JP2003049385A - Newsprint paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide newsprint paper excellent in optical characteristics such as opacity and whiteness, bulky and excellent in printability. SOLUTION: Wood chips of broadleaf trees, more preferably those having cell wall thickness of >=4.0 runkel ratio and >=450 kg/m<3> volume-weight are impregnated in an aqueous alkaline hydrogen peroxide solution containing sodium hydroxide, sodium silicate, hydrogen peroxide and a chelating agent, subsequently refined at normal pressure or under pressure to produce bulky broadleaf tree-mechanical pulp which is included in newsprint paper in preferably 5-95 wt.% as a pulp component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a newsprint having a low density and excellent optical properties such as opacity and whiteness.

[0002]

2. Description of the Related Art Users are required to reduce the weight of newsprint from the viewpoint of effectively utilizing paper pulp produced from forest resources and reducing distribution costs. on the other hand,
With the recent increase in environmental protection, it is also desired to increase the distribution of waste paper pulp to newsprint. However, in the trend of weight reduction, increasing the distribution of waste paper pulp, which has a high density and low opacity, is limited from the viewpoint of the volume and opacity of newsprint, and in order to solve these problems, increase the bulk and increase the opacity. Was needed.

As a method of increasing the bulk of paper, that is, reducing the density, paper pulp has been studied. Generally, wood pulp is used as pulp for papermaking, but in order to reduce the density, it is necessary to polish wood with a grinder rather than chemical pulp obtained by extracting lignin, which is a reinforcing material in wood fibers, with chemicals. Mechanical pulp such as crushed ground pulp, refiner mechanical pulp that refines wood with a refiner, or thermomechanical pulp has more rigid fibers and is effective for lowering the density. However, although groundwood pulp has a high specific scattering coefficient and contributes to high opacity to paper, it is weak in strength and it is becoming difficult to secure logs as a raw material. Also, groundwood pulp is generally bulkier and less prone than refiner mechanical pulp. On the other hand, softwood refiner pulp has high bulkiness and high strength, but has a low specific scattering coefficient and does not contribute much to the opacity of paper.

Further, among the mechanical pulps, thermomechanical pulp has a long fiber length and high rigidity, but there is a problem that the smoothness of the produced sheet is lowered.

As a method for lowering the density of newsprint, Japanese Patent Publication No. 3041297 discloses that a bulking agent composed of a polyhydric alcohol and a fatty acid ester is added to make the surface of pulp fiber hydrophobic to produce a low density newsprint. Although the method described above has been described, it has been necessary to use expensive chemicals, resulting in the drawbacks of increased cost and reduced strength of paper.

Further, as a method of increasing the opacity, it is possible to add a filler, but this also lowers the strength and bulk of the paper,
Moreover, it is considered that the addition rate is limited because it causes paper dust.

[0007]

An object of the present invention is to provide a newsprint having high opacity, bulkiness and excellent printability.

[0008]

Means for Solving the Problems The present inventors have found that mechanical pulp produced from hardwood is finer in fibers and has higher optical characteristics than mechanical pulp produced from softwood, and therefore is effective in improving the opacity of newsprint. Considering that there is a hardwood, more preferably a thick cell wall with a Runkel ratio of 4.0 or more, 450
The present invention has been completed by blending a hardwood having a high volume weight of not less than kg / m ³ and a bulky mechanical pulp produced by chemical treatment.

The Runkel ratio defined in the present invention is RO
It is a parameter that H. Runkel published in Wachbl. Papierfabr. Magazine in 1940. (Runkel ratio) = (2 of fiber wall thickness)
Times) / (fiber inner diameter). A larger Runkel ratio indicates a stiffer fiber. The Runkel ratio shown in the specification is Fiber Lab. (Kajaani
It was calculated from the fiber width and fiber wall thickness measured by the company).

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The hardwood mechanical pulp used in the newsprint of the present invention is a mechanical pulp made from a hardwood material such as refiner groundwood pulp (RGP), thermomechanical pulp (TMP) and chemithermomechanical. Examples include pulp (CTMP), alkaline hydrogen peroxide mechanical pulp (APMP), alkaline hydrogen peroxide thermomechanical pulp (APTMP), and the like.

