Abstract: An encapsulated toner for heat-and-pressure fixing which is composed of a heat-fusible core containing at least a coloring material and a shell formed so as to cover the surface of the core, wherein the main component of the shell is a resin prepared by reacting an iso(thio)cyanate compound comprising(1) 0 to 30 mole % of monovalent isocyanate and/or isothiocyanate compounds and(2) 100 to 70 mole % of at least divalent isocyanate and/or isothiocyanate compounds with an active hydrogen compound comprising(3) 0 to 30 mole % of a compound having one active hydrogen atom reactive with isocyanate and/or isothiocyanate groups and(4) 100 to 70 mole % of a compound having at least two active hydrogen atoms reactive with isocyanate and/or isothiocyanate groupsat a molar ratio of the components (1) and (2) to the components (3) and (4) of between 1:1 and 1:20, and wherein at least 30% of the whole linkages in which an isocyanate or isothiocyanate group participates are thermally dissociating linkages.

Abstract: A novel resin is produced by the step of polymerizing (a) styrene and/or a derivative thereof, (b) a monomer component selected, alone or in combination of two or more, from the group consisting of methacrylic acid, acrylic acid, a methacrylic ester and an acrylic ester, and (c) 0.05 to 10 percent by weight, based on the total weight of the monomers, of a polybasic acid having 7 to 40 carbon atoms, an anhydride thereof or a lower (C1 to C6) alkyl ester thereof, the monomer component (b) containing at least one acrylic or methacrylic ester having hydroxyl or epoxy group in at least equimolar amount to the component (c) and has a softening point of 100.degree. to 160.degree. C. and a glass transition temperature of 50.degree. C. or higher. It is useful as a binder resin for a toner composition.

Abstract: A modified polyester is produced by co-condensation-polymerizing a starting linear polyester which may have a branched group, having a number-average molecular weight of 300 to 1,400 and containing from 10 to less than 25 mole percent, basd on the total constituent monomer units of the starting polyester, of a dihydric alcohol having the following formula: HO--(CH2)n--OH, in which n is an integer of 2 to 6, with a tri- or more-valent monomer(s) selected from a tri- or higher valent carboxylic acid, a derivative thereof and a tri- or higher-valent alcohol. The modified polyester is useful as binder resin in an electrophotographic developer composition and toner.

Abstract: An electrophotographic developer composition comprises a binder resin, which comprises a polyester as the major component, said polyester obtained by co-condensation polymerization of(i) a diol component represented by the general formula: ##STR1## wherein R is an ethylene or propylene group and x and y are each an integer of 1 or more, with the proviso that the average sum total of x and y is 2 to 7, with(ii) a dicarboxylic acid, an anhydride or a lower alkyl ester thereof and(iii) a polycarboxylic acid having at least three carboxyl groups or an anhydride or a lower alkyl ester thereof or a polyhydric alcohol having at least three hydroxyl groups and having an OHV/AV value of at least 1.2 wherein AV is an acid value of the polyester and OHV is a hydroxyl value thereof, and at least two charge controllers.

Abstract: A toner for developing electrostatic latent images which comprises a colorant and two kinds of polyester is disclosed.The fFirst polyester is a nonlinear polyester that is composed of monomers including monomers of trivalence or higher valency and which satisfies the following conditions A1 and A2, the second polyester is a nonlinear polyester that is composed of monomers including monomers of trivalence or higher valency and which satisfies the following conditions B1 and B2, and the difference between the softening points of said first and second polyesters is at least 10.degree. C.condition A1: the monomers of trivalence or higher valency represent from 0.05 mol % to less than 15 mol % of all the monomers present;condition A2: the softening point is in the range of from 120.degree. C. to 160.degree. C.;condition B1: the monomers of trivalence or higher valency represent from 0.05 mol % to less than 15 mol % of all the monomers represent;condition B2: the softening point is in the range of from 80.degree.

Abstract: A toner composition for electrophotography contains a binder resin, coloring material, and other additive as required, characterized in that the principal component of the binder resin is a polyester resin formed by co-condensation of(a) a diol component represented by the formula below; ##STR1## (where R denotes an ethylene group or propylene group; x and y each are integers greater than 1; and the average value of x+y is 2 to 7.)(b) a dibasic carboxylic acid, an acid anhydride thereof, or a lower alkyl ester thereof; and(c) tribasic or polybasic carboxylic acid, an acid anhydride thereof, or a lower alkyl ester thereof, or a trihydroxyl or polyhydroxylic alcohol; said polyester resin having an acid value (AV) and a hydroxy value (OHV) defined by OHV/AV=1.2 and up.

Abstract: A polyester for use as an electrophotographic toner composition is obtained by copolycondensation of (a) a diol component of polyoxyalkylene-bis(4-hydroxyphenyl)propane and (b) an acid component, improved by incorporating into the acid component a copolymer of styrene or a derivative thereof and a carboxylic vinyl monomer. A copolymer of an unsaturated aliphatic hydrocarbon and an unsaturated carboxylic acid and a polymer and copolymer of an unsaturated carboxylic acid may be used. The toner is improved in the prevention of off-set in the fixation step.