JP2013147769A - White paperboard - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a white paperboard that has reduced white unevenness on its surface and has improved surface texture on its surface, in a paperboard, specifically a white paperboard which uses recycled pulp not deinked in a middle layer thereof.SOLUTION: There is provided a white paperboard that contains 3-30 mass% of talc containing 5-50 mass% of chlorite in surface layers of a multi-layered cardboard that has used paper blended therein and at least two or more layers, and preferably further contains at least one kind of an acrylamide-acrylonitrile-acrylic acid terpolymer and an acrylamide-itaconic acid copolymer in the surface layers.

Description

The present invention relates to a paperboard, particularly a white paperboard using a waste paper pulp not deinked in the middle layer, and relates to a white paperboard having a white paper appearance in which white unevenness is not noticeable.

White paperboard is usually a cardboard having a multilayer structure of 2 to 9 layers, and is often used in various packaging boxes. Waste paper pulp is often used from the viewpoint of environmental factors and cost reduction of packaging materials, and waste paper pulp that is not deinked is used for the middle layer. For example, virgin pulp or deinked pulp with high whiteness is used for the surface layer, and waste paper pulp with low whiteness is used for the middle layer or the back layer. In order to conceal the color of the middle layer, the surface layer needs to have a certain thickness, but there is a problem of cost.

For the purpose of concealing an intermediate layer with low whiteness, a method of embedding a white pigment on the surface layer has been proposed (see Patent Documents 1 and 2). Examples of white pigments include clay, clay, calcined clay, titanium oxide, and calcium carbonate. However, the method of engraving these pigments tends to reduce the strength of the obtained paperboard, and the surface of the paperboard breaks when the paperboard is made into a box in the post-processing box making process. The amount of pigment added is limited to a small amount, which is not sufficient for concealment purposes.

JP-A-51-40412 JP-A-6-41896

The present invention provides a white paperboard, in particular, a white paperboard using a waste paper pulp which is not deinked in the middle layer, and the whiteness of the surface is reduced and the surface texture is improved.

The present invention is characterized in that, in a multilayered paperboard of at least two layers or more mixed with waste paper, 3 to 30% by mass of talc containing 5 to 50% by mass of chlorite is contained in the surface layer. Further, the surface layer preferably contains at least one of an acrylamide-acrylonitrile-acrylic acid terpolymer and an acrylamide-itaconic acid copolymer.

According to the present invention, in the white paperboard using waste paper pulp not deinked in the middle layer, there is little surface white unevenness, there is no problem of ruled line cracking in the boxing process in the post-processing process, and the surface texture is improved. White paperboard can be provided.

In the present invention, chlorite-containing talc is contained in the surface layer of the multilayer paperboard having two or more layers.
Talc is oblique, hydrous silicate mineral of magnesium forms a layered crystal structure of monoclinic system represented by the composition formula _{3MgO · 4SiO 2 · H 2 O} . Whiteness improves by containing talc in the surface layer. Further, since talc is a flat pigment and has the property of reducing frictional resistance, when it is used for the surface layer, the frictional resistance of white paperboard can be reduced and dirt is less likely to adhere.

On the other hand, chlorite is a mineral containing aluminum represented by the composition formula Al ₂ O ₃ · 5MgO · 3SiO ₂ · 4H ₂ O. Compared with talc, its hydrophilicity is high and its dispersibility in water is good.
Chlorite is one in which Mg (magnesium) of talc is partially replaced by Al (aluminum), and one that already contains a certain proportion of chlorite at the time of talc production is preferably used in the present invention.

When chlorite-containing talc is used for the surface layer, in addition to the effect of improving whiteness and reducing frictional resistance, there is an advantage that the problem of ruled line cracking in the box making process is less likely to occur. This is probably because chlorite is relatively hydrophilic and dispersible in water, so that it is uniformly dispersed in the surface layer without agglomeration, and the resulting white paperboard has a high tensile strength.

In the present invention, when the chlorite-containing talc is less than 5% by mass, the dispersion in the pulp becomes poor, and the strength of the obtained white paperboard may be insufficient, which may cause a problem of ruled line cracking. When chlorite exceeds 50% by mass, the effect of reducing the frictional resistance of the obtained white paperboard is insufficient and not only dirt is likely to adhere, but also chlorite has a Mohs hardness of 1 compared to 2 Since it is -3, it may have an influence on the abrasion degree of the cutter blade at the time of punching.

Talc containing 5% by mass to 50% by mass of the chlorite of the present invention is contained in the surface layer in an amount of 3-30% by mass. The total amount of chlorite may be in the range of 5% by mass to 50% by mass. It is also possible to mix two or more kinds of talc within the above range. If the talc is less than 3% by mass, the whiteness improvement effect may be insufficient. If the talc exceeds 30% by mass, the whiteness improvement effect cannot be expected any more. There is concern about the wear of the cutter blade.