As the hardwood mechanical pulp used in the present invention, the above-mentioned APMP and APTMP are bulky, and have high opacity, high whiteness, and high strength.
It is preferable to use these. APMP is manufactured by impregnating wood chips with an aqueous solution of alkaline hydrogen peroxide containing sodium hydroxide, hydrogen peroxide and sodium silicate, and refining at atmospheric pressure. APTMP is refined at high temperature and pressure. Go to be manufactured.
Further, after the refining treatment, a pulp having a higher whiteness can be obtained by holding it with an aqueous solution of alkaline hydrogen peroxide at room temperature or under heating for 5 minutes or more. A
Aqueous alkaline hydrogen peroxide solution used when manufacturing PMP and APTMP is 0.2 to 2.0 with respect to absolute dry chip weight.
Wt% sodium hydroxide, 0.2-2.0 wt% sodium silicate, 0.01-0.2 wt% magnesium sulfate, 0.05-
An aqueous solution containing 0.4 wt% chelating agent and 0.2-5 wt% hydrogen peroxide is preferred.

Further, APMP and APTMP are described below in a) to
It is preferably produced in step i). a) a step of compressing hardwood wood chips at a compression ratio of at least 4: 1 and impregnating a chelating agent at the time of pressure release b) a step of holding the impregnated chips at a temperature of 10 ° C to 80 ° C for 5 minutes or more c) the above Further compressing the impregnated tip at a compression ratio of at least 4: 1 and impregnating with an alkaline chemical solution upon release d) holding the impregnated tip for about 10 minutes to 1 hour at a temperature of 10 ° C to 80 ° C e) The treated chips are further impregnated with alkaline peroxide, and the chips are defibrated by passing through a pressure or atmospheric pressure refining device to produce wood pulp f) The produced pulp is heated at a temperature of 50 ° C. or higher for 5 minutes or more Holding step g) step of diluting the manufactured pulp to a concentration of 5% or less, washing, and then concentrating again to 15% or more h) performing refining of the manufactured pulp under pressure or atmospheric pressure to obtain a desired filtration Step i) to obtain a pulp having water content Was pulp is manufactured through a process that is bleached in one or more steps using an oxidizing agent or reducing agent.

In the step a), it is preferable to use a chelating agent in an amount of 0.05 to 0.4%, and in the step c), the alkaline agent is added in an amount of 0.2 to the weight of the absolutely dried chips.
~ 2.0 wt% sodium hydroxide, 0.2-2.0 wt% sodium silicate, 0.01-0.2 wt% magnesium sulfate,
An aqueous solution containing 0.05 to 0.4% by weight of a chelating agent and 0.2 to 5% by weight of hydrogen peroxide is preferable.

In the step e), the bleached and softened wood chips are added with an alkaline peroxide containing a chelating agent immediately before the primary refining, and the wood chips are pressurized or subjected to an atmospheric pressure refining apparatus. Disintegrated into pulp fibers. A general defibration device is sufficient for refining,
Preferably, it is defibrated with a single disc refiner, a conical disc refiner, a double disc refiner, a twin disc refiner or the like.

Although the chips are bleached by the hydrogen peroxide in the alkaline hydrogen peroxide solution, it is desirable to remove the metal ions in order to enhance the reaction efficiency of the hydrogen peroxide. Therefore, in the step before adding the alkaline hydrogen peroxide aqueous solution, by complexing with a metal ion by a chelating agent,
Prevents decomposition of hydrogen peroxide. As a chelating agent, diethylenetriaminepentaacetic acid, 2-hydroxyethylethylenediaminetriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepenta (methylenephosphone)
Acetic acid or an alkali metal salt thereof is preferred.

When high whiteness is required for the obtained hardwood mechanical pulp, the pulp can be further bleached by one or more known bleaching steps. In this case, oxidizing agents such as hydrogen peroxide, ozone and peracetic acid, or reducing agents such as hydrosulfite (sodium dithionite), sodium hydrogensulfate, sodium borohydride, formamidinesulfinic acid (FAS), etc. Can be used.

Among the above-mentioned hardwood mechanical pulps, the hardwood mechanical pulp produced from a high volume heavy material having a Runkel ratio of 4.0 or more and a volume weight of 450 kg / m ³ or more is rigid and its fiber lumen (lumen) is hard to collapse. Therefore, the paper in which this pulp fiber is blended maintains a bulky structure and has a low density. As such tree species, Eucalyptus, particularly Eucalyptus globulus, Eucalyptus grandis, Eucalyptus europhyra, Eucalyptus nighttens, Eucalyptus legnans and the like are preferable.

