| 摘要 |
A monocellular thermoplastic, resinous polymeric particle has a generally spherical shape and has encapsulated therein a discrete portion of a non-polar volatile liquid raising agent which becomes gaseous at a temperature below the softening point of the polymer. The particles are usually prepared by providing an aqueous dispersion of (a) organic monomeric materials suitable for polymerization to a thermoplastic resinous material, (b) a liquid blowing agent which exerts little solvent action on the resulting polymer, (c) a dispersion stabilizing material which is utilized to maintain the dispersion and subsequently polymerizing the monomeric material to solid spherical particles having a quantity of the liquid blowing agent encapsulated therein. Organic monomeric materials specified are alkenyl aromatic monomers such as styrene and nuclear substituted styrenes, acrylate monomers both alone and in combination with alkenyl aromatic monomers. Copolymers of vinyl chloride and vinylidene chloride, acrylonitrile with halogenated vinyl compounds such as vinyl chloride or bromide; and vinyl esters can also be used. Copolymerizable acids, e.g. acrylic acid, itaconic acid, fumaric acid and vinyl benzoic acid are often advantageously added. Blowing agents are hydrocarbons or halogenated hydrocarbons. Suspending agents named are methyl cellulose, gum agar, hydroxypropyl methyl cellulose, carboxymethyl cellulose, colloidal silica and colloidal clays. Suitable catalysts include peroxide compounds and high energy ionizing radiation. Beads produced may be either symmetrical or asymmetrical: the former are better prepared by including a copolymerizable polar system in the monomer mixture. The beads may be used in making porous epoxy resins, expandable coatings, laminates, decorative patterns and heat setting adhesives.ALSO:The invention comprises foamable and foamed coating compositions containing unexpanded or expanded monocellular thermoplastic resinous polymeric particles. The unexpanded particles have encapsulated therein a portion of a non-polar volatile blowing agent. The polymeric particles are formed from olefinically unsaturated monomers e.g., alkonyl aromatics, acrylates, vinyl compounds. The coating compositions containing unexpanded particles also comprise a flexible, thermoplastic resinous binder, heating the dry coating causes the particles to expand and form a foamed layer. The coatings containing expanded particles are made by mixing the prefoamed particles with a suitable binder; the type of binder depends on the required coating, e.g. temporary water-soluble coatings may comprise a water-soluble polymeric material such as a cellulose derivative or agar-agar, and permanent coatings may comprise a thermosetting material such as a phenol-formaldehyde resin. The compositions may be applied to a variety of substrates to give smooth or textured finishes. Examples relate to coating (SS) a copper pipe, (56) band paper, (57, 58) a paper cup and (61) a lacquered wooden panel. |
