Digestion Accelerator and Method for Producing Pulp Using Same

The present disclosure relates to a digestion accelerator, and a method for producing pulp with the digestion accelerator.

Alkaline main agents are used for pulping materials including lignocellulose in digestion steps of methods for producing pulp. Digestion accelerators are used for efficiently performing digestion. As such a digestion accelerator, Patent Literature 1 discloses a digestion accelerator containing a quaternary ammonium compound. Patent Literature 2 discloses a digestion accelerator containing at least one of glucose and fructose.

In a case where an alkaline main agent and the digestion accelerator disclosed in Patent Literature 1 and Patent Literature 2 are used in a digestion step of a method for producing pulp, a material including lignocellulose can be efficiently digested as compared with digestion where only an alkaline main agent is used. However, there is a demand for a further increase in efficiency of digestion in order to efficiently produce pulp, from the viewpoint of price increase of wood according to the expansion of a demand for wood in recent years, suppression of deforestation according to global warming, and the like.

In view of the above circumstances, an objective of the present disclosure is to provide a digestion accelerator capable of efficiently digesting a material including lignocellulose in a digestion step of pulping a material including lignocellulose, and a method for producing pulp with the digestion accelerator.

The inventors of the present disclosure have made intensive studies for achieving the above objective, and as a result, have found that the above objective can be achieved by a digestion accelerator including a specified quaternary ammonium compound, and at least one amine compound selected from the group consisting of a specified primary monoamine, a specified secondary monoamine, and a specified tertiary monoamine, and a digestion accelerator including a specified quaternary ammonium compound, and a sulfur-containing compound that generates a sulfide ion, a polysulfide ion, or a hydrogen sulfide ion in the presence of the quaternary ammonium compound, thereby leading to completion of the present disclosure.

In order to achieve the above objective, [1] the digestion accelerator according to the present disclosure includes a quaternary ammonium compound represented by formula (1), and at least one amine compound selected from the group consisting of a primary monoamine represented by formula (2), a secondary monoamine represented by formula (3), and a tertiary monoamine represented by formula (4).

In formula (1), Ris an alkyl group having 8 to 22 carbon atoms, a hydroxyalkyl group having 8 to 22 carbon atoms, an alkenyl group having 8 to 22 carbon atoms, or a hydroxyalkenyl group having 8 to 22 carbon atoms,

In formula (2), Ris an alkyl group having 1 to 22 carbon atoms, an alkenyl group having 2 to 22 carbon atoms, a hydroxyalkyl group having 1 to 22 carbon atoms, a hydroxyalkenyl group having 2 to 22 carbon atoms, or an (AO)Z group, AO is an alkyleneoxy group having 2 to 4 carbon atoms, Z is a hydrogen atom or an acyl group, and k is an integer of 1 to 6.

In formula (3), Rand Rare each independently an alkyl group having 1 to 22 carbon atoms, an alkenyl group having 2 to 22 carbon atoms, a hydroxyalkyl group having 1 to 22 carbon atoms, a hydroxyalkenyl group having 2 to 22 carbon atoms, or an (AO)Z group, AO is an alkyleneoxy group having 2 to 4 carbon atoms, Z is a hydrogen atom or an acyl group, and r is an integer of 1 to 12.

In formula (4), Rand Rare each independently an alkyl group having 1 to 22 carbon atoms, an alkenyl group having 2 to 22 carbon atoms, a hydroxyalkyl group having 1 to 22 carbon atoms, a hydroxyalkenyl group having 2 to 22 carbon atoms, or an (AO)Z group, AO is an alkyleneoxy group having 2 to 4 carbon atoms, Z is a hydrogen atom or an acyl group, and t is an integer of 1 to 12, and

In addition, [2] a mass ratio between the quaternary ammonium compound and the amine compound may be 5:1 to 10000:1.

In addition, [3] the digestion accelerator according to the present disclosure includes a quaternary ammonium compound represented by formula (1), and a sulfur-containing compound that generates a sulfide ion, a polysulfide ion, or a hydrogen sulfide ion in the presence of the quaternary ammonium compound.