[0018] Further, a hardwood machine having a density of 0.45 g / cm ³ or less when the handmade paper is prepared according to JIS P 8222: 1998 after being prepared to a Canadian standard freeness of 100 ml. With pulp, bulky newsprint can be manufactured.

In addition to the above-mentioned mechanical pulp produced from hardwood, the newsprint of the present invention includes chemical pulp (bleached kraft pulp of conifer (NBKP) or unbleached kraft pulp (NUKP)) and bleached kraft pulp of hardwood as raw material pulp ( LBKP) or unbleached kraft pulp (LUKP)
Etc.), mechanical pulp of softwood (groundwood pulp (GP), refiner mechanical pulp (RMP),
Thermo-mechanical pulp (TMP), chemi-thermo-mechanical pulp (CTMP), etc., and deinking pulp (DIP) are used alone or in a mixture at an arbitrary ratio.

The newsprint of the present invention can be produced with a hardwood mechanical pulp content of 5 to 95% by weight. In recent years, it has been required to increase the blending ratio of deinking pulp from the viewpoint of resource saving. Therefore, the content of hardwood mechanical pulp is 5 to 60% by weight, and the content of deinking pulp is 40 to 9%.
It is preferably 5% by weight.

The newsprint of the present invention can be made by a known paper machine such as a Fourdrinier paper machine, a gap former, a hybrid former (on-top former). The papermaking conditions are not particularly specified, and the pH during papermaking is
May be acidic, neutral or alkaline.

The newsprint of the present invention may contain a filler. As the filler, known fillers such as white carbon, talc, kaolin, clay, heavy calcium carbonate, light calcium carbonate, titanium oxide and synthetic resin filler can be used.

Further, the newsprint of the present invention is used for papermaking such as a sulfuric acid band and various anionic, cationic, nonionic or amphoteric retention improvers, drainage improvers, paper strength enhancers and internal sizing agents. An auxiliary agent can be used if necessary. Furthermore, there is no problem even if a dye, a fluorescent whitening agent, a pH adjusting agent, a defoaming agent, a pitch control agent, a slime control agent, etc. are added as necessary.

Further, for the purpose of improving the surface strength and size, a surface treatment agent containing a water-soluble polymer as a main component may be applied. As the water-soluble polymer, starch, oxidized starch,
As the surface treating agent such as modified starch, carboxymethyl cellulose, polyacrylamide, polyvinyl alcohol, etc., those usually used as surface treating agents can be used alone or in a mixture thereof. In addition to the water-soluble polymer, a paper strength enhancer for water resistance and surface strength improvement and an externally added sizing agent for sizing can be added to the surface treatment agent. The surface treatment agent can be applied by a coating machine such as a two-roll size press coater, a gate roll coater, a blade metalling coater, or a rod metalling coater.

As described above, by blending the hardwood mechanical pulp, a newsprint having high whiteness, high opacity, bulkiness and high strength can be obtained. For example, by blending APMP or APTMP produced from hardwood, the basis weight is 35 to 50 g / m ² , the whiteness is 53% or more, and the opacity is 90.
It is possible to produce newsprint paper having a density of not less than% and a density of not more than 0.6 g / cm ³ .

[0026]

EXAMPLES Examples will be shown below, but the examples do not limit the scope of the present invention. In the description,% means% by weight.

<Manufacture of Mechanical Pulp> Mechanical pulp was manufactured from the hardwood wood chips or softwood wood chips shown in Table 1 by using a lab scale device by the following method.

[Production Examples 1, 4 and 7] Production of Chemothermo-mechanical pulp (CTMP) Sodium sulfite was added at 2.0% based on the dry weight of wood chips, and impregnated at room temperature under reduced pressure of -760 mmHg for 30 minutes. After infiltrating the chemical solution, the chip was taken out and the raw material concentration was 40%, and the lab scale pressure refiner (BRP45-3 manufactured by Kumagai Riki Kogyo)
00SS) was used for primary refining at a temperature of 133 ° C. Further, the pulp concentration was adjusted to 20%, and secondary refining was carried out under atmospheric pressure using a lab scale atmospheric pressure refiner (BR-300CB manufactured by Kumagai Riki Kogyo Co., Ltd.). This time,
The freeness after the secondary refining was adjusted to 100 ml of Canadian Standard Freeness (CSF).

