JPH11323755A - White paperboard - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a white paperboard capable of eliminating printing trouble due to back fuzz and excellent in printability. SOLUTION: This white paperboard comprises three or more layers of a skin, a medial and a back layers. In the white paperboard, the skin layer has a pigment coating layer and the back layer is a layer consisting essentially of a waste paper pulp. The white paperboard is obtained by disintegrating the waste paper, removing dust from the waste paper, then carrying out a kneading treatment, subsequently conducting an alkali soaking treatment and, as necessary, further performing a flotation treatment. Thereby, the pulp water retention value of the back layer is >=135% and the aggregated ash content is <=5 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a white paperboard used for packaging boxes and the like. More specifically, it relates to white paperboard having excellent printability.

[0002]

2. Description of the Related Art White paperboard is widely used as a packaging box for articles such as a detergent box, a tissue paper box, a photographic film box, and a commercially available medicine box. It is also used for applications other than packaging, such as book covers and picture books.

[0003] White paperboard is generally composed of at least three layers of a surface layer, a middle layer and a back layer. For the middle layer, non-deinked waste paper pulp is used. Used. The back layer differs depending on the application. When white is required on both surfaces, the back layer is the same as the surface layer. When white is not required, waste paper pulp having low whiteness is used.

In order to conceal the color of the middle layer, the surface layer needs to have a concealing property and needs a certain thickness. But,
If concealment is required only for the surface layer, it will be costly.
A lower surface layer having a certain degree of whiteness is often provided between the middle layer and the surface layer. When a more beautiful appearance is required, a paint using a pigment having high whiteness is applied to the surface of the surface layer as in the case of a general coated paper for printing.

[0005]

Problems to be Solved by the Invention White paperboard is stored and transported in a roll or sheet until it is applied to a printing machine after papermaking and coating, but the coated surface of the surface layer and the back layer are under load. The surface of the back layer may be partially transferred to the surface-coated surface when peeled off. In particular, the cohesive ash generated from the coated paper waste paper lowers the surface strength of the paper and is likely to be transferred. This phenomenon is referred to as "back
Called. When "back fluff" occurs, a problem occurs in that printing is impaired by impurities attached to the surface when printing is performed. SUMMARY OF THE INVENTION It is an object of the present invention to eliminate a printing trouble caused by "back fringing".

[0006]

Means for Solving the Problems In order to solve the above problems, the present invention employs the following configurations. That is, the present invention, the surface layer,
A white paperboard consisting of three or more layers of a middle layer and a back layer. The surface layer has a pigment coating layer on the surface layer. The back layer is a layer mainly composed of waste paper pulp. After that, alkali soaking is performed, and if necessary, further flotation treatment is performed to reduce the pulp water retention of the back layer to 1
A white paperboard characterized by having an agglomerated ash content of not less than 35% and not more than 5%.

[0007] According to the study of the present inventors, the back fluff is generated depending on the kind and lot of used waste paper of the back layer.
As means for solving the back fluff, a method by changing the physical properties of a binder of a paint applied to the surface layer, addition of an additive, and the like, and a method by examining a substance to be applied to the back surface can be considered. However, the back fluff is essentially due to variations in the quality of the raw material, and it is desirable to take fundamental measures on the raw material. However, it is difficult to limit the used paper from the viewpoint of the recent expansion of resource recovery and reuse.

On the other hand, in order to remove the cohesive ash derived from the coating layer which is not fragmented by the disintegration process and exists as an aggregate in the pulp, the raw material waste paper is disintegrated, kneaded, and further classified. As a result, the present applicant has made a proposal for countermeasures against back fluff. Although this method exhibits an excellent effect, the fine fibers are slightly lost due to the classification treatment,
The freeness of the raw pulp of the middle layer using it decreases,
In some cases, the operating conditions were limited by the suitability for papermaking and dehydration.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted research from such a viewpoint, and as a result, by specifying the pulp water retention in the raw material of the back layer, the back fluff can be removed even if the agglomerated ash content is large. They have found that they can be suppressed and arrived at the present invention.

The white paperboard to be used in the present invention comprises at least three layers: a surface layer, a middle layer, and a back layer. In many cases, a lower surface layer is provided between the surface layer and the middle layer. The lower layer pulp is a layer whose whiteness is lower than that of the surface layer and whose main purpose is to mask the coloring of the middle layer. Each layer may be composed of two or more layers, and in most cases, a total of 5 to 9 layers is formed.

[0011] The surface layer is the outermost layer of papermaking, and uses pulp with high whiteness to completely hide the effect of the colored pulp in the middle layer. The pulp used for the surface layer is bleached pulp, the raw wood may be either hardwood or conifer, and the pulping method may be either chemical pulp or mechanical pulp. Also,
Deinked waste paper pulp can also be used, and these may be mixed and blended.

