Abstract: Urethane-modified polyester resin which has a total acid value not greater than 10 KOH mg/g and is obtained by kneading, in a molten state, a base polyester resin (A) having an acid value of 5 to 20 KOH mg/g and a hydroxyl value of 40 to 70 KOH mg/g, a low-molecular-weight polyester resin (B) having an acid value not greater than 5 KOH mg/g, a hydroxyl value not greater than 10 KOH mg/g and a weight-average molecular weight of 3,000 to 5,000 and a polyisocyanate compound, wherein components (A) and (B) are at a weight ratio of 3 to 5:7 to 5 and the polyisocyanate compound is in an amount of 0.2 to 1.2 equivalent, in terms of an isocyanate group per equivalent, of the total hydroxyl groups of all the resins.

Abstract: An object of the present invention is to provide an electrostatic image developing toner having good charge properties, low-temperature fixing properties, offset resistance and blocking resistance as well as good resistance against sticking to a heated roll and wax dispersibility and a novel urethane-modified polyester resin used for the toner.

Abstract: Urethane modified polyester resin which has a total acid value not greater than 10 KOH mg/g and has been obtained by kneading, in a molten state, a base polyester resin (A) having an acid value of 5 to 20 KOH mg/g and a hydroxyl value of 40 to 70 KOH mg/g, a low-molecular-weight polyester resin (B) having an acid value not greater than 5 KOH mg/g, a hydroxyl value not greater than 10 KOH mg/g and a weight-average molecular weight of 3,000 to 5,000 and a polyisocyanate compound, by using the components (A) and (B) at a weight ratio of 3 to 5:7 to 5 and the polyisocyanate compound in an amount of 0.2 to 1.2 equivalent, in terms of an isocyanate group per equivalent, of the total hydroxyl groups of all the resins. This novel urethane-modified polyester resin (C) is used as a binder resin for the toner. For the preparation of the toner, the resin is mixed and kneaded with a colorant, magnetic powders, charge control agent and the like under a molten state, followed by cooling and pulverization.

Abstract: The present invention provides a toner composition mainly comprising a binder resin (D) which contains at least 20% by weight of an urethane-modified polyester resin (C) obtained by reacting a polyester resin (A) with an isocyanate compound (B) and whose gel fraction ranges from 2 to 75% by weight. The toner composition exhibits good melting properties upon heating suitable for fast reproduction such as a low lower limit of the fixing temperature and a wide range for permitted fixing temperature and is further excellent in resistance to blocking, resistance to carrier contamination and image-forming properties. The binder resin as the main component of the toner composition can be prepared according to a method comprising the step of continuously adding an isocyanate compound (B) to a polyester resin (A) in an equivalent ratio, NCO/OH, of the amount of the NCO groups of the isocyanate compound (B) to that of OH groups of the polyester resin (A) ranging from 0.3 to 1.

Abstract: Disclosed is a toner composition for electrophotography which comprises, as a principal component, a urethane-modified polyester resin whose loss tangent (tan .delta.) has a maximum and a minimum both falling within the range of from 0.7 to 2.5, the loss tangent being determined at 150.degree. C. and a frequency ranging from 10.sup.-2 to 10 Hz. The toner composition has excellent low temperature fixing ability and offset resistance as well as a wide range of permitted fixing temperature.

Abstract: A toner composition for electrophotography comprises, as a principal component, a reaction product of a mixture which comprises 20 to 80% by weight of a polyester resin (A) whose number average molecular weight ranges from 1,000 to 5,000, whose glass transition point ranges from 0.degree. to 50.degree. C. , whose OH value ranges from 20 to 60 KOHmg/g and which is prepared by using at least one trifunctional alcohol in an amount of from 2 to 10 mole % on the basis of the total amount of starting raw alcohols consisting of at least one diol and at least one trifunctional alcohol; and 80 to 20% by weight of a polyester resin (B) whose number average molecular weight ranges from 1,000 to 5,000, whose glass transition point ranges from 50.degree. to 90.degree. C. and whose OH value is not more than 5 KOH mg/g, with a diisocyanate.

Abstract: A resin for toner of electrophotography comprises a urethane-modified polyester resin (D) having a glass transition temperature ranging from 40.degree. to 75.degree. C., which is obtained by reacting a resin mixture composed of a polyester resin (A) having a number-averaging molecular weight of 1,000 to 15,000 and a hydroxyl value of 10 to 100 and a polyester resin (B) having a number-average molecular weight ranging from 1,000 to 5,000 and a sum of acid value and hydroxyl value of less than 10, in a weight ratio of (A)/(B) ranging from 20:80 to 60:40, with 0.3 to 0.99 molar equivalent of an isocyanate compound (C) per one molar equivalent of hydroxyl group of the polyester resin (A).The resin for toner is excellent in grindability and storage stability and it provides toners for electrophotography having good anti-blocking properties and good fixing properties whereby good images free of fogging can be obtained.

Abstract: A resin for toner of electrophotography comprises a urethane-modified polyester resin (D) having a glass transition temperature ranging from 40.degree. to 75.degree. C., which is obtained by reacting a resin mixture composed of a polyester resin (A) having a number-average molecular weight of 1,000 to 15,000 and a hydroxyl value of 10 to 100 and a polyester resin (B) having a number-average molecular weight ranging from 1,000 to 5,000 and a sum of acid value and hydroxyl value of less than 10, in a weight ratio of (A)/(B) ranging from 20:80 to 60:40, with 0.3 to 0.99 molar equivalent of an isocyanate compound (C) per one molar equivalent of hydroxyl group of the polyester resin (A).The resin for toner is excellent in grindability and storage stability and it provides toners for electrophotography having good anti-blocking properties and good fixing properties whereby good images free of fogging can be obtained.

Abstract: Disclosed is a toner composition for the electrophotography, which comprises as a main component a urethane-modified polyester resin obtained by reacting a polyester resin with an isocyanate compound, in which the mole-equivalent ratio between the hydroxyl group of the polyester resin and the isocyanate group of the isocyanate compound is within a specific range and the glass transition temperature of the obtained resin is within a specific range.This composition has a good fixing property at a low temperature and a good offset resistance at a high temperature, and this composition is especially excellent in the form of a mixture with a polymer having a relatively low molecular weight.