[Production Examples 2 and 5] Alkaline hydrogen peroxide thermomechanical pulp (APTM
Production of P) Wood chips in a chemical solution (sodium hydroxide is added at 1.5%, diethylenetriaminepentaacetic acid (DTPA) 0.3%, sodium silicate 2.0%, magnesium sulfate 0.05% based on the dry weight of wood chips) Room temperature, −760
Impregnation was carried out for 30 minutes under a reduced pressure of mmHg. After returning to normal pressure once, add hydrogen peroxide solution to the chemical solution per dry weight of wood chips.
It was added so as to be 2.5% and impregnated again at room temperature under reduced pressure of -760 mmHg for 1 hour. Next, insert the chip at a temperature of 60 ° C for 3
After holding for 0 minutes, primary refining was performed at a temperature of 133 ° C. using a pressure refiner for lab scale (BRP45-300SS manufactured by Kumagai Riki Kogyo) at a raw material concentration of 40%. Then, the pulp concentration was adjusted to 20%, and secondary refining was performed under atmospheric pressure by a lab scale atmospheric pressure refiner (BR-300CB manufactured by Kumagai Riki Kogyo Co., Ltd.). At this time, the freeness after the secondary refining was adjusted to 100 ml of CSF.

[Production Examples 3 and 6] Production of alkaline hydrogen peroxide mechanical pulp (APMP) DTPA was added to wood chips at 0.2 per dry weight of wood chips.
% -Sodium hydroxide per 1.5 wt% of wood chips after impregnation under reduced pressure of -760 mmHg
%, Hydrogen peroxide 2.0%, sodium silicate 2.0%, magnesium sulphate 0.1%, DTPA 0.2%, wood chips immediately before primary refining and during chemical impregnation under a reduced pressure of -760 mmHg. It was divided into and infiltrated.
Next, after holding the wood chips for 30 minutes at a temperature of 60 ° C, using a lab-scale atmospheric pressure refiner (BR-300CB manufactured by Kumagai Riki Kogyo) at a raw material concentration of 40%, primary refining was performed under atmospheric pressure. It was The obtained pulp was kept as it was at 60 ° C. for 30 minutes to allow the reaction of residual chemicals to proceed, and then the pulp concentration was diluted to 4% to adjust the pH to 7, and the pulp was washed. The washed pulp was concentrated again to a concentration of 20% and subjected to secondary refining under atmospheric pressure by a lab scale atmospheric pressure refiner (BR-300CB manufactured by Kumagai Riki Kogyo Co., Ltd.). This time,
The freeness after the secondary refining was adjusted to 100 ml of CSF.

A chemical solution was prepared according to the production recipe shown in Table 1, mechanical pulp was produced, and JI was prepared from the obtained pulp.
Producing handmade paper according to SP 8222: 1998, JIS P 814
Whiteness was measured according to 8 and opacity according to JIS P 8138. The results are shown in Table 1.

[0032]

[Table 1] The hardwood mechanical pulps of Production Examples 1 to 6 were pulps of higher whiteness while having the same opacity as the softwood mechanical pulp of Production Example 7. In particular, APTMP of Production Examples 2 and 5,
The APMPs of Production Examples 3 and 6 had significantly higher whiteness.

<Manufacture of Newspaper> [Examples 1 to 12 and Comparative Examples 1 to 8] The mechanical pulp manufactured in Manufacturing Examples 1 to 7 and ground wood pulp of Japanese red pine (GP, CSF 80 ml, whiteness 64.0%, non-existent). Transparency 9
4.0%), deinked pulp (DIP, CSF 180ml, whiteness)
54.0%, opacity 90.0%), softwood kraft pulp (N
KP, CSF 650ml, whiteness 83.0%, opacity 65.0
%) To a mixed pulp slurry having a pulp formulation shown in Table 2 to prepare a paper stock by adding a silica-based filler to the absolute dry weight of the pulp in an amount of 1% based on the weight of the pulp.
From this stock material, using a Tappi standard square type hand machine, JIS P
According to 8222: 1998, handmade paper was prepared and evaluated. However, only in Comparative Example 5, the addition rate of the silica filler was 4%.
And

The newsprint produced in the examples and comparative examples
After adjusting the humidity under the conditions of ℃ and 50% RH, measure the following items,
The results are shown in Table 3. -Basis weight: Measured according to JIS P 8124. -Thickness and density: Measured according to JIS P 8118. Whiteness: Measured according to JIS P 8123. -Opacity: Measured according to JIS P 8138. -Tensile strength: Measured according to JIS P 8113.