In formula (1), Ris an alkyl group having 8 to 22 carbon atoms, a hydroxyalkyl group having 8 to 22 carbon atoms, an alkenyl group having 8 to 22 carbon atoms, or a hydroxyalkenyl group having 8 to 22 carbon atoms,

In addition, [4] the sulfur-containing compound may include at least one compound selected from the group consisting of thiosulfate, hydrogen thiosulfate, sulfite, hydrogen sulfite, disulfite, dithionite, dithionate, disulfate, peroxosulfate, peroxodisulfate, and polythionate.

In addition, [5] a mass ratio between the quaternary ammonium compound and the sulfur-containing compound may be 1:2 to 100:1.

In addition, in order to achieve the above objective, [6] the method for producing pulp according to the present disclosure includes a digestion step of adding at least one main agent selected from the group consisting of an alkaline main agent and a sulfite-based main agent, and a digestion accelerator, to digest a material including lignocellulose, wherein the digestion accelerator is the digestion accelerator according to [1] or [3].

In addition, [7] a content of the digestion accelerator may be 0.001% by mass to 1.0% by mass relative to the material including the lignocellulose.

According to the digestion accelerator and the method for producing pulp with the digestion accelerator of the present disclosure, a material including lignocellulose can be efficiently digested.

Hereinafter, each mode for carrying out the present disclosure (hereinafter, simply referred to as “Embodiment”.) is described in detail. The following Embodiments are illustrative for describing the present disclosure, and are not intended to limit the present disclosure to the following content. The present disclosure can be appropriately modified and carried out within the gist thereof.

A digestion accelerator of Embodiment 1 includes a quaternary ammonium compound, and at least one amine compound selected from the group consisting of a primary monoamine, a secondary monoamine, and a tertiary monoamine. First, the quaternary ammonium compound and the amine compound are described. Next, the digestion accelerator including them is described.

The quaternary ammonium compound included in the digestion accelerator of Embodiment 1 is a compound represented by the following formula (1).

Furthermore, in a case where R, R, and Rin formula (1) are each a hydroxyalkyl group, a hydroxyalkenyl group, or an alkyleneoxy group, these each preferably have the following structure from the viewpoint of promotion of digestion.

In a case where Ris a hydroxyalkyl group having 1 to 22 carbon atoms, a hydroxyalkenyl group having 2 to 22 carbon atoms, or an (AO)Y group, the sum of the number of such hydroxyalkyl groups, the number of such hydroxyalkenyl groups, and n is preferably an integer of 1 to 15. The sum is more preferably 1 to 9, still more preferably 1 to 6.

In a case where Ror Rare each independently a hydroxyalkyl group having 1 to 4 carbon atoms, a hydroxyalkenyl group having 2 to 4 carbon atoms, or an (AO)Y group, the sum of the number of such hydroxyalkyl groups, the number of such hydroxyalkenyl groups, and m is preferably an integer of 1 to 15. The sum is more preferably 1 to 9, still more preferably 1 to 6.

In a case where, in Rand Ror R, Ris a hydroxyalkyl group having 1 to 22 carbon atoms, a hydroxyalkenyl group having 2 to 22 carbon atoms, or an (AO)Y group and Ror Ris each independently a hydroxyalkyl group having 1 to 4 carbon atoms, a hydroxyalkenyl group having 2 to 4 carbon atoms, or an (AO)Y group, the sum of the number of such hydroxyalkyl groups, the number of such hydroxyalkenyl groups, n, and m is preferably an integer of 2 to 15. The sum is more preferably 2 to 9, still more preferably 2 to 6.

In a case where, in Rand R, Rand Rare each independently a hydroxyalkyl group having 1 to 4 carbon atoms, a hydroxyalkenyl group having 2 to 4 carbon atoms, or an (AO)Y group, the sum of the number of such hydroxyalkyl groups, the number of such hydroxyalkenyl groups, and m is preferably an integer of 2 to 15. The sum is more preferably 2 to 9, still more preferably 2 to 6.