The chlorite-containing talc of the present invention preferably has an average particle size in the range of 0.5 to 30 μm. When the average particle size is less than 0.5 μm, the wettability to water is lowered and the dispersibility in water may be insufficient. If the average particle size exceeds 30 μm, the surface smoothness of the resulting product may be inferior. The average particle size defined in the present invention is measured by a sedimentation method (Cedigraph), and the particle size at which the cumulative mass is 50% is defined as the average particle size.

The white paperboard of the present invention is a multilayer paperboard having at least two layers. The basis weight of the surface layer is in the range of 5 to 80 g / ^{m 2} is preferred. When the basis weight of the surface layer is less than 5 g / m ² , whiteness and hiding properties may be insufficient. In addition, since the sheet becomes extremely thin, serious troubles such as running out of paper are likely to occur during operation. When the basis weight of the surface layer exceeds 80 g / m ² , the concealment effect is increased, but the drying load of the first layer pulp sheet is extremely increased at the time of paper making, resulting in a decrease in paper making speed or an increase in cost due to the use of much pulp. This is not preferable.

In the present invention, virgin pulp or deinked high-whiteness pulp is used alone or mixed in the surface layer of two or more paperboards, and the back layer (including the middle layer in the case of three or more layers) is not deinked. Used waste paper pulp. Note that both surfaces may be surface layers in the case of three or more layers.
In order to obtain 70% of the product whiteness on the surface layer side, the whiteness of the surface layer itself needs to be 80% or more.
Furthermore, in order to obtain uniform whiteness with no unevenness, it is known to add a filler to the surface layer in addition to pulp to make it uniform, but it is most preferable to add chlorite-containing talc.
And, other than waste paper pulp, for example, bleached or unbleached chemical pulp, one kind of mechanical pulp, or two or more kinds are mixed appropriately and used according to the intended strength and whiteness of each layer Good. In addition, the white paperboard of the present invention may appropriately contain a sizing agent, a paper strength agent, a chemical stabilizer, a filtering agent, a filler, a dye and the like as necessary.

In particular, the surface layer preferably contains at least one of acrylamide-acrylonitrile-acrylic acid terpolymer and acrylamide-itaconic acid copolymer as a paper strength agent. These paper strength agents have the effect of further improving the dispersibility of the chlorite-containing talc of the present invention, and among them, an arylylamide-acrylonitrile-acrylic acid terpolymer is preferable. As a commercially available product, Polystron (manufactured by Arakawa Chemical Co., Ltd.) can be used. The content is preferably 0.5% by mass to 2.0% by mass in the surface layer.

A known method can be used for making the white paperboard of the present invention. For example, a papermaking raw material for waste paper pulp and white water are mixed and beaten with a refiner or the like to dissolve the pulp. The obtained pulp slurry is sequentially sent to a mixing chest and a machine chest, and then sent to a seed box. The pulp slurry is then fed through a screen to a paper machine. For pulp slurry, various anionic, nonionic, cationic or amphoteric drainage improvers, internal sizing agents, dyes, fluorescent brighteners, pH adjusters, antifoaming agents, pitch control agents as required Further, an internal additive for papermaking such as a slime control agent can be added as appropriate. The white paperboard of the present invention has a multilayer structure of two or more layers, and is not limited as long as it is a paper machine capable of making a multi-layer paper. A long net paper machine, a short net paper machine, a circular net paper machine, an on-top paper machine. Paper machines such as mer and gap former can be used.

Further, in the present invention, a roll size press coater, a gate roll coater, a pre-metering size press coater, a shim sizer, natural adhesive such as starch, polyvinyl alcohol, polyallylamide, styrene-butadiene copolymer resin, In order to use a synthetic adhesive such as an acrylic resin and impart printability, it is possible to provide a coating layer mainly composed of a pigment and an adhesive.

The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples. In the following examples and comparative examples, “parts” and “%” indicate solid parts by mass and solids mass%, respectively.