For the middle layer, used newspaper, used magazine, used corrugated cardboard, used miscellaneous paper, etc. are used only for the disintegration process. The back layer is generally the same as the middle layer, but deinked waste paper pulp may be used. In special cases, pulp similar to the surface layer may be used for the back layer to provide cosmetics on both sides, but in this case, both sides should be recognized as the surface layer. The present invention is directed to a case where disintegrated waste paper pulp and / or deinked waste paper pulp is used for the back layer.

The present invention is directed to a white paperboard provided with a pigmented layer on the surface of a surface layer. The pigment coating is performed with the same paint as that used for general printing coated paper. The paint is composed of kaolin, calcium carbonate, plastic pigment, pigment such as titanium dioxide, SBR latex, starch, binder such as polyvinyl alcohol, and the like.
The coating method can also be performed by a known coating machine, and two or more pigment coating layers may be formed.

The back layer defined in the claims of the present invention refers to the outermost layer on the side opposite to the surface coated surface. The measurement of pulp water retention was carried out according to the method described in the section of Examples. The method for measuring the aggregated ash content is also the same as the method described in the section of Examples. In the present invention, the pulp water retention of the back layer must be 135% or more, and the cohesive ash content in the back layer must be 5% or less. When the degree of water retention is less than this range, the frequency of occurrence of back fluffing increases.

In the present invention, as a method for controlling the pulp water retention and the coagulated ash content of the back layer to specified values, in addition to the usual pulverized pulp production processing (defibration and dust removal), the method used in the pulp production process can be used. Kneading with a concentration dispersing machine (dispersion kneading), followed by alkali soaking (aging), and blending as deinked pulp through flotation, washing, and dewatering steps as necessary Achieved by The water retention can also be increased by reducing the pulp freeness using a refining machine such as a refiner, but this method is not preferable because it increases the number of fine fibers at the same time.

The high-concentration dispersers can be classified into a single-shaft type, a twin-shaft type, and a disk type when structurally classified. Power load of kneading process is 2.5Kwh / pulp AD
(Air drying) t or more is preferable. By doing so, the swellability of the pulp fiber is increased, and it is easy to secure the water retention.
The pulp concentration at the time of kneading is preferably set as high as the performance of the apparatus allows. Usually, it is in the range of 25 to 35% by weight. The temperature is maintained at 50 ° C. or higher without particular heating due to frictional heat.

In the production of ordinary deinked pulp, alkali, hydrogen peroxide, sodium silicate and a deinking agent are added at the same time during ripening, and soaking is performed. In the case of the present invention,
The addition of hydrogen peroxide and sodium silicate may or may not be performed. As the alkali, for example, caustic soda is added in an amount of 0.2 to 0.5% by weight with respect to waste paper pulp, and alkali soaking (aging) is performed at 50 ° C. or more for 80 minutes or more.
Thereafter, the pulp for the back layer may be obtained through a flotation / washing / dehydration step as necessary. When performing flotation, there is no particular limitation except that a deinking agent is added together with caustic soda at 0.05 to 0.1% by weight to waste paper pulp during soaking, but the pulp concentration during flotation is 0.1%. The range of 7 to 1.0% by weight is preferred.

[0018]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto. The numerical values such as the addition ratio are numerical values based on the weight of the solid component or the active ingredient.

<Measurement Method of Pulp Water Retention> A slurry pulp serving as a sample was sampled at about 0.5 g in absolute dry weight,
The mixture is naturally filtered through a centrifuge tube for a centrifuge, which is previously equipped with a wire mesh. Second, suction filtration is performed while pouring the squeezed liquid obtained in the first step into a centrifuge tube. Third, centrifugal filtration is performed at 4200 rpm for 15 minutes using a centrifugal separator, and the wet weight of the sample at this time is determined. Finally, the sample is dried at 105 ° C. for 10 hours or more to determine the absolute dry weight. As the water retention, the difference between the wet weight of the sample after centrifugal filtration and the absolute dry weight is defined as the retained moisture of the sample, and the weight percentage of the moisture retained in the sample relative to the absolute dry weight is expressed as the water retention (%). (J. Tappi No. 26
According to. )

<Measurement method of agglomerated ash content> A slurry-like pulp serving as a sample is passed through a sieve having openings of 300 mesh,
Wash while diluting with 15 l of tap water. Next, after measuring the absolute dry weight of the residue remaining on the sieve, it is baked in an electric furnace at a furnace temperature of 500 ° C., and the weight of the ash is determined. As the coagulated ash content, the weight% of the ash with respect to the above-mentioned residual dry weight is expressed as coagulated ash content (%).

<Examples 1 and 2, Comparative Examples 1 and 2> As a back layer raw material, used magazine waste paper was subjected to a normal disintegration pulp production treatment (disintegration
Dust removal). The water retention of this disintegrated pulp is 126%,
The cohesive ash content was 6.2%. This was used as a back layer pulp to make Comparative Example 1. Classification after kneading (150
The pulp concentration was increased to 10% with a mesh sieve) to obtain Comparative Example 2.