In a case where, in R, R, and R, Ris a hydroxyalkyl group having 1 to 22 carbon atoms, a hydroxyalkenyl group having 2 to 22 carbon atoms, or an (AO)Y group and Rand Rare each independently a hydroxyalkyl group having 1 to 4 carbon atoms, a hydroxyalkenyl group having 2 to 4 carbon atoms, or an (AO)Y group, the sum of the number of such hydroxyalkyl groups, the number of such hydroxyalkenyl groups, n, and m is preferably an integer of 3 to 15. The sum is more preferably 3 to 9, still more preferably 3 to 6.

Xin formula (1) represents a counterion. p represents the valence of an ion. p is 1 to 40, and is preferably 1 to 20, more preferably 1 to 3 from the viewpoint of productization, industrialization, and cost. The counterion is not limited as long as it is an anion capable of being taken with the quaternary ammonium compound to constitute a salt. Examples of the counterion include (i) an inorganic anion and (ii) an organic anion.

Examples of the inorganic anion (i) include halogen ions such as chloride ions and bromide ions, hydroxy ions, sulfate ions, nitrate ions, phosphate ions, borate ions, sulfonate ions, hypochlorite ions, nitrite ions, phosphite ions, diphosphite ions, sulfite ions, hydrogen sulfite ions, sulfide ions, hydrogen sulfide ions, polysulfide ions, thiol ions, thiosulfate ions, and thioglycollate.

Examples of the organic anion (ii) include i) an organic carboxylate ion, ii) phosphate ester ion, iii) a sulfonate ion, iv) an alkyl carbonate ion, v) a sulfate ester ion, and vi) an anionic polymer. Examples of the organic carboxylate ion i) include formate ions, acetate ions, propionate ions, gluconate ions, lactate ions, fumarate ions, maleate ions, and adipate ions. Examples of the phosphate ester ion ii) include polyoxyalkylene alkyl ether phosphate ester ions, alkyl phosphate monoester ions, alkyl phosphate diester ions, alkenyl phosphate ester ions, and aryl phosphate ester ions. Examples of the sulfonate ion iii) include alkylbenzenesulfonate ions and alkylsulfonate ions. Examples of the alkyl carbonate ion iv) include methyl carbonate ions and ethyl carbonate ions. Examples of the sulfate ester ion v) include alkyl sulfate ester ions and polyoxyalkylene alkyl ether sulfate ester ions. Examples of the anionic polymer vi) include polyacrylic acid, polymaleic acid, polyphosphoric acid, and polysulfuric acid compounds.

Among these counterions, the inorganic anion (i) is preferably a halogen ion such as a chloride ion or a bromide ion, a sulfate ion, a nitrate ion, a borate ion, or a phosphate ion from the viewpoint of promotion of digestion. The organic anion (ii) is preferably an alkyl phosphate monoester ion in which the number of carbon atoms in the alkyl group is 1 to 4, such as a butyl phosphate ester ion; an alkyl phosphate diester ion in which the number of carbon atoms in the alkyl group is 1 to 4, such as a dibutyl phosphate ester ion; an alkylbenzenesulfonate ion in which the number of carbon atoms in p-toluenesulfonate or the like is 1 to 4; or an alkyl sulfate ester ion in which the number of carbon atoms in the alkyl group is 1 to 4, such as a methyl sulfate ion (CHSO) or an ethyl sulfate ion (CHSO).

The amine compound included in the digestion accelerator of Embodiment 1 includes at least one amine compound selected from the group consisting of a primary monoamine, a secondary monoamine, and a tertiary monoamine.

The primary monoamine is a compound represented by the following formula (2).

In formula (2), Ris an alkyl group having 1 to 22 carbon atoms, an alkenyl group having 2 to 22 carbon atoms, a hydroxyalkyl group having 1 to 22 carbon atoms, a hydroxyalkenyl group having 2 to 22 carbon atoms, or an (AO)Z group. Here, AO is an alkyleneoxy group having 2 to 4 carbon atoms, and Z is a hydrogen atom or an acyl group. k is an integer of 1 to 6.