[0035]

[Table 2]

[0036]

[Table 3] As shown in Table 3, as compared with the newsprint of Comparative Example 1 and Comparative Example 2, when the basis weight alone is reduced by about 3 g / m ^{2 at} the same pulp blending and filler blending ratio, the opacity and strength are reduced. . In the newsprint of Comparative Examples 3 and 4 in which DIP was increased in comparison with Comparative Example 2, the strength was improved but the opacity was decreased.
Further, the strength of the newsprint of Comparative Example 5 in which a filler was added as a measure against opacity was extremely reduced. Similarly, the strength of the newsprint of Comparative Examples 6 to 8 in which a part of the pulp was replaced with GP as a measure against opacity decreased. On the other hand, in the newsprint of Examples 1 to 16 using hardwood mechanical pulp, D
Even when IP was mixed at 60% or 70%, the opacity and the strength were equal to or higher than those of the newsprint of Comparative Example 1 in which the basis weight was higher by about 3 g / m ² . Especially the APMP of Eucalyptus globulus
The newsprint papers of Examples 13 to 16 having a high compounding ratio of 1 had a high whiteness and a very high opacity.

[0037]

EFFECTS OF THE INVENTION By blending a hardwood mechanical pulp, it is possible to easily produce a newsprint having a low density and a high opacity. This makes it possible to increase the distribution of waste paper pulp, which is also environmentally friendly. Make a big contribution. Further, the bulky mechanical pulp used in the present invention has the same whiteness as the chemical pulp and has a high yield, and therefore contributes to the promotion of the use of the mechanical pulp as a substitute for the chemical pulp.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takuya Yamashita             5-21-1 Oji, Kita-ku, Tokyo Nippon Paper Industries             Technical Research Institute Co., Ltd. (72) Inventor Yuu Onodera             5-21-1 Oji, Kita-ku, Tokyo Nippon Paper Industries             Technical Research Institute Co., Ltd. (72) Inventor Takanori Miyanishi             5-21-1 Oji, Kita-ku, Tokyo Nippon Paper Industries             Technical Research Institute Co., Ltd. F term (reference) 4L055 AA02 AA03 AC03 AC04 AC06                       AC09 AG18 AH01 BA14 BA28                       BA29 BA34 EA04 EA08 EA15                       EA18 FA12 FA15 FA16 GA16

Claims (8)

[Claims] 1. Newsprint containing hardwood mechanical pulp. 2. Hardwood wood chips are sodium hydroxide,
2. The newsprint paper according to claim 1, which contains a hardwood mechanical pulp produced by impregnating an alkaline hydrogen peroxide aqueous solution containing sodium silicate, hydrogen peroxide, and a chelating agent, and then performing a normal pressure or pressure refining treatment. 3. Hardwood wood chips are sodium hydroxide,
A hardwood produced by impregnating it with an alkaline hydrogen peroxide aqueous solution containing sodium silicate, hydrogen peroxide, and a chelating agent, and then subjecting it to atmospheric pressure or pressure refining treatment, and then holding it with a chemical solution at room temperature or under heating. The newsprint according to any one of claims 1 and 2, which contains mechanical pulp. 4. A cell wall thickness having a Runkel ratio of 4.0 or more,
Capacity weight is 450 kg / m ^ThreeManufactured from the above hardwood
4. A hardwood mechanical pulp containing
Newspaper described in. 5. The newsprint according to any one of claims 1 to 4, wherein the content of the hardwood mechanical pulp is 5 to 95% by weight. 6. The content of hardwood mechanical pulp is 5 to 60% by weight, and the content of deinking pulp is 40 to 95% by weight, according to any one of claims 1 to 5. Newspaper. 7. A basis weight of 35 to 50 g / m ² , whiteness of 53% or more,
The newsprint according to claim 1, which has an opacity of 90% or more and a density of 0.6 g / cm ³ or less. 8. The density of the handmade paper is 0.45 g / cm ³ or less when the handmade paper is made from pulp prepared to have a Canadian standard freeness of 100 ml according to JIS P 8222: 1998. Newsprint containing hardwood mechanical pulp.