Imperial Chemical Industries Limited

Julian A Waters

Christopher Henry Such

Susan M Horley

George E Abboud

Brian J Roulstone

Frederick A Waite

The tendency for hard and irregular particles of titanium dioxide pigment to adversely affect the sheen and coin mar resistance of a dried coating into which they have been incorporated is reduced by modifying the particles with polymer particles which have been preformed and are therefore of a more pre-determinable shape and size. The polymer particles are chemically bonded to a polymeric water-soluble compound containing moieties which are adsorbable onto the titanium dioxide particles so that on mixing a colloidally stabilised aqueous dispersion of the polymer particles with a colloidally stabilised aqueous dispersion of titanium dioxide particles, the moieties adsorb onto the titanium dioxide to form a colloidally stable aqueous dispersion of polymer-modified titanium dioxide which is useful in coating compositions.

Polymer-modified particulate titanium dioxide

A composite particle dispersion is prepared by mixing an aqueous dispersion of polymer particles which will form the particle shell with pre-formed polymer particles which will form the core at a temperature above the glass transition temperature for the shell particles. In order to ensure composite particle formation, certain interfacial energy criteria have to be satisfied for the core particle surface/shell particle surface/liquid interfaces. In order to allow the desired energy relationships to be established, the core particle surfaces include covalently attached ionic groupings which enable a permanent modification of the core particle surface to be made.

Composite particle dispersions

A process for the preparation of composite particle dispersons is disclosed. The composite particles have a core particle 1 surrounded by a second material 2. Normally a core shell particle will be formed and the second material which forms the shell will be a polymer material. The composite particles are formed by mixing a dispersion of polymer particles with pre-formed core material particles. The polymer particles are stabilized relative to one another, and the core material particles are destabilized in the dispersion so that they are able to make contact with the surfaces of the polymer particles. The process takes place at a temperature above the operative glass transition temperature of the polymer, and in the process the polymer spreads over the surface of the core particle so that the core particle is encapsulated. The process will proceed, and composite particles will be formed, when the interfacial energies of the three interfaces (core/polymer: core/liquid: polymer/liquid) and the relative volumes of the core particles and polymer particles are related to one another in accordance with an equation which is set out in the specification.

Polymerizable monomers of structure ##STR1## wherein R.sub.1 and R.sub.2 are C.sub.2-3 alkylene groups, the same or different; A and B are substituted C.sub.2-18 alkyl groups at least one group A or B comprising in a substituent a polymerizable ethylenically unsaturated group; and X=H, C.sub.1-18 alkyl or ##STR2## the monomers being substantially free from non-polymerizable water-soluble contaminants; processes of manufacture and derived polymers including copolymers; and aqueous polymer dispersions, their manufacture and use in coatings including paints.

Methacryloxy-containing compounds

Polymerizable monomers of structure ##STR1## wherein R.sub.1 and R.sub.2 are C.sub.2-3 alkylene groups, the same or different; A and B are substituted C.sub.2-18 alkyl groups at least one group A or B comprising in a substituent a polymerizable ethylenically unsaturated group; ane X=H, C.sub.1-18 alkyl or ##STR2## the monomers being substantially free from non-polymerizable water-soluble contaminants; processes of manufacture and derived polymers including copolymers; and aqueous polymer dispersions, their manufacture and use in coatings including paints.

Acryloxy-containing compounds

Polymerizable monomers of structure ##STR1## wherein R.sub.1 and R.sub.2 are C.sub.2-3 alkylene groups, the same or different; A and B are substituted C.sub.2-18 alkyl groups at least one group A or B comprising in a substituent a polymerizable ethylenically unsaturated group; and x=H, C.sub.1-18 alkyl or ##STR2## the monomers being substantially free from non-polymerizable water-soluble contaminants; processes of manufacture and derived polymers including copolymers; and aqueous polymer dispersions, their manufacture and use in coatings including paints.

Methacryloxy containing compounds

Sterically stabilized aqueous polymer depersions of at least 20% solids content are made by free radical-initiated polymerization of monomers in an aqueous medium at a temperature at least 10.degree. C. higher that the glass transition temperature of the polymer to be formed, in the presence of a pre-formed amphipathic block or graft copolymer which contains in the molecule a component solvatable by the medium and another component capable of associating with the polymer particles formed, the conditions being such that there is at no time present a separate monomer phase. The dispersions are useful as a basis of improved aqueous coating compositions.

Manufacture of aqueous polymer dispersions and coating compositions

A dispersion is described of block copolymer particles in a saturated aliphatic hydrocarbon diluent, the block copolymer consisting of a thermoplastic tertiary butyl styrene polymer block A of molecular weight 10,000-100,000 which is soluble in the diluent, an elastomeric conjugated diene polymer block B of molecular weight 1,000-100,000 which is terminally attached to block A, and a styrene homopolymer or copolymer block C of molecular weight 20,000-1,000,000 which is terminally attached to block B, is insoluble in the diluent and forms at least part of the core of the particles. The particles may be separated from the diluent while retaining their previous molecular organization, i.e. with the insoluble block C present in the core of the particles and the thermoplastic block A remote from the core, and may be converted by hot pressing into shaped articles having impact resistance. A process is also described for producing such a particle dispersion by anionic polymerization of monomers in the hydrocarbon diluent to form successively the polymer blocks A, B and C.

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Goring-on-Thames, United Kingdom

Julian A Waters