<Example 1>
A paper stock was prepared with the composition shown below, paper-made, paper-combined, pressed, and dried to obtain white paperboard.
Surface layer (first layer)
US tsubo 50.0 g / m ²
Waste paper pulp 100% (uses Kent waste paper and cut waste paper mixed and bleached to 80% whiteness)
Freeness 260mL
Chlorite-containing talc (trade name: NK-KCL, Kanematsu Chemical, containing 30% by mass of chlorite, particle size 7 μm) 15%
Polyacrylamide resin 0.8%
Aluminum sulfate 3.5%
Acrylamide-acrylonitrile-acrylic acid terpolymer resin 3.2%

Lower layer (second layer)
US tsubo 50.0 g / m ²
100% waste paper pulp (uses a mixture of magazine waste paper and PP waste paper)
Freeness 400mL
Polyacrylamide resin 0.16%
Aluminum sulfate 2.2%
Acrylamide-acrylonitrile-acrylic acid terpolymer resin 1.8%

Middle layer (3-6th layer)
US tsubo 150.0 g / m ²
100% waste paper pulp (uses 42% white magazine paper)
Freeness 400mL
Polyacrylamide resin 0.8%
Aluminum sulfate 0.27%

Back layer (7th layer)
US tsubo 50.0 g / m ²
100% waste paper pulp (uses 42% white magazine paper)
Freeness 250mL
0.25% polyacrylamide resin
Aluminum sulfate 1.5%
Acrylamide-acrylonitrile-acrylic acid terpolymer resin 0.55%

Example 2
A white paperboard was obtained according to Example 1 except that the chlorite-containing talc in the surface layer was 3%.

Example 3
A white paperboard was obtained according to Example 1 except that the chlorite-containing talc in the surface layer was changed to 30%.

Example 4
A white paperboard was obtained according to Example 1 except that talc containing 5% by mass of chlorite was used as the chlorite-containing talc of the surface layer.

Example 5
A white paperboard was obtained according to Example 1 except that the chlorite-containing talc of the surface layer was changed to talc containing 50% by mass of chlorite (blended below).
Product name: NK-KCL (Kanematsu Chemical, containing 30% by mass of chlorite, particle size 7 μm) 67%
Product name: NK-KW (Kanematsu Chemical, containing 90% by mass of chlorite, particle size 6 μm) 33%

Example 6
A white paperboard was obtained according to Example 1 except that talc containing 3% by mass of chlorite was used as the chlorite-containing talc of the surface layer.

Comparative Example 1
A white paperboard was obtained according to Example 1 except that the chlorite-containing talc in the surface layer was changed to talc containing 60% by mass of chlorite (blended below).
Product name: NK-KCL (Kanematsu Chemical, containing 30% by mass of chlorite, particle size 7 μm) 50%
Product name: NK-KW (Kanematsu Chemical, containing 90% by mass of chlorite, particle size 6 μm) 50%

Comparative Example 2
A white paperboard was obtained according to Example 1 except that the chlorite-containing talc in the surface layer was 1% by mass.

Comparative Example 3
White paperboard was obtained according to Example 1 except that the chlorite-containing talc in the surface layer was 40% by mass.

Comparative Example 4
A white paperboard was obtained according to Example 1 except that kaolinite clay was used instead of chlorite-containing talc for the surface layer.

The obtained white paperboard was evaluated as follows, and the obtained results are summarized in Table 1. The measurement and evaluation of the white paperboard in the present invention were performed in an environment of 23 ° C. and 50% RH unless otherwise specified.

-Dispersibility The surface layer stock is visually confirmed to evaluate the cohesiveness of the pigment. A: There is no aggregation of the pigment and the pigment is uniformly dispersed.
○: A little aggregation of the pigment is observed, but there is no practical problem.
X: There are many aggregations of the pigment and there are practical problems.

-Whiteness The whiteness of the obtained white paperboard (surface layer side) was adjusted for 6 hours under the conditions based on JIS P8111 and then a spectral whiteness colorimeter (Suga test) according to JIS P-8148: 2001. (Manufactured by Kikai Co., Ltd.).

・ Evaluation of frictional property on the surface (surface side) ◎: Friction is sufficiently low and dirt is hardly adhered.
○: Good with low friction.
X: There is a problem in practical use because of high friction and easy adhesion of dirt.

・ Surface layers of white paperboard made of paper dust were rubbed together to evaluate the amount of the detached pigment ○: No pigment was detached.
X: Desorption of the pigment is often observed and there is a practical problem.

-Abrasion degree of punching blade The wear degree of the female mold was visually observed when 50,000 shots were punched by a flat punching machine (Iijima Seisakusho automatic flat plate punching machine JF660).
×: Necessary to replace △: No need to replace but worn considerably

Claims (2)

A white paperboard comprising 3 to 30% by mass of talc containing 5 to 50% by mass of chlorite in a surface layer of a multi-layered paperboard having at least two layers mixed with waste paper. 2. The white paperboard according to claim 1, wherein the surface layer contains at least one of an acrylamide-acrylonitrile-acrylic acid terpolymer and an acrylamide-itaconic acid copolymer.