Salts of acid-containing AB diblock copolymers as charge directors for positive-working electrostatic liquid developers

A process for preparing a positive-working electrostatic liquid developer for electrostatic imaging comprising

• (A) dispersing at an elevated temperature in a vessel a thermoplastic resin, and a nonpolar liquid having a Kauri-butanol value of less than 30, while maintaining the temperature in the vessel at a temperature sufficient to plasticize and liquify the resin and below that at which the nonpolar liquid degrades and the resin decomposes,
• (B) cooling the dispersion, either
• (1) without stirring to form a gel or solid mass, followed by shredding the gel or solid mass and grinding by means of particulate media with or without the presence of additional liquid;
• (2) with stirring to form a viscous mixture and grinding by means of particulate media with or without the presence of additional liquid;
• or
• (3) while grinding by means of particulate media to prevent the formation of a gel or solid mass with or without the presence of additional liquid;
• (C) separating the dispersion of toner particles having an average by area particle size of less than 10 .mu.m from the particulate media, and
• (D) adding to the dispersion during or subsequent to Step (A) an AB diblock copolymer charge director substantially soluble in component (A), wherein the B block is a polymer substantially soluble in component (A) having a number average molecular weight range of 2,000 to 50,000, and the A block is a salt of a carboxylic acid-containing polymer having a number average molecular weight range of 200 to 10,000, the weight percent of the A block being 5 to 40% of the polymer.

A process for preparing a positive-working electrostatic liquid developer comprising

• (A) dispersing a thermoplastic resin and optionally a colorant and/or adjuvant in the absence of a nonpolar liquid having a Kauri-butanol value of less than 30 to form a solid mass.
• (B) shredding the solid mass,
• (C) grinding the shredded solid mass by means of particulate media in the presence of a liquid selected from the group consisting of a polar liquid having a Kauri-butanol value of at least 30, a nonpolar liquid having a Kauri-butanol value of less than 30, and combinations thereof,
• (D) separating the dispersion of toner particles having an average by area particle size of less than 10 .mu.m from the particulate media, and
• (E) adding additional nonpolar liquid, polar liquid or combinations thereof to reduce the concentration of toner particles to between 0.1 to 15 percent by weight with respect to the liquid;
• and
• (F) adding to the dispersion an AB diblock copolymer charge director substantially soluble in component (A), wherein the B block is a polymer substantially soluble in component (A) having a number average molecular weight range of 2,000 to 50,000, and the A block is a salt of a carboxylic acid-containing polymer having a number average molecular weight range of 200 to 10,000, the weight percent of the A block being 5 to 40% of the polymer.

A process for preparing a positive-working electrostatic liquid developer comprising

• (A) dispersing a thermoplastic resin and optionally a colorant and/or adjuvant in the absence of a dispersant nonpolar liquid having a Kauri-butanol value of less than 30 to form a solid mass.
• (B) shredding the solid mass,
• (C) redispersing the shredded solid mass at an elevated temperature in a vessel in the presence of a nonpolar liquid having a Kauri-butanol value of less than 30, while maintaining the temperature in the vessel at a temperature sufficient to plasticize and liquify the resin and below that at which the nonpolar liquid degrades and the resin and/or colorant decomposes,
• (D) cooling the dispersion, either
• (1) without stirring to form a gel or solid mass, followed by shredding the gel or solid mass and grinding by means of particulate media with or without the presence of additional liquid;
• (2) with stirring to form a viscous mixture and grinding by means of particulate media with or without the presence of additional liquid;
• or
• (3) while grinding by means of particulate media to prevent the formation of a gel or solid mass with or without the presence of additional liquid;
• (E) separating the dispersion of toner particles having an average by area particle size of less than 10 .mu.m from the particulate media, and
• (F) adding additional nonpolar liquid, polar liquid or combinations thereof to reduce the concentration of toner particles to between 0.1 to 15 percent by weight with respect to the liquid;
• and
• (G) adding to the dispersion an AB diblock copolymer charge director substantially soluble in component (A), wherein the B block is a polymer substantially soluble in component (A) having a number average molecular weight range of 2,000 to 50,000, and the A block is a salt of a carboxylic acid-containing polymer having a number average molecular weight range of 200 to 10,000, the weight percent of the A block being 5 to 40% of the polymer.