초록 ▼

A paper making process with improved retention and binding of fillers is characterized by the use of an amphoteric mucous compound as binder. The preferred compound is the reaction product between cationic starch (CS) of low charge density and a polysaccharide acid such as carboxymethyl cellulose (C

A paper making process with improved retention and binding of fillers is characterized by the use of an amphoteric mucous compound as binder. The preferred compound is the reaction product between cationic starch (CS) of low charge density and a polysaccharide acid such as carboxymethyl cellulose (CMC). This compound has amphoteric and mucous character and should be used for enveloping fillers, while in a unique transient structure. This structure is characterized by filler particles being enclosed and finely distributed in droplets of the highly hydrated but substantially water-insoluble mucous compound. According to the invention this transient structure should further be reorganized to a less hydrated and more resistant gel structure, still enclosing the filler. This gel structure can stand the draining forces on a paper machine wire screen. This structural reorganization is achieved by reaction with colloidal particles, especially of polyaluminum-oxy-citrate compounds. The process yields paper of high strength and filler retentions of more than 90% at a single wire passage even at extreme filler contents of 30-60% of the paper weight.

대표청구항 ▼

In a method for forming paper from an aqueous slurry of cellulosic fibers and a separate slurry of mineral fillers mixed with and enveloped by a dispersion of cationic starch (CS) and carboxymethyl cellulose (CMC) or alginate, the improvement comprising the steps of: (a) swelling 100 parts by weight

In a method for forming paper from an aqueous slurry of cellulosic fibers and a separate slurry of mineral fillers mixed with and enveloped by a dispersion of cationic starch (CS) and carboxymethyl cellulose (CMC) or alginate, the improvement comprising the steps of: (a) swelling 100 parts by weight CS particles in an aqueous solution of 1-8 parts, by weight, of carboxymethyl cellulose or alginate at temperature-time conditions selected to prevent molecular solubilization of the CS to form an aqueous dispersion of viscous CS droplets that is at least 2% CS by weight, said dispersion of CS droplets being superficially reacted with CMC or alginate, and adding this dispersion to said slurry of mineral fillers prior to attainment of coacervate equilibrium by said dispersion, thereby individually enveloping the filler particles; (b) adding to said slurry of enveloped mineral fillers, while still in a transitional non-equilibrium state, a synerese hardening compound comprising a solution of a polyaluminum complex having a composition within the stoichiometric formula limits Al12(OH)21-30Ci6-12(SO4)0-4, where Ci represents a citric acid equivalent, in an amount of at least 1% by weight of the CS measured as Al2O3, whereby a synerese hardening reaction is effected and the enveloped mineral fillers become less hydrated and form a strong gel.