This disintegrated pulp is further kneaded (disperser treatment, power load 2.8 Kwh / pulp ADt).
In addition, alkali soaking treatment (caustic soda vs. pulp 0.3%, 60 ° C., 80 minutes), and further flotation treatment (ink removing agent vs. pulp 0.1%, pulp concentration 1.0%) Was performed to obtain a pulp slurry having the physical properties shown in Table 1. This was prepared white board total rice basis 340 g / m ² was papermaking as lining of Beitsubo 40 g / m ^2. The structure of each layer in common is: Surface layer: LBKP / NB
^{KP = 75 / 25,30g / m 2} ; 1 layer, Table lower: 100% magazine paper deinked pulp, 30g / m ^2; 1 layer, middle layer:
Magazine pulp 100%, 60 g / m ² ; 4 layers, 1 layer of backing layer. These are Examples 1 and 2. On each surface layer, a pigment coating layer was provided with a coating material having the following formulation so as to have a dry weight of 19 g / m ² .

<Coating of paint> Top coat: kaolin (Kao Fine-90) / calcium carbonate (Brilliant-15) / titanium dioxide (Kronos KA-10) = 55/35/10 (parts), latex 20 parts, starch 6 Department. Undercoat: kaolin (alpha gloss) / calcium carbonate (SL-2200) / calcium carbonate (Tamapearl 12)
1MC) = 15/55/30 (parts) and latex 1
4 parts, starch 6 parts.

The back fluff of each white paperboard was evaluated as follows. <Method for evaluating back fluff> RI method: The back side of white paperboard as a sample is printed on an RI printing machine (100
(Rotation). After printing, the number of fibers taken on the blanket was copied to a transfer paper, and the degree of fiber taken was evaluated visually by dividing it into five stages. The higher the value, the less fiber is removed and the better. Hot pressing method: The front and back sides of white paperboard are overlapped,
After adjusting the humidity in an environment of 60 ° C and 85% RH, hot press 8
Pressurization (30 kg / cm ² ) is performed at 0 ° C. for 20 minutes. This is peeled off, and at this time, the number of binding fibers of the back layer taken on the surface of the white paperboard, the number of coat lees, the number of clumps of pigment, and the like are measured by an image analyzer.

[0025]

[Table 1]

According to the results shown in Table 1, the back pulp according to the present invention (Examples 1 and 2) showed significantly improved back fluff evaluation as compared with Comparative Example 1 in which only the defibration and dust removal treatment was performed. Further, in Examples 1 and 2, Comparative Example 2 in which a classification process was further performed after the kneading process was performed.
On the other hand, the aggregated ash content was slightly large, but the back fluff evaluation was equal to or higher than that. It is clear that the present invention is excellent also in that the outflow of fine fibers is suppressed and a high back fluff evaluation is obtained.

<Examples 3 to 5, Comparative Example 3> As a back layer raw material, a used paper for magazines was subjected to a usual defibration pulp production treatment (defibration and dust removal). The water retentivity of this disintegrated pulp was 131%, and the cohesive ash content was 5.9%. This was used as a back layer pulp to make Comparative Example 3. The disintegrated pulp is treated under the conditions shown in Table 2 (kneading treatment / soaking with alkali addition), followed by flotation (adding 0.1% of deinking agent to pulp, pulp concentration of 1.0%), and pulp for the back layer (implement Examples 3 and 4) were obtained. During soaking, hydrogen peroxide (3.5% with respect to pulp) and sodium silicate (5%) were added together with caustic soda and a deinking agent.
%) Was added, and then normal DIP obtained by flotation was blended at the ratio shown in Table 2 to obtain Example 5. Thereafter, the same white paperboard as in Example 1 was obtained.

[0028]

[Table 2] * Pc in Table 2 indicates the absolute dry weight ratio of pulp to the raw material slurry weight.

[0029]

According to the present invention, there is no need to change the pigment coating layer or the coating material on the back surface, and the back fluff can be stably prevented even if the cohesive ash content is high. In particular, in Comparative Example 2, fine fibers and agglomerated ash that had passed through the sieve were passed to the middle layer as a measure against runoff, and as a result, coarse raw materials had to be specially added in order to maintain the paper layer formability.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Eiji Okayama Inventor 872-1 Eno-michi, Onaka-shi, Oita-shi, Oita Oji Paper Co., Ltd. Oita Mill

Claims (1)

[Claims] 1. A white paperboard comprising three or more layers of a surface layer, an intermediate layer, and a back layer, wherein the surface layer has a pigment coating layer, the back layer is a layer mainly composed of waste paper pulp, and the waste paper is disintegrated. -After dust removal, kneading treatment, alkali soaking, and further flotation treatment as necessary, the pulp water retention of the back layer is 135% or more, and the cohesive ash content is 5% by weight or less. White paperboard.