Security pigment based on core-shell particles, and production method

A security pigment comprising chemically stable core-shell particles, each of the core-shell particles comprising

• a core based on a thermoplastic polymer,
• a shell based on a condensation polymer, and
• an organic or metalorganic feature substance present in dissolved or finely distributed form in the core,
• wherein the mass fraction of the shell amounts to more than 25%, relative to the mass of the core such that the core-shell particles are chemically stable, and
• wherein the condensation polymer is selected from aminoplasts, phenoplasts, melamine-formaldehyde resins (MF), melamine-phenol-formaldehyde resins (MPF), phenol-formaldehyde resins (PF), urea-formaldehyde resins (UF), melamine-guanidine-formaldehyde resins or phenol-resorcin-formaldehyde resins.

A method for producing a security pigment of core-shell particles, each of the core-shell particles being produced to comprise a solid core based on a thermoplastic polymer, a shell based on a condensation polymer, and an organic or metalorganic feature substance present in dissolved or finely distributed form in the core, the method comprising:

• a) dissolving the feature substance together with the thermoplastic polymer in an organic solvent and dispersing the obtained solution in water by means of a surfactant;
• b) supplying at a certain pH value prepolymer units to be polymerized in a condensation reaction such that condensation of the shell-forming polymer around the dispersed droplets of the organic solvent is achieved;
• and
• c) removing the organic solvent such that the core-shell particles are formed with a solid core;
• wherein the mass fraction of the shell amounts to more than 25%, relative to the mass of the core, such that the core-shell particles are chemically stable, and
• wherein the condensation polymer includes an aminoplast, a phenoplast, a melamine-formaldehyde resin (MF), a melamine-phenol-formaldehyde resin (MPF), a phenol-formaldehyde resin (PF), a urea-formaldehyde resin (UF), a melamine-guanidine-formaldehyde resin, or a phenol-resorcin-formaldehyde resin.

A method for producing a security pigment of core-shell particles, each of the core-shell particles being produced to comprise a solid core based on a thermoplastic polymer, a shell based on a condensation polymer, and an organic or metalorganic feature substance present in dissolved or finely distributed form in the core, the method comprising:

• a) preparing the core based on a thermoplastic polymer, in which the feature substance is present in dissolved or finely distributed form, wherein the thermoplastic polymer has functional groups on its outside, which are suitable for prepolymer units to bind thereto covalently for preparing the shell;
• b) preparing the shell from prepolymer units polymerizing in a condensation reaction, said units growing directly to the core through reaction with the functional groups of the thermoplastic core,
• wherein the mass fraction of the shell amounts to more than 25%, relative to the mass of the core, such that the core-shell particles are chemically stable, and
• wherein the condensation polymer includes an aminoplast, a phenoplast, a melamine-formaldehyde resin (MF), a melamine-phenol-formaldehyde resin (MPF), a phenol-formaldehyde resin (PF), a urea-formaldehyde resin (UF), a melamine-guanidine-formaldehyde resin, or a phenol-resorcin-formaldehyde resin.

A method for producing a security pigment of core-shell particles, each of the core-shell particles being produced to comprise a solid core based on a thermoplastic polymer, a shell based on a condensation polymer, and an organic or metalorganic feature substance present in dissolved or finely distributed form in the core, the method comprising:

• a) dissolving an organic or metalorganic feature substance in a thermoplastic polymer to supply in this manner thermoplastic particles with feature substance dissolved therein;
• and
• b) incorporating the thermoplastic particles with feature substance dissolved therein obtained in step a) in a duromer matrix,
• c) grinding the product obtained in step b) to pigment particles,
• wherein the mass fraction of the shell amounts to more than 25%, relative to the mass of the core, such that the core-shell particles are chemically stable, and
• wherein the condensation polymer includes an aminoplast, a phenoplast, a melamine-formaldehyde resin (MF), a melamine-phenol-formaldehyde resin (MPF), a phenol-formaldehyde resin (PF), a urea-formaldehyde resin (UF), a melamine-guanidine-formaldehyde resin, or a phenol-resorcin-formaldehyde resin.