JP2002069878A - Method for producing bleached kraft pulp and printing paper produced by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing bleached kraft pulp, capable of reducing the occurrence of vessel pick in the production of the bleached kraft pulp from a raw material having large vessels for which no effective treating method is established, and to obtain a printing paper using the pulp. SOLUTION: This method for producing bleached kraft pulp is characterized in that in a method for producing a bleached kraft pulp form wood having a large-scale vessel as a raw material, a pH adjustment is carried out after oxygen bleaching and successively chlorine bleaching is performed. The range of the pH adjustment is 7-2, preferably 4-2. This printing paper is characterized by using the bleached kraft pulp produced by the method for producing a bleached kraft pulp.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing bleached kraft pulp and a printing paper produced using the method. More specifically, in the production of bleached kraft pulp from a material having a large vessel such as eucalyptus as a raw material, the present invention relates to a method for producing bleached kraft pulp in which the occurrence of vessel picks is reduced, and a printing paper produced using the same. is there.

[0002]

2. Description of the Related Art The kraft process is currently the main method of producing chemical pulp in the world. This is because pulp with high strength can be obtained regardless of the type of wood used as a raw material, and pulp with high whiteness can be obtained by progress in bleaching methods.

[0003] As described above, the Kraft method does not select a tree species as a raw material, but in consideration of economic efficiency, the tree species to be used is higher in yield, more easily bleachable, and requires less bleaching chemicals. It is desirable that

Eucalyptus is a tree species satisfying such economic requirements, and is actually widely used at present. However, eucalyptus is characterized by having a large amount of vessels.

[0005] The vessel peels off during printing, leaving white voids on the printed surface. This is generally called a vessel pick and is considered to be undesirable in terms of printability.

In order to reduce the occurrence of the vessel pick, a method of reducing the absolute amount of the vessel by reducing the ratio of the eucalyptus material in the raw material has been adopted.

As another method, there is a method in which the vessel is treated with an enzyme to reduce the occurrence of vessel picking. However, the treatment with the enzyme also affects the fiber itself, resulting in a decrease in strength and a decrease in yield. Is known to occur.

As another countermeasure, there is a method of increasing the surface strength of paper by adding a chemical during papermaking, but it is economically disadvantageous because the amount of chemical used increases.

As described above, eucalyptus is excellent in economy and the like, but its use is limited due to the problem of vessel, and an effective countermeasure is strongly desired.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a bleached kraft pulp made from a material having a large vessel, for which an effective countermeasure has not been established, to reduce the occurrence of vessel picking. An object of the present invention is to provide a method for producing kraft pulp and printing paper using the pulp.

[0011]

As a result of intensive studies to solve the above-mentioned problems, the pH of kraft pulp after oxygen bleaching was determined.
Was adjusted, followed by chlorine bleaching, to reduce the occurrence of vessel picking, thereby completing the present invention.

That is, the method for producing bleached kraft pulp of the present invention is characterized in that, in the method for producing bleached kraft pulp using a material having a large vessel as a raw material, pH is adjusted after oxygen bleaching, followed by chlorine bleaching. It is assumed that.

In the present invention, the range of pH adjustment is 7 to 2
It is characterized by being.

Further, in the present invention, the range of pH adjustment is preferably from 4 to 2.

In the present invention, it is preferable to use an inorganic acid for pH adjustment.

The printing paper of the present invention is characterized by using bleached kraft pulp produced by the above method for producing bleached kraft pulp.

[0017]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing bleached kraft pulp which reduces the occurrence of vessel picking which is a problem in bleached kraft pulp from a material having a large vessel, and a printing paper using this pulp. provide.

The type of the acid used for adjusting the pH in the present invention is not particularly limited, and examples thereof include hydrochloric acid, sulfuric acid, and nitric acid, with sulfuric acid being preferred.

The range of pH adjustment in the present invention is 7 to 2,
More preferably, it is 4 to 2.

