Patent ID: 7297229

Claim:
A process for producing a paper having a bulk density of more than 0.308 g/cm 3 , said process consisting of: obtaining a pulp slurry containing a virgin and/or a deiniced pulp that has been subjected to a deinicing process including both a floatation step and a washing step; adding a cationic compound and a nonionic surfactant to the pulp slurry containing the virgin and/or the deiniced pulp and evenly blending the cationic compound and the nonionic surfactant with the pulp slurry containing the virgin and/or the deinked pulp; and obtaining a paper having a bulk density of more than 0.308 g/cm 3 from the pulp slurry containing the virgin and/or the deinked pulp; wherein the cationic compound is a cationic compound represented by formula (a 1 ) or (b 1 ): wherein in formula (a 1 ) or (b 1 ), R 11 and R 12 are the same as or different from each other, and each represents an alkyl, alkenyl or β-hydroxyalkyl group having 8 to 24 carbon atoms; R 13 , R 14 and R 15 arc the same as or different from each other, and each of R 13 , R 14 and R 15 represents an alkyl group or hydroxyalkyl group having 1 to 8 carbon atoms, benzyl or -(AO)n 11 -Z 11 , wherein AO is an oxyalkylene unit having 2 or 3 carbon atoms, Z 11 represents a hydrogen atom or an acyl group, and n 11 is an integer of 1 to 50; R 16 represents an alkyl, an alkenyl or β-hydroxyalkyl group having 8 to 36 carbon atoms; and X − is an anion; and the nonionic surfactant is at least one of the nonionic surfactants represented by (A) to (C): (A): a compound represented by the following formula (A) R 81 O(EO) m 81 (PO) n 81 H (A) wherein R 81 is a C6 to C22 straight or branched alkyl or alkenyl group or an alkylaryl group having a C4 to C20 alkyl group; E is an ethylene unit; P is a propylene unit; m 81 and n 81 are an average number of added moles, m 81 is a number in the range of 0 to 20 and n 18 is a number in the range of 0 to 50; and the addition form of EO and PO may be any of block and random and the addition order of BO and PO may not be limited; (B): a compound represented by the following formula (B) R 81 COO(EO) m 81 (PO) n 81 R b (B) wherein R 81 , E, P, m 81 and n 81 are the same as those of the formula (A); and R b is H, an alkyl group, an alkenyl group or an alkylaryl group; and (C): a nonionic surfactant selected from the following (1) to (3): (1) a nonionic surfactant based on fat, (2) a nonionic surfactant based on sugar alcohol, and (3) a nonionic surfactant based on sugar, wherein the cationic compound and the nonionic surfactant are added in a combined amount of 0.01 to 10 wt % based on the weight of the virgin and/or the deinked pulp, and wherein a ratio by weight of said cationic compound to the at least one non-ionic surfactant represented by (A) to (C) is from 1/99 to 50/50.