Ris preferably an alkyl group having 1 to 18 carbon atoms, an alkenyl group having 2 to 18 carbon atoms, a hydroxyalkyl group having 1 to 18 carbon atoms, a hydroxyalkenyl group having 2 to 18 carbon atoms, or an (AO)Z group from the viewpoint of promotion of digestion. Here, AO is an alkyleneoxy group having 2 to 4 carbon atoms, and Z is a hydrogen atom or an acyl group. k is an integer of 1 to 2. Ris more preferably an alkyl group having 10 to 14 carbon atoms, an alkenyl group having 10 to 14 carbon atoms, a hydroxyalkyl group having 10 to 14 carbon atoms, a hydroxyalkenyl group having 10 to 14 carbon atoms, or an (AO)Z group. Here, AO is an alkyleneoxy group having 2 to 4 carbon atoms, and Z is a hydrogen atom or an acyl group. k is 1.

The secondary monoamine is a compound represented by the following formula (3).

In formula (3), Ris an alkyl group having 1 to 22 carbon atoms, an alkenyl group having 2 to 22 carbon atoms, a hydroxyalkyl group having 1 to 22 carbon atoms, a hydroxyalkenyl group having 2 to 22 carbon atoms, or an (AO)Z group. Here, AO is an alkyleneoxy group having 2 to 4 carbon atoms, and Z is a hydrogen atom or an acyl group. r1 is an integer of 1 to 12. In formula (3), Ris an alkyl group having 1 to 22 carbon atoms, an alkenyl group having 2 to 22 carbon atoms, a hydroxyalkyl group having 1 to 22 carbon atoms, a hydroxyalkenyl group having 2 to 22 carbon atoms, or an (AO)Z group. Here, AO is an alkyleneoxy group having 2 to 4 carbon atoms, and Z is a hydrogen atom or an acyl group. r2 is an integer of 1 to 12. In addition, Rand Rmay be the same as or different from each other.

Here, the (AO)Z group of Rand the (AO)Z group of Rmay also be collectively designated as “(AO)Z group”.

Rand Rin formula (3) each preferably have the following structure from the viewpoint of promotion of digestion.

Ris preferably an alkyl group having 1 to 18 carbon atoms, an alkenyl group having 2 to 18 carbon atoms, a hydroxyalkyl group having 1 to 18 carbon atoms, a hydroxyalkenyl group having 2 to 18 carbon atoms, or an (AO)Z group. Here, AO is an alkyleneoxy group having 2 to 4 carbon atoms, and Z is a hydrogen atom or an acyl group. r1 is an integer of 1 to 6. Ris more preferably an alkyl group having 10 to 14 carbon atoms, an alkenyl group having 10 to 14 carbon atoms, a hydroxyalkyl group having 10 to 14 carbon atoms, a hydroxyalkenyl group having 10 to 14 carbon atoms, or an (AO)Z group. Here, AO is an alkyleneoxy group having 2 to 4 carbon atoms, and Z is a hydrogen atom or an acyl group. r1 is an integer of 2 to 4.

Ris preferably an alkyl group having 1 to 18 carbon atoms, an alkenyl group having 2 to 18 carbon atoms, a hydroxyalkyl group having 1 to 18 carbon atoms, a hydroxyalkenyl group having 2 to 18 carbon atoms, or an (AO)Z group. Here, AO is an alkyleneoxy group having 2 to 4 carbon atoms, and Z is a hydrogen atom or an acyl group. r2 is an integer of 1 to 6. Ris more preferably an alkyl group having 1 to 4 carbon atoms, an alkenyl group having 2 to 4 carbon atoms, a hydroxyalkyl group having 1 carbon atom, a hydroxyalkenyl group having 2 to 4 carbon atoms, or an (AO)Z group. Here, AO is an alkyleneoxy group having 2 to 4 carbon atoms, and Z is a hydrogen atom or an acyl group. r2 is an integer of 2 to 4.