In the present invention, the pulp concentration at the time of chlorine bleaching performed after the pH adjustment is 1 to 40% by weight, more preferably 10 to 30% by weight.

In the present invention, the processing time for bleaching after the pH adjustment is 30 minutes or more, more preferably 60 minutes.
~ 120 minutes.

In the present invention, the pulp concentration at the time of chlorine bleaching after the pH adjustment is 1 to 40% by weight, more preferably 10 to 30% by weight.

The processing temperature for chlorine bleaching performed after the pH adjustment in the present invention is 30 to 100 ° C., and more preferably 40 to 80 ° C.

In the present invention, the chlorine addition at the time of chlorine bleaching performed after the pH adjustment is 0.1 to 3% by weight, more preferably 1 to 2% by weight.

There is no particular limitation on the bleaching chemical used in the bleaching performed after chlorine bleaching of the present invention.

In the bleached kraft pulp manufactured according to the present invention, the surface of the vessel is modified without deteriorating the strength, and the vessel pick is reduced by increasing the bonding strength between the vessel and the fiber.

[0027]

The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to these examples.

Comparative Examples 1 to 3 and Examples 1 to 3 In order to prove that the pH of the pulp after oxygen bleaching was adjusted and then chlorine bleaching was carried out to reduce the vessel picking, the oxygen was bleached in a laboratory. After adjusting the pH of the pulp after bleaching to various pH, C / D-EHD- containing chlorine in the first stage
Sequence (C; chlorine bleaching, D; chlorine dioxide bleaching, E
Alkaline extraction, H; hypo bleaching), and the number of vessels picked was compared. Comparative Example 1
In Examples 1-3, the pH was adjusted with caustic soda, and in Examples 1-3, the pH was adjusted with sulfuric acid. Table 1 shows the measurement results.

The pulp used was 100% eucalyptus as a raw material tree species, and pulp which had been subjected to oxygen bleaching on an actual machine was used.

The number of occurrences of vessel picks was determined by treating the processed pulp as a handmade sheet, printing it with a black solid printing machine using an RI printer, counting the number of vessel picks generated at that time, and comparing the numbers.

[0031]

[Table 1]

Examples 4 to 6 In order to confirm the influence of the bleaching chemicals used after pH adjustment after oxygen bleaching and subsequent chlorine bleaching, the number of occurrences of Vessel picks was compared in the laboratory by changing the bleaching chemicals. Was. Table 2 shows the measurement results. (D; chlorine dioxide bleaching,
E: alkali extraction, H: hypo bleaching, P: hydrogen peroxide bleaching)

[0033]

[Table 2]

Evaluation: From Tables 1 and 2 above, it can be seen that by adjusting the pH of the pulp after oxygen bleaching to pH 7 or less and then performing chlorine bleaching, the vessel pick can be reduced to a level at which there is no problem as printing paper. Understand. Table 2
Thus, this effect does not depend on the type of chemical used after chlorine bleaching.

[0035]

As described above, according to the present invention,
In the production of bleached kraft pulp from a material having a large vessel, it becomes possible to produce bleached kraft pulp with reduced occurrence of vessel picks. Further, by using the bleached kraft pulp, it becomes possible to obtain a printing paper excellent in printing suitability with less occurrence of vessel picking.

Claims (5)

[Claims] 1. A method for producing bleached kraft pulp using a material having a large vessel as a raw material.
A method for producing bleached kraft pulp, comprising adjusting and then performing chlorine bleaching. 2. The method for producing bleached kraft pulp according to claim 1, wherein the range of pH adjustment is 7 to 2. 3. The method for producing bleached kraft pulp according to claim 1, wherein the range of pH adjustment is 4 to 2. 4. The method for producing bleached kraft pulp according to claim 1, wherein an inorganic acid is used for pH adjustment. 5. A printing paper characterized by using bleached kraft pulp produced by the method for producing bleached kraft pulp according to any one of claims 1 to 4.