type of product.

The products available this group arc widely [unclear: u]. commercially because of [unclear: th] excellent properties of cher cal and weather resistar strength and clarity.

The acrylic resins are po mers of acrylic acid, [unclear: simplest] acrylate used methyl acrylate. Other [unclear: or] monomers used to fo polymers are ethyl acryli butyl acrylate, 2-ethyl he acrylate. methyl methacryl and many more.

The activity in the acry field is very intense in N Zealand and overseas. Be work is being undertaken [unclear: in] building up polymers new monomers attempting overcome defects in the [unclear: p] ticular system under [unclear: revi] The quality of surface [unclear: co ings] in New Zealand is [unclear: high] by world standards, a consequently the struggle constantly improve is [unclear: tinuous].

Taking each type in turn (a) Solution acrylics: [unclear: T] polymer resins are fori from the monomers select by a reaction mechant known as a peroxide initia free radicle polymerisati This means that the polyn is built up in solution, such xylene, and methyl [unclear: ketone], by each building [unclear: adding] on head to tall

page 13

ad to head, until the [unclear: quired] molecular weight is [unclear: ached]. Most Industrially [unclear: ul] coating resins are pre-red from several different [unclear: omer] types conferring [unclear: eir] own special properties ese are copolymrr resins, producing copolymer resins [unclear: e] resin formulating chemist [unclear: ust] be aware of The com-[unclear: cations] and deviations that [unclear: n] aride during the poly-[unclear: erisation,] such as the differnt rates that one monomer ill enter the polymer, re[unclear: ting] in an uneven monomer stribution.

There are two types of lution acrylic:

(i) Acrylic lacquers

(ii) Acrylic enamels

Both types are produced id used in New Zealand. The [unclear: sic] development was done erseas and not a great deal [unclear: s] been done in modifying, they are tricky compounds work with. Most of the [unclear: difications] done here are way of the other additives the final paint such as [unclear: vent] blends.

The lacquer type can be [unclear: rmulat] as a typical [unclear: ample] from polymer built from methacrylic acid and ethyl methacrylate (a hard, ugh resin). The lacquers in be modified with cellulose [unclear: etate-butyrate] to aid, for camole, adhesion, plus other ds to film forming such as plasticiser, eg. butyl benzyl [unclear: thalate].

The acrylic enamels or [unclear: ermosetting] acrylics are reacing the acrylic lacquers ad conventional enamels in [unclear: e] automotive industry and ppliance fields. They are ard, durable, resistant to aining and to grease and ave excellent colour retenon and high gloss. Their igher cost is compensated or by their superior performance. The polymer is based [unclear: n] copolymers of methacrylic cid or acrylamide with ethyl crylate.

To form the enamel, after igmentation melamine form-ldehyde resin is added and [unclear: he] film baked. Cross linking etween the two resins occurs, iving a film with the out-landing properties detailed bove. Plasticising alkyd esins are also included to romote adhesion.

(b) Emulsion acrylics: This roup comprises acrylic poly-lers and copolymers in susension in an aqueous phase.

These suspension polymers re used to produce paints lor nerior and exterior brush-is "latex" types.

The basic units used in the olymerisation are methyl crylate, ethyl acrylate. 2-thyl hexyl acrylate. metharylic acid, and vinyl acetate.

It is in this field that [unclear: ctivity] is greatest. The [unclear: echanism] of polymerisation by a similar free radicle [unclear: ystem]. The basic units are mulsified in situ and the [unclear: onomers] enter the emulsiled micelle to give a polymer of the required molecular eight. The copolymer systems with vinyl acetate coupled with the ncrylates, and the pure acrylics, are both manulactured in New Zealand by this method, These vehicles form the basis of the acrylic paints of today.

The field is very wide, the chemistry of which makes an interesting study.

(c) 100 per cent reactive material for the plasties Industry: Everybody is familiar with the transparent sheeting type of material and its uses. It is formed by similar materials to those used in the acrylic lacquer, i.e. methyl methacrylate. The sheets of plastic are made by filling a space between two sheets of armour-tough plans, with the methyl methacrylate. and placing in an oven and heating until the monomer becomes nolymerised to the nolymethyl metharylate The finished sheeting is' imported ready to use.